Mechanism of the oxygen effect in connection with the irradiation of proteins

Journal Article · Sat Jul 15 04:00:00 EDT 1961 · Bakh Inst. of Biochemistry (U.S.S.R.) (English Translation)

OSTI ID:4011057

Pavlovskaya, T. E.; Pasynskii, A. G.

The oxidation of thiol groups was investigated on solutions of cysteine and egg albumin and also on dry protein preparations following irradiation with x rays or gamma rays ia vacuum, ia a nitrogen atmosphere, and in air (at atmospheric pressure and different partial pressures). A number of the experiments was carnied out by irradiating in the presence of denaturing substances, namely guanidine, HCl, and others. It was demonstrated that reinforcement of the oxidation of SH groups in the air (the oxygen effect) in cysteine solutions can be qualitatively interpreted by assunning an indirect radiation effect in such a manner that the magnitude of the oxygen effect depends on the relation between the substrate concentration and the applied radiation dose; the oxygen effect diminishes when the ratio expressing tbis relation drops. In this sense, the magnitude of the oxygen effect is only relative. In protein solutions the magnitude of the oxygen effect depends to a considerable extent on the hydrogen bonds formed by SH groups. In cases of irradiation in vacuum, in a nitrogen atmosphere, or at an air pressure below 100 mm Hg, the SH groups of protein are not oxidized at all as a result of irradiation at doses up to 600,000 roentgens, following irradiation with which complete oxidation of SH groups is obtained in air. If irradiation in vacuum is carried out in guanidine solutions or irradiation takes place in air (at pressures higher than 350 mm Hg), the oxidation of SH groups proceeds normally, just as in solutions of simple thiol substances, which apparently is a result of the breaking of H-bonds in the protein molecule. Addition of air after irradiation of the protein solution does not change the SH-group titer (i.e., an aftereffect is absent). An oxygen effect associated with the direct action of radiation apparently cannot be explained the formation of free peroxide radicals, because the amount of oxidized SH groups exceeds by two orders of magnitude the total number of radicals that has been measured by the electronic paramagnetic resonance method. The concept is advanced that the oxygen effect associated with the direct action of radiation can be explained by the action of irradiated oxygen (present in the O/sub 2/* or O/sub 2/- form) on the breaking and rearrangement of a number of hydrogen bonds in the protein molecule. (auth)

• NSA Number: NSA-15-025863
• OSTI ID: 4011057
• Journal Information: Bakh Inst. of Biochemistry (U.S.S.R.) (English Translation), Journal Name: Bakh Inst. of Biochemistry (U.S.S.R.) (English Translation) Vol. 26
• Country of Publication: USSR
• Language: English

Related Subjects

AIR
ALBUMINS
ATMOSPHERE
BIOLOGY AND MEDICINE
CYSTEINE
GAMMA RADIATION
HYDROCHLORIC ACID
IRRADIATION
NITROGEN
OXIDATION
OXYGEN
PRESSURE
PROTEINS
RADIATION DOSES
RADIATION EFFECTS
SOLUTIONS
THIOLS
VACUUM
X RADIATION