Synthesis, characterization and the interaction of some new water-soluble metal Schiff base complexes with human serum albumin

• The nature of the interaction of water soluble metal Schiff base complexes with HAS was investigated.
• The complex binding did not induce any aggregation on HSA molecules.
• The mechanism of binding of the complexes with HSA was dynamic.
• The microenvironment around the tryptophan residues did not show obvious changes during the binding process.
• Thermodynamic results indicated that the binding process was endothermic.

Some new water-soluble Schiff base complexes of Na2[M(L)(H2O)n]; (M = Zn, Cu, Ni, Mn) with a new water-soluble Schiff base ligand where L denotes an asymmetric N2O2 Schiff base ligands; N,N′-bis(5-sulfosalicyliden)-3,4-diaminobenzophenone (5-SO3-3,4-salbenz) were synthesized and characterized. The formation constants of the water soluble Schiff base complexes were calculated by Ketelaar’s equation. The theoretical molecular structure for the complexes was computed by using the HF method and the 6-311G basis set. The mechanism of binding of Na2[M(L)(H2O)n] with human serum albumin (HSA) was studied by fluorescence spectroscopic technique. The results of fluorescence titration showed that the intrinsic fluorescence of HSA was quenched by the complexes; which was rationalized in terms of the dynamic quenching mechanism. The values of Stern–Volmer constants, quenching rate constants, binding constants, binding sites and average aggregation number of HSA have been determined. The thermodynamic parameters, were calculated by van’t Hoff equation, indicate that the binding is entropy driven and enthalpically disfavored. Based on the Förster theory of non-radiation energy transfer, the efficiency of energy transfer and the distance between the donor (Trp residues) and the acceptor (complex) were obtained. Finally, the growth inhibitory effects of the complexes toward the K562 cancer cell line were measured.

Effect of water soluble Schiff base complex, [ZnL], on the fluorescence spectra of HSA (T = 298 K). c(HSA) = 1.0 × 10−5 mol dm−3, investigated c[ZnL]) = 2.5×10−6 − 2.0 × 10−5 mol dm−3.Figure optionsDownload as PowerPoint slide