NMR study on the low-affinity interaction of human serum albumin with diclofenac sodium

The low-affinity interaction between human serum albumin (HSA) and Diclofenac sodium (DCF) was studied using NMR techniques. Both 13C-NMR chemical shift and linewidth show that the dichlorophenyl ring in DCF molecule plays a primary role in its interaction with HSA. Langmuir adsorption isotherm was applied to evaluate the association constant K and the number of binding sites n of the drug/HSA complex through (1)H-NMR spin-lattice relaxation measurement. The results indicate that Langmuir isotherm can perfectly explain the capacity of low-affinity binding of proteins for the ligands.