The financial support of R. Menzel and L. Ruess by the Deutsche Forschungsgemeinschaft (RU RU780/11-1) is gratefully acknowledged. R. Nehring was funded by RU 780/10-1. Finally, we are extremely thankful to Dr. Hazel Ruvimbo Maboreke for proofreading our manuscript.

<ol>
	<li>Ruess, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Application+of+lipid+analysis+to+understand+trophic+interactions+in+soil.">Application of lipid analysis to understand trophic interactions in soil.</a> Ecology. 86 (8), 2075-2082 (2005).</li><li>Ruess, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lipid+composition+of+Collembola+and+their+food+resources+in+deciduous+forest+stands+-+Implications+for+feeding+strategies.">Lipid composition of Collembola and their food resources in deciduous forest stands - Implications for feeding strategies.</a> Soil Biology and Biochemistry. 39 (8), 1990-2000 (1990).</li><li>Chamberlain, P. M., Bull, I. D., Black, H. I. J., Ineson, P., Evershed, R. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fatty+acid+composition+and+change+in+Collembola+fed+differing+diets:+identification+of+trophic+biomarkers.">Fatty acid composition and change in Collembola fed differing diets: identification of trophic biomarkers.</a> Soil Biology and Biochemistry. 37 (9), 1608-1624 (2005).</li><li>Stott, A. W., Davies, E., Evershed, R. P., Tuross, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monitoring+the+routing+of+dietary+and+biosynthesised+lipids+through+compound-specific+stable+isotope+(delta+C-13)+measurements+at+natural+abundance.">Monitoring the routing of dietary and biosynthesised lipids through compound-specific stable isotope (delta C-13) measurements at natural abundance.</a> Naturwissenschaften. 84 (2), 82-86 (1997).</li><li>Ruess, L., Haggblom, M. M., Langel, R., Scheu, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nitrogen+isotope+ratios+and+fatty+acid+composition+as+indicators+of+animal+diets+in+belowground+systems.">Nitrogen isotope ratios and fatty acid composition as indicators of animal diets in belowground systems.</a> Oecologia. 139 (3), 336-346 (2004).</li><li>Pollierer, M. M., Scheu, S., Haubert, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Taking+it+to+the+next+level:+Trophic+transfer+of+marker+fatty+acids+from+basal+resource+to+predators.">Taking it to the next level: Trophic transfer of marker fatty acids from basal resource to predators.</a> Soil Biology and Biochemistry. 42 (6), 919-925 (2010).</li><li>Ferlian, O., Scheu, S., Pollierer, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trophic+interactions+in+centipedes+(Chilopoda,+Myriapoda)+as+indicated+by+fatty+acid+patterns:+Variations+with+life+stage,+forest+age+and+season.">Trophic interactions in centipedes (Chilopoda, Myriapoda) as indicated by fatty acid patterns: Variations with life stage, forest age and season.</a> Soil Biology and Biochemistry. 52, 33-42 (2012).</li><li>Ruess, L., Chamberlain, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+fat+that+matters:+Soil+food+web+analysis+using+fatty+acids+and+their+carbon+stable+isotope+signature.">The fat that matters: Soil food web analysis using fatty acids and their carbon stable isotope signature.</a> Soil Biology and Biochemistry. 42 (11), 1898-1910 (2010).</li><li>Traugott, M., Kamenova, S., Ruess, L., Seeber, J., Plantegenest, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Empirically+characterising+trophic+networks:+What+emerging+DNA-based+methods,+stable+isotope+and+fatty+acid+analyses+can+offer.">Empirically characterising trophic networks: What emerging DNA-based methods, stable isotope and fatty acid analyses can offer.</a> Adv Ecol Res. 49, 177-224 (2013).</li><li>Hammer, B. T., Fogel, M. L., Hoering, T. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stable+carbon+isotope+ratios+of+fatty+acids+in+seagrass+and+redhead+ducks.">Stable carbon isotope ratios of fatty acids in seagrass and redhead ducks.</a> Chemical Geology. 152 (1-2), 29-41 (1998).</li><li>Budge, S. M., Iverson, S. J., Koopman, H. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Studying+trophic+ecology+in+marine+ecosystems+using+fatty+acids:+A+primer+on+analysis+and+interpretation.">Studying trophic ecology in marine ecosystems using fatty acids: A primer on analysis and interpretation.</a> Marine Mammal Science. 22 (4), 759-801 (2006).</li><li>Haubert, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trophic+structure+and+major+trophic+links+in+conventional+versus+organic+farming+systems+as+indicated+by+carbon+stable+isotope+ratios+of+fatty+acids.">Trophic structure and major trophic links in conventional versus organic farming systems as indicated by carbon stable isotope ratios of fatty acids.</a> Oikos. 118 (10), 1579-1589 (2009).</li><li>Ngosong, C., Raupp, J., Richnow, H. H., Ruess, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tracking+Collembola+feeding+strategies+by+the+natural+13C+signal+of+fatty+acids+in+an+arable+soil+with+different+fertilizer+regimes.">Tracking Collembola feeding strategies by the natural 13C signal of fatty acids in an arable soil with different fertilizer regimes.</a> Pedobiologia. 54 (4), 225-233 (2011).</li><li>Bec, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessing+the+reliability+of+fatty+acid-specific+stable+isotope+analysis+for+trophic+studies.">Assessing the reliability of fatty acid-specific stable isotope analysis for trophic studies.</a> Methods in Ecology and Evolution. 2 (6), 651-659 (2011).</li><li>Gladyshev, M. I., Makhutova, O. N., Kravchuk, E. S., Anishchenko, O. V., Sushchik, N. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stable+isotope+fractionation+of+fatty+acids+of+Daphnia+fed+laboratory+cultures+of+microalgae.">Stable isotope fractionation of fatty acids of Daphnia fed laboratory cultures of microalgae.</a> Limnologica. 56 (Supplement C. 56 (Supplement C), 23-29 (2016).</li><li>Gladyshev, M. I., Sushchik, N. N., Kalachova, G. S., Makhutova, O. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stable+isotope+composition+of+fatty+acids+in+organisms+of+different+trophic+levels+in+the+Yenisei+river.">Stable isotope composition of fatty acids in organisms of different trophic levels in the Yenisei river.