Highly Sensitive TM-mode ENDOR and its Biological Applications

为了实现高灵敏度的ENDOR光谱仪及其在生物系统中的应用，我们对其中的电子电路和腔体进行了检测。特别地，利用几种典型的有机自由基，通过重复实际观察，精确地检查了TM模型ENDOR腔，并产生了新腔。我们最终获得了超过3000的高负载q值，这是高灵敏度和低信噪比的重要原因。所研究的体系有位阻2-甲基二苯甲酮阴离子自由基、一氧化氮（NO）清除剂4,4,5,5-四甲基咪唑-1,3-氧基、伍斯特蓝阳离子自由基等。在位阻体系中，由于存在大量的非等效质子，导致谱线较宽。在我们的案例中，我们可以解析8-9条线，允许完美的ESR分析，并详细讨论了受阻旋转机制。NO捕集清除剂的^1H-和^<14>N-ENDOR光谱揭示了NO在生物系统中的重要作用。此外，还证实了平面细胞结合tm模腔对研究生物重要自由基具有强大的作用，这些自由基有时会导致低q值，从而导致ENDOR灵敏度低。

In order to accomplish a high sensitive ENDOR spectrometer and its development into biological systems, we examined electronis circuits and a cavity therein. In particular, a TM mode-type ENDOR cavity was precisely checked and newly produced by repeating actual observations using several of the typical organic radicals. We finally obtained high loaded Q-value amounting to more than 3000, which essentially contributes ro the high sensitivity and low signal-to-noise ratio.Systems investigated were sterically hindeered 2-methylbenzophenone anion radical, nitric oxide (NO) scavebger 4,4,5,5-tetramethyl imidazoline-1,3-oxyl, Wurster's blue cation radical and so forth. In the sterically hindered system, there are lot of non-equivalent protons resulting in broad ESR lines. In our case we could resolve 8-9 lines which allowed perfect ESR analysis, and a hindered rotation mechanism was discussed in detail. ^1H- and ^<14>N-ENDOR spectra of NO-trapping scavenger revealed an important role of NO in the biological systems. In addition, it was established that a flat cell combined with the TM-mode cavity is powerful to study the biological important radicals, which sometimes cause low Q-value and therefore low sensitivity in ENDOR.