Radiation Effects on Erythrocyte Membrane Structure Studied by the Intrinsic Fluorescence

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Abstract
The changes in the intrinsic fluorescence, primarily from tryptophan residues, of sheep erythrocyte membranes following X-irradiation (0-4000 R) were investigated. There was a decrease in the intensity of fluorescence with increasing dose of X-rays, a small shift of fluorescence emission to longer wavelengths, and a decrease in the fluorescence polarization. Treatment of membranes with a perturbing solvent, 2-chloroethanol, can eliminate the effects of X-rays. The amount of tryptophan in the membranes was not altered after X-irradiation. Sulfhydryl reagents, N-ethylmaleimide and 2,2''-dithiodipyridine, induced similar fluorescence changes. The fluorescence changes could result from a change in the environment surrounding tryptophan residues, from being relatively non-polar to being more polar, implying that conformational changes of membrane proteins are brought about by low doses of X-rays.