Anomalous refractivity changes of gramicidin A in ethanol solutions

Studies of the refractive properties of Gramicidin A in absolute ethanol and in ethanol water mixtures showed that this peptide in solution undergoes a conformational transition resulting in species with different refractivity. Accordingly, the folded form of this peptide shows a lower specific refractive index increment than the unfolded form. In addition, the occurrence of a strong pressure dependence of the transition is documented.