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Letteratura scientifica selezionata sul tema "Chemical affinity"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 29 luglio 2024

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Articoli di riviste sul tema "Chemical affinity"

Košíková, Božena, Elena Sláviková e Juraj Lábaj. "Affinity of lignin preparations towards genotoxic compounds". BioResources 4, n. 1 (17 novembre 2008): 72–79. http://dx.doi.org/10.15376/biores.4.1.72-79.

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The carcinogenicity and mutagenicity of chemicals may be modulated by other chemicals, including those prepared by organic synthesis. Considering the several drawbacks of synthetic compounds vis-a-vis the human organism, the lignin biomass component was examined for this purpose. The binding affinity of lignin samples prepared by chemical and biological modification of lignin products derived from chemical wood treatment towards for N-nitrosodiethylamine (NDA) was examined. The protective role of the lignin samples against carcinogenesis was tested on a well-known model carcinogen, N-methyl-N´-nitro-N-nitrosoguanidine (MNNG). The observed ability of a series of lignin preparations to reduce alkylation damage of deoxyribonucleic acid (DNA) on hamster cells in vitro could be explained by their affinity to bind N-nitrosoamines. The results indicate that lignin has potential to protect living organisms against damaging effects of different genotoxicants.

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Kauvar, Lawrence M., Hugo O. Villar, J. Richard Sportsman, Deborah L. Higgins e Donald E. Schmidt. "Protein affinity map of chemical space". Journal of Chromatography B: Biomedical Sciences and Applications 715, n. 1 (settembre 1998): 93–102. http://dx.doi.org/10.1016/s0378-4347(98)00045-0.

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PARIKH, INDU, e PEDRO CUATRECASAS. "AFFINITY CHROMATOGRAPHY". Chemical & Engineering News 63, n. 34 (26 agosto 1985): 17–32. http://dx.doi.org/10.1021/cen-v063n034.p017.

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Ohno, K., Y. Inoue e M. Sakurai. "Quantum Chemical Study of Antibody Affinity Maturation". Seibutsu Butsuri 43, supplement (2003): S50. http://dx.doi.org/10.2142/biophys.43.s50_4.

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Alcantara, R. E., C. Xu, T. G. Spiro e V. Guallar. "A quantum-chemical picture of hemoglobin affinity". Proceedings of the National Academy of Sciences 104, n. 47 (14 novembre 2007): 18451–55. http://dx.doi.org/10.1073/pnas.0706026104.

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Hornung, M. W., M. A. Tapper, J. S. Denny, R. C. Kolanczyk, B. R. Sheedy, P. C. Hartig, H. Aladjov, T. R. Henry e P. K. Schmieder. "Effects-based chemical category approach for prioritization of low affinity estrogenic chemicals". SAR and QSAR in Environmental Research 25, n. 4 (3 aprile 2014): 289–323. http://dx.doi.org/10.1080/1062936x.2014.898692.

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Schmieder, P., Ovanes Mekenyan, Steven Bradbury e G. Veith. "QSAR prioritization of chemical inventories for endocrine disruptor testing". Pure and Applied Chemistry 75, n. 11-12 (1 gennaio 2003): 2389–96. http://dx.doi.org/10.1351/pac200375112389.

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Binding affinity between chemicals and the estrogen receptor (ER) serves as an indicator of the potential to cause endocrine disruption through this receptor-mediated endocrine pathway. Estimating ER-binding affinity is, therefore, one strategic approach to reducing the costs of screening chemicals for potential risks of endocrine disruption. While measuring ER binding with in vitro assays may be the first choice in prioritizing chemicals for additional in vitro or in vivo estrogenicity testing, the time and costs associated with screening thousands of chemicals is prohibitive. Recent advances in 3D modeling of the reactivity of flexible structures make in silico methods for estimating ER binding possible. One technique, the common reactivity pattern (COREPA) approach, was applied to development of reactivity patterns for ER relative binding affinity based on global nucleophilicity, interatomic distances between nucleophilic sites, and local electron donor capability of the nucleophilic sites. The reactivity patterns provided descriptor profiles for order-of-magnitude RBA ranges of training set chemicals. An exploratory expert system was subsequently developed to predict RBA and rank chemicals with respect to potential estrogenicity. A strategy is presented for extending initial exploratory 3D QSAR models beyond current training sets to increase applicability to more diverse structures in large chemical inventories.

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Freidin, A. B. "On the chemical affinity tensor for chemical reactions in deformable materials". Mechanics of Solids 50, n. 3 (maggio 2015): 260–85. http://dx.doi.org/10.3103/s0025654415030048.

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Nayarisseri, Anuraj. "Experimental and Computational Approaches to Improve Binding Affinity in Chemical Biology and Drug Discovery". Current Topics in Medicinal Chemistry 20, n. 19 (14 settembre 2020): 1651–60. http://dx.doi.org/10.2174/156802662019200701164759.

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Drug discovery is one of the most complicated processes and establishment of a single drug may require multidisciplinary attempts to design efficient and commercially viable drugs. The main purpose of drug design is to identify a chemical compound or inhibitor that can bind to an active site of a specific cavity on a target protein. The traditional drug design methods involved various experimental based approaches including random screening of chemicals found in nature or can be synthesized directly in chemical laboratories. Except for the long cycle design and time, high cost is also the major issue of concern. Modernized computer-based algorithm including structure-based drug design has accelerated the drug design and discovery process adequately. Surprisingly from the past decade remarkable progress has been made concerned with all area of drug design and discovery. CADD (Computer Aided Drug Designing) based tools shorten the conventional cycle size and also generate chemically more stable and worthy compounds and hence reduce the drug discovery cost. This special edition of editorial comprises the combination of seven research and review articles set emphasis especially on the computational approaches along with the experimental approaches using a chemical synthesizing for the binding affinity in chemical biology and discovery as a salient used in de-novo drug designing. This set of articles exfoliates the role that systems biology and the evaluation of ligand affinity in drug design and discovery for the future.

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Nowak, Damian, Rafał Adam Bachorz e Marcin Hoffmann. "Neural Networks in the Design of Molecules with Affinity to Selected Protein Domains". International Journal of Molecular Sciences 24, n. 2 (16 gennaio 2023): 1762. http://dx.doi.org/10.3390/ijms24021762.

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Drug design with machine learning support can speed up new drug discoveries. While current databases of known compounds are smaller in magnitude (approximately 108), the number of small drug-like molecules is estimated to be between 1023 and 1060. The use of molecular docking algorithms can help in new drug development by sieving out the worst drug-receptor complexes. New chemical spaces can be efficiently searched with the application of artificial intelligence. From that, new structures can be proposed. The research proposed aims to create new chemical structures supported by a deep neural network that will possess an affinity to the selected protein domains. Transferring chemical structures into SELFIES codes helped us pass chemical information to a neural network. On the basis of vectorized SELFIES, new chemical structures can be created. With the use of the created neural network, novel compounds that are chemically sensible can be generated. Newly created chemical structures are sieved by the quantitative estimation of the drug-likeness descriptor, Lipinski’s rule of 5, and the synthetic Bayesian accessibility classifier score. The affinity to selected protein domains was verified with the use of the AutoDock tool. As per the results, we obtained the structures that possess an affinity to the selected protein domains, namely PDB IDs 7NPC, 7NP5, and 7KXD.

