Ionizing Radiation-induced Changes In The Absorption Spectrum Of Erythrocyte Membrane Proteins

Abstract

Under influence of ionizing radiation different types of oxidative modifications of the protein occur, including carbonylation, direct amino-acid oxidation, oxidative cleavage of the protein backbone, or amino acid side chains. Aromatic amino acids are significantly more reactive with the dominant reaction pathway, including the connection of •OH to the aromatic ring. In the case of Tyr, the connection of •OH and subsequent hydrogen extraction lead to the formation of peroxyl radicals, which in the absence of reductants, form Tyr dimers that are implicated in the formation of intra- and inter-protein linkages [7, 8]. Erythrocyte membrane contains numerous integral membrane proteins, usually, they show absorption maximum between 275 and 280 nm, which are caused by the absorbance of the aromatic amino acids tryptophan (Trp) and tyrosine (Tyr) and, to a small extent, by the absorbance of cystine (i.e., of disulfide bonds). Our study aimed to determine Ionizing radiationinduced changes in the absorption spectrum of erythrocyte membrane proteins.

Mice whole-body irradiation with 137Cs was performed at a dose rate of 1,1Gy/min for the total dose of 5 Gy with a “Gamma-capsule-2”. The Erythrocyte membrane was separated according to Hasts Method and absorbance spectra were measured with a spectrophotometer.

Results show that absorption for proteins of erythrocytes’ membrane at 280 nm wavelength timedependent decreased after irradiation and after one month reaches 75% of the control level. This decrease may be related to Tyr-phosphorylation of B3p in radiation-induced oxidative stress conditions, which markedly reduces its affinity for ankyrin, leading to the release of band 3 from the spectrin/actin membrane skeleton, enhancement of the lateral mobility of band 3 protein in the bilayer, progressive vesiculation and loss from the plasma membrane of radiated cells, triggering a cascade of events inducing alteration of deformability, the resistance of erythrocytes membrane, its destabilization.