Articles de revues : « Amino terminated molecules »

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Baumgärtel, Thomas, Christian von Borczyskowski et Harald Graaf. « Selective surface modification of lithographic silicon oxide nanostructures by organofunctional silanes ». Beilstein Journal of Nanotechnology 4 (25 mars 2013) : 218–26. http://dx.doi.org/10.3762/bjnano.4.22.

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This study investigates the controlled chemical functionalization of silicon oxide nanostructures prepared by AFM-anodization lithography of alkyl-terminated silicon. Different conditions for the growth of covalently bound mono-, multi- or submonolayers of distinctively functional silane molecules on nanostructures have been identified by AFM-height investigations. Routes for the preparation of methyl- or amino-terminated structures or silicon surfaces are presented and discussed. The formation of silane monolayers on nanoscopic silicon oxide nanostructures was found to be much more sensitive towards ambient humidity than, e.g., the silanization of larger OH-terminated silica surfaces. Amino-functionalized nanostructures have been successfully modified by the covalent binding of functional fluorescein dye molecules. Upon excitation, the dye-functionalized structures show only weak fluorescence, which may be an indication of a relatively low surface coverage of the dye molecules on length scale that is not accessible by standard AFM measurements.

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Levine, Zachary A., Michael V. Rapp, Wei Wei, Ryan Gotchy Mullen, Chun Wu, Gül H. Zerze, Jeetain Mittal, J. Herbert Waite, Jacob N. Israelachvili et Joan-Emma Shea. « Surface force measurements and simulations of mussel-derived peptide adhesives on wet organic surfaces ». Proceedings of the National Academy of Sciences 113, n^o 16 (28 mars 2016) : 4332–37. http://dx.doi.org/10.1073/pnas.1603065113.

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Translating sticky biological molecules—such as mussel foot proteins (MFPs)—into synthetic, cost-effective underwater adhesives with adjustable nano- and macroscale characteristics requires an intimate understanding of the glue’s molecular interactions. To help facilitate the next generation of aqueous adhesives, we performed a combination of surface forces apparatus (SFA) measurements and replica-exchange molecular dynamics (REMD) simulations on a synthetic, easy to prepare, Dopa-containing peptide (MFP-3s peptide), which adheres to organic surfaces just as effectively as its wild-type protein analog. Experiments and simulations both show significant differences in peptide adsorption on CH3-terminated (hydrophobic) and OH-terminated (hydrophilic) self-assembled monolayers (SAMs), where adsorption is strongest on hydrophobic SAMs because of orientationally specific interactions with Dopa. Additional umbrella-sampling simulations yield free-energy profiles that quantitatively agree with SFA measurements and are used to extract the adhesive properties of individual amino acids within the context of MFP-3s peptide adhesion, revealing a delicate balance between van der Waals, hydrophobic, and electrostatic forces.

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Gorkan, T., H. Arkin et E. Aktürk. « Influence of doping with selected organic molecules on the magnetic and electronic properties of bare, surface terminated and defect patterned Ti₂C MXene monolayers ». Physical Chemistry Chemical Physics 24, n^o 4 (2022) : 2465–75. http://dx.doi.org/10.1039/d1cp04359e.

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In this study, based on the density functional theory, we examine the interaction between the bare, F-, OH-terminated as well as defect patterned Ti2C and selected neurotransmitter (NT) and amino acids (AA) such as dopamine, glutamate, glycine and serine.

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Schneider, Jens, Christin Fricke, Heike Overwin, Birgit Hofmann et Bernd Hofer. « Generation of Amylosucrase Variants That Terminate Catalysis of Acceptor Elongation at the Di- or Trisaccharide Stage ». Applied and Environmental Microbiology 75, n^o 23 (2 octobre 2009) : 7453–60. http://dx.doi.org/10.1128/aem.01194-09.

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ABSTRACT An amylosucrase gene was subjected to high-rate segmental random mutagenesis, which was directed toward a segment encoding amino acids that influence the interaction with substrate molecules in subsites −1 to +3. A screen was used to identify enzyme variants with compromised glucan chain elongation. With an average mutation rate of about one mutation per targeted codon, a considerable fraction (82%) of the clones that retained catalytic activity were deficient in this trait. A detailed characterization of selected variants revealed that elongation terminated when chains reached lengths of only two or three glucose moieties. Sequencing showed that the amylosucrase derivatives had an average of no more than two amino acid substitutions and suggested that predominantly exchanges of Asp394 or Gly396 were crucial for the novel properties. Structural models of the variants indicated that steric interference between the amino acids introduced at these sites and the growing oligosaccharide chain are mainly responsible for the limitation of glucosyl transfers. The variants generated may serve as biocatalysts for limited addition of glucose moieties to acceptor molecules, using sucrose as a readily available donor substrate.

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Chen, Acong, Xin Xin, Jie Xu, Yu Bian et Zhaoyong Bian. « Cadmium ion adsorption by amine-modified activated carbon ». Water Science and Technology 75, n^o 7 (24 janvier 2017) : 1675–83. http://dx.doi.org/10.2166/wst.2017.042.

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Cadmium (Cd) is one of the most toxic metals found in water and sediments. In the effort to develop an effective adsorbent for aqueous Cd removal, activated carbon (AC) was modified with an amino-terminated organosilicon (3-aminopropyltrimethoxysilane, APS). Response surface methodology was used to optimize selected operational parameters of adsorption of aqueous Cd by considering a central composite design with three input variables, temperature of the mixture solution, the contact time and feed ratio (APS/AC), on the surface modification. Results demonstrated that the strong Cd-binding amine ligands were effectively introduced onto the AC surfaces through the silanol reaction between carbon surface functional groups (–COOH, –COH) and APS molecules. The optimized preparation condition is 77 °C, 4 h and 2.1 ratio. The adsorbent presented a favorable adsorption of the aqueous Cd(II).

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Song, Zhiguang, Shiyuan Cui, Cuiping Tang, Yong Chen, Deqing Liang et Sibo Wang. « Effect of a Terminated PVCap on Methane Gas Hydrate Formation ». Journal of Marine Science and Engineering 11, n^o 2 (27 janvier 2023) : 282. http://dx.doi.org/10.3390/jmse11020282.

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Polyvinylcaprolactam (PVCap) is an economic kinetic inhibitor for hydrate formation in pipelines during oil and gas transportation. However, its application is limited because of the low inhibition performance under certain conditions. In this work, a modified PVCap on its chain end is proposed.2-amino-3-propionic acid mercapto-terminated polyvinyl caprolactam (PVCap-NH2-COOH) was synthesized and its performance as a KHI for methane hydrate formation was evaluated under different conditions. Results showed that the performance of PVCap-NH2-COOH as a KHI was better than that of PVCap at the same concentrations. Gas hydrate samples with 1 wt.% PVCap-NH2-COOH were measured using Raman spectroscopy, XRD, and cryo-SEM. PVCap-NH2-COOH had a selective action on a specific crystal surface of the hydrates and could prevent methane molecules from entering large cages. Its inhibition ability increased with the decrease in the occupancy rate of large cages. The morphology of the gas hydrate crystal changed from porous in a pure water system to a chaotic but compact structure state in the system with PVCap-NH2-COOH.

