Ultrafast nuclear magnetic resonance spectroscopy using parallel detection and DNP enhancement for studies of molecular dynamics

核磁共振是一种光谱技术，它使测量核间距离与化学选择性成为可能。先进技术的设计也可以用来探测大生物分子中的核的连接性，这使得核磁共振成为研究生物分子结构的首选方法。然而，核磁共振对分子动力学的研究，如蛋白质构象、蛋白质折叠或配体-蛋白质结合的变化，仅限于相对较慢的秒级时间尺度。出现这个问题的原因是，在进行另一次核磁共振实验之前，在激发后需要大约一秒钟的延迟，以使核自旋系统恢复平衡。核磁共振的另一个问题是，与其他光谱技术相比，其灵敏度相对较低。通常，为了提高实验的信噪比，需要对信号进行平均，从而产生另一个限制可能的时间分辨率的因素。在这个研究计划中，我们建议结合几种技术来大幅提高核磁共振波谱实验的时间分辨率。我们将在一个专门设计的探针头中使用并行检测来监测六个不同样品位置的核磁共振信号。通过分别开始六个短时间延迟的实验，我们将能够监测样品中的快速分子动力学。这种新型的核磁共振探头将连接到具有六个独立通道的控制台。我们将开发新的程序，最大限度地利用多通道配置来实现尽可能最佳的时间分辨率。为了在拟议的核磁共振实验中最大化信噪比，我们将使用动态核极化(DNP)。这项技术使产生核自旋系统成为可能，与将自旋系统暴露在强磁场中时获得的热极化相比，核自旋系统具有显著更高的极化。DNP依赖于自由基未配对电子与周围核自旋之间的相互作用。如果样品温度在-271摄氏度到20摄氏度之间快速变化，使用DNP的核极化可以增强高达四个数量级。我们将把我们新的并行检测策略集成到DNP-核磁共振原型系统中，该系统设计为在大约1秒内完成这种温度跃升。我们的新技术将在蛋白质-配体相互作用的研究中非常有用。通常，由于缺乏合适的实验方法，这种相互作用中的第一个事件并没有完全被理解。随着我们新技术的成功实施，我们的目标是阐明这种快速的分子动力学过程。

Nuclear Magnetic Resonance (NMR) is a spectroscopy technique which makes it possible to measure inter-nuclear distances in conjunction with chemical selectivity. The design of sophisticated techniques which can be used to probe also the connectivity of nuclei in large biomolecules has made NMR the method of choice in studies of biomolecular structure. However, NMR studies of molecular dynamics such as changes of protein conformation, protein folding or ligand-protein binding are limited to relatively slow time scales of the order of seconds. This problem arises because a delay of approximately one seconds is required after an excitation to allow the nuclear spin system to return to equilibrium before another NMR experiment can be carried out. Another problem in NMR is the relatively low sensitivity in comparison with other spectroscopy techniques. Frequently signal averaging is required to improve the signal-to-noise of an experiment thus creating another factor which limits the possible time resolution. In this research programme we propose to combine several technologies to improve the time resolution of NMR spectroscopy experiments substantially. We will use parallel detection to monitor the NMR signal at six different sample locations in a purpose designed probehead. By starting six experiments separately with short time delays we will be able to monitor fast molecular dynamics within the sample. This novel NMR probehead will be interfaced to a control console with six independent channels. We will develop novel programmes which will take maximal advantage of the multi-channel configuration to achieve the best possible time resolution. To maximise the signal-to-noise in the proposed NMR experiments we will use dynamic nuclear polarisation (DNP). This technology makes it possible to generate nuclear spin systems which have a substantially higher polarisation compared to the thermal polarisation obtained when exposing the spin systems to a strong magnetic field. DNP relies on the interactions between unpaired electrons of a radical and the surrounding nuclear spins.The nuclear polarisation using DNP can be enhanced up to four orders of magnitude if the sample temperature is also changed quickly between -271 degree C and 20 degree C. We will integrate our novel parallel detection strategy in a DNP-NMR prototype system that has been designed to perform this temperature jump in about 1 seconds. Our novel technology will be extremely useful in studies of protein-ligand interactions. Frequently, the first events in such interactions are not complete understood due to a lack of suitable experimental method. With an successful implementation of our novel technology we aim to shed light on such fast molecular dynamic processes.