Radiat Environ Biophys (1989) 28:4258 Radiation and Environmental Biophysics © Springer-Verlag 1989 Radiation-induced changes of structural and functional properties of human hemoglobin IL Structural and functional characterization of irradiated deoxyhemoglobin Z. Szweda-Lewandowska 1, M. Puchata 1, P.A. Osmulski ~, and J. Rosin 2 1 Chair of Biophysics, University of L6d~, ul. Banacha 12/16, PL-90-237 L6d~, Poland 2 Institute of Occupational Medicine, ul. Teresy 8, PL-90-950 g6d~, Poland Received August 26, 1987 / Accepted in revised form May 16, 1988 Summary. Gel filtration and SDS-PAGE separation of hemoglobin (Hb) irradiated under argon or N20 show formation of covalent-aggregated Hb molecules. The production of covalent bonds is attributed mainly to the action of hydroxyl radicals, because addition of ethanol, a scaven- ger of these radicals, suppresses this reaction to a great extent. The oxidized heme iron forming metHb or hemichromes is found in all the separated fractions of irradiated Hb. It is also found that the radiation- modified Hb molecules exhibit a decrease of co-operative binding of oxygen. Introduction Radiolysis of proteins in aqueous solutions is due to their reactions with primary radicals of water. The radicals react with the amino acid residues or with the peptide bonds. The terminal effect of the reactions depends on a kind of protein and conditions employed. Radiation-induced processes of protein cross-linking dominate under anoxic conditions (Boguta et al. 1983; Kamarei and Karel 1983; Kim et al. 1984; Radola 1968; Yamamoto 1977). Reactions of protein degradation, however, predominate in the pres- ence of oxygen (Boguta et al. 1983; Schuessler and Herget 1980; Schuessler and Schilling 1984). Hb aggregation as a result of hydrogen peroxide action was described by Rice and co-workers (1983). The radiation-induced cross- linking of Hb under the anaerobic conditions was also demonstrated (Schuessler and Puchata, unpublished data). In this study, radiation-induced aggregation of human Hb was investigated in the light of structural and functional properties of the native and modified protein molecules. Material and methods Material was collected and purified according to the procedure described in the first part of our study. Employed irradiation conditions, Hb concen-