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Hayashi, Kazuyuki, Atsushi Hozumi, Nagahiro Saito, Hiroyuki Sugimura et Osamu Takai. « Selective immobilization of functional organic molecules onto a microtemplate fabricated using an amino-terminated self-assembled monolayer ». Surface Science 532-535 (juin 2003) : 1072–78. http://dx.doi.org/10.1016/s0039-6028(03)00211-5.

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Enders, Dominik, Tadaaki Nagao et Tomonobu Nakayama. « Two-Step Desorption Process of Au Nanoparticles in D2O Suspension on Amino-Terminated SiO2/Si Substrate Induced by Small Thiol Molecules ». Japanese Journal of Applied Physics 46, n^o 5A (8 mai 2007) : 3020–23. http://dx.doi.org/10.1143/jjap.46.3020.

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de Medeiros, S. F., F. Amato, C. D. Matthews et R. J. Norman. « Molecular heterogeneity of the β-core fragment of human chorionic gonadotrophin ». Journal of Endocrinology 139, n^o 3 (décembre 1993) : 519–32. http://dx.doi.org/10.1677/joe.0.1390519.

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ABSTRACT We have analysed the structure and composition of the β-core fragment of human chorionic gonadotrophin (βC-hCG) from fresh urine specimens obtained from pregnant women and compared our findings with those previously proposed by other groups using different protocols. SDS-PAGE separation of reduced βC-hCG demonstrated two major bands with apparent molecular weights of Mr 8900 and Mr 7500. The molecular weight of the agalacto βC-hCG was estimated to be Mr 10 218 from the amino acid analysis after high-performance liquid chromatography (HPLC) separation. Moreover, HPLC separation of its reduced and S-carboxymethylated peptides resulted in three peaks, but only two of them could be sequenced and demonstrated to be the previously reported β6-40 (Mr 5000) and β55-92 (Mr 5300) peptides of the βhCG subunit. The results showed that 56-78% of βC-hCG molecules of molecular weight Mr 12 800 were able to bind Concanavalin A (Con A). While most were lacking all the peripheral monosaccharides and terminated in mannose, some retained other sugar residues on their antennae. Direct carbohydrate analysis showed the following molar content normalized to six mannose molecules: galactose 2·8, glucosamine 5·3, galactosamine 0·3, fucose 1·7 and sialic acid 3·0. Approximately 22–44% of the βC-hCG molecules did not bind Con A (Con A non-reactive forms), of which 88% were totally deprived of sugar units and had an apparent molecular weight of approximately Mr 10 000, and 12% were weakly reactive to Con A and reactive to anion exchange (negatively charged forms), being incompletely trimmed of their oligosaccharide chains. Comparison of our results with those of two other groups have indicated that the differences noted among preparations are due to either the source or the methods used to purify and characterize this fragment. In addition, our results showed significant microheterogeneity on the N-linked oligosaccharide moieties with some molecules apparently having no sugar molecules. These results have implications for the origins of βC-hCG, suggesting secretion of some molecules without sugar chains and in other cases possible metabolism of hCG in the peripheral tissues. Journal of Endocrinology (1993) 139, 519–532

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Tamura, Atsushi, Asato Tonegawa, Yoshinori Arisaka et Nobuhiko Yui. « Versatile synthesis of end-reactive polyrotaxanes applicable to fabrication of supramolecular biomaterials ». Beilstein Journal of Organic Chemistry 12 (28 décembre 2016) : 2883–92. http://dx.doi.org/10.3762/bjoc.12.287.

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Cyclodextrin (CD)-threaded polyrotaxanes (PRXs) with reactive functional groups at the terminals of the axle polymers are attractive candidates for the design of supramolecular materials. Herein, we describe a novel and simple synthetic method for end-reactive PRXs using bis(2-amino-3-phenylpropyl) poly(ethylene glycol) (PEG-Ph-NH2) as an axle polymer and commercially available 4-substituted benzoic acids as capping reagents. The terminal 2-amino-3-phenylpropyl groups of PEG-Ph-NH2 block the dethreading of the α-CDs after capping with 4-substituted benzoic acids. By this method, two series of azide group-terminated polyrotaxanes (benzylazide: PRX-Bn-N3, phenylazide: PRX-Ph-N3,) were synthesized for functionalization via click reactions. The PRX-Bn-N3 and PRX-Ph-N3 reacted quickly and efficiently with p-(tert-butyl)phenylacetylene via copper-catalyzed click reactions. Additionally, the terminal azide groups of the PRX-Bn-N3 could be modified with dibenzylcyclooctyne (DBCO)-conjugated fluorescent molecules via a copper-free click reaction; this fluorescently labeled PRX was utilized for intracellular fluorescence imaging. The method of synthesizing end-reactive PRXs described herein is simple and versatile for the design of diverse functional PRXs and can be applied to the fabrication of PRX-based supramolecular biomaterials.

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Magrath, Christi, et Linda E. Hyman. « A Mutation in GRS1, a Glycyl-tRNA Synthetase, Affects 3′-End Formation in Saccharomyces cerevisiae ». Genetics 152, n^o 1 (1 mai 1999) : 129–41. http://dx.doi.org/10.1093/genetics/152.1.129.

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Abstract 3′-end formation is a complex and incompletely understood process involving both cis-acting and trans-acting factors. As part of an effort to examine the mechanisms of transcription termination by RNA polymerase II, a mutant hunt for strains defective in 3′-end formation was conducted. Following random mutagenesis, a temperature-sensitive strain exhibiting several phenotypes consistent with a role in transcription termination was isolated. First, readthrough of a terminator increases significantly in the mutant strain. Accordingly, RNA analysis indicates a decrease in the level of terminated transcripts, both in vivo and in vitro. Moreover, a plasmid stability assay in which high levels of readthrough lead to high levels of plasmid loss and transcription run-on analysis also demonstrate defective termination of transcription. Examination of polyadenylation and cleavage by the mutant strain indicates these processes are not affected. These results represent the first example of a transcription termination factor in Saccharomyces cerevisiae that affects transcription termination independent of 3′-end processing of mRNA. Complementation studies identified GRS1, an aminoacyl-tRNA synthetase, as the complementing gene. Sequence analysis of grs1-1 in the mutant strain revealed that nucleotides 1656 and 1657 were both C to T transitions, resulting in a single amino acid change of proline to phenylalanine. Further studies revealed GRS1 is essential, and the grs1-1 allele confers the temperature-sensitive growth defect associated with the mutant strain. Finally, we observed structures with some similarity to tRNA molecules within the 3′-end of various yeast genes. On the basis of our results, we suggest Grs1p is a transcription termination factor that may interact with the 3′-end of pre-mRNA to promote 3′-end formation.

