Mechanism of Albumin Degradation Under the Action of UV Radiation and Reactive Oxygen Species

Oxidative degradation of bovine serum albumin (BSA), an albumin-like mixture of aromatic amino acids (tyrosine, tryptophan, and phenylalanine), and separately the same aromatic amino acids that are part of BSA, under the action of reactive oxygen species (ROS)—hydroxyl and hydroperoxyl radicals—as well as UV radiation (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda =253.7$</tex-math> </inline-formula> nm) was investigated. The source of hydroxyl radicals was cold plasma of corona electric discharge; hydroperoxyl radicals were generated in an aqueous solution under the influence of pulsed radiation from hot plasma. The source of continuous UV radiation was a low-pressure mercury lamp. The initial substances and reaction products were identified by fluorescence in the 2-D scanning mode. In the process of oxidative degradation of phenylalanine, tyrosine was formed, and the yield of tyrosine was compared with the consumption of phenylalanine. During the oxidation of phenylalanine and tyrosine, dityrosine isomers were formed. For all reaction channels, Stern–Volmer-like coefficients <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K_{\text {SV}}^{0}$</tex-math> </inline-formula> were determined, which characterize the relative change in fluorescence yield both in the case of consumption of the initial substance and the formation of a new product, depending on the dose. On the basis of the coefficients <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K_{\text {SV}}^{0}$</tex-math> </inline-formula>, the features of the mechanism of ROS and UV radiation reactions with aromatic amino acids and protein are analyzed.