3H NMR spectroscopy

The quaternization kinetics were followed by 3H NMR spectroscopy using a JE0L FX-90Q NMR spectrometer. Solvolysis of p nitro-phenylacetate was followed by UV spectroscopy using a Hewlett Packard 8450 A diode array spectrophotometer. 

The tritiated version could be prepared from tritiated formic acid which we had prepared at high specific activity (2.5 Ci mmol-1) by a metal-catalyzed hydrogen-tritium exchange procedure using T2 gas. The material can be stored either as a solid or as a solution if the latter any release of tritium by back exchange can be easily monitored by 3H NMR spectroscopy. In our experience very little exchange occurs over several weeks of storage [51]. 

The comprehensive dedicated research ultimately made it possible to decode the patterns of labelling in almost any type of tritium labelled compound at low isotopic abundance (e.g., 3 x 10 4 to 3 x 10 2 per cent. 3H per site) with the aid of 3H-NMR directly, rapidly, reliably and non-destructive analytical means. Since, 1971, the 3H-NMR spectroscopy, utilizing only millicurie (mCi) quantities of radioactivity, emerged as a most useful analytical tool for the study of tritium labelled compounds. 

The two major advantages of 3H-NMR spectroscopy based on the characteristic magnetic features of the tritium nucleus are, namely ... 

Variable-temperature 3H and 31P NMR spectra for Os(r 2-H2)(bipy)[P]3 +, where [P] = P(OEt)3, PPh(OEt)2, confirmed the presence of the dihydrogen ligand.924 Variable-temperature 3H NMR spectroscopy was used to study the hydride dynamics in [H Osk/CO ], showing that p2-hydrides are much more mobile than p3-.925... 

Water Sorbed on to Solids. Solid-state 3H NMR spectroscopy was used to determine the characteristics of H20 adsorbed on Ti02 photocatalytic systems.623,624 The dynamics of water molecules in the deuteriated analogue of H3PWi204o.nH20, where n = 5.5 or 0.1, were followed by solid-state 2H NMR spectra.625... 

H- and 13C-NMR data have been reported for diagnostic purposes in direct analysis of phenylthiohydantoin amino acid derivatives (PTH) produced in the Edman degradation of peptides and proteins.189-193 The insensitivity of 3H-NMR spectroscopy constitutes a major hurdle for its application in the sequence study of peptides.194,195 Alternatively, identification of the cleaved amino acids in the automated Edman degradation has been solved in some cases by using IR,196-198 mass,199 and gas chromatographic techniques.200... 

These predictions were subsequently verified experimentally for [Cp Ru(dppm) (H2)]+ by study of the HD, HT, and DT complexes using H and 3H NMR spectroscopy.55 A significant isotope effect was observed on the values of the HT... 

An example of thione coordination is demonstrated with the thiocarbonyl donor ligand 2,6-dimethyl-4H-pyran-4-thione, that gives a complex with zinc chloride of the form ZnL2Cl2-The crystal structure shows the zinc is tetrahedrally coordinated by two chloride and two sulfur donors and the compound was further studied by 3H NMR and IR spectroscopy.573 Both monomeric and dimeric heterocyclic thione complexes have been formed with zinc.5 4,575... 

Within meat science, NMR spectroscopy has mainly been carried out on 3H, 13C and 31P, which all are nuclei with a nuclear spin of /= 1/2. Most relevant data on each nucleus will be reviewed in the following. 

Nevertheless, I. l3C NMR spectroscopy has not yet reached the importance and ubiquity of 3H NMR, and detailed discussions of 13C spectral parameters are... 

With counteranions of lower nucleophilicity the " Sn NMR chemical resonance of solutions of tributyl tin salts is further shifted to lower field. Lambert and Kuhlmann reported for the tiibutylstarmyl borate Bu3SnB(C6F5)3H 8" Sn = 360 in benzene and Kira and co-workers found for the related BusSnTFPB 8 Sn = 356 in CD2Cl2. In the latter case, F NMR spectroscopy indicates no cation-anion interaction. Finally, for Bu3SnTPFPB in toluene at —60 °C 5" Sn = 434.2 was reported by Piers et The solvent dependence of the Sn NMR chemical shift suggests... 

Traditional protein NMR spectroscopy of smaller proteins relies of 15N-filtered experiments, due to the relatively low expense of introducing 15N labels into proteins (compared to 13C) and the concomitant ability to use heteronuclear filtering to improve resolution in the H NMR dimension. Jelinek et al. were the first to demonstrate the ability to transfer this approach to peptides on TantaGel.80 They also showed the ability to detect pronounced peptide structure through the appearance of strong NOE correlations in 3H NOESY HRMAS spectra as shown in Fig. 8. This had important implications for the search of biological activity in peptides attached to supports, as the structure on the support may be different or more pronounced than in solution, if present at all in solution in peptides of this small size. 

Characterization of complexes has generally been based on solution studies, for example using NMR spectroscopy (3H 426 13C,427 15N428) since few reports have dealt with isolated complexes.422... 

Peptide aldehydes are fairly reactive and usually exist in solution partially as hydrates Xaa[CH(OH)2] (e.g., 3), which are identified using 13C NMR spectroscopy. 3 3" With amino acids containing nucleophilic side chains, cyclized forms predominate (Scheme 2). Argininal analogues such as Z-Leu-Phe-Arg-H have been shown to exist primarily as the carbinol amine 4 with no spectroscopic evidence for an iminium structure. Lysinal derivatives such as Z-Leu-Phe-Lys-H exist both as a cyclic carbinol amine 5 and as an iminium ion 6 as shown by 3H and 13C NMR spectra. The C-terminal ornithinal analogue Z-Leu-Phe-Orn-H exists primarily as the carbinol amine form 7 and the cyclic iminium form 8 as characterized by the 13C NMR spectra. 3,21 In general, the existence of carbinol and iminium cyclized forms does not preclude the existence of the free or hydrated aldehydes under aqueous conditions. 

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