Nuclear magnetic resonance relaxation data analysis

Raw nuclear magnetic resonance (NMR) data consist of damped oscillations produced by choruses of nuclei with different resonant frequencies. Analysis consists of determining those resonances, and is traditionally done with the discrete Fourier transform. However, the time variation of the amplitudes introduces errors, and the weakness of the resonances forces many repetitions to get adequate height in the peaks. The continuous wavelet transform spectral estimation algorithm has recently been used instead, to avoid both these problems. Without the need for repetitions, it is possible to analyze chemical reactions at time steps comparable with nuclear spin relaxation times. 

Several spectroscopic techniques, namely, Ultraviolet-Visible Spectroscopy (UV-Vis), Infrared (IR), Nuclear Magnetic Resonance (NMR), etc., have been used for understanding the mechanism of solvent-extraction processes and identification of extracted species. Berthon et al. reviewed the use of NMR techniques in solvent-extraction studies for monoamides, malonamides, picolinamides, and TBP (116, 117). NMR spectroscopy was used as a tool to identify the structural parameters that control selectivity and efficiency of extraction of metal ions. 13C NMR relaxation-time data were used to determine the distances between the carbon atoms of the monoamide ligands and the actinides centers. The II, 2H, and 13C NMR spectra analysis of the solvent organic phases indicated malonamide dimer formation at low concentrations. However, at higher ligand concentrations, micelle formation was observed. NMR studies were also used to understand nitric acid extraction mechanisms. Before obtaining conformational information from 13C relaxation times, the stoichiometries of the... 

In a paper that appeared in 1979, R.P.J. Merks and R. DeBeer pointed out that the sinusoidal dependence of the stimulated echo ESEEM experiment on x and T (equation 8), presented the opportunity to collect ESEEM data in both time dimensions and then apply a two-dimensional EFT to derive two important benefits. The first benefit was that suppression-free spectra should be obtained along the zero-frequency axis for each dimension while the second benefit would be the appearance of cross-peaks at (tUo, cofs) and (tw, co ) that would allow one to identify peaks that belonged to the same hyperfine interaction. This ESEEM version of the NMR COSY experiment (see Nuclear Magnetic Resonance (NMR) Spectroscopy of Metallobiomolecules) would prove invaluable for ESEEM analysis of complex spin systems. However, the disparity in spin relaxation times in the x and T time dimensions precluded the general application of this method. 

Nuclear Magnetic Resonance Spectroscopy.—As noted above, conformational analysis of bicyclo[3.3.1]nonanes is still a topic of considerable interest. A variable-temperature n.m.r. analysis now provides the first case in which the boat-chair-chair-boat equilibrium is directly observed in the amines (17) and (18). In a related case, re-examination of the acetal (19) suggests that the preferred conformation involves a chair carbocyclic ring and a boat heterocyclic ring. This conclusion was made by n.m.r. analysis, using lanthanide shift reagents, by a study of nuclear Overhauser effects, and by measurement of relaxation times of protons. Details have been reported for other 3-azabicyclo[3.3.1]nonanes, and the non-additivity of substituent effects on chemical shifts in 9-thiabicyclo[3.3.1]non-2-enes has been analysed. Both and n.m.r. data have been reported for a series of 9-borabicyclo[3.3.1]non-anes and their pyridine complexes. 

Abstract Nuclear Magnetic Resonance (NMR) relaxation is a powerful technique that provides information about internal dynamics associated with configurational energetics in proteins, as well as site-specific information involved in conformational equilibria. In particular, N relaxation is a useful probe to characterize overall and internal backbone dynamics of proteins because the relaxation mainly reflects reorientational motion of the N-H bond vector. Over the past 20 years, experiments and protocols for analysis of N Ri, R2, and the heteronuclear N- NOE data have been well established. The development of these methods... 

Among the several experimental techniques for studying colloid and sol-gel chemistry, perhaps the most powerful one is nuclear magnetic resonance (NMR) spectroscopy. NMR allows investigation of these systems by a combination of structural information, obtained through lineshape analysis and chemical shift data, and indirect information from dynamic measurements of spin relaxation and diffusion. 

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