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Artykuły w czasopismach na temat "Glycan Removal"
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Liang, Yu, Miklos Guttman, James A. Williams, Hans Verkerke, Daniel Alvarado, Shiu-Lok Hu i Kelly K. Lee. "Changes in Structure and Antigenicity of HIV-1 Env Trimers Resulting from Removal of a Conserved CD4 Binding Site-Proximal Glycan". Journal of Virology 90, nr 20 (3.08.2016): 9224–36. http://dx.doi.org/10.1128/jvi.01116-16.
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ABSTRACTThe envelope glycoprotein (Env) is the major target for HIV-1 broadly neutralizing antibodies (bNAbs). One of the mechanisms that HIV has evolved to escape the host's immune response is to mask conserved epitopes on Env with dense glycosylation. Previous studies have shown that the removal of a particular conserved glycan at N197 increases the neutralization sensitivity of the virus to antibodies targeting the CD4 binding site (CD4bs), making it a site of significant interest from the perspective of vaccine design. At present, the structural consequences that result from the removal of the N197 glycan have not been characterized. Using native-like SOSIP trimers, we examine the effects on antigenicity and local structural dynamics resulting from the removal of this glycan. A large increase in the binding of CD4bs and V3-targeting antibodies is observed for the N197Q mutant in trimeric Env, while no changes are observed with monomeric gp120. While the overall structure and thermostability are not altered, a subtle increase in the flexibility of the variable loops at the trimeric interface of adjacent protomers is evident in the N197Q mutant by hydrogen-deuterium exchange mass spectrometry. Structural modeling of the glycan chains suggests that the spatial occupancy of the N197 glycan leads to steric clashes with CD4bs antibodies in the Env trimer but not monomeric gp120. Our results indicate that the removal of the N197 glycan enhances the exposure of relevant bNAb epitopes on Env with a minimal impact on the overall trimeric structure. These findings present a simple modification for enhancing trimeric Env immunogens in vaccines.IMPORTANCEThe HIV-1 Env glycoprotein presents a dense patchwork of host cell-derived N-linked glycans. This so-called glycan shield is considered to be a major protective mechanism against immune recognition. While the positions of many N-linked glycans are isolate specific, some are highly conserved and are believed to play key functional roles. In this study, we examine the conserved, CD4 binding site-proximal N197 glycan and demonstrate that its removal both facilitates neutralizing antibody access to the CD4 binding site and modestly impacts the structural dynamics at the trimer crown without drastically altering global Env trimer stability. This indicates that surgical glycosylation site modification may be an effective way of sculpting epitope presentation in Env-based vaccines.
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CHITLARU, Theodor, Chanoch KRONMAN, Baruch VELAN i Avigdor SHAFFERMAN. "Overloading and removal of N-glycosylation targets on human acetylcholinesterase: effects on glycan composition and circulatory residence time". Biochemical Journal 363, nr 3 (24.04.2002): 619–31. http://dx.doi.org/10.1042/bj3630619.
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Optimization of post-translational modifications was shown to affect the ability of recombinant human acetylcholinesterase (rHuAChE) produced in HEK-293 cells to be retained in the circulation for prolonged periods of time [Kronman, Velan, Marcus, Ordentlich, Reuveny and Shafferman (1995) Biochem. J. 311, 959–967; Chitlaru, Kronman, Zeevi, Kam, Harel, Ordentlich, Velan and Shafferman (1998) Biochem. J. 336, 647–658; Chitlaru, Kronman, Velan and Shafferman (2001) Biochem. J. 354, 613–625]. To evaluate the possible contribution of the number of appended N-glycans in determining the pharmacokinetic behaviour of AChE, a series of sixteen recombinant human AChE glycoforms, differing in their number of appended N-glycans (2, 3, 4 or 5 glycans), state of assembly (dimeric or tetrameric) and terminal glycan sialylation (partially or fully sialylated) were generated. Extensive structural analysis of N-glycans demonstrated that the various glycan types associated with all the different rHuAChE glycoforms are essentially similar both in structure and abundance, and that production of the various glycoforms in the sialyltransferase-overexpressing 293ST-2D6 cell line resulted in the generation of enzyme species that carry glycans sialylated to the same extent. Pharmacokinetic profiling of the rHuAChE glycoforms in their fully tetramerized and sialylated state clearly demonstrated that circulatory longevity correlated directly with the number of attached N-glycans (mean residence times for rHuAChE glycoforms harbouring 2, 3, and 4 glycans = 200, 740, and 1055min respectively). This study provides evidence that glycan loading, together with N-glycan terminal processing and enzyme subunit oligomerization, operate in a hierarchical and concerted manner in determining the pharmacokinetic characteristics of AChE.
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Binley, James M., Yih-En Andrew Ban, Emma T. Crooks, Dirk Eggink, Keiko Osawa, William R. Schief i Rogier W. Sanders. "Role of Complex Carbohydrates in Human Immunodeficiency Virus Type 1 Infection and Resistance to Antibody Neutralization". Journal of Virology 84, nr 11 (24.03.2010): 5637–55. http://dx.doi.org/10.1128/jvi.00105-10.
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ABSTRACT Complex N-glycans flank the receptor binding sites of the outer domain of HIV-1 gp120, ostensibly forming a protective “fence” against antibodies. Here, we investigated the effects of rebuilding this fence with smaller glycoforms by expressing HIV-1 pseudovirions from a primary isolate in a human cell line lacking N-acetylglucosamine transferase I (GnTI), the enzyme that initiates the conversion of oligomannose N-glycans into complex N-glycans. Thus, complex glycans, including those that surround the receptor binding sites, are replaced by fully trimmed oligomannose stumps. Conversely, the untrimmed oligomannoses of the silent domain of gp120 are likely to remain unchanged. For comparison, we produced a mutant virus lacking a complex N-glycan of the V3 loop (N301Q). Both variants exhibited increased sensitivities to V3 loop-specific monoclonal antibodies (MAbs) and soluble CD4. The N301Q virus was also sensitive to “nonneutralizing” MAbs targeting the primary and secondary receptor binding sites. Endoglycosidase H treatment resulted in the removal of outer domain glycans from the GnTI- but not the parent Env trimers, and this was associated with a rapid and complete loss in infectivity. Nevertheless, the glycan-depleted trimers could still bind to soluble receptor and coreceptor analogs, suggesting a block in post-receptor binding conformational changes necessary for fusion. Collectively, our data show that the antennae of complex N-glycans serve to protect the V3 loop and CD4 binding site, while N-glycan stems regulate native trimer conformation, such that their removal can lead to global changes in neutralization sensitivity and, in extreme cases, an inability to complete the conformational rearrangements necessary for infection.
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Vyas, Heema K. N., Anuk D. Indraratna, Arun Everest-Dass, Nicolle H. Packer, David M. P. De Oliveira, Marie Ranson, Jason D. McArthur i Martina L. Sanderson-Smith. "Assessing the Role of Pharyngeal Cell Surface Glycans in Group A Streptococcus Biofilm Formation". Antibiotics 9, nr 11 (4.11.2020): 775. http://dx.doi.org/10.3390/antibiotics9110775.
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Group A Streptococcus (GAS) causes 700 million infections and accounts for half a million deaths per year. Antibiotic treatment failure rates of 20–40% have been observed. The role host cell glycans play in GAS biofilm formation in the context of GAS pharyngitis and subsequent antibiotic treatment failure has not been previously investigated. GAS serotype M12 GAS biofilms were assessed for biofilm formation on Detroit 562 pharyngeal cell monolayers following enzymatic removal of all N-linked glycans from pharyngeal cells with PNGase F. Removal of N-linked glycans resulted in an increase in biofilm biomass compared to untreated controls. Further investigation into the removal of terminal mannose and sialic acid residues with α1-6 mannosidase and the broad specificity sialidase (Sialidase A) also found that biofilm biomass increased significantly when compared to untreated controls. Increases in biofilm biomass were associated with increased production of extracellular polymeric substances (EPS). Furthermore, it was found that M12 GAS biofilms grown on untreated pharyngeal monolayers exhibited a 2500-fold increase in penicillin tolerance compared to planktonic GAS. Pre-treatment of monolayers with exoglycosidases resulted in a further doubling of penicillin tolerance in resultant biofilms. Lastly, an additional eight GAS emm-types were assessed for biofilm formation in response to terminal mannose and sialic acid residue removal. As seen for M12, biofilm biomass on monolayers increased following removal of terminal mannose and sialic acid residues. Collectively, these data demonstrate that pharyngeal cell surface glycan structures directly impact GAS biofilm formation in a strain and glycan specific fashion.
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White, K. D., R. D. Cummings i F. J. Waxman. "Ig N-glycan orientation can influence interactions with the complement system." Journal of Immunology 158, nr 1 (1.01.1997): 426–35. http://dx.doi.org/10.4049/jimmunol.158.1.426.
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Abstract This study was prompted by the paradoxical observation that a pair of dinitrophenyl-specific murine monoclonal IgG2a Abs had similar monosaccharide content and yet differed in their binding to lectins. The differential lectin-binding properties were lost when the Abs were denatured, suggesting that variations in lectin binding reflected the conformational accessibility of the N-glycans rather than intrinsic differences in the lectin binding capacity of the glycans themselves. This hypothesis was supported by experiments indicating that the degree to which the N-glycans on the Abs were reactive with beta-1,4-galactosyltransferase or susceptible to peptide N-glycosidase F corresponded directly to their relative accessibility to lectins. Moreover, the relative susceptibility to these enzymes and accessibility to lectins was inversely related to the capacity of the Abs to activate the classical pathway, suggesting that the orientation of the more accessible N-glycan might inhibit C1q binding. This hypothesis was supported by evidence that enzymatic cleavage of the more accessible N-glycan resulted in enhanced Clq, C4b, and C3b deposition. Conversely, removal of the less accessible N-glycan expressed by the other Ab inhibited C1q, C4b, and C3b deposition. The respective increase or decrease in C3b deposition on the two deglycosylated Abs was magnified when complement activation was performed in factor B-depleted serum, suggesting that N-glycan conformation primarily affects the classical pathway. Collectively, these data suggest that the orientation of the N-glycan expressed on Igs can profoundly influence interaction with the complement system.
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Townsley, Samantha, Yun Li, Yury Kozyrev, Brad Cleveland i Shiu-Lok Hu. "Conserved Role of an N-Linked Glycan on the Surface Antigen of Human Immunodeficiency Virus Type 1 Modulating Virus Sensitivity to Broadly Neutralizing Antibodies against the Receptor and Coreceptor Binding Sites". Journal of Virology 90, nr 2 (28.10.2015): 829–41. http://dx.doi.org/10.1128/jvi.02321-15.
