体内31P NMR表面线圈探头的研制

报道一种为进行活体小动物核磁共振实验而研制的体内³¹P NMK表面线圈探头.该探头工作频率为161.83MHz,无载Q值为300,可无损伤地研究生命体内各部位的性质.本文给出了用该探头所测得的小鼠体内肝脏、大腿肌肉、大脑以及大脑缺氧状态下³¹P NMR谱图实例.     

HR/MAS高分辨魔角微量探头用于天然橡胶固体1H、13C NMR测试及其与液体BBO探头、固体CP/MAS探头测试的比较

采用BRUKER高分辨魔角微量探头（HR/MAS），液相宽带BBO探头和固体CP/MAS探头，对天然橡胶固体、乳液以及天然橡胶溶于氘代苯的溶液进行了¹H、¹³C 1D和2D NMR谱的测试和比较. 发现HR/MAS探头用于天然橡胶固体和乳液时可以得到高分辨的¹H、¹³C谱，克服了CP/MAS探头测试固体¹³C NMR谱或者是固体¹H NMR谱时，谱图存在S/N值可能较小、谱峰可能宽化的弱点.     

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.     

非晶态离子导体Li2B2O4的核磁共振研究

本文报道了非晶态离子导体Li₂B₂O₄的⁷Li核磁共振研究。测量了⁷Li核磁共振谱与温度的关系。实验中发现,Li₂B₂O₄的晶态、非晶态和部分晶化样品的⁷Li核磁共振谱有很大的不同,且在部分晶化样品的⁷Li核磁共振谱上有附加的小峰,它与LiCl(Al₂O₃)的⁷Li核磁共振谱上附加的小峰相类似。我们也对非晶态离子导体B₂O₃-0.7Li₂O-0.7LiCl进行了⁷Li核磁共振研究,其结果与上面的类似。研究结果表明,它们都起因于非晶母体与微晶的界面效应。 关键词：     

高分辨魔角旋转核磁共振技术（HR/MAS）在固相合成中的应用

使用微量探头分析了不同树脂、溶剂、温度对¹H NMR线宽的影响，并运用高分辨魔角旋转核磁共振技术跟踪固相载体上羟基氨基酸的糖基化反应. 该研究表明使用高分辨魔角旋转核磁共振探头可以快速、直接鉴定树脂上的产物，是固相合成中重要的分析工具.     

7-氧代-3-苯基香豆素的NMR谱研究

详细归属了三个7-氧代-3-苯基香豆素类衍生物的核磁共振谱(¹1H、¹³C NMR).除7-甲氧基-3-苯基香豆素的¹³C NMR谱外,上述化合物的核磁共振谱均未见报道.     

低温NMR探头的应用

在过去10年中研发新核磁共振探头一直是制造者争夺的活跃领域. 最近，因其灵敏度的巨大提高，低温冷却探头得到人们格外的关注. 利用这一技术可大量节省谱仪机时. 对于低γ核可直接测定天然丰度样品而不必标记，这远比节省机时更为重要. 本文评述了针对5～10 Hz优化2 mg天然丰度噁唑烷酮抗菌素eperezolid的 CIGAR-HMBC-¹H-¹⁵N谱的比较，一个是采自美国瓦里安公司的5 mm低温探头，另一个是采自瓦里安公司传统室温3 mm 梯度三共振探头. 利用低温探头大约10 min就可记录到大部份¹H-¹⁵N远 程相关，26 min可观察到几乎所有的远程共振. 而在同样条件下使用3 mm传统梯度反式三共振探头无法得到有用的谱图，要想取得相同的结果须累加约18 h.     

NMR方法在煤炭分析中的应用进展

简要介绍了核磁共振（NMR）方法在煤炭组成及热解过程分析中的应用. 目前用于煤炭分析的NMR方法主要包括固体NMR和液体NMR. 从检测手段来看,以¹³C NMR和¹H NMR方法较多,¹⁵N NMR, ¹⁹F NMR和³¹P NMR也在煤炭的分析中发挥了重要作用. 其中用于区分和选择性检测不同官能团的NMR谱编辑方法的发展, 进一步推进了NMR在煤炭化工中的应用.     

