Nitrogen-15 Labelling

Figure 1 Fate of N-labelled nitrogen fertilizer applied to a winter wheat erop. (Taken from Maedonald et...

The best overall recovery of labelled fertilizer in crop and soil was 99% and the leastsatisfactory 65%. Thus 1-35% ofthe labelled nitrogen, onaverage 15.7%, was missing, presumed lost . These losses occurred between the time of the fertilizer application in spring and the time the crop was harvested but why and how did they occur ... 

The reason why the losses occurred is simply because it rained . The more rain that fell in the period after application, the more labelled nitrogen was lost. The critical period seemed to be the first three weeks after application this was the period that showed the closest relationship between the losses and the rainfall (Figure 2). ... 

Up to Harvest. Oilseed rape and field beans are used as break crops for winter wheat on a variety of soils, and potatoes are used on the lighter soils. Sugar beet may also be grown, but this depends not only on the soil but also on the proximity of a sugar beet processing factor. Four Rothamsted-based experiments compared the effectiveness of winter wheat and winter oilseed rape in their use of labelled nitrogen fertilizer. Potatoes were included in two of these experiments and sugar beet and field beans in one experiment each. Two criteria based on the... 

Thus, upon photolyzing a mixture of two nitrites, one of which contains an isotopically labeled nitrogen, the products should show the original isotopic distribution if mechanism (a) is operative, the original isotopic distribution in unreacted nitrite but scrambling in the nitroso product if (c) is operative, and complete isotopic scrambling if (b) is operative. 

According to Guiochon [17] the experiments with labelled nitrogen atoms seem to support an earlier suggestion of Davis and Abrams [21] that the decomposition of ammonium nitrate may pass through the intermediate formation of nitramide through dehydration of ammonium nitrate in the first stage (7) ... 

The precise nature of the reaction path is ambiguous, because the same products would be obtained regardless of whether an oxygen atom or a chlorine atom were transferred. As they pointed out in their paper, this ambiguity can be resolved by using nitryl chloride with isotopically labeled nitrogen. Pertinent to this question are the calculations of Herschbach, Johnston, Pitzer, and Powell,199 who computed pre-exponential factors based on two alternative activated complexes... 

The H15N03 produced can be used to prepare other 15N-labeled nitrogen compounds. 

Tietema, A., Emmett, B. A., Gundersen, P., Kjonaas, O. J. Koopmans, C. J. (1998). The fate of N-labelled nitrogen deposition in coniferous forests. Forest Ecology and Management, 101, 19—27. 

Slawyk, G., Raimbault, P., and Garcia, N. (1998). Measuring gross uptake of N-labeled nitrogen by marine phytoplankton without particulate matter collection Evidence for low N losses to the dissolved organic nitrogen pool. Limnol. Oceanogr. 43(7), 1734-1739. 

They then studied the reaction between isotopically labeled nitrogen dioxide and ordinary SO2. The formation of labeled SO2 was taken as evidence for reaction ( — 14), and therefore for the mechanism consisting of (14) and (15). From the rate of isotopic substitution, Jaffe and Klein were able to calculate and -14-1 15 Their results were... 

Preparation of heterocyclic compounds by coupling two constituents with a titanium Lewis acid is shown in Eqs (241) and (242). A C-labeled nitrogen heterocycle was synthesized by condensation of a keto-oxime and a-aminonitrile in the presence... 

Labeled nitrogen. Purine biosynthesis is allowed to take place in the presence of [i N]aspartate, and the newly synthesized GTP and ATP are isolated. What positions are labeled in the two nucleotides ... 

Chichester F. W. (1970) Tranformations of fertilizer nitrogen in soil II. Total and N15-labelled nitrogen of soil organo-mineral sedimentation fractions. Plant Soil 33, 437-456. 

Unexpectedly, reactions of some hetaryl halides with amide ion in ammonia do not follow an SnAt pathway. Although the structures of the products provide no clues that new routes are being followed, the use of isotopically labelled nitrogen atoms reveals unanticipated complexities. 

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