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ABSTRACTHIV-1 establishes persistent infection in part due to its ability to evade host immune responses. Occlusion by glycans contributes to masking conserved sites that are targets for some broadly neutralizing antibodies (bNAbs). Previous work has shown that removal of a highly conserved potential N-linked glycan (PNLG) site at amino acid residue 197 (N7) on the surface antigen gp120 of HIV-1 increases neutralization sensitivity of the mutant virus to CD4 binding site (CD4bs)-directed antibodies compared to its wild-type (WT) counterpart. However, it is not clear if the role of the N7 glycan is conserved among diverse HIV-1 isolates and if other glycans in the conserved regions of HIV-1 Env display similar functions. In this work, we examined the role of PNLGs in the conserved region of HIV-1 Env, particularly the role of the N7 glycan in a panel of HIV-1 strains representing different clades, tissue origins, coreceptor usages, and neutralization sensitivities. We demonstrate that the absence of the N7 glycan increases the sensitivity of diverse HIV-1 isolates to CD4bs- and V3 loop-directed antibodies, indicating that the N7 glycan plays a conserved role masking these conserved epitopes. However, the effect of the N7 glycan on virus sensitivity to neutralizing antibodies directed against the V2 loop epitope is isolate dependent. These findings indicate that the N7 glycan plays an important and conserved role modulating the structure, stability, or accessibility of bNAb epitopes in the CD4bs and coreceptor binding region, thus representing a potential target for the design of immunogens and therapeutics.IMPORTANCEN-linked glycans on the HIV-1 envelope protein have been postulated to contribute to viral escape from host immune responses. However, the role of specific glycans in the conserved regions of HIV-1 Env in modulating epitope recognition by broadly neutralizing antibodies has not been well defined. We show here that a single N-linked glycan plays a unique and conserved role among conserved glycans on HIV-1 gp120 in modulating the exposure or the stability of the receptor and coreceptor binding site without affecting the integrity of the Env in mediating viral infection or the ability of the mutant gp120 to bind to CD4. The observation that the antigenicity of the receptor and coreceptor binding sites can be modulated by a single glycan indicates that select glycan modification offers a potential strategy for the design of HIV-1 vaccine candidates.
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Aguilar, Hector C., Kenneth A. Matreyek, Claire Marie Filone, Sara T. Hashimi, Ernest L. Levroney, Oscar A. Negrete, Andrea Bertolotti-Ciarlet i in. "N-Glycans on Nipah Virus Fusion Protein Protect against Neutralization but Reduce Membrane Fusion and Viral Entry". Journal of Virology 80, nr 10 (15.05.2006): 4878–89. http://dx.doi.org/10.1128/jvi.80.10.4878-4889.2006.
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ABSTRACT Nipah virus (NiV) is a deadly emerging paramyxovirus. The NiV attachment (NiV-G) and fusion (NiV-F) envelope glycoproteins mediate both syncytium formation and viral entry. Specific N-glycans on paramyxovirus fusion proteins are generally required for proper conformational integrity and biological function. However, removal of individual N-glycans on NiV-F had little negative effect on processing or fusogenicity and has even resulted in slightly increased fusogenicity. Here, we report that in both syncytium formation and viral entry assays, removal of multiple N-glycans on NiV-F resulted in marked increases in fusogenicity (>5-fold) but also resulted in increased sensitivity to neutralization by NiV-F-specific antisera. The mechanism underlying the hyperfusogenicity of these NiV-F N-glycan mutants is likely due to more-robust six-helix bundle formation, as these mutants showed increased fusion kinetics and were more resistant to neutralization by a fusion-inhibitory reagent based on the C-terminal heptad repeat region of NiV-F. Finally, we demonstrate that the fusogenicities of the NiV-F N-glycan mutants were inversely correlated with the relative avidities of NiV-F's interactions with NiV-G, providing support for the attachment protein “displacement” model of paramyxovirus fusion. Our results indicate that N-glycans on NiV-F protect NiV from antibody neutralization, suggest that this “shielding” role comes together with limiting cell-cell fusion and viral entry efficiencies, and point to the mechanisms underlying the hyperfusogenicity of these N-glycan mutants. These features underscore the varied roles that N-glycans on NiV-F play in the pathobiology of NiV entry but also shed light on the general mechanisms of paramyxovirus fusion with host cells.
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Zhang, Nanyan, Brian R. Curtis i Peter J. Newman. "Genetic Removal of Terminal Sialic Acid Residues from the O-Linked Glycans Adjacent to the HPA-9b Polymorphism of Platelet Membrane Glycoprotein IIb Improves the Binding and Detection of HPA-9b Patient Alloantibodies". Blood 138, Supplement 1 (5.11.2021): 352. http://dx.doi.org/10.1182/blood-2021-144718.
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Abstract Sialic acids occupy the terminal position of glycan chains, and have the potential to influence the antigenicity of glycoproteins. Antibody binding sites on a glycoprotein can be solely protein in nature, or can include or be affected by nearby glycan chains, which may either mask the epitope, or conversely comprise part of the antibody binding site. The polymorphisms responsible for formation of the Human Platelet Alloantigens (HPA)-3 (Ile843Ser) and HPA-9 (Val837Met) are next to each other near the C-terminus of the extracellular domain of platelet membrane glycoprotein (GP)IIb, and are adjacent to sialyl-Core 1 O-glycans that emanate from serines 845 and 847. Previous studies have shown that these O-linked glycans are required to support the binding of some of HPA-3a alloantibodies. Loss of these glycans, especially terminal sialic acid residues, during platelet storage or preparation, can present major difficulties in detecting clinically important anti-HPA-3a alloantibodies in suspected cases of fetal/neonatal alloimmune thrombocytopenia (FNAIT). Similarly, detection and identification of anti-HPA-9b alloantibodies from FNAIT patient sera can also be extremely challenging, resulting in the inability to resolve clinical cases of this bleeding disorder. Whether the nearby O-glycans on serines 845 and 847 of GPIIb affect the antigenicity of HPA-9b, and/or influence the binding of anti-HPA-9b alloantibodies in clinically significant cases of FNAIT is unknown. We previously reported the generation of bioengineered, HLA class I-negative, HPA-9a or -9b allele-specific megakaryocytes (MKs) from human induced pluripotent stem cells (iPSCs) that are suitable for whole-cell flow cytometric detection of anti-HPA-9b alloantibodies (Blood 2019;134(22):e1-e8). Unexpectedly, treatment of these allele-specific MKs with neuraminidase actually enhanced the binding of anti-HPA-9b alloantibodies, suggesting that terminal sialic acids on GPIIb partially mask the HPA-9b epitope. To test the hypothesis that removal of terminal sialic acids on nearby O-glycans, or removal of the entire O-glycan chains emanating from Ser845/847 of GPIIb, might enhance the detection of anti-HPA-9b patient alloantibodies, we created a series of deletion mutants in two major sialidases, ST3GAL1 and ST3GAL2, known to be responsible for transferring terminal sialic acid residues to Core 1 O-glycans, in our HPA-9a and -9b allele-specific iPSCs. Immunoprecipitation/western blot analysis confirmed the complete removal of terminal sialic acids on the O-glycan chains of GPIIb in ST3GAL1/2 knockout (KO) iPSC-derived MKs, as reported by the binding of the lectin PNA to the exposed Core 1 structure on GPIIb. These sialylation-deficient ST3GAL1/2 KO HPA-9b MKs exhibited dramatically increased anti-HPA-9b alloantibody binding, further confirming the notion that HPA-9b epitopes are partially masked by terminal sialic acids on nearby GPIIb O-glycan chains. Finally, allele-specific iPSCs lacking the complete O-glycan chains attached to serines 845 and 847 of GPIIb were generated by mutating those residues to alanines using a similar CRISPR/Cas9 gene editing approach. Interestingly, O-glycan chain-deficient Ala845/847 mutant MKs carrying the HPA-9b polymorphism exhibited slightly to moderately reduced binding of anti-HPA-9b alloantibodies, indicating that the presence of the Core 1 O-glycan chains attached to GPIIb serine residues 845 and 847 contribute to the presentation of the HPA-9b epitope - perhaps by stabilizing the conformation of the glycoprotein in this region. Taken together, these data suggest that detection of anti-HPA-9b alloantibodies may be enhanced through the use of iPSC-derived HPA-9b-specific MKs that have been genetically altered to lack nearby terminal sialic acid residues, but retain the glycan chains to which they are attached. Disclosures Curtis: Rallybio: Consultancy. Newman: Rallybio: Consultancy, Research Funding.
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Chen, Ping, Ran Liu, Mengmeng Huang, Jinlu Zhu, Dong Wei, Francis J. Castellino, Guanghui Dang i in. "A unique combination of glycoside hydrolases in Streptococcus suis specifically and sequentially acts on host-derived αGal-epitope glycans". Journal of Biological Chemistry 295, nr 31 (9.06.2020): 10638–52. http://dx.doi.org/10.1074/jbc.ra119.011977.
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Infections by many bacterial pathogens rely on their ability to degrade host glycans by producing glycoside hydrolases (GHs). Here, we discovered a conserved multifunctional GH, SsGalNagA, containing a unique combination of two family 32 carbohydrate-binding modules (CBM), a GH16 domain and a GH20 domain, in the zoonotic pathogen Streptococcus suis 05ZYH33. Enzymatic assays revealed that the SsCBM-GH16 domain displays endo-(β1,4)-galactosidase activity specifically toward the host-derived αGal epitope Gal(α1,3)Gal(β1,4)Glc(NAc)-R, whereas the SsGH20 domain has a wide spectrum of exo-β-N-acetylhexosaminidase activities, including exo-(β1,3)-N-acetylglucosaminidase activity, and employs this activity to act in tandem with SsCBM-GH16 on the αGal-epitope glycan. Further, we found that the CBM32 domain adjacent to the SsGH16 domain is indispensable for SsGH16 catalytic activity. Surface plasmon resonance experiments uncovered that both CBM32 domains specifically bind to αGal-epitope glycan, and together they had a KD of 3.5 mm toward a pentasaccharide αGal-epitope glycan. Cell-binding and αGal epitope removal assays revealed that SsGalNagA efficiently binds to both swine erythrocytes and tracheal epithelial cells and removes the αGal epitope from these cells, suggesting that SsGalNagA functions in nutrient acquisition or alters host signaling in S. suis. Both binding and removal activities were blocked by an αGal-epitope glycan. SsGalNagA is the first enzyme reported to sequentially act on a glycan containing the αGal epitope. These findings shed detailed light on the evolution of GHs and an important host-pathogen interaction.
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Kong, Leopold, Alba Torrents de la Peña, Marc C. Deller, Fernando Garces, Kwinten Sliepen, Yuanzi Hua, Robyn L. Stanfield, Rogier W. Sanders i Ian A. Wilson. "Complete epitopes for vaccine design derived from a crystal structure of the broadly neutralizing antibodies PGT128 and 8ANC195 in complex with an HIV-1 Env trimer". Acta Crystallographica Section D Biological Crystallography 71, nr 10 (26.09.2015): 2099–108. http://dx.doi.org/10.1107/s1399004715013917.
