固体核磁共振样品制备系统的自主研制

近年来,国内多个科研单位引进了固体核磁共振波谱仪．由于目前固体核磁共振波谱仪还没有国产化,完全依赖进口,因此仪器及配套的样品制备系统价格昂贵．转子是魔角旋转核磁共振实验的关键耗材,其尺寸精密度要求极高,加工难度大．通过分析进口成品3.2 mm固体核磁共振转子及其配套样品制备工具的特性和实际应用需求,改进转子各零部件之间的连接方式,优化转子的密封性,成功实现了固体核磁共振转子和配套样品制备工具箱的自主研制．测试结果表明,自主研制的转子能在12 kHz转速下正常运行,满足常规固体核磁共振实验需求,且配套的样品制备工具箱操作简单,安全可靠．     

19F固体核磁共振技术研究膜蛋白相互作用的进展

固体核磁共振技术因其可实现细胞膜环境中的蛋白质结构研究而广受关注.¹⁹F元素由于灵敏度高、天然丰度高,无生物背景等优点,被广泛应用于生物核磁共振技术中.氟标固体核磁共振技术常被用于细胞膜中蛋白质的相互作用研究,如：抗菌肽与细胞膜的相互作用、聚合膜蛋白结构分析等.此篇综述介绍了常用的蛋白质氟标修饰的实验方法,总结了常用的¹⁹F生物固体核磁共振实验技术,以及介绍了应用¹⁹F固体核磁共振研究膜蛋白的成功案例.此外,此篇综述讨论了¹⁹F固体核磁共振技术在蛋白质研究中的局限性.     

一个核磁共振实验场效应管探头

近年来随着实验技术的发展,核磁共振(NMR)实验方法在各个科学领域内得到广泛的应用,已制成各种测试设备,成为进行物理和化学研究的标准实验方法之一。NMR实验技术不但是直接测定原子核磁矩和研究核结构的准确方法;并且通过对液体或固体样品核磁共振谱线的研究,可以获得物质结构方面的知识;在基本实验测量方面,核磁共振还是精确测     

核磁共振成像教学实验

利用超小型核磁共振成像仪，完成了核磁共振空间编码成像的一系列实验．研究了超小型核磁共振成像仪的性能，并对2种观赏植物、动物骨骼、蛔虫、蚯蚓等生物样品进行了核磁共振成像以及T1加权和氢核密度加权成像．     

高磁场中纳升(Nanoliter)生物组织固态氢谱及代谢研究

在高磁场21.1 T（900 MHz ¹H NMR)的快速魔角旋转条件下,采用商业化的1.6 mm探头, 生物样品可以在≤1 μL(150 nL,约0.15 mg）和较短的时间（数分钟）内获得满意的代谢产物的固体高分辨氢谱,且仅需对1.6 mm样品管稍作改进. 防止生物样品的泄漏和污染是实验成功的关键因素,因此对于生物样品的封装进行了讨论, 同时对于微量生物样品在高磁场下信噪比的优化策略也进行了理论和实验的探讨. 该文介绍了生物样品的高磁场固体NMR谱学方法在代谢组学的应用,并总结了此领域里的最新研究进展.     

核磁共振、X射线小角散射以及计算机模拟相结合构建生物大分子复合物的结构模型

近年来,结构生物学研究越来越注重生物大分子复合物的解析,因为许多重要生物学过程都离不开复合物的参与．溶液核磁共振是目前重要的结构解析方法之一．X射线小角散射(SAXS)作为一种新的结构生物学实验手段,近年来发展迅速．SAXS 能提供生物大分子复合物的较低分辨率结构信息,而核磁共振能解析复合物中各个亚基的原子分辨率结构．此外,通过核磁共振还能得到亚基之间的界面、取向以及距离信息．因此近年来通过计算机模拟,整合核磁共振和 SAXS 不同分辨率的结构信息,可以用来搭建生物大分子复合物的结构模型．该综述重点介绍这方面的研究进展．     

吸收光谱光路的设计与误差

固体、液体和气体物质的吸收光谱是大学普物、光学专业的一个基本实验．如何在普通的设备和实验条件下，较为准确地测量吸收系数？本文从朗伯定律出发，介绍一种“对数测量法”光路．并对实验中出现的“负吸收系数”等误差作了分析．文中还介绍了消除材料样品对探测光的反射误差的固体、液体样品架．     

固体核磁共振技术在气体水合物研究中的应用

气体水合物是在低温高压条件下由气体和水形成的笼型化合物,主要有I型,II型和H型3种晶体结构,而固体核磁共振（solid state NMR）是测定其水合指数、笼占有率等结构参数的重要手段. 该文综述了固体核磁共振技术的原理及其在水合物研究中的应用,着重介绍固体核磁共振在水合物结构表征、气体组分的鉴定、结构转化、以及在水合物生成/分解动力学过程监测方面的研究进展. 同时,对其实验方法及测试条件也进行了详细的探讨.     