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Xi, Erte, Vasudevan Venkateshwaran, Lijuan Li, Nicholas Rego, Amish J. Patel et Shekhar Garde. « Hydrophobicity of proteins and nanostructured solutes is governed by topographical and chemical context ». Proceedings of the National Academy of Sciences 114, n^o 51 (20 novembre 2017) : 13345–50. http://dx.doi.org/10.1073/pnas.1700092114.

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Hydrophobic interactions drive many important biomolecular self-assembly phenomena. However, characterizing hydrophobicity at the nanoscale has remained a challenge due to its nontrivial dependence on the chemistry and topography of biomolecular surfaces. Here we use molecular simulations coupled with enhanced sampling methods to systematically displace water molecules from the hydration shells of nanostructured solutes and calculate the free energetics of interfacial water density fluctuations, which quantify the extent of solute–water adhesion, and therefore solute hydrophobicity. In particular, we characterize the hydrophobicity of curved graphene sheets, self-assembled monolayers (SAMs) with chemical patterns, and mutants of the protein hydrophobin-II. We find that water density fluctuations are enhanced near concave nonpolar surfaces compared with those near flat or convex ones, suggesting that concave surfaces are more hydrophobic. We also find that patterned SAMs and protein mutants, having the same number of nonpolar and polar sites but different geometrical arrangements, can display significantly different strengths of adhesion with water. Specifically, hydroxyl groups reduce the hydrophobicity of methyl-terminated SAMs most effectively not when they are clustered together but when they are separated by one methyl group. Hydrophobin-II mutants show that a charged amino acid reduces the hydrophobicity of a large nonpolar patch when placed at its center, rather than at its edge. Our results highlight the power of water density fluctuations-based measures to characterize the hydrophobicity of nanoscale surfaces and caution against the use of additive approximations, such as the commonly used surface area models or hydropathy scales for characterizing biomolecular hydrophobicity and the associated driving forces of assembly.

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Ariel, Amiram, Eran J. Yavin, Rami Hershkoviz, Ann Avron, Suzanne Franitza, Izhar Hardan, Liora Cahalon, Mati Fridkin et Ofer Lider. « IL-2 Induces T Cell Adherence to Extracellular Matrix : Inhibition of Adherence and Migration by IL-2 Peptides Generated by Leukocyte Elastase ». Journal of Immunology 161, n^o 5 (1 septembre 1998) : 2465–72. http://dx.doi.org/10.4049/jimmunol.161.5.2465.

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Abstract Migration of inflammatory cells requires cell adhesion and their subsequent detachment from the extracellular matrix (ECM). Leukocyte activation and migration must be terminated to stop inflammation. Here, we report that IL-2 enhances human T cell adherence to laminin, collagen type IV, and fibronectin (FN). In contrast, neutrophil elastase, an enzyme activated during inflammation, degrades IL-2 to yield IL-2 fractions that inhibit IL-2-induced T cell adhesion to FN. The amino acid composition of two of these IL-2 fractions, which appear to block T cell adherence to FN, were analyzed, and three peptides were consequently synthesized. The three peptides IVL, RMLT, and EFLNRWIT, but not the corresponding inversely synthesized peptides, inhibited T cell adhesion to FN induced by a variety of activators: IL-2, IL-7, macrophage inflammatory protein (MIP)-1β, and PMA, as well as anti-CD3 and anti-β1 integrin-activating mAb. Moreover, these IL-2 peptides inhibited T cell chemotaxis via FN-coated membranes induced by IL-2 and MIP-1β. Inhibition of T cell adherence and migration apparently involves abrogation of the rearrangement of the T cell actin cytoskeleton. Thus, the migrating immune cells, the cytokines, and the ECM can create a functional relationship in which both inflammation-inducing signals and inhibitory molecules of immune responses can coexist; the enzymatic products of IL-2 may serve as natural feedback inhibitors of inflammation.

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Flores-Perez, Rosangelly, et Albena Ivanisevic. « Molecular recognition of chromophore molecules to amine terminated surfaces ». Applied Surface Science 253, n^o 9 (février 2007) : 4176–81. http://dx.doi.org/10.1016/j.apsusc.2006.09.020.

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Patel, Hasmukh S., et Nilesh P. Patel. « Poly(Amido-Imide)s Based on Amino-Terminated Oligoimides ». High Performance Polymers 9, n^o 1 (mars 1997) : 33–39. http://dx.doi.org/10.1088/0954-0083/9/1/003.

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An amino-terminated oligoimide was prepared by Michael addition reaction of N, N′-1, 4-phenylene bismaleimide (PBM) and 4, 4′-diamino-diphenyl methane (DDM) at a PBM–DDM ratio of 1:2. The poly(amido-imide)s (PAIs) were prepared by condensation of this PBM–DDM oligoimide with various aliphatic bisesters. The resultant PAIs were characterized by elemental analysis, IR spectral studies, number-average molecular weight ( Mn), estimated by nonaqueous conductometric titration, and thermogravimetry. The curing reaction of the epoxy resin–, namely diglycidyl ether of bisphenol-A (DGEBA)–, PAI system was monitored by differential scanning calorimetry (DSC). Based on cure temperature, the glass- and carbon-fibrereinforced composites (i.e. laminates) of the PAI–epoxy resin system have also been prepared and characterized.

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Kim, Taekyeong, et Tae Hyun Kim. « Measuring Conductance of Phenylenediamine as a Molecular Sensor ». Journal of Sensors 2015 (2015) : 1–6. http://dx.doi.org/10.1155/2015/353095.

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We report experimental measurements of molecular conductance as a single molecular sensor by using scanning tunneling microscope-based break-junction (STM-BJ) technique. The gap was created after Au atomic point contact was ruptured, and the target molecule was inserted and bonded to the top and bottom electrodes. We successfully measured the conductance for a series of amine-terminated oligophenyl molecules by forming the molecular junctions with Au electrodes. The measured conductance decays exponentially with molecular backbone length, enabling us to detect the type of molecules as a molecular sensor. Furthermore, we demonstrated reversible binary switching in a molecular junction by mechanical control of the gap between the electrodes. Since our method allows us to measure the conductance of a single molecule in ambient conditions, it should open up various practical molecular sensing applications.

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Nebel, Christoph E., Dongchan Shin, Bohuslav Rezek, Norio Tokuda, Hiroshi Uetsuka et Hideyuki Watanabe. « Diamond and biology ». Journal of The Royal Society Interface 4, n^o 14 (18 janvier 2007) : 439–61. http://dx.doi.org/10.1098/rsif.2006.0196.

