Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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    In depth investigation of the metabolism of Nectandra megapotamica chemotypes
    S. Farias, Katyuce de; Delatte, Thierry ; C. de O. Arruda, Rosani do; Alves, Flavio M. ; Silva, Denise B. ; Beekwilder, Jules ; Carollo, Carlos A. - \ 2018
    PLoS ONE 13 (2018)8. - ISSN 1932-6203

    Plants produce a wide range of secondary metabolites. Within a single species, chemotypes can be distinguished by the differences in the composition of the secondary metabolites. Herein, we evaluated Nectandra megapotamica (Spreng.) chemotypes and the balance of different classes of metabolites to verify how significant differences in plant metabolism are regarding chemotypes. We collected N. megapotamica leaves from eight adult plants in two Brazilian states. The essential oils and ethanol/water extracts were analyzed by GC-MS and LC-DAD-MS, respectively. Histochemical tests were performed, as well as chemical analyses of leaves from adaxial and abaxial foliar surfaces of N. megapotamica, and the stereochemistry of α-bisabolol was determined. Two different chemotypes, based on volatile compounds, were identified, distinguished by the presence of isospathulenol, α-bisabolol, β-bisabolene, and (E)-nerolidol for chemotype A, and bicyclogermacrene and elemicin for chemotype B. A stereochemical analysis of chemotype A extract revealed (+)-α-bisabolol enantiomer. Histochemical tests of chemotypes showed similar results and suggested the presence of essential oil in idioblasts stained with the dye NADI. The analyses of chemotype A leaves by GC-MS revealed similar compositions for abaxial and adaxial surfaces, such pattern was also observed for chemotype B. Medium and high polarity metabolites showed high chemical similarities between the chemotypes, highlighting the presence of proanthocyanidins and glycosylated flavonoids (O- and C-glycosides). Thus, N. megapotamica produced distinct volatile chemotypes with highly conserved medium to high polarity compounds. Such results suggest that phenolic derivatives have a basal physiological function, while genetic or environmental differences lead to differentiation in volatile profiles of N. megapotamica.

    Role of Gender in Sali-Nadi (Shanku Raj Kulo) Irrigation Management: A Case Study
    Pun, S. - \ 2001
    In: Challenges to Farmer Managed Irrigation Systems / Upendra Gautam en Shrish Rana. - Kathmandu, Nepal : FMIS Promotion Trust, 2001. - ISBN 999933-328-0-1 - p. 59 - 73.
    Cloning of a DNA region from Bradyrhizobium japonicum encoding pleiotropic functions in heme metabolism and respiration.
    Ramseier, Th.M. ; Kaluza, B. ; Studer, D. ; Gloudemans, T. ; Bisseling, T. ; Jordan, P.M. ; Jones, R.M. ; Zuber, M. ; Hennecke, H. - \ 1989
    Archives of Microbiology 151 (1989). - ISSN 0302-8933 - p. 203 - 212.
    Random and site-directed Tn5-induced mutagenesis of Bradyrhizobium japonicum yielded two mutations, one in strain 2960 and the other in strain 2606::Tn5-20, which mapped close to each other but in separate genes. The corresponding wild-type genes were cloned, and their approximate location on the cloned DNA was determined. Mutant 2960 was Fix- and formed green nodules on soybean, whereas strain 2606::Tn5-20 had ca. 4% of wild-type Fix activity and formed white nodules. Cytochrome oxidase assays (Nadi tests) showed a negative reaction with both mutants, indicating a functional deficiency of cytochrome c or its terminal oxidase or both. However, the mutants grew well under aerobic conditions on minimal media with different carbon sources. Furthermore, mutant 2960 had a reduced activity in hydrogen uptake, was unable to grow anaerobically with nitrate as the terminal electron acceptor and 2960-infected soybean nodules contained little, if any, functional leghemoglobin. Southern blot analysis showed that a B. japonicum heme biosynthesis mutant [strain LO505: O'Brian MR, Kirshbom PM, Maier RJ (1987) Proc Natl Acad Sci USA 84: 8390–8393] had its mutation close to the Tn5 insertion site of our mutant 2606::Tn5-20. This finding, combined with the observed phenotypes, suggested that the genes affected in mutants 2960 and 2606::Tn5-20 were involved in some steps of heme biosynthesis thus explaining the pleiotropic respiratory deficiencies of the mutants. Similar to strain LO505, the mutant 2606::Tn5-20 (but not 2960) was defective in the activity of protoporphyrinogen IX oxidase which catalyzes the penultimate step in the heme biosynthesis pathway. This suggests that one of the two cloned genes may code for this enzyme.
    Binding of small molecules to lipoamide dehydrogenase
    Muiswinkel-Voetberg, H. van - \ 1972
    Landbouwhogeschool Wageningen. Promotor(en): C. Veeger. - Wageningen : Veenman - 66
    katalysatoren - chemische structuur - optische eigenschappen - oxidoreductasen - relaties - katalyse - catalysts - chemical structure - optical properties - oxidoreductases - relationships - catalysis

