Radiation-induced effects on a fibronectin peptide: investigation of electron ejection and disulfide bond cleavage

Studying the direct effects of radiation on proteins at the molecular scale is crucial for describing, quantifying and understanding the consequences of radiation on biological matter. These direct effects are particularly relevant in the case of the extracellular matrix, mainly composed of proteins such as collagen and fibronectin. The latter plays a key role in adhesion of cells to the extracellular matrix, notably thanks to a higher-order geometrical structure that is stabilized by numerous disulfide bonds. Here, we use mass spectrometry techniques to analyse in situ the molecular products of a fibronectin peptide under non-ionizing or ionizing radiation. We find that interaction with a single X-ray photon or carbon ion triggers the ejection of multiple valence electrons due to the decay of core atomic vacancies, a process only reported previously to occur in DNA oligonucleotides. Furthermore, our results strongly suggest that, unlike non-ionizing UV radiation, these ionizing particles do not induce disulfide bond cleavage. This is of key relevance for understanding radiation damage to proteins stabilized by disulfide bonds, in particular extracellular matrix proteins such as fibronectin.