</a> PLoS One. 7 (3), e34059 (2012).</li><li>Eisenreich, W., Dandekar, T., Heesemann, J., Goebel, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carbon+metabolism+of+intracellular+bacterial+pathogens+and+possible+links+to+virulence.">Carbon metabolism of intracellular bacterial pathogens and possible links to virulence.</a> Nature Reviews Microbiology. 8 (6), 401-412 (2010).</li><li>Eylert, E., Bacher, A., Eisenreich, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NMR-based+isotopologue+profiling+of+microbial+carotenoids.">NMR-based isotopologue profiling of microbial carotenoids.</a> Methods Mol Biol. 892, 315-333 (2012).</li><li>Garton, N. J., O'Hare, H. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tuberculosis:+feeding+the+enemy.">Tuberculosis: feeding the enemy.</a> Chemical Biology. 20 (8), 971-972 (2013).</li><li>Rosenblatt, J., Chinkes, D., Wolfe, M., Wolfe, R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stable+isotope+tracer+analysis+by+GC-MS,+including+quantification+of+isotopomer+effects.">Stable isotope tracer analysis by GC-MS, including quantification of isotopomer effects.</a> Am J Physiol. 263 (3), E584-E596 (1992).</li><li>Fernandez, C. A., Des Rosiers, C., Previs, S. F., David, F., Brunengraber, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correction+of+13C+mass+isotopomer+distributions+for+natural+stable+isotope+abundance.">Correction of 13C mass isotopomer distributions for natural stable isotope abundance.</a> J Mass Spectrom. 31 (3), 255-262 (1996).</li><li>Heuner, K., Eisenreich, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+intracellular+metabolism+of+legionella+by+isotopologue+profiling.">The intracellular metabolism of legionella by isotopologue profiling.</a> Methods Mol Biol. 954, 163-181 (2013).</li><li>Willenborg, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+the+pivotal+carbon+metabolism+of+Streptococcus+suis+serotype+2+under+ex+vivo+and+chemically+defined+in+vitro+conditions+by+isotopologue+profiling.">Characterization of the pivotal carbon metabolism of Streptococcus suis serotype 2 under ex vivo and chemically defined in vitro conditions by isotopologue profiling.</a> J Biol Chem. 290 (9), 5840-5854 (2015).</li><li>Menzel, R., Ngosong, C., Ruess, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isotopologue+profiling+enables+insights+into+dietary+routing+and+metabolism+of+trophic+biomarker+fatty+acids.">Isotopologue profiling enables insights into dietary routing and metabolism of trophic biomarker fatty acids.</a> Chemoecology. 27 (3), 101-114 (2017).</li><li>Buse, T., Ruess, L., Filser, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+trophic+biomarkers+for+Collembola+reared+on+algal+diets.">New trophic biomarkers for Collembola reared on algal diets.</a> Pedobiologia. 56 (3), 153-159 (2013).</li><li>Hutson, B. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+variations+of+the+plaster-charcoal+culture+method+on+a+Collembolan,+Folsomia+candida.">Effects of variations of the plaster-charcoal culture method on a Collembolan, Folsomia candida.</a> Pedobiologia. 18, 138-144 (1978).</li><li>Fountain, M. T., Hopkin, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Folsomia+candida+(Collembola):+a+&amp;#34;standard&amp;#34;+soil+arthropod.">Folsomia candida (Collembola): a &amp;#34;standard&amp;#34; soil arthropod.</a> Annu Rev Entomol. 50, 201-222 (2005).</li><li>ISO, I. O. f. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Soil Quality-Inhibition of reproduction of Collembola (Folsomia candida) by soil pollutants. , (1999).</li><li>Welch, D. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applications+of+cellular+fatty+acid+analysis.">Applications of cellular fatty acid analysis.</a> Clin Microbiol Rev. 4 (4), 422-438 (1991).</li><li>Dodds, E. D., McCoy, M. R., Rea, L. D., Kennish, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gas+chromatographic+quantification+of+fatty+acid+methyl+esters:+flame+ionization+detection+vs.+electron+impact+mass+spectrometry.">Gas chromatographic quantification of fatty acid methyl esters: flame ionization detection vs. electron impact mass spectrometry.</a> Lipids. 40 (4), 419-428 (2005).</li><li>Kuppardt, S., Chatzinotas, A., Kastner, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+fatty+acid+and+RNA+stable+isotope+probing-based+method+for+tracking+protist+grazing+on+bacteria+in+wastewater.">Development of a fatty acid and RNA stable isotope probing-based method for tracking protist grazing on bacteria in wastewater.</a> Appl Environ Microbiol. 76 (24), 8222-8230 (2010).</li><li>Zhang, X., He, H., Amelung, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+GC/MS+method+for+the+assessment+of+15N+and+13C+incorporation+into+soil+amino+acid+enantiomers.">A GC/MS method for the assessment of 15N and 13C incorporation into soil amino acid enantiomers.</a> Soil Biology and Biochemistry. 39 (11), 2785-2796 (2007).</li><li>Vetter, W., Thurnhofer, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+fatty+acids+by+mass+spectrometry+in+the+selected+ion+monitoring+mode.">Analysis of fatty acids by mass spectrometry in the selected ion monitoring mode.</a> Lipid Technol. 19 (8), 184-186 (2007).</li><li>Thurnhofer, S., Vetter, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+gas+chromatography/electron+ionization-mass+spectrometry-selected+ion+monitoring+method+for+determining+the+fatty+acid+pattern+in+food+after+formation+of+fatty+acid+methyl+esters.">A gas chromatography/electron ionization-mass spectrometry-selected ion monitoring method for determining the fatty acid pattern in food after formation of fatty acid methyl esters.</a> J Agric Food Chem. 53 (23), 8896-8903 (2005).</li><li>Haubert, D., Haggblom, M. M., Scheu, S., Ruess, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+fungal+food+quality+and+starvation+on+the+fatty+acid+composition+of+Protaphorura+fimata+(Collembola).">Effects of fungal food quality and starvation on the fatty acid composition of Protaphorura fimata (Collembola).</a> Comparative Biochemistry and Physiology B-Biochemistry &amp; Molecular Biology. 138 (1), 41-52 (2004).</li></ol>

