The effect of UV radiation on bovine serum albumin solutions was studied, and differences in the photomodification of bovine serum albumin molecules in different media were revealed. The formation and properties of complexes formed by albumin and lysozyme molecules have been studied. A change in the spectral characteristics and hydrodynamic radius of protein complexes under the action of UV light is shown. It was found that a change in the ionic strength of the solution at pH 5.5 does not affect the absorption spectrum of albumin, which confirms the stability of its conformation. In the Na-phosphate buffer at pH 5.5, albumin exists mainly in the form of dimers with a hydrodynamic radius of ~5.14 nm, while monomeric and dimeric forms are present in distilled water, which indicates the heterogeneity of the aggregate state of the system. It has been shown that UV irradiation causes dose-dependent photooxidation of tyrosine residues to form dityrosine, which is reflected in the albumin spectrum in the 300-320 nm band. At the same time, the photolability of albumin is higher in buffer than in water. Under the influence of UV light, the size and number of aggregates increase, which is associated with the destruction of intramolecular bonds and the formation of molten globules. The addition of lysozyme to albumin in buffer solution does not change the absorption spectrum of albumin at 250−290 nm. Molecular docking has shown that during the formation of the albumin– lysozyme complex, Trp, Tyr, and Phe residues are not shielded. Hydrodynamic analysis confirmed the formation of an albumin–lysozyme complex (~5 nm) predominantly with the monomeric form of albumin. UV irradiation affects the interaction of bovine serum albumin with lysozyme: at low doses (755 and 1510 J/m), the optical density of the complex decreases; at high doses (3020 J/m) complex formation is impeded. In the irradiated samples, lysozyme reduced the intensity of the aggregation of albumin molecules, which indicates its stabilizing role. In aqueous solutions, exposure to UV light reduced the size of the albumin-lysozyme monomer complex and promoted the formation of larger aggregates.
Lusheva et al. (Thu,) studied this question.