Binding of a novel bacteriostatic agent—chitosan oligosaccharides–kojic acid graft copolymer to bovine serum albumin: spectroscopic and conformation investigations

Abstract

In this paper, a novel chitosan oligosaccharides derivative—chitosan oligosaccharides–kojic acid graft copolymer (COS/KA), COS, and KA were selected to investigate the binding to bovine serum albumin (BSA) using UV–Vis spectroscopy, fluorescence, synchronous fluorescence, and circular dichroism (CD) at pH 7.4. The results indicated that the tryptophan residues of BSA to the distance of COS/KA, COS, and KA were 2.0 × 1010 L mol−1 s−1 for COS/KA–BSA, COS–BSA, and KA–BSA at 298, 302, 306, 310 K, respectively, those confirmed that the quenching process belongs to static quenching. The thermodynamic parameters ∆H°, ΔG°, ΔS° at different temperatures were calculated and indicated that hydrophobic and electrostatic forces played important roles in the binding process, and the enhanced binding affinity mainly associated with the increase of the hydrophobicity. Moreover, the CD data demonstrated that the secondary structure of BSA was slightly altered in the presence of COS/KA, COS, and KA, with different reduced α-helix contents (46.30 ± 0.20, 48.60 ± 0.40, 50.70 ± 0.20), respectively. The work provides basic data for the binding mechanism of COS/KA with BSA in vitro.