Fluorescence Spectroscopic Studies on Ovis Lactoperoxidase

Ovis lactoperoxidase (sLP), on excitation at 280 nm shows fluorescence emission of a single broad maximum at 332 nm. The conformational stability was measured by unfolding studies in urea and guanidine hydrochloride. The fluorescence intensity gradually decreased with increase in urea concentrations. The decline might have been caused by partial unfolding, affecting some of the tryptophan residues. In 5 M GuHCl concentrations, a red shift in emission maximum to 356 nm was observed. It indicates that tryptophan is buried in the interior of the hydrophobic environment in native folded state and inaccessible to solvent water but on unfolding all get exposed to aqueous environment. Acrylamide is an efficient quencher and the quenching process is essentially homogenous with all tryptophan being accessible. A little quenching is observed for KI is interpreted as sLP has tryptophan residues that are buried inside the core of the protein.