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• Rotunno, Giuseppe; Petersen, Dirk & Amedjkouh, Mohamed (2020). Absolute Autocatalytic Amplification under Heterogenous Phase Conditions Involving Subsequent Hydride Transfer and a Hemiacetal Intermediate. ChemSystemsChem. 2(5). doi: 10.1002/syst.201900060. Full text in Research Archive Show summary

  In contrast to the homogenous phase, absolute asymmetric amplification of pyridine alkanol is observed under heterogenous conditions. The reaction of iPr2Zn vapor on a solid powder of pyridine carbaldehyde induced autocatalytic amplification of chirality providing the alkanol product with an enantiopurity up to 90 % ee. In this study, side products were identified and their formation is traced back to redox pathways involving hydride transfer, namely a chiral ester resulting most probably from a disproportionation of the starting aldehyde into a hemiacetal and subsequent hydride loss following a Claisen-Tishchenko mechanism. These observations provide new perspectives in the elucidation of the mechanism of amplification of chirality in the Soai reaction.

• Jochriem, Markus; Casper, Larissa A.; Vanicek, Stefan; Petersen, Dirk; Kopacka, Holger & Wurst, Klaus [Show all 9 contributors for this article] (2020). Rhodocenium Monocarboxylic Acid Hexafluoridophosphate and Its Derivatives: Synthesis, Spectroscopy, Structure, and Electrochemistry. European Journal of Inorganic Chemistry (EurJIC). ISSN 1434-1948. 2020(14), p. 1300–1310. doi: 10.1002/ejic.202000071. Full text in Research Archive Show summary

  As an extension of our continuing work in metallocenium chemistry, we report here on new functionalized rhodocenium salts. In contrast to isoelectronic cobaltocenium compounds, rhodium as a 4d metal allows synthetic routes via prefunctionalized cyclopentadienyl half‐sandwich precursors, thereby facilitating access to monofunctionalized rhodocenium salts containing substituents comprising methyl, trimethylsilyl, carboxylate and carboxylate ester as well as amide derivatives. Synthetic aspects, scope and limitations, as well as spectroscopic (1H/13C‐NMR, IR, HR‐MS), and structural (XRD) properties are reported. Like the parent rhodocenium ion, all new derivatives undergo two chemically consecutive reductions at potentials that depend on the respective ring substituent. The second reduction competes with a rapid reaction of the corresponding rhodocenes to their 18 VE dimers. Rate constants for this process range from 2 × 103 s–1 to 2.5 × 105 s–1 as estimated from digital simulations of experimental voltammograms. Rhodocenium carboxylic acid (8) constitutes a special case in that proton instead of metal reduction is observed at Pt or Au electrodes.

• Paulsen, Britt; Fredriksen, Kim Alex; Petersen, Dirk; Maes, Louis; Matheeussen, An & Naemi, Ali-Oddin [Show all 12 contributors for this article] (2019). Synthesis and antimicrobial activities of N6-hydroxyagelasine analogs and revision of the structure of ageloximes. Bioorganic & Medicinal Chemistry. ISSN 0968-0896. 27(4), p. 620–629. doi: 10.1016/j.bmc.2019.01.002. Full text in Research Archive Show summary

  (+)-N6-Hydroxyagelasine D, the enantiomer of the proposed structure of (–)-ageloxime D, as well as N6-hydroxyagelasine analogs were synthesized by selective N-7 alkylation of N6-[tert-butyl(dimethyl)silyloxy]-9-methyl-9H-purin-6-amine in order to install the terpenoid side chain, followed by fluoride mediated removal of the TBDMS-protecting group. N6-Hydroxyagelasine D and the analog carrying a geranylgeranyl side chain displayed profound antimicrobial activities against several pathogenic bacteria and protozoa and inhibited bacterial biofilm formation. However these compounds were also toxic towards mammalian fibroblast cells (MRC-5). The spectral data of N6-hydroxyagelasine D did not match those reported for ageloxime D before. Hence, a revised structure of ageloxime D was proposed. Basic hydrolysis of agelasine D gave (+)-N-[4-amino-6-(methylamino)pyrimidin-5-yl]-N-copalylformamide, a compound with spectral data in full agreement with those reported for (–)-ageloxime D.

• Lerum, Hans Vigeland; Andersen, Niels Højmark; Eriksen, Dag Øistein; Hansen, Eddy Walther; Petersen, Dirk & Wibetoe, Grethe [Show all 7 contributors for this article] (2018). Study of Cadmium Extraction with Aliquat 336 from Highly Saline Solutions. Journal of Solution Chemistry. ISSN 0095-9782. 47(8), p. 1395–1417. doi: 10.1007/s10953-018-0795-z. Full text in Research Archive
• Frandsen, Rasmus John Normand; Rasmussen, Silas A.; Knudsen, Peter B.; Uhlig, Silvio; Petersen, Dirk & Lysøe, Erik [Show all 9 contributors for this article] (2016). Black perithecial pigmentation in Fusarium species is due to the accumulation of 5-deoxybostrycoidin-based melanin. Scientific Reports. 6. doi: 10.1038/srep26206. Full text in Research Archive Show summary

