Studies of biological effects of vacuum ultraviolet radiation above 50 nm.

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The monochromatic vacuum-ultraviolet (VUV) irradiation system for radiobiological studies installed at BL-5 of the SOR-RING, the Institute for Solid State Physics, the University of Tokyo, was improved as follows. Firstly a 50 1/s ion pump was added to the grating chamber of the monochromator to obtain better vacuum. As a result, decrease of light intensity due to deteriotation of the grating became negligible. Secondly a shutter was replaced by a new high-performance type, which can control irradiation time down to 0.25 sec. Thirdly computor program was improved. The following experiments were performed during 1986 and 1987 fiscal years.Dry samples: Oligonucleotide, dephospho (dA)_2, was irradiated over 55 to 190 nm range and analyzed thin-layer chromatography (T. Ito et al.). Following DNA damages were measured: single-strand breaks detected by agarose gel electrophoresis by K. Hieda (80-255 nm), base release detected by HPLC by K. Hieda (150-190 nm) and thymine-dimer detected by monoclonal antibody by O. Nikaido (150-260 nm). Inactivation of lysozyme by K. Kobayashi for 60-190 nm, inactivation of T_1 phage by H. Maezawa for 50-260 nm and inactivation of Batillus subtilis spore by N. Munakata for 50-300 nm were measured. Conventional absorption measurement on lipid bilayer by T. Megumi and photoacoustic spectrometry of organic film by T. Inagaki were also performed.Solution: OH radical produced by VUV was measured by the spin-trapping method by A. Minegishi. Photolysis of dinucleotide, CpC, by K. Takakura for 150-254 nm.