应用多核固体核磁共振光谱与量子化学计算的方法研究层状的过渡金属硫化物

层状的过渡金属硫化物及其衍生物在许多领域内有着广泛的应用前景. 具体应用包括催化、陶瓷、润滑、能量储存、半导体、电子与光学器件. 该文报道了作者最近用固体核磁共振光谱的方法来表征几种有代表性的过渡金属硫化物(MS₂: M=Zr, Ti, W, Mo和Ta)的结果. 并在不同的磁场强度下（21.1、14.1、9.4 T）成功地获取了³³S, ^47/49Ti,⁹¹Zr,⁹5Mo 在天然丰度下的固体核磁共振光谱. 为了帮助解释实验结果,同时还进行了量子化学计算. 实验及理论计算的结果都表明³³S, ^47/49Ti, ⁹¹Zr, ⁹⁵Mo 的固体核磁共振参数对于这些核的局部几何与电子环境非常敏感.     

[Co(H2O)4(NCS)2](18-C-6)配合物的NMR研究

该文测定了最近合成的[Co(H₂O)₄(NCS)₂](18-C-6)的¹H、¹³C、¹⁴N核磁共振谱,验证了其配合物的结构,并用红外光谱(IR)作了进一步的确定.     

On-line coupling of high temperature GPC and 1H NMR for the analysis of polymers

The on-line coupling of gel permeation chromatography (GPC) and 1H NMR operating at temperatures up to 130 degrees C is presented. A NMR flow probe with a cell volume of 120 microL and a stop-flow valve are developed for on-flow and stop-flow NMR measurements at high temperatures. To maintain high and constant temperatures through the whole probe, the flow probe contains two separate heating circuits. A modified stop-flow valve is developed as a control device for enabling on-flow and stop-flow experiments at high temperature conditions. Heated transfer lines connect the flow probe with the high temperature GPC system. Due to their semicrystalline nature, polyolefins can be studied by liquid chromatography only at temperatures above 100 degrees C. The novel high temperature GPC-NMR system is used for the separation of complex polyolefins regarding their molar mass and for the analysis of different chemical structures. Blends of polyethylene, poly(methyl methacrylate), and ethylene-methyl methacrylate copolymers are separated according to the molar masses of the components. The compositions of the components are directly studied by on-line NMR. Moreover, the chemical composition distribution of an ethylene-methyl methacrylate copolymer sample is analysed. Differences between results of on-flow and stop-flow measurements are discussed.     

High pressure 1D and 2D NMR experiments on model biomembranes

Abstract

We developed a high-pressure high-resolution probe for NMR experiments on biological systems which enabled us to study the phase behaviour of model biomembranes by 1D and 2D NMR experiments at temperatures up to 65°C and at pressures up to 3000 bar.     

High-precision nuclear magnetic resonance probe suitable for in situ studies of high-temperature metallic melts

High-temperature nuclear magnetic resonance (NMR) has proven to be very useful for detecting the temperature-induced structural evolution and dynamics in melts. However, the sensitivity and precision of high-temperature NMR probes are limited. Here we report a sensitive and stable high-temperature NMR probe based on laser-heating, suitable for in situ studies of metallic melts, which can work stably at the temperature of up to 2000 K. In our design, a well-designed optical path and the use of a water-cooled copper radio-frequency (RF) coil significantly optimize the signal-to-noise ratio (S/NR) at high temperatures. Additionally, a precise temperature controlling system with an error of less than ±1 K has been designed. After temperature calibration, the temperature measurement error is controlled within ±2 K. As a performance testing, ²⁷Al NMR spectra are measured in Zr-based metallic glass-forming liquid in situ. Results show that the S/NR reaches 45 within 90 s even when the sample's temperature is up to 1500 K and that the isothermal signal drift is better than 0.001 ppm per hour. This high-temperature NMR probe can be used to clarify some highly debated issues about metallic liquids, such as glass transition and liquid-liquid transition.     

