Ulla Jacobsson

Orientation of the pine weevil Hylobius abietis to underground sources of host volatiles

Adults of Hylobius abietis (L.) (Coleoptera: Curculionidae) were found to locate conifer roots suitable for oviposition by utilizing host volatiles diffusing through the soil. Underground sources of host volatiles were presented to weevils in a laboratory bioassay. A cold‐trapping condensate of Scots pine, Pinus sylvestris L., and fractions of it were tested. Various fractions containing host terpenes attracted weevils in the bioassay, but the complete pine condensate caused the highest response. Ethanol was also found to be attractive. Weevils caged underground in the absence of host material did not attract weevils on the surface.

Sesquiterpene lactones from Michelia champaca

Five sesquiterpene lactones were isolated from Michelia champaca root bark. One of these, michampanolide (2,7-dihydroxy-3,7-dimethyl-11-methylene-13-oxatricyclo[8,3,0,0,3,b]tridecan-12-one), possessed a new skeleton, while two others, 8-acetoxyparthenolide and magnograndiolide, were isolated for the first time from M. champaca.

Pathways of glutamine metabolism in Spodoptera frugiperda (Sf9) insect cells: evidence for the presence of the nitrogen assimilation system, and a metabolic switch by 1H/15N NMR☆

1H/15N and 13C NMR were used to investigate metabolism in Spodoptera frugiperda (Sf9) cells. Labelled substrates ([2-15N]glutamine, [5-15N]glutamine, [2-15N]glutamate, 15NH4Cl, [2-15N]alanine, and [1-13C]glucose) were added to batch cultures and the concentration of labelled excreted metabolites (alanine, NH4+, glutamine, glycerol, and lactate) were quantified. Cultures with excess glucose and glutamine produce alanine as the main metabolic by-product while no ammonium ions are released. 1H/15N NMR data showed that both the amide and amine-nitrogen of glutamine was incorporated into alanine in these cultures. The amide-nitrogen of glutamine was not transferred to the amine-position in glutamate (for further transamination to alanine) via free NH4+ but directly via an azaserine inhibitable amido-transfer reaction. In glutamine-free media 15NH4+ was consumed and incorporated into alanine. 15NH4+ was also incorporated into the amide-position of glutamine synthesised by the cells. These data suggest that the nitrogen assimilation system, glutamine synthetase/glutamate synthase (NADH-GOGAT), is active in glutamine-deprived cells. In cultures devoid of glucose, ammonium is the main metabolic by-product while no alanine is formed. The ammonium ions stem both from the amide and amine-nitrogen of glutamine, most likely via glutaminase and glutamate dehydrogenase. 13C NMR revealed that the [1-13C] label from glucose appeared in glycerol, alanine, lactate, and in extracellular glutamine. Labelling data also showed that intermediates of the tricarboxylic acid cycle were recycled to glycolysis and that carbon sources, other than glucose-derived acetylCoA, entered the cycle. Furthermore, Sf9 cell cultures excreted significant amounts glycerol (1.9-3.2 mM) and ethanol (6 mM), thus highlighting the importance of sinks for reducing equivalents in maintaining the cytosolic redox balance.

Stereochemistry of two epoxy alcohols from Saprolegnia parasitica

Abstract Two epoxy alcohols, 11,12-epoxy-15-hydroxy-5,8,13-eicosatrienoic acid and 13,14-epoxy-15-hydroxy-5, 8,11-eicosatrienoic acid, were recently isolated following incubation of arachidonic acid with homogenates of the fungus, Saprolegnia parasitica (Hamberg, M., Herman, C.A. and Herman, R.P. (1986) Biochim. Biophys. Acta 877, 447–457). In the present study the complete stereochemical structures of the two epoxy alcohols were determined by steric analysis of short chain acids formed by chemical degradation and by NMR-spectrometric analysis. The epoxy alcohols were found to be 11(S),12(R)-epoxy-15(S)-hydroxy-5 (Z),8(Z),13(E)-eicosatrienoic acid and 13(R),14(R)-epoxy-15(S)-hydroxy-5(Z),8(Z),11(Z). eicosatrienoic acid.

