Mechanistic understanding and binding analysis of a novel Schiff base palladium (II) complex with β-lactoglobulin and human serum albumin

Abstract

The binding interactions between new Schiff base palladium(II) complex and two transporter proteins, human serum albumin (HSA) and β-lactoglobulin (β-LG) were studied by spectroscopic and computational methods. Fluorescence spectroscopy results revealed the strong quenching of intrinsic fluorescence of both HSA and β-LG due to interaction with Pd(II) complex by a static quenching mechanism. The Pd(II) complex interacted with studied proteins with moderate binding affinity (Kb = 1.01 × 104 M−1 for HSA and 6.60 × 103 M−1 for β-LG at 303 K). The thermodynamic parameters revealed the contribution of hydrogen bond and Van der Waals interactions but, the role of hydrophobic interactions was not negligible due to imine group in structure of complex and obtained small positive ∆S° values in both systems. UV–Visible and FT-IR measurements indicated that the binding of Pd(II) complex to HSA and β-LG may induce conformational and micro-environmental changes of these proteins. Moreover, Multivariate Curve Resolution- Alternating Least Square (MCR-ALS), was used for resolution of measured complex spectra and estimation the number of independent chemical species. The docking studies indicate the Pd(II) complex binds to residues located in the subdomain IIIA of HSA and site II of β-LG.