A study of reactions of N-ethyl malaeimide with cellular fractions during radiosensitization of E. coli B/R

Abstract

E. coli B/r cells γ-irradiated under anoxic conditions and in the presence of NEM showed enhanced damage in terms of their colony-forming ability. Irradiation leads to binding of NEM with cellular macromolecules, particularly proteins. Binding occurs to all amino acid residues. In vitro irradiation of bovine serum albumin in aqueous solution has confirmed this. A reaction between NEM and amino acid radical has been implicated. The binding of NEM with cellular proteins may lead to inactivation of enzymes involved in post-irradiation biochemical processes giving rise to enhanced damage. NEM also reacts with amino acids in the absence of radiation, which may partly explain the residual sensitization noticed in cells treated with NEM. Part of the sensitizing effect of NEM has been shown to be due to its electron affinic property.