Two-Phase Induction of the Nonnative α-Helical Form of β-Lactoglobulin in the Presence of Trifluoroethanol

Abstract

The trifluoroethanol-dependent induction of the nonnative α-helical form of β-lactoglubulin has been studied by circular dichroism spectroscopy. Data analysis is performed by factor analysis and multivariate curve resolution. An intermediate form in the induction of the α-helical form of the β-lactoglobulin has been identified at low TFE concentration. By application of an alternating least-squares algorithm, the CD spectrum corresponding to the intermediate form has been resolved. The deconvolution of this CD spectrum shows a secondary structure content more in agreement with the one predicted from the amino acid sequence than the secondary structure of the helical form obtained at higher TFE concentrations. The additional α-helical content of the form present at higher TFE concentrations could be due to nonspecific interaction of TFE with the polypeptide chain.