  Biosynthesis of the black perithecial pigment in the filamentous fungus Fusarium graminearum is dependent on the polyketide synthase PGL1 (oPKS3). A seven-membered PGL1 gene cluster was identified by over-expression of the cluster specific transcription factor pglR. Targeted gene replacement showed that PGL1, pglJ, pglM and pglV were essential for the production of the perithecial pigment. Over-expression of PGL1 resulted in the production of 6-O-demethyl-5-deoxybostrycoidin (1), 5-deoxybostrycoidin (2), and three novel compounds 5-deoxybostrycoidin anthrone (3), 6-O-demethyl-5-deoxybostrycoidin anthrone (4) and purpurfusarin (5). The novel dimeric bostrycoidin purpurfusarin (5) was found to inhibit the growth of Candida albicans with an IC50 of 8.0 +/− 1.9 μM. The results show that Fusarium species with black perithecia have a previously undescribed form of 5-deoxybostrycoidin based melanin in their fruiting bodies.

• Strand, Martin Frank; Wilson, Steven Ray Haakon; Dembinski, Jennifer; Holsworth, Daniel D.; Khvat, Alexander & Okun, Ilya [Show all 8 contributors for this article] (2011). A Novel Synthetic Smoothened Antagonist Transiently Inhibits Pancreatic Adenocarcinoma Xenografts in a Mouse Model. PLOS ONE. 6(6). doi: 10.1371/journal.pone.0019904. Full text in Research Archive
• Uhlig, Silvio; Petersen, Dirk; Rolen, Elin; Jacobsen, Wolfgang Mathias & Vrålstad, Trude (2011). Ergosedmine, a new peptide ergot alkaloid (ergopeptine) from the ergot fungus, Claviceps purpurea parasitizing Calamagrostis arundinacea. Phytochemistry Letters. ISSN 1874-3900. 4(2), p. 79–85. doi: 10.1016/j.phytol.2010.09.004. Full text in Research Archive Show summary

  A new natural ergopeptine, ergosedmine, was isolated from sclerotia of the ascomycete Claviceps purpurea. Its structure was elucidated by 1D- and 2D-NMR spectroscopy and mass spectrometry as N-(N-lysergyl)- cyclo(isoleucyl-phenylanalyl-prolyl). Partial epimerization of ergosedmine into ergosedminine was evident during purification and in DMSO-d(6). According to common ergot alkaloid nomenclature ergosedmine belongs to the ergoannines, one of the four subgroups of ergopeptines. The sclerotia were obtained from reed feather grass (Calamagrostis arundinacea). Phylogenetic analyses using ITS-and beta-tubulin sequences of pure culture isolates obtained from the C. purpurea sclerotia demonstrated that the ergosedmine-producing strain belongs to the genotype G2, which is associated with wet and shady habitats. (C) 2010 Phytochemical Society of Europe. Published by Elsevier B. V. All rights reserved.

• Uhlig, Silvio; Petersen, Dirk; Rolen, Elin; Egge-Jacobsen, Wolfgang & Vrålstad, Trude (2010). Ergosedmine, a new peptide ergot alkaloid (ergopeptine) from the ergot fungus, Claviceps purpurea parasitizing Calamagrostis arundinacea. Phytochemistry Letters. ISSN 1874-3900. 4(2), p. 79–85. doi: 10.1016/j.phytol.2010.09.004. Full text in Research Archive
• Ivanova, Lada; Petersen, Dirk & Uhlig, Silvio (2010). Phomenins and fatty acids from Alternaria infectoria. Toxicon. ISSN 0041-0101. 55(6), p. 1107–1114. doi: 10.1016/j.toxicon.2009.12.017. Full text in Research Archive
• Wilson, Steven Ray Haakon; Strand, Martin Frank; Krapp, Andreas; Rise, Frode; Petersen, Dirk & Krauss, Stefan (2010). Hedgehog antagonist cyclopamine isomerizes to less potent forms when acidified. Journal of Pharmaceutical and Biomedical Analysis. ISSN 0731-7085. 52(5), p. 707–713. doi: 10.1016/j.jpba.2010.02.017. Full text in Research Archive
• Uhlig, Silvio; Ivanova, Lada; Petersen, Dirk & Kristensen, Ralf (2009). Structural studies on minor enniatins from Fusarium sp VI 03441: Novel N-methyl-threonine containing enniatins. Toxicon. ISSN 0041-0101. 53(7-8), p. 734–742. doi: 10.1016/j.toxicon.2009.02.014. Full text in Research Archive
• Uhlig, Silvio & Petersen, Dirk (2008). Lactam ergot alkaloids (ergopeptams) as predominant alkaloids in sclerotia of Claviceps purpurea from Norwegian wild grasses. Toxicon. ISSN 0041-0101. 52(1), p. 175–185. doi: 10.1016/j.toxicon.2008.05.002. Full text in Research Archive
• 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. Full text in Research Archive 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.

