NMR studies on thermal stability of α-helix conformation of melittin in pure ethanol and ethanol-water mixture solvents

Thermal stability of the alpha-helix conformation of melittin in pure ethanol and ethanol-water mixture solvents has been investigated by using NMR spectroscopy. With increase in water concentration of the mixture solvents (from 0 wt% to similar to 71.5 wt%) as well as temperature (from room temperature to 60 degrees C), the intramolecular hydrogen bonds formed in melittin are destabilized and the alpha-helix is partially uncoiled. Further, the hydrogen bonds are found to be more thermally stable in pure ethanol than in pure methanol, suggesting that their stability is enhanced with increase in the size of the alkyl groups of alcohol molecules. Copyright (C) 2011 European Peptide Society and John Wiley & Sons, Ltd.