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Più fonti

Tesi sul tema "Chemical affinity"

Lindgren, Joel. "Chemical Engineering of Small Affinity Proteins". Doctoral thesis, KTH, Proteinteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-141014.

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Small robust affinity proteins have shown great potential for use in therapy, in vivo diagnostics, and various biotechnological applications. However, the affinity proteins often need to be modified or functionalized to be successful in many of these applications. The use of chemical synthesis for the production of the proteins can allow for site-directed functionalization not achievable by recombinant routes, including incorporation of unnatural building blocks. This thesis focuses on chemical engineering of Affibody molecules and an albumin binding domain (ABD), which both are three-helix bundle proteins of 58 and 46 amino acids, respectively, possible to synthesize using solid phase peptide synthesis (SPPS). In the first project, an alternative synthetic route for Affibody molecules using a fragment condensation approach was investigated. This was achieved by using native chemical ligation (NCL) for the condensation reaction, yielding a native peptide bond at the site of ligation. The constant third helix of Affibody molecules enables a combinatorial approach for the preparation of a panel of different Affibody molecules, demonstrated by the synthesis of three different Affibody molecules using the same helix 3 (paper I). In the next two projects, an Affibody molecule targeting the amyloid-beta peptide, involved in Alzheimer’s disease, was engineered. Initially the N-terminus of the Affibody molecule was shortened resulting in a considerably higher synthetic yield and higher binding affinity to the target peptide (paper II). This improved variant of the Affibody molecule was then further engineered in the next project, where a fluorescently silent variant was developed and successfully used as a tool to lock the amyloid-beta peptide in a β-hairpin conformation during studies of copper binding using fluorescence spectroscopy (paper III). In the last two projects, synthetic variants of ABD, interesting for use as in vivo half-life extending partners to therapeutic proteins, were engineered. In the first project the possibility to covalently link a bioactive peptide, GLP-1, to the domain was investigated. This was achieved by site-specific thioether bridge-mediated cross-linking of the molecules via a polyethylene glycol (PEG)-based spacer. The conjugate showed retained high binding affinity to human serum albumin (HSA) and a biological activity comparable to a reference GLP-1 peptide (paper IV). In the last project, the possibility to increase the proteolytic stability of ABD through intramolecular cross-linking, to facilitate its use in e.g. oral drug delivery applications, was investigated. A tethered variant of ABD showed increased thermal stability and a considerably higher proteolytic stability towards pepsin, trypsin and chymotrypsin, three important proteases found in the gastrointestinal (GI) tract (paper V). Taken together, the work presented in this thesis illustrates the potential of using chemical synthesis approaches in protein engineering.

QC 20140207

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Zourna, Kalliopi. "Smart magnetic affinity adsorbents". Thesis, University of Birmingham, 2009. http://etheses.bham.ac.uk//id/eprint/511/.

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As the focus of research on ‘adaptive/responsive’ surfaces has in recent years contributed strongly towards the design of surface materials with ‘intelligent’ or ‘smart’ behaviour, current superparamagnetic adsorbents being employed both in small and large scale operations can be surface modified and improved by gaining dual functionalities. In this work, modification of M-PVA supports with polymer brushes of dual properties has been explored for their intended use in bioseparation technology, i.e. for both selectively protein binding and enhanced temperature elution of especially difficult to elute species such as haemoglobin. Tethering of polymer brushes was achieved by employing two different ‘grafting from’ routes, i.e. cerium (IV) initiated polymerisation and Atom Transfer Polymerisation Reaction (ATRP). By identifying the optimum cerium (IV) reaction conditions, the said chemistry was further utilised to attach different polymers (thermoresponsive and affinity ligands) and their combination (thermo-affinity) at fixed positions onto M-PVA supports, either as di-block or mixed functionality polymer brushes. The configuration of introduced polymer chains as well as the haemoglobin binding characteristics of the above materials was evaluated, and their efficiency for haemoglobin and GFP desorption via sequential temperature transitions was demonstrated. Mixed polymer brushes manufactured using sequential ATRP after partial bromination of AGE activated magnetic supports were characterised and tested likewise. Protein binding and release efficiency was dependent on brush configuration (length and spacing between the graft sites of polymers), pNIPAAm content, type of affinity ligand and type of protein employed. From the above materials those with polymer chains of sufficient pNIPAAm length and at such spacing allowing their ‘free’ expansion/collapse upon temperature change (especially those grafted via cerium (IV) route) were found efficient, as brush behaviour favour enhanced desorption of difficult to elute species.

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Beard, Hester Annie. "Affinity-guided chemical probes for the study of protein interactions". Thesis, University of Leeds, 2018. http://etheses.whiterose.ac.uk/20637/.

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Chemical methods that allow for the targeted labelling of a specific protein within a complex biological environment can enable valuable information regarding the structure and function of proteins to be gained. This thesis explores two different projects where affinity-guided chemical probes were used to study the interactions of proteins, both with small molecules (Chapter 2) and interacting protein partners (Chapter 3). Firstly, chemical labelling methods based on a recognition unit for the protein of interest are reviewed in Chapter 1. Then, Chapter 2 describes how a combination of chemical tools (including photoaffinity, biotinylated and fluorescent probes) were used to study the interaction of a small molecule inducer of human glioblastoma cell death and its relevant target. This work resulted in the identification of HSPD1 as a potential therapeutic target for the treatment of glioblastoma. Chapter 3 details the development of a method for traceless labelling of B-cell lymphoma 2 (BCL-2) family proteins, using a ruthenium-bipyridyl modified peptide. Myeloid cell leukaemia 1 (MCL-1) was rapidly and selectively labelled with fluorescent and biotinylated tags, in vitro, facilitated by the interaction with a peptide mimicking a binding partner. Overall, this thesis demonstrates how affinity-guided labelling of proteins can be used for understanding molecular mechanisms of disease and mapping protein interactomes.

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Tarasova, Anna Optometry UNSW. "Fabrication and characterisation of affinity-bound liposomes". Awarded by:University of New South Wales. Optometry, 2007. http://handle.unsw.edu.au/1959.4/29114.

