Biochimica et Biophysica Acta vol:1814 issue:2 pages:318-25
An alkali-pretreated gelatin (pI~4.9) was fractionated by means of alcohol coacervation and semi-preparative gel chromatography. The thermal responses of the isolated α fractions, the coacervate and the total gelatin were investigated by 2D-correlation FTIR spectroscopy in the amide I band region (1600-1700cm(-1)). The gelation temperature was the same for all examined samples (24.5°C) while the melting temperature of the α(2) fraction was lower (30°C) than that of the other samples (32.5°C). The 2D COS plots indicate that on cooling (gelation) the core sequence of conformational changes is the same for all samples. On heating, however, the α(2) fraction deviates from the α(1)-containing samples and shows an earlier disappearance of the triple helix signal in the event sequence. The lower melting temperature (less thermostable gelatin gel) of the α(2) fraction thus results from a different conformational cascade of the α(2) chains upon melting. In all samples the initial conformational changes take place in the β-turns, providing further evidence for the models proposed previously.