Difference Spectra of Proteins

Abstract

It has already been noted that the application of UV spectroscopy for studying conformation and conformational transitions of proteins is based on the dependence of the parameters of these spectra on the chromophore group interactions with other groups in the protein molecule and solvent molecules. The observed spectroscopic effects, shifts of absorption bands for about 1 nm and less, are small in comparison to the half-width of absorption bands, being about 30 nm. Additional approaches and techniques are required for facilitating the analysis of spectra and increasing their sensitivity. At present, difference spectrophotometry is widely used as such a method. Difference spectra are the absorption spectra obtained by simultaneously measuring two samples (automatic subtraction of one from the other). Through application of difference spectra in studies of proteins, inconsiderable changes are observed in the position of the absorption bands, their shape, and intensity, which are to be determined.