• Uhlig, S; Wisloff, H & Petersen, Dirk (2007). Identification of cytotoxic constituents of Narthecium ossifragum using bioassay-guided fractionation. Journal of Agricultural and Food Chemistry. ISSN 0021-8561. 55. doi: 10.1021/jf070776k. Full text in Research Archive
• Larsen, Kristofer; Petersen, Dirk; Wilkins, Alistair; Samdal, Ingunn; Sandvik, Morten & Rundberget, Thomas [Show all 13 contributors for this article] (2007). Clarification of the C-35 stereochemistries of dinophysistoxin-1 and dinophysistoxin-2 and its consequences for binding to protein phosphatase. Chemical Research in Toxicology. ISSN 0893-228X. 20, p. 868–875. Full text in Research Archive Show summary

  Okadaic acid analogues are well known as protein phosphatase inhibitors and occur naturally in marine shellfish feeding on dinoflagellates of the genus Dinophysis, leading to diarrhetic shellfish poisoning of shellfish consumers. Knowledge of the correct structures for these toxins is important in understanding their toxicology, biochemistry, and biosynthesis. We have performed extensive NMR analyses on okadaic acid (1), dinophysistoxin-1 (DTX-1), and dinophysistoxin-2 (DTX-2) obtained from natural sources. Consequently, we were able to unambiguously deduce the stereochemistries at C-35 for DTX-1 and DTX-2 based on analysis of NMR coupling constants and NOE interactions. Our results revealed that DTX-2 (3) has a stereochemistry opposite to that of DTX-1 (2) at C-35. Molecular modeling of the docking of 1-3 with protein phosphatase-1 and protein phosphatase 2A (PP2A) suggested that the reduced affinity of DTX-2 for PP2A may be due to the newly defined stereochemistry at the 35-methyl group. The implications of these findings for biosynthesis and toxicology are discussed.

• Larsen, Kristofer; Petersen, Dirk; Wilkins, Alistair L.; Samdal, Ingunn; Sandvik, Morten & Rundberget, Thomas [Show all 13 contributors for this article] (2007). Clarification of the C-35 Stereochemistries of Dinophysistoxin-1 and Dinophysistoxin-2 and Its Consequences for Binding to Protein Phosphatase. Chemical Research in Toxicology. ISSN 0893-228X. 20(6), p. 868–875. doi: 10.1021/tx700016m. Full text in Research Archive Show summary

  Okadaic acid analogues are well known as protein phosphatase inhibitors and occur naturally in marine shellfish feeding on dinoflagellates of the genus Dinophysis, leading to diarrhetic shellfish poisoning of shellfish consumers. Knowledge of the correct structures for these toxins is important in understanding their toxicology, biochemistry, and biosynthesis. We have performed extensive NMR analyses on okadaic acid (1), dinophysistoxin-1 (DTX-1), and dinophysistoxin-2 (DTX-2) obtained from natural sources. Consequently, we were able to unambiguously deduce the stereochemistries at C-35 for DTX-1 and DTX-2 based on analysis of NMR coupling constants and NOE interactions. Our results revealed that DTX-2 (3) has a stereochemistry opposite to that of DTX-1 (2) at C-35. Molecular modeling of the docking of 1-3 with protein phosphatase-1 and protein phosphatase 2A (PP2A) suggested that the reduced affinity of DTX-2 for PP2A may be due to the newly defined stereochemistry at the 35-methyl group. The implications of these findings for biosynthesis and toxicology are discussed.

• 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. Full text in Research Archive
• Uhlig, Silvio; Wisløff, Helene & Petersen, Dirk (2007). Identification of Cytotoxic Constituents of Narthecium ossifragum Using Bioassay-Guided Fractionation. Journal of Agricultural and Food Chemistry. ISSN 0021-8561. 55(15), p. 6018–6026. Full text in Research Archive
• Aarnes, Halvor; Eriksen, Aud Else Berglen; Petersen, Dirk & Rise, Frode (2007). Accumulation of ammonium in Norway spruce (Picea abies) seedlings measured by in vivo 14N-NMR. Journal of Experimental Botany. ISSN 0022-0957. 58(5), p. 929–934. doi: 10.1093/jxb/erl247. Full text in Research Archive Show summary

  http://jxb.oxfordjournals.org/cgi/content/abstract/erl247? ijkey=y8vx24OpXL2qpyu&keytype=ref 14N-NMR and 31P-NMR have been used to monitor the in vivo pH in roots, stems, and needles from seedlings of Norway spruce, a typical ammonium-tolerant plant. The vacuolar and cytoplasmic pH measured by 31P-NMR was found to be c. pH 4.8 and 7.0, respectively, with no significant difference between plants growing with ammonium or nitrate as the N-source. The 1H-coupled 14NH resonance is pH-sensitive: at alkaline pH it is a narrow singlet line and below pH 4 it is an increasing multiplet line with five signals. The pH values in ammonium-containing compartments measured by 14N-NMR ranged from 3.7 to 3.9, notably lower than the estimated pH values of the Pi pools. This suggests that, in seedlings of Norway spruce, ammonium is stored in vacuoles with low pH possibly to protect the seedlings against the toxic effects of ammonium (NH) or ammonia (NH3). It was also found that concentrations of malate were 3–6 times higher in stems than in roots and needles, with nitrate-grown plants containing more malate than plants grown with ammonium. Key words: Ammonium, cytoplasmic pH, in vivo 14N-NMR, in vivo 31P-NMR, malate, organic acids, Picea abies (L.) Karst, vacuolar pH

