Vibrational circular dichroism spectra of protein films: thermal denaturation of bovine serum albumin

Vibrational circular dichroism (VCD) spectroscopy has been used for the first time to investigate the thermal denaturation of proteins in H2O solutions. Films prepared from heated aqueous solutions were used for these investigations. A well-known alpha-helical protein, bovine serum albumin (BSA), is used for this first study. Both VCD and infrared absorption results obtained for BSA films indicate that the heat treatment of BSA induces significant amounts of beta-sheet structure and that the denaturation process is irreversible. To verify the irreversible nature of thermal denaturation, optical rotation was also measured as a function of temperature in both heating and cooling cycles. These results also indicate that thermal denaturation of BSA in solution is irreversible. This study establishes the usefulness of films for VCD investigations and offers new avenues for VCD studies on biologically important systems. (C) 2004 Elsevier B.V. All rights reserved.