Thermally driven interactions between beta-lactoglobulin and retinol acetate investigated by fluorescence spectroscopy and molecular modeling methods

摘要

Whey proteins have important functional properties as it can bind a wide range of bioactive molecules. In this study, the complexation of beta-lactoglobulin with retinol at alkaline pH was investigated. The fluorescence spectroscopy was used to determine the temperature dependent behavior of the beta-lactoglobulin-retinol acetate (beta LG-RET) ensemble. The pattern of protein unfolding in the temperature range of 25-85 A degrees C was followed mainly considering the exposure of tryptophan (Trp) residues. The beta LG-RET complex appeared rather stable in the 25-60 A degrees C range, while further increase of the temperature caused partial unfolding. The anisotropy measurements indicated a more flexible conformation at temperature increase up to 80 A degrees C. In addition, the in silico approach was used to complement the experimental results. Important changes in the interaction surface were observed after performing molecular dynamics simulations. The temperature increase caused important rearrangements of the amino acids of the EF loop involved in the interaction with the retinol molecule, which got twisted. These atomic level events induced a significant increase of the affinity between beta LG and retinol. This study offers useful information on the potential use of beta LG as a carrier for biologically active compounds in order to obtain food products with desired functionalities.