Radiation damage to proteins: an electron paramagnetic resonance study

Abstract

Exposure of a wide range of proteins to ionizing radiation at low temperatures has led to the following generalizations: (i) Electrons are ejected indiscriminately from any part of the protein. The residual radical cations largely become localized on the backbone amide units, and are trapped thereon by the N–H proton loss. (ii) These centres are characterized by their ¹⁴N hyperfine coupling constants and by coupling to the unique C–H proton. This varies in a manner that is characteristic of α-helical regions and β-sheet regions of the protein. (iii) The ejected electrons, in contrast, are very mobile through the protein until they reach good electron traps, such as transition metal ions or disulfide linkages.