Analysis of the State of Aromatic Amino Acid Residues in Heated Soybean 7S Globulin by Absorption Derivative Spectrophotometry and Spectrofluorimetry

The heating of 7S globulin caused changes in the intensities, but hardly affected the positions of the peaks and troughs of the second derivative absorption spectra at wavelengths below 270 nm. On the other hand, above 271 nm, changes were reflected both in the intensities and in the positions of peaks and troughs. The difference-second derivative absorption spectra indicated that 60 and 70 percent, respectively, of phenylalanine and tyrosine residues buried in the native 7S globulin remained as the buried form even after heating. A Spectrofluorimetry and fluorescence-quenching study suggested that one residue of tryptophan in the 7S globulin tended to be transferred to the more hydrophobic interior on heating.