Stabilization of helical domains in short peptides using hydrophobic interactions.

The contribution of hydrophobic interactions in the stabilization of helical structure was compared for a series of short peptides that incorporated two epsilon-(3,5-dinitrobenzoyl)Lys residues at various positions. Results showed that in aqueous/organic mixtures, methanol induced helical stability over a wider range and at higher concentration than trifluoroethanol (TFE); a similar degree of stability was seen in low mole fraction mixtures of TFE in water. Solvent mixture titrations in TFE/water demonstrated that helical stability was highest for the peptide having a pair of modified residues spaced by three other residues. Solvent mixture titrations in TFE/water appear to be useful in indicating the degree of hydrophobic stabilization.