Tyge Greibrokk

• Ambaw, Yohannes Abere; Dahl, Sandra Rinne; Chen, Yan; Greibrokk, Tyge; Lundanes, Elsa & Lazraq, Issam [Show all 11 contributors for this article] (2021). Tailored polymer-based selective extraction of lipid mediators from biological samples. Metabolites. ISSN 2218-1989. 11(8), p. 1–14. doi: 10.3390/metabo11080539. Full text in Research Archive Show summary

  Lipid mediators, small molecules involved in regulating inflammation and its resolution, are a class of lipids of wide interest as their levels in blood and tissues may be used to monitor health and disease states or the effect of new treatments. These molecules are present at low levels in biological samples, and an enrichment step is often needed for their detection. We describe a rapid and selective method that uses new low-cost molecularly imprinted (MIP) and non-imprinted (NIP) polymeric sorbents for the extraction of lipid mediators from plasma and tissue samples. The extraction process was carried out in solid-phase extraction (SPE) cartridges, manually packed with the sorbents. After extraction, lipid mediators were quantified by liquid chromatography–tandem mass spectrometry (LC–MSMS). Various parameters affecting the extraction efficiency were evaluated to achieve optimal recovery and to reduce non-specific interactions. Preliminary tests showed that MIPs, designed using the prostaglandin biosynthetic precursor arachidonic acid, could effectively enrich prostaglandins and structurally related molecules. However, for other lipid mediators, MIP and NIP displayed comparable recoveries. Under optimized conditions, the recoveries of synthetic standards ranged from 62% to 100%. This new extraction method was applied to the determination of the lipid mediators concentration in human plasma and mouse tissues and compared to other methods based on commercially available cartridges. In general, the methods showed comparable performances. In terms of structural specificity, our newly synthesized materials accomplished better retention of prostaglandins (PGs), hydroxydocosahexaenoic acid (HDoHE), HEPE, hydroxyeicosatetraenoic acids (HETE), hydroxyeicosatrienoic acid (HETrE), and polyunsaturated fatty acid (PUFA) compounds, while the commercially available Strata-X showed a higher recovery for dihydroxyeicosatetraenoic acid (diHETrEs). In summary, our results suggest that this new material can be successfully implemented for the extraction of lipid mediators from biological samples.

• Hustoft, Hanne Kolsrud; Vehus, Tore; Brandtzæg, Ole Kristian Merkesvik; Krauss, Stefan; Greibrokk, Tyge & Wilson, Steven Ray Haakon [Show all 7 contributors for this article] (2014). Open tubular lab-on-column/mass spectrometry for targeted proteomics of nanogram sample amounts. PLOS ONE. ISSN 1932-6203. 9(9). doi: 10.1371/journal.pone.0106881. Full text in Research Archive
• Røgeberg, Magnus; Vehus, Tore; Grutle, Lene; Greibrokk, Tyge; Wilson, Steven Ray Haakon & Lundanes, Elsa (2013). Separation optimization of long porous-layer open-tubular columns for nano-LC-MS of limited proteomic samples. Journal of Separation Science. ISSN 1615-9306. 36(17), p. 2838–2847. doi: 10.1002/jssc.201300499.
• Malerød, Helle; Røgeberg, Magnus; Tanaka, Nobou; Greibrokk, Tyge & Lundanes, Elsa (2013). Large volume injection of aqueous peptide samples on a monolithic silica based zwitterionic-hydrophilic interaction liquid chromatography system for characterization of posttranslational modifications. Journal of Chromatography A. ISSN 0021-9673. 1317, p. 129–137. doi: 10.1016/j.chroma.2013.07.083.
• Hustoft, Hanne Kolsrud; Brandtzæg, Ole Kristian Merkesvik; Røgeberg, Magnus; Misaghian, Dorna; Torsetnes, Silje Bøen & Greibrokk, Tyge [Show all 9 contributors for this article] (2013). Integrated enzyme reactor and high resolving chromatography in ‘‘sub-chip’’ dimensions for sensitive protein mass spectrometry. Scientific Reports. ISSN 2045-2322. 3:3511. doi: 10.1038/srep03511. Full text in Research Archive
• Røberg-Larsen, Hanne; Strand, Martin Frank; Grimsmo, Anders; Olsen, Peter Angell; Dembinski, Jennifer & Rise, Frode [Show all 10 contributors for this article] (2012). High sensitivity measurements of active oxysterols with automated filtration/filter backflush-solid phase extraction-liquid chromatography-mass spectrometry. Journal of Chromatography A. ISSN 0021-9673. 1255, p. 291–297. doi: 10.1016/j.chroma.2012.02.002.
• Pedersen-Bjergaard, Stig & Greibrokk, Tyge (2012). Sample preparation - a modern and complex field. Journal of Separation Science. ISSN 1615-9306. 35, p. 2318–2318. doi: 10.1002/jssc.201270143.
• Hustoft, Hanne Kolsrud; Malerød, Helle; Wilson, Steven Ray Haakon; Reubsaet, Leon; Lundanes, Elsa & Greibrokk, Tyge (2012). A critical review of trypsin digestion for LC-MS based proteomics. In Lueng, Eastwood (Eds.), Proteomics / book2. IntechOpen. ISSN 979-953-307-693-4. doi: 10.5772/29326.
• Røgeberg, Magnus; Wilson, Steven Ray Haakon; Malerød, Helle; Lundanes, Elsa; Tanaka, Nobuo & Greibrokk, Tyge (2011). High efficiency, high temperature separations on silica based monolithic columns. Journal of Chromatography A. ISSN 0021-9673. 1218(41), p. 7281–7288. doi: 10.1016/j.chroma.2011.08.049.
• Hustoft, Hanne Kolsrud; Reubsaet, Leon; Greibrokk, Tyge; Lundanes, Elsa & Malerød, Helle (2011). Critical assessment of accelerating trypsination methods. Journal of Pharmaceutical and Biomedical Analysis. ISSN 0731-7085. 56(5), p. 1069–1078. doi: 10.1016/j.jpba.2011.08.013.
• Malerød, Helle; Lundanes, Elsa & Greibrokk, Tyge (2010). Recent advances in on-line multidimensional liquid chromatography. Analytical Methods. ISSN 1759-9660. 2(2), p. 110–122. doi: 10.1039/b9ay00194h.
• Røgeberg, Magnus; Wilson, Steven Ray Haakon; Greibrokk, Tyge & Lundanes, Elsa (2010). Separation of intact proteins on porous layer open tubular (PLOT) columns. Journal of Chromatography A. ISSN 0021-9673. 1217(17), p. 2782–2786. doi: 10.1016/j.chroma.2010.02.025.
• Dahl, S. Rinne; Kleiveland, Charlotte; Kassem, M.; Lea, Tor; Lundanes, Elsa & Greibrokk, Tyge (2009). Determination of thromboxanes, leukotrienes and lipoxins using high-temperature capillary liquid chromatography-tandem mass spectrometry and on-line sample preparation. Journal of Chromatography A. ISSN 0021-9673. 1216(22), p. 4648–4654. doi: 10.1016/j.chroma.2009.03.068. Show summary

