Inactivation of deoxyribonuclease by x-rays. II. The kinetics of inactivation in aqueous solution.
Inactivation of deoxyribonuclease by x-rays. II. The kinetics of inactivation in aqueous solution.
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X 射线使脱氧核糖核酸酶失活。
DOI：
10.1016/0003-9861(57)90249-7
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发表时间：
1957
影响因子：
3.9
通讯作者：
Shigefumi Okada
中科院分区：
文献类型：
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作者：
Shigefumi Okada
1.1.观察到以下三个与 X 射线灭活 DNA 酶浓度相关的现象： 1.1.(a)D37 剂量随着酶浓度的降低而降低，并在较低浓度范围内保持恒定，其中 20% 的酶 (0.5 μg./ml.) 在 100 r 时灭活。 x 射线.1.2.(b) 离子产率随着酶浓度的降低而降低。在酶的中间浓度（8.14 × 10−5M 和 8.14 × 10−6M）中发现了“稀释效应”，即不同浓度溶质的恒定离子产率。1.3.(c) 在浓度范围为 8.14 × 10−9 至 8.14 × 时，相对于 X 射线剂量的酶失活程度是指数函数。 10−5M.2.2。上述三种现象可以根据在普遍稳定状态假设下发展起来的动力学得到令人满意的解释。3.3．发生“稀释效应”的浓度下的离子产率约为0.14，相同浓度范围内的G值约为0.42。动力学表明，与一个酶分子反应的9.3个自由基中只有一个能有效导致酶活性丧失。4.4．自由基失活反应是与酶竞争破坏自由基的反应，属于一级反应而不是二级反应。5.5．有效自由基的百分比，即与酶反应的自由基占产生的自由基总数的100倍，随着浓度的增加而增加。
1.1. The following three phenomena were observed in relation to the inactivation of concentrations of DNase by X-rays:1.1.(a) TheD37dose decreases as the enzyme concentration diminishes and becomes constant in the lower concentration range where 20% of the enzyme (0.5 μg./ml.) was inactivated by 100 r. of x-ray.1.2.(b) The ionic yield decreases with decreasing enzyme concentration. The “dilution effect,” i.e., a constant ionic yield with varying concentrations of solute, is found in the intermediate concentrations of the enzyme (8.14 × 10−5Mand 8.14 × 10−6M).1.3.(c) The degree of enzyme inactivation relative to the x-ray dose is an exponential function at concentrations ranging from 8.14 × 10−9to 8.14 × 10−5M.2.2. The three afore-mentioned phenomena can be interpreted satisfactorily on the basis of the kinetics developed on the assumption of a prevailing steady state.3.3. The ionic yield at concentrations at which the “dilution effect” occurs is about 0.14 and theGvalue at the same range of concentrations is approximately 0.42. The kinetics suggest that only one in 9.3 free radicals which react with one enzyme molecule is effective in causing loss of enzymatic activity.4.4. The deactivation reaction of free radicals, which is the reaction competing with the enzyme for the destruction of the free radicals, was of the first order rather than the second order.5.5. The per cent of the effective free radicals, i.e., 100 times the ratio of free radicals which reacted with the enzyme to total number of free radicals produced, increased with the concentration.