Fourier transform infrared (FT-IR) spectra were measured for an aqueous solution (pD =5.40) of defatted monomer bovine serum albumin (BSA) over a temperature range of 25-90
C toinvestigate temperature-induced secondary structure and conformation changes. The curve fitting methodcombined with the Fourier self-deconvolution technique allowed us to explore details of the secondarystructure and conformation changes in defatted BSA. Particularly striking in the FT-IR spectra was anobservation of the formation of an irreversible intermolecular
-sheet of BSA on heating above 70
C. Aband at 1630 cm
-1 in the spectra was assigned to short-segment chains connecting
-helical segments.The transition temperature for the short-segment chains connecting
-helical segments is lower by 17-18
C, when compared to those of the
-helix, turn, and intermolecular
-sheet structures of BSA,suggesting that the
-helix and turn structures of BSA are cooperatively denatured on heating. Moreover,the results give an important feature in heat-induced denaturation of BSA that the conformation changesoccur twice around both 57 and 75
C. The appearance of two peaks is interpreted by the collapse of theN-terminal BSA domain due to the crevice in the vicinity between domains I and II at low-temperaturetransition and by the change in cooperative unit composed of the other two BSA domains athigh-temperature transition.