  An on-line strong cation-exchange (SCX)-reversed-phase (RP) capillary liquid chromatographic (cLC) method with ion-trap, tandem mass spectrometric (IT-MS/MS) detection for the simultaneous determination of thromboxane (TX) B-2, TXB3, leukotriene (LT) B-4, LTD4 and lipoxin (LX) A(4) in cell culture supernatants was developed and validated. In the present method, a high temperature (70 degrees C) was used for the separation on the analytical column to obtain efficient chromatography of the thromboxanes. An on-line sample preparation was performed, where peptides/proteins contained in the matrix were removed by the SCX Column. Sample pre-treatment included dilution and filtration, and the analysis time including all sample preparation steps was 60min per sample. Limits of detection in the range of 1-4 ng/mL cell Culture supernatant, recoveries between 30% and 100%, within day precisions of less than 20% RSD and between day precisions of less than 30% RSD were obtained. Human mesenchymal stem cells (hMSCs) were stimulated with cytokine-containing supernatants derived from activated human T lymphocytes, and thromboxane, leukotriene and lipoxin production was analysed using the developed method. TXB2 was found in cultures from both non-differentiated and differentiated hMSCs that were stimulated with a cytokine-containing Supernatant obtained from activated T-cells. (C) 2009 Elsevier B.V. All rights reserved.

• Dahl, Sandra Rinne; Ramstad Kleiveland, Charlotte; Kassem, Moustapha; Lea, Tor Erling; Lundanes, Elsa & Greibrokk, Tyge (2009). Determination of thromboxanes, leukotrienes and lipoxins using high-temperature capillary liquid chromatography-tandem mass spectrometry and on-line sample preparation. Journal of Chromatography A. ISSN 0021-9673. 1216(22), p. 4648–4654. doi: 10.1016/j.chroma.2009.03.068.
• Dahl, S. Rinne; Kleiveland, Charlotte; Kassem, M.; Lea, Tor; Lundanes, Elsa & Greibrokk, Tyge (2008). Detecting pM concentrations of prostaglandins in cell culture supernatants by capillary SCX-LC-MS/MS. Journal of Separation Science. ISSN 1615-9306. 31(14), p. 2627–2633. Show summary

  A highly sensitive, improved online strong cation exchange (SCX) - RP capillary liquid chromatographic (cLC) method with IT mass spectrometric (IT-MS/MS) detection for the simultaneous determination of prostaglandin (PG)A(1), PGD(2), PGE(1), PGE(2), PGF(2 alpha), 8-iso-(8i)PGF(2 alpha), 6-keto-(6k)PGF(1 alpha), and 15-Delta(12,14)-deoxy-PGJ(2) (15dPGJ(2) in cell culture supernatants was developed and validated. Pretreatment of the cell Culture supernatants included only dilution and filtration, and the analysis time including all sample preparation steps was 60 min per sample. Peptides/proteins contained ill the matrix were removed by the SCX column. LODs in the range of 8-44 pg/ml (25-120 pM) cell culture supernatant were obtained. Excellent linearity (R-2 > 0.99) and satisfactory recoveries and within and between-day precisions were obtained. Human mesenchymal stem cells (hMSCs) were stimulated with tumor necrosis factor a. (TNF zeta) or TNF alpha/IL-17, and PG production was analyzed using the developed method. The four PGs, 6kPGI(1a) PGF(1a), PGE(2), and PGE(1) were detected both in nonstimulated and stimulated cells. The amount of PG produced by the cell increased when the cell was stimulated.