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The HIV-1 envelope gp160 glycoprotein (Env) is a trimer of gp120 and gp41 heterodimers that mediates cell entry and is the primary target of the humoral immune response. Broadly neutralizing antibodies (bNAbs) to HIV-1 have revealed multiple epitopes or sites of vulnerability, but mapping of most of these sites is incomplete owing to a paucity of structural information on the full epitope in the context of the Env trimer. Here, a crystal structure of the soluble BG505 SOSIP gp140 trimer at 4.6 Å resolution with the bNAbs 8ANC195 and PGT128 reveals additional interactions in comparison to previous antibody–gp120 structures. For 8ANC195, in addition to previously documented interactions with gp120, a substantial interface with gp41 is now elucidated that includes extensive interactions with the N637 glycan. Surprisingly, removal of the N637 glycan did not impact 8ANC195 affinity, suggesting that the antibody has evolved to accommodate this glycan without loss of binding energy. PGT128 indirectly affects the N262 glycan by a domino effect, in which PGT128 binds to the N301 glycan, which in turn interacts with and repositions the N262 glycan, thereby illustrating the important role of neighboring glycans on epitope conformation and stability. Comparisons with other Env trimer and gp120 structures support an induced conformation for glycan N262, suggesting that the glycan shield is allosterically modified upon PGT128 binding. These complete epitopes of two broadly neutralizing antibodies on the Env trimer can now be exploited for HIV-1 vaccine design.
Rozprawy doktorskie na temat "Glycan Removal"
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Butchosa, Robles Núria. "Tailoring Cellulose Nanofibrils for Advanced Materials". Doctoral thesis, KTH, Biokompositer, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155056.
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Cellulose nanofibrils (CNFs) are nanoscale fibers of high aspect ratio that can be isolated from a wide variety of cellulosic sources, including wood and bacterial cellulose. With high strength despite of their low density, CNFs are a promising renewable building block for the preparation of nanostructured materials and composites. To fabricate CNF-based materials with improved inherent rheological and mechanical properties and additional new functionalities, it is essential to tailor the surface properties of individual CNFs. The surface structures control the interactions between CNFs and ultimately dictate the structure and macroscale properties of the bulk material. In this thesis we have demonstrated different approaches, ranging from non-covalent adsorption and covalent chemical modification to modification of cellulose biosynthesis, to tailor the structure and surface functionalities of CNFs for the fabrication of advanced materials. These materials possess enhanced properties such as water-redispersibility, water absorbency, dye adsorption capacity, antibacterial activity, and mechanical properties. In Paper I, CNFs were modified via the irreversible adsorption of carboxymethyl cellulose (CMC). The adsorption of small amounts of CMC onto the surface of CNFs prevented agglomeration and co-crystallization of the nanofibrils upon drying, and allowed the recovery of rheological and mechanical properties after redispersion of dried CNF samples. In Paper II, CNFs bearing permanent cationic charges were prepared through quaternization of wood pulp fibers followed by mechanical disintegration. The activation of the hydroxyl groups on pulp fibers by alkaline treatment was optimized prior to quaternization. This optimization resulted in individual CNFs with uniform width and tunable cationic charge densities. These cationic CNFs demonstrated ultrahigh water absorbency and high adsorption capacity for anionic dyes. In Paper III, via a similar approach as in Paper II, CNFs bearing polyethylene glycol (PEG) were prepared by covalently grafting PEG to carboxylated pulp fibers prior to mechanical disintegration. CNFs with a high surface chain density of PEG and a uniform width were oriented to produce macroscopic ribbons simply by mechanical stretching of the CNF hydrogel network before drying. The uniform grafted thin monolayer of PEG on the surface of individual CNFs prevented the agglomeration of CNFs and facilitated their alignment upon mechanical stretching, thus resulted in ribbons with ultrahigh tensile strength and modulus. These optically transparent ribbons also demonstrated interesting biaxial light scattering behavior. In Paper IV, bacterial cellulose (BC) was modified by the addition of chitin nanocrystals (ChNCs) into the growing culture medium of the bacteria Acetobacter aceti which secretes cellulose in the form of entangled nanofibers. This led to the in situ incorporation of ChNCs into the BC nanofibers network and resulted in BC/ChNC nanocomposites exhibiting bactericidal activity. Further, blending of BC nanofibers with ChNCs produced nanocomposite films with relatively lower tensile strength and modulus compared to the in situ cultivated ones. The bactericidal activity increased significantly with increasing amount of ChNCs for nanocomposites prepared by direct mixing of BC nanofibers and ChNCs. In Paper V, CNFs were isolated from suspension-cultured wild-type (WT) and cellulose-binding module (CBM) transformed tobacco BY-2 (Nicotiana tabacum L. cv bright yellow) cells. Results from strong sulfuric acid hydrolysis indicated that CNFs from transgenic cells overexpressing CBM consisted of longer cellulose nanocrystals compared to CNFs from WT cells. Nanopapers prepared from CNFs of transgenic cells demonstrated significantly enhanced toughness compared to CNFs of WT cells.QC 20141103
CARBOMAT
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Luo, Ying. "SLURRY CHEMISTRY EFFECTS ON COPPER CHEMICAL MECHANICAL PLANARIZATION". Master's thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4470.
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Chemical-mechanical Planarization (CMP) has emerged as one of the fastest-growing processes in the semiconductor manufacturing industry, and it is expected to show equally explosive growth in the future (Braun, 2001). The development of CMP has been fueled by the introduction of copper interconnects in microelectronic devices. Other novel applications of CMP include the fabrications of microelectromechanical systems (MEMS), advanced displays, three dimensional systems, and so on (Evans, 2002). CMP is expected to play a key role in the next-generation micro- and nanofabrication technologies (Singh, et al., 2002). Despite the rapid increase in CMP applications, the fundamental understanding of the CMP process has been lacking, particularly the understanding of the wafer-slurry-pad interactions that occur during the CMP process. Novel applications of CMP are expected to expand to materials that are complex chemically and fragile mechanically. Thus, fundamental understanding and improvement of slurry design for CMP is the key to the development of sophisticated next-generation CMP processes. Slurry performance for CMP can be determined by several output parameters including removal rate, global planarity, surface topography, and surface defectivity. To achieve global planarity, it is essential to form a very thin passivating surface layer (<2 nm) that is subsequently removed by the mechanical component of the slurry (Kaufman et al., 1991) or by combined chemo-mechanical effects (Tamboli, 2000). Chemical additives like hydrogen peroxide (H?O?), potassium ferricyanide, and ferric chloride are added to slurries as oxidizers in order to form a desirable surface layer. Other chemical additives such as inhibitors (e.g. benzotriazole) and complexing agents (e.g. ammonia) are added to the copper slurry in order to modify the oxide layer. That the removal rate of the thin surface layer is greater at the highest regions of the wafer surface than at the lowest regions leads to surface planarity. In this study, various complexing agents and inhibitors are combined to form slurry chemistry for copper CMP processing in H?O? based slurries at pH values ranging from 2 to 10. Two complexing agents (glycine and Ethylenediamine) and one inhibitor (3-amino-1, 2, 4-triazole) were selected as slurry constituents for detailed chemical synergistic effect study because they showed good materials removal and surface planarity performances. To understand the fundamental mechanisms involved in copper CMP process with the afore-mentioned slurry chemical formations, various techniques, such as electrochemical testing techniques (including potentiodynamic polarization and electrochemical impedance spectroscopy), x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM), were applied. As a result, guidelines for optimized slurry chemical formulation were arrived at and the possible mechanisms of surface-chemical-abrasive interactions were determined. From applications point of view, this study serves as a guide for further investigations in pursuing highly effective slurry formulations for copper/low-k interconnect applications.M.S.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical, Materials and Aerospace Engineering;
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Rathore, Ujjwal. "HIV-1 Immunogen Design : Envelope Protein Minimization, Stabilization and Glycan Removal". Thesis, 2015. http://etd.iisc.ac.in/handle/2005/4093.
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Effective vaccines exist for a number of viral diseases. However, despite much effort, there is no successful vaccine against the Human Immunodeficiency Virus (HIV-1). The envelope glycoprotein (Env) of HIV-1 gp120, the most exposed protein on the viral surface is an important candidate for vaccine design. The primary reason for the difficulty in generating an effective neutralizing antibody response against HIV-1 lies in extensive Env sequence variability. Apart from sequence variation, HIV-1 deploys a number of defence mechanisms to evade the host immune response. The gp120 protein is one of the most heavily glycosylated viral proteins known with ~50% of its molecular mass contributed by glycans. The extensive glycosylation of gp120 helps to mask critical neutralization epitopes, although some bNAbs target glycan dependent epitopes in order to achieve virus neutralization. In addition, the presence of long, variable immunodominant loops focuses the immune response away from conserved epitopes. Certain conserved epitopes are cryptic and are exposed only after gp120 binds to CD4. Moreover, the highly flexible nature of gp120 and the labile nature of the gp120:gp41 complex makes structural characterization extremely difficult. Shed gp120 samples various non-native conformations that are likely to be absent in native Env and that elicit non-neutralizing antibodies. Despite these defence mechanisms, about 20-30% of HIV-1 patients do generate a broad neutralization response and around 1% of them do so with high potency. Although these bNAbs and their epitopes have been identified, eliciting similar bNAbs through immunization is challenging.
Monomeric gp120 is an obvious candidate immunogen, due to its surface accessibility and immunogenicity during natural infections. Initial immunization studies with full length monomeric gp120 failed to elicit neutralizing antibodies and failed to show protection in a human clinical trial. This indicates that neutralization epitopes are not optimally presented on monomeric gp120. Elicitation of neutralizing antibodies is a desirable feature of a vaccine. Thus a rational design approach to focus the immune response towards specific epitopes targeted by known bNAbs is urgently required. The aim of any rational immunogen design methodology targeting HIV-1 is to maximize the exposure of conserved neutralization epitopes and to simultaneously ensure minimal exposure of variable non neutralizing epitopes to the immune system. This can likely be achieved either by (a) stabilization of native Env trimers, or/and by (b) protein fragment design.
Chapter 1 gives a brief overview of the HIV-1 virus, and outlines the structural organization of its Env protein. The difficulties in generating an effective HIV-1 vaccine and the recent advances in rational structure based HIV-1 vaccine design are discussed.
