Localization of porphyrins and their metal complexes in albumin and its effect on protein aggregation and denaturation

Albumin is a globular protein with a number of functions of vital importance. Its aggregation can cause serious problems and cause hypoalbuminemia. Albumin complex formation with endogenous and exogenous porphyrins can lead to aggregation. This work is a study of the localization effect of a number of endogenous porphyrins, such as protoporphyrin, hematoporphyrin, deuteroporphyrin and their metal complexes in an albumin globule on the albumin state in solutions and resistance of protein complexes to thermally induced denaturation. The structure of the obtained complexes was determined by the IR and fluorescence spectroscopy methods in combination with molecular docking. The results obtained show that nature porphyrins form hydrogen bonds with various sections of the albumin polypeptide chain and cause changes in the protein secondary structure associated with the transformation of alpha-helices into beta-folds and subsequent protein aggregation. The DSC studies revealed that complex formation with porphyrins lowered the thermal effect of protein denaturation by 50-67%. The dependence of the structure of the complexes on the denaturation thermal effect was analyzed. It was established that the changes in the protein denaturation thermal effect could be used to determine porphyrin localization in the protein globule and protein ability to form aggregates, following complex formation. (C) 2021 Published by Elsevier B.V.