• Dahl, Sandra Rinne; Kleiveland, CR; Kassem, M; Lea, T; Lundanes, Elsa & Greibrokk, Tyge (2008). Detecting pM concentrations of prostaglandins in cell culture supernatants by capillary SCX-LC-MS/MS. Journal of Separation Science. ISSN 1615-9306. 31, p. 2627–2633. doi: 10.1002/jssc.200800184.
• Tzankova, Mihailova Albena; Malerød, Helle; Wilson, Steven Ray Haakon; Karaszewski, B; Hauser, R & Lundanes, Elsa [Show all 7 contributors for this article] (2008). Improving the resolution of neuropeptides in rat brain with on-line HILIC-RP compared to on-line SCX-RP. Journal of Separation Science. ISSN 1615-9306. 31. doi: 10.1002/jssc.200700257.
• Tran, Bao Quoc; Pepaj, Milaim; Lundanes, Elsa & Greibrokk, Tyge (2008). On-line method for identification of native proteins using pH-gradient SAX chromatography and reversed phase chromatography-mass spectrometry of tryptic peptides. Journal of Liquid Chromatography & Related Technologies. ISSN 1082-6076. 31, p. 1387–1411. doi: 10.1080/10826070802039291.
• Tzankova, Mihailova Albena; Karaszewski, B; Faergestad, EM; Hauser, R; Nyka, WM & Lundanes, Elsa [Show all 7 contributors for this article] (2008). Two-dimensional LC-MS/MS in detection of peptides in hypothalamus of the rat subjected to hypoxic stress. Journal of Separation Science. ISSN 1615-9306. 31. doi: 10.1002/jssc.200700269.
• Tran, Bao Quoc; Loftheim, Håvard; Reubsaet, Jan Leo; Lundanes, Elsa & Greibrokk, Tyge (2008). On-Line multitasking analytical proteomics: How to separate, reduce, alkylate and digest whole proteins in an on-Line multidimensional chromatography system coupled to MS. Journal of Separation Science. ISSN 1615-9306. 31(16-17), p. 2913–2923. doi: 10.1002/jssc.200800275. Show summary

  An on-Line multidimensional system has been developed, consisting of pH gradient strong anion exchange chromatography of native proteins in the first dimension with subsequent trapping and on-column reduction/alkylation on C4 trap columns and RP separation of the alkylated proteins in the second dimension followed by on-column tryptic digestion and electrospray MS detection. The system was evaluated using model proteins and a human urine sample. Compared to the commonly used in-solution alkylation method, the developed on-column method provides an equivalent efficiency. The recovery from the C4 trap columns of the alkylated proteins relative to the native state was from 94 to 102%. On-column tryptic digestion was satisfactory for many, but not for all proteins. The whole analytical procedure was performed on-Line with packed capillary columns for a total time of 320 min for the first ion exchange fraction, with additional 60 min for each subsequent fraction

• Olsen, Raymond; Ovrebo, S; Thorud, S; Lundanes, Elsa; Thomassen, Y & Greibrokk, Tyge [Show all 7 contributors for this article] (2008). Sensitive determination of a glyoxal-DNA adduct biomarker candidate by column switching capillary liquid chromatography electrospray ionization mass spectrometry. The Analyst. ISSN 0003-2654. 133. doi: 10.1039/b719842f.
• Mihailova, Albena; Karaszewski, Bartosz; Færgestad, Ellen M.; Hauser, Roman; Nyka, Walenty M. & Lundanes, Elsa [Show all 7 contributors for this article] (2008). Two dimensional LC-MS/MS in detection of peptides in hypothalamus of the rat subjected to hypoxic stress. Journal of Separation Science. ISSN 1615-9306. 31, p. 468–479. doi: 10.1002/jssc.200700269. Show summary

  A capillary 2-D LC method coupled with IT MS has been used for separation and identification of peptides in rat hypothalamus. Animals of two different age groups (8 and 50 wk) were exposed to two different rates of CO2 in inhaled air to investigate the influence of different hypoxia/hypercapnia levels and their stress-related factor on the peptide excretion. Peptide compounds were fractionated (strong cation exchange chromatography), trapped, and separated (RP chromatography), and MS/ MS mass spectra were used for identification. About 107 peptide compounds were identified and 88 of them were semiquantified. Among the characterized peptides, there were fragments from proteins such as proenkephalin A, proSAAS, prosomatostatin, prooxytocin, vasopressin, etc. Explorative principal component analysis (PCA) combined with hypothesis testing was applied to the obtained data to investigate the impact of age and hypoxic stress factors on the peptide pattern. Twenty-six peptides revealed significant differences in concentrations between the animal groups influenced by age and influx rate.

• Rinne, S.; Kleiveland, Charlotte; Kassem, M.; Lea, Tor; Lundanes, E & Greibrokk, Tyge (2007). Fast and simple online sample preparation coupled with capillary LC-MS/MS for determination of prostaglandins in cell culture supernatants. Journal of Separation Science. ISSN 1615-9306. 30, p. 1860–1869. Show summary

  An online 2-D strong cation exchange (SCX)-RP capillary liquid chromatographic (cLC) method with IT mass spectrometric (IT-MS/MS) detection for the simultaneous determination of prostaglandin (PG) A(1) PGD(2), PGE(1), PGE(2), PGE(2a), 6-keto-(6k)PGF(1a), and l5-Delta(12,14)-deoxy-PGJ(2) (15dPGJ(2)) in cell culture supernatants was developed and validated. Pretreatment of the cell culture supernatants included dilution and filtration, and the analysis time including all sample preparation steps was less than 50 min per sample. Peptides/proteins contained in the matrix were removed by the SCX column. LODs in the range of 0.4-2.2 ng/mL cell culture supernatant, recoveries higher than 80% and within- and between-day precisions of less than 30% RSDs were obtained. Human mesenchymal stem cells (hMSCs) were stimulated with cytokine-containing supernatants derived from activated T lymphocytes, and PG production was analyzed using the developed method. PGE(2) was found in cultures from both untreated and stimulated hMSCs, while PGE(1) was present above the detection limit only in stimulated cells.

