Services and support of the research project were provided by the VCU Massey Cancer Center Tissue and Data Acquisition and Analysis Core and the VCU Lipidomics and Metabolomics Core, which are supported in part with funding from NIH-NCI Cancer Center Support Grant P30CA016059. This work was supported by National Institutes of Health Grants R21CA232234 (Santiago Lima).

De-identified human lung tissues were obtained from the Virginia Commonwealth University (VCU) Tissue and Data Acquisition and Analysis Core under an internal review board (IRB) approved protocol (#HM2471). The use of mice for research and harvesting of mice tissues was approved by the VCU institutional animal care and use committee (IACUC).
1. Preparation of materials
NOTE: These steps should be performed a day prior to the tissue washing.
<ol>
	<li>Pre-label and...

<ol>
	<li>Maceyka, M., Spiegel, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sphingolipid+metabolites+in+inflammatory+disease.">Sphingolipid metabolites in inflammatory disease.</a> Nature. 510, 58-67 (2014).</li><li>Ogretmen, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sphingolipid+metabolism+in+cancer+signalling+and+therapy.">Sphingolipid metabolism in cancer signalling and therapy.</a> Nature Reviews. Cancer. 18 (1), 33-50 (2018).</li><li>Hannun, Y. A., Obeid, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sphingolipids+and+their+metabolism+in+physiology+and+disease.">Sphingolipids and their metabolism in physiology and disease.</a> Nature Reviews Molecular Cell Biology. 19 (3), 175-191 (2018).</li><li>Hla, T., Dannenberg, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sphingolipid+signaling+in+metabolic+disorders.">Sphingolipid signaling in metabolic disorders.</a> Cell Metabolism. 16 (4), 420-434 (2012).</li><li>Lima, S., Milstien, S., Spiegel, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sphingosine+and+Sphingosine+Kinase+1+involvement+in+endocytic+membrane+Trafficking.">Sphingosine and Sphingosine Kinase 1 involvement in endocytic membrane Trafficking.</a> The Journal of Biological Chemistry. 292 (8), 3074-3088 (2017).</li><li>Lima, S., 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=TP53+is+required+for+BECN1-+and+ATG5-dependent+cell+death+induced+by+sphingosine+kinase+1+inhibition.">TP53 is required for BECN1- and ATG5-dependent cell death induced by sphingosine kinase 1 inhibition.</a> Autophagy. , 1-50 (2018).</li><li>Young, M. M., 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=Sphingosine+Kinase+1+cooperates+with+autophagy+to+maintain+endocytic+membrane+trafficking.">Sphingosine Kinase 1 cooperates with autophagy to maintain endocytic membrane trafficking.</a> Cell Reports. 17 (6), 1532-1545 (2016).</li><li>Young, M. M., Wang, H. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sphingolipids+as+regulators+of+autophagy+and+endocytic+trafficking.">Sphingolipids as regulators of autophagy and endocytic trafficking.</a> Advances in Cancer Research. 140, 27-60 (2018).</li><li>Shen, H., 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=Coupling+between+endocytosis+and+sphingosine+kinase+1+recruitment.">Coupling between endocytosis and sphingosine kinase 1 recruitment.</a> Nature Cell Biology. 16 (7), 652-662 (2014).</li><li>Morad, S. A. F., Cabot, M. C., Chalfant, C. E., Fisher, P. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Advances in Cancer Research. 140, 235-263 (2018).</li><li>Rohrbach, T. 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=A+simple+method+for+sphingolipid+analysis+of+tissues+embedded+in+optimal+cutting+temperature+compound.">A simple method for sphingolipid analysis of tissues embedded in optimal cutting temperature compound.</a> Journal of Lipid Research. 61 (6), 953-967 (2020).</li><li>Weston, L. A., Hummon, A. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+LC-MS/MS+analysis+of+optimal+cutting+temperature+(OCT)+compound+removal+for+the+study+of+mammalian+proteomes.">Comparative LC-MS/MS analysis of optimal cutting temperature (OCT) compound removal for the study of mammalian proteomes.</a> Analyst. 138 (21), 6380-6384 (2013).</li><li>Holfeld, A., Vald&#233;s, A., Malmstr&#246;m, P. -. U., Segersten, U., Lind, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Parallel+proteomic+workflow+for+mass+spectrometric+analysis+of+tissue+samples+preserved+by+different+methods.">Parallel proteomic workflow for mass spectrometric analysis of tissue samples preserved by different methods.</a> Analytical Chemistry. 90 (9), 5841-5849 (2018).</li><li>Zhang, W., Sakashita, S., Taylor, P., Tsao, M. S., Moran, M. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comprehensive+proteome+analysis+of+fresh+frozen+and+optimal+cutting+temperature+(OCT)+embedded+primary+non-small+cell+lung+carcinoma+by+LC-MS/MS.">Comprehensive proteome analysis of fresh frozen and optimal cutting temperature (OCT) embedded primary non-small cell lung carcinoma by LC-MS/MS.</a> Methods. 81, 50-55 (2015).</li><li>Shah, P., 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=Tissue+proteomics+using+chemical+immobilization+and+mass+spectrometry.">Tissue proteomics using chemical immobilization and mass spectrometry.</a> Analytical Biochemistry. 469, 27-33 (2015).</li></ol>

