基于多重氢键组装的双杯冠合成及对铯离子的络合

合成了一种基于多重氧键组装形成的新型双杯冠化合物,利用核磁共振氢谱(1H NMR)和碳谱(13C NMR)以及高分辨质谱(ESI-HRMS)对组装前体分子结构进行了表征.通过一维和二维核磁共振氢谱(2D NOESY)研究了该双杯冠的的自组装结构,并采用核磁共振和紫外-可见光谱的方法测定了其对铯离子的络合.实验表明,通过氢键组装形成的双杯冠化合物,由于阻止了单杯冠分子内组装而限制了冠醚环构象改变,其萃取率由单杯冠的82％提高到96％.     

A study of molecular motion in a liquid-crystalline copolyester by broad-line nuclear magnetic resonance

Broad-line nuclear magnetic resonance (NMR) measurements have been carried out for the proton resonance in an oriented liquid-crystalline copolyster prepared from 4-hydroxybenzoic acid (HBA) and 2-hydroxy-6-naphthoic acid (HNA). The Second moments were determined as a function of the angle γ between the specimen orientation direction and the static magnetic field. The low-temperature NMR results are consistent with a rigid structure of random copolymer chains arranged on a hexagonal lattice. As the temperature is raised the NMR signal changes and can be modeled very satisfactorily by considering that there is free rotation of the benzene ring residues about the 1-4 substitution direction. At more elevated temperatures the observed NMR spectra are consistent with rotation of both HBA and HNA groups.     

核磁共振技术(NMR)在组合化学中的应用

对科学产生最大影响的分析方法是核磁共振技术(NMR),它被广泛用于许多领域.本文结合作者的研究结果评述了NMR在组合化学中的应用,着重于NMR在固相合成的应用、液态NMR和NMR在高通量筛选中的应用.     

Computer systems for laboratory networks and high-performance NMR

Modern computer technology is significantly enhancing the associated tasks of spectroscopic data acquisition and data reduction and analysis. Distributed data processing techniques, particularly laboratory computer networking, are rapidly changing the scientist's ability to optimize results from complex experiments. Optimization of nuclear magnetic resonance spectroscopy (NMR) and magnetic resonance imaging (MRI) experimental results requires use of powerful, large-memory (virtual memory preferred) computers with integrated (and supported) high-speed links to magnetic resonance instrumentation. Laboratory architectures with larger computers, in order to extend data reduction capabilities, have facilitated the transition to NMR laboratory computer networking. Examples of a polymer microstructure analysis and in vivo 31P metabolic analysis are given. This paper also discusses laboratory data processing trends anticipated over the next 5-10 years. Full networking of NMR laboratories is just now becoming a reality.     

核磁共振成像(NMRI)在非医学领域中的应用

对核磁共振成像（ＮＭＲＩ）与核磁共振（ＮＭＲ）波谱进行了概括性的比较。重点介绍了当前ＮＭＲＩ在非医学领域最新应用的进展情况，同时对ＮＭＲＩ的发展也做了回顾与展望。     

温敏性纤维素/聚N-异丙基丙烯酰胺复合水凝胶的固体核磁共振表征及动力学研究

利用半互穿网络方法将具有温度响应的高分子聚N-异丙基丙烯酰胺(PNIPAM)与天然纤维素复合得到温敏性水凝胶. 通过固体核磁共振的 ¹H, ¹³C CP/MAS(交叉极化/魔角旋转)和QCP(定量交叉极化)等实验手段对复合凝胶的结构进行了定性及定量研究, 并利用固体静态变温核磁共振实验和偶极滤波-自旋扩散实验研究了复合凝胶中PNIPAM分子链段的动力学行为.     

Constituents of a fern, Davallia mariesii Moore. I. Isolation and structures of davallialactone and a new flavanone glucuronide

A new gamma-lactone derivative named davallialactone (4) and the 7-O-beta-D-glucuronide of (+/-)-eriodictyol (5a) have been isolated from Davallia mariessi Moore along with caffeic acid (1), 4-beta-D-glucopyranosylcaffeic acid (2) and 4-O-beta-D-glucopyranosyl-p-coumaric acid (3). The structures of the new compounds were determined by chemical and spectroscopic methods including two-dimensional nuclear magnetic resonance (2D NMR) techniques, especially 1H-detected heteronuclear multiple-bond multiple-quantum coherence and long-range C-H J-resolved 2D NMR techniques.     

