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Intramolecular CH···O Hydrogen‐bond mediated stabilization of a Cis ‐ D Pro imide‐bond in a stereocontrolled heterochiral model peptide
Author(s) -
Bhadbhade Mohan M.,
Kishore Raghuvansh
Publication year - 2012
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.21705
Subject(s) - chemistry , intramolecular force , hydrogen bond , moiety , stereochemistry , non covalent interactions , crystallography , intermolecular force , population , peptide , supramolecular chemistry , molecule , crystal structure , organic chemistry , biochemistry , demography , sociology
The X‐ray diffraction analysis of a stereocontrolled heterochiral designed model peptide Boc‐ D Pro‐Thr‐OMe ( 1 ) revealed the existence of an unusual folded molecular structure, stabilized via an effective unconventional CH…O type intramolecular hydrogen‐bond, encompassing a noncovalent 12‐membered ring‐motif. Together with an uncommon type a disposition of the urethane moiety, the tightly folded topology is compounded with a cis ‐ D Pro imide‐bond. The overall conformation is suggested to be the reminiscent of specific type VI β‐turn structures, hitherto, characterized across the Aaa‐ cis ‐Pro peptide‐bonds in globular proteins and polypeptides. The 13 C NMR spectrum of 1 in an apolar CDCl 3 environment revealed the presence of approximately an equal population of cis and trans isomers unexpectedly, analogous to Pro side‐chain, the 13 C NMR chemical‐shifts of Thr C β ‐resonance is observed to be sensitive toward cis‐trans isomerization. In conjunction with solid‐state FT‐IR spectral data, we established that a network of complex intermolecular hydrogen‐bonds stabilize a self‐complementary noncovalent helical hexagonal self‐assembly and crystallographic supramolecular aggregate. The results incline us to highlight that the stabilization of cis ‐ D Pro peptide‐bond in crystalline state may be driven by the favorable energy of formation of an unconventional weak CH…O intramolecular hydrogen‐bond. © 2011 Wiley Periodicals, Inc. Biopolymers 97: 73–82, 2012.