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A summary of photo- and electrochemical surface modifications applied on single-crystalline chemical vapour deposition diamond films is given. The covalently bonded formation of amine and phenyl linker molecular layers is characterized using X-ray photoelectron spectroscopy, atomic force microscopy (AFM), cyclic voltammetry and field-effect transistor characterization experiments. Amine and phenyl layers are very different with respect to formation, growth, thickness and molecular arrangement. We deduce a sub-monolayer of amine linker molecules on diamond with approximately 10% coverage of 1.5×10 15 cm −2 carbon bonds. Amine is bonded only on initially H-terminated surface areas. In the case of electrochemical deposition of phenyl layers, multilayer properties are detected with three-dimensional nitrophenyl growth properties. This leads to the formation of typically 25 Å thick layers. The electrochemical bonding to boron-doped diamond works on H-terminated and oxidized surfaces. After reacting such films with heterobifunctional cross-linker molecules, thiol-modified ss-DNA markers are bonded to the organic system. Application of fluorescence and AFM on hybridized DNA films shows dense arrangements with densities up to 10 13 cm −2 . The DNA is tilted by an angle of approximately 35° with respect to the diamond surface. Shortening the bonding time of thiol-modified ss-DNA to 10 min causes a decrease in DNA density to approximately 10 12 cm −2 . Application of AFM scratching experiments shows threshold removal forces of approximately 75 and 45 nN for the DNA bonded to the phenyl and the amine linker molecules, respectively. First, DNA sensor applications using Fe(CN 6 ) 3−/4− mediator redox molecules and DNA field-effect transistor devices are introduced and discussed.

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Li, Kai, Zheng Li, Yong Shen, Xiaohui Fu, Chongyi Chen et Zhibo Li. « Organobase 1,1,3,3-tetramethyl guanidine catalyzed rapid ring-opening polymerization of α-amino acid N-carboxyanhydrides adaptive to amine, alcohol and carboxyl acid initiators ». Polymer Chemistry 13, n^o 5 (2022) : 586–91. http://dx.doi.org/10.1039/d1py01508g.

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For amine, hydroxyl and carboxyl terminated initiators, the organobase 1,1,3,3-tetramethylguanidine (TMG) catalyzes the rapid polymerization to afford polypeptides with controllable molecular weights and dispersities.

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Finstad, Casey C., et Anthony Muscat. « UV Activated Surface Preparation of Silicon for High-k Dielectric Deposition ». Solid State Phenomena 103-104 (avril 2005) : 7–10. http://dx.doi.org/10.4028/www.scientific.net/ssp.103-104.7.

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High-k gate materials, such as HfO2, are unstable on silicon and form low permittivity interfacial oxides when heated. A single layer of silicon nitride grown prior to gate dielectric deposition could serve as a diffusion barrier to prevent oxide formation. A monolayer film of surface amine groups will be chemically similar to surface hydroxyl groups, and could also serve as a seed layer to promote the nucleation of a high-k film. The deposition of amines (≡Si-NH2 or ≡Si-NH-Si≡) on chlorine and hydrogen terminated Si(100) at low temperature (<100°C) was investigated using x-ray photoelectron spectroscopy (XPS). UV-Cl2 exposures (0.1-10 Torr Cl2 at 25-150°C, 10-600 s, 1000 W Xe lamp) were used to terminate Si(100) with Cl atoms. Exposure to NH3 (0.1-1000 Torr, 75°C, 5-60 min) replaced Cl atoms with up to 0.3 ML of amine groups, as measured by XPS. Cl atoms served as reactive leaving groups, lowering the overall activation energy barrier for nitridation. Alternatively, UV photons with energy greater than 5.7 eV were used to photodissociate NH3 molecules, yielding NH2 photofragments that reacted with the H-terminated Si(100) surface. At a UV photon flux of 19 mW/cm2, the N coverage increased with time and saturated at ~1 ML. Significant oxygen was observed on the surface due to H2O contamination in the source gas.

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Shaya, O., I. Amit, H. Einati, L. Burstein, Y. Shacham-Diamand et Y. Rosenwaks. « Molecular gating of transistors by amine-terminated layers ». Applied Surface Science 258, n^o 8 (février 2012) : 4069–72. http://dx.doi.org/10.1016/j.apsusc.2011.12.102.

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Nebel, C. E., D. Shin, D. Takeuchi, T. Yamamoto, H. Watanabe et T. Nakamura. « Photochemical attachment of amine linker molecules on hydrogen terminated diamond ». Diamond and Related Materials 15, n^o 4-8 (avril 2006) : 1107–12. http://dx.doi.org/10.1016/j.diamond.2005.11.041.

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Liu, Yahao, Jian Zheng, Xiao Zhang, Yongqiang Du, Guibo Yu, Ke Li, Yunfei Jia et Yu Zhang. « Bioinspired modified graphene oxide/polyurethane composites with rapid self-healing performance and excellent mechanical properties ». RSC Advances 11, n^o 24 (2021) : 14665–77. http://dx.doi.org/10.1039/d1ra00944c.

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We successfully modified graphene oxide with amino-terminated hyperbranched polyamide(MGO), and obtained novel mussel-inspired MGO/polyurethane composites with outstanding self-healing and mechanical performances via rational molecular design.

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Meyerbroeker, N., P. Waske et M. Zharnikov. « Amino-terminated biphenylthiol self-assembled monolayers as highly reactive molecular templates ». Journal of Chemical Physics 142, n^o 10 (14 mars 2015) : 101919. http://dx.doi.org/10.1063/1.4907942.

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Xu, Chang-An, Bingfei Nan, Mangeng Lu, Zhencai Qu, Zhiyou Tan, Kun Wu et Jun Shi. « Effects of polysiloxanes with different molecular weights on in vitro cytotoxicity and properties of polyurethane/cotton–cellulose nanofiber nanocomposite films ». Polymer Chemistry 11, n^o 32 (2020) : 5225–37. http://dx.doi.org/10.1039/d0py00809e.

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A series of polyurethane/cotton–cellulose nanofiber nanocomposite films are manufactured using amino-terminated polydimethylsiloxane, polycarbonate diol, isophorone diisocyanate, and dispersed cotton–cellulose nanofibers.

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Pan, Xiaoyun, Cheng Qian, Amber Chow, Lu Wang et Maria Kamenetska. « Atomically precise binding conformations of adenine and its variants on gold using single molecule conductance signatures ». Journal of Chemical Physics 157, n^o 23 (21 décembre 2022) : 234201. http://dx.doi.org/10.1063/5.0103642.

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We demonstrate single molecule conductance as a sensitive and atomically precise probe of binding configurations of adenine and its biologically relevant variants on gold. By combining experimental measurements and density functional theory (DFT) calculations of single molecule–metal junction structures in aqueous conditions, we determine for the first time that robust binding of adenine occurs in neutral or basic pH when the molecule is deprotonated at the imidazole moiety. The molecule binds through the donation of the electron lone pairs from the imidazole nitrogen atoms, N7 and N9, to the gold electrodes. In addition, the pyrimidine ring nitrogen, N3, can bind concurrently and strengthen the overall metal–molecule interaction. The amine does not participate in binding to gold in contrast to most other amine-terminated molecular wires due to the planar geometry of the nucleobase. DFT calculations reveal the importance of interface charge transfer in stabilizing the experimentally observed binding configurations. We demonstrate that biologically relevant variants of adenine, 6-methyladenine and 2′-deoxyadenosine, have distinct conductance signatures. These results lay the foundation for biosensing on gold using single molecule conductance readout.

