Irreversible unfolding of myoglobin in an aqueous solution by supercritical carbon dioxide

The conformational changes in myoglobin, treated by microbubbling of superc ritical carbon dioxide (SC-CO2), were investigated by measuring the circula r dichroism spectra in the ultraviolet range and compared with those in oth er proteins (ovoalbumin, bovine serum albumin, and beta -lactoglobulin), Ir reversible unfoldings were observed after the microbubbling of SC-CO2 at 35 degreesC and 30 MPa for 30 min. The degree of unfolding depended on the nu mber of intramolecular S-S bonds. alpha -Helix contents of myoglobin decrea sed with increasing density of SC-CO2. Unfoldings of myoglobin induced by h eating, pH-lowering, and the addition of a denaturant were reversible. The irreversible unfolding of myoglobin was also observed by the bubbling of ga seous CO2 under atmospheric pressure, but heating was required.