• Wilson, Steven Ray Haakon; Malerød, Helle; Petersen, Dirk; Rise, Frode; Lundanes, Elsa & Greibrokk, Tyge (2007). An alternative multiple-trapping LC-SPE-NMR system. Journal of Separation Science. ISSN 1615-9306. 30, p. 322–328. doi: 10.1002/jssc.200600238.
• Mmatli, Edward M; Malerød, Helle; Wilson, Steven Ray Haakon; Abegaz, Berhanu m; Greibrokk, Tyge & Lundanes, Elsa [Show all 9 contributors for this article] (2007). Identification of major metal complexing compounds in Blepharis aspera. Analytica Chimica Acta. ISSN 0003-2670. 597(1), p. 24–31. doi: 10.1016/j.aca.2007.06.042. Show summary

  Verbascoside and isoverbascoside, present at 0.7% and 0.2% (w/w dryweight), were identified to be major compounds that could contribute to the metal complexation in Blepharis aspera collected in Botswana, Africa. The metallophyte B. aspera has high ability to cope with a high level of metal accumulation. The presence of metal complexing compounds and/or antioxidants can prevent oxidative reactions in lipids, proteins and DNA that take place due to the metal accumulation. On-line liquid chromatography–solid phase extraction–nuclear magnetic resonance (LC–SPE–NMR) was applied for the identification, while electrospray-mass spectrometry (ESI-MS) and UV-vis spectroscopy was used to assess whether these compounds can complex with metals. It was found that verbascoside and isoverbascoside may form complexes with nickel, iron (verbascoside only) and copper. Thus, the presence of verbascoside and isoverbascoside can explain the survival of B. aspera in mineral-rich areas.

• Saber, A.L.; Elmosallamy, A.F.; Wilson, Steven Ray Haakon; Lundanes, Elsa & Greibrokk, Tyge (2007). Determination of Oxomemazine in human plasma by capillary LC-ESI-MS. Journal of Liquid Chromatography & Related Technologies. ISSN 1082-6076. 30, p. 393–403. doi: 10.1080/10826070601084860.
• Tzankova, Mihailova Albena; Karaszewski, Bartosz; Hauser, Roman; Lundanes, Elsa & Greibrokk, Tyge (2007). Identification of neuropeptides in rat brain rhinencephalon. Journal of Separation Science. ISSN 1615-9306. 30, p. 249–256.
• Wilson, Steven Ray Haakon; Malerød, Helle; Holm, Anders; Molander, Pål; Lundanes, Elsa & Greibrokk, Tyge (2007). On-line SPE–nano-LC–nanospray-MS for rapid and sensitive determination of perfluorooctanoic acid andperfluorooctane sulfonate in river water. Journal of Chromatographic Science. ISSN 0021-9665. 45(3), p. 146–152. doi: 10.1093/chromsci/45.3.146. Show summary

  An instrumental set up including on-line solid-phase extraction, nano-liquid chromatography, and nanospray mass spectrometry is constructed to improve the sensitivity for quantitation of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in surface water. Sample volumes of 1000 µL are loaded onto a microbore 1.0-mm i.d. × 5 mm, 5 µm Kromasil C18 enrichment column by a carrier solution consisting of 10mM ammonium acetate in acetonitrile-water (10:90, v/v) at a flow rate of 250 µL/min, providing on-line analyte enrichment and sample clean-up. Backflushed elution onto a 0.1-mm i.d. × 150 mm, 3.5 µm Kromasil C18 analytical column is conducted using an acetonitrile-10mM ammonium acetate solvent gradient from 30% to 70% acetonitrile. Water samples are added with internal standard (perfluoroheptanoic acid) and filtrated prior to injection. The mass limits of detection of PFOA and PFOS are 0.5 and 1 pg, respectively, corresponding to concentration limits of detection of 500 pg/L and 1 ng/L, respectively. The total time spent on sample preparation, chromatography, and detection is approximately 12 min per sample. The method was employed for the determination of PFOS and PFOA in urban river water.

• Olsen, Raymond; Backman, Josefin; Molander, Pål; Øvrebø, Steinar; Thorud, Syvert & Lundanes, Elsa [Show all 8 contributors for this article] (2007). Characterization of Adducts Formed in the Reaction of Glutaraldehyde with 2´-deoxyadenosine. Chemical Research in Toxicology. ISSN 0893-228X. 20, p. 965–974. doi: 10.1021/tx7000477. Show summary

  Glutaraldehyde (1,5-pentanedial) is a widely used industrial chemical that has been found to be mutagenic in bacteria and mammalian cells. In this study, we examined the reaction of glutaraldehyde with 2‘-deoxyadenosine and calf thymus DNA in aqueous buffered solutions. The 2‘-deoxyadenosine adducts were isolated by reversed phase HPLC and characterized by their UV absorbance and 1H and 13C NMR spectroscopic and mass spectrometric features. The reaction produced three major adducts. The adduct dA567 was derived from two 2‘-deoxyadenosine units bound together with a piperidine unit, and its yield was 10.4%. The carbons of the piperidine ring originated from glutaraldehyde, whereas the nitrogen of the ring originated from the exocyclic amino group of one of the 2‘-deoxyadenosine units. The adduct dA451d (yield 0.6%) was similar in structure to dA567, but one of the deoxyribose moieties from 2‘-deoxyadenosine was missing. The third adduct, dA334, consisted of a hydroxy-tetrahydropyridine moiety derived from glutaraldehyde and N6 of 2‘-deoxyadenosine (yield 4.0%). Furthermore, LC-ESI-MS/MS analysis of the reaction mixture revealed the formation of compounds with ion peaks of m/z = 352. None of these compounds were sufficiently stable for preparative isolation. They were tentatively identified as a pair of diastereomers of 2,6-dihydroxypiperidine derivatives, which are likely precursors to dA334. Plausible mechanisms for the formation of the adducts are presented. In the reaction of glutaraldehyde with single and double stranded calf thymus DNA, the dA334 adduct was formed.