OCT is a common long-term cryo-preservation agent used in biorepositories. However, OCT can result in ion suppression when tissues are analyzed by various mass spectrometry platforms12,13,14,15, or result in loss of signal when samples are analyzed by LC-ESI-MS/MS11. OCT in cryopreserved tissues can also interfere with tissue normalization methods such as weighing and pr...

Sphingolipids are bioactive metabolites known for their roles in human metabolism and disease1,2. They regulate complex cellular processes such as cell migration, cell survival and death, cell movement, vesicular trafficking, cellular invasion and metastasis, angiogenesis, and the production of cytokines1,2,3,4,5,6,7,8,9. Defects in the regulation of sphingolipid metabolism contribute to the initiation and progression of cancers, determine how aggressive cancers are, and how cancers respond to and develop resistance to therapy3,10. Therefore, because of these broad impacts on the etiology of disease, analytical methods that can precisely establish disease-specific sphingolipid alterations are important tools. Mass spectrometry (MS) is the most accurate and reliable method to analyze sphingolipid alterations.
Human specimens that can be used for the analysis of sphingolipid alterations can be obtained prospectively from the surgical suite or retrospectively from tissue biorepositories. Fresh tissues from surgery are advantageous because they can be directly analyzed by MS or other analytical methods. However, acquiring tissues prospectively has administrative, technical, and logistical hurdles, and collecting sufficient specimens to reach statistical power can be challenging. Obtaining tissues from biorepositories is advantageous because they can be acquired retrospectively, in large numbers, and biorepositories confirm histology and pathology, use standard operating procedures to cryogenically preserve and store tissues, and can provide clinicopathological data that can be used for correlation analyses. However, to preserve molecular and structural features, biorepositories may cryopreserve tissues by embedding them in optimal cutting temperature (OCT) compound, which we have shown interferes with data normalization assays and the quantification of sphingolipids by liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS)11. It has also been shown that polyvinyl alcohol and polyethylene glycol, the primary components in OCT compound, result in ion suppression in other MS analysis platforms12,13,14,15. Therefore, OCT compound must be removed from tissues prior to sphingolipidomic analysis by MS.
In a previous report, we have validated a protocol for the removal of OCT compound from human specimens for LC-ESI-MS/MS analysis11 and the methodology used for weighing tissues for data normalization11. Here, we detail the steps of the sphingolipidomic OCT compound-removal protocol (sOCTrP) and show representative data from human lung adenocarcinoma tumors and normal adjacent uninvolved tissues.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1 mL polypropylene pipette tips</td>
			<td>NA</td>
			<td>NA</td>
			<td>Used to retrieve specimens</td>
		</tr>
		<tr>
			<td>1.5 mL polypropylene centrifuge tubes</td>
			<td>NA</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>10 mL Erlenmeyer flask</td>
			<td>VWR</td>
			<td>89091-116</td>
			<td>Used for tube and tissue weighing</td>
		</tr>
		<tr>
			<td>AB Sciex Analyst 1.6.2</td>
			<td>Sciex</td>
			<td>NA</td>
			<td>Software to analyze and integrate MS data</td>
		</tr>
		<tr>
			<td>Ammonium formate</td>
			<td>Fisher Scientific</td>
			<td>A11550</td>
			<td>For LC mobile phases</td>
		</tr>
		<tr>
			<td>Analytical scale</td>
			<td>NA</td>
			<td>NA</td>
			<td>Scale that is accurate to 0.1 mg</td>
		</tr>
		<tr>
			<td>Bottle top dispenser</td>
			<td>Sartorius</td>
			<td>LH-723071</td>
			<td>Used for dispensing solvents</td>
		</tr>
		<tr>
			<td>C12-Ceramide (d18:1/C12:0); N-(dodecanoyl)-sphing-4-enine</td>
			<td>Avanti Polar Lipids</td>
			<td>LM2212</td>
			<td>Internal standard</td>
		</tr>
		<tr>
			<td>C12-glucosylceramide (d18:1/12:0); N-(dodecanoyl)-1-&#946;-glucosyl-sphing-4-eine</td>
