Irreversible Thermal Denaturation of Bovine Hemoglobin

This laboratory experience describes an experiment for the study of the thermal denaturation of an oligomeric protein, bovine hemoglobin, using circular dichroism spectroscopy. We have found that this process is irreversible and apparently follows a simple two-state model (native state to denatured state). The energy activation (E) that characterizes this reaction was calculated by the use of different approaches. The obtained values for E were rather similar between them, varying from 195.5 to 269.6 kJ/mol. When Lumry-Eyring model was considered we were able to estimate the van’t Hoff enthalpy for the equilibrium between native and unfolding states (738.2 kJ/mol). This experiment may be used to introduce the problem of thermal denaturation of an oligomeric protein and the biophysical methods to understand it.