Does oxygen enhance the radiation-induced inactivation of penicillinase
The radiation-induced inactivation of penicillinase (..beta..-lactamase, EC 3.5.2.6) in dilute aqueous solutions buffered with phosphate was studied by examining enzyme radiosensitivity in the presence of various gases (He, O/sub 2/, H/sub 2/, N/sub 2/O and N/sub 2/O + O/sub 2/). The introduction of either N/sub 2/O or O/sub 2/ was found to reduce the radiodamage. On the other hand, H/sub 2/ or N/sub 2/O + O/sub 2/ gas mixture enhanced the radiosensitivity. In the presence of formate and oxygen no enzyme inactivation was detected. The results indicated that the specific damaging efficiency of H atoms is more than twofold higher than that of OH radicals; therefore, in 50 mM phosphate buffer, where more than half the free radicals are H atoms, the H radicals are responsible for the majority of the damage. The superoxide radicals appeared to be completely inactive and did not contribute to enzyme inactivation. Oxygen affected the radiosensitivity in two ways: (1) it protected by converting e/sub aq//sup -/ and H into harmless O/sub 2/-radicals; and (2) it increased inactivation by enhancing the damage brought about by OH radicals (OER = 2.6). In oxygenated buffer the protection effect of oxygen exceeded that of sensitization, thus giving rise to a moderate overall protection effect.
- Research Organization:
- Hebrew Univ., Jerusalem, Israel
- DOE Contract Number:
- EY(11-1)-3221
- OSTI ID:
- 5099910
- Journal Information:
- Radiat. Res.; (United States), Vol. 82:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
OXYGEN
RADIOSENSITIVITY EFFECTS
PENICILLIN
BIOCHEMICAL REACTION KINETICS
CESIUM 137
CHEMICAL RADIATION EFFECTS
DOSE-RESPONSE RELATIONSHIPS
ENZYME INHIBITORS
EXPERIMENTAL DATA
GAMMA RADIATION
HYDROGEN
INACTIVATION
NITROUS OXIDE
RADICALS
RADIOSENSITIVITY
RESPONSE MODIFYING FACTORS
ALKALI METAL ISOTOPES
ANTIBIOTICS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CESIUM ISOTOPES
CHALCOGENIDES
CHEMISTRY
DATA
DRUGS
ELECTROMAGNETIC RADIATION
ELEMENTS
INFORMATION
IONIZING RADIATIONS
ISOTOPES
KINETICS
NITROGEN COMPOUNDS
NITROGEN OXIDES
NONMETALS
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
OXIDES
OXYGEN COMPOUNDS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIATIONS
RADIOISOTOPES
REACTION KINETICS
YEARS LIVING RADIOISOTOPES
560111* - Radiation Effects on Biochemicals- In Vitro- (-1987)
550200 - Biochemistry