Contrary to conventional belief, amino acid show conformational preferences in unfolded peptides and proteins in aqueous solutions. This is particularly true for alanine, which exhibits PPII fractions between 0.8 and 0.9 at room temperature. Individual propensities of residues are changed by interactions with their nearest neighbors and co-solvent addition to water. We are currently performing detailed spectroscopic studies (NMR, CD, vibrational spectroscopy) to determine the nearest neighbor interactions in selected GxyG peptides (x,y: different types of residues) and structural changes of tripeptides by co-solvents. First results reveal (a) that serine and aspartic acid at the x-position affect the distribution of alanine at y, (b) that GDAG forms turn structures and (c) that glycerol and ethanol co-solvents directly interact directly with alanine side chains, thus stabilizing �-strand like conformations. Altogether, our results reveal a rather complex relationship between solution parameters and the Gibbs energy landscape of unfolded peptides.

Influence of nearest neighbors and solvent composition on conformational propensities of amino acid residues in unfolded peptides

243rd National Meeting (2012)

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