• Pepaj, Milaim; Lundanes, Elsa & Greibrokk, Tyge (2007). Separation of apolipoprotein A-I from human plasma by on-line two dimensional liquid chromatography. Journal of Liquid Chromatography & Related Technologies. ISSN 1082-6076. 30, p. 1879–1894. doi: 10.1080/10826070701386439.
• Dahl, Sandra Rinne; Ramstad, Charlotte; Kassem, Moustapha; Lea, Tor; Lundanes, Elsa & Greibrokk, Tyge (2007). Fast and simple online sample preparation coupled with capillary LC-MS/MS for determination of prostaglandins in cell culture supernatants. Journal of Separation Science. ISSN 1615-9306. 30, p. 1860–1869.
• Olsen, Raymond; Thorud, S; Hersson, M; Ovrebo, S; Lundanes, Elsa & Greibrokk, Tyge [Show all 9 contributors for this article] (2007). Determination of the dialdehyde glyoxal in workroom air - development of personal sampling methodology. Journal of Environmental Monitoring. ISSN 1464-0325. 9(7), p. 687–694. doi: 10.1089/b700105n.
• Tran, Bao Quoc; Pepaj, Milaim; Lundanes, Elsa & Greibrokk, Tyge (2007). The behaviour of reduced, alkylated and native proteins in a pH-gradient LC system. Chromatographia. ISSN 0009-5893. 66, p. 709–715. doi: 10.1365/s10337-007-0390-8.
• Wilson, Steven Ray Haakon; Greibrokk, Tyge; Lundanes, Elsa; Malerød, Helle; Petersen, Dirk & Rise, Frode (2007). An alternative LC-SPE-NMR design. Journal of Separation Science. ISSN 1615-9306.
• Wilson, SR; Jankowski, M; Pepaj, M; Mihailova, A; Tzankova, Mihailova Albena & Boix, Fernando [Show all 9 contributors for this article] (2007). 2D LC separation and determination of bradykinin in rat muscle tissue dialysate with on-line SPE-HILIC-SPE-RP-MS. Chromatographia. ISSN 0009-5893. 66(7-8), p. 469–474. doi: 10.1365/s10337-007-0341-4.

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• Lundanes, Elsa; Reubsaet, Leon & Greibrokk, Tyge (2013). Chromatography, basic principles, sample preparation and related methods. Wiley-VCH. ISBN 978-3-527-33620-3. 224 p.

