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Chirality and Template‐Mediated Induction of Helical Preferences in Achiral β‐Peptides
Author(s) -
Sharma Gangavaram V. M.,
Kodeti Srinivas Reddy,
Dutta Samit K.,
Velaparthi Subash,
Narsimulu Kongari,
Anjaiah Gonuguntla,
Basha Shaik Jeelani,
Kunwar Ajit C.
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201201892
Subject(s) - chirality (physics) , helix (gastropod) , trimer , n terminus , stereochemistry , circular dichroism , chemistry , peptide , amino acid , folding (dsp implementation) , crystallography , peptide sequence , biochemistry , biology , organic chemistry , physics , ecology , dimer , chiral symmetry breaking , engineering , quantum mechanics , snail , gene , nambu–jona lasinio model , electrical engineering , quark
This study describes chirality‐ or template‐mediated helical induction in achiral β‐peptides for the first time. A strategy of end capping β‐peptides derived from β‐hGly (the smallest achiral β‐amino acid) with a chiral β‐amino acid that possesses a carbohydrate side chain (β‐Caa; C‐linked carbo β‐amino acid) or a small, robust helical template derived from β‐Caas, was adopted to investigate folding propensity. A single chiral ( R )‐β‐Caa residue at the C‐ or N‐terminus in these oligomers led to a preponderance of right‐handed 12/10‐helical folds, which was reiterated more strongly in peptides capped at both the C‐ and N‐terminus. Likewise, the presence of a template (a 12/10‐helical trimer) at both the C‐ and N‐terminus resulted in a very robust helix. The propagation of the helical fold and its sustenance was found in a homo‐oligomeric sequence with as many as seven β‐hGly residues. In both cases, the induction of helicity was stronger from the N terminus, whereas an anchor at the C terminus resulted in reduced helical propensity. Although these oligomers have been theoretically predicted to favor a 12/10‐mixed helix in apolar solvents, this study provides the first experimental evidence for their existence. Diastereotopicity was found in both the methylene groups of the β‐hGly moieties due to chirality. Additionally, the β‐hGly units have shown split behavior in the conformational space to accommodate the 12/10‐helix. Thus, end capping to assist chiralty‐ or template‐mediated helical induction and stabilization in achiral β‐peptides is a very attractive strategy.