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In considering the concept of surface-immobilised liposomes as a drug release system, two factors need to addressed, the interfacial surface density of the liposomes for maximum drug loading and the stability of these liposomes to allow for controlled drug release. This thesis investigates a multilayer system for the affinity immobilisation of liposomes and their stability to various applied stresses. In the work presented here an allylamine monomer was used to create plasma coatings that were stable, thin and amine-rich. The aging studies using AFM showed these films to rapidly oxidise on exposure to water. The freshly deposited films were used for further surface modifications, by the covalent grafting of PEG layers of different interfacial densities under the conditions of varying polymer solvation. The AFM was used to measure the interaction forces between the grafted PEG layers and modified silica interfaces. It was found that the polydispersity of the PEG species resulted in bridging interactions of ???brush???-like PEG layers with the silica surface. These interactions were screened minimised by increasing the ionic strength of the solution. Although the densely grafted PEG layers were found to be highly protein-resistant by the XPS and QCM-D some minor protein-polymer adhesions were observed by the AFM. The densely anchored biotinylated PEG chains served as an optimum affinity platform for affinity-docking of NeutrAvidinTM molecules, which assembled in a rigid, 2-D layer as confirmed by the QCM-D. The submonolayer surface density of NeutrAvidin, as determined by Europium-labelling, was attributed to steric hindrance of the immobilised molecules. The final protein layer enabled specific binding of biotin-PEG-liposomes as a highly dissipative, dense and stable layer verified by tapping mode AFM and QCM-D. We found that these liposomes were also stable under a range of stresses induced by the shearing effects of water, silica probe and HSA layer at increased loads and velocities. The frictional response of the liposome layer also demonstrated the viscoelasticity and stability of these surface immobilised liposomes. Finally, the minimal adhesive interaction forces, as measured by the AFM, demonstrated the repellency of these liposomes to commonly found proteins, such as HSA.

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Zulqarnain, Kamran. "Scale-up of affinity separation based on magnetic support particles". Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313426.

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Stewart, David Johnston. "Immobilisation of triazine dyes on inert hydrophobic supports for affinity chromatography". Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315974.

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Miller, Eric Alexander. "Development of thermostable affinity reagents for low-cost, paper-based medical diagnostics". Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122849.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references.
The timely diagnosis and treatment of disease in resource-constrained settings requires the development of robust point-of-care (POC) diagnostics, which provide accurate results and can be employed by users with minimal medical training and limited access to basic infrastructure. One of the most common POC diagnostic formats is the immunochromatographic rapid diagnostic test, which traditionally uses nitrocellulose-immobilized IgG antibodies as binding proteins for the capture of disease biomarkers from patient samples. However, these antibodies are expensive to produce and structurally complex, and are prone to thermal denaturation. In contexts where continuous cold chain storage may be infeasible, the resulting loss in binding activity can manifest as diminished assay sensitivity, leading to adverse clinical outcomes and eroding patient trust in the diagnostic format.
In the interest of replacing diagnostic antibodies with a more cost-effective, robust class of binding proteins, this thesis explores the development of thermostable affinity reagents based on the hyperthermophilic scaffold protein rcSso7d. Given its native microbial host, minimalist structure, and high wild-type melting temperature (98°C), rcSso7d represents a viable alternative to antibodies in in vitro POC assays. To assess the applicability of the rcSso7d scaffold in this context, protein engineering techniques were used to rapidly select analyte-specific binding variants from a yeast surface display library of >109 members. A high-affinity rcSso7d binder was identified, produced in high yield in a bacterial host, and readily purified in a single chromatographic step.
The in vitro activity and thermal stability of this engineered binder were characterized in the context of a low-cost, paper-based assay, and significant improvements in stability and production economics were observed for rcSso7d-based assays, relative to assays featuring a representative antibody reagent. Additionally, general strategies were developed to improve the diagnostic performance of paper-based assays employing rcSso7d-based reagents. In one instance, chimeric protein constructs in which rcSso7d variants are fused to a cellulose-binding domain were found to bind to unmodified cellulose in an oriented fashion and with high efficiency. This substrate anchoring approach permits the rapid, high-density immobilization of the rcSso7d species in paper-based assays, and yields significant sensitivity enhancement by enabling both the depletion of the soluble analyte from the sample, and the processing of large sample volumes within clinically relevant timescales.
Detection reagents incorporating rcSso7d binders were also developed, using novel fusion constructs which enabled in vivo labelling while preserving analyte binding activity. These techniques were applied in the context of a urine-based tuberculosis biomarker, and may one day permit the development of multiplexed assays targeting a suite of these analytes. Such a development would enable point-of-care diagnostic testing without requiring the production of sputa, facilitating disease detection in otherwise inaccessible patient populations (e.g. children under five, the elderly, and immunocompromised patients).
"People who have financially supported this thesis: the NIH Biotechnology Training Program, the Tata Center for Technology and Design, the Deshpande Center, the Sandbox program, and the Singapore- MIT Alliance for Research and Technology"
by Eric Alexander Miller.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Chemical Engineering

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Hsu, Kuang-Hsin. "Scale-up of affinity chromatography for protein purifications". Ohio : Ohio University, 2000. http://www.ohiolink.edu/etd/view.cgi?ohiou1172002240.

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Lam, Hei Ning Henry. "Electrostatic and affinity enhancements of protein partitioning in two-phase aqueous micellar systems". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33700.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2005.
Includes bibliographical references (p. 175-188).
This thesis was motivated by the practical need to develop a scalable and cost-effective separation method for low-cost, high-volume protein products. This unmet challenge can potentially be addressed by extraction in two-phase aqueous micellar systems, in which biomolecules can be partitioned in mild, predominantly aqueous environments. The goal of this thesis was to explore various ways of enhancing protein partitioning in two-phase aqueous micellar systems, by the incorporation of electrostatic and affinity interactions, to obtain satisfactory yield and specificity for the purification of industrially relevant hydrophilic proteins. The electrostatically-enhanced partitioning of the enzyme glucose-6-phosphate dehydrogenase (G6PD) in two-phase aqueous mixed (nonionic/cationic) micellar systems was investigated experimentally and theoretically. The successful enhancement, up to 22-fold, of the partitioning of the negatively-charged G6PD was attained by adding the positively- charged surfactant alkyltrimethylammonium bromide (CnTAB) to form charged mixed micelles with the phase-forming nonionic surfactant, decyl tetra(ethylene oxide) (C₁₀E₄).
(cont.) The effects of the tail length of the positively-charged surfactant on protein denaturation and protein partitioning behavior were also studied. Furthermore, the experimental results were used to validate a predictive theory for electrostatic enhancement. In the area of affinity enhancement, the affinity-enhanced partitioning of an engineered affinity-tagged protein, CBM9-GFP (Green Fluorescent Protein linked to a carbohydrate- binding module), in two-phase aqueous micellar systems was investigated experimentally and theoretically. The experimental results showed that the partition coefficient of the target protein, CBM9-GFP, can be improved more than 6-fold, by virtue of the affinity interactions, and that the enhancement is specific to the target protein. The system utilized requires only one surfactant, decyl [beta]-D-glucopyranoside (C₁₀G₁), which acts simultaneously as the affinity ligand and as the phase-forming surfactant, and as such, has important practical advantages. A novel theoretical framework to describe affinity- enhanced protein partitioning in two-phase aqueous micellar systems was developed and validated experimentally. In addition, the separation method developed was successfully applied to a real cell lysate.
(cont.) It was found that the protein impurities in the cell lysate do not interfere with the partitioning of the target protein (CBM9-GFP) at industrially relevant concentrations, and that the protein impurities were concentrated away from the target protein. Lastly, the theoretical description developed was used to identify various strategies for improving the affinity-enhanced partitioning of the target protein in two-phase aqueous micellar systems. Although more work remains to be done before the separation methods studied in this thesis can reach their full potential and be eventually commercialized, this thesis nevertheless represents an essential starting point for future efforts to improve, extend, and commercialize this promising bioseparation method.
by Hei Ning Henry Lam.
Ph.D.