NMR assignments for a helical 40 kDa membrane protein

Backbone nuclear magnetic resonance (NMR) assignments were achieved for diacylglycerol kinase (DAGK) in detergent micelles. DAGK is a homotrimeric integral membrane protein comprised of 121 residue subunits, each having three transmembrane segments. Assignments were made using TROSY-based pulse sequences. DAGK was found to be an almost exclusively helical protein. This work points to the feasibility of both solving the structure of DAGK using solution NMR methods and using NMR as a primary tool in structural studies of other helical integral membrane proteins of similar size and complexity.     

Benchtop 19F NMR spectroscopy as a practical tool for testing of remedial technologies for the degradation of perfluorooctanoic acid,a persistent organic pollutant

The development of effective remedial technologies for the destruction of environmental pollutants requires the ability to clearly monitor degradation processes. Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for understanding reaction progress; however, practical considerations often restrict the application of NMR spectroscopy as a tool to better understand the degradation of environmental pollutants. Chief among these restrictions is the limited access smaller environmental research labs and remediation companies have to suitable NMR facilities. Benchtop NMR spectroscopy is a low-cost and user-friendly approach to acquire much of the same information as conventional nuclear magnetic resonance (NMR) spectroscopy, albeit with reduced sensitivity and resolution. This paper explores the practical application of benchtop NMR spectroscopy to understand the degradation of perfluorooctanoic acid using sodium persulfate, a common reagent for the destruction of groundwater contaminants. It is found that Benchtop ¹⁹F NMR spectroscopy is able to monitor the complete degradation of perfluorooctanoic acid into fluoride; however, the observation of intermediate degradation products formed, which can be observed using a conventional NMR spectrometer, cannot be readily distinguished from the parent compound when measurements are performed using the benchtop instrument. Under certain reaction conditions, the formation of fluorinated structures that are resistant to further degradation is readily observed. Overall, it is shown that benchtop ¹⁹F NMR spectroscopy has potential as a quick and reliable tool to assist in the development of remedial technologies for the degradation of fluorinated contaminants.     

Broadband rotational resonance in solid state NMR spectroscopy

A new technique for restoring nuclear magnetic dipole-dipole couplings under magic-angle spinning (MAS) in solid state nuclear magnetic resonance (NMR) spectroscopy is described and demonstrated. In this technique, called broadband rotational resonance (BroBaRR), the coupling between a pair of nuclear spins with NMR frequency difference close (but not necessarily equal) to the MAS frequency is restored by the application of a train of weak radio-frequency pulses at a carrier frequency close to the average of the two NMR frequencies. Phase or amplitude modulation of the pulse train at half the MAS frequency splits the carrier into sidebands close to the two NMR frequencies. The pulse train then removes offsets from the exact rotational resonance condition, leading to dipolar recoupling over a bandwidth controlled by the amplitude of the pulse train. (13)C NMR experiments on uniformly (15)N,(13)C-labeled L-valineHClH(2)O powder validate the theoretical analysis. BroBaRR will be useful in studies of molecular structures by solid state NMR, for example in the detection of long-range couplings between carbons in uniformly labeled organic and biological materials.     

Preparation and characterization of inclusion complexes of pefloxacin mesylate with three kinds of cyclodextrins

The ability of alpha-cyclodextrin, beta-cyclodextrin and hydroxypropyl-beta-cyclodextrin (alpha-CD, beta-CD and HP-beta-CD) to break pefloxacin mesylate (PM) aggregates by forming inclusion complexes has been studied using 1H NMR (nuclear magnetic resonance spectroscopy), 13C NMR and fluorescence spectra. The inclusion constants are determined to compare the corresponding inclusion capacity. Solid-inclusion complexes of PM with CDs are synthesized by coprecipitation method, and all the inclusion ratios are found to be 1:1. Additionally, spatial characterization of complexes has been proposed based on two-dimensional nuclear magnetic resonance technique (2D NMR) and spatial conformation is also investigated to propose two possible models between PM and CDs.     

Synthesis of a novel naphthyl-based self-catalyzed phthalonitrile polymer

A novel naphthyl-based self-catalyzed phthalonitrile monomer was prepared via nucleophilic displacement reaction. The structure was characterized by Fourier infrared spectrum (FT-IR) and nuclear magnetic resonance (1H NMR). The polymerization mechanism was explored. Thermal properties were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), which demonstrated self-promoted behavior and excellent heat resistance.     

DNA-based magnetic nanoparticle assembly acts as a magnetic relaxation nanoswitch allowing screening of DNA-cleaving agents

Monodisperse magnetic nanoparticles conjugated with complementary oligonucleotide sequences self-assemble into stable magnetic nanoassemblies resulting in a decrease of the spin-spin relaxation times (T2) of neighboring water protons. When these nanoassemblies are treated with a DNA cleaving agent, the nanoparticles become dispersed, switching the T2 of the solution back to original values. These qualities render the developed nanoparticles and their nanoassemblies as magnetic relaxation switches capable of screening for DNA-cleaving compounds by magnetic resonance methods such as MRI and NMR.     