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Chen, Fang, Xiulan Li, Joshua Hihath, Zhifeng Huang et Nongjian Tao. « Effect of Anchoring Groups on Single-Molecule Conductance : Comparative Study of Thiol-, Amine-, and Carboxylic-Acid-Terminated Molecules ». Journal of the American Chemical Society 128, n^o 49 (décembre 2006) : 15874–81. http://dx.doi.org/10.1021/ja065864k.

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Ganesan, P. G., A. P. Singh et G. Ramanath. « Diffusion barrier properties of carboxyl- and amine-terminated molecular nanolayers ». Applied Physics Letters 85, n^o 4 (26 juillet 2004) : 579–81. http://dx.doi.org/10.1063/1.1775035.

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Nakamichi, Aina, et Jun-ichi Kadokawa. « Fabrication of Chitosan-Based Network Polysaccharide Nanogels ». Molecules 27, n^o 23 (1 décembre 2022) : 8384. http://dx.doi.org/10.3390/molecules27238384.

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In this study, we developed a method to fabricate chitosan-based network polysaccharides via the condensation between amino groups in water-soluble chitosan (WSCS) and a carboxylate-terminated maltooligosaccharide crosslinker. We previously reported on the fabrication of network-polysaccharide-based macroscopic hydrogels via the chemical crosslinking of water-soluble chitin (WSCh) with the crosslinker. Because the molecular weight of the WSCS was much smaller than that of the WSCh, in the present investigation, the chemical crosslinking of the WSCS with the crosslinker was observed at the nanoscale upon the condensation between amino and carboxylate groups in the presence of a condensing agent, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and N-hydroxysuccinimide, affording nano-sized chitosan-based network polysaccharides. The occurrence of the crosslinking via the formation of amido linkages was supported by the IR analysis and 1H NMR measurements after the dissolution via acid hydrolysis in DCl/D2O. The products formed nanogels, whose sizes depended on the amino/carboxylate feed ratio. The nanoscale morphology and size of the products were evaluated via scanning electron microscopy, dynamic light scattering analyses, and transition electron microscopy. In the present study, we successfully developed the method to fabricate nanogel materials based on network polysaccharide structures, which can practically be applied as new polysaccharide-based 3D bionanomaterials.

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Hukkamäki, Jarkko, et Tuula T. Pakkanen. « Study on catalytic hydrogenation in synthesis of four-directional amine-terminated dendritic molecules ». Journal of Molecular Catalysis A : Chemical 174, n^o 1-2 (octobre 2001) : 205–11. http://dx.doi.org/10.1016/s1381-1169(01)00173-x.

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Eves, Brian J, Chaoyang Fan et Gregory P Lopinski. « Sequential Reactions with Amine-Terminated Monolayers and Isolated Molecules on H/Si(111) ». Small 2, n^o 11 (novembre 2006) : 1379–84. http://dx.doi.org/10.1002/smll.200600103.

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Dasgupta, Sayani, Sharmishtha Samantaray, Dinkar Sahal et Rajendra P. Roy. « Isopeptide Ligation Catalyzed by Quintessential Sortase A ». Journal of Biological Chemistry 286, n^o 27 (12 mai 2011) : 23996–4006. http://dx.doi.org/10.1074/jbc.m111.247650.

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The housekeeping transpeptidase sortase A (SrtA) from Staphyloccocus aureus catalyzes the covalent anchoring of surface proteins to the cell wall by linking the threonyl carboxylate of the LPXTG recognition motif to the amino group of the pentaglycine cross-bridge of the peptidoglycan. SrtA-catalyzed ligation of an LPXTG containing polypeptide with an aminoglycine-terminated moiety occurs efficiently in vitro and has inspired the use of this enzyme as a synthetic tool in biological chemistry. Here we demonstrate the propensity of SrtA to catalyze “isopeptide” ligation. Using model peptide sequences, we show that SrtA can transfer LPXTG peptide substrates to the ϵ-amine of specific Lys residues and form cyclized and/or a gamut of branched oligomers. Our results provide insights about principles governing isopeptide ligation reactions catalyzed by SrtA and suggest that although cyclization is guided by distance relationship between Lys (ϵ-amine) and Thr (α-carboxyl) residues, facile branched oligomerization requires the presence of a stable and long-lived acyl-enzyme intermediate.

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Zhao, Xiao Fei, De Nan Wu, Chun Xi Ma, Li Xin Liu, Jun Tao Du et Su Min Liu. « Synthesis of a Novel Cationic Polyacrylamide and Its Application in Flocculation ». Advanced Materials Research 311-313 (août 2011) : 1124–27. http://dx.doi.org/10.4028/www.scientific.net/amr.311-313.1124.

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In the flocculation treatment of oilfield sewage, cationic polyacrylamide (CPAM), which was synthesized by the copolymerization of dimethyldiallylammonium chloride (DMDAAC), acrylamide(AM), and acrylic acid(AA), will react with the residue of oil displacement agent, causing the quick crimp of its linear-molecular-structure chain and deteriorating the flocculating effects. In order to solve the problem, cationic polyacrylamide (CPAM) was grafted by a cationic-terminated spheroidal-molecular-structure hyperbranched polymer (CHP), which was synthesized by introducing methacryloxyethyl trimethylammonium chloride (DMC) into a kind of amino-terminated hyperbranched polymer. Both CPAM and grafted CPAM were used in flocculation treatment of simulated ASP oilfield sewage. The comparison results in flocculating effects indicated that the flocculating effect of grafted CPAM is greater than CPAM, its optimal dosage is 12.5mg/L, and its transmittance of the treated sewage reached 98.6%.

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Yang, Kui, Elizabeth Wills et Joel D. Baines. « The Putative Leucine Zipper of the UL6-Encoded Portal Protein of Herpes Simplex Virus 1 Is Necessary for Interaction with pUL15 and pUL28 and Their Association with Capsids ». Journal of Virology 83, n^o 9 (18 février 2009) : 4557–64. http://dx.doi.org/10.1128/jvi.00026-09.

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ABSTRACT Herpes simplex virus (HSV) type 1 capsids contain a single portal vertex that is composed of 12 copies of the UL6 gene product (pUL6), which forms a pore through which DNA is inserted during packaging. This unique vertex is also believed to comprise the site with which a molecular motor, termed the terminase, associates during the DNA packaging reaction. In HSV, the terminase likely comprises the UL15, UL28, and UL33 proteins (pUL15, pUL28, and pUL33, respectively). The current study was undertaken to identify portal domains required for interaction with the terminase. Both the amino and carboxyl termini, as well as amino acids 422 to 443 of pUL6 forming a putative leucine zipper motif, were critical for coimmunoprecipitation with pUL15 in the absence of other viral proteins. Amino acids 422 to 443 were also necessary for interaction with pUL28 in the absence of other viral proteins. By using an engineered recombinant virus, it was further determined that although amino acids 422 to 443 were dispensable for interaction with scaffold protein and incorporation of portal protein into capsids, they were necessary for coimmunoprecipitation of pUL6 and pUL15 from infected cell lysates, association of optimal levels of pUL15, pUL28, and pUL33 with capsids, and DNA cleavage and packaging. These data identify a portal protein domain critical for terminase association with the capsid and suggest that both the pUL15- and pUL28-bearing terminase subunits mediate docking of the terminase with the portal vertex.

