新型葫芦[6]脲纳米颗粒超极化129Xe"分子笼"研究

在相同浓度下,超极化¹²⁹Xe的核磁共振（NMR）灵敏度是传统质子NMR的10 000倍以上,但单原子Xe不具有靶向性,只有单一NMR信号.若超极化¹²⁹Xe与“分子笼”相结合,就能获得新的“笼”内Xe信号,为发展超极化¹²⁹Xe分子探针奠定基础.因此,构建新型的“分子笼”是发展新型超极化¹²⁹Xe分子探针的一个重要方向.葫芦[6]脲纳米颗粒的出现能改善以葫芦[6]脲为主体的¹²⁹Xe分子探针水溶性差、信号弱等缺点.本文构建了水溶性的葫芦[6]脲纳米颗粒,并发现其具有葫芦[6]脲/纳米颗粒内部两个“笼”内¹²⁹Xe信号.这一发现使这种纳米颗粒具有成为超极化¹²⁹Xe分子探针的潜力,能降低检测结果中假阳性和假阴性的发生率,值得更深入的探索和研究.     

新型C10高碳糖的NMR和ESI-MS/MS研究

利用1,2-异丙基-5位苯甲酰基α-D-呋喃型木糖合成了具有潜在抗菌活性的C10高碳糖,检测了该化合物的¹H、¹³C NMR和ESI-MS/MS图谱,确证了该化合物的结构,通过DEPT和¹H-¹H COSY,HMQC,HMBC等2D NMR技术对其¹H和¹³C NMR数据进行了全归属和较详细的解析并探讨了其ESI-MS/MS质谱裂解规律.     

Selective saturation in strongly inhomogeneous magnetic fields

The possibility to produce selective saturation by nuclear magnetic resonance (NMR) sequences of low-power radio-frequency pulses in strongly inhomogeneous magnetic fields is explored. The saturation of parts of the sensitive volume is produced by a particular pulse sequence with reduced amplitude distribution and the spectrum of the recorded signal is compared with the simulated spectrum. The spectra of the recorded free induction decays and echo signals are in good agreement with the simulated spectra of the pulse sequence, which demonstrates the effect of the selective saturation. The results obtained are an important step towards the development of new mobile and lowpower NMR equipments operating with inhomogeneous magnetic fields.     

不均匀不稳定磁场下高分辨液体核磁共振新技术的研究进展

高分辨核磁共振（Nuclear Magnetic Resonance,NMR）谱的获得通常需要高度稳定且均匀的强静磁场. 阻抗磁体或阻抗－超导混合磁体可获得比超导磁体高得多的磁场, 但它们的磁场的稳定性与均匀性比较差;另一方面, 在活体定域波谱研究中,样品内部组分的磁化率差异,运动或生理活动等作用将不可避免地导致磁场的不均匀不稳定,并且这些不稳定不均匀性无法通过锁场匀场等传统的方法消除. 基于分子间零量子相干的方法、空间编码单扫描快速方法、反卷积技术等日渐成为在不均匀不稳定磁场下获取高分辨率的NMR谱的研究热点.     

High-field NMR using resistive and hybrid magnets

Resistive and resistive-superconducting hybrid magnets can generate dc magnetic fields much higher than conventional superconducting NMR magnets but the field spatial homogeneity and temporal stability are usually not sufficient for high-resolution NMR experiments. Hardware and technique development addressing these issues are presented for high-resolution NMR at magnetic fields up to 40T. Passive ferromagnetic shimming and magic-angle spinning are used effectively to reduce the broadening from inhomogeneous magnetic field. A phase correction technique based on simultaneous heteronuclear detection is developed to compensate magnetic field fluctuations to achieve high spectral resolution.     

