Differential scanning calorimetric studies on binding of N-acetyl-d-glucosamine to lysozyme (original) (raw)

1995, Biophysical Chemistry

Differential scanning calorimetric (DSC) measurements were performed on the thermal denaturation of lysozyme and lysozyme complexed with N-acetyl-o-ghtcosamine (G~cNAc) at pH 5.00 (acetate buffer), 4.25 and 2.25 (Gly-HCI buffer). DSC data have been analyzed to obtain denaturation temperature Td, enthalpy of denaturation AH,, heat capacity of denaturation AC,, and cooperativity index 77. From these thermodynamic parameters, the binding constant K, and enthalpy of binding AH,_, for the weak binding of lysozyme with GlcNAc have been determined. The values of K, and AH,_ at pH 5.00 and 298 K are 42k4 M-' and-24 f 4 kJ mol-', respectively, and agree very well with the experimentally determined values from equilibrium and other studies. The binding constant has also been estimated by simulating the DSC curve with varying values of K, CT,) until it matches the experimental curve.