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长期规律耕作土壤腐殖质的高分辨核磁共振研究 总被引:1,自引:0,他引:1
利用高分辨核磁共振波谱技术对来自长期规律耕作土壤中的腐殖质进行研究,根据所测核磁共振谱粗略探讨了土壤腐殖质的化学基团组成,及不同耕作模式对土壤腐殖质化学基团构成的影响,及部分土壤腐殖质化学基团之间的偶联关系。 相似文献
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近年发展起来的固体高分辨核磁共振(NMR)方法在化学中的应用越来越广。其中一个很重要方面是用于研究难熔高聚物。所谓固体高分辨NMR方法包括:高功率质子去耦、魔角转动样品、交叉极化及多脉冲 相似文献
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高分辨液体核磁共振谱(NMR)的线宽一般<1Hz,它提供了关于天然和合成高分子结构,构象,组成和序列结构等的详尽的知识,因此,对于化学家来说NMR已经成了不可缺少的的结构分析手段。多维高分辨谱技术的发展,人们甚至已经可以获得复杂的蛋白质分子在溶液中的空间立体构象,并为揭示生物大分子的结构和功能的关系起到了重 相似文献
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核磁共振波谱在研究化学结构中占有重要的地位。在高分辨的核磁共振波谱中,磁性核之间的自旋-自旋偶合作用往往会使谱线复杂化。一方面,可以利用自旋-自旋偶合作用来确定一些化合物的结构;另一方面,由于谱线的复杂化,使得分析复杂化合物的核磁共振谱发生困难。借助于自旋去偶技术可以解决核磁共振中很多疑难问题,使核磁共振的研究工作更深入一步。因此,它是核磁共振波谱学发展中的一门重要的研究技术。必须区别两种不同的自旋-自旋偶合情况,即同一类核之间的自旋-自旋偶合(例如质子之间的偶合)和不同类核之间的偶合(例如质子同 相似文献
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利用高分辨核磁共振谱仪研究了环氧乙烷-环氧丙烷均聚物和无规共聚物的核磁共振主链碳谱。在对其链结构进行有效归属的基础上,讨论了不同配比聚合物的僚共振主链碳谱特点及其可能的单元链节排列顺序。 相似文献
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高硅FAU沸石与甲胺吸附物的相互作用 总被引:1,自引:0,他引:1
合成高硅沸石中所用的模板剂胺类分子与沸石骨架 Si—O基团间的相互作用机理尚不清楚 .迄今为止 ,沸石与吸附胺之间的相互作用的研究还只限于测定沸石酸性质 [1,2 ]、表面羟基活性位或了解模板分子在沸石骨架中的位置和状态 [3,4 ] .甲胺、乙胺在骨架完美的高硅 FAU(Y型 )沸石上的亲和性指数 AT 值 ,即被吸附有机物脱附峰温与该有机物的沸点之差分别高达 1 60与 1 5 0℃[5] .而在高硅 MFI(Silicalite-1 )沸石上为 1 60与 1 2 7℃ [6 ] .与大多数有机物不同 ,被吸附的胺类脱附时的吸热效应十分明显 .上述现象表明胺与高硅沸石骨架 O2 -… 相似文献
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Ccile Dubois Isaline Herrada Philippe Barthe Christian Roumestand 《Molecules (Basel, Switzerland)》2020,25(23)
High-hydrostatic pressure is an alternative perturbation method that can be used to destabilize globular proteins. Generally perfectly reversible, pressure exerts local effects on regions or domains of a protein containing internal voids, contrary to heat or chemical denaturant that destabilize protein structures uniformly. When combined with NMR spectroscopy, high pressure (HP) allows one to monitor at a residue-level resolution the structural transitions occurring upon unfolding and to determine the kinetic properties of the process. The use of HP-NMR has long been hampered by technical difficulties. Owing to the recent development of commercially available high-pressure sample cells, HP-NMR experiments can now be routinely performed. This review summarizes recent advances of HP-NMR techniques for the characterization at a quasi-atomic resolution of the protein folding energy landscape. 相似文献
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Alfred Deege Heribert Husmann Eduard Hübinger Frank Kobor Gerhard Schomburg 《Journal of separation science》1993,16(10):587-593
Complex mixtures of partially alkylated cyclodextrins can be analyzed by both HPLC and high temperature capillary GC. Because of the limited efficiency of LC, suitable analytical and preparative separations can be achieved only with systems of carefully optimized selectivity. Using LC it has been possible to isolate and purify single cyclodextrin species from very complex mixtures of components which contain unreacted hydroxyl groups in addition to the alkoxy groups. Analysis of the reaction mixtures and of fractions taken from LC separations can be performed with advantage by high resolution capillary GC at high temperatures between 300 and 400 °C. The thermal stability of partially alkylated cyclodextrins in high temperature GC is considerably increased by trimethylsilylation of the free hydroxyl groups. Fast atom bombardment mass spectrometry and proton NMR were used to identify species isolated from the preparative LC separations. 相似文献
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Li‐Hong Tseng Ulrich Braumann Markus Godejohann Shoei‐Sheng Lee Klaus Albert 《中国化学会会志》2000,47(6):1231-1236