			<td>Avanti Polar Lipids</td>
			<td>LM2511</td>
			<td>Internal standard</td>
		</tr>
		<tr>
			<td>C12-lactosylceramide (d18:1/12:0); N-(dodecanoyl)-1-&#223;-lactosyl-sphing-4-ene</td>
			<td>Avanti Polar Lipids</td>
			<td>LM2512</td>
			<td>Internal standard</td>
		</tr>
		<tr>
			<td>C12-Sphingomyelin&#160; (d18:1/C12:0), N-(dodecanoyl)-sphing-4-enine-1-phosphocholine</td>
			<td>Avanti Polar Lipids</td>
			<td>LM2312</td>
			<td>Internal standard</td>
		</tr>
		<tr>
			<td>CHLOROFORM OMNISOLV 4L</td>
			<td>VWR</td>
			<td>EM-CX1054-1</td>
			<td></td>
		</tr>
		<tr>
			<td>ClickSeal Biocontainment Lids</td>
			<td>Thermo Scientific</td>
			<td>75007309</td>
			<td>To prevent biohazard aeresols during centrifugation</td>
		</tr>
		<tr>
			<td>Conflikt</td>
			<td>Decon Labs</td>
			<td>4101</td>
			<td>Decontaminant</td>
		</tr>
		<tr>
			<td>CTO-20A/20AC Column Oven</td>
			<td>Shimadzu</td>
			<td>NA</td>
			<td>For LC</td>
		</tr>
		<tr>
			<td>d17:1-Sphingosine;&#160; (2S,3R,4E)-2-aminoheptadec-4-ene-1,3-diol</td>
			<td>Avanti Polar Lipids</td>
			<td>LM2000</td>
			<td>Internal standard</td>
		</tr>
		<tr>
			<td>d17:1-Sphingosine-1-phosphate; heptadecasphing-4-enine-1-phosphate</td>
			<td>Avanti Polar Lipids</td>
			<td>LM2144</td>
			<td>Internal standard</td>
		</tr>
		<tr>
			<td>DGU20A5R degasser</td>
			<td>Shimadzu</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Disposable Culture Tubes 13x100mm</td>
			<td>VWR</td>
			<td>53283-800</td>
			<td>13x100 mm screw top tubes</td>
		</tr>
		<tr>
			<td>Heated water bath</td>
			<td>NA</td>
			<td>NA</td>
			<td>For overnight lipid extraction</td>
		</tr>
		<tr>
			<td>Homogenizer 150</td>
			<td>Fisher Scientific</td>
			<td>15-340-167</td>
			<td>triturate tissues</td>
		</tr>
		<tr>
			<td>Homogenizer Plastic Disposable Generator Probe</td>
			<td>Fisher Scientific</td>
			<td>15-340-177</td>
			<td>for homogenization</td>
		</tr>
		<tr>
			<td>Kimwipes</td>
			<td>Kimtech</td>
			<td>34120</td>
			<td>Laboratory grade tissue used to make wicks</td>
		</tr>
		<tr>
			<td>Methanol LC-MS Grade 4L</td>
			<td>VWR</td>
			<td>EM-MX0486-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Nexera LC-30 AD binary pump system</td>
			<td>Shimadzu</td>
			<td>NA</td>
			<td>For LC-MS</td>
		</tr>
		<tr>
			<td>Permanent marker</td>
			<td>VWR</td>
			<td>52877-310</td>
			<td></td>
		</tr>
		<tr>
			<td>Phenolic Screw Thread Closure, Kimble Chase (caps for disposable culture tubes)</td>
			<td>VWR</td>
			<td>89001-502</td>
			<td>13x100 mm screw top tube caps</td>
		</tr>
		<tr>
			<td>Phosphate bufffered saline</td>
			<td>Thermo Scientific</td>
			<td>10010023</td>
			<td>To retrieve specimens from tubes after washing</td>
		</tr>
		<tr>
			<td>Repeater pipette</td>
			<td>Eppendorf</td>
			<td>4987000118</td>
			<td>To dispense LC-MS internal standards</td>
		</tr>
		<tr>
			<td>Screw Caps, Blue, Red PTFE/White Silicone</td>
			<td>VWR</td>
			<td>89239-020</td>
			<td>Autoinjector vial caps</td>
		</tr>
		<tr>
			<td>Screw Thread Glass Vials with ID Patch</td>
			<td>VWR</td>
			<td>46610-724</td>
			<td>Autoinjector vials</td>
		</tr>
		<tr>
			<td>SIL-30AC autoinjector</td>
			<td>Shimadzu</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>SpeedVac</td>
			<td>Thermo Scientific</td>
			<td>SPD2030P1220</td>
			<td>For drying solvents</td>
		</tr>
		<tr>
			<td>Supelco 2.1 (i.d.) x 50 mm Ascentis Express C18 column</td>
			<td>Sigma Aldrich</td>
			<td>53822-U</td>
			<td>For LC-MS</td>
		</tr>
		<tr>
			<td>Triple Quad 5500+ LC-MS/MS System</td>
			<td>Sciex</td>
			<td>NA</td>
			<td>For LC-ESI-MS/MS</td>
		</tr>
		<tr>
			<td>Ultrasonic water bath</td>
			<td>Branson</td>
			<td>Model 2800</td>
			<td>for homogenization and resuspension of extracted and dried lipids</td>
		</tr>
		<tr>
			<td>Vortexer</td>
			<td>NA</td>
			<td>NA</td>
			<td>For sOCTrP and resuspending dried lipids</td>
		</tr>
		<tr>
			<td>VWR Culture Tubes Disposable Borosilicate Glass</td>
			<td>VWR</td>
			<td>47729572</td>
			<td>13x100 glass culture tubes</td>
		</tr>
		<tr>
			<td>Water Hipersolve Chromanorm LC-MS</td>
			<td>VWR</td>
			<td>BDH83645.400</td>
			<td></td>
		</tr>
	</tbody>
</table>

