Solvent determined conformation of gramicidin affects the ability of the peptide to induce hexagonal HH phase formation in dioleoylphosphatidylcholine model membranes

It is shown by 31P-NMR and small angle X-ray scattering that induction of an hexagonal HH phase in dioleoylphosphatidylcholine model membranes by external addition of gramicidin A′ depends on the solvent which is used to solubilize the peptide. Addition of gramicidin from dimethylsulfoxide or trifluoroethanol solution leads to HH phase formation whereas addition of the peptide from ethanol does not. This solvent dependence is shown by circular dichroism to be correlated with the peptide conformation. The channel conformation appears to be responsible for HH phase formation by gramicidin