High-Temperature Pulsed-Field-Gradient Multidimensional NMR of Polymers

The application of pulsed-field-gradient (PFG) techniques has been particularly important in providing the ability to detect 2D and 3D NMR cross peaks from minor structural components in synthetic organic polymers. The lack of mobility in a large percentage of polymers leads to rapid T2 relaxation which prevents the use of pulse sequences, such as the HMBC experiment, that operate based on coherence transfer via small, long-range J couplings. High-temperature NMR increases molecular motion with corresponding line narrowing (e.g., polyethylenes are typically analyzed at 120 degrees C). However, until now, the requirement for high temperature has precluded the use of PFG methods. Here we present data from a new probe which is capable of performing high-temperature PFG coherence selection experiments at temperatures typical of those used in many polymer analyses. We illustrate the performance of this probe with PFG-HMBC spectra of a copolymer from ethylene/1-hexene/1-butene at 120 degrees C.     

Capillary scale NMR flow mapping

Stopped-flow NMR at capillary scale has many advantages over traditional methods of introducing the sample into the probe, particularly when large numbers of samples must be examined. This work describes application of a simple method for direct visualization of a sample inside the flow cell of flow NMR systems to capillary scale analysis. We describe the details of the method and show how it can be used to measure the optimum flow rate for a capillary NMR system and how to determine the optimum sampling efficiency for small samples.     

High-pressure,high-resolution NMR probe working at 400 MHZ

Abstract

A probe for obtaining high-resolution multinuclear NMR spectra at elevated pressures with a Bruker AM-400 spectrometer is described. The probe is designed for pressures up to 200 MPa and has been used between -40 to 150°C. We obtain routinely a resolution of about 1 Hz for proton (400 MHz) spectra using deuterium as an internal field lock. This probe is easily interchangeable with a commercial probe. We also describe a simple sample tube made of a 5 mm commercial NMR tube and a machinable glass cap with a total volume of about 1 cm³.     

Determination of moisture fraction in wood by mobile NMR device

A mobile NMR probe has been used as a non-destructive and non-invasive tool for water content analysis on wood samples. The porosity index, express as the fraction of the sensitivity volume of the probe occupied by water, is here proposed as an alternative to the moisture content index, namely the amount of water mass with respect to the mass of dried sample. In principle the method can be applied to any kind of porous media that has not detectable proton signal from the rigid matrix as, for instance, in building materials. In wood, where proton signal can be detected also from cellulose and others macromolecular components, some considerations and artifices are here proposed for eliminating this contribution. The method has allowed performing moisture volume fraction analysis on wood samples characterized by different wood species, cutting and moisture contents. The NMR data of moisture detection as volume fraction have successfully been compared with those obtained by the gravimetric method.     

Radiation damping in microcoil NMR probes

Radiation damping arises from the field induced in the receiver coil by large bulk magnetization and tends to selectively drive this magnetization back to equilibrium much faster than relaxation processes. The demand for increased sensitivity in mass-limited samples has led to the development of microcoil NMR probes that are capable of obtaining high quality NMR spectra with small sample volumes (nL-microL). Microcoil probes are optimized to increase sensitivity by increasing either the sample-to-coil ratio (filling factor) of the probe or quality factor of the detection coil. Though radiation damping effects have been studied in standard NMR probes, these effects have not been measured in the microcoil probes. Here a systematic evaluation of radiation damping effects in a microcoil NMR probe is presented and the results are compared with similar measurements in conventional large volume samples. These results show that radiation-damping effects in microcoil probe is much more pronounced than in 5 mm probes, and that it is critically important to optimize NMR experiments to minimize these effects. As microcoil probes provide better control of the bulk magnetization, with good RF and B0 inhomogeneity, in addition to negligible dipolar field effects due to nearly spherical sample volumes, these probes can be used exclusively to study the complex behavior of radiation damping.     

焙烧对HL沸石结构的影响

运用MAS NMR研究了焙烧对HL沸石结构的影响. 结果表明,高温焙烧将引起HL沸石骨架的脱铝,当焙烧温度高于650 ℃后,沸石骨架脱铝明显;²⁷Al MAS NMR谱表明,从沸石上脱下来的铝,部分形成了NMR不可测的无定形态,且随焙烧温度的升高,NMR不可测铝增多.