• Inngjerdingen, Kari T.; Kiyohara, Hiroaki; Matsumoto, Tsukasa; Petersen, Dirk; Michaelsen, Terje Einar & Diallo, Drissa [Show all 9 contributors for this article] (2007). An immunomodulating pectic polymer from Glinus oppositifolius. Phytochemistry. ISSN 0031-9422. 68(7), p. 1046–1058. doi: 10.1016/j.phytochem.2007.01.011. Full text in Research Archive
• 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. Full text in Research Archive
• Berg, Tom Christian Sung; Bakken, Vebjørn; Gundersen, Lise-Lotte & Petersen, Dirk (2006). Cyclization and Rearrangement Products from Coupling Reactions between Terminal o-Alkynylphenols or o-ethynyl(hydroxymethyl)benzene and 6-Halopurines. Tetrahedron. ISSN 0040-4020. 62, p. 6121–6131. Full text in Research Archive
• Nergård, Cecilie Sogn; Kiyohara, Hiroaki; Reynolds, James; Thomas-Oates, Jane; Matsumoto, Tsukasa & Yamada, Haruki [Show all 11 contributors for this article] (2006). Structures and Structure - Activity Relationships of Three Mitogenic and Complement Fixing Pectic Arabinogalactans from the Malian Antiulcer Plants Cochlospermum tinctorium anA. Rich and Vernonia kotschyana Sch. Bip. ex Walp. Biomacromolecules. ISSN 1525-7797. 7(1), p. 71–79. Full text in Research Archive
• Malerød, Helle; Petersen, Dirk; Nebojsa, Simic; Bobu, Maria-Magdalena; Rise, Frode & Lundanes, Elsa [Show all 8 contributors for this article] (2006). Controlling LC-SPE-NMR systems. Journal of Separation Science. ISSN 1615-9306. 29(4), p. 582–589. Full text in Research Archive
• Wilkins, Alistair L.; Rehman, Nils; Miles, Christopher O.; Torgersen, Trine; Rundberget, Thomas & Keogh, Myra [Show all 9 contributors for this article] (2006). Identification of Fatty Acid Esters of Pectenotoxin-2 Seco Acid in Blue Mussels (Mytilus edulis) from Ireland. Journal of Agricultural and Food Chemistry. ISSN 0021-8561. 54(15), p. 5672–5678. Full text in Research Archive
• Miles, Christopher O.; Wilkins, Alistair L.; Hawkes, Alan D.; Jensen, Dwayne J.; Coony, Janine M. & Larsen, Kristofer [Show all 10 contributors for this article] (2006). Isolation and identification of a cis-C8-diol-ester of okadaic acid from Dinophysis acuta in New Zealand. Toxicon. ISSN 0041-0101. 48(2), p. 195–203. Full text in Research Archive
• Spilsberg, Bjorn; Rise, Frode; Petersen, Dirk & Nissen-Meyer, Jon (2006). Thymidine secretion by hybridoma and myeloma cells. Biochemical and Biophysical Research Communications - BBRC. ISSN 0006-291X. 342, p. 221–226. Full text in Research Archive
• Bakkestuen, Anne Kristin Vibstad; Gundersen, Lise-Lotte; Petersen, Dirk; Utenova, Bibigul & Vik, Anders (2005). Synthesis and Antimycobacterial Activity of Agelasine E and Analogs. Organic and biomolecular chemistry. ISSN 1477-0520. 3, p. 1025–1033. Full text in Research Archive
• Rise, Frode; Miles, Christopher O.; Samdal, Ingunn; Aasen, John A. G.; Jensen, Dwayne J. & Quilliam, Michael A. [Show all 11 contributors for this article] (2005). Evidence for numerous analogs of yessetoxin in Protoceratium reticulatum. Harmful Algae. ISSN 1568-9883. 4, p. 1075–1091. doi: 10.1016/j.hal.2005.03.005. Full text in Research Archive
• Miles, Christopher; Samdal, Ingunn; Bunæs, John A Aasen; Jensen, Dwayne; Quilliam, Michael & Petersen, Dirk [Show all 11 contributors for this article] (2005). Evidence for numerous analogs of yessotoxin in Protoceratium reticulatum. Harmful Algae. ISSN 1568-9883. 4(6), p. 1075–1091. Full text in Research Archive
• Uhlig, Silvio; Petersen, Dirk; Flåøyen, Arne & Wilkins, Alistair (2005). 2-Amino-14,16-dimethyloctadecan-3-ol, a new sphingosine analogue toxin in the fungal genus Fusarium. Toxicon. ISSN 0041-0101. 46, p. 513–522. Full text in Research Archive
• Abegaz, Berhanu m; Ngadjui, Bonaventure t; Folefoc, Gabriel n; Fotso, Serge; Ambassa, Pantaleon & Bezabih, Merhatibeb [Show all 9 contributors for this article] (2004). Prenylated flavonoids, monoterpenoid furanocoumarins and other constituents from the twigs of Dorstenia elliptica (Moraceae). Phytochemistry. ISSN 0031-9422. 65, p. 221–226. Full text in Research Archive
• Bjørgen, Morten; Olsbye, Unni; Petersen, Dirk & Kolboe, Stein (2004). The methanol-to-hydrocarbons reaction: insight into the reaction mechanism from [C-12]benzene and [C-13]methanol coreactions over zeolite H-beta. Journal of Catalysis. ISSN 0021-9517. 221, p. 1–10. Full text in Research Archive
• Petersen, Dirk; Miles, Christopher O.; Wilkins, Alistair L.; Samdal, Ingunn A.; Sandvik, Morten & Quilliam, Michael A. [Show all 12 contributors for this article] (2004). A Novel Pectenotoxin, PTX-12, in Dinophysis Spp. and Shellfish from Norway. Chemical Research in Toxicology. ISSN 0893-228X. 17/11, p. 1423–1433. Full text in Research Archive
• Miles, Christopher; Wilkins, A.L.; Samdal, Ingunn; Sandvik, Morten; Petersen, Dirk & Quilliam, Michael [Show all 12 contributors for this article] (2004). A Novel Pectenotoxin, PTX-12, in Dinophysis Spp. and Shellfish from Norway. Chemical Research in Toxicology. ISSN 0893-228X. 17, p. 1423–1433. Full text in Research Archive
• Hu, Chunxiang; Liu, Yongding; Paulsen, Berit Smestad; Petersen, Dirk & Klaveness, Dag (2003). Extracellular carbohydrate polymeres from five desert soil algae with different cohesion in the stabilization of fine sand grain. Carbohydrate Polymers. ISSN 0144-8617. 54(1), p. 33–42. Full text in Research Archive
• Hassel, Bjørnar; Bråthe, Anders & Petersen, Dirk (2002). Cerebral dicarboxylate transport and metabolism studied with isotopically labelled fumarate, malate and malonate. Journal of Neurochemistry. ISSN 0022-3042. 82(2), p. 410–419. Full text in Research Archive
• Johannessen, Cecilie U.; Petersen, Dirk; Fonnum, Frode & Hassel, Bjørnar (2002). The acute effect of valproate on cerebral energy metabolism in mice. Epilepsy Research. ISSN 0920-1211. 47, p. 247–256. Full text in Research Archive
• Hansen, L.; Størmer, Fredrik C.; Petersen, Dirk & Aasen, Arne Jørgen (2001). Cycloechinulin - a Trp-Ala-derived alkaloid from the fungus Aspergillus ochraceus. Acta Crystallographica Section E: Structure Reports Online. 57(10), p. 909–912. Full text in Research Archive Show summary