Elevated glutamate dehydrogenase flux in glucose-deprived hybridoma and myeloma cells: Evidence from 1H/15N NMR

The glutamine metabolism was studied in glucose-starved and glucose-sufficient hybridoma and Sp2/0-Ag14 myeloma cells. Glucose starvation was attained by cultivating the hybridoma cells with fructose instead of glucose, and the myeloma cells with a low initial glucose concentration which was rapidly exhausted. Glutamine used in the experiments was labeled with 15N, either in the amine or in the amide position. The fate of the label was monitored by 1H/15N NMR analysis of released 15NH+4 and 15N-alanine. Thus, NH+4 formed via glutaminase (GLNase) could be distinguished from NH+4 formed via glutamate dehydrogenase (GDH). In the glucose-sufficient cells a small but measurable amount of 15NH+4 released by GDH could be detected in both cell lines (0.75 and 0.31 micromole/10(6) cells for hybridoma and myeloma cells, respectively). The uptake of glutamine and the total production of NH+4 was significantly increased in both fructose-grown hybridoma and glucose-starved myeloma cells, as compared to the glucose-sufficient cells. The increased NH+4 production was due to an increased throughput via GLNase (1.6 -1.9-fold in the hybridoma, and 2.7-fold in the myeloma cell line) and an even further increased metabolism via GDH (4.8-7.9-fold in the hybridoma cells, and 3.1-fold in the myeloma cells). The data indicate that both GLNase and GDH are down-regulated when glucose is in excess, but up-regulated in glucose-starved cells. It was calculated that the maximum potential ATP production from glutamine could increase by 35-40 % in the fructose-grown hybridoma cells, mainly due to the increased metabolism via GDH.

Synthesis and characterization of all four isomers of methyl 2,4-decadienoate for an investigation of the pheromone components of Pityogenes chaicographus

Synthesis and Characterization of All 4 Isomers of Methyl 2,4-Decadienoate for an Investigation of the Pheromone Components of Pityogenes-Chalcographus

High pressure approach to the total synthesis of 6-EPI-d-purpurosamine b

Abstract Methyl 2,6-di- N -acetyl-6-epi-α- D -purpurosaminide B ( 11 ) was synthesized from L -alanine by an eleven-step reaction sequence. Eu(fod)3-mediated high-pressure (4+2) cycloaddition of 1-methoxybuta-1 ,3-diene ( 2 ) to α-amino aldehyde 3 , easily available from L -alanine ( 4 ), is the key step in the synthetic sequence.

Determination of NADH-dependent glutamate synthase (GOGAT) in Spodoptera frugiperda (Sf9) insect cells by a selective 1H/15N NMR in vitro assay.

This is the second of two papers [Drews, M., Doverskog, M., Ohman, L., Chapman, B.E., Jacobsson, U., Kuchel, P.W., Häggström, L., 2000. Pathways of glutamine metabolism in Spodoptera frugiperda (Sf9) insect cells: evidence for the presence of the nitrogen assimilation system, and a metabolic switch by 1H/15N NMR. J. Biotechnol. 78, 23-37]. where the general goal has been to determine and characterise the glutamine metabolism in Sf9 cells. The presence of glutamate synthase (GOGAT) activity was investigated in cell-free extracts of S. frugiperda (Sf9) insect cells by modified 1H/15N spin-echo and gradient enhanced multiple quantum coherence NMR spectroscopy techniques. Cell-free extracts were prepared from cells cultured in a serum-free medium. The assay conditions were based on conventional spectrophotometric and chromatographic methods. NMR data showed that nitrogen from [5-15N] glutamine was selectively incorporated into 2-oxoglutarate forming [2-15N] glutamate with a specific activity of 4.15 +/- 0.21 nmol [2-15N] glutamate min -1 (mg total protein)-1 in the cell-free extracts. The enzyme activity was exclusively dependent on NADH as coenzyme and was completely inhibited by 1 mM azaserine. From the results obtained, we conclude that Sf9 cells possess NADH-GOGAT activity. Furthermore, the high specificity of the NMR method enables distinction of competing reactions from glutaminase and glutamate dehydrogenase.

Structures, absolute configurations, and syntheses of volatile signals from three sympatric ant-lion species,Euroleon nostras, Grocus bore, andMyrmeleon formicarius (Neuroptera: Myrmeleontidae).

The thoracic gland of the ant-lionEuroleon nostras was found to contain nerol oxide (1a) and (Z)-6-undecen-2-ol (nostrenol,3) while the speciesGrocus bore contained 10-homonerol oxide (1b) and nostrenol (3). Nerol (2a) and 10-homonerol (2b) were found in a third species,Myrmeleon formicarius. 10-Homonerol, racemic 10-homonerol oxide, and racemic as well as (R)- and (S)-nostrenol were synthesized. The nerol oxide ofE. nostras and the 10-homonerol oxide ofG. bore were found to be racemic, while both species contained optically pure (R)-nostrenol (28).

Influence of N-protecting groups on the stereochemical course of [4+2] cycloaddition of activated dienes to α-amino aldehydes

Abstract Stereochemical aspects of high-pressure [4+2] cycloaddition between 1-methoxybuta-1,3-diene and N -protected α-amino aldehydes are discussed. In addition, the zinc bromide catalyzed cyclocondensation of 1-ethoxy-3-silyloxybuta-1,3-diene and N -protected α-amino aldehydes is studied, at ambient pressure.