The configurations of the amino acids in pneumococcal C-polysaccharide have been determined chromatographically after acid hydrolysis. The amino acids were coupled with an L-amino acid N-carboxyanhydride for formation of the corresponding L-Dand L-L-dipeptides; these derivatives were separated by ion exchange chromatography on an amino acid analyzer. The amount of racemization of alanine which ...

We developed an efficient, stereoselective synthetic method for the diketopiperazine moiety of neoechinulin A and its derivatives. The intramolecular cyclization at 80 ºC proceeded with minimal racemization of the stereogenic center at C-12 on neoechinulin A, even though the cyclization at 110 ºC caused partial racemization. In contrast with these results, the cyclization on diketopiperazine of...

The recent paper by Huang and Davisson (J. Bacteriol., 76, 495, 1958) on the distribution of lysine racemase in bacteria reports its occurrence in only a few species of Escherichia and Proteus. Various other bacteria including 22 strains of various genera of the Pseudomonadaceae did not possess such activity. I wish to report evidence for the occurrence of lysine racemase activity in a Pseudomo...

D-Amino acids have been shown to play an increasingly diverse role in bacterial physiology, yet much remains to be learned about their synthesis and catabolism. Here we used the model soil- and rhizosphere-dwelling organism Pseudomonas putida KT2440 to elaborate on the genomics and enzymology of d-amino acid metabolism. P. putida KT2440 catabolized the d-stereoisomers of lysine, phenylalanine, ...

Thiolate-protected gold nanoparticles and clusters combine size-dependent physical properties with the ability to introduce (bio)chemical functionality within their ligand shell. The engineering of the latter with molecular precision is an important prerequisite for future applications. A key question in this respect concerns the flexibility of the gold-sulfur interface. Here we report the firs...

Racemases catalyse the inversion of stereochemistry in biological molecules, giving the organism the ability to use both isomers. Among them, lactate racemase remains unexplored due to its intrinsic instability and lack of molecular characterization. Here we determine the genetic basis of lactate racemization in Lactobacillus plantarum. We show that, unexpectedly, the racemase is a nickel-depen...

Investigation of amino acids in fossils over the past thirty years has revealed that residual amino acids may exist in fossils from throughout the Phanerozoic portion of the geologic column, that the amino acid pattern in a given fossil changes with age due to differences in stability among the twenty amino acids of which proteins are constructed, and that the ratio of right-handed to left-hand...

Attrition-enhanced chiral symmetry breaking in crystals, also known as Viedma ripening, is a remarkable phenomenon from a variety of perspectives. By providing a direct route to solid-phase homochirality in a controllable manner, it is of inherent interest to those who study chiral symmetry-breaking/amplification mechanisms. When applied to intrinsically chiral molecules, Viedma ripening may ha...

Dual promiscuous racemization/amidation activities of lipases leading to efficient dynamic kinetic resolution protocols of racemic α-aminonitrile compounds are described. α-Amidonitrile products of high enantiomeric purity could be formed in high yields. Several lipases from different sources were shown to exhibit the dual catalytic activities, where opposite enantioselectivities could be recor...

Synthesis is described of bradykinyl-Val-Ala-Pro-Ala-Ser-OH.All the fragment condensations were carried out by Rudinger's azide method in order to minimize the racemization during the coupling steps involving peptide fragments.The ensuing tetradecapeptide with a high degree of homogeneity was found to be identical with bradykinyl-ValAla-Pro-Ala-Ser-OH of natural origin with respect to chemical ...