  The structure of the Trp-Ala-derived, non-basic alkaloid cycloechinulin from the mycelial mat of the fungus Aspergillus ochraceus is described; systematic name: (3S)-2,3,8,9-tetrahydro- 11-methoxy-3,8,8-trimethylpyrazino[1´,2´:1,2]azocino- [5,4-b]indole-1,4-dione/methanol (4/1), C20H21N3O3/0.25- CH3OH. There are four independent molecules plus one methanol molecule in the asymmetric unit. The conformations of molecules 1-3 are almost identical, while molecule 4 shows a different conformation in the fused 8-6 ring moiety.

• Spilsberg, Bjørn; Rise, Frode; Petersen, Dirk & Nissen-Meyer, Jon (2000). Secretion of thymidine by hybridoma cells. In Zoref-Shani, Esther & Sperling, Oded (Ed.), Advances in experimental medicine and biology: Purine and pyrimidine metabolism in man. Kluwer Academic / Plenum Publishers, New York. ISSN 9780306465154. p. 295–301. Full text in Research Archive

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• Paulsen, Britt; Fredriksen, Kim Alex; Petersen, Dirk; Maes, Louis; Matheeussen, An & Naemi, Ali-Oddin [Show all 12 contributors for this article] (2019). Synthesis directed towards bioactive ent-Ageloxime D and analogues. Full text in Research Archive
• Paulsen, Britt; Fredriksen, Kim Alex; Petersen, Dirk; Maes, Louis; Matheeussen, An & Naemi, Ali-Oddin [Show all 11 contributors for this article] (2019). Synthesis directed towards bioactive ent-Ageloxime D and analogues. Full text in Research Archive
• Lerum, Hans Vigeland; Bouzga, Aud Mjærum; Jørgensen, Sissel; Petersen, Dirk; Eriksen, Dag Øistein & Hansen, Eddy Walther [Show all 8 contributors for this article] (2016). Study of cadmium extraction from aqueous solutions with high chloride concentration using radiotracer and NMR. Full text in Research Archive
• Lerum, Hans Vigeland; Bouzga, Aud Mjærum; Jørgensen, Sissel; Petersen, Dirk; Eriksen, Dag Øistein & Hansen, Eddy Walther [Show all 8 contributors for this article] (2016). LIQUID-LIQUID EXTRACTION OF CADMIUM CHLORIDE COMPLEXES STUDIED BY NMR. Full text in Research Archive
• Wilson, Steven Ray Haakon; Petersen, Dirk; Rise, Frode & Krauss, Stefan (2009). Exporing the chemistry of the anti-cancer drug cycopamine with LC-MS and NMR. Full text in Research Archive
• Wilson, Steven Ray Haakon; Strand, Martin Frank; Rise, Frode; Petersen, Dirk; Lundanes, Elsa & Krauss, Stefan (2009). NMR and LC-MS Analysis of Natural and Acid-Induced Isomers of Cyclopamine. Full text in Research Archive
• 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. Full text in Research Archive
• Uhlig, Silvio; Ivanova, Lada; Petersen, Dirk & Kristensen, Ralf (2008). Indications of a novel class of naturally occurring enniatins containing N-methyl-threonine. Full text in Research Archive
• 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. Full text in Research Archive
• Rise, Frode; Mmatli, Edward Eddie; Malerød, Helle; Wilson, Steven Ray Haakon; Lundanes, Elsa & Greibrokk, Tyge [Show all 8 contributors for this article] (2007). Identification of Phenylethyl Glycosides from Blepharis Aspera by LC-UV-SPE-NMR/MS Hyphenation. Full text in Research Archive
• Larsen, Kristofer; Petersen, Dirk; Wilkins, Alistair L.; Goldstone, David; Arcus, Vickery & Rise, Frode [Show all 7 contributors for this article] (2007). The C-35 Stereochemisties for Dinophysistoxin-1 and Dinophysistoxin-2 and its consequenses for biosynthesis and binding to protein phosphatases. Full text in Research Archive