preparation of human tissues embedded in optimal cutting temperature compound for mass spectrometry analysis

Sphingolipids are cellular components that have well-established roles in human metabolism and disease. Mass spectrometry can be used to determine whether sphingolipids are altered in a disease and investigate whether sphingolipids can be targeted clinically. However, properly powered prospective studies that acquire tissues directly from the surgical suite can be time consuming, and technically, logistically, and administratively challenging. In contrast, retrospective studies can take advantage of cryopreserved human specimens already available, usually in large numbers, at tissue biorepositories. Other advantages of procuring tissues from biorepositories include access to information associated with the tissue specimens including histology, pathology, and in some instances clinicopathological variables, all of which can be used to examine correlations with lipidomics data. However, technical limitations related to the incompatibility of optimal cutting temperature compound (OCT) used in the cryopreservation and mass spectrometry is a technical barrier for the analysis of lipids. However, we have previously shown that OCT can be easily removed from human biorepository specimens through cycles of washes and centrifugation without altering their sphingolipid content. We have also previously established that sphingolipids in human tissues cryopreserved in OCT are stable for up to 16 years. In this report, we outline the steps and workflow to analyze sphingolipids in human tissue specimens that are embedded in OCT, including washing tissues, weighing tissues for data normalization, the extraction of lipids, preparation of samples for analysis by liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS), mass spectrometry data integration, data normalization, and data analysis.