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• Greibrokk, Tyge (2016). Molecular imprinting in separation science. Journal of Separation Science. ISSN 1615-9306. 39(5), p. 815–817. doi: 10.1002/jssc.201670054.
• Brandtzæg, Ole Kristian Merkesvik; Hustoft, Hanne Kolsrud; Vehus, Tore; Greibrokk, Tyge; Krauss, Stefan & Reubsaet, Leon [Show all 8 contributors for this article] (2015). On-line protein digestion and peptide separation using “ultra-nano” LC-MS .
• Abele, Silvija; Røgeberg, Magnus; Wilson, Steven Ray Haakon; Lundanes, Elsa & Greibrokk, Tyge (2014). Development of new materials for chromatography - HILIC-PLOT columns for LC-MS analysis of metabolites of cancer stem cells.
• Hustoft, Hanne Kolsrud; Wilson, Steven Ray Haakon; Vehus, Tore; Røgeberg, Magnus; Brandtzæg, Ole Kristian Merkesvik & Greibrokk, Tyge [Show all 7 contributors for this article] (2014). Open tubular enzyme reactors and LC columns for high performance protein analysis.
• Vehus, Tore; Greibrokk, Tyge; Lundanes, Elsa & Wilson, Steven Ray Haakon (2014). Proteomic Analysis of the Wnt/beta-catenin Pathway.
• Røberg-Larsen, Hanne; Krauss, Stefan; Greibrokk, Tyge; Lundanes, Elsa & Wilson, Steven Ray Haakon (2014). Investigating the Role of Endogenous Small Molecules on the Hedgehog Signal Pathway: Very Sensitive, Highly Automated Nano-LC Based Determination of Oxysterols in Cancer Cells.
• Vehus, Tore; Røgeberg, Magnus; Grutle, Lene; Greibrokk, Tyge; Wilson, Steven Ray Haakon & Lundanes, Elsa (2014). Bottom-up proteomikk med «open layer tubular column» for små prøver – applikasjonar og utvikling.
• Johnsen, Elin Follaug; Folven, Lars; Leknes, Siri; Greibrokk, Tyge; Wilson, Steven Ray Haakon & Lundanes, Elsa (2014). On-line coupling of various spe phases with HILIC-LC for enrichment and separation of polar neurotransmitters in various biological matrices.
• Hustoft, Hanne Kolsrud; Brandtzæg, Ole Kristian Merkesvik; Torsetnes, Silje Bøen; Greibrokk, Tyge; Reubsaet, Leon & Wilson, Steven Ray Haakon [Show all 7 contributors for this article] (2014). Development of a nanoproteomic platform with integrated immunocapture and enzymatic digestion for on-line detection of the low abundant cancer biomarker PROGRP.
• Røgeberg, Magnus; Grutle, Lene; Wilson, Steven Ray Haakon; Greibrokk, Tyge & Lundanes, Elsa (2013). Sensitive, high resolving liquid chromatography using 10 μm I.D. porous layer open tubular (PLOT) columns with Orbitrap mass spectrometry.
• Greibrokk, Tyge (2013). From packed LC-columns via SFC to open tubular LC-columns.
• Johnsen, Elin Follaug; Reubsaet, Leon; Stenmark, Harald; Lundanes, Elsa & Greibrokk, Tyge (2012). PLOT kolonner med utskiftbar overflate-funksjonalitet basert på gullnanopartikler.
• Malerød, Helle; Hustoft, Hanne Kolsrud; Reubsaet, Leon; Greibrokk, Tyge & Lundanes, Elsa (2012). Kan proteiner bli enzymatisk klippet i løpet av minutter med nye og akselererte metoder?
• Røgeberg, Magnus; Wilson, Steven Ray Haakon; Malerød, Helle; Tanaka, Nobou; Lundanes, Elsa & Greibrokk, Tyge (2012). Effektiv peptidseparasjon ved bruk av høy temperatur på silikabaserte monolittkolonner.
• Greibrokk, Tyge; Røgeberg, Magnus; Lundanes, Elsa; Misaghian, Dorna & Wilson, Steven Ray Haakon (2012). New open tubular columns in HPLC.
• Greibrokk, Tyge; Røgeberg, Magnus; Wilson, Steven Ray Haakon; Lundanes, Elsa; Misaghian, Dorna & Johnsen, Elin Follaug (2012). Is there a future for open tubular capillary columns in LC?
• Røgeberg, Magnus; Wilson, Steven Ray Haakon; Lundanes, Elsa & Greibrokk, Tyge (2011). Porous Layer Open Tubular Columns for Protein Separations.
• Røgeberg, Magnus; Wilson, Steven Ray Haakon; Malerød, Helle; Tanaka, Nobuo; Lundanes, Elsa & Greibrokk, Tyge (2011). Monolithic silica based columns in proteomics: optimization and applications.
• Røgeberg, Magnus; Wilson, Steven Ray Haakon; Malerød, Helle; Lundanes, Elsa & Greibrokk, Tyge (2011). Monolithic Silica Based Columns for Fast, High Temperature Peptide Separations in Proteomics.
• Malerød, Helle; Hustoft, Hanne Kolsrud; Wilson, Steven Ray Haakon; Reubsaet, Leon; Lundanes, Elsa & Greibrokk, Tyge (2011). Evaluating accelerating methods for trypsin digestion in LC-MS based proteomics.
• Greibrokk, Tyge (2011). Recent Advances in two-dimensional capillary liquid chromatography.
• Greibrokk, Tyge; Lundanes, Elsa; Wilson, Steven Ray Haakon & Malerød, Helle (2010). Two-dimensional capillary LC.
• Greibrokk, Tyge (2010). Multidimensional LC - recent developments.
• Greibrokk, Tyge (2010). Open tubular LC - any news?
• Lundanes, Elsa; Røgeberg, Magnus; Wilson, Steven Ray Haakon; Hustoft, Hanne Kolsrud & Greibrokk, Tyge (2010). Open tubular liquid chromatography - nanospray MS.
• Hustoft, Hanne Kolsrud; Lundanes, Elsa; Greibrokk, Tyge & Reubsaet, Jan Leo (2010). Multidimensjonale nanoLC-MS/MS metoder i jakten på kreftstamcelle markører.
• Malerød, Helle; Lundanes, Elsa & Greibrokk, Tyge (2010). Multidimensjonal væskekromatografi og ulike applikasjoner.
• Brenna, Ida; Olsen, Helle; Lundanes, Elsa; Greibrokk, Tyge & Borge, Grethe Iren Andersen (2010). Determination of flavenoids in cell cultures and intestinal cells.
• Rahho, Rafika; Hustoft, Hanne Kolsrud; Wilson, Steven Ray Haakon; Lundanes, Elsa & Greibrokk, Tyge (2010). Miniaturized capillary columns for protein and peptide analysis.
• Røgeberg, Magnus; Wilson, Steven Ray Haakon; Lundanes, Elsa & Greibrokk, Tyge (2010). Open HPLC columns for protein separations.
• Opsal, Kristin; Malerød, Helle; Wilson, Steven Ray Haakon; Lundanes, Elsa & Greibrokk, Tyge (2010). Quantification of cancer drugs in blood plasma with LC-UV-MS.
• Johnsen, Elin; Wilson, Steven Ray Haakon; Lundanes, Elsa & Greibrokk, Tyge (2010). Method development for determination of (triphosphate) nucleotides on a ZIC-pHILIC column.
• Greibrokk, Tyge & Sellergren, Börje (2009). Molecular imprinting in separation science. Journal of Separation Science. ISSN 1615-9306. 32, p. 3263–3264.
• Greibrokk, Tyge; Wilson, Steven Ray Haakon; Malerød, Helle & Lundanes, Elsa (2009). Multidimensional capillary liquid chromatography.
• Greibrokk, Tyge; Lundanes, Elsa; Wilson, Steven Ray Haakon; Malerød, Helle; Tzankova, Mihailova Albena & Pepaj, Milaim (2009). Multidimensional LC - advantages and limitations.
• Dahl, Sandra Rinne; Lundanes, Elsa; Greibrokk, Tyge & Lea, Tor Erling (2009). LC-MS of known and unknown prostaglandions.
• Malerød, Helle; Tzankova, Mihailova Albena; Færgestad, Ellen M; Karaszewski, Bartosz; Hauser, Roman & Lundanes, Elsa [Show all 7 contributors for this article] (2009). Neuropeptide profiling in rat hippocampus using capillary 2D-LC-MS/MS.
• Greibrokk, Tyge (2008). SFC and SFE in a historical perspective. Journal of Separation Science. ISSN 1615-9306. 31.
• Malerød, Helle; Tzankova, Mihailova Albena; Wilson, Steven Ray Haakon; Karaszewski, Bartosz; Hauser, Roman & Lundanes, Elsa [Show all 7 contributors for this article] (2008). Comparison of on-line HILIC-RP with on-line SCX-RP for separation of neuropeptides in rat brain.
• Kona, T; Dahl, Sandra Rinne; Lea, Tor Erling; Lundanes, Elsa & Greibrokk, Tyge (2008). Capillary liquid chromatography method for determination of adenosine in stem cell culture medium.
• Ellevog, U; Malerød, Helle; Lundanes, Elsa & Greibrokk, Tyge (2008). Solubility and chromatography of membrane proteins.
• Dahl, Sandra Rinne; Kleiveland, C.R.; Lea, Tor Erling; Lundanes, Elsa & Greibrokk, Tyge (2008). Determination of prostanoids in stem cell culture supernatants.
• Dahl, Sandra Rinne; Kleiveland, C.R; Lundanes, Elsa; Greibrokk, Tyge & Lea, Tor Erling (2008). Determination of prostanoids in stem cells – a study to map immunomodulation properties.
• Greibrokk, Tyge; Lundanes, Elsa; Tzankova, Mihailova Albena; Pepaj, Milaim; Tran, Bao Quoc & Wilson, Steven Ray Haakon [Show all 8 contributors for this article] (2008). Two-dimensional LC - principles and some applications.
• Greibrokk, Tyge; Lundanes, Elsa; Tzankova, Mihailova Albena; Pepaj, Milaim & Tran, Bao Quoc (2008). Miniaturized chromatography at the University of Oslo.
• Greibrokk, Tyge; Lundanes, Elsa; Pepaj, Milaim; Tzankova, Mihailova Albena; Wilson, Steven Ray Haakon & Karaszewski, Bartosz [Show all 7 contributors for this article] (2008). Two-dimensional miniaturized LC.
• Greibrokk, Tyge (2008). Two dimensional LC principles and some applications.
• Wilson, Steven Ray Haakon; Greibrokk, Tyge; Lundanes, Elsa; Malerød, Helle; Malterud, Karl Egil & Petersen, Dirk [Show all 9 contributors for this article] (2008). Identification of the major metal compounds in blepharis aspera.
• Malerød, Helle; Tzankova, Mihailova Albena; Karaszewski, Bartosz; Hauser, Roman; Lundanes, Elsa & Greibrokk, Tyge (2008). Determination and identification of neuropeptides in rat hippocampus.
• Chen, Y; Dahl, Sandra Rinne; Malerød, Helle; Lundanes, Elsa & Greibrokk, Tyge (2008). Prostaglandins and molecular imprinted polymers.
• Wilson, Steven Ray Haakon; Greibrokk, Tyge; Lundanes, Elsa; Malerød, Helle; Malterud, Karl Egil & Petersen, Dirk [Show all 7 contributors for this article] (2008). Identification of the major metal compounds in blepharis aspera.
• Wilson, Steven Ray Haakon; Greibrokk, Tyge; Lundanes, Elsa; Malerød, Helle; Jankowski, Mikolaj & Mihailova, Albena (2007). Online two dimensional HILIC-RP separation of peptides.
• Johnsen, Elin Follaug; Lundanes, Elsa; Wilson, Steven Ray Haakon & Greibrokk, Tyge (2017). High performance analytical Tools for small molecules in biosamples. Universitetet i Oslo. ISSN 1501-7710.
• Vesterdal, Caroline; Røberg-Larsen, Hanne; Wilson, Steven Ray Haakon; Greibrokk, Tyge & Lundanes, Elsa (2015). Comparing methods for sensitive determination of Hedgehog active oxysterols. Universitetet i Oslo. Show summary

