Interaction between melamine and bovine serum albumin: Spectroscopic approach and density functional theory

Spectroscopic approach and density functional theory (DFT) have been employed to investigate the interaction between melamine (MA) and bovine serum albumin (BSA). The UV absorption difference spectra show the MA–BSA complexes can form under physiological conditions. Furthermore, the B3LYP/6-311++G(d,p) calculations indicate that the protonated melamine (MAH+) bond to Asp, Glu, Asn, Gln, Ser, Thr amino acid residues or peptide groups via NH(MAH+)…OC(BSA) or NH(MAH+)…OC(BSA) hydrogen bonds, in agreement with the results of UV absorption difference spectra, and the interaction energies of them decrease in the order Asp, Glu > Pep > Asn, Gln > Ser, Thr. The fluorescence spectra, synchronous fluorescence spectra and FT-IR spectra demonstrate that this interaction has no obvious effect on the secondary structure of BSA.