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Balakrishnan, AbhayRam, Rahul Suresh et S. Vijayakumar. « Amine terminated polyynes as candidates for molecular wire applications : A DFT study ». Physica E : Low-dimensional Systems and Nanostructures 137 (mars 2022) : 115045. http://dx.doi.org/10.1016/j.physe.2021.115045.

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Suemori, Yoshiharu, Kaoru Fujii, Makiko Ogawa, Yukari Nakamura, Kiyoshi Shinohara, Katsunori Nakagawa, Morio Nagata et al. « Molecular assembly of artificial photosynthetic antenna core complex on an amino-terminated ITO electrode ». Colloids and Surfaces B : Biointerfaces 56, n^o 1-2 (avril 2007) : 182–87. http://dx.doi.org/10.1016/j.colsurfb.2006.10.029.

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Patel, Rita R., et Mukesh C. Patel. « Novel Interecting Blends Based on Amino Terminited Oligoimides by Using Michael Addition Reaction-II ». E-Journal of Chemistry 9, n^o 4 (2012) : 1960–67. http://dx.doi.org/10.1155/2012/687540.

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New amino terminated oligoimides (AOIs) were prepared by the Michael addition reaction of various bismaleimide (1), namely, 1-(4-((4-((2, 5-dioxocyclopent-3 enylamino) methyl) cyclohexyl) methyl) cyclohexyl)-1, 6-dihydropyridine-2, 5-dione with excess of various diamines (2a-c). These AOIs were characterized by elemental analysis, FT-IR spectral studies and number average molecular weight estimated by non-aqueous conductometric titrations. AOIs were then treated with acrylol chloride and resultant acryl terminated oligoimides (AcOIs) samples were also characterized thermogravimetrically. Each of these AcOI was then combined with theN-phenyl maleimide (PM) in THF solvent. The resultant suspensions were then heated in the presence of azobisisobutyronitrile (AIBN) as an initiator. The AcOI and PM polymerized through double bond simultaneously and form interacting blends, which were analyzed thermogravimetrically. The glass fiber reinforced composites were fabricated by using the suspensions of the AcOI and PM. The composites of Interacting blends were analyzed for their mechanical, chemical and electrical properties.

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Berman, Neil J., James Plant, Ray W. Turner et Leonard Maler. « Excitatory Amino Acid Receptors at a Feedback Pathway in the Electrosensory System : Implications for the Searchlight Hypothesis ». Journal of Neurophysiology 78, n^o 4 (1 octobre 1997) : 1869–81. http://dx.doi.org/10.1152/jn.1997.78.4.1869.

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Berman, Neil J., James Plant, Ray W. Turner, and Leonard Maler. Excitatory amino acid receptors at a feedback pathway in the electrosensory system: implications for the searchlight hypothesis. J. Neurophysiol. 78: 1869–1881, 1997. The electrosensory lateral line lobe (ELL) of the South American gymnotiform fish Apteronotus leptorhynchus has a laminar structure: electroreceptor afferents terminate ventrally whereas feedback input distributes to a superficial molecular layer containing the dendrites of the ELL principle (pyramidal) cells. There are two feedback pathways: a direct feedback projection that enters the ELL via a myelinated tract (stratum fibrosum, StF) and terminates in the ventral molecular layer (VML) and an indirect projection that enters as parallel fibers and terminates in the dorsal molecular layer. It has been proposed that the direct feedback pathway serves as a “searchlight” mechanism. This study characterizes StF synaptic transmission to determine whether the physiology of the direct feedback projection is consistent with this hypothesis. We used field and intracellular recordings from the ELL to investigate synaptic transmission of the StF in an in vitro slice preparation. Stimulation of the StF produced field potentials with a maximal negativity confined to a narrow band of tissue dorsal to the StF. Current source density analysis revealed two current sinks: an early sink within the StF and a later sink that corresponded to the anatomically defined VML. Field potential recordings from VML demonstrated that stimulation of the StF evoked an excitatory postsynaptic potential (EPSP) that peaked at a latency of 4–7 ms with a slow decay (∼50 ms) to baseline. Intracellular recordings from pyramidal cells revealed that StF-evoked EPSPs consisted of at least two components: a fast gap junction mediated EPSP (peak 1.2–1.8 ms) and a chemical synaptic potential (peak 4–7 ms) with a slow decay phase (∼50 ms). The amplitudes of the peak and decay phases of the chemical EPSP were increased by depolarizing current injection. Pharmacological studies demonstrated that the chemical EPSP was mainly due to ionotropic glutamate receptors with both N-methyl-d-aspartate (NMDA) and non-NMDA components. NMDA receptors contributed substantially to both the early and late phase of the EPSP, whereas non-NMDA receptors contributed mainly to the early phase. Stimulation of the StF at physiological rates (100–200 Hz, 100 ms) produced an augmenting depolarization of the membrane potential of pyramidal cells. Temporal summation and a voltage-dependent enhancement of later EPSPs in the stimulus train permitted the compound EPSP to reach spike threshold. The nonlinear behavior of StF synaptic potentials is appropriate for the putative role of the direct feedback pathway as part of a searchlight mechanism allowing these fish to increase the electrodetectability of scanned objects.

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Tanaka, Yuta, Yuh Matsuo, Haruka Saito, Yusuke Tsutsumi, Hisashi Doi, Takayuki Yoneyama, Hachiro Imai et Takao Hanawa. « Biofunctionalization of Metal Surface by Immobilization of Poly(Ethylene Glycol) Terminated Amine ». Advanced Materials Research 26-28 (octobre 2007) : 765–68. http://dx.doi.org/10.4028/www.scientific.net/amr.26-28.765.

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In many biomedical devices such as catheters and diagnostic sensors, blood compatibility is required. The best way to control this property is to prevent or drastically reduce the adsorption of proteins. Poly(ethylene glycol) terminated amine at both terminals, NH2-PEG-NH2, is immobilized on a commercially pure titanium, a 316L austenitic stainless steel, and a cobalt-chromium-molybdenum alloy with immersion or electrodeposition. Chemical bonding states at the interface and orientation of PEG molecules were characterized using X-ray photoelectron spectroscopy, glow discharge optical emission spectroscopy, and Fourie-transformed infrared spectrometer with a reflection absorption spectrometer. As a result, NH2-PEG-NH2 was immobilized onto metal surface as a U-shape mainly with stable NHO bonding in electrodeposition. In the case of electrodepostion, the concentration of active surface hydroxyl groups on surface oxide film played an important role in the immobilization.

