Barreto J C, Smith G S, Strobel N H, McQuillin P A, Miller T A
Department of Surgery, University of Texas Medical School, Houston 77030.
Life Sci. 1995;56(4):PL89-96. doi: 10.1016/0024-3205(94)00925-2.
Hydroxylation reactions of aromatic compounds have been used to detect hydroxyl radicals produced by gamma irradiation and ultrasound. The present study investigated the suitability of terephthalic acid (THA) as a hydroxyl radical dosimeter for general use in biologically relevant reactions. Hydroxyl radicals were generated by: (1) irradiating THA with a 254 nm ultraviolet light; (2) irradiating with gamma rays from a cesium source; and (3) generating hydroxyl radicals with 1 mM H2O2 and 10 microM Cu+2. In each of the three experiments, a fluorescent product was generated which exhibited identical fluorescent excitation and emission spectra. THA is non-fluorescent, eliminating the problem of a high initial background. Because THA has four identical ring hydrogens, only one mono-hydroxylated isomer was formed. The hydrogen peroxide reaction was dependent on the presence of a metal and cupric ions were effective in enhancing the reaction. With a Cu+2 concentration of 10 microM, the reaction was linear between 0-30 mM H2O2. Catalase abolished the reaction at a concentration of 100 micrograms/ml and the effects could still be observed at 10 ng/ml, consistent with the very high rate at which catalase destroys hydrogen peroxide. Tertbutyl- hydroperoxide did not generate any fluorescence in this system which makes THA a very specific detector of hydroxyl radicals.
芳香族化合物的羟基化反应已被用于检测由γ射线辐照和超声产生的羟基自由基。本研究调查了对苯二甲酸（THA）作为羟基自由基剂量计在生物相关反应中普遍应用的适用性。羟基自由基通过以下方式产生：（1）用254 nm紫外线辐照THA；（2）用铯源的γ射线辐照；以及（3）用1 mM H2O2和10 μM Cu+2产生羟基自由基。在这三个实验中的每一个中，都产生了一种荧光产物，其表现出相同的荧光激发和发射光谱。THA是非荧光性的，消除了高初始背景的问题。由于THA有四个相同的环氢，只形成了一种单羟基化异构体。过氧化氢反应依赖于金属的存在，铜离子在增强反应方面是有效的。当Cu+2浓度为10 μM时，反应在0 - 30 mM H2O2之间呈线性。过氧化氢酶在浓度为100微克/毫升时消除了反应，在10纳克/毫升时仍可观察到其效果，这与过氧化氢酶破坏过氧化氢的非常高的速率一致。叔丁基过氧化氢在该系统中不产生任何荧光，这使得THA成为羟基自由基的一种非常特异的检测器。
