REPAIR OF DNA DOUBLE-STRAND BREAKS AS A DETERMINATION OF RBE OF ALPHA PARTICLES
The role of repair contributing to the actual value temperature sensitive yeast mutant (rad 54-3/rad 54-3). This mutant is proficient in the repair of DNA double- strand breaks (dsb) at the permissive temperature of 23betaC at which it yields a shouldered survival curve. In contrast, this mutant is dsb repair deficient at the restrictive temperature of 36betaC at which it yields an exponential survival curve. At the permissive temperature the rad-3 mutant shows liquid holding recovery (LHR) of colony forming ability as a function of the liquid holding period. Thus, with this mutant it is possible to obtain survival curves, involving repair of dsb (immediate plating, 36betaC), partial repair of dsb (immediate plating, 23betaC) and gradually increased levels of dsb repair by delayed plating after liquid holding periods of 24, 48 and 72 h. The RBE values of densely ionizing alpha particles (mean restricted LET: 65 KeV/mum) in relation to sparsely ionizing 30 MeV electrons (mean restricted LET: 0.1 KeV/mum) have been determined as a function of the level of dsb repair by using the rad 54-3 mutant. The results are: 1. The RBE value is low and independent of dose when no repair of dsb is involved. 2. The RBE value for a given surviving fraction becomes gradually larger with a gradual increase in the level of dsb repair.
Bibliographic Reference: 11TH GRAY CONFERENCE, GLASGOW (SCOTLAND), JULY 18-22, 1983 BR. J. CANCER, VOL. 49 (1984), SUPPLEMENT VI, PP. 169-173
Record Number: 1989122081400 / Last updated on: 1987-01-01
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