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Novel Methods for High Resolution NMR in Inhomogeneous Fields

非均匀场高分辨率核磁共振的新方法

基本信息

批准号：
49580800
负责人：
Professor Dr. Steffen Glaser
金额：
--
依托单位：
Professur für Organische Chemie
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2007
资助国家：
德国
起止时间：
2006-12-31 至 2010-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/49580800?language=en
关键词：
Novel Methods Resolution NMR Inhomogeneous

项目摘要

In the proposed work, we plan to develop novel methods for high resolution NMR spectroscopy in inhomogeneous static and radio-frequency fields. High resolution NMR experiments require extremely homogeneous magnetic fields to obtain chemical shift and J coupling information of nuclei, as these interactions are orders of magnitude smaller than the main Zeeman coupling to the external field B0. Achieving such homogeneity is not trivial, especially over relatively large volumes. This usually comes at the cost both in price of NMR systems and in size demanded by NMR magnets. Such homogeneities are not achievable when dealing with spatially heterogeneous tissues or employing remote NMR arrangements. Here we propose to develop very general methods based on time varying 3D gradients and spatially non-selective radio-frequency pulses for learning the distribution of inhomogeneous magnetic fields and then correcting for the phase acquired by the spins due to these inhomogeneities. With this correction, the chemical shift information of the nuclei can be extracted and high resolution spectra can be obtained. These methods can potentially replace dedicated shim coils in inexpensive magnets for specialized applications of traditional NMR or imaging experiments. The proposed methods will also advance the methodology of mobile and ex-situ NMR with applications to materials science, chemical engineering and geosciences, and in process, product and quality control. As a second major component of the proposed work, we plan to develop novel pulse sequences based on methods of optimal control and Fourier synthesis which are robust to Larmor dispersion of spins and rf-inhomogeneities and are significantly shorter than conventional designs used for the same purpose. As NMR spectroscopy at high fields up to 21 Tesla is becoming routine, there are emerging applications that pose new pulse design challenges. These applications include design of broadband excitation or inversion pulses, band selective excitations, decoupling pulse sequences in situations when the bandwidth to be covered is comparable or much larger than the rf power available. A natural choice in these settings is the use of adiabatic pulse sequences which tend to be very long and are not desirable in the presence of large relaxation rates. This makes it desirable to develop pulse sequence designs that are significantly shorter than the conventional methods and offer comparable compensation performance. Here we propose methodologies for the study of such designs. The proposed work will also develop sensitivity enhanced experiments in protein NMR spectroscopy based on these new methods.

在拟议的工作中，我们计划开发新的方法，在不均匀的静态和射频领域的高分辨率NMR光谱。高分辨率NMR实验需要非常均匀的磁场来获得原子核的化学位移和J耦合信息，因为这些相互作用比外部场B0的主要塞曼耦合小几个数量级。实现这样的均匀性并不是微不足道的，特别是在相对较大的体积上。这通常以NMR系统的价格和NMR磁体所需的尺寸为代价。当处理空间异质组织或采用远程NMR布置时，这种同质性是不可实现的。在这里，我们建议开发基于时变3D梯度和空间非选择性射频脉冲的非常通用的方法，用于学习不均匀磁场的分布，然后校正由于这些不均匀性而由自旋获得的相位。通过这种校正，可以提取原子核的化学位移信息，从而获得高分辨率的光谱。这些方法可以潜在地替代廉价磁体中的专用匀场线圈，用于传统NMR或成像实验的专门应用。所提出的方法也将推进移动的和非原位NMR的方法学，其应用于材料科学、化学工程和地球科学，以及过程、产品和质量控制。作为所提出的工作的第二个主要组成部分，我们计划开发新的脉冲序列的基础上的方法，最优控制和傅立叶合成的自旋和射频不均匀性的拉莫尔色散是强大的，并显着短于传统的设计用于相同的目的。随着高达21特斯拉的高场NMR光谱学逐渐成为常规，出现了一些新兴的应用，对脉冲设计提出了新的挑战。这些应用包括宽带激励或反转脉冲的设计，频带选择性激励，当要覆盖的带宽与可用的射频功率相当或远大于可用的射频功率时的去耦脉冲序列。在这些设置中的自然选择是使用绝热脉冲序列，该绝热脉冲序列往往非常长，并且在存在大弛豫速率的情况下是不期望的。这使得期望开发比常规方法明显更短并且提供相当的补偿性能的脉冲序列设计。在这里，我们提出了研究这种设计的方法。拟议的工作还将开发基于这些新方法的蛋白质NMR光谱的灵敏度增强实验。