63Cu NMR evidence for enhanced antiferromagnetic correlations around Zn impurities in YBa2Cu3O6.7

Doping the high- T(c) superconductor YBa2Cu3O6.7 with 1.5% of nonmagnetic Zn impurities in CuO2 planes is shown to produce a considerable broadening of 63Cu NMR spectra, as well as an increase of low-energy magnetic fluctuations detected in 63Cu spin-lattice relaxation measurements. A model-independent analysis demonstrates that these effects are due to the development of staggered magnetic moments on many Cu sites around each Zn and that the Zn-induced moment in the bulk susceptibility might be explained by this staggered magnetization. Several implications of these enhanced antiferromagnetic correlations are discussed.     

Enhancement of SQUID-detected NMR signals with hyperpolarized liquid 129Xe in a 1 microT magnetic field

We report an enhancement of proton NMR signals by a factor of 10(6) by cross polarization with hyperpolarized liquid 129Xe in an ultralow magnetic field of 1 microT. The NMR signals from cyclopentane, acetone, and methanol are detected using a commercial high-T(c) SQUID magnetometer with a signal-to-noise ratio of up to 1000 from a single 90 degrees tipping pulse. This technique allows a wide range of low-field NMR measurements and is promising for the detection of intermolecular scalar spin-spin couplings. Scalar intermolecular couplings can produce a shift of the average NMR frequency in a hyperpolarized sample even in the presence of rapid chemical exchange.     

Optical ac Stark Effect in ~(23)Na NMR Spectra

1.ＩＮＴＲＯＤＵＣＴＩＯＮＯｐｔｉｃａｌａｃＳｔａｒｋｅｆｆｅｃｔ(ａｌｓｏｓｉｍｐｌｙｃａｌｌｅｄａｓｌｉｇｈｔｓｈｉｆｔ),ａｓａｎｉｎｔｅｒｅｓｔｉｎｇｆｉｅｌｄｏｆｉｎｖｅｓｔｉｇａｔｉｏｎｆｏｒｔｅｓｔｉｎｇｔｈｅｆｕｎｄａｍｅｎｔａｌｔｈｅ?..     

In vitro NMR investigation of controlled single and repeated isoflurane anesthesia.

Immobilization of laboratory animals is a basic requirement for experimental in vivo NMR measurements. The effect of single and repeated isoflurane anesthesia on proton NMR relaxation times T1 and T2 in rat liver was studied. Furthermore, physiological monitoring was performed to evaluate the influence of isoflurane anesthesia (up to 2 hr) on biological parameters. Neither single nor repeated isoflurane application over the observed time produce relevant alterations of physiological parameters or relaxation times, compared with untreated control groups. Therefore, we conclude that isoflurane anesthesia is appropriate for in vivo NMR investigations, especially of the liver.     

Portable, low-cost NMR with laser-lathe lithography produced microcoils

Nuclear Magnetic Resonance (NMR) is unsurpassed in its ability to non-destructively probe chemical identity. Portable, low-cost NMR sensors would enable on-site identification of potentially hazardous substances, as well as the study of samples in a variety of industrial applications. Recent developments in RF microcoil construction (i.e. coils much smaller than the standard 5mm NMR RF coils), have dramatically increased NMR sensitivity and decreased the limits-of-detection (LOD). We are using advances in laser pantographic microfabrication techniques, unique to LLNL, to produce RF microcoils for field deployable, high sensitivity NMR-based detectors. This same fabrication technique can be used to produce imaging coils for MRI as well as for standard hardware shimming or "ex-situ" shimming of field inhomogeneities typically associated with inexpensive magnets. This paper describes a portable NMR system based on the use of a 2 kg hand-held permanent magnet, laser-fabricated microcoils, and a compact spectrometer. The main limitations for such a system are the low resolution and sensitivity associated with the low field values and quality of small permanent magnets, as well as the lack of large amounts of sample of interest in most cases. The focus of the paper is on the setting up of this system, initial results, sensitivity measurements, discussion of the limitations and future plans. The results, even though preliminary, are promising and provide the foundation for developing a portable, inexpensive NMR system for chemical analysis. Such a system will be ideal for chemical identification of trace substances on site.     

