Exchange nuclear magnetic resonance

The exchange NMR method is another class of experiments, described by Judeinstein et that can be used to study molecular motions which has the advantage of being much more model independent. The principles of these experiments rely on the orientation dependence of the NMR interactions for solid materials. The chemical shift in a solid is described by a 3x3 tensor, thus the NMR frequency of a nucleus (for example) in a specific molecular site depends on the orientation of the molecule. This is known as chemical shift anisotropy (CSA) and, for amorphous or polycrystalline samples, the NMR spectrum defined by such interaction has a characteristic shape known as NMR powder patterns (Fig. 7.16a) when all orientations are present in the sample. The basic idea of an exchange 

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Mueller, G.A., Smith, A.M., Chapman, M.D., Rule, G.S., and Benjamin, D.C. 2001. Hydrogen exchange nuclear magnetic resonance spectroscopy mapping of antibody epitopes on the house dust mite allergen Derp 2. J Biol Chem 276(12) 9359-9365. 

While the value suggested by Johnson and McCants for the conformational free energy difference in Scheme 3.2 was a substantial AG°9q.c = +1.3 kcalmol [13], a more precise determination was carried out by Lambert and Keske [14], who examined the slow-exchange nuclear magnetic resonance (NMR) spectra of the unsubstituted tetradeuteriated thiane-l-oxide (2) at -90°C (Scheme 3.3). 

H. Geen, G. Bodenhausen, Pure absorption-mode chemical exchange nuclear magnetic resonance spectroscopy with suppression of spinning sidebands in a slowly rotating solid, J. Chem. Phys. 97 (1992) 2928. 

Woessner D E 1996 Relaxation effects of chemical exchange Encyclopedia of Nuclear Magnetic Resonance ed D M Grant and R K Harris (Chichester Wiley) pp 4018-28... 

Di Bari L, Kowalewski J and Bodenhausen G 1990 Magnetization transfer modes in scalar-coupled spin systems investigated by selective 2-dimensional nuclear magnetic resonance exchange experiments J. Chem. Rhys. 93 7698-705... 

Reeves L W and Shaw K N 1970 Nuclear magnetic resonance studies of multi-site chemical exchange. I. Matrix formulation of the Bloch equations Can. J. Chem. 48 3641-53... 

Binsch G 1969 A unified theory of exchange effects on nuclear magnetic resonance lineshapes J. Am. Chem. Soc. 91 1304-9... 

Alexander S 1962 Exchange of interacting nuclear spin in nuclear magnetic resonance. I. Intramolecular exchange J. Chem. Phys. 37 967-74... 

Physical Chemical Characterization. Thiamine, its derivatives, and its degradation products have been fully characterized by spectroscopic methods (9,10). The ultraviolet spectmm of thiamine shows pH-dependent maxima (11). H, and nuclear magnetic resonance spectra show protonation occurs at the 1-nitrogen, and not the 4-amino position (12—14). The H spectmm in D2O shows no resonance for the thiazole 2-hydrogen, as this is acidic and readily exchanged via formation of the thiazole yUd (13) an important intermediate in the biochemical functions of thiamine. Recent work has revised the piC values for the two ionization reactions to 4.8 and 18 respectively (9,10,15). The mass spectmm of thiamine hydrochloride shows no molecular ion under standard electron impact ionization conditions, but fast atom bombardment and chemical ionization allow observation of both an intense peak for the patent cation and its major fragmentation ion, the pyrimidinylmethyl cation (16). 

An X-ray crystallographic study of 2-hydroxy-4,6-dimethylpyrimi-dine led to no conclusions regarding its structure. Because of the rapid exchange of the NH protons of pyrimidin-2-one both in dimethyl sulfoxide and in water, nuclear magnetic resonance spectroscopy does not afford positive evidence for either the oxo or the hydroxy formulation. The statement that 4,6-dimethylpyrimidin-2-one had been isolated in two modifications, 94 and 95, was soon disproved. ... 

JesJ73 Jesson, J. P., Meakin, P. Determination of mechanistic information for nuclear magnetic resonance line shape for intramolecular exchange. Accounts of Chem. Res. 6 (1973) 269-275. 

Exchange reactions can be sometimes investigated by the techniques of polari-metry, nuclear magnetic resonance and electron spin resonance. The optical activity method requires polarimetric measurements on the rate of racemization in mixtures of d-X (or /-X) and /-Y (or d-Y). 

Isab, A.A. and Sadler, P.J. (1982) A carbon-13 nuclear magnetic resonance study of thiol exchange reactions of gold(l) thiomalate ( Myocrisin ) including applications to cysteine derivatives. Journal of the Chemical Society, Dalton Transactions, (1), 135—141. 

Beryllium(II) is the smallest metal ion, r = 27 pm (2), and as a consequence forms predominantly tetrahedral complexes. Solution NMR (nuclear magnetic resonance) (59-61) and x-ray diffraction studies (62) show [Be(H20)4]2+ to be the solvated species in water. In the solid state, x-ray diffraction studies show [Be(H20)4]2+ to be tetrahedral (63), as do neutron diffraction (64), infrared, and Raman scattering spectroscopic studies (65). Beryllium(II) is the only tetrahedral metal ion for which a significant quantity of both solvent-exchange and ligand-substitution data are available, and accordingly it occupies a... 

Riickert, M., Wohlfarth, M., and Bringmann, G., Characterization of protein mixtures by ion-exchange chromatography coupled on-line to nuclear magnetic resonance spectroscopy, ]. Chromatogr. A, 840, 131, 1999. 

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