• Larsen, Kristofer; Wilkins, Alistair L.; Goldstone, David; Vickery, Arcus; Rise, Frode & Miles, Christopher O. [Show all 7 contributors for this article] (2007). The C-35 Stereochemistries for Dinophysistoxin-1 and Dinophysistoxin-2 and its consequences for biosynthesis and binding to protein phosphatases. Full text in Research Archive
• Rise, Frode; Malerød, Helle; Mmatli, Edward Eddie; Wilson, Steven Ray Haakon; Lundanes, Elsa & Greibrokk, Tyge [Show all 8 contributors for this article] (2007). Identification of Phenylethyl Glycosides from Blepharis aspera by LC-UV-SPE-NMR/MS Hyphenation. Full text in Research Archive
• Larsen, Kristofer; Petersen, Dirk; Wilkins, Alistair L.; Samdal, Ingunn; Sandvik, Morten & Rundberget, Thomas [Show all 13 contributors for this article] (2007). Clarification of the C-35 Stereochemistries of Okadaic Acid, Dinophysistoxin-1, and Dinophysistoxin-2, and its consequences for binding to protein phosphatase. Full text in Research Archive
• Larsen, Kristofer; Petersen, Dirk; Wilkins, Alistair L.; Samdal, Ingunn; Sandvik, Morten & Rundberget, Thomas [Show all 13 contributors for this article] (2007). Clarification of the C-35 Stereochemistries of Okadaic Acid, Dinophysistoxin-1, and Dinophysistoxin-2, and its consequences for binding to protein phosphatase. Full text in Research Archive
• Malerød, Helle; Wilson, Steven Ray Haakon; Petersen, Dirk; Rise, Frode; Lundanes, Elsa & Greibrokk, Tyge (2007). Structure determination using on-line LC-MS/NMR. Full text in Research Archive
• Larsen, Kristofer; Petersen, Dirk; Wilkins, A.L.; Samdal, Ingunn; Sandvik, Morten & Rundberget, Thomas [Show all 13 contributors for this article] (2006). The C-35 Stereochemistries for dinophysistoxin - 1 and dinophysistoxin - 2 and its consequences for binding to proteinphosphatases. Full text in Research Archive
• Berg, Tom Christian; Bakken, Vebjørn; Gundersen, Lise-Lotte & Petersen, Dirk (2006). Cyclisation and Rearrangement Products from Coupling Reactions between terminal o-Alkynylphenols or o-ethynyl(hydroxymethyl)benzene and 6-Halopurines. Full text in Research Archive
• Larsen, Kristofer; Rise, Frode; Petersen, Dirk; Miles, Christopher O. & Wilkins, Alistair L. (2006). Clarification of the C-35 Stereochemistry of DTX-1. Full text in Research Archive
• Nebojsa, Simic; Wilson, Steven Ray; Malerød, Helle; Petersen, Dirk; Bobu, M M & Rise, Frode [Show all 8 contributors for this article] (2006). Controlling LC-SPE-NMR Systems. Full text in Research Archive
• Larsen, Kristofer; Rise, Frode; Petersen, Dirk; Miles, Christopher O. & Wilkins, Alistair L. (2006). Clarification of the C-35 Stereochemistry of DTX-1. Full text in Research Archive
• Uhlig, Silvio; Petersen, Dirk; Wilkins, Alistair Lawrence & Flåøyen, Arne (2006). 2-amino-14,16-dimethyl-octadecan-3-ol - A Noval Fusarium Metabolite with Biological Activity. Full text in Research Archive
• Rise, Frode; Mmatli, Edward Eddie; Malerød, Helle; Wilson, Steven Ray Haakon; Lundanes, Elsa & Greibrokk, Tyge [Show all 8 contributors for this article] (2006). Identification of Phenylethyl Glycosides from Blepharis aspera by LC-UV-SPE-NMR/MS Hyphenation. Full text in Research Archive Show summary

