Abstract
The present work was undertaken in order to investigate the effects of X-ray radiation upon the pathogenicity and antigenicity of tobacco mosaic virus (TMV).
The virus preparation used in this work was the aqueous suspension of TMV purified by Bawden's procedure. The antiserum was prepared by injecting rabbits with the purified TMV. The infectivity of the irradiated virus was tested by the half-leaf method using Nicotiana glutinosa as assay plants. In serological tests of TMV, the precipitin reaction was used. The virus preparation 2 or 3mm thick in a Petri dish of 5cm in diameter was irradiated at 5cm distance from an anticathode of an X-ray tube run at 60KVP and or 10mA. The mean wave-length of X-ray used in this work was 0.4Å, and dosages measured were 2400r/min. in the case of 15mA and 1600r/min. in that of 10mA. The pH of the virus preparations were 6.0∼6.2 and their temperatures were 14°∼20°C during the irradiations, and as the X-ray tube employed was water-cooled no rising of temperature of the preparations due to the irradiations was recognized.
The results of experiments are summarized as follows:
(1) The non-infective preparations of TMV which had been inactivated by X-ray radiation always showed to be serologically active, and it was moreover found that the serological activities of irradiated preparations increased within the limits of dosage used in the experiments, on the contrary of decreasing of the infectivity (Tables 1 and 2).
(2) The logarithm of the surviving fraction has been plotted against the dosage of irradiation according to the results of the virus activity assay (half-leaf mnethod), and the survival curve was shown by a straight line (Fig. 1 and 2). Consequently, these results seem to agree with the view that the inactivation of virus by ionizing radiation is caused by a single ionization or a single cluster of ionization, as the inactivation follows a simple exponential curve.
(3) The inactivation doses (the 37% doses) were estimated from the above-mentioned curves, to be approximately 28×104r in the case of preparations of 0.2% and 2×104r in the occasion of 0.02%.
