Peptidomimetic design of unusual turns by incorporating flexible and rigid omega-amino acids simultaneously
Kar, S., Drew, M. and Pramanik, A. (2010) Peptidomimetic design of unusual turns by incorporating flexible and rigid omega-amino acids simultaneously. Journal of Molecular Structure, 963 (2-3). pp. 160-167. ISSN 0022-2860
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To link to this article DOI: 10.1016/j.molstruc.2009.10.029
The tripeptides Boc-Gly-Aib-m-ABA-OMe (I), Boc-beta Ala-Aib-m-ABA-OMe (II) and Boc-gamma Abu-Aib-rn-ABA-OMe (III) (Aib: alpha-aminoisobutyric acid, beta Ala: beta-alanine, gamma Abu: gamma-aminobutyric acid, m-ABA: meta-aminobenzoic acid) with homologated amino acids at the N-terminus, the rigid gamma-amino acid m-ABA at the C-terminus and the helicogenic Aib at the central position have been chosen to create unusual turns. Single crystal X-ray diffraction studies, solvent dependent NMR titrations and 2D NMR analysis reveal that peptides II and III adopt unusual turns of 11- and 12-membered rings stabilized by modified 4 -> 1 type intramolecular hydrogen bonds. Solution phase studies indicate that peptide I exists in the beta-turn conformation stabilized by 10-membered intramolecular hydrogen bonding.