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Alpha-Amino Acid
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Thomas R M Barends – One of the best experts on this subject based on the ideXlab platform.
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Acetobacter turbidans Alpha-Amino Acid ester hydrolase: merohedral twinning in P21 obscured by pseudo-translational NCS.
Acta crystallographica. Section D Biological crystallography, 2003Co-Authors: Thomas R M Barends, Bauke W. DijkstraAbstract:The structure elucidation of the Alpha-Amino Acid ester hydrolase from Acetobacter turbidans by molecular replacement is described. In the monoclinic crystal, the molecules are related by both rotational and pseudo-crystallographic translational NCS (non-crystallographic symmetry). Refinement of the structure converged at unacceptably high R factors. After re-evaluation of the data, it was found that the crystal was merohedrally twinned, with a high twinning fraction. It is shown that the pseudo-crystallographic NCS causes aberrant behaviour of conventional twinning indicators, which explains why the twinning was only realized at the refinement stage.
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Acetobacter turbidans Alpha-Amino Acid ester hydrolase
Acta Crystallographica Section D Biological Crystallography, 2003Co-Authors: Thomas R M Barends, Bauke W. DijkstraAbstract:The structure elucidation of the Alpha-Amino Acid ester hydrolase from Acetobacter turbidans by molecular replacement is described. In the monoclinic crystal, the molecules are related by both rotational and pseudo-crystallographic translational NCS (non-crystallographic symmetry). Refinement of the structure converged at unacceptably high R factors. After re-evaluation of the data, it was found that the crystal was merohedrally twinned, with a high twinning fraction. It is shown that the pseudo-crystallographic NCS causes aberrant behaviour of conventional twinning indicators, which explains why the twinning was only realized at the refinement stage.
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the sequence and crystal structure of the alpha amino Acid ester hydrolase from xanthomonas citri define a new family of beta lactam antibiotic acylases
Journal of Biological Chemistry, 2003Co-Authors: Thomas R M Barends, Jolanda Polderman Tijmes, Peter A Jekel, Cmh Hensgens, Erik De Vries, Dick B. Janssen, Bebauke W DijkstraAbstract:Abstract α-Amino Acid ester hydrolases (AEHs) catalyze the hydrolysis and synthesis of esters and amides with an α-amino group. As such, they can synthesize β-lactam antibiotics from acyl compounds and β-lactam nuclei obtained from the hydrolysis of natural antibiotics. This article describes the gene sequence and the 1.9-A resolution crystal structure of the AEH from Xanthomonas citri. The enzyme consists of an α/β-hydrolase fold domain, a helical cap domain, and a jellyroll β-domain. Structural homology was observed to the Rhodococcus cocaine esterase, indicating that both enzymes belong to the same class of bacterial hydrolases. Docking of a β-lactam antibiotic in the active site explains the substrate specificity, specifically the necessity of an α-amino group on the substrate, and explains the low specificity toward the β-lactam nucleus.
Leslie Leiserowitz – One of the best experts on this subject based on the ideXlab platform.
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separation of enantiomers and racemate formation in two dimensional crystals at the water surface from racemic alpha amino Acid amphiphiles design and structure
Journal of the American Chemical Society, 1997Co-Authors: Isabelle Weissbuch, Maria Berfeld, Wim G Bouwman, Kristian Kjaer, J Alsnielsen, Meir Lahav, Leslie LeiserowitzAbstract:Studies are presented on the two-dimensional (2-D) crystalline packing arrangements of enantiomerically pure and racemic α-amino Acid RHC(NH3+)CO2- monolayers on water and on glycine aqueous solutions, as determined by synchrotron grazing incidence X-ray diffraction. The amphiphiles have been designed such that their racemic mixtures form 2-D crystals which are either heterochiral (for R = CnH2n+1−, n = 10, 12, 16) due to the tendency for herringbone chain arrangements via glide symmetry or homochiral (for R = CnH2n+1CONH(CH2)4−, n = 11, 17, 21) by virtue of hydrogen bonding by translation of the amide group in the chains leading to a spontaneous separation into islands of opposite chirality. The two different crystalline motifs led to a correlation between their packing arrangements and induced oriented nucleation of 3-D crystals of α-glycine by these monolayers. The relevance of the present results to the possibility of ordering and spontaneous segregation of racemates of the natural hydrophobic α-amino…
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The role of crystal polarity in Alpha-Amino Acid crystals for induced nucleation of ice
Science (New York N.Y.), 1992Co-Authors: Moshe Gavish, J. L. Wang, M Eisenstein, Michal Lahav, Leslie LeiserowitzAbstract:The hydrophobic faces of single crystals of a series of pairs of racemic and chiral-resolved hydrophobic Alpha-Amino Acids were used as a substrate, onto which water vapor has been cooled to freezing. The morphologies and molecular packing arrangements within each crystal pair are similar but only one of each pair exhibits a polar axis, parallel to the hydrophobic face exposed to water. Those crystals that have a polar axis induce a freezing point higher by 4 degrees to 5 degrees C than the corresponding crystals that do not have a polar axis. The results are interpreted in terms of an electric field mechanism that helps align the water molecules into ice-like clusters en route to crystallization.
Bauke W. Dijkstra – One of the best experts on this subject based on the ideXlab platform.
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Acetobacter turbidans Alpha-Amino Acid ester hydrolase
Acta Crystallographica Section D Biological Crystallography, 2003Co-Authors: Thomas R M Barends, Bauke W. DijkstraAbstract:The structure elucidation of the Alpha-Amino Acid ester hydrolase from Acetobacter turbidans by molecular replacement is described. In the monoclinic crystal, the molecules are related by both rotational and pseudo-crystallographic translational NCS (non-crystallographic symmetry). Refinement of the structure converged at unacceptably high R factors. After re-evaluation of the data, it was found that the crystal was merohedrally twinned, with a high twinning fraction. It is shown that the pseudo-crystallographic NCS causes aberrant behaviour of conventional twinning indicators, which explains why the twinning was only realized at the refinement stage.
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Acetobacter turbidans Alpha-Amino Acid ester hydrolase: merohedral twinning in P21 obscured by pseudo-translational NCS.
Acta crystallographica. Section D Biological crystallography, 2003Co-Authors: Thomas R M Barends, Bauke W. DijkstraAbstract:The structure elucidation of the Alpha-Amino Acid ester hydrolase from Acetobacter turbidans by molecular replacement is described. In the monoclinic crystal, the molecules are related by both rotational and pseudo-crystallographic translational NCS (non-crystallographic symmetry). Refinement of the structure converged at unacceptably high R factors. After re-evaluation of the data, it was found that the crystal was merohedrally twinned, with a high twinning fraction. It is shown that the pseudo-crystallographic NCS causes aberrant behaviour of conventional twinning indicators, which explains why the twinning was only realized at the refinement stage.