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Kim, Deok Hyeon, et Taekyeong Kim. « Tight-binding model for amine-terminated oligophenyl molecular junctions formed with carbon electrodes ». Journal of the Korean Physical Society 66, n^o 10 (mai 2015) : 1499–502. http://dx.doi.org/10.3938/jkps.66.1499.

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Chen, Ling, De Suo Zhang, Hong Lin et Yu Yue Chen. « A Study of Antimicrobial Property of Oxidized Cotton Fabric Finished with Amino-Terminated Hyperbranched Polymer ». Advanced Materials Research 175-176 (janvier 2011) : 640–45. http://dx.doi.org/10.4028/www.scientific.net/amr.175-176.640.

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The chief aim of the present work is to investigate the preparation for silver nanoparticles antimicrobial agent and its antibacterial activity on cotton fabric. In this study, antimicrobial agent was fabricated by a reaction between an amino-terminated hyperbranched polymer (HBP-NH2) and silver nitrate solution of certain concentration. Meanwhile, cotton fabric was oxygenated to afford aldehyde groups which could connect with the amino groups of the HBP-NH2 to provide cotton fabric with durable antimicrobial properties. The effects of different biocides made of various molecular structures of synthetic material (HBP-NH2) on antimicrobial properties of nano-silver colloid solution were discussed, and three different agents generated then were characterized in following aspects as silver nanoparticles size and distribution by using DLS, TEM and UV-vis. Furthermore, the fabric structure, mechanical properties and antimicrobial property of treated cotton fabric were also tested. Included in this part of experiment were transverse micro morphology of cotton fibre by SEM, fabric strength retention after finishing, silver nanoparticles molecular conformation on fabric and content analysis via ICP-AES. The results showed that stable silver nanoparticles collide solution with 20-30 nano, applied on oxidized cotton fabric under certain condition, could produce ideal antibacterial rate over 94% of bacterial reduction to both Staphylococcus aureus (S.aureus) and Escherichia coli (E.coli) after 50 consecutive washings.

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Crews, Kristy, Crystal Reeves, Porsha Thomas, Daniel Abugri, Albert Russell et Michael L. Curry. « Heterogeneous Catalysis of C–O Bond Cleavage for Cellulose Deconstruction : A Potential Pathway for Ethanol Production ». ISRN Nanotechnology 2014 (20 février 2014) : 1–8. http://dx.doi.org/10.1155/2014/634679.

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Due to difficulty deconstructing the linkages between lignin, hemicellulose and cellulose during the conversion of cellulose to sugar, the commercial production of cellulosic ethanol is limited. This can be overcome by using a high surface-area metal catalyst. In this study, high surface-area metal NPs were synthesized using 20 mM of chloroplatinic acid and cobalt chloride prepared in THF with 0.1 mM of generation four poly(amido)amine (PAMAM) terminated dendrimer (G4-NH2) prepared in methanol and stirred for 2 hours under nitrogen. Subsequently, Pt+2 and Co+2 ions were reduced to metal zero via introduction of sodium borohydride and centrifuged for complete separation. The resulting product was heated for 2.5 hours at ~200°C. After cooling, 2.0 grams of crushed peanut shells was added to 40 mL of distilled tert-butyl methyl ether along with the separated metal nanocatalyst and refluxed on condenser at 20% for 24 hours. UV-Vis and XRD analyses show the formation of Pt and Co nanoparticles using dendrimer templating methodology. Both TLC and HPLC show that, upon introduction of the metal catalyst into the suspension of “cellulose” in TBME, separation of the cellulose into small molecules is evident. That is, release of sugar molecules via C–O bond cleavage is facilitated by the formed nanocatalysts.

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Nasir, Saima, Mubarak Ali et Wolfgang Ensinger. « Thermally controlled permeation of ionic molecules through synthetic nanopores functionalized with amine-terminated polymer brushes ». Nanotechnology 23, n^o 22 (10 mai 2012) : 225502. http://dx.doi.org/10.1088/0957-4484/23/22/225502.

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Ren, Longfang, Guohui Zhao, Taotao Qiang, Xuechuan Wang et Na Wang. « Synthesis of amino-terminated hyperbranched polymers and their application in microfiber synthetic leather base dyeing ». Textile Research Journal 83, n^o 4 (22 novembre 2012) : 381–95. http://dx.doi.org/10.1177/0040517512467134.

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In the current study, amino-terminated hyperbranched polymers (NH2-HBP) were synthesized by Michael addition reaction in which N, N’-methylene bisacrylamide (MBA) and diethylene triamine (DETA) were used as raw materials, and water was used as a solvent. Reaction temperature, raw material ratio, and reaction time were optimized via single-factor experiments in which the production rate and primary amino content were used as indexes. The results showed that the mol ratio of MBA to DETA was 1:1.1, the temperature was 70°C, and reaction time was 24 h. Under this condition, the primary amino content of NH2-HBP was 2.83 mmol/g, and the yield was 91.16%. The NH2-HBP structure was characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance. Moreover, the relative molecular mass distribution of NH2-HBP was also determined by gel permeation chromatography. As an active substance, NH2-HBP was grafted onto the polyamide microfiber synthetic leather used in clothes, and organic phosphine was used as a cross-linking agent. The change in dye uptake, surface chroma, and resistance to dry-rub and wet-rub fastness properties was discussed. When the NH2-HBP dosage was 5.5%, the dye uptake improved from 56.89% to 94.85% (an increase of almost 61%). The surface chroma also deepened, the dry-rub fastness improved from 3.0 to 4.5, and the wet-rub fastness improved from 2.5 to 3.5.

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Kodr, David, Jarmila Stanková, Michaela Rumlová, Petr Džubák, Jiří Řehulka, Tomáš Zimmermann, Ivana Křížová et al. « Betulinic Acid Decorated with Polar Groups and Blue Emitting BODIPY Dye : Synthesis, Cytotoxicity, Cell-Cycle Analysis and Anti-HIV Profiling ». Biomedicines 9, n^o 9 (28 août 2021) : 1104. http://dx.doi.org/10.3390/biomedicines9091104.

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Betulinic acid (BA) is a potent triterpene, which has shown promising potential in cancer and HIV-1 treatment. Here, we report a synthesis and biological evaluation of 17 new compounds, including BODIPY labelled analogues derived from BA. The analogues terminated by amino moiety showed increased cytotoxicity (e.g., BA had on CCRF-CEM IC50 > 50 μM, amine 3 IC50 0.21 and amine 14 IC50 0.29). The cell-cycle arrest was evaluated and did not show general features for all the tested compounds. A fluorescence microscopy study of six derivatives revealed that only 4 and 6 were detected in living cells. These compounds were colocalized with the endoplasmic reticulum and mitochondria, indicating possible targets in these organelles. The study of anti-HIV-1 activity showed that 8, 10, 16, 17 and 18 have had IC50i > 10 μM. Only completely processed p24 CA was identified in the viruses formed in the presence of compounds 4 and 12. In the cases of 2, 8, 9, 10, 16, 17 and 18, we identified not fully processed p24 CA and p25 CA-SP1 protein. This observation suggests a similar mechanism of inhibition as described for bevirimat.

