Two-dimensional NMR spectroscopy

Two significant developments in NMR spectroscopy are the use of Fourier transform techniques, and the development of two-dimensional (2D) NMR spectroscopy. Two-dimensional spectra are obtained using a sequence of rf pulses that includes a variable delay or delays. A set of FIDs is acquired and stored. The variable delay is incremented by a small amount of time and a new set of FIDs are obtained and stored, and so on. At the end, the resulting matrix of FID data is Fourier transformed twice once with respect to the acquisition time (as in normal FT-NMR) and second with respect to the time of the variable delay in the pulse sequence. The resulting data represent a surface and are presented as a contour plot of that surface. 

The drying of porous catalyst support pellets has been followed using NMR imaging.MRI has been used to analyse water movement in water based ceramic pastes.NMR spectroscopy has been used to study suspensions of drilling mud. The effect of particle size on the floculation behaviour of ultrafine clays in salt solution has been studied using NMR spectroscopy. Two-dimensional NMR spectroscopy has been used to study surface water dynamics in hydrated silica spheres.Aqueous suspensions of highly dispersed... 

See also Diffusion Studied Using NMR Spectroscopy NMR Pulse Sequences Product Operator Formalism in NMR Solvent Suppression Methods in NMR Spectroscopy Two-Dimensional NMR, Methods. 

See also Cells Studied By NMR In vivo NMR, Applications, NMR Pulse Sequences Nuclear Over-hauser Effect Nucleic Acids Studied Using NMR Nucleic Acids and Nucleotides Studied Using Mass Spectrometry Parameters in NMR Spectroscopy, Theory of Perfused Organs Studied Using NMR Spectroscopy Proteins Studied Using NMR Spectroscopy Two-Dimensional NMR Methods. 

See also Biofluids Studied By NMR Chromatogra-phy-NMR, Applications Diffusion Studied Using NMR Spectroscopy Magnetic Fieid Gradients in High Resolution NMR NMR Data Processing NMR Principles NMR Pulse Sequences NMR Relaxation Rates NMR Spectrometers Product Operator Formalism in NMR Proteins Studied Using NMR Spectroscopy Two-Dimensional NMR, Methods. 

The salts 266-268 fonn solid dimers solvated with THF. The association into dimers is preserved in solution. They can be characterized in solution by H, Li and NMR spectroscopies and in the solid state by Li MAS NMR, C CP/MAS NMR and two-dimensional Li MAS NMR spectroscopies and XRD crystallography . 

Brenna, S., Posset, T, Furrer, J. et al, N NMR and two-dimensional suspension iR and i C HRMAS NMR spectroscopy of ionic liquids immobilized on silica,... 

We have characterized (8e-i) this intermediate using solid-state 13C CP/MAS NMR, 2H NMR, and two dimensional (2D). /-resolved 3C NMR spectroscopy in the course of dehydration of isobutyl alcohol and /er/-butyl alcohol in HZSM-... 

We have investigated peptides whose structures were known beforehand from NMR or x-ray spectroscopy and related these structures to 2D-IR spectroscopy. Ultimately, one would like to deduce the structure of an unknown sample from a 2D-IR spectrum. In the case of 2D NMR spectroscopy, two different phenomena are actually needed to determine peptide structures. Essentially, correlation spectroscopy (COSY) is utilized in a first step to assign protons that are adjacent in the chemical structure of the peptide so that J coupling gives rise to cross peaks in these 2D spectra. However, this through-bond effect cannot be directly related to the three-dimensional structure of the sample, since that would require quantum chemistry calculations, which presently cannot be performed with sufficient accuracy. The nuclear Overhauser effect (NOE), which is an incoherent population transfer process and has a simple distance dependence, is used as an additional piece of information in order to measure the distance in... 

Although solution-state NMR has revealed much regarding the chemical structural composition of humic substances and dissolved organic matter (5), the development of more sophisticated software, pulse sequences, probes in recent years have not been exploited much in the field of soil science. Most of the novel applications have strictly relied on conventional one-dimensional spectroscopy. Two-dimensional NMR methods have become the mainstay of the chemical research field, especially for the structural elucidation of complex soluble biopolymers. The complexity of humic substances along with other inherent physical properties such as limited solubility and the presence of paramagnetics... 

Nuclear Magnetic Resonance Spectroscopy. Like IR spectroscopy, NMR spectroscopy requires little sample preparation, and provides extremely detailed information on the composition of many resins. The only limitation is that the sample must be soluble in a deuterated solvent (e.g., deuterated chloroform, tetrahydro-furan, dimethylformamide). Commercial pulse Fourier transform NMR spectrometers with superconducting magnets (field strength 4-14 Tesla) allow routine measurement of high-resolution H- and C-NMR spectra. Two-dimensional NMR techniques and other multipulse techniques (e.g., distortionless enhancement of polarization transfer, DEPT) can also be used [10.16]. These methods are employed to analyze complicated structures. C-NMR spectroscopy is particularly suitable for the qualitative analysis of individual resins in binders, quantiative evaluations are more readily obtained by H-NMR spectroscopy. Comprehensive information on NMR measurements and the assignment of the resonance lines are given in the literature, e.g., for branched polyesters [10.17], alkyd resins [10.18], polyacrylates [10.19], polyurethane elastomers [10.20], fatty acids [10.21], cycloaliphatic diisocyanates [10.22], and epoxy resins [10.23]. 