  Oxysterols in biological samples of limited size are present in low concentrations thus sensitive methods are advantageous. Derivatization of oxysterols prior to liquid chromatography (LC) mass spectrometry (MS) analysis is a common, however a laborious approach. The possibility to reduce the extent of sample preparation by formation of adducts between oxysterols and mobile phase additives (e.g. ammonium acetate) were investigated. Stable adduct ion signals were not obtained with the use of the MS instruments available. However, loss of water ions ([Oxysterol+H-H2O]+ and [Oxysterol+H-2H2O]+, m/z 385.35 and m/z 367.34) were observed when diluting oxysterol standards with ammonium formate (2.5 mM) and formic acid (0.25%) in methanol (MeOH). Under these conditions no easy recognizable fragmentation pattern was observed in tandem MS mode due to clustering of ions in the low mass area when fragmentation energy was applied. Another challenge with the analysis of native oxysterols with a nanoLC system was adsorption to surfaces, especially to fused silica capillaries. Silanization of the fused silica capillaries reduced the issue, but nowhere near satisfactory. It was considered unfeasible to determine native oxysterols with high sensitivity using nanoLC due to the large carry-over issues. Derivatization is therefore recommended when analyzing oxysterols with nanoLC. An on-line automatic filtration filter back-flush solid phase extraction liquid chromatography tandem mass spectrometry (AFFL-SPE-LC-MS/MS) method for determination of Girard T derivatized 24S-hydroxycholesterol, 25-hydroxycholesterol, 27-hydroxycholesterol, and 22S-hydroxycholesterol was modified for analysis of exosome samples. Best separation of oxysterol isomers was obtained with an ACE 3 C18 (0.1 mm ID × 150 mm, 3μm, 100 Å) column with a column temperature of 15°C and by using a mobile phase gradient from 0.1/25/75 (v/v/v %) FA/H2O/MeOH to 0.1/10/90 (v/v/v %) FA/H2O/MeOH in 25 minutes. The method was used for analyses of exosome samples obtained with the use of different isolation techniques to find a suitable procedure for exosome isolation.

