HIGH FREQUENCY DYNAMIC NUCLEAR POLARIZATION OF BIOLOGICAL SYSTEMS

动态核极化（DNP） 使用高功率回旋共振脉塞（回旋管）的实验 工作在140 GHz。 先前的结果显示NMR信号 -185在甘氨酸的静态CP谱和 -50 - 100的CP/M[AS]光谱的精氨酸和T4-溶菌酶，所有在 甘油/水掺杂4-氨基克里思，20- 50 K。 为了 从纺丝样品中获得详细的结构信息， 再耦合技术必须与DNP结合。 成功 掺入关键取决于稳定的微波功率（即， 稳定的纺丝速度， 一段时间。 我们实施了两项重大改革， 回旋管输出功率的稳定性。 我们把电子 枪与一个配备了较新的阴极杆。 较新的股骨柄 稳定的短期（降解超过一天的长期 脉冲）和长期（发射功率的一般退化 月）的gyrotron的行为。 此外，泵送效率 枪附近的增加，导致最大值下降 在长脉冲期间获得的压力（从10-6 Torr到-10-1Toff） （> 30秒）。 由于输出功率与基础压力成比例， 我们现在可以执行更长的脉冲和/或更高的占空比， 保持稳定的功率输出。 我们还将DNP扩展到 四极核的研究。 由于氧气的重要作用， 多种生物学功能和“0 NMR”的低灵敏度 在实验中，“0”是DNP的特别好的候选者。 初步 在甘油/H2O冷冻溶液上的静态DNP实验， 4-氨基克里思在20 K下产生50-80的信号增强。

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.