Thermal effects of added propanol on the helix–coil transition of (Pro-Pro-Gly)10 in D2O solution: An NMR study

The conformational transition of collagen model peptide, (Pro-Pro-Gly)10, from the triple helical structure to the statistical coil was observed in various aqueous alcohol solutions by NMR measurements. In methanol or ethanol solution, the thermal transition temperature, Tm, of the peptide increased regularly with the concentration of alcohols. In 1- or 2-propanol, however, Tm first decreased and then increased steeply, in apparent contrast to the general trend that the addition of alcohol on aqueous solution increases the stability of ordered structure of polypeptides. This exceptional behavior of the collagen model peptide in propanols might provide a clue to investigate the mechanism of stabilization of protein conformation.