Two-dimensional Experiments (two-dimensional + experiment)

Distribution by Scientific Domains

Selected Abstracts

17O NMR in room temperature phase of La2Mo2O9 fast oxide ionic conductor

Joel Emery
Abstract A room temperature 17O NMR study of La2Mo2O9, a fast oxide ionic conductor exhibiting a phase transition at 580 C between a low-temperature ,-phase and a high-temperature ,-phase, is presented. Four partly overlapping quasi-continuous distributions of oxygen sites are evidenced from 1D magic angle spinning (MAS) and 2D triple quantum MAS NMR experiments. They can be correlated with the three oxygen sites O1, O2 and O3 of the high-temperature crystal structure. The low-temperature phase is characterized by two distributed sites of type O1, which proves that the symmetry is lower than in the cubic high-temperature phase. Two-dimensional experiments show that there is no dynamic exchange process, on the NMR time-scale, between the different oxygen sites at room temperature, which agrees well with conductivity results. Copyright 2005 John Wiley & Sons, Ltd. [source]

Complete 1H and 13C NMR spectral assignment of ,- and ,-adenosine, 2,-deoxyadenosine and their acetate derivatives

P. Ciuffreda
Abstract 1H and 13C NMR chemical shifts of ,- and ,-anomers of adenosine, 2,-deoxyadenosine and their acetate derivatives were completely and definitely assigned using the concerted application of one- and two-dimensional experiments (gCOSY, gNOESY, gHSQC and gHMBC). The influence of the stereochemistry of the purine base on the NMR data of the hydrogen and carbon atoms of the furanose moiety was estimated. Copyright 2007 John Wiley & Sons, Ltd. [source]

1H and 13C chemical shifts for some tetrasubstituted 2,5-diaryl di- and tetrahydrofuran derivatives

S. Martinet
Abstract The 1H and 13C NMR chemical shifts of four 2,5-diaryltetrahydrofuran derivatives and their dihydro precursors were assigned completely with certainty using a concerted application of one- and two-dimensional experiments (DEPT, gs-COSY, gs-HMQC and gs-HMBC) Copyright 2006 John Wiley & Sons, Ltd. [source]

High resolution in heteronuclear 1H,13C NMR experiments by optimizing spectral aliasing with one-dimensional carbon data

Damien Jeannerat
Abstract In the chemistry literature it is common to provide NMR data on both proton and carbon spectra based on one-dimensional experiments, but often only proton spectra are assigned. The absence of a complete attribution of the carbons is in good part due to the difficulty in reaching the necessary resolution in the carbon dimension of two-dimensional experiments. It has already been shown that high-resolution heteronuclear spectra can be acquired within nearly the same acquisition time using a violation of the Nyquist condition. For a spectral width reduction by a given factor k, the resolution increases by the same factor as long as it is not limited by relaxation. The price to pay for such an improvement is a k -fold ambiguity in the chemical shift of the signal along the folded or aliased dimension. The computer algorithm presented in this paper takes advantage of the peak list stemming from one-dimensional spectra in order to calculate spectral widths for which the ambiguities in the aliased dimension of heteronuclear experiments are eliminated or at least minimized. The resolution improvement factor is only limited by the natural lineshape and reaches a typical value higher than 100. The program may be set to run automatically on spectrometers equipped with automatic sample changers. Applications to short-range HSQC experiments and long-range HMBC spectra of steroids, carbohydrates, a peptide and a mixture of isomers are shown as examples. Copyright 2002 John Wiley & Sons, Ltd. [source]

Lipopolysaccharides from Serratia marcescens Possess One or Two 4-Amino-4-deoxy- L -arabinopyranose 1-Phosphate Residues in the Lipid A and D - glycero - D - talo -Oct-2-ulopyranosonic Acid in the Inner Core Region,

Evgeny Vinogradov Dr.
Abstract The carbohydrate backbones of the core-lipid A region were characterized from the lipopolysaccharides (LPSs) of Serratia marcescens strains 111R (a rough mutant strain of serotype O29) and IFO 3735 (a smooth strain not serologically characterized but possessing the O-chain structure of serotype O19). The LPSs were degraded either by mild hydrazinolysis (de- O -acylation) and hot 4,M KOH (de- N -acylation), or by hydrolysis in 2,% aqueous acetic acid, or by deamination. Oligosaccharide phosphates were isolated by high-performance anion-exchange chromatography. Through the use of compositional analysis, electrospray ionization Fourier transform mass spectrometry, and 1H and 13C NMR spectroscopy applying various one- and two-dimensional experiments, we identified the structures of the carbohydrate backbones that contained D - glycero - D - talo -oct-2-ulopyranosonic acid and 4-amino-4-deoxy- L -arabinose 1-phosphate residues. We also identified some truncated structures for both strains. All sugars were D -configured pyranoses and ,-linked, except where stated otherwise. [source]