Peptides and amino acid structures

Date:: 1941-1959

Reference:: PP/CRI/H/2/35

Credit: Peptides and amino acid structures. Source: Wellcome Collection.

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$[Contribution from the Gates and Crellin Laboratorio of Chemistry, California Insiitute The Crystal Structure of ¿//-Alanine By Henri A. Levy and Robert B. Corey Introduction The determination of the crystal structure of ¿/-alanine was undertaken as a continuation of X-ray diffraction studies which are a part of a program of research upon the constitution and configuration of proteins. In earlier investigations the structures of crystals of diketopiperazine 1 and of glycine 2 'were determined and the interatomic distances and bond angles of their molecules thereby established. Definite data were thus made available for the construction of a tenta tive model of the polypeptide chain. In discus sions of these data 1,2 and in a more recent con sideration of their application to the problem of the configuration of the polypeptide chain 8 in pro tein molecules the presence of certain anomalies among the interatomic distances found in glycine and in its cyclic anhydride have been mentioned. Thus in both of these compounds a C-N distance near 1.40 Á. is found which is shorter than that predicted from the covalent radii (1.47 Â.). In diketopiperazine the C-C distance, 1.47 Â., is surprisingly short compared to that which might be anticipated (1.54 Â.); however, in glycine the distance 1.52 Â. is in agreement with the normal$

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Peptides and amino acid structures

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