The outer domain (OD) of HIV-1 Env glycoprotein gp120 contains the site for the binding of cellular receptor CD4 and epitopes for a large number of recently discovered broadly neutralizing antibodies (bNAbs). Therefore, OD is considered to be an important candidate for structure-based vaccine design and for designing minimal gp120 immunogens. We have previously reported the design and characterization of a non-glycosylated, E. coli expressed outer domain immunogen (ODEC) that bound CD4 and bNAb b12 with micromolar affinity and elicited a modest neutralizing antibody response in rabbits (Bhattacharyya et al., 2010a). In Chapter 2, we report the design and characterization of an engineered bridging sheet deleted variant of ODEC (ODEC∆BS), which showed significant improvement in biophysical properties over the original ODEC molecule (∆Tm = 6.6°C) and bound bNAb VRC01 with improved affinity (KD of ~100-150nM). In another approach, we engineered an OD molecule (ODECConsensus) using consensus based protein design methodology. Consensus mutations are generally believed to improve the thermal stability of proteins. ODECConsensus showed improvement in biophysical properties (∆Tm = ~3.0°C) and in binding affinities with bNAbs such as VRC01 and b12 (KD of ~60-80nM) as compared to ODEC. When these two improved designs were used as immunogens in rabbits, the resultant sera showed significantly higher anti-gp120 titers as compared to the original ODEC design and in addition, showed cross-clade neutralization of Tier 1 viruses.
HIV-1 Env protein gp120 is heavily glycosylated with approximately 25 glycosylation sites of which ~4 are located in the inner domain, ~7-8 in the V1V2 and V3 variable loops and the rest in the outer domain (OD) of gp120. Glycans partially shield Env from recognition by the host immune system and are believed to be indispensable for proper folding of gp120. It is not known how many of the ~25 glycans present on the gp120 surface are essential for folding. This is an important question as these glycans mask various conserved epitopes on the viral surface and thereby impede the development of an effective gp120 based vaccine. In addition, several recently isolated bNAbs bind to specific glycans on gp120. If the importance of each PNGS in maintaining the structural and functional integrity of gp120 could be determined, then this information could be used to modulate coverage of Env by glycans.
In chapter 3, Using rationally designed mutations and yeast surface display (YSD), we show that glycosylation is not essential for the correct in vivo folding of gp120 outer domain fragment alone or outer domain in the context of core gp120. Following randomization of the remaining four glycosylation sites and screening by yeast surface display, two core gp120 mutants were isolated which contained a single inner domain glycan, retained yeast surface expression and bNAb binding. This demonstrates that most core gp120 glycans are dispensable for folding in the absence of gp41. Presence of either N88 or N241 glycan was found to be essential for the folding of core gp120. Both N88 and N241 belong to the inner domain of gp120, which interacts with gp41. Since gp41 was absent in the core gp120 constructs, we hypothesized that removal of these inner domain glycans might result in exposure of hydrophobic surface and consequently aggregation of core gp120. An ODEC variant lacking all 14 potential N-glycosylation sites (PNGS) was purified from E.coli (ΔG-ODEC). ΔG-ODEC is devoid of the inner domain, part of the bridging sheet, V1/V2/V3 variable loops and has a fivefold lower molecular weight than full length gp120. However, it could still bind bNAb b12, bNAb VRC01 and CD4 with affinities comparable to that of full length gp120 (KD of ~10-50nM).
Human bNAbs that prevent viral entry into cells arise after several years of infection, but are extensively mutated. Unmutated (germline) versions of these antibodies generally do not show measurable binding with WT gp120. Hence such antibodies are difficult to elicit through immunization with Env. It has been proposed that immunogens that bind well to germline precursors of bNAbs as well as the corresponding mature antibodies may help to elicit such bNAbs upon vaccination. Glycan free ΔG-ODEC could bind to the germline variant of bNAb VRC01 with high affinity (KD of ~10nM) without any requirement for additional mutations. The results from Chapter 3 inform immunogen design, targeting mature as well as GL bNAbs, clarify the role of glycosylation in gp120 folding and illustrate general methodology for design of glycan free, folded protein derivatives.
Apart from gp120 folding, glycosylation is also considered to be essential for Env native trimer formation and for viral infectivity. Most of the studies done to examine the effect of glycan removal on viral infectivity were performed with single site mutants. Whenever multiple sites were mutated in combination, it resulted in loss of viral infectivity which led to the hypothesis that a certain level of glycan coverage is essential for maintaining infectivity of the virions. In Chapter 4, we studied the importance of glycosylation in maintenance of native Env trimers and viral infectivity. By introducing rational mutations at potential N-glycosylation sites, we could show that Env lacking all core gp120 glycans can retain native trimeric structure. We used pseudoviral neutralization assays to show that infectivity can be retained in the absence of all glycans from core gp120, if mutations are introduced rationally. Loss of infectivity, in the earlier studies can be attributed to non-optimal substitutions (hydrophilic and uncharged mutations) at the PNGS, which probably failed to rescue the folding of Env, in the absence of glycans.
We also found that recognition of a germline reverted version of bNAb VRC01 increases substantially with the progressive loss of glycans from JRFL pseudoviruses, indicating that one way by which glycans can shield the virus from the host immune response could be by reducing the interaction with germline antibodies. These deglycosylated constructs can also be used in DNA immunizations as they will quite likely activate a large number of germline variants including those of bNAbs. Combinations of these molecules in various prime: boost regimes will be helpful in expanding our understanding about the role of glycosylation in modulating the gp120 directed immune response. Knowledge of these mutations which can be tolerated at PNGS in gp120 would also be useful for structure determination of full length gp120 and native Env trimers in the future as extensive glycosylation has rendered this task extremely difficult. Further, the methodology outlined in this work can in principle be used to probe the role of glycans in the stability and folding of any glycosylated protein.
In Chapter 5, we have attempted to further improve the binding and biophysical properties of ODEC immunogens by reducing their conformational flexibility. As disulfides have long been known to stabilize proteins by reducing the entropy of the unfolded state, we attempted to rationally engineer cross-strand disulfides in ODEC, in order to reduce the conformational flexibility of the molecule. In another design, we have introduced previously known cavity filling mutations to reduce the flexibility of ODEC by restricting it in the ‘CD4 bound state’. Finally, we combined the rational stabilizing mutations with the glycosylation site mutations to generate second generation OD immunogens capable of binding to various CD4 binding site (CD4bs) ligands with affinities comparable to that of full length WT gp120 (~10-50nM KD). In another slightly different approach to design an OD immunogen, we made a cyclic permutant of ODEC (CycV4OD), which resulted in a drastic improvement in the binding affinities for CD4, bNAb b12 and bNAb VRC01 (~10-45nM KD) without any additional mutations. When tested in rabbits, the two immunogens designed in the current study, showed improvement in their ability to generate anti-gp120 sera and neutralizing antibody against Tier 1 viruses relative to the previous immunogens.
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Das, Raksha. "Effects of Cyclic Permutation, Glycan Removal and Aspartate Mutagenesis on Conformation of HIV-1 Envelope". Thesis, 2017. http://etd.iisc.ac.in/handle/2005/4169.
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It has been decades since Human Immunodeficiency Virus-1 (HIV-1) was discovered. The virus has created havoc worldwide. According to the UNAIDS 2014 Gap report, 35million people worldwide are infected with HIV-1 and yet there is no vaccine. The most abundant and exposed protein on the HIV-1 virion surface is Envelope (Env) glycoprotein. HIV-1 uses its Env glycoprotein to infect host cells. HIV-1 Env glycoprotein exists as a trimer of heterodimers of gp120 and gp41. gp120 is the surface exposed and gp41 the membrane anchored subunit. gp120, being surface exposed, is the primary target of neutralizing antibodies and therefore is an important candidate for immunogen design. The generation of an effective HIV-1 vaccine is a challenging job because the HIV-1 virus has acquired many immune evasive mechanisms. The HIV-1 virus has high sequence variability, because of which it is difficult to make a vaccine that can effectively act against all viral strains. HIV-1 gp120 is extensively glycosylated and thus much of the surface is concealed from the host immune system. It also has immunodominant loops that are highly exposed in shed gp120 and can drive the immune focus towards a non-neutralizing response. There are different strategies that have been employed in the search for an HIV-1 vaccine. Chapter 1, contains a brief introduction of HIV-1, the difficulties in eliciting neutralizing antibodies and the strategies employed so far in Env based immunogen design. In Chapter 2, we describe the use of cyclic permutation as a strategy to trimerize gp120 in the absence of gp41. Normally, the Env trimer present on the cell surface exists as a trimer of gp120 and gp41 heterodimers. The trimerization is largely mediated by gp41 and assisted by V1V2 loops on gp120 that form the apex of the trimer. The antibodies generated against gp41 are autoreactive and more often non-neutralizing. To avoid that, only gp120 was used as an immunogen and to trimerize gp120 in the absence of gp41, a cyclic permutant of gp120 was made. The original N and C termini were joined by a linker and new N and C termini were generated in the V1 loop region. The V1 loop is a flexible region in gp120 and can tolerate insertions at the chosen location between residues 143 and 144. The trimerization domain, human cartilage matrix protein (hCMP), was linked at the new N terminus of the V1 loop. In a separate construct, hCMP was also linked to the C terminus of gp120 as a negative control. We found that the resulting V1 cyclic permutants JRCSF-hCMP-V1cyc and JRFL-hCMP-V1cyc improved the binding of gp120 to broadly neutralizing antibodies like VRC01 and VRCPG04 (CD4 binding site antibodies) and reduced the binding to non-neutralizing antibodies like b6 and F105. These cyclic permutants showed ~ 10-20 fold increase in binding to the quaternary epitope specific broadly neutralizing antibodies PGT145, PG9, PG16, and PGDM 1400. The gp120 cyclic permutants showed an increased thermal stability by 4˚C compared to Wtgp120 and were shown to be trimeric by negative stain EM. On immunization in guinea the resulting sera could neutralize a subset of heterologous cross clade Tier-2 viruses. Some of the neutralization response was CD4 binding site directed. gp120 is a heavily glycosylated molecule. It contains ~25 glycosylation sites, ~14-15 in the outer domain, ~4 in the inner domain, ~7-8 in the V1V2 and V3 loops. Earlier it was believed that glycosylation is indispensable for viral infectivity as well as for proper folding of Env. In Chapter 3, we investigated the effect of removal of glycans from core gp120 on viral infectivity and conformation of the soluble protein. The glycans from gp120 were rationally removed by mutating to the second most frequent residue in a multiple sequence alignment. In natural infection, it takes many years to generate broadly neutralizing antibodies. During the course of development, the antibodies undergo extensive affinity maturation from their germline unmutated versions. It is observed that the glycosylated wild type gp120 does not bind to the germline reverted version of the broadly neutralizing, CD4 binding site antibody VRC01, and the binding progresses with the removal of glycans. We show that the removal of glycosylation from the outer domain of core gp120 in the JRFL molecular clone does not affect viral infectivity. The viral fitness of virus lacking glycans in core gp120 was assessed in HUTR5 cells. It was found that the infectivity of glycan deficient virus is higher than wild type, suggesting that the primary role of glycosylation is not to stabilize Env conformation, but rather to shield the molecule from the humoral immune system. We show that upon selective removal of glycosylation from the outer domain of the trimeric cyclic permutant of JRFL described in (chapter 2), the conformational integrity of the cyclic permutant is not perturbed. The glycan deficient molecules bound to the trimer specific, quaternary epitope targeting antibodies like PGDM 1400 similarly to the wild type molecule. It also bound mature VRC01 with an affinity similar to the WT. The glycan deficient molecules bound weakly to