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Ju, Mingjie, Feirong Gong, Shujun Cheng et Yun Gao. « Fast and Convenient Synthesis of Amine-Terminated Polylactide as a Macroinitiator forω-Benzyloxycarbonyl-L-Lysine-N-Carboxyanhydrides ». International Journal of Polymer Science 2011 (2011) : 1–7. http://dx.doi.org/10.1155/2011/381076.

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Amine-terminated poly (L-lactide) (NH2-PLLA) with various chain lengths were successfully synthesized by sequential tert-butyl-N-(3-hydroxypropyl) carbamate initiated bulk ring-opening polymerization (ROP) of L-lactide (L-LA) in the presence of Stannous(II) 2-ethylhexanoate (Sn(Oct)2) and deprotection of theN-tert-butoxycarbonyl (Boc) group at the end of the polymer chain. The polymers obtained were characterized by FT-IR,1H NMR, and GPC method. NH2-PLLA thus prepared was used to initiate the polymerization of ω-benzyloxycarbonyl-L-lysine-N-carboxyanhydride (Lys (Z)-NCA), and the result confirmed the high nucleophilicity of the terminal amine group. This method was not only suitable for the preparation of low molecular weight NH2-PLLA, but also quite efficient in the synthesis of high molecular weight samples.

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Lambert, Christoph, et Volker Kriegisch. « Heterogeneous Electron Transfer Processes in Self-Assembled Monolayers of Amine Terminated Conjugated Molecular Wires ». Langmuir 22, n^o 21 (octobre 2006) : 8807–12. http://dx.doi.org/10.1021/la061404t.

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Casjens, Sherwood R., Eddie B. Gilcrease, Danella A. Winn-Stapley, Petra Schicklmaier, Horst Schmieger, Marisa L. Pedulla, Michael E. Ford, Jennifer M. Houtz, Graham F. Hatfull et Roger W. Hendrix. « The Generalized Transducing Salmonella Bacteriophage ES18 : Complete Genome Sequence and DNA Packaging Strategy ». Journal of Bacteriology 187, n^o 3 (1 février 2005) : 1091–104. http://dx.doi.org/10.1128/jb.187.3.1091-1104.2005.

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ABSTRACT The generalized transducing double-stranded DNA bacteriophage ES18 has an icosahedral head and a long noncontractile tail, and it infects both rough and smooth Salmonella enterica strains. We report here the complete 46,900-bp genome nucleotide sequence and provide an analysis of the sequence. Its 79 genes and their organization clearly show that ES18 is a member of the lambda-like (lambdoid) phage group; however, it contains a novel set of genes that program assembly of the virion head. Most of its integration-excision, immunity, Nin region, and lysis genes are nearly identical to those of the short-tailed Salmonella phage P22, while other early genes are nearly identical to Escherichia coli phages λ and HK97, S. enterica phage ST64T, or a Shigella flexneri prophage. Some of the ES18 late genes are novel, while others are most closely related to phages HK97, lambda, or N15. Thus, the ES18 genome is mosaically related to other lambdoid phages, as is typical for all group members. Analysis of virion DNA showed that it is circularly permuted and about 10% terminally redundant and that initiation of DNA packaging series occurs across an approximately 1-kbp region rather than at a precise location on the genome. This supports a model in which ES18 terminase can move substantial distances along the DNA between recognition and cleavage of DNA destined to be packaged. Bioinformatic analysis of large terminase subunits shows that the different functional classes of phage-encoded terminases can usually be predicted from their amino acid sequence.

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LeVine, Michael V., Daniel S. Terry, George Khelashvili, Zarek S. Siegel, Matthias Quick, Jonathan A. Javitch, Scott C. Blanchard et Harel Weinstein. « The allosteric mechanism of substrate-specific transport in SLC6 is mediated by a volumetric sensor ». Proceedings of the National Academy of Sciences 116, n^o 32 (19 juillet 2019) : 15947–56. http://dx.doi.org/10.1073/pnas.1903020116.

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Neurotransmitter:sodium symporters (NSSs) in the SLC6 family terminate neurotransmission by coupling the thermodynamically favorable transport of ions to the thermodynamically unfavorable transport of neurotransmitter back into presynaptic neurons. Results from many structural, functional, and computational studies on LeuT, a bacterial NSS homolog, have provided critical insight into the mechanism of sodium-coupled transport, but the mechanism underlying substrate-specific transport rates is still not understood. We present a combination of molecular dynamics simulations, single-molecule fluorescence resonance energy transfer (smFRET) imaging, and measurements of Na+ binding and substrate transport that reveals an allosteric substrate specificity mechanism. In this mechanism, residues F259 and I359 in the substrate binding pocket couple the binding of substrate to Na+ release from the Na2 site by allosterically modulating the stability of a partially open, inward-facing state. We propose a model for transport selectivity in which residues F259 and I359 act as a volumetric sensor that inhibits the transport of bulky amino acids.

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Tang, Li-ming, Ji Feng et Yu Wang. « INFLUENCE OF MOLECULAR STRUCTURES OF SECONDARY AMINE TERMINATED POLY(ESTER-AMINE)S ON THE CURING PERFORMANCE WITH EPOXY RESIN ». Chinese Journal of Polymer Science 25, n^o 06 (2007) : 545. http://dx.doi.org/10.1142/s025676790700245x.

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Mian, Shabeer Ahmad, et Younas Khan. « The Adhesion Mechanism of Marine Mussel Foot Protein : Adsorption of L-Dopa onα- and β-Cristobalite Silica Using Density Functional Theory ». Journal of Chemistry 2017 (2017) : 1–6. http://dx.doi.org/10.1155/2017/8756519.

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Marine mussels strongly adhere to various surfaces and endure their attachment under a variety of conditions. In order to understand the basic mechanism involved, we study the adsorption of L-dopa molecule on hydrophilic geminal and terminal isolated silanols of silica (001) surface. High content of modified amino acid L-dopa is found in the glue-like material secreted by the mussels through which it sticks to various surfaces under water. To understand the adsorption behavior, we have made use of periodic Density Functional Theory (DFT) study. The L-dopa molecule adheres to silica surfaces terminated with geminal and terminal silanols via its catechol part. In both cases, the adhesion is achieved through the formation of 4 H-bonds. A binding energy of 29.48 and 31.67 kcal/mol has been estimated, after the inclusion of dispersion energy, for geminal and terminal silanols of silica, respectively. These results suggest a relatively stronger adhesion of dopa molecule for surface with terminal isolated silanols.

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