The potential of coupling HPLC separation methodology to on‐line high resolution nuclear magnetic resonance (NMR) spectroscopy has been demonstrated with a mixture of nine aporphine alkaloids. A loop storage procedure after separation has facilitated the identification of closely eluted peaks (α = k2/k1 = 1.01 and Δv = 0.37 min = 367 μL). These were collected off‐line and identified by a 1D 1H NMR spectrum. For this purpose an automated procedure has been implemented which includes the use of shaped pulses, multiple solvents suppression and 13C satellite suppression of acetonitrile. 相似文献
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Palle J. Pedersen 《Tetrahedron letters》2008,49(43):6220-6223
Regio- and stereoselective hydrosilylation of terminal alkynes on solid support using diisopropyl hydrosilanes yielding β-(E)-vinyl silanes with excellent selectivity is reported. The hydrosilylation is catalyzed by Pt(DVDS)/P(iBuNCH2CH2)3N (DVDS = 1,3-divinyl-1,1,3,3-tetramethyl-disiloxane), in which the bulky proazaphosphatrane ligand plays a key role for the selectivity. The immobilized products are characterized with gel phase13C NMR and 1H high resolution magic angle spinning NMR. 相似文献
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Junko Iida Takehiro Takeda Takumi Takasuga John Moncur Phil Ireland Barry Wright 《Journal of separation science》1991,14(2):103-109
A hybrid mass spectrometer with an EBQQ configuration was used to investigate two approaches to trace dioxin analysis: high resolution gas chromatography – high resolution mass spectrometry (HRGC-HRMS) and high resolution gas chromatography – mass spectrometry – mass spectrometry (HRGC-MS-MS). It is shown that selected ion monitoring (SIM) HRGC-HRMS exhibits better selectivity for dioxins separated on a cyanopropyl column than is otherwise obtained under medium resolution mass spectrometry (3,000 resolution), while optimization of conditions for HRGC-MS-MS allowed the observation of 350 femtograms of the highly toxic 2,3,7,8-TCDF at a S/N ratio of 5:1. Both methods were applied to environmental samples with good results. 相似文献
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通过高低工作频率的高分辩率核磁共振谱仪(型号分别为GX-400和FX-90Q)对含有不同微量异种结构单元的聚乙烯样品作了^13C谱测量和比较分析;结果表明^13C谱在较高磁场频率(100.4MHz)条件下可检测灵敏度达到0.5个支化点/10000个碳原子(0.5/10000C);而较低磁场频率(22.5MHz)只达到1个支化点/1000个碳原子(1/1000C)以上;综合分析所得结果,指出在用电磁体系列(谱仪频率一般为90MHz或100MHz)核磁共振谱仪检测高分子量物质时,应注意有遗漏1/1000C以下浓度结构的可能性;分析了^13C谱可检测灵敏度与磁场强度等因素的关系,得到了可检测灵敏度S/N与磁场强度(H0)间比较适合的关系式。 相似文献
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Partial‐Homogeneity‐Based Two‐Dimensional High‐Resolution Nuclear Magnetic Resonance Spectroscopy under Inhomogeneous Magnetic Fields 下载免费PDF全文
Wenqi Qiu Dr. Zhiliang Wei Nan Ding Dr. Yu Yang Qimiao Ye Prof. Yulan Lin Prof. Zhong Chen 《Chemphyschem》2016,17(10):1493-1499
High‐resolution multidimensional nuclear magnetic resonance (NMR) spectroscopy serves as an irreplaceable and versatile tool in various chemical investigations. In this study, a method based on the concept of partial homogeneity is developed to offer two‐dimensional (2D) high‐resolution NMR spectra under inhomogeneous fields. Oscillating gradients are exerted to encode the high‐resolution information, and a field‐inhomogeneity correction algorithm based on pattern recognition is designed to recover high‐resolution spectra. Under fields where inhomogeneity primarily distributes along a single orientation, the proposed method will improve performances of 2D NMR spectroscopy without increasing the experimental duration or significant loss in sensitivity, and thus may open important perspectives for studies of inhomogeneous chemical systems. 相似文献