# Molecular Rearrangement in Aromatic Amino Acids and Proteins After Reaction with Hydroxyl and Hydroperoxyl Radicals and UV-C Radiation

## TL;DR

This study explores how aromatic amino acids and proteins change when exposed to radicals and UV-C light, using fluorescence to track molecular changes.

## Contribution

The paper introduces a method to study free radical processes in proteins using fluorescence quenching and excitation under UV-C and radical exposure.

## Key findings

- Hydroxyl radicals can abstract hydrogen atoms from any position in target molecules.
- UV-C radiation excites the entire protein molecule, not just specific parts.
- Fluorescence changes indicate molecular rearrangements in amino acids and proteins.

## Abstract

The fluorescence of aqueous solutions of the aromatic amino acids tryptophan, tyrosine, and phenylalanine, an albumin solution, and a mixture of water-soluble animal and plant proteins is investigated after treatment with hydroxyl and hydroperoxyl radicals and continuous UV-C radiation at λ = 253.7 nm. The use of independent sources of active species allows for the study of activation and the development of free radical processes in model objects. The analysis is based on Stern–Volmer coefficients for the quenching of the fluorescence of the initial substrates and the ignition of the fluorescence of newly formed products. In the reaction with hydroxyl radicals, the hydrogen atom could be abstracted from any position in the target molecule. Under continuous UV-C radiation, the protein molecule as a whole was excited.