Nuclear magnetic resonance nitrogen-15 labeling

The mechanism outlined above is supported by experimental findings. An intermediate 5 has been isolated, " and has been identified by and N-nuclear magnetic resonance spectroscopy. Side-products have been isolated, which are likely to be formed from intermediate 4. N-isotope labeling experiments have shown that only the nitrogen remote from the phenyl group is eliminated as ammonia. 

Callies, R Altenburger, R., Abarzua, S Mayer, A., Grimme, L.H., Leibfritz, D. (1992). In situ nuclear magnetic resonance of 15N pulse labels monitors different routes for nitrogen assimilation. Plant Physiol. 100, 1584-1586. 

All but the smallest proteins studied by nuclear magnetic resonance (NMR) need to be labeled with isotopes of hydrogen, nitrogen, or carbon ( H, C), or combi-... 

D, the investigation of the biosynthesis of the latter two metabolites was initiated in our laboratory in 1970. The biosynthetic studies are carried out as in vitro experiments. A synthetic medium serves for the cultivation of the microorganisms. The culture is incubated with potential biogenetic precursors radioactively labeled ( H, or labeled with the radioinactive isotopes or If possible, the precursors are added to the culture when the cytochalasin production begins. For this purpose, the rate of formation of the secondary metabolite must be determined. The cytochalasins are isolated in the usual fashion. To localize the radioactive atoms incorporated into the molecule, the specimen is subjected to a specific chemical degradation. In the experiments with C-labeled precursors, carbon-13 nuclear magnetic resonance NMR) is used. Mass spectrometry serves for the determination of nitrogen-15. 

Molecular nitrogen, N2, is one of the most extensively studied diatomic molecules and optical spectroscopy has provided a wealth of information about its ground and excited electronic states. Molecular beam magnetic resonance studies of N2 in its ground state have yielded information about 14N nuclear spin dipolar and quadrupole interactions. Similar studies of N2 in its electronically excited A 3LU state were described in two very extensive papers by Freund, Miller, De Santis and Lurio [43] (paper I) and De Santis, Lurio, Miller and Freund [44] (paper II). We will describe their results and analysis in detail, but first note in passing that, strictly speaking, the lowest excited triplet state should be labelled the a state the label A has been used by all concerned in the past, so we will continue to do so. 

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