Spectrophotometric studies on the binding of Vitamin C to lysozyme and bovine liver catalase

The patterns of Vitamin C (ascorbic acid) binding to lysozyme (LYSO) and bovine liver catalase (BLC) were investigated at 298, 308 and 316 K at pH 7.40 using spectrophotometric techniques. The quenching mechanism, binding constant and the number of binding sites were determined by fluorescence experiments. Moreover, the Stern–Volmer fluorescence quenching constant (KSV) of LYSO by Vitamin C was more sensitive to the temperature changes than that of BLC by Vitamin C. The thermodynamic data suggest that hydrogen bonds were the predominant intermolecular forces in the binding reaction. The effect of Vitamin C on the conformation of LYSO or BLC was analyzed using synchronous fluorescence, UV–vis absorption and circular dichroism (CD) spectra.