  Conclusions Verbascoside and isoverbascoside were isolated and purified from Blepharis aspera. An in lab designed LC-UV-SPE-NMR/MS system was successfully used to separate the two compounds and to obtain their 1H NMR data online using a 30 micro liter LC-NMR probe.

• Rise, Frode; Petersen, Dirk; Nebojsa, Simic; Wilson, Steven Ray & Malerød, Helle (2005). LC-NMR. Full text in Research Archive
• Berg, Tom Christian; Gundersen, Lise-Lotte & Petersen, Dirk (2005). Cyclization Reactions on 6-(Hydroxyalk-1-ynyl)purines. Full text in Research Archive
• Rise, Frode; Petersen, Dirk; Nebojsa, Simic & Wilson, Steven Ray (2004). LC-NMR. Full text in Research Archive
• Uhlig, Silvio; Petersen, Dirk; Wilkins, Alistair Lawrence & Flåøyen, Arne (2004). A Novel Fusarium Metabolite with Biological Activity. Full text in Research Archive
• Miles, Christopher; Wilkins, A.L.; Samdal, Ingunn; Sandvik, Morten; Rundberget, Thomas & Petersen, Dirk [Show all 14 contributors for this article] (2004). PTX-12, a New Pectenotoxin Present in Scandinavian Shellfish and Dinophysis. Full text in Research Archive
• Aarnes, Halvor; Eriksen, Aud Else Berglen; Petersen, Dirk & Rise, Frode (2004). In Vivo 14N-NMR and 31P-NMR: intracellular pH in Norway spruce (Picea abies) seedlings grown on ammonium or nitrate. Full text in Research Archive
• Miles, Christopher; Wilkins, Alistair Lawrence; Samdal, Ingunn Anita; Briggs, Lyn R.; Bunæs, John A Aasen & Cooney, Janine M. [Show all 14 contributors for this article] (2003). Identification of new yessotoxins. Full text in Research Archive
• Briggs, Lyn; Fitzgerald, Joan; Garthwaite, Linda; Miles, Christopher; Garthwaite, Ian & Ross, Kathryn [Show all 12 contributors for this article] (2002). Immunoassays for the analysis of yessotoxins. Full text in Research Archive
• Briggs, L.R.; Fitzgerald, Joan; Garthwaite, I.; Miles, Christopher; Ross, Karen & Towers, N.R. [Show all 11 contributors for this article] (2002). Immunoassays for analysis of yessotoxins. Full text in Research Archive Show summary

  Polyclonal antibodies that bind to yessotoxin (YTX) and its analogues have been produced. The antibodies were used to develop ELISAs as part of a research programme carried out at AgResearch to develop rapid screening methods for algal toxins in shellfish. Direct and indirect formats for the assays have been optimised and yessotoxins have been quantified in water samples, shellfish (both whole flesh and hepatopancreas) and algal extracts. The most sensitive format has a limit of quantitation of 20 pg/mL. Dilution of shellfish extracts 300-fold eliminates matrix effects. Although dilution raises the limit of quantitation, assay sensitivity is still well below the EU recommended maximum levels of 1 mg/kg of shellfish flesh. Cross-reactivity studies have demonstrated that the anti-YTX antibodies also bind YTXs modified at the C-40 end of the molecule, as well as homoYTX (although cross-reactivities are lower for analogues where functional groups on C-1 are modified). The assay is therefore able to detect all the YTX analogues that the EU currently requires shellfish to be tested for. In addition, because of the immunogen chemistry, it is expected that the antibodies will also recognise the toxic analogues adriatoxin and carboxyessotoxin¿although confirmation of this has not been possible due to a lack of standards for these toxins. Because the antibodies can bind to a wide range of YTX analogues, the ELISA response for algal and shellfish samples is often greater than with other analytical methods (e.g. HPLC) that do not measure all YTX analogues. Nevertheless, results from ELISA and LC-MS analyses of shellfish extracts showed a good linear correlation. Studies are under way to determine the nature of the YTX analogues responsible for the increased response of the ELISA. Chromatography of extracts from Protoceratium reticulatum followed by ELISA analysis has provided ELISA-reactive fractions. Preliminary analysis of these fractions by NMR and LC-MS has confirmed the presence of a complex mixture of yessotoxin analogues. Similar studies on contaminated shellfish are also planned. Commercialisation of a yessotoxin ELISA is now in progress. Keyword1: yessotoxin Keyword2: immunoassay

