Conformational study of new amphipathic α‐helical peptide models of apoA‐I as potential atheroprotective agents

Aiming at contributing to the development of potential atheroprotective agents, we report on the concept and design of two peptide models, which mimic the amphipathic helices of apoA‐I and incorporate Met into their sequences to validate its role as oxidant scavenger: Ac‐ESK(Palm)KELSKSW 10 SEM 13 LKEK(Palm)SKS‐NH 2 (model 1 [W 10 , M 13 ]) and Ac‐ESK(Palm)KELSKSM 10 SEW 13 LKEK(Palm)SKS‐NH 2 (model 2 [M 10 , W 13 ]). Hydrophobic residues of both models cover about the half of the surface, while the positively and negatively charged residues constitute two separate clusters on the hydrophilic face. Palmitoyl groups were introduced into the Lys‐N ϵ H 2 groups at positions 3 and 17 to contribute to the amphipathic character of the peptides and stabilize the nonpolar face of the helix. Conformational study by the combined application of 2D‐NMR and molecular dynamics simulations, CD, FTIR, and fluorescence spectroscopy revealed that model 1 adopts helical conformation and Met is well exposed to the microenvironment. Model 2 that derives from model 1 by exchanging W 10 (model 1) with M 10 and M 13 (model 1) with W 13 also displays helical characteristics, while Met is rather shielded. Oxidation experiments indicated that model 1 exhibits a 2‐fold more potent antioxidant activity towards LDL oxidation, compared to model 2, confirming the role of Met, when is devoid of steric hindrances, as oxidant scavenger for the protection of LDL. © 2006 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 88: 362–372, 2007. 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