仲氢诱导极化增强的核磁共振实验条件优化

仲氢诱导极化(Parahydrogen Induced Polarization, PHIP)技术能够极大地增强核磁共振信号,在化学、生物、医学等多方面具有广阔的应用前景．但在实际应用中,通过PHIP技术获得的核磁共振(NMR)信号增强倍数往往受到实际反应条件的影响．该文中以己炔的加氢反应为例,考察了氢气通入方式、反应温度和反应压强对PHIP实验中核磁共振信号增强倍数的影响．     

基于固体核磁共振技术的固体酸结构、酸性及活性分析

固体酸是工业烃转化和生物质精炼中应用最广泛的非均相催化剂之一，了解它们的局部结构和酸性等性质有利于合理设计高效绿色固体酸催化剂，从而提高目标反应的活性和稳定性.近年来，固体核磁共振波谱在定性和定量表征固体酸的局部结构和酸性方面已显示出巨大的应用潜力，甚至可作为一种标准方法.二维固体核磁共振波谱的应用可以进一步揭示固体酸表面位点的结构对称性和不同位点的空间构效关系，从而加深对“催化剂结构-酸性-活性关系”的理解.在这篇综述中，我们总结了用于固体酸表征的固体核磁共振波谱方法和常规实验操作流程，并着重阐述了在使用和不使用探针分子的情况下，固体核磁共振波谱应用于固体酸局部结构和酸性性质研究的进展.     

Solid-state NMR as an analytical tool: quantitative aspects

Analytical methods based on solid-state NMR are becoming increasingly popular. However, these flourishing activities bring up the issue of how accurately NMR can assess an analyte proportion in a solid sample. The use of a chemical intensity reference for this purpose is a natural but often unsuitable choice, due to sample stability or preciousness. We propose here a protocol to perform quantitative measurements in solid-state NMR, by calibration of the circuit response through a low-power pulse injected during the acquisition (the so-called ERETIC method). Although this method has been in use for some time in liquid-phase and in vivo NMR, we point out here some peculiarities and useful applications typical of solids. Namely, the temperature dependence of the signal intensity imposes care in the application to MAS experiments.     

魔角旋转固体核磁共振探头中转子的研制

转子作为魔角旋转（MAS）探头一个至关重要的部件,是固体样品高速旋转的载体,被广泛应用于各种固体核磁共振（NMR）实验.但国内关于MAS转子的研究极少,以至其长期被国外市场垄断.本文通过对MAS转子的深入研究,设计了常规的4 mm MAS转子;并对MAS转子进行了流固耦合仿真,分析其应力应变大小;同时进行了模态仿真,确定了MAS转子的各阶振型及临界转速;最后制作了转子,进行了转速测试和固体NMR实验.结果表明,本文设计和制作的转子能在14 kHz转速下正常运行,并在4 kHz及12.5 kHz转速下采集了金刚烷标样的¹H NMR信号,结果表明该转子能满足常规固体NMR实验的需求.     

Experimental method for low-temperature reaction studies in sealed samples by 13C CP/MAS NMR

A new, simple, and inexpensive technique is presented for monitoring high-resolution solid-state NMR of ¹³C at temperatures ranging between 85 and 450 K. In this procedure, the reaction conditions are controlled by preparing samples at 77 K in 5 mm NMR tubes, while attached to a vacuum system. The NMR tubes are prefitted with a rotor for spinning. After preparation, the samples are sealed, transferred to the double-resonance MAS NMR probe, and analyzed, all while the sample temperature is maintained as low as 85 K. The spinning rates vary from 3.0 kHz at 85 K to 5.2 kHz at 300 K using nitrogen drive gas. Probe design and performance, sample-preparation procedure, and details of the low-temperature experiment are described. In general, the technique may be applied in studies of low-temperature reaction mechanisms and kinetics. ¹³C CP/MAS spectra of ethylene adsorbed on silica-supported ruthenium catalyst are presented to illustrate its performance and possible application.     

固体核磁共振魔角旋转条件下的定量交叉极化技术(英文)

交叉极化与魔角旋转结合（CP/MAS）的方法已经成为增强固体核磁共振（NMR）检测灵敏度最重要的技术之一.CP/MAS技术的应用大大提高了固体NMR谱图的采集效率.然而,I-S偶极耦合作用、旋转坐标系下的自旋-晶格弛豫、分子运动,以及样品中丰核的分布情况等因素,通常会导致CP/MAS谱图失去定量作用.近年来,多个研究组通过改进或者设计新型固体NMR脉冲序列,获得了基于CP的可用于定量分析的固体NMR谱图.本综述首先简要介绍了CP及CP动力学,随后介绍了一系列基于CP的定量固体NMR信号增强技术,具体包括ramped-amplitude CP（RAMP-CP）、multiple-contact CP、quantification of CP（QCP）、Lee-Goldburg frequency modulated CP（LG-FMCP）和quantitative CP（QUCP）.     

