Phase transitions of sequenced polytripeptides observed by microcalorimetry

The heat capacities (Cp) of sequenced polytripeptides, (prolyl-prolyl-glycine)10 and (prolyl-hydroxyprolyl-glycine)10, were measured. The peaks in the Cp curves associated with thermal transitions were observed to shift significantly without changing their shapes. The observed transitions are discussed in the framework of a first-order phase transition. The cause of the origin of the widths of the observed transitions is also discussed in relation to the Gibbs phase rule.