Solvent denaturation of proteins as observed by resolution-enhanced Fourier transform infrared spectroscopy.

Fourier self-deconvolution of Fourier transform infrared (FTIR) spectra and second derivative FTIR spectroscopy were applied to study solvent-induced conformational changes in globular proteins. For beta-lactoglobulin a total of three different denatured forms were identified in alkaline solution and in aqueous methanol-d1 and isopropanol-d1. In isopropanol-d1 solution a new conformation was identified which appears to resemble, but is not identical with, the beta-structure of native proteins. This conformation is characterized by absorption bands around 1615-1618 and 1684-1688 cm-1, and is also observed for concanavalin A and chymotrypsinogen A in aqueous isopropanol-d1 solution.