Ando T, Yoshikawa T, Tanigawa T, Kohno M, Yoshida N, Kondo M
Second Department of Internal Medicine, Matsushita Memorial Hospital, Osaka, Japan.
Life Sci. 1997;61(19):1953-9. doi: 10.1016/s0024-3205(97)00835-7.
The mechanism of the generation and the quantitative analysis of singlet oxygen (1O2) formed by the exposure of a hematoporphyrin derivative (HpD) to light was re-evaluated by electron spin resonance (ESR) combined with 2,2,6,6,-tetramethyl-4-piperidine (TMPD). The change from TMPD to 2,2,6,6,-tetramethyl-4-piperidine-N-oxide (TAN) has been reported to depend on singlet oxygen. However, we confirmed that this reagent also react with superoxide anion (O2-) and hydroxyl radicals (OH). Therefore, the reactions between TMPD and 1O2, O2- and OH were re-examined using a kinetic approach. We found that the generation of TAN was proportional to the concentration of TMPD and HpD, as well as to the duration and strength of the illumination. The generation of TAN was not inhibited by dimethyl-sulfoxide (DMSO) or superoxide dismutase (SOD). The reaction rate between TMPD and 1O2 was determined to be 5.0 x 10(-7) M min-1. The generation of 1O2 from HpD was 2.7 x 10(-7) M min-1 under our conditions. The competitive reaction observed between 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and TMPD for O2- or OH shows that TMPD reacts with both forms of active oxygen, but gave no ESR signal. The second-order reaction rate constant of TMPD between O2- and OH was calculated as 73 M-1 s-1 and 1.5 x 10(9) M-1 s-1, respectively. The photochemical generation of 1O2 from methylene blue, another sensitizer, was also demonstrated by this method. These results show that ESR signal of TAN can be used for the highly selective monitoring of 1O2.
通过电子自旋共振（ESR）结合2,2,6,6 - 四甲基 - 4 - 哌啶（TMPD），对血卟啉衍生物（HpD）光照产生单线态氧（1O2）的机制及其定量分析进行了重新评估。据报道，从TMPD到2,2,6,6 - 四甲基 - 4 - 哌啶 - N - 氧化物（TAN）的变化取决于单线态氧。然而，我们证实该试剂也能与超氧阴离子（O2-）和羟基自由基（OH）反应。因此，采用动力学方法重新研究了TMPD与1O2、O2-和OH之间的反应。我们发现TAN的生成与TMPD和HpD的浓度、光照持续时间及强度成正比。TAN的生成不受二甲基亚砜（DMSO）或超氧化物歧化酶（SOD）的抑制。TMPD与1O2之间的反应速率确定为5.0×10（-7）M min-1。在我们的条件下，HpD产生1O2的速率为2.7×10（-7）M min-1。5,5 - 二甲基 - 1 - 吡咯啉 - N - 氧化物（DMPO）和TMPD对O2-或OH的竞争反应表明，TMPD能与两种活性氧形式反应，但未给出ESR信号。TMPD与O2-和OH之间的二级反应速率常数分别计算为73 M-1 s-1和1.5×10（9）M-1 s-1。该方法还证明了另一种敏化剂亚甲蓝光化学产生1O2的过程。这些结果表明，TAN的ESR信号可用于1O2的高选择性监测。
