Yoshida H
Health Sciences Research Division, Oak Ridge National Laboratory, Tennessee 37831.
Radiat Res. 1994 Feb;137(2):145-51.
Competition between recombination of the radicals formed in the gamma radiolysis of water (eaq-, OH, H) and the reaction of eaq- with glycylglycine is investigated in glycylglycine solutions of various concentrations and pH. First, the concentration dependence of the ammonia yields is measured in the glycylglycine solutions of between 0.5 mM and 1.0 M. The G values of ammonia appear to reach a plateau of 2.47 +/- 0.05 molecules/100 eV at the low concentrations (1-5 mM) and increase to 3.81 +/- 0.07 molecules/100 eV at the high concentration (1 M). Secondly, the pH dependence of the ammonia yields is measured at low (1 and 5 mM) and high (0.1 and 0.2 M) concentrations of glyclyglycine. For concentrated glyclyglycine solutions, the ammonia yields increase with increasing pH, as expected based on comparison of the probabilities of the competitive reactions. However, the G values of ammonia reach a maximum at pH 9.0 and then decrease as the pH increases for dilute solutions. The lower G values at higher pH for dilute glycylglycine solutions may result from increased interspur recombination since the rate constant for the reaction of eaq- with glycylglycine is decreased and, as a consequence, the scavenging capacity of glycylglycine for eaq- decreases approximately 4.7-fold from low to high pH.
在不同浓度和pH值的甘氨酰甘氨酸溶液中，研究了水的γ辐解产生的自由基（水合电子eaq-、羟基自由基OH、氢自由基H）的复合与eaq-和甘氨酰甘氨酸反应之间的竞争关系。首先，在浓度为0.5 mM至1.0 M的甘氨酰甘氨酸溶液中测量了氨产率的浓度依赖性。在低浓度（1 - 5 mM）下，氨的G值似乎达到2.47±0.05分子/100 eV的平稳值，而在高浓度（1 M）时增加到3.81±0.07分子/100 eV。其次，在低浓度（1和5 mM）和高浓度（0.1和0.2 M）的甘氨酰甘氨酸溶液中测量了氨产率的pH依赖性。对于浓甘氨酰甘氨酸溶液，正如基于竞争反应概率的比较所预期的那样，氨产率随pH值升高而增加。然而，对于稀溶液，氨的G值在pH 9.0时达到最大值，然后随着pH值的进一步升高而降低。稀甘氨酰甘氨酸溶液在较高pH值下较低的G值可能是由于链间复合增加，因为eaq-与甘氨酰甘氨酸反应的速率常数降低，结果，甘氨酰甘氨酸对eaq-的清除能力从低pH到高pH大约降低了4.7倍。