F 2-FDG NMR imaging of the brain in rat

Images of the rat head reflecting glucose utilization were obtained using 2-fluoro-2-deoxy-D-glucose (2-FDG) and ¹⁹F nuclear magnetic resonance (NMR) imaging. Spatial heterogeneity of glucose utilization in the rat head was clearly demonstrated showing significantly higher glucose utilization in the brain as compared to the surrounding tissues. Although the potential adverse effects of the high doses of 2-FDG (400 mg/kg) needed to perform the study preclude immediate application of this technique to clinical quantitative glucose utilization studies, the present study shows potential for future development of glucose utilization imaging by NMR.     

Three-dimensional correlation by combination of 2D NMR spectra

A method is proposed to make automatic structure elucidation and identification more reliable and unambiguous. Space correlation is utilized to map spin systems and to produce data banks on the basis of pattern recognition. The essence of the method presented is the mathematical combination of the measured 2D NMR spectra, but further extensions are also possible. From the correlation solid constructed in this way, the entire hidden information content of the individual 2D NMR spectra can be extracted.     

无规立构聚乙烯醇缩酮环结构13C NMR研究Ⅱ.各种环浓度测定与估算

报道了用¹³C NMR研究不同聚合度无规立构聚乙烯醇与丙酮、丁酮反应所形成缩酮环的结构及浓度,并与理论估算值进行了比较,讨论了实际成环浓度与理论值差别的原因,并根据不同聚合度PVA缩酮化结果发现PVA缩酮化反应存在一个临界聚合度No。     

Solvent-localized NMR spectroscopy using the distant dipolar field: a method for NMR separations with a single gradient

Solvent-localized NMR (SOLO) is a new method which allows the separation of NMR spectra of substances dissolved in different solvents. It uses the selective HOMOGENIZED pulse sequence to produce a two-dimensional NMR spectrum resulting from intermolecular zero-quantum coherences in one distinct solvent. The detected signal is locally refocused by the action of the distant dipolar field, which is created by a frequency selective pulse only in regions containing the selected solvent. The prerequisites are that the different solvents have sufficiently different chemical shifts to be excited separately and that compartments with different solvents are spatially separated by more than the typical diffusion distance. Here, the method is demonstrated for the solvents water and DMSO on a length scale of 0.5 mm. Because signal in the spectra is refocused locally, SOLO is insensitive to variations in the magnetic field which may result from inhomogeneities or structures in the sample. This makes applications in strongly structured samples possible. SOLO is the first method that achieves localization of NMR signal with a single gradient pulse. Therefore, it can be used in conventional NMR spectrometers with one-axis gradient systems and lends itself to a wide range of applications including in vivo NMR.     

NMR studies of structure and dynamics in fruit cuticle polyesters

Cutin and suberin are support polymers involved in waterproofing the leaves and fruits of higher plants, regulating the flow of nutrients among various plant organs, and minimizing the deleterious impact of microbial pathogens. Despite the complexity and intractable nature of these plant biopolyesters, their molecular structure and development are amenable to study by suitable solid-state and solution-state NMR techniques. Interactions of tomato cutin with water were examined by solid-state 2H and 13C NMR, showing that water films enhance rapid segmental motions of the acyl chains and are associated with a fivefold increase in surface elasticity upon cutin hydration. The suberization of wounded potato tissues was studied by solid-state 13C NMR, revealing the likely phenylpropanoid structures that permit dense cross-linking of the suberin structure and their proximity to the cell-wall polysaccharides. Finally, two new approaches were developed to elucidate the molecular structures of these biopolymers: partial depolymerization followed by spectroscopic analysis of the soluble oligomers; and swelling of the intact materials followed by magic-angle spinning (MAS) NMR analysis.     

Solid state NMR interaction parameters of oxygens linking titanium and silicon in crystalline cyclic titanodiphenylsiloxanes

17O static and magic angle spinning NMR spectra are reported from three crystalline cyclic titanodiphenylsiloxanes at magnetic fields of 5.6, 14.1, and 17.6 T. These compounds allow the NMR parameters characteristic of Ti-O-Si environments to be determined. It appears from these data that the quadrupole interaction (C(Q)) of such environments is in the range of 3-3.5 MHz and that Si-O-TiO3 sites are less shifted than Si-O-TiO5. The relatively large isotropic chemical range observed suggests that for structurally and atomically disordered titanosilicate-based materials the very highest applied magnetic field may not produce the best 17O solid state NMR spectra. There appears to be a correlation between the 17O shift and Ti-O bondlength.     

