Nuclear magnetic resonance probe specifications

While XAS techniques focus on direct characterizations of the host electrode structure, nuclear magnetic resonance (NMR) spectroscopy is used to probe local chemical environments via the interactions of insertion cations that are NMR-active nuclei, for example lithium-6 or -7, within the insertion electrode. As with XAS, NMR techniques are element specific (and nuclear specific) and do not require any long-range structural order in the host material for analysis. Solid-state NMR methods are now routinely employed to characterize the various chemical components of Li ion batteries metal oxide cathodes, Li ion-conducting electrolytes, and carbonaceous anodes.Coupled to controlled electrochemical in-sertion/deinsertion of the NMR-active cations, the... 

Spectroscopic techniques, such as ultra-violet (9), Infrared (25), Nuclear Magnetic Resonance (24), and Fluorescence spectroscopies (5-8), constitute direct probes of specific events occurring at the molecular scale. When a quantitative interpretation is possible, spectroscopy provides very detailed microscopic information. Unfortunately however, the interpretation of spectra in terms of molecular events is often complex. Yet another approach that probes events at the molecular scale involves the use of tracers, such as chromophores (1-225). Again, the complexity of the tracer imposes limitations on the extent to which the data can be interpreted quantitatively. 

Solvent effects on nuclear magnetic resonance (NMR) spectra have been studied extensively, and they are described mainly in terms of the observed chemical shifts, 8, corrected for the solvent bulk magnetic susceptibility (Table 3.5). The shifts depend on the nucleus studied and the compound of which it is a constituent, and some nuclei/compounds show particularly large shifts. These can then be employed as probes for certain properties of the solvents. Examples are the chemical shifts of 31P in triethylphosphine oxide, the 13C shifts in the 2-or 3-positions, relative to the 4-position in pyridine N-oxide, and the 13C shifts in N-dimethyl or N-diethyl-benzamide, for the carbonyl carbon relative to those in positions 2 (or 6), 3 (or 5) and 4 in the aromatic ring (Chapter 4) (Marcus 1993). These shifts are particularly sensitive to the hydrogen bond donation abilities a (Lewis acidity) of the solvents. In all cases there is, again, a trade off between non-specific dipole-dipole and dipole-induced dipole effects and those ascribable to specific electron pair donation of the solvent to the solute or vice versa to form solvates. 

In a broad sense, an acid site can be defined as a site on which a base is chemically adsorbed. Conversely, a basic site is a site on which an acid is chemically adsorbed. Specifically, a Bronsted acid site has a propensity to give a proton, and a Bronsted base has the tendency to receive a proton. Additionally, a Lewis acid site is capable of taking an electron pair and a Lewis basic site is capable of providing an electron pair. These processes can be studied by following the color modifications of indicators, and by using infrared (IR) and nuclear magnetic resonance (NMR) spectroscopies, and calorimetry of adsorption of the probe molecules (see Chapter 4). 

Infrared spectroscopy is an important technique for studying acidity. Acidic OH groups can be studied directly. Probe molecules such as pyridine may be used to study both Bronsted and Lewis acidity since two forms of adsorbed probes are easily distinguished by their infrared spectra. Quantitative infrared spectroscopy may be performed by measuring the spectrum of acidic OH or probes adsorbed on thin, self-supporting wafers of the acidic solid. Other spectroscopic methods which may provide information in specific cases include Fourier Transform Raman spectroscopy, electron spin resonance spectroscopy, ultraviolet spectroscopy, and nuclear magnetic resonance spectroscopy. 

Nuclear magnetic resonance (NMR) is one of the most important site-specific and sensitive probes for electronic environments and hence for molecular... 

Endogenous ligands for the cannabinoid receptor have not yet been identified. Arachidonylethanolamide, a new arachidonic acid derivative named anandamide, was isolated from porcine brain. Its structure was determined by mass spectrometry and nuclear magnetic resonance spectroscopy and was confirmed by synthesis. It inhibits the specific binding of a labelled cannabinoid probe to synaptosomal membranes in a manner typical of competitive ligands, and produces a concentration-dependent inhibition of the electrically-evoked twitch response of the mouse vas deferens, a characteristic effect of psychotropic cannabinoids. Similar compounds were synthesized and their pharmacological properties were investigated. 

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... 

Haimovich J, Schechter I, Sela M (1969) Combining sites of IgG and IgM antibodies of poly-D-alanyl specificity. Eur J Biochem 7 537-543 Hamaoka T, Katz DH, Benacerraf B (1972) Radioresistance of carrierspecific helper thymus-derived lymphocytes in mice. Proc Natl Acad Sci USA 69 3453-3458 Hauglund RP, Stryer L, Stengle TR, Baldeschweiler JD (1967) Nuclear magnetic resonance studies of antibody-hapten interactions using a chloride ion probe. Biochemistry 6 498-502... 

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