207Pb chemical shift thermometer at high temperature for magic angle spinning experiments

The temperature dependence of 207Pb chemical shift in magic angle spinning (MAS) NMR spectrum of Pb(NO3)2 provides a sensitive method to calibrate sample temperatures in MAS NMR. The temperature dependence is uniform in the temperature range between 30 degrees C and 400 degrees C. The NMR sensitivity and the line width are also favorable.     

The effects of different heat treatment and atmospheres on the NMR signal and structure of TiO2-ZrO2-SiO2 sol-gel materials

The effects of different heat treatment schemes (i.e. successively or directly heated to particular temperatures) and atmospheres (air or nitrogen) on the solid-state NMR spectra obtained from (TiO(2))(0.15)(ZrO(2))(0.05)(SiO(2))(0.80) sol-gel materials are investigated. A combination of 1H, 13C, 17O and 29Si NMR is used. 29Si MAS NMR indicates that the extent of condensation of the silica-based network strongly depends on the maximum temperature the sample has experienced, but the condensation is largely independent of the details of the heat treatment scheme and atmosphere used. For sol-gel produced silicate-based materials the results show that the equilibrium structure at each temperature is reached rapidly compared to the time (2h) spent at that temperature. The 17O NMR results confirm that a nitrogen atmosphere does significantly reduce loss of 17O from the structure but care must be taken since there could be differential loss of 17O from the regions having different local structural characteristics.     

A general protocol for temperature calibration of MAS NMR probes at arbitrary spinning speeds

A protocol using (207)Pb NMR of solid lead nitrate was developed to determine the temperature of magic-angle spinning (MAS) NMR probes over a range of nominal set temperatures and spinning speeds. Using BioMAS and FastMAS probes with typical sample spinning rates of 8 and 35 kHz, respectively, empirical equations were devised to predict the respective sample temperatures. These procedures provide a straightforward recipe for temperature calibration of any MAS probe.     

Supercycled SW(f)-TPPM sequence for heteronuclear dipolar decoupling in solid-state nuclear magnetic resonance

The performance of a supercycled SW(f)-TPPM sequence for heteronuclear dipolar decoupling in solid-state NMR is analyzed here. The decoupling performance of this sequence with respect to experimental parameters, such as, the phase angle, proton offset and MAS frequency is studied. A comparison is made with two other commonly used decoupling schemes in solid-state NMR namely, SPINAL-64 and SW(f)-TPPM, on a sample of U-13C-labeled tyrosine. Our results show that supercycled SW(f)-TPPM performs better than the former sequences. Also, numerical spin dynamics studies are presented which support the experimentally observed efficiency in the decoupling.     

Measurement of sample temperatures under magic-angle spinning from the chemical shift and spin-lattice relaxation rate of 79Br in KBr powder

Accurate determination of sample temperatures in solid state nuclear magnetic resonance (NMR) with magic-angle spinning (MAS) can be problematic, particularly because frictional heating and heating by radio-frequency irradiation can make the internal sample temperature significantly different from the temperature outside the MAS rotor. This paper demonstrates the use of (79)Br chemical shifts and spin-lattice relaxation rates in KBr powder as temperature-dependent parameters for the determination of internal sample temperatures. Advantages of this method include high signal-to-noise, proximity of the (79)Br NMR frequency to that of (13)C, applicability from 20 K to 320 K or higher, and simultaneity with adjustment of the MAS axis direction. We show that spin-lattice relaxation in KBr is driven by a quadrupolar mechanism. We demonstrate a simple approach to including KBr powder in hydrated samples, such as biological membrane samples, hydrated amyloid fibrils, and hydrated microcrystalline proteins, that allows direct assessment of the effects of frictional and radio-frequency heating under experimentally relevant conditions.     

Progress in correlation spectroscopy at ultra-fast magic-angle spinning: basic building blocks and complex experiments for the study of protein structure and dynamics

Recent progress in multi-dimensional solid-state NMR correlation spectroscopy at high static magnetic fields and ultra-fast magic-angle spinning is discussed. A focus of the review is on applications to protein resonance assignment and structure determination as well as on the characterization of protein dynamics in the solid state. First, the consequences of ultra-fast spinning on sensitivity and sample heating are considered. Recoupling and decoupling techniques at ultra-fast MAS are then presented, as well as more complex experiments assembled from these basic building blocks. Furthermore, we discuss new avenues in biomolecular solid-state NMR spectroscopy that become feasible in the ultra-fast spinning regime, such as sensitivity enhancement based on paramagnetic doping, and the prospect of direct proton detection.