Isotopologue profiling
A detailed analysis of the quantitative aspects in 13C distribution in FAs needs cutting-edge technology to assign carbon partitioning in food webs. The present work employed isotopologue profiling to assess the 13C/12C ratios in common FA biomarkers for tropic interactions. This method is well established for amino acid analysis by liquid chromatography (LC-MS) and was applied for investigations of carbon metabolism in p...

In a cryptic habitat such as soil, trophic relationships are difficult to address and are further restricted by the small size of the fauna. The last decade has seen advances in biochemical ecology, particularly in the use of fatty acids as biomarkers for defining feeding strategies of the soil fauna under field conditions1,2,3. This is based on the fact that fatty acids from resources can be incorporated in consumer tissue as entire molecules, a process termed dietary routing4. Transfer of fatty acids has been reported over three trophic levels, i.e., from fungi to nematodes to Collembola5. Recently, the predatory fauna was considered6,7 and the first reviews on fatty acids as trophic markers in soil food webs have been published8,9.
More detailed information on trophic interactions is attained by fatty acid stable isotope probing (FA-SIP). The determination of 13C/12C ratios in fatty acids in diets and consumers can ascribe binary links and estimate the associated carbon flow, and has been employed in terrestrial, fresh water, and marine food webs10,11,12,13. The basic assumption is that dietary routed fatty acids are not subject to enzymatic processes; therefore, their 13C signal, i.e., the 13C/12C ratio of the fatty acid, in the consumer is similar to that in the diet1. However, a gradual depletion of the 13C signature up the food chain has been reported in aquatic systems, thereby hindering broad application of FA-SIP in trophic studies14,15,16. Moreover, knowledge in the lipid metabolism in most invertebrates in terrestrial food webs is still limited.
An understanding of the lipid metabolism pathways in consumers is essential for the usage of trophic marker fatty acids as means for the determination of the quantitative carbon flow in food web ecology. With this in mind, 13C-isotopologue profiling, which in principle can be applied for investigation of the carbon metabolism of any biological system17, is a promising method. Following the introduction of a 13C-labelled carbon substrate, the distribution of the 13C in the metabolic network is traceable since the generated metabolic products in the consumer show a specific isotopologue distribution. This can be assessed by quantitative nuclear metabolic resonance spectroscopy18,19 or mass spectrometry20,21, with the latter favored in biological samples with low biomass due to its higher sensitivity.
Although isotopologue profiling has been successfully applied to amino acids and provided insight into the in vivo carbon metabolism of bacterial pathogens17,22,23, its implementation in fatty acids has lagged behind. The first detailed analysis on the fate of a stable isotope labelled precursor fatty acid, its dietary routing or degradation via &#946;-oxidation, in soil invertebrate consumers, was recently performed by Menzel et al.24. Here, the methodological basics for incorporation experiments with 13C labelled fatty acids followed by isotopologue analysis of key descendants in frequent soil invertebrates, the Collembola, are provided. These microarthropods are a good model group as they form important components of the soil food web and are well investigated for their trophic marker fatty acids8,25.
An understanding of the lipid metabolism pathways in consumers is essential for the usage of trophic marker fatty acids as means for the determination of the quantitative carbon flow in food web ecology. The present protocol gives the design and set up for a laboratory feeding experiment, and the biochemical procedures for extraction and methylation of dominant lipids fractions (neutral lipids, phospholipids) from Collembola. It demonstrates how the isotopologue composition of fatty acids is analyzed by mass spectrometry and describes the related formula and calculations. This procedure results in: (i) the ratios of isotopologues exceeding the mass of the parent ion (i.e., the fatty acid molecular ion M+) by one or more mass units (M+1, M+2, M+3, etc.) and (ii) the overall 13C enrichment in fatty acids derived from the 13C labelled precursor. Although used for Collembola, this approach can generally be applied to any other predator-prey interaction on the premise that these are culturable in sufficient quantity under controlled conditions to ensure a successful label uptake and subsequent verification.

