Thermorestoration of Radiation Damage in Dry Bacterial Spores
Heating dry spores of Bacillus megaterium after anaerobic irradiation without an intervening exposure to air results in a substantial decrease in radiation sensitivity of the spores. This phenomenon, termed thermorestoration, appears to be caused by annealment of long-lived x-rayinduced states which damage the spore through a reaction with oxygen. This annealment proceeds in a simple exponential fashion with time at any given temperature, and rate constants for a number of temperatures were obtained. The annealment constant for thermorestoration varies from about 1.0 min-i at 99 deg C to about 0.0003 min-i at 1 deg C. The apparent energy of activation is 15,890 plus or minus 460 cal; this value clearly differentiates the phenomenon from the small effect of temperature observed during irradiation in this system over the very much larger temperature range of --145 deg C to 35 deg C. The ratio of inactivation constants at any two temperatures below 35 deg C is not changed by thermorestoration, although the numerical values of the constants may be changed by as much as 50%. Also, the transition temperature, below which radiation sensitivity is independent of the temperature during the irradiation, at about -- 145 deg C, is not changed by thermorestoration. (auth)
- Research Organization:
- Argonne National Lab., Ill.
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-14-016568
- OSTI ID:
- 4153031
- Journal Information:
- Radiation Research, Journal Name: Radiation Research Journal Issue: 6 Vol. 12; ISSN 0033-7587
- Publisher:
- Radiation Research Society
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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