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Liebenberg, Liesl Eileen. "Non-covalent immobilisation of a ligand system : a new approach to affinity separation". Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53522.

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Thesis (MSc)--Stellenbosch University, 2003.
ENGLISH ABSTRACT: Advances in pharmacology, biochemistry and biotechnology are increasingly dependant upon affinity chromatography as a preferred separation technique for the purification and characterisation of specific biomolecules. In the past few years avidin-biotin technology has been widely and successfully used in the fields of medicine, pharmacy, biology and biochemistry. The avidin-biotin complex (ABC) has been used as a mediator for affinity chromatography, affinity cytochemistry, immunoassay, histopathology, bioaffinity sensors, erosslinking and immobilisation studies. The main reason for the popularity of the ABC and its growing usefulness in biotechnology is the exceptionally high affinity (1015 M-l) and stability of the noncovalent interaction between avidin and biotin. The use of the ABC is broadening as different biotin derivatives and avidin-containing conjugates are becoming commercially available. The aim of this work was to evaluate the usefulness of a plutonic" FI 08 and the ABC conjugate to effect affinity separation. Towards this aim, the adsorption of plutonic" F108 onto hydrophobic polysulphone membrane surfaces was studied. This information was used to determine the theoretical maximum amount of pluronic" FI08 that will adsorb onto a unit surface area of the membrane. It is known that the polypropylene oxide (PPO) centre block ofthe pluronic" F I08 surfactant molecule governs the concentration of pluronic" F I 08 molecules that will adsorb onto a given hydrophobic surface. If the maximum coating concentration of plutonic" FI08 is known, one can assume that the maximum coating concentration of any pluronic derivative, with the same PPO centre block size, will be the same. Adsorption studies were carried out, the Langmuir adsorption isotherm was determined, and subsequently the fractional coating was calculated. The end-groups of plutonic" FI08 were modified as follows and the substituted pluronic was adsorbed onto a membrane that was to act as the solid support matrix in the development of an affinity system: Amino pluronic was synthesised by first tosylating pluronic" FI08, followed by azidation with NaN3 then reduction with LiAI~. The synthesised amino pluronic was then biotinylated using N-hydroxysuccinimide biotin ester. The suitability of this synthetic route was first assessed on a model compound, 2-methoxyethylamine, and validated by NMR (Nuclear Magnetic Resonance) spectroscopy. The synthetic protocol was then used to derivatise the larger pluronic molecule. The affinity system was tested on two different hydrophobic surfaces: polystyrene and polysulphone membranes (PSMs). Avidin-conjugated horseradish peroxidase was obtained and used to interact with the immobilised biotin. The enzymatic reaction of the coupled peroxidase converted the substrate, 2, 2'-azino-di-(3-ethyl-benzthiazoline-6-sulphonic acid) (ABTS) to a coloured product. The colour developed is proportional to the amount of biotin that was immobilised on the hydrophobic surfaces studied. Non-covalent immobilisation of the synthesised biotin-pluronic molecule was successfully obtained onto the hydrophobic polystyrene as well as the polysulphone membrane surfaces.
AFRIKAANSE OPSOMMING: Vooruitgang in die farmakologie, biochemie en biotegnologie word al meer afhanklik van affiniteits chromatografie as die verkose tegniek vir die suiwering en karaterisering van spesifieke biomolekules. Oor die afgelope jare het die avidien-biotien tegnologie homself as baie bruikbaar bewys in die mediese, farmakologiese, biologiese en biochemiese velde. Toepassings waar die avidien-biotien kompleks betrokke was sluit in die toepassing as 'n mediator vir affiniteits chromatografie, affiniteits sitologie, immuno bepalings, histopatologie, bioaffiniteits sensors sowel as kruisbinding en immobiliserings studies en vele meer. Die hoofrede vir die gewildheid van die avidien-biotien kompleks en die groeiende bruikbaarheid in die biotegnologie is die buitengewone hoë affiniteit (l015 M-I ) en stabiliteit van die nie-kovalente interaksie tussen avidien en biotien. Die toepassingsveld van die avidien-biotien kompleks word wyer met die verskeidenheid biotien derivate en avidien-bevattende konjugate wat kommersiëel beskikbaar is. Die doel van die werk wat hier gedokumenteer word is om die bruikbaarheid van Plutonic" FI08 en die avidien-biotien kompleks, vir gebruik in 'n affiniteits chromatografie sisteem, te evalueer. Om hierdie doel te bereik is die adsorpsie van Pluronic" FI08 aan hidrofobiese polisulfoon membraan oppervlaktes bestudeer. Die eksperimentele data wat gegenireer is, is gebruik om die teoretiese maksimum hoeveelheid Pluronic wat per eenheids oppervlakte membraan adsorbeer te bepaal. Dit is reeds bekend dat die polipropileen (PPO) middel blok van die Pluronic emulgant die konsentrasie van die geadsorbeerde Pluronic molekules op 'n gegewe hidrofobiese oppervlakte bepaal. Indien die maksimum bedekkingskonsentrasie VIr maksimum oppervlakbedekking van Plutonic" FI08 bekend is, kan teoreties aanvaar word dat die bedekkingskonsentrasie vir enige Pluronic derivaat met dieselfde grootte PPO blok dieselfde sal wees. Adsorpsiestudies was uitgevoer om die Langmuir adsorpsie isoterm te bepaal. Daaropvolgend was die fraksionele bedekking bereken. Amino-pluronic was gesintetiseer deur die eindpunte van Pluronic te derivatiseer. Hierdie Pluronic derivaat was gevolglik geadsorbeer aan 'n membraan wat gedien het as die soliede oppervlakte vir die ontwikkeling van 'n affiniteits chromatografie sisteem. Amino-pluronic was gesintetiseer deur Pluronic eers te tosileer en daarna te asideer met NaN3 en laastens te reduseer met LiAI~. Die produk was gebiotinileer deur gebruik te maak van N-hidroksisuksinimied-biotien-ester. Die bruikbaarheid van hierdie sintetiese roete is eers bepaal deur van 'n model verbinding, 2-metoksiëtielamien, gebruik te maak en dit met behulp van KMR (Kern Magnetiese Resonans) spektroskopie te karakteriseer. Die affiniteits sisteem is getoets op twee verskillende hidrofobiese oppervlaktes naamlik polistireen en polisulfoon membraan oppervlaktes. Avidien gekonjugeerd met 'n peroksiedase ensiem is gebruik om met die geïmmobiliseerde biotien te assosieer. Die ensiematiese reaksie van die gekoppelde peroksiedase het die substraat 2, 2' -azino-di-(3-etiel-benzthiazolien-6-sulfoonsuur) (ABTS) omgesit na 'n gekleurde produk, waar dit teenwoordig is. 'n Reeks wasstappe is gebruik om die gemodifiseerde peroksidase ensiem wat nie aan die hidrofobiese oppervlakte gekoppel nie, weg te spoel. Hierdeur is die mate van binding aan die hirofobiese oppervlakte gekwantifiseer deur die kleur te kwantifiseer wat ontwikkelomdat die kleurontwikkeling direk proporsioneel is aan die hoeveelheid peroksidase wat nog aan die membraan gekoppel is. Nie-kovalente immobilisasie van die gesintetiseerde biotien-pluronic molekule is suksesvolop beide die hidrofobiese polistireen oppervlakte sowel as die polisulfoon membraan verkry.

