Isotopic labeled fatty acid

Isotopically labelled fatty acids and the lipids derived from them are used in studies of reaction mechanism (e.g. hydrogenation) and of lipid biosynthesis and metabolism. Compounds containing radioactive isotopes ( H, are studied by liquid-scintillation counting or radio gas chromatography. Non-radio-active labels are studied by mass spectrometry or by NMR spectroscopy. 

Adlof, R.O. (1999) Isotopically Labelled Fatty Acids, in Lipids Synthesis and Manitfacture (Gunstone, F.D., ed.) pp. 46-93, Sheffield Academic Press, Sheffield, UK. 

E. Gazi, T. J. Harvey, P. Gardner, N. P. Lockyer, C. A. Hart, N. W. Clarke and M. D. Brown, A FTIR Microspectroscopic Study of the Uptake and Metabolism of Isotopically Labelled Fatty Acids by Metastatic Prostate Cancer, Vib. Spectrosc., 2009, 50, 99-105. 

Kemp, S., Valianpour, R, Mooyer, RA., Kulik, W. and Wanders, R.J., Method for measurement of peroxisomal very-long-chain fatty acid beta-oxidation in human skin fibroblasts using stable-isotope-labeled tetracosanoic acid. Clin. Chem., 50, 1824-1826 (2004). 

The particulars of the condensation mechanism will be disregarded for the moment. The essential point here is that 2-carbon fragments are formed from fatty acids which may then condense to yield acetoacetate. The fact that little or no isotope is found in the a- and y-carbons of acetoacetate from carboxyl-labeled fatty acids in liver - - or from carboxyl-labeled acetate in kidney slices provides evidence that the orientation of the carbons of the 2-carbon fragment is not altered. 

Problem 29.5 Evidence for the role of acetate in fatty-acid biosynthesis comes from isotope-labeling experiments. If acetate labeled with 13C in the methyl group ( CFtyCC H) were incorporated into fatty acids, at what positions in the fatty-acid chain would you expect the, 3C label to appear ... 

Elucidation of the physiological role of arachidonic acid 13 and other polyunsaturated fatty acids, particularly the role of all Z-4,7,10,13,16,19-decosahexaenoic acid 14, found in brain, required the corresponding stable-isotope labelled material1011. The deuteriated phosphonium salt 15, the key intermediate used in the synthesis of title compound 16 (equation 8), has been prepared in 19% overall yield12 starting with ethanol-D6 (equation 7). 

The authors have also synthesized134 fatty acids labelled with deuterium and carbon-11 in order to investigate if kinetic isotope effects related to fatty acid metabolism can be observed in vivo by pet133,135-137. In vitro, the large kinetic deuterium isotope effects are observed in the oxidation of deuteriated aliphatic carboxylic acids with alkaline permanganate and manganate135-139. 

A polyketide/fatty acid-type metabolic route using three propionate units has been shown by stable isotope-labeled probes and MS to the biosynthetic route towards the production of the insect pheromone (Sl-d-methyl-d-heptanone in the ant Harpegnathos saltator. 

Later experiments using isotopic labeling with 13C verified Knoop s proposals/but study of isolated enzymes was not possible until after the discovery of coenzyme A in 1950. Then, studies of fatty acid oxidation by extracts from isolated mitochondria established the details of the pathway/... 

It should be stressed that it is a prerequisite of successful flavor precursor studies that the contribution of the odorant under investigation to a food flavor or off-flavor has been established. Sometimes the structure of a precursor can be assumed on the basis of structural elements in the odorant. In such cases, additions of the respective isotope-labelled precursor to the food system is commonly used to elucidate the precursor and to clarify reaction pathways governing the formation of the odorant. This method has been frequently applied, especially, in studies on the enzymatic generation of odor-active aldehydes (e.g., (Z)-3-hexenal in tea leaves) or alcohols (e.g., l-octen-3-oI in mushrooms) [cf. reviews in 84, 85] as well as lactones [86] from unsaturated fatty acids. 

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