Wojciech Rogóż, Julia Szczypta, Aleksandra Owczarzy, Karolina Kulig, Małgorzata Maciążek-Jurczyk

The influence of selected compounds on the reaction between human serum albumin and a model free radical

 

2024-12-02

Object of study. Human serum albumin (HSA) is a protein present in human blood and it has many important functions. It participates in the transport of various ligands and it is involved in maintaining oxidation-reduction balance. The result of binding ligands by HSA is not only their transport, but also the change of the protein`s structure and its biological activity.

Aim of the study. The aim of this study was to investigate the effect of selected antioxidants and compounds with potential antioxidant activity (caffeine, colchicine, salicylic acid, gallic acid, ascorbic acid) binding to HSA on its reaction with the model free radical DPPH.

Materials and methods. In order to study the impact of DPPH on the conformation of HSA, CD spectra in the far and near ultraviolet were determined and analysed.

Results. It has been shown that the model free radical DPPH can influence the HSA secondary structure, regardless of the presence of ligands. A change in the percentage content of each secondary structure was also observed due to the interactions between HSA and included ligands, except for caffeine. It was confirmed that the presence of DPPH in the environment results in changes on the level of HSA tertiary structure in the regions rich in aromatic amino acid residues. Similar effects were observed in the case of HSA samples containing colchicine, salicylic acid and ascorbic acid. In turn, gallic acid and caffeine affected the conformation in the regions rich in Tyr and Trp residues. It was reported that gallic acid forming a complex with HSA, probably has a protective effect on this protein, shielding its tertiary structure against changes caused by the radical reaction with DPPH.

Conclusions. The performed analyses have confirmed the usefulness of circular dichroism spectroscopy to study reactions between free radicals and proteins or protein-ligand complexes. The demonstrated impact of DPPH on HSA`s conformation can probably be reduced by some ligands, such as gallic acid.

Keywords: albumin, DPPH, circular dichroism, antioxidants.

© Farm Pol, 2024, 80(7): 477–487