In this protocol, we describe in detail a method to remove OCT from cryo-preserved human tissues and weigh the tissues for analysis by LC-ESI-MS/MS. The materials required for this procedure are listed in Table of Materials. Shown in Figure 1 are results of a typical experiment where 10 human lung adenocarcinoma tumors and 10 normal adjacent tissues were washed to remove OCT and analyzed by LC-ESI-MS/MS. Importantly, as we have previously shown11, the...

Watch this Scientific Journal Video about Preparation of Human Tissues Embedded in Optimal Cutting Temperature Compound for Mass Spectrometry Analysis at JoVE.com

Preparation of Human Tissues Embedded in Optimal Cutting Temperature Compound for Mass Spectrometry Analysis

Sphingolipids are bioactive metabolites with well-established roles in human disease. Characterizing alterations in tissues with mass-spectrometry can reveal roles in disease etiology or identify therapeutic targets. However, the OCT-compound used for cryopreservation in biorepositories interferes with mass-spectrometry. We outline methods to analyze sphingolipids in human tissues embedded in OCT with LC-ESI-MS/MS.

Sphingolipids are cellular components that have well-established roles in human metabolism and disease. Mass spectrometry can be used to determine whether ...

OCT is a cryo-preservation agent that is incompatible with mass spectrometry analysis. Using this protocol, researchers can remove OCT from tissues and quantify sphingolipids with tandem liquid chromatography mass spectrometry. The preparation of tissue drying wicks, tissue washing, and tissue weighing will be demonstrated by April Boyd from Virginia Commonwealth University, and the lipid extraction will be demonstrated by Dr.Jeremy Allegood, director of the Virginia Commonwealth Metabolomics and Lipidomics Core.To begin, clean surgical scissors by immersing them in methanol for five minutes, followed by wiping them with a clean laboratory grade tissue. Using powder-free gloves, twirl the end of a laboratory grade tissue to create a finely tapered 30 to 40 millimeter long wick. Then using the methanol cleaned scissors, cut the wick at the thick end and place it in a clean cardboard box.Next, using the methanol cleaned scissors, cut four to five millimeters off the tip of a one milliliter pipette tip and place the tip back in the tip holder. To wash away the OCT from the tissues, add 10 milliliters of ice cold ultrapure deionized water to each tube containing human lung tissue and cap them tightly. Allow the tubes to incubate for 10 minutes.Vigorously vortex each tube until all the tissue deposited on the walls of the tube or the tissue pellet is completely resuspended. Then centrifuge the tubes in a pre-chilled swinging bucket centrifuge at 4, 000 to 5, 000 times G for 10 minutes at four degrees Celsius. Once the centrifugation is complete, uncap the tubes on ice.Carefully aspirate the wash solution, leaving approximately 0.5 milliliters of the supernatant in the tube, then recap the tube. After removing the supernatant from all tubes, wash the tissues twice more in the same manner. After the three OCT removal washes, use the prepared shortened pipette tip to add 500 microliters of ice cold PBS to the tube.Using the same tip, gently resuspend the pellet and transfer all of the resuspended tissue into a pre-labeled and pre-weighed 1.5 milliliter centrifuge tube. Keep the tube on ice until all the tissue samples are transferred. Pellet the tissues by centrifuging the tubes in a pre-chilled centrifuge, then carefully aspirate as much of the PBS as possible without disturbing the pellet and place the tubes back on ice.Using the tissue drying wicks prepared earlier, gently remove any remaining wash solution, then close the tube and place it on ice. To weigh the tubes, place one tube at a time in a recently calibrated tared and zeroed analytical balance and close the chamber door. Once the weight has stabilized, record it in an electronic spreadsheet.After weighing, place the tube back on ice and add 300 microliters of ice