• Briggs, L.R.; Miles, C. O.; Garthaite, I.; Ross, Karen; Towers, N.R. & Samdal, Ingunn [Show all 10 contributors for this article] (2002). Immunoassays for the analysis of yessotoxins. Full text in Research Archive Show summary

  Polyclonal antibodies that bind to yessotoxin (YTX) and its analogues have been produced. The antibodies were used to develop ELISAs as part of a research programme carried out at AgResearch to develop rapid screening methods for algal toxins in shellfish. Direct and indirect formats for the assays have been optimised and yessotoxins have been quantified in water samples, shellfish (both whole flesh and hepatopancreas) and algal extracts. The most sensitive format has a limit of quantitation of 20 pg/mL. Dilution of shellfish extracts 300-fold eliminates matrix effects. Although dilution raises the limit of quantitation, assay sensitivity is still well below the EU recommended maximum levels of 1 mg/kg of shellfish flesh. Cross-reactivity studies have demonstrated that the anti-YTX antibodies also bind YTXs modified at the C-40 end of the molecule, as well as homoYTX (although cross-reactivities are lower for analogues where functional groups on C-1 are modified). The assay is therefore able to detect all the YTX analogues that the EU currently requires shellfish to be tested for. In addition, because of the immunogen chemistry, it is expected that the antibodies will also recognise the toxic analogues adriatoxin and carboxyessotoxin¿although confirmation of this has not been possible due to a lack of standards for these toxins. Because the antibodies can bind to a wide range of YTX analogues, the ELISA response for algal and shellfish samples is often greater than with other analytical methods (e.g. HPLC) that do not measure all YTX analogues. Nevertheless, results from ELISA and LC-MS analyses of shellfish extracts showed a good linear correlation. Studies are under way to determine the nature of the YTX analogues responsible for the increased response of the ELISA. Chromatography of extracts from Protoceratium reticulatum followed by ELISA analysis has provided ELISA-reactive fractions. Preliminary analysis of these fractions by NMR and LC-MS has confirmed the presence of a complex mixture of yessotoxin analogues. Similar studies on contaminated shellfish are also planned. Commercialisation of a yessotoxin ELISA is now in progress.

• Spilsberg, Bjørn; Rise, Frode; Petersen, Dirk & Nissen-Meyer, Jon (2001). SECRETION OF THYMIDINE BY HYBRIDOMA CELLS. Full text in Research Archive Show summary

  Myeloma and hybridoma cells have been reported to secrete a low molecular weight growth inhibitory factor (Rønning et al., 1991, Cytotechnology 7, 15-24; Røe, Ø. et al., 1999, Biochem. Biophys. Res. Commun. 254, 138-142). The factor was identified as thymidine by NMR spectroscopy after isolation to homogeneity from hybridoma cell cultures by ultrafiltration, dialysis concentration and reverse phase chromatography under acidic and neutral conditions. Taken together, the results suggest that hybridoma cells and possibly myeloma cells secrete thymidine.

• Spilsberg, Bjørn; Rise, Frode; Petersen, Dirk; Rønning, Øystein W. & Nissen-Meyer, Jon (2000). The low-molecular-weight "growth inhibitory factor" produced by hybridoma cell culture identifed as thymidine by NMR-spectroscopy. Full text in Research Archive
• Spilsberg, Bjørn; Rise, Frode; Petersen, Dirk; Rønning, Øystein W. & Nissen-Meyer, Jon (2000). The low-molecular-weight "growth inhibitory factor" produced by hybridoma cell cultures identified as thymidine by NMR-spectroscopy. Full text in Research Archive Show summary

  Myeloma and hybridoma cells have been reported to secrete a low-molecular-weight growth inhibitory factor (1, 2). This factor was isolated to homogeneity from the media (4.0 liters) of hybridoma cell cultures by ultrafiltration, ¿dialysis concentration¿ and reverse phase chromatography under acidic and neutral conditions. The inhibitory factor was identified as thymidine by NMR spectroscopy. (1) Rønning, Ø.W., Schartum, M., Winsnes, A. and Lindberg, G. (1991) Growth limitation in hybridoma cell cultures: The role of inhibitory or toxic metabolites. Cytotechnology 7, 15-24. (2) Røe, Ø., Brondz, I., Rønning, Ø. and Nissen-Meyer, J. (1999) Isolation of a low-molecular-weight growth inhibitory factor from hybridoma cell cultures. Biochem. Biophys. Res. Commun. 254, 138-142.

• Rise, Frode & Petersen, Dirk (2007). Processing and plotting of 2D NMR spectra - TOCSY, NOESY and HSQC. Dirk Petersen and Frode Rise. Full text in Research Archive
• Petersen, Dirk (2007). SHIMMING BRUKER NMR INSTRUMENTS. Dirk Petersen. Full text in Research Archive

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