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Crystal structures of peptide enantiomers and racemates: Probing conformational diversity in heterochiral Pro‐Pro sequences
Author(s) -
Saha Indranil,
Chatterjee Bhaswati,
Shamala Narayanaswamy,
Balaram Padmanabhan
Publication year - 2008
Publication title -
peptide science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.20982
Subject(s) - chemistry , enantiomer , peptide , diversity (politics) , stereochemistry , functional diversity , crystal (programming language) , crystallography , biochemistry , ecology , sociology , anthropology , computer science , biology , programming language
Multiple conformational states in heterochiral diproline sequences have been characterized in the solid state by the determination of the crystal structures of seven tripeptides in enantiomeric and racemic forms. The sequences of the type Piv‐ D Pro‐ L Pro‐ D Xxx‐NHMe ( D‐L‐D ) [ D Xxx = D Val 1, D Leu 3, and D Phe 5] and their corresponding enatiomeric L‐D‐L sequences [ L Xxx = L Val 2, L Leu 4, and L Phe 6] have been investigated. Single crystals have been obtained for the pure enantiomers 1, 2, 3, 4 and for the racemates 1/2, 3/4, and 5/6. For Xxx = Leu, mirror image conformations (type II/II′ β‐turns) at Pro‐Leu segment are obtained. For Xxx = Val, a L Pro‐ D Pro type II β‐turn in 2 and an open/extended structure is obtained in the solvated form of the enantiomer 1. For Xxx = Phe, suitable crystals could not be obtained for enatiomeric peptides. The racemate 5/6 revealed a cis peptide bond between the diproline segment with the absence of any intramolecular hydrogen bonds. Crystal structures of enantiomers and racemates prove useful in characterizing the multiple conformational states that are accessible to Pro‐Pro segments. © 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 90: 537–543, 2008. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com