• Brandtzaeg, Ole Kristian; Hustoft, Hanne Kolsrud; Wilson, Steven Ray Haakon; Greibrokk, Tyge & Lundanes, Elsa (2014). Open Tubular Enzyme Reactors (OTERs) for On-line Protein Digestion in Liquid Chromatography Mass Spectrometry Proteomics. Universitetet i Oslo. Show summary

  Sample preparation in bottom-up proteomics consists of denaturation, reduction and alkylation of the proteins, before enzymatic digestion of the proteins into peptides. The rate limiting step is the enzymatic digestion, and digestion overnight is recommended. Hence, for faster analysis, the digestion time should be reduced. The main focus of this master thesis was the development of 20 μm inner diameter (ID) open tubular enzyme reactors (OTERs) based on 2-hydroxyethyl methacrylate-co-vinyl azlactone (HEMA-VDM) for on-line protein digestion of limited sample sizes in a nano liquid chromatography (LC) - mass spectrometry (MS) system. Monolithic solid phase extraction (SPE) pre-columns based on butyl methacrylate (BuMa) and polystyrene divinylbenzene (PS-DVB) were prepared in 50 μm ID capillaries and used for trapping of peptides generated by the OTER. These peptides were then separated using 10 μm ID PS-DVB porous layer open tubular (PLOT) columns. The developed OTER was prepared by polymerization using a polymerization mixture consisting of HEMA and VDM as monomer, 1-heptanol or 1-decanol as porogen, and 2,2´azobis(2-methylpropinonitrile) (AIBN) as initiator. Short OTERs were prepared with 1-decanol as porogen, while for longer OTERs, 1-heptanol was used. The sample was loaded onto the OTER with a loading buffer consisting of 50 mM NH4OAc pH 8.75 with 4 % acetonitrile (ACN). A trapping time of 4 min from the OTER to the SPE column was found to be optimal (for the short OTER) using the manual LC-MS-system (developed by Hanne K. Hustoft). The run-to-run retention time repeatability in this system, was 0.25-0.44 % in relative standard deviation (RSD %), and 300 attomoles of targeted recombinant progastrin-releasing peptide isoform 1 (ProGRP) could be detected. The developed long OTER, immobilized with Trypsin/endoproteinase Lys-C (T/L) gave sequence coverages (SQ %) up to 95 % of standard proteins. The optimal reactor temperature during digestion and the optimal digestion time was 37 ºC and 30 min, correspondingly. The OTER could be integrated in an automated LC-MS-system (Hanne K. Hustoft and set up by Tore Vehus), where the within and between digestion repeatability were satisfactory. About 1500 proteins were identified in a single analysis when injecting 1 μg of a human cell lysate sample using the OTER in the automated system.

• Hustoft, Hanne Kolsrud; Lundanes, Elsa; Wilson, Steven Ray Haakon; Reubsaet, Leon & Greibrokk, Tyge (2014). Accelerating enzymatic protein digestion and on-line nano liquid chromatography-mass spectrometry based proteomics. Universitetet i Oslo.
• Köhler, Christian Jeffrey; Thiede, Bernd; Lundanes, Elsa & Greibrokk, Tyge (2013). Isobaric peptide termini labeling (IPTL) - An alternative approach for quantitative proteomics. Universitetet i Oslo.
• Røgeberg, Magnus; Lundanes, Elsa; Greibrokk, Tyge; Wilson, Steven Ray Haakon & Reubsaet, Leon (2013). Monolithic and porous layer open tubular nano columns for peptide and protein separation in liquid chromatography - mass spectrometry. Universitetet i Oslo.
• Malerød, Helle; Greibrokk, Tyge & Lundanes, Elsa (2010). Multidimensional miniaturized LC based methods – developments and applications. Universitetet i Oslo.
• Dahl, Sandra Rinne; Greibrokk, Tyge; Lundanes, Elsa & Lea, Tor Anderssen (2009). Prostaglandins in human mesenchymal stem cells (hMSCs). On-line capillary LC-MS/MS techniques for determination of prostaglandins, thromboxanes, leukotrienes and lipoxins in culture of stimulated stem cells. Universitetet i Oslo.
• Szeto, Kai Chung & Greibrokk, Tyge (2008). Synthesis of metal-organic frameworks: materials with potential applications in catalysis. Universitetet i Oslo.
• Tran, Bao Quoc; Greibrokk, Tyge; Lundanes, Elsa & Rise, Frode (2008). Multidimensional LC methods for proteomics. Universitetet i Oslo.
• Pepaj, Milaim; Greibrokk, Tyge & Lundanes, Elsa (2008). Two-dimensional liquid chromatography of target proteins. Universitetet i Oslo.
• Olsen, Raymond; Molander, Pål; Øvrebø, Steinar; Lundanes, Elsa & Greibrokk, Tyge (2008). Exposure to dialdehydes – DNA adduct characterization and development of analytical methodologies. Universitetet i Oslo og Statens arbeidsmiljøinstitutt. ISSN 1501-7710.

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