129Xe NMR as a probe of polymer blends

The miscibility of two-component polymer blends has been investigated using xenon-129 (¹²⁹Xe) nuclear magnetic resonance (NMR) to probe the phase morphology. The chemical shift of ¹²⁹Xe dissolved in a given polymer is unique, thus heterogeneous blends with large domain sizes exhibit two ¹²⁹Xe NMR lines. When a single resonance is obtained, the data are consistent with miscibility, yielding an upper bound on the domain size. The temperature dependence of the relative solubilities and chemical shifts of ¹²⁹Xe dissolved in the pure components may allow a determination of the phase morphology in blends exhibiting a single resonance. The method is used to demonstrate that polychloroprene and 25% epoxidized 1,4-polyisoprene form a miscible blend.     

Use of NMR in fish processing optimization: a review of recent progress

The goal of this review is to give an overview of general trends in the application of the NMR related to fish processing and quality and to provide some viewpoints on the current situation. Three novel examples of the application of the methodologies magnetic resonance spectroscopy, magnetic resonance imaging, and low‐field NMR are also presented. The capability of these techniques to be utilized as a tool to optimize fish processing, and thereby improving product quality, as well as to confirm labelling information, are demonstrated. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis of a novel bifunctional oxyammonium-based ionic liquid: Application for the synthesis of pyrano[4,3-b]pyrans and tetrahydrobenzo[b]pyrans

In the present investigation, a novel bifunctional oxyammonium-based ionic liquid, namely, 2,2′-(ethane-1,2-diylbis[oxy])bis(ethan-1-aminium)-2,2,2-trifluoroacetate, was designed and synthesized. The structure of the titled ionic liquid was characterized using Fourier-transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (¹HNMR), carbon nuclear magnetic resonance (¹³CNMR), fluorine nuclear magnetic resonance (¹⁹FNMR), homonuclear COSY nuclear magnetic resonance (NMR), thermogravimetry (TG), derivative thermogravimetry (DTG) analysis, X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The described ionic liquid demonstrated robust catalytic performance in the synthesis of pyrano[4,3-b]pyrans and tetrahydrobenzo[b]pyran derivatives. The ionic liquid presents a high potential of recycling and reusing capability in both types of model reactions.     

Rheo-NMR in food science—Recent opportunities

For over 25 years, nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) techniques have been used to study materials under mechanical deformation. Collectively, these methods are referred to as Rheo-NMR. In many cases, it provides spatially and temporally resolved maps of NMR spectra, intrinsic NMR parameters (such as relaxation times), or motion (such as diffusion or flow). Therefore, Rheo-NMR is complementary to conventional rheological measurements. This review will briefly summarize current capabilities and limitations of Rheo-NMR in the context of material science and food science in particular. It will report on recent advances such as the incorporation of torque sensors or the implementation of large amplitude oscillatory shear and point out future opportunities for Rheo-NMR in food science.     

对羟基苯甲酸／对苯二甲酸／双酚A三元共聚酯的核磁共振表征

对羟基苯甲酸／对苯二甲酸／双酚Ａ三元共聚酯的核磁共振表征吴大诚，谢新光，李瑞霞，王勇（成都科技大学纺织工学院成都６１００６５）周子南，高新风，孝延文，张建国（中国科学院长春应用化学研究所高分子物理开放实验室长春１３００２２）关键词对羟基苯甲酸／对苯二...     

Level Anti‐Crossings are a Key Factor for Understanding para‐Hydrogen‐Induced Hyperpolarization in SABRE Experiments

Various hyperpolarization methods are able to enhance the sensitivity of nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) by several orders of magnitude. Among these methods are para‐hydrogen‐induced polarization (PHIP) and signal amplification by reversible exchange (SABRE), which exploit the strong nuclear alignment of para‐hydrogen. Several SABRE experiments have been reported but, so far, it has not been possible to account for the experimentally observed sign and magnetic‐field dependence of substrate polarization. Herein, we present an analysis based on level anti‐crossings (LACs), which provides a complete understanding of the SABRE effect. The field‐dependence of both net and anti‐phase polarization is measured for several ligands, which can be reproduced by the theory. The similar SABRE field‐dependence for different ligands is also explained. In general, the LAC concept allows complex spin dynamics to be unraveled, and is crucial for optimizing the performance of novel hyperpolarization methods in NMR and MRI techniques.