14C incorporation

Scheme 14 Biosynthesis of the C5 unit of thiamin from isotopically labelled hexoses. Label from D-[l-14C]glucose and D-[l-uC]fructose label C-4 exclusively D-[2-14C]glucose labels C-4 and C-4 equally D-[6-14C]glucose labels C-4 (16% of 14C incorporated the precise location of the remaining 14C was not determined) d-[6-D2]glucose gives rise to both [4 -D2]- and [7-D2]-thiamin...

Moran, X. A. G., and M. Estrada. 2000. Phytoplankton DOC and POC production in the Bransfield and Gerlache straits as derived from kinetic experiments of 14C incorporation. Deep Sea Research, in Press. 

Ireland, C. M. and Scheuer, P. J., Photosynthetic marine mollusks in vivo 14C incorporation into metabolites of the sacoglossan Placobranchus ocellatus, Science, 205, 922, 1979. 

By the third decade of the twentieth century, the emitted radioactivity from artificially synthesized tritium (3H) and carbon-14 (14C) was used to follow biochemical reactions. Glucose, amino acids, and other chemical compounds were synthesized with 3H or 14C incorporated either randomly or at some known position in the molecule. The radioactive products derived from radiolabeled glucose or amino acids added to cells, tissue slices, or a whole organism identified the metabolic fate of these molecules under defined... 

C-labeled D-glucose (34) [87, 88] and D-ribose [87] were efficiently incorporated... 

Dehydroquinic acid and [l,6-14C]-D-shikimic acid methyl ester were not incorporated, indicating a very early branch from the shikimate pathway. The intermediacy of 4-amino-3,4-dideoxy-D-araf>ino-heptulosonic acid 7-phosphate (37) was proposed, consistent with later findings on the role of the variant aminoshikimate pathway [94]. 

Initially, attempts to grow the organism on sodium acetate as the sole source of carbon were unsuccessful, but the difficulties were overcome and mannitol, arabinitol, erythritol, glycerol, maltose, and a,a-trehalose were produced. This was a useful development because conditions were established for the incorporation of [14C] acetate, thereby making labeled polyols and disaccharides available. 

By analogy with the asymmetrical incorporation of [2-14C] ornithine it was proposed (5,116,117) (Scheme 22) that to avoid the formation of putrescine... 

The in vivo transformation of [6-14C]strictosidine (19) to gelsemine in Gelsemium sempervirens was claimed with an incorporation of 0.47% (33). This provides another experimental support to the proposal that strictosidine appears to be the original precursor in the biosynthesis of monoterpenoid indole alkaloids, although the detailed pathway of this biosynthetic process still remains obscure. 

Leaf discs from rapidly expanding V.faba leaves incorporated 14C-labeled palmitic acid into cutin. After removal of the soluble lipids and other materials, the insoluble residue was subjected to LiAlH4 hydrogenolysis and the labeled reduction products of cutin monomers were identified by chromatography as hexadecane-... 

The incorporation of 14C into compounds at a suitable site often requires extensive and complicated syntheses, and thus a relatively long time. This usually means that 14C-labeled compounds are unsuitable for studies to be carried out during discovery. There are however, very rapid methods for incorporating 3 H into compounds. The newer methods, generally involving metal-catalyzed exchange reactions [15-18], in our experience, mean that suitable labels can often be prepared in 2 or 3 weeks. These time scales make the approach viable for discovery support. Additionally, and importantly, these methods can lead to specific incorporation of tritium. 

The study above does not account for the extra six carbons acquired in the conversion of piperideine (8, 10 carbons) to phlegmarine (9, 16 carbons). It was initially proposed that the carbons were incorporated via pelletierine (12), which was incorporated twice into lycopodine resulting in two symmetrical halves of the alkaloid (Scheme 6.2). However, when 14C-labeled pelletierine (12, label at C2) was fed to the plant, degradation studies of lycopodine revealed that only one half consisted of the 14C label from pelletierine (the half containing C9-C16) [10]. The other half does not result from pelletierine 12 but must be something similar in structure since it does contain the piperideine unit (8) resulting from lysine. It was of interest then to determine the exact source of the three-carbon propionate unit in pelletierine (12). 

In order to investigate whether the above glycerides are derived from the animal s diet or by biosynthesis, [2-14C]RS-mevalonic add DBED salt was injected into the digestive gland of A. montereyensis and A. odhneri spedmens, which were placed in a running sea-water aquarium for 24 h and then extracted [79]. Incorporation of the label was checked in the major metabolites of the two nudibranchs, namely 23 and 51 in A. montereyensis and 47 in A. odhneri, after HPLC purification and conversion to derivatives that were also purified via... 

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