<table><tbody><tr><td>neoLab-Round jars</td><td>neoLab</td><td>2-1506</td><td>69 x 40 mm, 10 pacs/pack</td></tr><tr><td>Charcoal activated</td><td>Carl Roth</td><td>X865.1</td><td>p.a., powder, CAS No. 7440-44-0</td></tr><tr><td>Alabaster Dental</td><td>R&amp;Ouml;HRICH-GIPSE</td><td>---</td><td>http://www.roehrich-gipse.de/dentalgipse.php</td></tr><tr><td>Chloroform</td><td>Carl Roth</td><td>7331.1</td><td>HPLC &amp;ge; 99,9 %</td></tr><tr><td>Methanol</td><td>Carl Roth</td><td>P717.1</td><td>HPLC &amp;ge; 99,9 %</td></tr><tr><td>Hexan</td><td>Carl Roth</td><td>7339.1</td><td>HPLC &amp;ge; 98 %</td></tr><tr><td>&lt;em&gt;tert&lt;/em&gt;-Butyl methyl ether (MTBE)</td><td>Carl Roth</td><td>T175.1</td><td>HPLC &amp;ge; 99,5 %</td></tr><tr><td>Aceton</td><td>Carl Roth</td><td>7328.2</td><td>HPLC &amp;ge; 99,9 %</td></tr><tr><td>NaOH</td><td>Carl Roth</td><td>6771.1</td><td>p.a. &amp;ge;99 %, in pellets</td></tr><tr><td>di-Natriumhydrogenphosphat</td><td>Carl Roth</td><td>P030.1</td><td>p.a. &amp;ge;99 % , water free</td></tr><tr><td>Na-dihydrogenphosphat Dihydrat</td><td>Carl Roth</td><td>T879.1</td><td>p.a. &amp;ge;99 %</td></tr><tr><td>Hypochloric acid (6 N)</td><td>VWR International</td><td>26,115,000</td><td>AVS TITRINORM vol. solution</td></tr><tr><td>Bond Elut (Columns)</td><td>Agilent Tech.</td><td>14102037</td><td>HF Bond Elut-SI, 500 mg, 3 mL, 50/PK</td></tr><tr><td>Pr&amp;auml;paratengl&amp;auml;ser Duran</td><td>Glasger&amp;auml;tebau Ochs</td><td>135215</td><td>&amp;Oslash; 16 x 100 mm, plus screw cap with handy knurl and integrated PTFE/silicone gasket</td></tr><tr><td>Supelco 37 Component FAME Mix</td><td>Sigma-Aldrich</td><td>47885-U Supelco</td><td>10&amp;nbsp;mg/mL in methylene chloride, analytical standard</td></tr><tr><td>FlowMesh</td><td>Carl Roth</td><td>2796.1</td><td>Polypropylene mesh, approximately 0.3 mm thick, with 1 mm strand spacing</td></tr><tr><td>Bacterial Acid Methyl Ester (BAME) Mix</td><td>Sigma-Aldrich</td><td>47080-U Supelco</td><td>10&amp;nbsp;mg/mL in methyl caproate, analytical standard</td></tr><tr><td>Methyl nonadecanoate</td><td>Sigma-Aldrich</td><td>74208</td><td>analytical standard &amp;ge; 98.0 %</td></tr><tr><td>Hexadecanoic acid-1-13C (Palmitic)</td><td>Larodan Fine Chemicals</td><td>78-1600</td><td>GC &amp;ge; 98.0 % (&lt;sup&gt;13&lt;/sup&gt;C: 99.0 %)</td></tr><tr><td>RVC 2-25 CDplus</td><td>Martin Christ Gefrier-trocknungsanlagen</td><td></td><td>Compact benchtop midi concentrator</td></tr><tr><td>Alpha 2-4 LDplus</td><td>Martin Christ Gefrier-trocknungsanlagen</td><td></td><td>Drying manifold</td></tr><tr><td>MZ 2C NT</td><td>Vacuubrand GMBH</td><td></td><td>Vacuum pump</td></tr><tr><td>Roto-Shake Genie</td><td>Scientific Industries</td><td></td><td>Combined rocking and rotating device</td></tr><tr><td>XP64 Micro Comparator</td><td>Mettler Toledo</td><td></td><td>Super high precision balance</td></tr><tr><td>GC-System 7890A</td><td>Agilent Tech.</td><td></td><td>Gas chromatograph</td></tr><tr><td>7000 GC/MS Triple Quad</td><td>Agilent Tech.</td><td></td><td>Triple Quad mass spectrometer</td></tr><tr><td>7683B Series Injector</td><td>Agilent Tech.</td><td></td><td>Sample injector</td></tr><tr><td>Heraeus Multifuge 3SR&lt;sup&gt;+&lt;/sup&gt;</td><td>Thermo Scientific</td><td></td><td>Centrifuge with 10 ml tube rotor</td></tr></tbody></table>

fatty acid 13c isotopologue profiling provides insight into trophic carbon transfer and lipid metabolism of invertebrate consumers

Fatty acids (FAs) are useful biomarkers in food web ecology because they are typically assimilated as a complete molecule and transferred into consumer tissue with minor or no modification, allowing the dietary routing between different trophic levels. However, the FA trophic marker approach is still hampered by the limited knowledge in lipid metabolism of the soil fauna. This study used entirely labelled palmitic acid (13C16:0, 99 atom%) as a tracer in fatty acid metabolism pathways of two widespread soil Collembola, Protaphorura fimata and Heteromurus nitidus. In order to investigate the fate and metabolic modifications of this precursor, a method of isotopologue profiling is presented, performed by mass spectrometry using single ion monitoring. Moreover, the upstream laboratory feeding experiment is described, as well as the extraction and methylation of dominant lipid fractions (neutral lipids, phospholipids) and the related formula and calculations. Isotopologue profiling does not only yield the overall 13C enrichment in fatty acids derived from the 13C labeled precursor but also produces the pattern of isotopologues exceeding the mass of the parent ion (i.e., the FA molecular ion M+) of each labeled FA by one or more mass units (M+1, M+2, M+3, etc.). This knowledge allows conclusions on the ratio of dietary routing of an entirely consumed FA in comparison to de novo biosynthesis. The isotopologue profiling is suggested as a useful tool for evaluation of fatty acid metabolism in soil animals to disentangle trophic interactions.

