Fourier transform NMR two-dimensional

Usually the 2D NMR spectnun is either for the spin-spin interaction (COSY) or for the NOE (NOESY). Spectra of 2D NMR are plotted on two frequency axes, which show a crosspeak at the frequencies corresponding to each pair of nuclei that interact. The magnitude of the interaction effect is represented by the intensity of the crosspeak. It is shown by the number of contours (like a contour map) at the point of interaction the more contours, the higher the peak corresponding to the interaction. The diagonal represents ID spectrum of the contour line of peaks, which also plot along both axes. 

Amino acids have characteristic resonances resulting from the Ca-proton and the protons on the side chains. 

The PMR spectra of side chains can be divided approximately into four regions  

Side chain (specific) Guanidine N Imidazole Indole CH Indole NH 

The characteristic chemical shifts for proton (shown in bold) resonances with respect to a reference compound, R—Si(CH3)3 (5 = Oppm) are illustrated. 

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Bax A, Freeman R, Morris G 1981 Correlation of proton chemical shifts by two-dimensional Fourier transform NMR. J Magn Res 42 164-168... 

Covariance NMR spectroscopy allows acquisition of spin-spin correlation in a more efficient way compared to the traditional two-dimensional Fourier-transformation NMR spectroscopy, leading to reduction in the experimental time or increase in the sensitivity of the spectrum obtainable within a given experimental time. This chapter summarizes recent works on covariance NMR, focusing on its applications to solid-state NMR spectroscopy. In addition to a brief survey of the covariance spectroscopy, an open question of whether "inner-product" spectroscopy is more natural is posted. The usefulness of covariance NMR spectroscopy is presented by exploring its applications to solid-state systems of chemical/biological interest. A number of recent reports to further improve its efficiency or to extend the scope of its applicability are reviewed. 

The laser heating technique can be applied to perform temperature jumps by irradiating short laser pulses at the sample container. Ernst et al. (54) used such a temperature jump protocol to perform stop-and-go experiments. After the start of the laser pulse, the temperature inside the sample volume is raised to the reaction temperature, the conversion of the adsorbed reactants proceeds, and the H MAS NMR measurement is performed. After the laser pulse is stopped, the temperature inside the sample volume decreases to ambient temperature, and the C MAS NMR measurement is made. Subsequently, the next laser pulse is started and, in this way, the reaction is recorded as a function of the reaction time. By use of the free-induction decay and the reaction time as time domains and respectively, a two-dimensional Fourier transformation leads to a two-dimensional spectrum, which contains the NMR spectrum in the Ej-dimension and the reaction rate information in the Ts-dimension (54,55). 

It is interesting to note that several of the concepts for improving NMR technology, as listed by Levy and Craik, in 1988, already have been partially or fully achieved (1) two-dimensional Fourier transform (FT NMR) (2) high-resolution NMR in solids (3) new types of pulse sequences (4) chemically induced dynamic nuclear polarization (5) multiple quantum NMR and (6) NMR imaging (MRI). 

It is important to realize that double Fourier transformation is not an essential part of two-dimensional NMR spectroscopy. This was made clear by Ernst in his early article (26) and when the spin system is simple there may be no particular advantage in using it. This approach was adopted in studies of C-enriched methyl formate in which various selective H and/or pulses were applied to individual transitions and it was found possible to deduce an accurate value for v( C) and draw conclusions about relaxation behaviour. (164-166) Detailed analysis (167) also shows that the sensitivity of two-dimensional Fourier transform spectroscopy can be as good as half that achieved in ordinary one-dimensional experiments. In this connection we should note that the time-saving gain of Fourier transformation... 

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 common to almost all of the Raman spectroscopies. Three-colour 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 transform representations analogous to 2D NMR [25]. 

R. Freeman and G. A. Morris, "Two-dimensional Fourier transformation in NMR," Bull. Magn. Resonance 1, 5-26... 

Kazimierczuk K, Kozminski W, Zhukov I (2006) Two-dimensional Fourier transform of arbitrarily sampled NMR data sets. J Magn Reson 179 323-328... 

In the in situ approach, the growth of the particles from the surface of a PDMS sample can be followed by NMR (figure 9.3) utilizing and Si magic-angle spinning, with two-dimensional Fourier transform spin-echo techniques. The spin-spin (T ) relaxation time of the protons in... 

Tbrpstra D 1979 Two-dimensional Fourier transform carbon-13 NMR. In Levy G C (ed) Topics in carbon-13 NMR spectroscopy, vol 3. John Wiley New York, 62-78... 

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