Study of thermal dynamics of defatted bovine serum albumin in D2O solution by Fourier transform infrared spectra and evolving factor analysis

Fourier transform infrared (FT-IR) spectra have been measured for defatted bovine serum albumin (BSA) in D2O with a concentration of 2.0 wt % over a temperature range of 26-90 degrees C and the corresponding difference spectra have been calculated by subtracting the contribution of D2O at the same temperature. Evolving factor analysis (EFA) by selecting two factors and three factors has been employed to analyze the temperature-dependent difference IR spectra in the 1700-1600 cm(-1) spectral region of the defatted BSA in D2O solution. Three-factor EFA has been employed to determine the distinction of the three protein species involved in the process of temperature elevation: native, transitional, and denatured protein. The temperature profiles obtained from three-factor EFA indicate that heat-induced conformational change in the secondary structures of defatted BSA in D2O undergoes two two-state transitions, a drastic transition and a slight transition, which occur in the temperature ranges of 68-82 degrees C and 56-76 degrees C, respectively.