Fresh weight and lipid content of Collembola 
In the course of the described experiment, the content in NLFAs and PLFAs did not change significantly over time, whereas the fresh weight of specimens increased slightly but not significantly24. Both parameters indicate a good level of physical fitness of the Collembola specimens. Be aware to investigate Collembola&#39;s fresh weight and lipid content throughout the experiment corresponding to the...

Watch this Scientific Journal Video about Fatty Acid 13C Isotopologue Profiling Provides Insight into Trophic Carbon Transfer and Lipid Metabolism of Invertebrate Consumers at JoVE.com

Fatty Acid 13C Isotopologue Profiling Provides Insight into Trophic Carbon Transfer and Lipid Metabolism of Invertebrate Consumers

The fatty acid trophic marker approach, i.e., the assimilation of fatty acids as entire molecule and transfer into consumer tissue with no or minor modification, is hampered by knowledge gaps in fatty acid metabolism of small soil invertebrates. Isotopologue profiling is provided as a valuable tool to disentangle trophic interactions.

Fatty Acid 13C Isotopologue Profiling Provides Insight into Trophic Carbon Transfer and Lipid Metabolism of Invertebrate Consumers

Fatty acids (FAs) are useful biomarkers in food web ecology because they are typically assimilated as a complete molecule and transferred into consumer ...

fatty-acid-13c-isotopologue-profiling-provides-insight-into-trophic

Research

JoVE Journal

Biochemistry

7.9K Views.  Humboldt-Universität zu Berlin. The fatty acid trophic marker approach, i.e., the assimilation of fatty acids as entire molecule and transfer into consumer tissue with no or minor modification, is hampered by knowledge gaps in fatty acid metabolism of small soil invertebrates. Isotopologue profiling is provided as a valuable tool to disentangle trophic interactions.

Video: Fatty Acid 13C Isotopologue Profiling Provides Insight into Trophic Carbon Transfer and Lipid Metabolism of Invertebrate Consumers

Profiling the Triacylglyceride Contents in Bat Integumentary Lipids by Preparative Thin Layer Chromatography and MALDI-TOF Mass Spectrometry

The mammalian integument includes sebaceous glands that secrete an oily material onto the skin surface. Sebum production is part of the innate immune system that is protective against pathogenic microbes. Abnormal sebum production and chemical composition are also a clinical symptom of specific skin diseases. Sebum contains a complex mixture of lipids, including triacylglycerides, which is species-specific. The broad chemical properties exhibited by diverse lipid classes hinder the specific determination of sebum composition. Analytical techniques for lipids typically require chemical derivatizations that are labor-intensive and increase sample preparation costs. This paper describes how to extract lipids from mammalian integument, separate broad lipid classes by thin-layer chromatography, and profile the triacylglyceride contents using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. This robust method enables a direct determination of the triacylglyceride profiles among species and individuals, and it can be readily applied to any taxonomic group of mammals.

Mammalian integument contains solvent-extractable lipids that can provide chemical compositions characteristic of individual species. This paper presents a routine method for separating broad lipid classes isolated from integumentary tissues using thin layer chromatography and determining the triacylglyceride profile by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

The mammalian integument includes sebaceous glands that secrete an oily material onto the skin surface. Sebum production is part of the innate immune ...

Chemistry

Extraction and Analysis of Microbial Phospholipid Fatty Acids in Soils

Phospholipid fatty acids (PLFAs) are key components of microbial cell membranes. The analysis of PLFAs extracted from soils can provide information about the overall structure of terrestrial microbial communities. PLFA profiling has been extensively used in a range of ecosystems as a biological index of overall soil quality, and as a quantitative indicator of soil response to land management and other environmental stressors.
The standard method presented here outlines four key steps: 1. lipid extraction from soil samples with a single-phase chloroform mixture, 2. fractionation using solid phase extraction columns to isolate phospholipids from other extracted lipids, 3. methanolysis of phospholipids to produce fatty acid methyl esters (FAMEs), and 4. FAME analysis by capillary gas chromatography using a flame ionization detector (GC-FID). Two standards are used, including 1,2-dinonadecanoyl-sn-glycero-3-phosphocholine (PC(19:0/19:0)) to assess the overall recovery of the extraction method, and methyl decanoate (MeC10:0) as an internal standard (ISTD) for the GC analysis.

Phospholipid fatty acids provide information about the structure of soil microbial communities. We present methods for extraction from soil samples with a single-phase chloroform mixture, fractionation of extracted lipids using solid phase extraction columns, and methanolysis to produce fatty acid methyl esters, which are analyzed by capillary gas chromatography.

Phospholipid fatty acids (PLFAs) are key components of microbial cell membranes. The analysis of PLFAs extracted from soils can provide information about ...