germline reverted VRC01 but the wild type molecule did not bind at all. Such glycan-deficient molecules can be used in immunizations to target germline B cells and can potentially broaden the antibody response. A high resolution crystal structure of the Env trimer in the absence of any stabilizing ligands is needed for an effective immunogen design. All the existing crystal and EM structures contain one or more ligands. In most structures of the soluble gp140 ectodomain of HIV-1, no density is visible for residues 512-517 of fusion peptide and 547-568 of the N-heptad region of gp41. In Chapter 4, we have used an aspartate scanning mutagenesis strategy to probe the residue burial of these gp41 regions for which the electron density is missing in most structures. We mutated these residues individually into aspartate in the mammalian cell surface expression plasmid JRFLgp160dCT and the effect of mutations was assessed by FACS. Cell surface expression of Env was monitored using 2G12 binding. The conformational integrity was probed by binding of conformational specific CD4 binding site neutralizing antibody b12 and non-neutralizing antibody b6. The b12/b6 ratio differentiates the effect of different mutations on native trimer integrity compared to the wild-type. V513D, Q562D, L576D, I580D were the mutations, highly affecting the expression and trimer integrity. L576 and I580 are both buried in the native Env. However, Q562 is not, so this is not consistent with the existing structures. Asp substitutions at several other residues in this region also appear to affect the native trimer integrity, suggesting that the region is unlikely to be disordered in native Env on the virion surface. The NHR and CHR regions of gp41form a six-helix bundle post fusion of viral and cellular membranes. In this structure, the three CHR wrap around the NHR trimer. We previously showed the V570D mutation, that destabilizes the six-helix bundle also prevents gp120 shedding without significantly perturbing the conformation of native Env. We, therefore, examined the effects of Asp mutants that apparently have native like conformation on CD4 induced, gp120 shedding. R557D, A558D, A561D, Q563D, R564D, M565D were all able to prevent gp120 shedding, but, N553D, N554D, Q560D could not prevent gp120 shedding. Several residues preventing gp120 shedding, namely R557D, A558D, A561D, Q563D, R564D, M565D are exposed in the native trimer, but surprisingly R557D and R564D are exposed in the post fusion form as well (PDB 1AIK). The mutations L555D, I559D, Q562D, L566D, T569D, L576D and I580D are all buried in the post fusion structure. Pseudoviral infectivity studies showed that virus loses all its infectivity in the presence of these mutants, presumably because they disrupt the six helix bundle formation. Residues preventing CD4 shedding are able to lock the trimer in a pre-fusion context on the cell surface. However, further studies need to be done in the context of a soluble trimeric protein, which can be used as an immunogen.
The native trimer is metastable. In Chapter 5, we have explored the utility of priming with gp160 DNA and boosting with trimeric gp120 or gp140 in prime boost immunizations in rabbits. We have used JRFLgp160dCT-V570D (dCT is cytoplasmic tail truncated), JRFLgp160dCT-Wt, and JRFL gp160dCT-SEKS (non-cleavable gp160) as DNA prime and boosted with JRFL-hCMP-V1cys or with ZAFV gp140 protein. In another set of studies, animals were subjected to a protein prime with variants of the gp120 outer domain and boosted with JRFL-hCMP-V1cyc or ZAFV g140. However, only Tier 1 neutralization was observed. Further work is needed to optimize these immunogens in order to elicit broadly neutralizing antibodies.
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黃韻儒. "Removal of N-linked glycan(s) in the stem region of influenza A virus hemagglutinin proteins to elicit heterosubtypic neutralizing antibodies and cross-protective immunity". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/53004753703006004625.
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Tsai, Pei-Yuan, i 蔡培元. "Removal of Propylene Glycol Monomethyl Ether Acetate by Biofiltration Process". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/78099269092033673200.
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碩士國立交通大學
分子醫學與生物工程研究所
98
This research is aimed to establish an effective biofiltration process which applys to remove the water-soluble organic waste gases emission from semiconductors and photonics industry. The target pollutant is focus on propylene glycol monomethyl ether acetate (PGMEA), which is harmful for human body, especially for liver and kidney. The objective of this study is to estimate the removal efficiency in different conditions by three kinds of biofiltration processes. The data showed that it could remove 100-300 ppm PGMEA for 98% removal efficiency (RE) in biofilter system, 93% in bioscrubber system with retention time (RT) in 20 seconds, and 93% RE in plate membrane bioscrubber system with RT in 30 seconds. The elimination capacity achieved 212, 258 and 150 g-PGMEA/m3/hr for biofilter, bioscrubber and plate membrane bioscrubber, respectively. In addition, to study the effect of amount of seeding in bioscrubber and plate membrane bioscrubber. It showed that high amount of seeding (over 109 CFU/ml) was helpful for high RE (up to 98%) and stable for operation. Finally, we estimated the addition of extra packing materials in biofilter and bioscrubber. The data showed that the bioscrubber with extra packing materials could achieve RE 90% in short time, while there was no difference in biofilter. Therefore, the optimal operation parameters for removal of PGMEA were obtained, and it could establish field-scale bioreactors for application in industrial field.
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Lin, Chia-Wei, i 林家緯. "Iron and Manganese doped CuO by Glycine Nitrate Process for Organic Pollutant Removal". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/bfr4gz.
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碩士國立臺北科技大學
環境工程與管理研究所
101
Nonylphenol polyethoxylate (NP9EO) is the most commonly used nonionic surfactant, but the microbial degradation of NP9EO would generate nonylphenol which is a persistent pollutant and classified as environmental hormones. The study was separated into two parts: preparation of photocatalyst and photocatalytic application. The synthesized photocatalyst was generated by combustion method with synthesis gel type precursor prepared by different glycine/nitrate ratio in solution with different pH of 2, 6 and 10, and the combustion synthesis method were also applied for modification of catalyst using iron and manganese doped with copper oxide. Finally, the synthetic catalyst was used for the degradation experiment of organic pollutant NP9EO. The crystalline phase of material generated from G/N = 0.3 and pH = 2 was mainly CuO, and the CuO can be reduced to Cu2O or Cu with increase of pH or G/N. More Cu2O and Cu were generated since glycine and ammonia were served as a reducing agent. Synthetic particles grew with increase of G/N, and there was an obvious agglomeration with pH 6 and 10. The crystalline phase of products generated from doping the transition metals was mainly CuO, which was observed with TEM. The CuO structure was agglomerated with particles smaller than 50 nm, and were mostly reticulated and porous. The size of crystal lattice calculated by the Scherrer equation was between 10 ~ 25 nm. When Fe/Cu=10-2, the specific surface area increased to 8.6 m2/g and increased to 11.8 m2/g when Mn/Cu=10-2. The experimental condition of photocatalytic was set as NP9EO = 100 mg/L, pH = 6, UV light = 254 nm and light intensity = 2.5 W/m2 with two catalysts of G/N = 0.3 and pH 2 and 10 respectively. The results show, the removal was higher with pH = 10, and the decomposition efficiency of NP9EO was 82.47 %. Apparently, Cu2O can improve the NP9EO removal efficiency more than CuO. In experiments of doping the transition metal elements, the efficiency of NP9EO degradation decrease after doping, and the lower band gap resulted in lower ability in oxide reduction of catalyst. While the ratio of transition metal doped with Cu was 10-4 with concentration of 0.1 M hydrogen peroxide and catalyst dosage 0.3 g/L, the removal efficiency for NP9EO was much better, the removal rates for iron and manganese doped catalysts were 74.58 % and 82.91 %, respectively. The optimized transition metal doped ratios for removal efficiency for iron and manganese were 5×10-4 and 10-2 with H2O2 of 0.1 M and catalyst dosage of 0.1 g/L. TOC removal efficiency (between 10 ~ 30 %) was lower than NP9EO due to by-products from decomposition of NP9EO still are the source of organic carbon.
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Jang, Liang-Wei, i 張良偉. "Production of Nanascale Copper Oxide by GNP（glycine-nitrate process）for Organic Pollutant Removal". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/x6hm26.
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碩士國立臺北科技大學
環境工程與管理研究所
100
A new combustion synthesis method, the glycine-nitrate process, has been used to prepare copper oxide powders. A precursor was prepared by combining glycine with metal nitrates in stoichiometric ratios in an aqueous solution. The precursor was heated to evaporate excess water, yielding a viscous liquid. Further heating to about 145°C caused the precursor liquid to self-propagating combustion. The glycine nitrate process has been successfully employed to prepare nanosized, porous copper oxide powders. Photochemical reactions catalyzed by semiconductors have been investigated extensively in the degradation of organic pollutants. Copper oxide is a photocatalyst. It can decompose the organic pollutant by irradiation under UV light. In some studies . It was demonstrated that “Cu2O/CuO” governs the capability of the heterojunction cascade and Cu does not play a significant role regardless of the heterojunction cascade efficiency. The effects of various key operating parameters and the effect of hydrogen peroxide the degradation rate of organic pollutants were studied. The SEM, TEM studies on these powders confirmed their nanosized nature and porous structure. When g/n molar is 0.3 as-prepared powders were nanosized (∼100 nm) into a spherical shape. The powders showed a very large surface area of 167 m2/g, as determined by BET surface area measurements. Then XRD pattern defines to CuO.But the particle size becomes bigger when the g/n molar increases. Because that increasing g/n molar ratio will increase flame temperature which led to particle sintering. When g/n molar is 0.5 as-prepared powders size closes 1 μm, and When g/n molar is 0.5 the catalyst size more than 1 μm. The glycine also act as reducing agent, so When g/n molar is 0.5 the catalyst includes CuO/Cu2O, and when g/n molar is 0.7 the catalyst contains Cu2O/Cu. The optimum values were 0.03 g/L of photocatalyst, 100 mg/L of NP9EO, 0.05 M of H2O2. An over 80% NP9EO and TOC removal was achieved in this catalytic oxidation.For an efficient photoactivity, low CuO concentration and sufficiently high concentration on Cu2O are requested. So when g/n molar is 0.5 of catalyst, the NP9EO removal efficiency achieved 87.7％. Cu cannot act as photosensitizer, but it can improve the photpcatalytic activity of single semiconductor by the formation of apparent ohmic junction enhancing the charges transfer kinetics.When g/n molar is 0.7 of catalyst, the NP9EO removal was achieved 94.6％. But due to the size increasing with g/n molar, so cause the particle BET decrease. When g/n molar is 0.5, the TOC removal was closed 57.6％. In same reason when g/n molar is 0.7, the TOC removal was achieved 52.8％
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Li, Houng, i 李弘. "Removal of Polyethylene Glycol in Printed Wiring Board Electroplating Solution by O3/UV Process". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/98842715405744069019.
