Oxidative stress via UVC irradiation on the structural rearrangement of hen egg white lysozyme†

Abstract

Oxidative stress is a physiological condition where oxygen radicals are responsible for the conformational restructuring and loss of functionality of important biomacromolecules. Among the various external agents, UV irradiation is one of the sources that can induce oxidative stress. Here, we report an in vitro study to gauge the effect of ROS on the structural rearrangement of hen egg white lysozyme, a hydrolytic enzyme, via UVC exposure studied via various biophysical techniques. The investigations revealed a rise in the β-sheet content of the protein at the expense of a decrease in α-helix within ten minutes of exposure, thereby showing rapid changes in the secondary structure. While the unexposed sample showed partial reversibility after being subjected to a heating and cooling cycle, the newly formed structures via irradiation, on the other hand, were found to be more thermally stable. The aging of the samples via UVC exposure was reflected in both the UV-vis and PL spectra of the samples, as well as the loss of spectral features in the aliphatic and aromatic regions in the magnetic resonance spectrum. Finally, the increase in the hydrodynamic diameter of the samples shows cross-linking taking place due to the generated oxygen radicals.