cold PBS. Using a shortened pipette tip, carefully transfer all tissue into two milliliters of ice cold methanol in a pre-labeled screw top glass tube. Before lipid extraction, allow the tissues and mass spectrometry internal lipid standards to equilibrate to room temperature for 20 minutes, then vortex and immerse the internal standard solutions in an ultrasonic water bath until the lipid standards have fully dissolved.Using a repeating pipette, add 250 picomoles of the internal mass spectrometry standards to each tube and lightly recap the tubes. To facilitate homogenization, adjust the volume of methanol to two milliliters, then triturate the tissue using a homogenizer by moving the homogenizer tip in a circular motion gently pressed against the tube wall. When clumps are no longer visible, recap the tube.Immerse the tube at a 45 degree angle in an ultrasonic water bath for 5 to 10 seconds. Then under a fume hood, add chloroform and methanol to each tube to achieve a methanol to chloroform to water ratio of two to one to 0.1. Seal the tubes tightly and leave them on the benchtop until the end of the day.Before leaving that evening, place the tightly capped tubes in a 48 degree Celsius water bath for an overnight incubation. On the following day, pellet any solvent and soluble debris by centrifugation. Then in a fume hood, carefully decant the supernatant into pre-labeled 13 into 100 millimeter borosilicate glass test tubes tilted at a 30 to 45 degree angle to facilitate the decanting.After decanting the supernatant from all tubes, use a vacuum concentrator at maximum vacuum with an initial one-hour heating step at 40 degrees Celsius to evaporate all solvent, then add 500 microliters of methanol to each tube. To resuspend the dried lipid extracts, vortex the tube for 5 to 10 seconds, then immerse the tube in an ultrasonic water bath at a 45 degree angle with rotation for two minutes. Re-vortex the tube for five seconds and re-immerse in the ultrasonic water bath for an additional minute.Remove any insoluble debris by centrifugation, then decant the supernatant into a pre-labeled autoinjector vial tilted at a 30 to 45 degree angle to facilitate the decanting. Cap the vials tightly before storing them at minus 80 degrees Celsius until analysis. Liquid chromatography electrospray ionization tandem mass spectrometry analysis following OCT removal confirms that various chain-length species of ceramides and monohexosyl-ceramides are significantly elevated in human lung adenocarcinoma tumors compared to normal adjacent uninvolved tissues.Sphingolipid standards elute sequentially in the following order:d17:1 sphingosine, d17:1 sphingosine-1-phosphate, C12 lactosyl-ceramide, C12 monohexosyl-ceramide, C12 sphingomyelin, and C12 ceramide. For each of these sphingolipid species, using the gradient and instrumentation settings in the text, there is an approximate positive 0.15 minute shift in the retention time for every two carbon increase in chain-length. However, longer chain-length lipids such as C24 and C26 may have larger retention time shifts.Furthermore, a double bond in the fatty acid often results in a negative 0.15 minute shift in retention time. Thus, C18:1 ceramide will have a retention time similar to C16 ceramide. Rather than relying almost exclusively on freshly collected tissues, this protocol expands the tissue sources that can be used for mass spectrometry analysis to include those cryogenically stored at biorepositories.

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1.9K vistas.  Virginia Commonwealth University. La OCT es un agente de criopreservación incompatible con el análisis por espectrometría de masas. Usando este protocolo, los investigadores pueden eliminar la OCT de los tejidos y cuantificar los esfingolípidos con espectrometría de masas de cromatografía líquida en tándem. La preparación de mechas de secado de tejidos, lavado de tejidos y pesaje de tejidos será demostrada por April Boyd de Virginia Commonwealth University, y la extracción de lípidos será demostrada por el Dr. Je...