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Libri sul tema "Chemical affinity"

Wrotnowski, Cort. Affinity technology. Norwalk, CT: Business Communications Co., 1991.

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Sadoun-Goupil, Michelle. Du flou au clair? Histoire de l'affinité chimique: De Cardan à Prigogine. Paris: Ed. du C.T.H.S., 1991.

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Sadoun-Goupil, Michelle. Du flou au clair?: Histoire de l'affinité chimique de Cardan à Prigogine. Paris: Éditions du C.T.H.S., 1991.

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Andrew, Kenney, e Fowell Susan, a cura di. Practical protein chromatography. Totowa, N.J: Humana Press, 1992.

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Tsukahara, Togo. Affinity and shinwa ryoku: Introduction of western chemical concepts in early nineteenth-century Japan. Amsterdam: J.C. Gieben, 1993.

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A, Olah George. Superelectrophiles and their chemistry. Hoboken, N.J: John Wiley, 2007.

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1964-, Yang Xueming, e Liu Kopin, a cura di. Modern trends in chemical reaction dynamics. Singapore: World Scientific, 2004.

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L, Krainsky I., e United States. National Aeronautics and Space Administration., a cura di. Negative electron affinity effect on the surface of chemical vapor deposited diamond polycrystalline films. [Washington, D.C: National Aeronautics and Space Administration, 1996.

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W, Ball David, e Lewis Research Center, a cura di. Theoretical and experimental determination of the proton affinity of (CF₃CH₂)₂O. [Cleveland, Ohio]: National Aeronautics and Space Administration, Lewis Research Center, 1998.

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Capitoli di libri sul tema "Chemical affinity"

Carredano, Enrique, e Herbert Baumann. "Affinity Ligands from Chemical Combinatorial Libraries". In Methods of Biochemical Analysis, 259–67. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2011. http://dx.doi.org/10.1002/9780470939932.ch10.

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de Berg, Kevin C. "The Reaction: Chemical Affinity and Controversy". In The Iron(III) Thiocyanate Reaction, 31–39. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-27316-3_4.

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Sato, Tsutomu. "Chemical Affinity in Kant’s Practical Philosophy". In Law and Peace in Kant’s Philosophy, 359–68. Berlin, New York: Walter de Gruyter, 2008. http://dx.doi.org/10.1515/9783110210347.3.359.

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Wang, Guangquan, Jeffrey R. Salm, Patrick V. Gurgel e Ruben G. Carbonell. "Small Peptide Ligands for Affinity Separations of Biological Molecules". In Chemical Engineering, 63–83. Chichester, UK: John Wiley & Sons, Ltd, 2005. http://dx.doi.org/10.1002/0470025018.ch3.

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Adamczewski, Martin, e Jean-Pierre Kinet. "The High-Affinity Receptor for Immunoglobulin E". In Chemical Immunology and Allergy, 173–90. Basel: KARGER, 1994. http://dx.doi.org/10.1159/000319254.

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Yatsimirsky, Anatoly K., e Vladimir M. Mirsky. "Quantitative Affinity Data on Selected Artificial Receptors". In Artificial Receptors for Chemical Sensors, 439–60. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2010. http://dx.doi.org/10.1002/9783527632480.ch14.

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Takayama, Hiroshi, Takashi Moriya e Naoki Kanoh. "Preparation of Photo-Cross-Linked Small Molecule Affinity Matrices for Affinity Selection of Protein Targets for Biologically Active Small Molecules". In Chemical Genomics and Proteomics, 75–83. Totowa, NJ: Humana Press, 2011. http://dx.doi.org/10.1007/978-1-61779-349-3_6.

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Mirsky, Vladimir M. "Quantitative Characterization of Affinity Properties of Immobilized Receptors". In Artificial Receptors for Chemical Sensors, 1–15. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2010. http://dx.doi.org/10.1002/9783527632480.ch1.

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Codd, Rachel, Jiesi Gu, Najwa Ejje e Tulip Lifa. "New Applications of Immobilized Metal Ion Affinity Chromatography in Chemical Biology". In Inorganic Chemical Biology, 1–35. Chichester, UK: John Wiley & Sons, Ltd, 2014. http://dx.doi.org/10.1002/9781118682975.ch1.

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Gutsev, G. L., e A. I. Boldyrev. "The Theoretical Investigation of the Electron Affinity of Chemical Compounds". In Advances in Chemical Physics, 169–221. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2007. http://dx.doi.org/10.1002/9780470142851.ch3.

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Atti di convegni sul tema "Chemical affinity"

Weaver, John B., e Adam M. Rauwerdink. "Chemical binding affinity estimation using MSB". In SPIE Medical Imaging, a cura di John B. Weaver e Robert C. Molthen. SPIE, 2011. http://dx.doi.org/10.1117/12.878788.

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"Estrogen receptor binding affinity estimated by QSAR". In International Institute of Chemical, Biological & Environmental Engineering. International Institute of Chemical, Biological & Environmental Engineering, 2015. http://dx.doi.org/10.15242/iicbe.c0615100.

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Freidin, Alexander B. "Chemical Affinity Tensor and Stress-Assist Chemical Reactions Front Propagation in Solids". In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-64957.

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We consider a stress-assist chemical reaction front propagation in a deformable solid undergoing a localized chemical reaction between solid and gas constituents. The reaction is sustained by the diffusion of the gas constituent through the transformed solid material. We introduce a chemical transformations strain tensor that relates two reference configurations of solid constituents. Then mass, momentum and energy balances are written down for the open system considered and the expression of the entropy production due to the reaction front propagation in a solid with arbitrary constitutive equations is derived. As a result, the expression of the chemical affinity tensor is obtained. Kinetic equation for the chemical reactions front propagation is formulated in a form of the dependence of the front velocity on normal components of the chemical affinity tensor. The locking effect — blocking the reaction by stresses is demonstrated. Finally the kinetic equation for the bulk chemical reaction is derived in a form of the dependence of the reaction rate on the first invariant of the chemical affinity tensor.

