Co-operative Study on the Mechanisms of DNA Damage Induced by Vacuum-UV above 50 nm.

研究结果如下：（1）发现了分子气体光声测量的一种新现象。由麦克风的方法测量的振幅信号表现出最小值，而不是最大值，对应于在真空紫外（VUV）区域的吸收最大值。(2)自旋捕获法被应用于160 nm光子诱导的固体中核苷酸自由基的测量，但由于强度不足而失败。(3)用高效液相色谱法测定了升华胸腺嘧啶膜的主要光产物：环丁烷型二聚体和（6-4）在150 nm以上和140 nm以下的光产物5-羟甲基尿嘧啶和5-甲酰基尿嘧啶。(4)用特异性单克隆抗体在150 ~ 300 nm处测定了干DNA中形成环丁烷型二聚体和（6-4）光产物的作用光谱。(5)在160和180 nm处测量溶液中DNA的双链断裂（dsb），表明160 nm光子比180 nm光子更有效地诱导dsb。(6)建立了一种测定枯草芽孢杆菌突变体DNA碱基序列的简便方法。初步结果表明，某些类型的罕见突变的选择性诱导紫外线和软X射线在高真空下。(7)在60 nm以上测定了溶菌酶失活和氨基酸降解的作用光谱。

The results of this study are as follows : (1) A new phenomenon was discovered for photoacoustic measurements of molecular gases. The amplitude signals measured by the microphone method exhibited minima, instead of maxima, corresponding to the absorption maxima in the vacuum-UV (VUV) region. (2) The spin-trapping method was applied to measure radicals of nucleotides in solids induced by 160 nm photons, but failed due to insufficient intensity. (3) The main photoproducts of sublimed thymine films were determined by the HPLC method : cyclobutane-type dimers and (6-4) photoproducts above 150 nm and below 140 nm 5-hydroxymethyluracil and 5-formyluracil. (4) The action spectra for forming the cyclobutane-type dimer and (6-4) photoproduct in dry DNA were determined at between 150 and 300 nm by specific monoclonal antibodies. (5) Double-strand breaks (dsb) in DNA in solution were measured at 160 and 180 nm, indicating that dsb was induced more efficiently by 160 nm photons than 180 nm photons. (6) A new simple method which can be used to determine the base sequence of mutant DNA of Bacillus subtilis was developed. The preliminary results indicate that certain types of rare mutations were selectively induced by UV and soft X-rays under high vacuum. (7) The action spectrum for the inactivation of lysozyme and degradation pattern of amino acids was determined above 60 nm.