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. Various biophysical techniques like UV-Vis absorption & photoluminescence spectroscopy, circular dichroism, FTIR, dynamic light scattering, and NMR techniques monitored the results. Rapid loss of helical structure of the protein was noted with an increase in β-sheet content as the helical structure decreased from ~34% to ~7% and the β-sheet increased from ~16% to ~34% in the first hour, beyond which there were minimal changes. UV-oxidation led to the thermal stability of the sample as compared to the partial reversibility of native lysozyme. Changes in the amide bands of the protein were noted, along with variations in the UV-vis & PL spectra of the samples. Loss of features with the increase in exposure was noted in the magnetic resonance spectrum. Lastly, with exposure, morphological changes were observed by cross-linking by generated radicals.