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碩士國立臺灣大學
環境工程學研究所
87
Abstract The objective of this study is to remove polyethylene glycol (PEG) from the acid-based electroplating solution of printed wiring board (PWB) industry by ozone (O3) or ozone/ultraviolet (UV) processes. The substrates (the major chemical species) of the electroplating solution recipe are inorganics, such as sulfuric acid, copper sulfate, etc., which will not be reacted by O3 or O3/UV. Ozonation will only destroy the minor organic additives (PEG, for example). The study establishes the kinetic expression of ozone self-decomposition reaction in electroplating solution substrate with and without UV radiation by batch and semi-batch experiments. In O3/PEG or O3/UV/PEG reactions, the reaction kinetics may be simulated by a two-step reaction mechanism in terms of O3 and total organic carbon (TOC). The rate constants are estimated by comparing the simulation results with the batch experiment data. The trial-and-error and fourth-order Runge-Kutta methods with FORTRAN program are used. The employed UV light intensities [I] in O3/UV/PEG reaction are 15.8, 25.2, 35.0 and 44.4 W/m2, respectively. The initial concentration of PEG is 30 mg/L, which is equivalent to TOC of 16.3 mg/L. The obtained kinetic parameters (rate constants and reaction orders) from above are used in prediction for the semi-batch experiments of ozonation with and without UV radiation. The fourth-order Runge-Kutta method and FORTRAN program are also used in simulation. In the semi-batch O3/PEG experiment, the percentile of TOC removal (RTOC) is about 60 % as the ozone dosage in each liter of electroplating solution (mO3) =10.5 mg/min．L and ozonation time (t) = 180 min. As for the semi-batch O3/UV/PEG experiment, RTOC raises to 77.9 % when [I] = 44.4 W/m2, mO3=10.5 mg/min．L, t = 180 min. Both the variations of concentrations of liquid phase ozone and TOC of the simulation agree well with those of the experiments.
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Lin, Shouzhong Lin Shouzhong. "I. Removable arenesulfonyl groups applications in peptide synthesis : II. Asymmetric transformation in synthesis : chiral glycine enolate equivalents /". 1994. http://catalog.hathitrust.org/api/volumes/oclc/32420244.html.
Pełny tekst źródłaCzęści książek na temat "Glycan Removal"
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Muzangwa, Lindah, Isaac Gura, Sixolise Mcinga, Pearson Nyari Mnkeni i Cornelius Chiduza. "Impact of conservation agriculture on soil health: lessons from the university of fort hare trial." W Conservation agriculture in Africa: climate smart agricultural development, 293–304. Wallingford: CABI, 2022. http://dx.doi.org/10.1079/9781789245745.0018.
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Abstract Conservation Agriculture (CA) promotes soil health, but issues to do with soil health are poorly researched in the Eastern Cape, South Africa. This study reports on findings from a field trial done on the effects of tillage, crop rotations composed of maize (Zea mays L.), wheat (Triticum aestivum L.) and soybean (Glycine max L.) and residue management on a number of soil health parameters such as carbon (C)-sequestration, CO2 fluxes, enzyme activities, earthworm biomass and the Soil Management Assessment Framework soil quality index (SMAF-SQI). The field trial was done in a semi-arid region of the Eastern Cape Province, South Africa, over five cropping seasons (2012-2015). It was laid out as a split-split plot with tillage [conventional tillage (CT) and no-till (NT)] as main plot treatment. Sub-treatments were crop rotations: maize-fallow-maize (MFM), maize-fallow-soybean (MFS); maize-wheat-maize (MWM) and maize-wheat-soybean (MWS). Residue management: removal (R-) and retention (R+) were in the sub-sub-plots. Particulate organic matter (POM), soil organic carbon (SOC), microbial biomass carbon (MBC) and enzyme activities were significantly (p < 0.05) improved by residue retention and legume rotation compared to residue removal and cereal-only rotations. Also, carbon dioxide (CO2) fluxes under CT were higher compared to NT. The calculated soil quality index (SQI) was greatly improved by NT and residue retention. MWM and MWS rotations, in conjunction with residue retention under NT, offered the greatest potential for building soil health. Residue retention and inclusion of soybean in crop rotations are recommended for improving soil health under CA systems in the semi-arid regions of South Africa.
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Harbord, Nikolas B., i Muhammad S. Akhter. "Poisonings and Intoxications". W Kidney Protection, redaktorzy Vijay Lapsia, Bernard G. Jaar i A. Ahsan Ejaz, 265–74. Oxford University Press, 2019. http://dx.doi.org/10.1093/med/9780190611620.003.0027.
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Nephrologists are involved in the treatment of poisoning, as extracorporeal removal may be essential in some intoxications. After addressing the epidemiology and management considerations regarding extracorporeal therapy, the chapter outlines the clinical presentation and management of common poisonings such as toxic alcohols (methanol and ethylene glycol), salicylates, toluene, and lithium are outlined. Specific treatment within the purview of the nephrologist includes recognition and treatment of acid-base derangements, enhanced elimination, and diffusive and convective clearance. Evidence-based recommendations for the role of dialysis in these poisonings is provided. Finally, the clinical presentation and unique renal pathophysiologic effects of toluene and Cleistanthus collinus poisoning are reviewed.
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Ferreira, Isabela Natália da Silva, Rosileide Fontenele da Silva Andrade i Galba Maria of Campos Takaki. "Recent advances in soil glyphosate contamination and removal". W A LOOK AT DEVELOPMENT. Seven Editora, 2023. http://dx.doi.org/10.56238/alookdevelopv1-067.
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The soil has been constantly exposed to a variety of contaminants and their mixtures in various concentrations, organic/inorganic chemical exposure, which mainly includes pesticides and their mixtures of monomers), which contaminate the soil to a greater extent and can also be transported within the soil and transfer the mixed contaminants, integrating into the food chain and passing through different trophic levels, causing health effects of organisms exposed to them. Pesticides are chemical compounds used to eliminate pests. They are chemical or biological agents, which weaken, incapacitate and kill pests. The emerging contaminant glyphosate (N-(phosphonomethyl)glycine) is widely used in agriculture in several countries. It is considered the most widely used herbicide in the world, as well as being one of the most harmful to human health. This compound is used to control harmful or invasive weeds. Glyphosate is the best-selling active ingredient in Brazil, with 195,056 tons sold in 2018. Brazil stands out for the massive agricultural use of glyphosate. An increasing number of countries have begun to restrict/ban the use of glyphosate-based products, such as Germany, Austria, Bulgaria, Colombia, and Costa Rica, among others, based on evidence already available on the direct incidence of glyphosate at various levels of the global ecosystem, as well as favoring the emergence of serious problems in human health. In this sense, the present study emphasizes the importance of knowing the main properties of pesticides and the study in search of efficient technological advances for the recovery of soils impacted by the use of glyphosate.
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Starosta, Wojciech, Jianwei Ren i Philiswa Nosizo Nomngongo. "Synthesis of zirconium porous sorbents from waste PET flakes". W Waste PET-MOF-Cleanwater: Waste PET-Derived Metal-Organic Framework (MOFs) as Cost-Effective Adsorbents for Removal of Hazardous Elements from Polluted Water, 19–32. UJ Press, 2022. http://dx.doi.org/10.36615/9781776419463-02.
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Polyethylene terephthalate (PET) is a thermoplastic polymer synthesised by polycondensation of terephthalic acid and ethylene glycol monomers. Developed in 1942, it found its way into fiber production. The advances in polymer processing in the 1970s, in particular the development of injection stretch blow molding process, made the mass production of beverage bottles possible. Since then, PET polyester has been an excellent choice as a material in many industries. Factors such as its chemical resistance, strength-to-weight ratio, shatterproof properties, and low cost to product, make it an accessible solution for consumable product packaging [1].
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Weinfeld, Michael, James Z. Xing, Jane Lee, Steven A. Leadon, Priscilla K. Cooper i X. Chris Le. "Factors influencing the removal of thymine glycol from DNA in γ-irradiated human cells". W Base Excision Repair, 139–49. Elsevier, 2001. http://dx.doi.org/10.1016/s0079-6603(01)68096-6.
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Naor-Revel, Shani, Ruth Goldstone i Ariel Revel. "Hysteroscopy, the Window into the Uterine Cavity". W Advances in Minimally Invasive Surgery. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.99069.
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Hysteroscopy, is a technique by which we can look into the uterine cavity entering through the cervix and is today the most applied minimally invasive technique in Gynecology. Indications for hysteroscopy include infertility investigation, abnormal uterine bleeding, and evaluation of suspicious sonographic findings. Nowadays we approach the uterus via vaginoscopy with no anesthetic. Once inside the uterus, we remove polyps or stringless IUD and take a biopsy. These procedures are often referred as “see and treat”. Operative hysteroscopy under GA or sometimes cervical block, uses larger instruments to resect myomas, cut a septum (metroplasty) or separate intrauterine adhesions (Asherman’s). As Glycine is no more used in hysteroscopy it has become quite a safe procedure. Use of disposable scopes will enable this tool to be part of every gynecologic clinic.
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Lambert, Tristan H. "Functional Group Protection". W Organic Synthesis. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190200794.003.0012.
