Sulfhydryl protection and the oxygen effect on radiation-induced inactivation of r-chromatin in vitro. Influence of an OH scavenger: t-butanol
Transcriptionally active r-chromatin from Tetrahymena has been irradiated in dilute phosphate buffer, pH 7.2, in the presence of the sulfhydryl compound 2-mercaptoethanol (MSH). MSH was more protective against radiation-induced inactivation of transcription under N/sub 2/ than under O/sub 2/. The OH scavenger, t-butanol, on the other hand, gives significantly less protection under N/sub 2/ than under O/sub 2/, apparently due to inactivation by secondary t-butanol radicals under anoxia as shown previously. However, MSH was found to restore most of the protective effect of t-butanol under N/sub 2/. Inactivation was studied as a function of MSH concentration (0.03-10 mM) at different, fixed concentrations of t-butanol (3-300 mM). The observed protection may be explained essentially in terms of (1) OH scavenging, (2) repair of DNA radicals by H-atom transfer from MSH under N/sub 2/ in competition with fixation of damage under O/sub 2/, and (3) protection against inactivation by secondary t-butanol radicals by H-atom transfer to these radicals. The sensitizing effect of oxygen in the presence of MSH is reduced by t-butanol and may even be reversed to produce an apparently protective effect. This finding is discussed in terms of residual inactivation by secondary radicals. The significance of OH scavengers as potential modifiers of oxygen enhancement ratio values is discussed.
- Research Organization:
- Univ. of Aarhus (Denmark)
- OSTI ID:
- 7184852
- Journal Information:
- Radiat. Res.; (United States), Vol. 115:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BUTANOLS
RADIOSENSITIVITY EFFECTS
CHROMATIN
CHEMICAL RADIATION EFFECTS
OXYGEN
THIOLS
BIOLOGICAL RADIATION EFFECTS
DNA REPAIR
ELECTRONS
ENERGY TRANSFER
OXYGEN ENHANCEMENT RATIO
RADICALS
TETRAHYMENA
TRANSCRIPTION
ALCOHOLS
ANIMALS
BIOLOGICAL EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CHEMISTRY
CILIATA
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
HYDROXY COMPOUNDS
INVERTEBRATES
LEPTONS
MICROORGANISMS
NONMETALS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PROTOZOA
RADIATION CHEMISTRY
RADIATION EFFECTS
RECOVERY
REPAIR
560120* - Radiation Effects on Biochemicals
Cells
& Tissue Culture