Secondary structure transitions of Bovine serum albumin induced by temperature variation

Secondary structure transitions of Bovine Serum Albumin (BSA) in H2O and D2O under temperature variation were investigated by in-situ IR spectral analysis and they were found to exhibit the same tendency with the only difference that the significant transition temperature of BSA's secondary structure moved towards a lower temperature in D2O. Before this significant transition temperature, the native secondary structures of BSA were essentially changing in a cooperative fashion with temperature variation, except for the intermolecular β-sheet (high-wavenumber) which increased as a result of thermal denaturation at a later stage. After the transition temperature, the relative contents of α-helix and extended chain continued to drop sharply and they were transformed into random coil, β-turn and β-sheet.