HIGH FREQUENCY DYNAMIC NUCLEAR POLARIZATION OF BIOLOGICAL SYSTEMS

我们一直在进行动态核极化(DNP) 使用高功率回旋共振脉泽(回旋管)的实验 工作频率为140 GHz。之前的结果显示了核磁共振信号 -185在甘氨酸和甘氨酸的静态CP谱中的增强作用 -50-100为CP/M[作为精氨酸和T4-溶菌酶的光谱，均在 甘油/水掺杂4-氨基TEMPO，在20-50K。为了 从旋转样品中获取详细的结构信息， 重新连接技术必须与DNP结合在一起。成功 掺入严重依赖于稳定的微波功率(即 持续增强)和稳定的旋转速度 一段时间。我们已实施了两项重大改革，以改善 回旋管输出功率的稳定性。我们已经取代了电子 一支喷枪配有较新的阴极杆。较新的阀杆有 在短期内稳定下来(一天的长期退化 脉冲)和长期(发射功率的总体劣化 几个月)回旋管的行为。此外，抽水效率 附近的枪已经增加，导致最大值下降 长脉冲期间获得的压力(从_10-6Torr到-10-‘Toff (&gt；30s)。由于输出功率与基本压力成正比， 我们现在可以执行更长的脉冲和/或更高的占空比，同时 保持稳定的功率输出。我们还将DNP扩展到 四极核的研究。由于氧气在人体内的关键作用 众多的生物功能和“0-核磁共振”的低灵敏度 实验，0是DNP的一个特别好的候选者。 甘油/H_2“O冷冻溶液中掺杂的静态DNP实验 4-氨基TEMPO在20K时信号增强50-80倍。

We have been performing Dynamic Nuclear Polarization (DNP) experiments using a high-power cyclotron resonance maser (gyrotron) operating at 140 GHz. Previous results have shown NMR signal enhancements of -185 in the static CP spectrum of glycine and of -50-100 for the CP/M[AS spectra of arginine and T4-lysozyme, all in glycerol/water doped with 4-amino TEMPO, at 20-50K. In order to obtain detailed structural information from spinning samples, recoupling techniques must be incorporated with DNP. Successful incorporation is critically dependent on stable microwave power (i.e. constant enhancements) and stable spinning speeds over extended periods of time. We have implemented two ma or changes to improve the stability of the gyrotron output power. We have replaced the electron gun with one equipped with a newer cathode stem. The newer stem has stabilized both the short term (degradation over a day of long pulsing) and the long term (general degradation of emitted power over months) behavior of the gyrotron. In addition, the pumping efficiency near the gun has been increased, leading to a decrease in the maximum pressure (from _ 10-6 Torr to -10-' Toff) attained during long pulse (>30s). Since the output power is proportional to the base pressure, we can now perform longer pulses and/or higher duty cycles while maintaining a stable power output. We have also extended DNP to the study of quadrupolar nuclei. Due to the crucial role of oxygen in numerous biological functions and the low sensitivity of "0 NMR experiments, "0 is a particularly good candidate for DNP. Preliminary static DNP experiments on a glycerol/H2"O frozen solution doped with 4-amino TEMPO produced signal enhancements of 50-80 at 20K.