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Yang, Yin-Jie, Ellis M. Shelley, Yi-Chia Liaw, Shing-Yi Suen, Min-Ying Wang, Eric D. Conte, Tai-Hong Cheng, Cheng-Chiang Huang e Shin-Ying Chou. "Preparation of Polyacrylonitrile-based Immobilized Metal-Ion Affinity Membrane for Protein Adsorption". In 14th Asia Pacific Confederation of Chemical Engineering Congress. Singapore: Research Publishing Services, 2012. http://dx.doi.org/10.3850/978-981-07-1445-1_304.

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Yang, Shiau-Jyun, e Yu-Kaung Chang. "Method Development for Extraction of GST-EGFP Fusion Protein by Immobilized Metal Affinity Chromatography". In 14th Asia Pacific Confederation of Chemical Engineering Congress. Singapore: Research Publishing Services, 2012. http://dx.doi.org/10.3850/978-981-07-1445-1_714.

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Vijayakumaran, Thivina, U. Hashim, A. Rahim Ruslinda, M. K. Arshad, P. Veeradasan e N. K. S. Nordin. "Improving the affinity of silicon surface for biosensor application: The interaction between multiwall carbon nanotube (MWCNT) and chitosan (CS)". In 11TH ASIAN CONFERENCE ON CHEMICAL SENSORS: (ACCS2015). Author(s), 2017. http://dx.doi.org/10.1063/1.4975294.

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Chou, Yan-Syun, e Yu-kaung Chang. "Stirred Fluidized Bed Immobilized Metal Affinity Chromatography for Direct Recovery of Poly His-tagged Enhanced Green Fluorescent Protein". In 14th Asia Pacific Confederation of Chemical Engineering Congress. Singapore: Research Publishing Services, 2012. http://dx.doi.org/10.3850/978-981-07-1445-1_709.

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Na Luo, Wei Feng, Xiaoqiang Wang e Feng Qian. "Dynamic optimization of chemical engineering problems using affinity propagation based estimation of distribution algorithm". In 2014 11th World Congress on Intelligent Control and Automation (WCICA). IEEE, 2014. http://dx.doi.org/10.1109/wcica.2014.7053323.

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Mosentsova, K. I., A. V. Toropova, M. Nour, A. Eldeeb e D. M. Kolpashchikov. "DEPENDENCE OF THE AFFINITY OF OLIGONUCLEOTIDES ON CHEMICAL MODIFICATIONS AND THE LENGTH OF NUCLEOTIDE SEQUENCES". In X Международная конференция молодых ученых: биоинформатиков, биотехнологов, биофизиков, вирусологов и молекулярных биологов — 2023. Novosibirsk State University, 2023. http://dx.doi.org/10.25205/978-5-4437-1526-1-278.

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In the work, such methods of changing the affinity of DNKzyms as chemical modifications and changes in the length of the nucleotide sequences of the arms were considered. This makes it possible to prioritize the activation of two types of DNKzyms gates to determine the concentration of an oncomarker in solution.

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CHEN, KUAN, e THOMAS EDDY. "Investigation of chemical affinity for reacting flows of non-LThE (non-Local Thermal Equilibrium) gases". In 24th Plasma Dynamics, and Lasers Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1993. http://dx.doi.org/10.2514/6.1993-3225.

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Rapporti di organizzazioni sul tema "Chemical affinity"

Glasscott, Matthew, Johanna Jernberg, Erik Alberts e Lee Moores. Toward the electrochemical detection of 2,4-dinitroanisole (DNAN) and pentaerythritol tetranitrate (PETN). Engineer Research and Development Center (U.S.), marzo 2022. http://dx.doi.org/10.21079/11681/43826.

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Analytical methods to rapidly detect explosive compounds with high precision are paramount for applications ranging from national security to environmental remediation. This report demonstrates two proof-of-concept electroanalytical methods for the quantification of 2,4-dinitroanisol (DNAN) and pentaerythritol tetranitrate (PETN). For the first time, DNAN reduction was analyzed and compared at a bare graphitic carbon electrode, a polyaniline-modified (PANI) electrode, and a molecularly imprinted polymer (MIP) electrode utilizing PANI to explore the effect of surface-area and preconcentration affinity on the analytical response. Since some explosive compounds such as PETN are not appreciably soluble in water (<10 μg/L), necessitating a different solvent system to permit direct detection via electrochemical reduction. A 1,2-dichloroethane system was explored as a possibility by generating a liquid-liquid extraction-based sensor exploiting the immiscibility of 1,2-dichloroethane and water. The reduction process was explored using a scan rate analysis to extract a diffusion coefficient of 6.67 x 10⁻⁶ cm/s, in agreement with literature values for similarly structured nitrate esters. Once further refined, these techniques may be extended to other explosives and combined with portable electrochemical hardware to bring real-time chemical information to soldiers and citizens alike.

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Author, Not Given. Colloids in groundwater: Their mobilization, subsurface transport, and sorption affinity for toxic chemicals. Office of Scientific and Technical Information (OSTI), gennaio 1991. http://dx.doi.org/10.2172/6144063.

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Gschwend, P. M. Colloids in groundwater: Their mobilization, subsurface transport, and sorption affinity for toxic chemicals. Office of Scientific and Technical Information (OSTI), luglio 1992. http://dx.doi.org/10.2172/7288440.

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Chen, Yona, Jeffrey Buyer e Yitzhak Hadar. Microbial Activity in the Rhizosphere in Relation to the Iron Nutrition of Plants. United States Department of Agriculture, ottobre 1993. http://dx.doi.org/10.32747/1993.7613020.bard.

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Iron is the fourth most abundant element in the soil, but since it forms insoluble hydroxides at neutral and basic pH, it often falls short of meeting the basic requirements of plants and microorganisms. Most aerobic and facultative aerobic microorganisms possess a high-affinity Fe transport system in which siderophores are excreted and the consequent Fe complex is taken up via a cognate specific receptor and a transport pathway. The role of the siderophore in Fe uptake by plants and microorganisms was the focus of this study. In this research Rhizopus arrhizus was found to produce a novel siderophore named Rhizoferrin when grown under Fe deficiency. This compound was purified and its chemical structure was elucidated. Fe-Rhizoferrin was found to alleviate Fe deficiency when applied to several plants grown in nutrient solutions. It was concluded that Fe-Rhizoferrin is the most efficient Fe source for plants when compared with other among microbial siderophores known to date and its activity equals that of the most efficient synthetic commercial iron fertilizer-Fe EDDHA. Siderophores produced by several rhizosphere organisms including Rhizopus Pseudomonas were purified. Monoclonal antibodies were produced and used to develop a method for detection of the siderophores produced by plant-growth-promoting microorganisms in barley rhizosphere. The presence of an Fe-ferrichrome uptake in fluorescent Pseudomonas spp. was demonstrated, and its structural requirements were mapped in P. putida with the help of biomimetic ferrichrome analogs. Using competition experiments, it was shown that FOB, Cop B and FC share at least one common determinant in their uptake pathway. Since FC analogs did not affect FOB or Cop-mediated 55Fe uptake, it could be concluded that these siderophores make use of a different receptor(s) than FC. Therefore, recognition of Cop, FOB and FC proceeds through different receptors having different structural requirements. On the other hand, the phytosiderophores mugineic acid (MA and DMA), were utilized indirectly via ligand exchange by P. putida. Receptors from different biological systems seem to differ in their structural requirements for siderophore recognition and uptake. The design of genus- or species-specific drugs, probes or chemicals, along with an understanding of plant-microbe and microbe-microbe relationships as well as developing methods to detect siderophores using monoclonal antibodies are useful for manipulating the composition of the rhizosphere microbial population for better plant growth, Fe-nutrition and protection from diseases.

