Conformations of gramicidin A and its 9,11,13,15-phenylalanyl analog in dimethyl sulfoxide and chloroform |
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| Authors: | F Heitz A Heitz Y Trudelle |
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| Institution: | 1. CIQUP, Centro de Investigação em Química, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Porto, Portugal;2. Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain;3. Faculty of Pharmacy, Comenius University in Bratislava, 832 32 Bratislava, Slovak Republic;4. iBB – Institute for Bioengineering and Biosciences, Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal;5. Department of Chemistry and Biochemistry, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal |
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| Abstract: | In order to understand the difference in single channel behavior of gramicidin A as compared to that of gramicidin M- which is the mirror image of gramicidin M (all four tryptophanyl residues substituted by phenylalanine), conformational investigations were made under several experimental conditions. It is shown that, when examined under identical conditions, both molecules adopt the same conformations which could be identified in dimethyl sulfoxide (DMSO) and chloroform. In DMSO the conformation is based on a succession of beta-turns while in chloroform gramicidin A and M- can adopt a dimeric hybrid structure: a double helix terminated by two single-stranded helices involving the N- and C-terminal parts, respectively. It is therefore concluded that the difference in the energy profile between both gramicidins which was deduced from the ion transfer data has its origin in the nature of the aromatic side chains. |
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