Studies on Sulfamethazine - Lysozyme Interactions by Fluorescence Quenching

Abstract

The binding of sulfamethazine to lysozyme was investigated in relation to certain physicochemical parameters by a fluorescence quenching technique. The parameters considered are ionization of the drug, hydrogen-ion concentration and alteration in protein conformation induced by urea at different pH-levels. The binding constant of the drug was found to be pH-dependent, increasing as the pH is reduced from 9 to 5. On the other hand, denaturation of lysozyme with urea favors the binding process. The interaction being again more pronounced at the lower pH's, when the drug is in the unionized form, and depends also upon the extent of denaturation of the enzyme.

Graphic representation, as well as, computer analysis of the different corrected binding data, at high drug to protein ratios are strongly indicative of a 1:1 interactions. The nature of the binding forces, and changes in the binding constants associated with alteration in the ionization of sulfamethazine at various pH-points were further interpreted in terms of hydrogen-ion dissociation equilibrium of the drug