# Radiolysis of myoglobin concentrated gels by protons: specific changes in secondary structure and production of carbon monoxide

## TL;DR

This study explores how protons from radiation alter myoglobin's structure and produce carbon monoxide, shedding light on radiation's biological effects.

## Contribution

The paper reveals specific structural changes in myoglobin and CO production under proton irradiation, linking them to heme degradation.

## Key findings

- Proton irradiation alters myoglobin's secondary structure from alpha helices to beta elements.
- Irradiation leads to significant carbon monoxide production from heme degradation.
- Radiolytic yields of denatured myoglobin, CO, and heme degradation are approximately equal at 0.16 ± 0.01 species/100 eV.

## Abstract

While particle therapy has been used for decades for cancer treatment, there is still a lack of information on the molecular mechanisms of biomolecules radiolysis by accelerated ions. Here, we examine the effects of accelerated protons on highly concentrated native myoglobin, by means of Fourier transform infrared and UV–Visible spectroscopies. Upon irradiation, the secondary structure of the protein is drastically modified, from mostly alpha helices conformation to mostly beta elements at highest fluence. These changes are accompanied by significant production of carbon monoxide, which was shown to come from heme degradation under irradiation. The radiolytic yields of formation of denatured protein, carbon monoxide, and of heme degradation were determined, and found very close to each other: G+denatured Mb ≈ G+CO ≈ G-heme = 1.6 × 10–8 ± 0.1 × 10–8 mol/J = 0.16 ± 0.01 species/100 eV. The denaturation of the protein to a beta structure and the production of carbon monoxide under ion irradiation are phenomena that may play an important role in the biological effects of ionizing radiation.