Two-dimensional Fourier Spectroscopy. Two-dimensional (2D) spectroscopy is a general concept that can be applied to different brimches of spectroscopy which make it possible to acquire more detailed information about the molecular system under investigation. Since the first proposal in the 1971 (35) and the first experimental realization in the 1974 (36-38) a large number of 2D NMR methods have been invented and applied (1) to solve structural and dynamical problems in physics, chemistry, biology, and medicine. 

A comprehensive study has been made to probe the spatial proximities among different acid sites in modified dealuminated H-Y zeolites by using a variety of different solid-state NMR techniques, including multinuclear MAS NMR and two-dimensional H DQ MAS NMR spectroscopy. ... 

A. Wokaun and R.R. Ernst, Selective detection of multiple quantum transitions in NMR by two-dimensional spectroscopy, Phys. Lett. 52,407 (1977). 

This application exemplifies how theoretical methods were used to extend the MC-SYM database. The symmetrical tandem of G U mismatches is a motif that was identified in ribosomal RNAs. The secondary structure and a selected spanning tree of the motif are shown in Figure 11. The list of possible G U base pairing patterns that involve two hydrogen bonds are shown in Table 5. Two of these patterns, XXVII (reverse Wobble) and XXVIII (Wobble), were described in Saenger and both were found in RNA and DNA X-ray crystallography and NMR spectroscopy three-dimensional structures. 

See also Biofluids Studied By NMR NMR, Methods NMR, Parameter Survey Carbohydrates Studied By NMR Cells Studied By NMR Drug Metabolism Studied Using NMR Spectroscopy NMR Applications, Solution State In Vivo NMR, Applications, Other Nuclei Nucleic Acids Studied Using NMR Perfused Organs Studied Using NMR Spectroscopy P NMR Proteins Studied Using NMR Spectroscopy Structural Chemistry Using NMR Spectroscopy, Pharmaceuticals Tritium NMR, Applications Two-Dimensional NMR, Methods. 

Time-resolved spectroscopy has become an important field from x-rays to the far-IR. Both IR and Raman spectroscopies have been adapted to time-resolved studies. There have been a large number of studies using time-resolved Raman [39], time-resolved resonance Raman [7] and higher order two-dimensional Raman spectroscopy (which can provide coupling infonuation analogous to two-dimensional NMR studies) [40]. Time-resolved IR has probed neutrals and ions in solution [41, 42], gas phase kmetics [42] and vibrational dynamics of molecules chemisorbed and physisorbed to surfaces [44]- Since vibrational frequencies are very sensitive to the chemical enviromnent, pump-probe studies with IR probe pulses allow stmctiiral changes to... 

The general task is to trace the evolution of the third order polarization of the material created by each of the above 12 Raman field operators. For brevity, we choose to select only the subset of eight that is based on two colours only—a situation that is connnon to almost all of the Raman spectroscopies. Tliree-coloiir Raman studies are rather rare, but are most interesting, as demonstrated at both third and fifth order by the work in Wright s laboratory [21, 22, 23 and 24]- That work anticipates variations that include infrared resonances and the birth of doubly resonant vibrational spectroscopy (DOVE) and its two-dimensional Fourier transfomi representations analogous to 2D NMR [25]. 

Aue W P, Kharan J and Ernst R R 1976 Homonuclear broadband decoupling and two-dimensional J-resolved NMR spectroscopy J. Chem. Phys. 64 4226-7... 

Barbate G, Ikura M, Kay L E, Pastor R W and Bax A 1992 Backbone dynamics of calmodulin studied by N relaxation using inverse detected two-dimensional NMR spectroscopy the central helix is flexible S/oefrem/sf/ y 31 5269-78... 

Jeener J, Meier B H, Bachmann P and Ernst R R 1979 Investigation of exchange processes by two-dimensional NMR spectroscopy J. Chem. Rhys. 71 4546-53... 

A good introductory treatment of the density operator formalism and two-dimensional NMR spectroscopy, nice presentation of Redfield relaxation theory. 

The standard monograph for those seeking an introduction to EPR spectroscopy. Frieboiin H 1993 Basic One- and Two-Dimensional NMR Spectroscopy (New York VCH) A basic introduction to NMR spectrai anaiysis. 

Two-dimensional nmr spectroscopy has led to a much better understanding of biopolymers and their function (151). This technique has been apphed to polyacrylamide for absolute assignments of proton and carbon spectra at the tetrad level (152). 

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