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Gschwend, P. M. Colloids in groundwater: Their mobilization, subsurface transport, and sorption affinity for toxic chemicals. Annual technical progress report. Office of Scientific and Technical Information (OSTI), luglio 1992. http://dx.doi.org/10.2172/10168896.

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Chefetz, Benny, Baoshan Xing e Yona Chen. Interactions of engineered nanoparticles with dissolved organic matter (DOM) and organic contaminants in water. United States Department of Agriculture, gennaio 2013. http://dx.doi.org/10.32747/2013.7699863.bard.

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Background: Engineered carbon nanotubes (CNTs) are expected to be increasingly released into the environment with the rapid increase in their production and use. The discharged CNTs may interact with coexisting contaminants and subsequently change environmental behaviors and ecological effects of both the CNTs themselves and the contaminants. Dissolved organic matter (DOM) plays a critical role in the transport of CNTs in the aquatic environment, affecting both CNT's surface properties through adsorption, and its colloidal stability in solution. Therefore, CNT-bound DOM complexes may interact with coexisting contaminants, thus affecting their environmental fate. With increasing production and use of CNTs, there is an increasing risk that humans could be exposed to CNTs mainly through ingestion and inhalation. Since CNTs can be carriers of contaminants due to their high adsorption affinity and capacity, the distribution of these nanoparticles in the environment holds a potential environmental and health risk. Project objectives: The overall goal of this project was to gain a better understanding of the environmental behavior of engineered nanoparticles with DOM and organic pollutant in aqueous systems. The scope of this study includes: characterizing various types of engineered nanoparticles and their interaction with DOM; binding studies of organic contaminants by nanoparticles and DOM-nanoparticle complexes; and examining interactions in DOM-nanoparticles-contaminant systems. Major conclusions, solutions and achievements: DOM has a pronounced effect on colloidal stability of CNTs in solution and on their surface chemistry and reactivity toward associated contaminants. The structure and chemical makeup of both CNTs and DOM determine their interactions and nature of formed complexes. CNTs, contaminants and DOM can co-occur in the aquatic environment. The occurrence of co-contaminants, as well as of co-introduction of DOM, was found to suppress the adsorption of organic contaminants to CNTs through both competition over adsorption sites and direct interactions in solution. Furthermore, the release of residual contaminants from CNTs could be enhanced by biomolecules found in the digestive as well as the respiratory tracts, thus increasing the bioaccessibility of adsorbed contaminants and possibly the overall toxicity of contaminant-associated CNTs. Contaminant desorption could be promoted by both solubilization and sorptive competition by biological surfactants. Scientific and agricultural implications: The information gained in the current project may assist in predicting the transport and fate of both CNTs and associated contaminants in the natural environment. Furthermore, the results imply a serious health risk from contaminant-associated CNTs.

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Avnimelech, Yoram, Richard C. Stehouwer e Jon Chorover. Use of Composted Waste Materials for Enhanced Ca Migration and Exchange in Sodic Soils and Acidic Minespoils. United States Department of Agriculture, giugno 2001. http://dx.doi.org/10.32747/2001.7575291.bard.

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Restoration of degraded lands and the development of beneficial uses for waste products are important challenges facing our society. In addition there is a need to find useful and environmentally friendly applications for the organic fractions of municipal and other solid waste. Recent studies have shown that composted wastes combined with gypsum or gypsum-containing flue gas desulfurization by-products enhance restoration of sodic soils and acidic minespoils. The mechanism by which this synergistic effect occurs in systems at opposite pH extremes appears to involve enhanced Ca migration and exchange. Our original research objectives were to (1) identify and quantify the active compost components involved in Ca transport, (2) determine the relative affinity of the compost components for Ca and competing metals in the two soil/spoil systems, (3) determine the efficacy of the compost components in Ca transport to subjacent soil and subsequent exchange with native soil cations, and (4) assess the impacts of compost enhanced Ca transport on soil properties and plant growth. Acidic mine spoils: During the course of the project the focus for objective (1) and (2) shifted more towards developing and evaluating methods to appropriately quantify Ca2+ and Al3+ binding to compost derived dissolved organic matter (DOM). It could be shown that calcium complexation by sewage sludge compost derived DOM did not significantly change during the composting process. A method for studying Al3+ binding to DOM was successfully developed and should allow future insight into DOM-Al3+ interactions in general. Laboratory column experiments as well as greenhouse experiments showed that in very acidic mine spoil material mineral dissolution controls solution Al3+ concentration as opposed to exchange with Ca2+. Therefore compost appeared to have no effect on Al3+ and Ca2+ mobility and did not affect subsoil acidity. Sodic alkaline soils: Batch experiments with Na+ saturated cation exchange resins as a model for sodic soils showed that compost home cations exchanged readily with Na+. Unlike filtered compost extracts, unfiltered compost suspensions also significantly increased Ca2+ release from CaCO3. Soil lysimeter experiments demonstrated a clear impact of compost on structural improvement in sodic alkaline soils. Young compost had faster, clearer and longer lasting effects on soil physical and chemical properties than mature compost. Even after 2 growing seasons differences could still be observed. Compost increased Ca2+ concentration in soil solution and solubility of pedogenic CaCO3 that is highly insoluble under alkaline conditions. The solubilized Ca2+ efficiently exchanged Na+ in the compost treated soils and thus greatly improved the soil structure.

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Landau, Sergei Yan, John W. Walker, Avi Perevolotsky, Eugene D. Ungar, Butch Taylor e Daniel Waldron. Goats for maximal efficacy of brush control. United States Department of Agriculture, marzo 2008. http://dx.doi.org/10.32747/2008.7587731.bard.