Environment

NMR Spectroscopy as a Robust Tool for the Rapid Evaluation of the Lipid Profile of Fish Oil Supplements

The western diet is poor in n-3 fatty acids, therefore the consumption of fish oil supplements is recommended to increase the intake of these essential nutrients. The objective of this work is to demonstrate the qualitative and quantitative analysis of encapsulated fish oil supplements using high-resolution 1H and 13C NMR spectroscopy utilizing two different NMR instruments; a 500 MHz and an 850 MHz instrument. Both proton (1H) and carbon (13C) NMR spectra can be used for the quantitative determination of the major constituents of fish oil supplements. Quantification of the lipids in fish oil supplements is achieved through integration of the appropriate NMR signals in the relevant 1D spectra. Results obtained by 1H and 13C NMR are in good agreement with each other, despite the difference in resolution and sensitivity between the two nuclei and the two instruments. 1H NMR offers a more rapid analysis compared to 13C NMR, as the spectrum can be recorded in less than 1 min, in contrast to 13C NMR analysis, which lasts from 10 min to one hour. The 13C NMR spectrum, however, is much more informative. It can provide quantitative data for a greater number of individual fatty acids and can be used for determining the positional distribution of fatty acids on the glycerol backbone. Both nuclei can provide quantitative information in just one experiment without the need of purification or separation steps. The strength of the magnetic field mostly affects the 1H NMR spectra due to its lower resolution with respect to 13C NMR, however, even lower cost NMR instruments can be efficiently applied as a standard method by the food industry and quality control laboratories.

Here, high-resolution 1H and 13C Nuclear Magnetic Resonance (NMR) spectroscopy was used as a rapid and reliable tool for quantitative and qualitative analysis of encapsulated fish oil supplements.

The western diet is poor in n-3 fatty acids, therefore the consumption of fish oil supplements is recommended to increase the intake of these essential ...

Determination of Total Lipid and Lipid Classes in Marine Samples

Lipids are largely composed of carbon and hydrogen and, therefore, provide a greater specific energy than other organic macromolecules in the sea. Being carbon- and hydrogen-rich they are also hydrophobic and can act as a solvent and absorption carrier for organic contaminants and thus can be drivers of pollutant bioaccumulation in marine ecosystems. Their hydrophobic nature facilitates their isolation from seawater or biological specimens: marine lipid analysis begins with sampling and then extraction in non-polar organic solvents, providing a convenient method for their separation from other substances in an aquatic matrix.
If seawater has been sampled, the first step usually involves separation into operationally defined &#39;dissolved&#39; and &#39;particulate&#39; factions by filtration. Samples are collected and lipids isolated from the sample matrix typically with chloroform for truly dissolved matter and colloids, and with mixtures of chloroform and methanol for solids and biological specimens. Such extracts may contain several classes from biogenic and anthropogenic sources. At this time, total lipids and lipid classes may be determined. Total lipid can be measured by summing individually determined lipid classes which customarily have been chromatographically separated. Thin-layer chromatography (TLC) with flame ionization detection (FID) is regularly used for the quantitative analysis of lipids from marine samples. TLC-FID furnishes synoptic lipid class information and, by summing classes, a total lipid measurement.
Lipid class information is especially useful when combined with measurements of individual components e.g., fatty acids and/or sterols, after their release from lipid extracts. The wide variety of lipid structures and functions means they are used broadly in ecological and biogeochemical research assessing ecosystem health and the degree of influence by anthropogenic impacts. They have been employed to measure substances of dietary value to marine fauna (e.g., aquafeeds and/or prey), and as an indicator of water quality (e.g., hydrocarbons).

This protocol is for the determination of lipids in seawater and biological specimens. Lipids in filtrates are extracted with chloroform or mixtures of chloroform and methanol in the case of solids. Lipid classes are measured by rod thin-layer chromatography with flame ionization detection and their sum gives the total lipid content.

Lipids are largely composed of carbon and hydrogen and, therefore, provide a greater specific energy than other organic macromolecules in the sea. Being ...

Stable Isotopic Profiling of Intermediary Metabolic Flux in Developing and Adult Stage Caenorhabditis elegans

Stable isotopic profiling has long permitted sensitive investigations of the metabolic consequences of genetic mutations and/or pharmacologic therapies in cellular and mammalian models. Here, we describe detailed methods to perform stable isotopic profiling of intermediary metabolism and metabolic flux in the nematode, Caenorhabditis elegans. Methods are described for profiling whole worm free amino acids, labeled carbon dioxide, labeled organic acids, and labeled amino acids in animals exposed to stable isotopes either from early development on nematode growth media agar plates or beginning as young adults while exposed to various pharmacologic treatments in liquid culture. Free amino acids are quantified by high performance liquid chromatography (HPLC) in whole worm aliquots extracted in 4% perchloric acid. Universally labeled 13C-glucose or 1,6-13C2-glucose is utilized as the stable isotopic precursor whose labeled carbon is traced by mass spectrometry in carbon dioxide (both atmospheric and dissolved) as well as in metabolites indicative of flux through glycolysis, pyruvate metabolism, and the tricarboxylic acid cycle. Representative results are included to demonstrate effects of isotope exposure time, various bacterial clearing protocols, and alternative worm disruption methods in wild-type nematodes, as well as the relative extent of isotopic incorporation in mitochondrial complex III mutant worms (isp-1(qm150)) relative to wild-type worms. Application of stable isotopic profiling in living nematodes provides a novel capacity to investigate at the whole animal level real-time metabolic alterations that are caused by individual genetic disorders and/or pharmacologic therapies.

Stable Isotopic Profiling of Intermediary Metabolic Flux in Developing and Adult Stage Caenorhabditis elegans

Stable isotopic profiling by gas chromatography mass spectrometric analysis of intermediary metabolic flux is described in the nematode, Caenorhabditis elegans. Methods are detailed for assessing isotopic enrichment in carbon dioxide, organic acids, and amino acids following isotope exposure either during development on agar plates or during adulthood in liquid culture.

Stable isotopic profiling has long permitted sensitive investigations of the metabolic consequences of genetic mutations and/or pharmacologic therapies in ...

