Synthesis, biological activity and solution structure of new analogues of the antimicrobial Gramicidin S

Gramicidin S (GS) is a cyclo-decapeptide antibiotic isolated from Bacillus brevis. The structural studies have shown that GS forms a two-stranded antiparallel beta-sheet imposed by two II' beta-turns. Despite its wide Gram+ and Gram- antimicrobial spectrum, GS is useless in therapy because of its high hemotoxicity in humans. It was found, however, that the analogues of GS-14 (GS with 14 amino acid residues) attained a better antimicrobial selectivity when their amphipatic moments were perturbed. In this study, we report effects of similar perturbations imposed on GS cyclo-decapeptide analogues. Having solved their structures by NMR/molecular dynamics and having tested their activities/selectivities, we have concluded that the idea of perturbation of the amphipatic moment does not work for GS-10_0 analogues. An innovative approach to the synthesis of head-to-tail cyclopeptides was used. Copyright (C) 2010 European Peptide Society and John Wiley & Sons, Ltd.