The Variable-Temperature FT-IR Study of the Secondary Structure of γ-Globulin, Chymotrypsin, Serum Albumin, and β-Lactoglobulin in Aqueous Solution

The FT-IR spectra of γ-globulin, chymotrypsin, serum albumin, and β-lactoglobulin were collected in aqueous buffer solutions at different temperatures. A least-squares subtraction algorithm was used to subtract the interfering water bands in the amide I, II, and III frequency regions. The spectra of the protein amide I and II bands were deconvoluted with the use of Fourier self-deconvolution and a Lorentzian curve fit process, and band assignments were made for the α helix, β pleated sheet, and disordered or turns structures of the proteins. Factor analysis was applied to the variable-temperature protein spectra, and the compositions with respect to the different types of secondary structures were calculated.