Innovative Instrumentation for High Magnetic Field DNP NMR

拟议的研究重点是创新的仪器，这将使根本性的进步， 在高磁场下的动态核极化（DNP）NMR领域，使这种强大的技术远 更容易获得和有用的国家和国际生物医学研究界。在DNP NMR，一种高频微波源，用于辐射电子-核跃迁，从而转移 电子自旋库中的高自旋极化通过超精细和偶极到达核自旋系统 交互.由此产生的NMR信号的增强显著减少了数据采集时间，从而 DNP NMR现在被认为是NMR光谱学的一个重大进展。最近，新的生物学见解， 使用DNP在高度复杂的系统如HIV-1衣壳蛋白上获得，来自细菌的针状结构， 分泌系统或细胞内蛋白质。在高磁场下的DNP实验中， 进行研究时，所需的微波频率在太赫兹（THz）范围内：460 GHz、527 GHz 在700 MHz、800 MHz和900 MHz ~ 1H NMR频率下，g=2电子的频率分别为593 GHz和593 GHz。然而，在这方面， DNP NMR信号的增强福尔斯随着磁场的增加而迅速下降 提高微波频率。时域DNP技术，例如通过电子自旋的核取向 锁定（NOVEL），时间优化（TOP）DNP和集成固体效果（伊势）不会随着时间的增加而下降。 磁场，因此在高磁场下非常有吸引力。然而，这些技术目前 由于缺乏高功率脉冲THz源， 在高磁场下进行脉冲DNP实验所需的仪器。NOVEL需要大拉比 频率（>10 MHz），脉冲数纳秒。所需的功率水平在千瓦范围内， 在当今的魔术中， 角旋压（MAS）样品架。我们的开创性研究将提供高性能所需的仪器 通过开发能够产生> 5 kW输出功率的脉冲回旋管振荡器实现磁场DNP NMR 460 GHz及以上。我们还将开发一种激光驱动的半导体开关，用于形成 纳秒级的脉冲需要为NOVEL实验。对于TOP DNP，我们将使用回旋管的反射 输出以产生所需的纳秒级脉冲串。我们将演示一个扫频回旋管 通过对回旋管电子枪的快速电压控制，使电源满足伊势实验的要求。 拟议的研究将使用现有的回旋磁铁，电源和460 GHz的DNP NMR 光谱仪，以加快研究和降低成本。这些技术的有效性将得到证明 在DNP NMR实验中，在460 GHz下使用可用的光谱仪。总的来说，这些进步将有助于 使高磁场下的DNP/NMR成为现代生物化学研究中更容易获得和有用的工具。

The proposed research is focused on innovative instrumentation that will enable fundamental advances in the field of Dynamic Nuclear Polarization (DNP) NMR at high magnetic fields, making this powerful technique far more readily available and useful to the national and international biomedical research communities. In DNP NMR, a high frequency microwave source is used to irradiate electron - nuclear transitions, thereby transferring the high spin polarization in the electron spin reservoir to the nuclear spin system through hyperfine and dipolar interactions. The resulting enhancements in NMR signals dramatically reduce data acquisition times, and thus DNP NMR is now considered a major advance in NMR spectroscopy. Recently, new biological insights were obtained using DNP on highly complex systems like HIV-1 capsid proteins, needle-like structures from bacterial secretion systems or in-cell proteins. In DNP experiments at the high magnetic fields where contemporary NMR research is conducted, the required microwave frequency is in the terahertz (THz) regime: 460 GHz, 527 GHz and 593 GHz for g=2 electrons at 700 MHz, 800 MHz and 900 MHz 1H NMR frequencies respectively. However, the enhancement in the DNP NMR signal falls off rapidly with increasing magnetic field and correspondingly increasing microwave frequency. Time domain DNP techniques such as Nuclear Orientation via Electron Spin Locking (NOVEL), Time Optimized (TOP) DNP and the Integrated Solid Effect (ISE) do not fall off with increasing magnetic field and are thus very attractive at high magnetic fields. However, these techniques are currently limited to low magnetic field NMR spectrometers due to the lack of the high power, pulsed THz sources and instrumentation required to perform pulsed DNP experiments at high magnetic field. NOVEL requires large Rabi frequencies (>10 MHz) in pulses of a few nanoseconds. The required power levels are in the kilowatt range and are further exacerbated by the poor electromagnetic field coupling into the sample in the present-day magic angle spinning (MAS) sample holders. Our pioneering research will provide the instrumentation needed for high magnetic field DNP NMR by developing pulsed gyrotron oscillators capable of generating > 5 kW output power at 460 GHz and higher. We will also develop a laser driven semiconductor switch that will be used to form the nanosecond scale pulses needed for NOVEL experiments. For TOP DNP, we will use reflection of the gyrotron output to produce the required train of nanosecond scale pulses. We will demonstrate a frequency swept gyrotron source by using fast voltage control of the gyrotron’s electron gun to meet the requirements of ISE experiments. The proposed research will use available gyrotron magnets, power supplies and a 460 GHz DNP NMR spectrometer to speed up the research and reduce costs. The efficacy of these techniques will be demonstrated in DNP NMR experiments at 460 GHz using an available spectrometer. Collectively, these advances will help make DNP/NMR at high magnetic field a far more accessible and useful tool in modern biochemistry research.