Biology

Screening Lipid Structures Using Stable Isotope Labeling

Tracing de novo Lipids using Stable Isotope Labeling LC-TIMS-TOF MS/MS

Lipids are highly diverse, and small changes in lipid structures and composition can have profound effects on critical biological functions. Stable isotope labeling (SIL) offers several advantages for the study of lipid distribution, mobilization, and metabolism, as well as de novo lipid synthesis. The successful implementation of the SIL technique requires the removal of interferences from endogenous molecules. In the present work, we describe a high-throughput analytical protocol for the screening of SIL lipids from biological samples; examples will be shown of lipid de novo identification during mosquito ovary development. The use of complementary liquid chromatography trapped ion mobility spectrometry and mass spectrometry allows for the separation and lipids assignment from a single sample in a single scan (&lt;1 h). The described approach takes advantage of recent developments in data-dependent acquisition and data-independent acquisition, using parallel accumulation in the mobility trap followed by sequential fragmentation and collision-induced dissociation. The measurement of SIL at the fatty acid chain level reveals changes in lipid dynamics during the ovary development of mosquitoes. The lipids de novo structures are confidently assigned based on their retention time, mobility, and fragmentation pattern.

Author Spotlight: Quantification of Complex Lipidomic Samples Using Stable Isotope Labeling

Presented here is a method for screening lipid structures through stable isotope labeling by using their retention time, mobility, and fragmentation.

Lipids are highly diverse, and small changes in lipid structures and composition can have profound effects on critical biological functions. Stable ...

Metabolic Pathway Confirmation and Discovery Through 13C-labeling of Proteinogenic Amino Acids

Microbes have complex metabolic pathways that can be investigated using biochemistry and functional genomics methods. One important technique to examine cell central metabolism and discover new enzymes is 13C-assisted metabolism analysis 1. This technique is based on isotopic labeling, whereby microbes are fed with a 13C labeled substrates. By tracing the atom transition paths between metabolites in the biochemical network, we can determine functional pathways and discover new enzymes. 
As a complementary method to transcriptomics and proteomics, approaches for isotopomer-assisted analysis of metabolic pathways contain three major steps 2. First, we grow cells with 13C labeled substrates. In this step, the composition of the medium and the selection of labeled substrates are two key factors. To avoid measurement noises from non-labeled carbon in nutrient supplements, a minimal medium with a sole carbon source is required. Further, the choice of a labeled substrate is based on how effectively it will elucidate the pathway being analyzed. Because novel enzymes often involve different reaction stereochemistry or intermediate products, in general, singly labeled carbon substrates are more informative for detection of novel pathways than uniformly labeled ones for detection of novel pathways3, 4. Second, we analyze amino acid labeling patterns using GC-MS. Amino acids are abundant in protein and thus can be obtained from biomass hydrolysis. Amino acids can be derivatized by N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (TBDMS) before GC separation. TBDMS derivatized amino acids can be fragmented by MS and result in different arrays of fragments. Based on the mass to charge (m/z) ratio of fragmented and unfragmented amino acids, we can deduce the possible labeled patterns of the central metabolites that are precursors of the amino acids. Third, we trace 13C carbon transitions in the proposed pathways and, based on the isotopomer data, confirm whether these pathways are active 2. Measurement of amino acids provides isotopic labeling information about eight crucial precursor metabolites in the central metabolism. These metabolic key nodes can reflect the functions of associated central pathways.
13C-assisted metabolism analysis via proteinogenic amino acids can be widely used for functional characterization of poorly-characterized microbial metabolism1. In this protocol, we will use Cyanothece 51142 as the model strain to demonstrate the use of labeled carbon substrates for discovering new enzymatic functions.

Metabolic Pathway Confirmation and Discovery Through 13C-labeling of Proteinogenic Amino Acids

13C-isotope labeling is a useful technique for determining the cell central metabolism for various types of microorganisms. After cells have been cultured with a specific labeled substrate, GC-MS measurement can reveal functional metabolic pathways based on unique labeling patterns in proteinogenic amino acids.

Microbes have complex metabolic pathways that can be investigated using biochemistry and functional genomics methods. One important technique to examine ...

Biochemical and High Throughput Microscopic Assessment of Fat Mass in Caenorhabditis Elegans

The nematode C. elegans has emerged as an important model for the study of conserved genetic pathways regulating fat metabolism as it relates to human obesity and its associated pathologies. Several previous methodologies developed for the visualization of C. elegans triglyceride-rich fat stores have proven to be erroneous, highlighting cellular compartments other than lipid droplets. Other methods require specialized equipment, are time-consuming, or yield inconsistent results. We introduce a rapid, reproducible, fixative-based Nile red staining method for the accurate and rapid detection of neutral lipid droplets in C. elegans. A short fixation step in 40% isopropanol makes animals completely permeable to Nile red, which is then used to stain animals. Spectral properties of this lipophilic dye allow it to strongly and selectively fluoresce in the yellow-green spectrum only when in a lipid-rich environment, but not in more polar environments. Thus, lipid droplets can be visualized on a fluorescent microscope equipped with simple GFP imaging capability after only a brief Nile red staining step in isopropanol. The speed, affordability, and reproducibility of this protocol make it ideally suited for high throughput screens. We also demonstrate a paired method for the biochemical determination of triglycerides and phospholipids using gas chromatography mass-spectrometry. This more rigorous protocol should be used as confirmation of results obtained from the Nile red microscopic lipid determination. We anticipate that these techniques will become new standards in the field of C. elegans metabolic research.

