Structure dependent hydrophobic and hydrophilic interactions between nickel(II) Schiff base complexes and serum albumins: Spectroscopic and docking studies

A systematic and comparative binding study between serum-albumins (SA) and a series of monomeric nickel(II)-Schiff-base-complexes (NSCs), which might be imperative to investigate the function of SA behind nickel allergy, has been carried out through docking and different spectroscopic techniques. The initial docking studies indicate structure-dependent selective hydrophobic and hydrophilic interactions. The pyridine and phenyl containing NSCs, which are more aromatic, show better π-π staking compared to pyrrole one. Again all the NSCs bind with BSA though amino acid residues of IB domain affecting local environment of the Trp-134 surrounded by both hydrophobic and hydrophilic residues instead of the hydrophobically buried Trp-212. In HSA the hydophobically buried Trp-214 is influenced by NSCs. The experimental results nicely support the docking outcomes. The changes in Gibbs free energy, binding affinity and the nature of hydrophilic/hydrophobic interactions of NSC-SA systems indicate greater accessibility of N2O2 donor set complex compared to N4 one towards SA. Quantum chemical structure optimizations support the better planarity of NSC with N2O2 which provides better binding. Therefore the structural variation of N2O2 donor set complexes becomes much more useful compared to N4 one to search out the most compatible NSC towards SAs.