Innovative Instrumentation for High Magnetic Field DNP NMR

拟议的研究重点是创新的仪器，将使根本性的进展 高磁场下的动态核极化(DNP)核磁共振，使这项强大的技术远远 对国内和国际生物医学研究界更容易获得和有用。在DNP中 核磁共振是一种高频微波源，用来照射电子-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对核自旋系统的影响 互动。由此产生的核磁共振信号增强极大地减少了数据采集时间，因此 DNP核磁共振现在被认为是核磁共振波谱学的一个重大进展。最近，新的生物学洞察是 使用DNP在高度复杂的系统上获得，如HIV-1衣壳蛋白，细菌的针状结构 分泌系统或细胞内蛋白质。在强磁场下的DNP实验中，当代的核磁共振 进行了研究，所需的微波频率为太赫兹(THz)：460 GHz、527 GHz G=2电子在700 MHz、800 MHz和900 MHz核磁共振频率下分别为593 GHz和593 GHz。然而， DNP核磁共振信号的增强随着磁场的增加而迅速减弱，相应地 提高微波频率。基于电子自旋的核取向等时间域DNP技术 锁定(新颖)、时间优化(顶部)DNP和集成固体效应(ISE)不会随着增加而下降 因此在强磁场下非常吸引人。然而，这些技术目前正在 由于缺乏高功率、脉冲太赫兹源和 在强磁场下进行脉冲DNP实验所需的仪器。小说需要大兔子 频率(&gt；10 MHz)，以几纳秒的脉冲为单位。所需功率级别在千瓦范围内，并且 在今天的魔术中，由于电磁场耦合到样品中而进一步加剧 角度旋转(MAS)样品架。我们开创性的研究将提供所需的仪器 研制可产生5kW输出功率的脉冲回旋管振荡器的磁场DNP核磁共振 在460 GHz和更高。我们还将开发一种激光驱动的半导体开关，用于形成 新奇实验所需的纳秒尺度脉冲。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序列。我们将演示一种扫频回旋管 通过使用回旋管电子枪的快速电压控制来满足ISE实验的要求。 这项拟议的研究将使用可用的回旋管磁铁、电源和460 GHz DNP核磁共振 加速了光谱仪的研究，降低了成本。这些技术的有效性将得到验证。 在460 GHz的DNP核磁共振实验中，使用可用的光谱仪。总体而言，这些进步将有助于 使高磁场下的DNP/核磁共振在现代生物化学研究中成为更容易获得和更有用的工具。

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.