Protein unfolding and subsequent refolding: a spectroscopic investigation.

The mechanism by which the protein Bovine Serum Albumin (BSA) undergoes unfolding induced by Guanidine Hydrochloride (GdHCl) and then the subsequent refolding brought in by many-fold dilution was studied by steady-state fluorescence, anisotropy, time resolved measurements and Circular Dichroism (CD) spectroscopy. CD data reveal that the protein attains a degree of extra rigidity at low concentrations of the denaturant, GdHCl, and this observation was correlated with other techniques used in this present work. The unfolding and refolding of BSA appear to proceed through intermediates and both the processes are sequential in nature. The intrinsic fluorescence from the tryptophan amino acid residue of BSA and another external fluorophore Nile Red was made use of in order to investigate the mechanisms of unfolding and refolding and we have conclusively proved that both these processes follow a reversible mechanism.