Biochemical and High Throughput Microscopic Assessment of Fat Mass in Caenorhabditis Elegans

We present robust biochemical and microscopic methods for studying Caenorhabditis elegans lipid stores. A rapid, simple, fixing-staining procedure for fluorescent lipid droplet imaging leverages the spectral properties of the lipophilic dye Nile red. We then present biochemical measurement of triglycerides and phospholipids using solid phase extraction and gas chromatography-mass spectrometry.

The nematode C. elegans has emerged as an important  model for the study of conserved genetic pathways regulating fat metabolism as  it relates to human ...

High-fat Feeding Paradigm for Larval Zebrafish: Feeding, Live Imaging, and Quantification of Food Intake

Zebrafish are emerging as a model of dietary lipid processing and metabolic disease. This protocol describes how to feed larval zebrafish a lipid-rich meal, which consists of an emulsion of chicken egg yolk liposomes created by sonicating egg yolk in embryo media. Detailed instructions are provided to screen larvae for egg yolk consumption so that larvae that fail to feed will not confound experimental results. The chicken egg yolk liposomes can be spiked with fluorescent lipid analogs, including fatty acids and cholesterol, enabling both systemic and subcellular visualization of dietary lipid processing. Several methods are described to mount larvae that are conducive to short- and long-term live imaging with both upright and inverted objectives at high and low magnification. Additionally presented is an assay to quantify larval food intake by extracting the lipids of larvae fed fluorescent lipid analogs, spotting the lipids on a thin layer chromatography plate, and quantifying the fluorescence. Finally, critical aspects of the procedures, important controls, options for modifying the protocols to address specific experimental questions, and potential limitations are discussed. These techniques can be applied not only to focused, hypothesis driven inquiries, but also to a variety of screens and live imaging techniques to study dietary lipid metabolism and the control of food intake.

Zebrafish are emerging as a valuable model of dietary lipid processing and metabolic disease. Described are protocols of lipid-rich larval feeds, live imaging of dietary fluorescent lipid analogs, and quantification of food intake. These techniques can be applied to a variety of screening, imaging, and hypothesis driven inquiry techniques.

Zebrafish are emerging as a model of dietary lipid processing and metabolic disease. This protocol describes how to feed larval zebrafish a lipid-rich ...

Laboratory Protocol for Genetic Gut Content Analyses of Aquatic Macroinvertebrates Using Group-specific rDNA Primers

Analyzing food webs is essential for a better understanding of ecosystems. For example, food web interactions can undergo severe changes caused by the invasion of non-indigenous species. However, an exact identification of field predator-prey interactions is difficult in many cases. These analyses are often based on a visual evaluation of gut content or the analysis of stable isotope ratios (&#948;15N and &#948;13C). Such methods require comprehensive knowledge about, respectively, morphologic diversity or isotopic signature from individual prey organisms, leading to obstacles in the exact identification of prey organisms. Visual gut content analyses especially underestimate soft bodied prey organisms, because maceration, ingestion and digestion of prey organisms make identification of specific species difficult. Hence, polymerase chain reaction (PCR) based strategies, for example the use of group-specific primer sets, provide a powerful tool for the investigation of food web interactions. Here, we describe detailed protocols to investigate the gut contents of macroinvertebrate consumers from the field using group-specific primer sets for nuclear ribosomal deoxyribonucleic acid (rDNA). DNA can be extracted either from whole specimens (in the case of small taxa) or out of gut contents of specimens collected in the field. Presence and functional efficiency of the DNA templates need to be confirmed directly from the tested individual using universal primer sets targeting the respective subunit of DNA. We also demonstrate that consumed prey can be determined further down to species level via PCR with unmodified group-specific primers combined with subsequent single strand conformation polymorphism (SSCP) analyses using polyacrylamide gels. Furthermore, we show that the use of different fluorescent dyes as labels enables parallel screening for DNA fragments of different prey groups from multiple gut content samples via automated fragment analysis.

Most common gut content analyses of macroinvertebrates are visual. Requiring intense knowledge about morphological diversity of prey organisms, they miss soft bodied prey and, due to strong comminution of prey, are nearly impossible for some organisms, including amphipods. We provide detailed, novel genetic approaches for macroinvertebrate prey identification in the diet of amphipods.

Analyzing food webs is essential for a better understanding of ecosystems. For example, food web interactions can undergo severe changes caused by the ...

Fatty Acid ¹³C Isotopologue Profiling Provides Insight into Trophic Carbon Transfer and Lipid Metabolism of Invertebrate Consumers

Podsumowanie

Przeglądaj więcej filmów

Rozdziały w tym wideo

Profiling the Triacylglyceride Contents in Bat Integumentary Lipids by Preparative Thin Layer Chromatography and MALDI-TOF Mass Spectrometry

Extraction and Analysis of Microbial Phospholipid Fatty Acids in Soils

NMR Spectroscopy as a Robust Tool for the Rapid Evaluation of the Lipid Profile of Fish Oil Supplements

Determination of Total Lipid and Lipid Classes in Marine Samples

Stable Isotopic Profiling of Intermediary Metabolic Flux in Developing and Adult Stage Caenorhabditis elegans

Tracing de novo Lipids using Stable Isotope Labeling LC-TIMS-TOF MS/MS

Metabolic Pathway Confirmation and Discovery Through ¹³C-labeling of Proteinogenic Amino Acids

Biochemical and High Throughput Microscopic Assessment of Fat Mass in Caenorhabditis Elegans

High-fat Feeding Paradigm for Larval Zebrafish: Feeding, Live Imaging, and Quantification of Food Intake

Laboratory Protocol for Genetic Gut Content Analyses of Aquatic Macroinvertebrates Using Group-specific rDNA Primers