Selective NMR excitation in strongly inhomogeneous magnetic fields

The NMR-MOUSE is a unilateral and mobile NMR sensor which operates with highly inhomogeneous magnetic fields. To produce a mobile NMR unit, RF excitation is sought, which can be produced with the most simple equipment, in particular nonlinear, low-power amplifiers, and to observe a free induction decay in strongly inhomogeneous fields, the excitation needs to be selective. The possibility to produce selective excitation by sequences of hard low-power radiofrequency pulses in the strongly inhomogeneous magnetic fields of the NMR-MOUSE is explored. The use of the DANTE sequence for selection of magnetization from parts of the sensitive volume was investigated for longitudinal and transverse magnetization by computer simulations and experiments. The spectra of the recorded FIDs and echo signals are in good agreement with those simulated for the excitation, which verifies the concept of the DANTE excitation. The results obtained are an important step towards a low-power operation of the NMR-MOUSE to improve its mobility.     

Field modulation effects induced by sample spinning: application to high-resolution magic angle spinning NMR

High-resolution magic angle spinning (HRMAS) has become an extremely versatile tool to study heterogeneous systems. HRMAS relies on magic angle spinning of the sample and on pulse sequences originally developed for liquid state NMR. In most cases the outcome of the experiment is conform to what is expected from high-resolution liquid state NMR spectroscopy. However in some instances, experiments run under MAS can produce some very puzzling results. After reviewing the basic hardware which is at the heart of HRMAS spectroscopy, we show that the origin of this behavior lies in the natural time-dependence of some physical quantities imparted by the rotation. We focus in particular on the effects of B1 inhomogeneities on the nutation, the (90 degrees)+x-t-(90 degrees )-x and the MLEV16 experiments. Different models of radiofrequency distribution of B1 fields in a solenoidal coil are derived from simple geometrical considerations. These models are shown by NMR spin dynamics calculations to reproduce the experimental NMR results. They are also consistent with electromagnetic simulations of the B1 field distribution inside a solenoidal coil.     

Diffusion studies in confined nematic liquid crystals by MAS PFG NMR

Pulsed field gradient (PFG) NMR and magic-angle spinning (MAS) NMR have been combined in order to measure the diffusion coefficients of liquid crystals in confined geometry. Combination of MAS NMR with PFG NMR has a higher spectroscopic resolution in comparison with conventional PFG NMR and improves the application of NMR diffusometry to liquid crystals. It is found that the confinement of the liquid crystal 5CB in porous glasses with mean pore diameters of 30 and 200 nm does not notably change its diffusion behavior in comparison with the bulk state.     

新型吡唑并[3,4-d]嘧啶-4-酮类衍生物的结构表征和镇痛活性

本文以2-氰基-3-乙氧基丙烯酸乙酯与3,4-二甲基苯肼为原料,通过多步反应合成了三种新型吡唑并[3,4-d]嘧啶-4-酮类衍生物（A~C）,通过核磁共振（NMR,包括¹H NMR、¹³C NMR）和液相色谱-质谱联用（LC-MS）技术表征确证了其结构,并完整归属了三种化合物的¹H NMR数据．对所合成的化合物1-(3,4-二甲基苯基)-6-甲基-5-[3-(哌啶-1-基)丙氧基]-1,5-二氢-4H-吡唑并[3,4-d]嘧啶-4-酮（A）,通过小鼠脑部质谱成像和福尔马林实验进行了初步的体内镇痛活性评价,我们发现化合物A能透过血脑屏障,并产生显著且剂量依赖的镇痛活性．本研究为以吡唑并[3,4-d]嘧啶-4-酮为骨架的镇痛药物的研发提供了结构和体内活性的基础研究数据．