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NMR over nine orders of magnitude in the magnetic field

磁场中超过九个数量级的核磁共振

基本信息

批准号：
EP/V055593/1
负责人：
Malcolm Levitt
金额：
$ 118.61万
依托单位：
University of Southampton
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2021
资助国家：
英国
起止时间：
2021 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FV055593%2F1
关键词：
NMR over nine orders magnitude

项目摘要

Nuclear magnetic resonance (NMR) is one of the most versatile forms of spectroscopy in the physical sciences, with applications spanning the full range from fundamental physics, quantum theory, chemistry, materials science and biochemistry to structural biology and clinical applications (especially in the form of magnetic resonance imaging, MRI). In most cases, NMR spectroscopy employs the strongest possible magnetic field, since this usually generates the strongest signals with high resolution of the different chemical sites of the atomic nuclei. Nevertheless, there are circumstances in which it is desirable to perform NMR over a range of magnetic fields, including the ultralow field regime, in which magnetic shielding is used to achieve very small magnetic fields over three orders of magnitude smaller than the earth's magnetic field. NMR in this ultralow field regime is very special in several ways. Firstly, the information content of the NMR spectrum is determined not by chemical shifts but by spin-spin couplings. Secondly, the line width in this regime is not governed by the magnetic field inhomogeneity, as in ordinary NMR, but by dissipation effects (relaxation). Extremely narrow linewidths (millihertz) are often achieved. Thirdly, the different species of nuclear spins are tightly coupled in the ultralow magnetic field regime, giving rise to the special phenomena such as heteronuclear long-lived states, which do not exist in larger magnetic fields. Fourthly, optical magnetometry techniques may be used to detect the magnetism of the nuclear spins, as opposed to electromagnetic induction, which is used in conventional NMR. The zero-to-ultralow field (ZULF) regime therefore offers a special form of NMR which has a quite different nature to ordinary NMR spectroscopy, and whose features and possibilities are only just starting to be explored. There is currently no equipment in the UK which allows observation of NMR signals in the ultralow magnetic field regime. The proposed research involves the construction of a device which shuttles a sample in a rapid and highly controlled way between the high-field region of an ordinary NMR magnet and a magnetically shielded chamber, equipped with optical magnetometers for the detection of the NMR signal in the ZULF regime. This equipment will allow us to explore the spin dynamics in the ZULF regime with great precision and also exploit the ZULF regime as part of a high-field NMR procedure. This allows numerous multidimensional NMR experiments in which the advantages of both regimes may be combined. In addition the equipment allows the possibility to explore NMR relaxation over a very wide range of magnetic fields, allowing the probing of molecular motion over an extremely wide range of timescales. In addition the equipment will permit the development of advanced methodology for manipulating nuclear spin systems in the ZULF regime, such as the development of "ZULF decoupling" sequences which cause the system to behave as if spin-spin couplings between nuclei of different isotopic types are suppressed. This will make the ZULF NMR signals narrower, more informative, and easier to interpret. The proposed equipment will be world-unique and will be made available to the UK scientific community as a research facility. A workshop and training course will be provided during the final stages of the research project in order to facilitate the transfer of knowledge on this special form of NMR to UK scientists.

核磁共振（NMR）是物理科学中最通用的光谱学形式之一，其应用范围涵盖基础物理学，量子理论，化学，材料科学和生物化学，结构生物学和临床应用（特别是磁共振成像，MRI）。在大多数情况下，NMR光谱法使用最强的磁场，因为这通常会产生最强的信号，并对原子核的不同化学位点具有高分辨率。然而，存在期望在一定范围的磁场上执行NMR的情况，包括超低场状态，其中磁屏蔽用于实现比地球磁场小三个数量级的非常小的磁场。这种超低场区的核磁共振在几个方面非常特殊。首先，NMR谱的信息内容不是由化学位移而是由自旋-自旋耦合决定的。其次，在这个制度的线宽是不受磁场的不均匀性，在普通的NMR，但通过耗散效应（松弛）。通常可以实现极窄的线宽（毫赫兹）。第三，不同种类的核自旋在超低磁场区域中紧密耦合，从而产生在较大磁场中不存在的特殊现象，例如异质长寿命态。第四，与在常规NMR中使用的电磁感应相反，光学磁力测量技术可以用于检测核自旋的磁性。因此，零至超低场（ZULF）制度提供了一种特殊形式的NMR，它与普通NMR光谱学具有完全不同的性质，其特征和可能性才刚刚开始探索。目前，英国还没有设备可以在超低磁场状态下观察核磁共振信号。拟议的研究涉及一种装置的建设，该装置以快速和高度控制的方式在普通NMR磁体的高场区域和磁屏蔽室之间穿梭样品，该磁屏蔽室配备有用于检测ZULF机制中NMR信号的光学磁力计。该设备将使我们能够以极高的精度探索ZULF机制中的自旋动力学，并将ZULF机制作为高场NMR程序的一部分。这允许进行许多多维核磁共振实验，其中可以结合两种方案的优点。此外，该设备允许在非常宽的磁场范围内探索NMR弛豫的可能性，允许在非常宽的时间尺度范围内探测分子运动。此外，该设备将允许开发用于在ZULF制度中操纵核自旋系统的先进方法，例如开发“ZULF去耦”序列，该序列使系统表现得好像不同同位素类型的核之间的自旋-自旋耦合被抑制。这将使ZULF NMR信号更窄，信息更丰富，更容易解释。拟议的设备将是世界上独一无二的，并将作为研究设施提供给英国科学界。在研究项目的最后阶段，将提供一个讲习班和培训课程，以促进向英国科学家转让有关这种特殊形式的核磁共振的知识。