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An efficient method for allylation of a sterically hindered alcohol in the presence of base-sensitive functionality (cf. 1 to 2) has been developed (Tetrahedron Lett. 2012, 53, 1319) by Richard B. Silverman at Northwestern University. Mark S. Taylor at the University of Toronto found (J. Am. Chem. Soc. 2012, 134, 8260) that borinic acid 4 catalyzed the monofunctionalization of diols and carbohydrates such as 3. The selective functionalization of unprotected peptides can be challenging, but Man-Kin Wong at Hong Kong Polytechnic University and Chi-Ming Che at the University of Hong Kong have shown (J. Am. Chem. Soc. 2012, 134, 2589) that selective N-terminal functionalization can be achieved with the alkynyl ketene 7, which allows for subsequent derivitization of the acylated products (e.g., 8) via click reactions with azides. To formylate amines such as morpholine (9), an N-heterocyclic carbene (e.g., 10) catalyzed procedure that utilizes CO2 and polymethylhydrosiloxane (PMHS) has been developed (J. Am. Chem. Soc. 2012, 134, 2934) by Thibault Cantat at the CEA in France. For the protection of acyclic amino acid derivatives, Eiji Tayama at Niigata University has reported (Tetrahedron Lett. 2012, 53, 1373) a new protecting group, 1,2-dimethoxy-4,5-dimethylene, that is installed by double alkylation and can be removed with, for example, ethyl chloroformate to produce the corresponding carbamate (e.g., 12 to 13). As far as protecting groups go, ethers can be especially challenging to remove; however, a new procedure for the oxidative cleavage of glycol ethers, including dioxane, has been developed (Org. Lett. 2012, 14, 3218) by Zhong-Quan Liu at Lanzhou University. This copper-catalyzed procedure employs carboxylic acids such as 14 and produces alkoxymethoxy esters 15. The cleavage of unactivated ethers such as dibutyl ether as a means to alkylate sulfonamides (cf. 16) has been reported (Synlett 2012, 595) by Wei Zeng at South China University of Technology. Protecting groups that are thermally labile offer the ability to achieve deprotection without added reagents. A new thermolabile protecting group has been developed (Tetrahedron Lett. 2012, 53, 666) by Marcin K. Chmielewski at the Polish Academy of Sciences based on 2-pyridyl-N-(2,4-difluorobenzyl)aminoethyl carbonates.
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Boobalan, Chitra, Sudha Ganesh i Parthiban Rangaswamy. "Analysis of Liquid Cooling in Microchannels Using Computational Fluid Dynamics (CFD)". W Heat Transfer - Design, Experimentation and Applications [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96248.
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Liquid cooling is an extremely successful process to remove excess heat generated, with the usual procedure of heat transfer using coolant in desktop PCs. In this regard, heat transfer with minimal size equipment can be achieved by the addition of nanosized solid particles to the base fluid. The hybrid nanofluid is synthesized by dispersing the synthesized mono nanofluid in a volume fraction of 0.2 iron oxide with 0.8 fractions of graphene nanofluid to form a graphene/iron oxide combination. These nanoparticles increase the heat transfer coefficient as they have high thermal conductivity when compared to conventional heat transfer fluids like water or ethylene glycol. Stability is increased and sedimentation is reduced because of the large surface area of a nanoparticle. FLUENT, the most widely used computational fluid dynamics (CFD) software package, based on the finite volume method, and is used to run the thermal simulations for estimating the base temperature of the heat sink. The scope of this chapter is to find the base temperature of the heat sink using simulations. The experimentally measured base temperature is 310.01 K and in the simulation, it is 310.81 K for the flow rate of 0.75LPM. All the simulated surface temperatures are compared with experimentally determined temperatures for simulation validation.
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Mahatmanti, F. W., E. Kusumastuti, W. D. P. Rengga, Nuryono i D. Siswanta. "Chitosan-silica- polyethylene Glycol (Ch/Si/P) Solid Membrane for Removal of Cu(II), Zn(II) and Cd(II) Ions from Aqueous Solutions". W Challenges and Advances in Chemical Science Vol. 1, 54–72. Book Publisher International (a part of SCIENCEDOMAIN International), 2021. http://dx.doi.org/10.9734/bpi/cacs/v1/8924d.
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Becker, Richard C., i Frederick A. Spencer. "Novel Anticoagulants". W Fibrinolytic and Antithrombotic Therapy. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780195155648.003.0023.
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While all anticoagulants have, to a certain extent, novel properties, the development of agents that inhibit specific coagulation proteases through structural affinity and can be inhibited themselves by the concomitant production of antidotes (drug–antidote pair construct) has the potential to revolutionize the field. With the evolution of our thinking toward hemostasis and thrombosis has come new pharmacologic constructs for safe and effective treatment. Aptamers are single-stranded nucleic acids that inhibit a protein’s function by folding into a specific three-dimensional structure that defines high-affinity binding to the target protein (White et al., 2000). The term aptamer (from the Latin aptus, “to fit”) was coined by Ellington and Szostak (1990) following their pioneering work published originally in Nature. Based on iterative selection techniques, aptamers that bind essentially any protein or small molecule can be generated. A high-affinity, specific inhibitor that interacts with functional groups (on both the nucleic acid and the protein) can be constructed if a small amount of pure target is available. The initiation point for aptamer development is a combinatorial library composed of single-stranded nucleic acids (RNA, DNA, or modified RNA), typically containing 20 to 40 randomized positions (1024 different sequences). Isolation of high-affinity nucleic acid ligands involves a process known as SELEX (systemic evolution of ligands by exponential enrichment). The starting library is incubated with the protein of interest. Nucleic acid molecules that adopt conformations that allow target protein binding are subsequently partitioned from other sequences (that do not bind the protein). The bound sequences are removed and amplified by reverse transcription and polymerase chain reaction (PCR) (for RNA-based libraries) or PCR alone (for DNA-based libraries). After repeating the process several times, the selected ligands are secured and evaluated for binding affinity and ability to inhibit activity (of the target protein). Postselection optimization steps typically include (1) reduction in aptamer length (from a starting molecule of 80–100 nucleotides to 40 nucleotides); (2) enhanced stability in biologic systems (achieved by substitution of ribonucleotides with 2-amino, 2´-fluoro, or 2´-0-alkyl nucleotides and protection from exonuclease digestion by 3´ end capping); and (3) reduced renal clearance (achieved by increasing the molecules’ mo lecular weight through site-specific addition of polyethylene glycol moieties or other hydrophobic groups.
Streszczenia konferencji na temat "Glycan Removal"
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Sharmin, Khurshida, i Ingmar Schoegl. "Processing and Analysis of Ceramic Mesoscale Combustors Fabricated by Co-Extrusion". W ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-64866.
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In this work, millimeter-scale tubular combustion channels were fabricated from ceramic precursor materials. Co-extrusion of structured feedrods holds promise for the development of multi-layered, functionally graded and/or textured combustor walls, but requires a polymer binder that is difficult to remove before structures can be sintered to full density. In conventional thermal debinding, cracking is a major issue, where crack formation is attributed to a lack of pore space for outgassing of pyrolysis products. The main focus of this study is to validate a manufacturing process that uses a combination of solvent de-binding and thermal debinding, which is applied to a simple combustor geometry. Alumina powder was batched with a mixture of polyethylene butyl-acrylate (PEBA) and polyethylene glycol (PEG) in a torque rheometer. A 19mm feedrod, consisting of a carbon-black/binder mixture as core, and a surrounding ceramic/binder mixture forming the wall, was extruded through a 5.84 mm die. The binder removal involves two processing steps, where the PEG content was removed by solvent extraction (SE) to initiate pore formation, after which thermal de-binding by pyrolysis removes the remaining binder and carbon-black. Solvent extraction was performed in water at three different temperatures for various times. The 1:1 mixture of PEG:PEBA showed the highest PEG removal of 80wt% for 6 hrs extraction. The thermal de-binding cycle was designed based on thermo-gravimetric analysis (TGA) and successfully performed with a ramping rate of 1.25°C/min to 1000°C without any crack formation. After de-binding, samples were sintered at 1600°C for 1 hr. SEM analysis showed some void spaces in the solvent extracted samples but confirmed that solvent extraction followed by thermal de-binding yielded the best results. The viability of sintered ceramic tubes was tested for conditions typical for thermal cycling in a combustion environment.
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Liu, Qisong, Hang Song, Jiang Li i Shun Yao. "Glycin Modification of Spherical Cellulose for Chromium Ions Removal from Wastewater". W 2010 4th International Conference on Bioinformatics and Biomedical Engineering (iCBBE). IEEE, 2010. http://dx.doi.org/10.1109/icbbe.2010.5518187.
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Mozaffar, Houra, Tore Larsen, Chris Henderson, Salim Deshmukh, Ross Anderson, Mohsen Hoopanah, Bahman Tohidi, Emilie Abadie, Vanessa Richon i Mark Charlesworth. "Multiple Recovery and Re-Use of Commercial Kinetic Hydrate Inhibitors from Produced Water and Rich Glycol". W International Petroleum Technology Conference. IPTC, 2022. http://dx.doi.org/10.2523/iptc-22399-ea.
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Abstract Kinetic hydrate inhibitors (KHIs) offer an alternative to traditional thermodynamic hydrate inhibitors (THIs) for the prevention of gas hydrates. KHIs have several advantages over THIs, such as lower required volumes, easier logistics and reduced CAPEX. However, KHIs are once through chemicals leading to increased OPEX, are mostly non-biodegradable and therefore cannot be discharged to sea or disposal wells in fear of aquifer pollution. KHIs can also lead to fouling of process equipment, especially at elevated temperatures. To resolve these issues, a new KHI polymer removal method using a solvent extraction-based technique has been developed. In this approach, an immiscible extraction fluid is mixed into the KHI containing aqueous phase where the KHI polymer partitions into the extraction fluid, which can then be separated from the aqueous phase. In some cases, the KHI separated this way can be re-used. This process has the potential to solve problems with KHI produced water treatment/disposal, including where KHI is used in combination with MEG, reducing the costs and process fouling and protecting the environment. A new joint industry project (JIP) is underway with the aim of developing the concept into a commercial process for removal and possible re-use of KHIs upstream of PW treatment or MEG Regeneration systems. The first phase of this project is lab scale evaluation of the solvent extraction method for simulated removal and re-use of two commercial KHI formulations for a real gas-condensate field case. Both the removal efficiency and hydrate inhibition performance of 4 cycles of re-injected/re-used KHI has been successfully demonstrated. Removal of KHI from a real MEG system case was also successfully demonstrated. In the second phase of the JIP, lab scale tests were used to screen extraction and separation equipment and identify optimum process conditions. The upcoming third phase of this JIP is dedicated to demonstrating the selected process concept(s) on pilot scale in a flow loop. In this proceeding we will give highlights of the early laboratory test results from a produced water case where two field qualified KHIs are removed from PW and reused 4 times, still showing adequate hydrate inhibition performance. Successful pilot tests will confirm the operability of this process in the field.
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Lehmann, Marc, Katerina Lepkova, Thunyaluk Pojtanabuntoeng, Varun Ghodkay, Annamaria Greenwood, Susumu Hirano i Toshiyuki Sunaba. "Use of Oxygen Scavenger in Well Safety Valve Balancing Operations". W Offshore Technology Conference Asia. OTC, 2022. http://dx.doi.org/10.4043/31509-ms.