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Background. Brush encroachment constitutes a serious problem in both Texas and Israel. We addressed the issue of efficacy of livestock herbivory - in the form of goat browsing - to change the ecological balance to the detriment of the shrub vegetation. Shrub consumption by goats is kept low by plant chemical defenses such as tannins and terpenes. Scientists at TAES and ARO have developed an innovative, cost-effective methodology using fecal Near Infrared Spectrometry to elucidate the dietary percentage of targeted, browse species (terpene-richredberry and blueberry juniper in the US, and tannin-rich Pistacialentiscus in Israel) for a large number of animals. The original research objectives of this project were: 1. to clarify the relative preference of goat breeds and the individual variation of goats within breeds, when consuming targeted brush species; 2. to assess the heritability of browse intake and validate the concept of breeding goat lines that exhibit high preference for chemically defended brush, using juniper as a model; 3. to clarify the relative contributions of genetics and learning on the preference for target species; 4. to identify mechanisms that are associated with greater intake of brush from the two target species; 5. to establish when the target species are the most vulnerable to grazing. (Issue no.5 was addressed only partly.) Major conclusions, solutions, achievements: Both the Israel and US scientists put significant efforts into improving and validating the technique of Fecal NIRS for predicting the botanical composition of goat diets. Israeli scientists validated the use of observational data for calibrating fecal NIRS, while US scientists established that calibrations could be used across animals differing in breed and age but that caution should be used in making comparisons between different sexes. These findings are important because the ability to select goat breeds or individuals within a breed for maximal efficiency of brush control is dependent upon accurate measurement of the botanical composition of the diet. In Israel it was found that Damascus goats consume diets more than twice richer in P. lentiscus than Mamber or Boer goats. In the US no differences were found between Angora and Boer cross goats but significant differences were found between individuals within breeds in juniper dietary percentage. In both countries, intervention strategies were found that further increased the consumption of the chemically defended plant. In Israel feeding polyethylene glycol (PEG, MW 4,000) that forms high-affinity complexes with tannins increased P. lentiscus dietary percentage an average of 7 percentage units. In the US feeding a protein supplement, which enhances rates of P450-catalyzed oxidations and therefore the rate of oxidation of monoterpenes, increased juniper consumption 5 percentage units. However, the effects of these interventions were not as large as breed or individual animal effects. Also, in a wide array of competitive tannin-binding assays in Israel with trypsin, salivary proteins did not bind more tannic acid or quebracho tannin than non-specific bovine serum albumin, parotid saliva did not bind more tannins than mixed saliva, no response of tannin-binding was found to levels of dietary tannins, and the breed effect was of minor importance, if any. These fundings strongly suggest that salivary proteins are not the first line of defense from tannin astringency in goats. In the US relatively low values for heritability and repeatability for juniper consumption were found (13% and 30%, respectively), possibly resulting from sampling error or non-genetic transfer of foraging behavior, i.e., social learning. Both alternatives seem to be true as significant variation between sequential observations were noted on the same animal and cross fostering studies conducted in Israel demonstrated that kids raised by Mamber goats showed lower propensity to consume P. lentiscus than counterparts raised by Damascus goats.

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Shomer, Ilan, Ruth E. Stark, Victor Gaba e James D. Batteas. Understanding the hardening syndrome of potato (Solanum tuberosum L.) tuber tissue to eliminate textural defects in fresh and fresh-peeled/cut products. United States Department of Agriculture, novembre 2002. http://dx.doi.org/10.32747/2002.7587238.bard.

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The project sought to understand factors and mechanisms involved in the hardening of potato tubers. This syndrome inhibits heat softening due to intercellular adhesion (ICA) strengthening, compromising the marketing of industrially processed potatoes, particularly fresh peeled-cut or frozen tubers. However, ICA strengthening occurs under conditions which are inconsistent with the current ideas that relate it to Ca-pectate following pectin methyl esterase (PME) activity or to formation of rhamnogalacturonan (RG)-II-borate. First, it was necessary to induce strengthening of the middle lamellar complex (MLX) and the ICA as a stress response in some plant parenchyma. As normally this syndrome does not occur uniformly enough to study it, we devised an efficient model in which ICA-strengthening is induced consistently under simulated stress by short-chain, linear, mono-carboxylic acid molecules (OAM), at 65 oC [appendix 1 (Shomer&Kaaber, 2006)]. This rapid strengthening was insufficient for allowing the involved agents assembly to be identifiable; but it enabled us to develop an efficient in vitro system on potato tuber parenchyma slices at 25 ºC for 7 days, whereas unified stress was reliably simulated by OAMs in all the tissue cells. Such consistent ICA-strengthening in vitro was found to be induced according to the unique physicochemical features of each OAM as related to its lipophilicity (Ko/w), pKa, protonated proportion, and carbon chain length by the following parameters: OAM dissociation constant (Kdiss), adsorption affinity constant (KA), number of adsorbed OAMs required for ICA response (cooperativity factor) and the water-induced ICA (ICAwater). Notably, ICA-strengthening is accompanied by cell sap leakage, reflecting cell membrane rupture. In vitro, stress simulation by OAMs at pH<pKa facilitated the consistent assembly of ICAstrengthening agents, which we were able to characterize for the first time at the molecular level within purified insoluble cell wall of ICA-strengthened tissue. (a) With solid-state NMR, we established the chemical structure and covalent binding to cell walls of suberin-like agents associated exclusively with ICA strengthening [appendix 3 (Yu et al., 2006)]; (b) Using proteomics, 8 isoforms of cell wall-bound patatin (a soluble vacuolar 42-kDa protein) were identified exclusively in ICA-strengthened tissue; (c) With light/electron microscopy, ultrastructural characterization, histochemistry and immunolabeling, we co-localized patatin and pectin in the primary cell wall and prominently in the MLX; (d) determination of cell wall composition (pectin, neutral sugars, Ca-pectate) yielded similar results in both controls and ICA-strengthened tissue, implicating factors other than PME activity, Ca2+ or borate ions; (e) X-ray powder diffraction experiments revealed that the cellulose crystallinity in the cell wall is masked by pectin and neutral sugars (mainly galactan), whereas heat or enzymatic pectin degradation exposed the crystalline cellulose structure. Thus, we found that exclusively in ICA-strengthened tissue, heat-resistant pectin is evident in the presence of patatin and suberinlike agents, where the cellulose crystallinity was more hidden than in fresh control tissue. Conclusions: Stress response ICA-strengthening is simulated consistently by OAMs at pH< pKa, although PME and formation of Ca-pectate and RG-II-borate are inhibited. By contrast, at pH>pKa and particularly at pH 7, ICA-strengthening is mostly inhibited, although PME activity and formation of Ca-pectate or RG-II-borate are known to be facilitated. We found that upon stress, vacuolar patatin is released with cell sap leakage, allowing the patatin to associate with the pectin in both the primary cell wall and the MLX. The stress response also includes formation of covalently bound suberin-like polyesters within the insoluble cell wall. The experiments validated the hypotheses, thus led to a novel picture of the structural and molecular alterations responsible for the textural behavior of potato tuber. These findings represent a breakthrough towards understanding of the hardening syndrome, laying the groundwork for potato-handling strategies that assure textural quality of industrially processed particularly in fresh peeled cut tubers, ready-to-prepare and frozen preserved products.

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