Time-dependent conformational changes of proteins and oil molecules at oil-'protein solution' interface were studied using ATR (Attenuated Total Reflection)-FTIR spectroscopic technique for the case of Bacillus subtilis extracellular proteins (BSEPs) and bovine serum albumin (BSA) in hexane-'protein solution' system. The IR spectra collected on the protein aggregate - film - formed at the hexane-'protein solution' interface demonstrated time-dependent conformational changes of the proteins through changes in the shapes and positions of the H2O-'amide I' cross peaks and the amide II peaks as a function of time (0-90th minute). Hexane-protein intermolecular association in the film was evident as the CH stretching vibration peaks of hexane were present along with the amide peaks in all the spectra collected over a period of 90min. Conformational changes of the hexane molecules, along with that of the proteins, were observed via variations (broadening and red/blue shifts) in the CH stretching vibration peaks of the CH3 and the CH2 groups of hexane. The red/blue shifts of the CH stretching vibration peaks of hexane were different with BSEPs and BSA, further indicating that the conformational changes of hexane molecules being protein specific. As similar to the protein types considered here, at oil-'protein solution' interfaces, conformational changes of the oil molecules appear to be a regular phenomenon.
Keywords: Adsorption; Conformational change; Interface; Protein film; Red/blue shift.
Published by Elsevier B.V.