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Abstract Monoethylene glycol (MEG) is often used to reduce the differential pressure across well valves so that they can be opened without damage. This MEG ultimately commingles with production fluids and if not deoxygenated contributes to the overall content of dissolved oxygen that may be seen by a receiving production facility. Normally, the dissolved oxygen levels would be removed to insignificant levels during fluid transport. Since the corrosion reactions sequester the oxygen as the fluids are exposed to less noble materials of construction, such as carbon steel. However, in facilities that utilise corrosion resistant alloys (CRA) the residual dissolved oxygen level can be so significant that it warrants reduction using oxygen scavengers. This paper reports on corrosion studies that illustrate the consequence of dissolved oxygen levels being carried through to a MEG reclamation unit constructed of CRA, and laboratory and field validation studies on the use of a bisulfite-based scavenger for removal of oxygen in 90wt% MEG used for equalising pressure of Subsurface Safety Valves.
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Bonifas, A. M., E. J. Taylor i J. J. Sun. "Industrial Applications of Advanced Electrochemical Finishing Techniques". W ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-61656.
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Faraday Technology, Inc. has developed electrochemical techniques for the edge and surface finishing of advanced materials, such as titanium alloys, stainless steels, and nickel based superalloys. This technology employs electrochemical metal removal under the influence of a bipolar, pulsed electric field to provide enhanced process control and excellent surface finishes. This process achieves high rates of metal removal in the presence of simple chemistries that are pH neutral, water based, non-toxic, and environmentally benign. This is in contrast to competing technologies that rely on electrolytes that are comprised of concentrated acids or ethylene glycol. This paper will present Faraday’s recent development efforts in a wide variety of industries, including the semiconductor, automotive, and medical industries.
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Ekoue-Kovi, Kekeli, Sankaran Murugesan, Onome Ugono, Sai Pinappu i Jerry Weers. "Novel Environmentally Responsible Solvents for Sulfur Removal in Oil and Gas Applications". W SPE International Conference on Oilfield Chemistry. SPE, 2023. http://dx.doi.org/10.2118/213824-ms.
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Abstract The removal of unreactive or non-acidic sulfur species to meet fuel specifications remains a challenge in the oil and gas industry. This is especially the case with the recent introduction of IMO 2020 restrictions in the use of marine fuels to those that have sulfur contents from 3.5% down to 0.5%. This has led refiners to seek alternative sulfur removal technologies that can be used in addition to the conventional desulfurization process. Formulations of cyclic organic carbonates (COCs) were developed in combinations with environmentally friendly lactones and glycol ethers and are shown to facilitate the removal of unreactive organosulfur compounds such as thiophenes, disulfides and mercaptans. This study utilizes different sulfur-containing hydrocarbon streams consisting of crude oil, heavy hydrocarbon (fuel oil), lighter hydrocarbon, naphtha from various refineries and field operations. Model hydrocarbon blends were prepared by dosing with different sulfur compounds and analyzed for sulfur removal efficiency using COC formulations. The use of sulfur containing heavy hydrocarbons from the field were also assessed to demonstrated that the sulfur removal was applicable to a wide range of hydrocarbons. Furthermore, a process for the recovery and reuse of solvent was developed to extend the lifetime of the solvent and reduce the cost of operations. The regenerated solvent shows extended efficiency and the process for its regeneration, recycle and reuse offers many advantages. The newly developed solvent formulation showed enhanced performance over caustic or other specialty chemistries by 30-100% depending on the nature of the sulfur species.
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Habib, B. A., i M. M. Farid. "Heat Transfer Studies on Freeze Concentration of Salt Brines in a Liquid Solid Fluidized Bed Heat Exchanger". W ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56798.
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Fluidized bed freeze concentration is a technology in which liquid solutions can be concentrated within a fluidized bed heat exchanger by preferential freezing of water out of the solution. Water forms an ice layer on the heat exchanger wall from where it is removed by the action of the fluidized bed on it. A double pipe fluidized bed heat exchanger was constructed which included a bed of 4×4 mm 304 stainless steel solid cylinders. Salt solutions (0–9.4 wt%) were used in the process to form ice, which could successfully be removed by the particles with bed porosity of 0.81–0.83. Freeze concentration effects were observed with continuous freezing point depression in these experiments. Coolants used in experiments were 34% ethylene glycol solution and a potassium formate solution. The respective overall heat transfer coefficients were ∼600 W/m2K with ethylene glycol and ∼1000 W/m2K with potassium formate solution (Tyfoxit).
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Hubel, A., N. Bidault i B. Hammer. "Transport Characteristics of Glycerol and Propylene Glycol in an Engineered Dermal Replacement". W ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32557.
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The ability to cryopreserve engineered tissues is important for the clinical application of therapies based on living cells. Cryopreservation facilitates the manufacture, transport and safety of cell-based therapies. The cryopreservation of cells and tissues had typically required the use of specialized solutions containing cryoprotective agents (CPAs). The addition of a CPA to the freezing solution may result in damage if it is not done properly. Tissues and intact organs can exhibit reduced cellular viability when exposed to sufficiently large step changes in external osmolarity resulting from introduction or removal of a cryopreservation solution (Pegg, 1972). Not only are large step changes in osmolarity potentially damaging, but also long-term exposure to even low concentrations of CPAs at room temperature can be lethal (Fahy et al., 1990). Exposure of cells to CPAs (in particular dimethyl sulfoxide, Me2SO) has been associated with a loss in viability with time of exposure. Subsequent studies have quantified specific cellular changes resulting from exposure to CPA, such as cytoskeletal reorganization, cross-linking of nuclear proteins, and alterations in membrane permeability (cf. ref (Fahy et al., 1990) for review) which may account for the loss in viability.
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Thiel, E., i K. H. Drexhage. "CW dye laser operation at very low flow velocities". W The European Conference on Lasers and Electro-Optics. Washington, D.C.: Optica Publishing Group, 1994. http://dx.doi.org/10.1364/cleo_europe.1994.ctuk63.
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Until now cw dye laser action has been observed only when the dye solution flows very fast (10 m/s) through the active region. This is realized mostly by using the jet stream technique. Two reasons for the demand of fast dye flow are generally accepted: first, reduction of thermal disturbances and second, mechanical quenching of the lowest triplet state of the dye molecules. A frequently used and high efficient laser dye solution is Rhodamine 6G in ethylene glycol. Employing a new spectroscopic method, we measured a triplet state lifetime of 5 µsec in air-saturated solution at room temperature.1 This is to be compared with the dye molecules, flight time through the active region of a typical cw dye laser. This time is about 2µs. Therefore, owing to the motion of the jet, the triplet state population in the active region is reduced sufficiently so that laser action becomes possible. Moreover it was concluded from the triplet data of Rhodamine 6G1 that no optical gain can be expected in ethylene glycol without mechanical removal of triplet molecules.
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Felix, S., K. Shah, D. George, V. Tolosa, A. Tooker, H. Sheth, T. Delima i S. Pannu. "Removable silicon insertion stiffeners for neural probes using polyethylene glycol as a biodissolvable adhesive". W 2012 34th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC). IEEE, 2012. http://dx.doi.org/10.1109/embc.2012.6346070.
Pełny tekst źródłaRaporty organizacyjne na temat "Glycan Removal"
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Yan. PR-261-123602-R01 Evaluation of the Corrosiveness of Glycol-Water Mixtures in Dry Gas Transmission Lines. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), maj 2013. http://dx.doi.org/10.55274/r0010009.
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This report provides a review of the state-of-the-art knowledge on glycol-water mixtures carried over to dry gas transmission pipelines, i.e., physical properties, the causes of entry, and the corrosiveness. Findings obtained from literature include: Glycol-water mixtures can be potentially accumulated in dry gas transmission pipelines. Operation conditions of the dehydration unit should be optimized to control the amount and corrosiveness of glycol-water being carried over into transmission lines. The glycol-water hold-up in dry gas transmission pipelines contain high glycol content, i.e., greater than 95%. The accumulated glycol-water requires removal by direct drain from liquid traps, or by pigging either with methanol or water. For transmission pipelines transporting natural gas containing CO2, the most likely corrosion mechanism associated with glycol-water mixtures is general corrosion. The corrosion rate has been proven to be low, i.e., much lower than 0.1mm/year. For sour gas transmission pipelines, although general corrosion has been ruled out as a major concern, localized corrosion and HIC can occur in glycol-water mixtures. The rate of localized corrosion and HIC remains undefined. The list of recommendations to minimize the amount of glycol-water mixtures being carried over to dry gas transmission lines and to reduce the corrosion risks is developed. More research is required to study the potential corrosion mechanisms, i.e., pitting and HIC, of pipeline steels in glycol-water mixtures with high glycol content ( greater than 95%) under sour gas conditions.
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Browdy, Craig, i Esther Lubzens. Cryopreservation of Penaeid Shrimp Embryos: Development of a Germplasm Cryo-Bank for Preservation of High Health and Genetically Improved Stocks. United States Department of Agriculture, sierpień 2002. http://dx.doi.org/10.32747/2002.7695849.bard.
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The objectives of the project were to develop a successful protocol for cryopreservation of penaeid germ plasm in order to preserve a pathogen-free broodstock nucleus for commercial exploitation of marine shrimp in aquaculture. The critical parameters to be characterized in the project were: 1. Determination of chill sensitivity and chill tolerant embryonic stages, including a full description and time course study of embryonic developmental stages. 2. Development of protocols for loading and removal of cryoprotectant agents (CPAs) from embryos; determination of optimal concentrations and duration of loading. 3. Characterization of the toxicity of the selected CP As and 4. Establishing optimal cooling and thawing procedures. Studies were performed on two penaeid species: Litopenaeus vannamei (in the USA) and P. semisulcatus (in Israel). The effect of incubation temperature on embryonic development rate and hatching success was studied in L. vannamei, showing that spawns maybe maintained at temperatures ranging from 24°C to 30°C, without compromising hatchability. Embryonic development extends from 12 hr to 19 hr at 30°C and 24°C, respectively. Studies showed that advanced embryonic developmental stages were chill tolerant in the two studied species, but P. semisulcatus could better endure lower temperatures than L. vannamei. A large number of experiments were performed to determine the optimal CP As, their concentration and duration of loading. Permeating (e.g. glycerol, methanol, DMSO, 1,2- propanediol, ethylene glycol, glucose) and non-permeating CPAs (sucrose, PVP, polyethylene glycol) were tested and several combinations of permeating and non-permeating CP As, on fertilized eggs (embryos), nauplii and protozoeae. In general, nauplii tolerated higher CPA concentrations than eggs and nauplii were also more permeable to radiolabeled methanol. Chlorine treatment intended to remove the chitinous envelop from eggs, did not increase dramatically the permeation of radiolabled methanol into eggs. Cooling eggs, nauplii or protozoeae to cryogenic temperatures, by either vitrification or slow cooling protocols, did not result in full survival of thawed samples, despite exhaustive attempts testing various protocols and CP As. Results seemed more encouraging in freezing of nauplii in comparison to eggs or protozoeae. Successful preliminary results in cryopreservation of spermatozoa of P. vannamei, will facilitate preservation of genetic specific to some extent.