    The existence of a monomer-dimer equilibrium with lipoamide dehydrogenase is demonstrated. The equilibrium can be shifted to the monomer side at low ionic strength and low pH by removing the phosphate ions by extensive dialysis. At low ionic strength, I : 0.01 and 0.02, the enzyme precipitates while aggregation takes place. This aggregation seems to be due to changes in the activity coefficient of the enzyme. High phosphate concentrations, NADI and high temperatures favor association. Also bringing the enzyme in a more polar environment causes dissociation. Dioxan and 2-chloroethanol are used to decrease the dielectric constant of the buffer solution. Inactivation and dissociation of the enzyme is time- dependent in these solutions. High concentrations of dioxan and 2-chloroethanol cause denaturation and precipitation of the enzyme. High phosphate concentrations stimulate the denaturation and precipitation of the enzyme in dioxan and 2-chloroethanol.

    Dissociation of the enzyme is accompanied by loss in activity and decrease in apparent α-helix content. ORD and CD data show this decrease, however the possibility that this decrease is due to changes in shape and size of the protein molecule cannot be excluded. Fluorescence and CD experiments show that upon dissociation an amino acid, a tryptophan residue, moves to a more polar environment. Also by treating the enzyme with dioxan a tryptophan residue is pertubed.

    Dissociation of the enzyme can also be achieved by treating the enzyme with sodium dodecylsulfate. Hydrophobic and ionic interactions are observed. Binding to the hydrophobic sites, by sodium dodecylsulfate or Tween 80, has no influence on the lipoate activity and on absorption spectrum of the enzyme in the visible- region. Binding to the ionic sites causes loss in lipoate activity and affects the absorption spectrum. From the dependency on the pH and the ionic strength it is concluded that a group of the kind BH += B + H +with a pK value around 6.6 is involved. At high SDS concentrations the binding of FAD to the enzyme is weakened and upon standing for long times the flavin dissociated off.

    Dimerization of the enzyme is favored by NAD +. Binding of NAD +to the enzyme yields a difference spectrum. From these spectral titration curves two pairs of NAD +-binding sites are calculated, the binding site with the highest affinity, K diss = 35 μM is assigned to the regulatory site while the binding site with K diss = 90-110 μM is assigned to the catalytic site. Upon NAD +binding to the regulatory site one proton per FAD is liberated. Comparision of the pH activity curves with computer models shows that the activating effect of NAD +in the lipoate activity can be explained by a shift in pK value of a group from pH 6.4-6.3 to 5.0-4.9 upon NAD +binding. Together with observations in the literature these results suggest that the pK value of a SH-group is shifted to lower pH upon NAD +binding. This SH-group is suggested to be functional in the S -state in the active center.

    Some responses of the root and the shoot of Vida faba plants to water stress.
    Nadi, A.H. El; Brouwer, R. ; Locher, J.T. - \ 1969
    Netherlands Journal of Agricultural Science 17 (1969)2. - ISSN 0028-2928 - p. 133 - 142.
    Some responses of the root and the shoot of Vicia faba plants to water stress
    Nadi, A.H. El; Brouwer, R. ; Locher, J.T. - \ 1969
    Wageningen : [s.n.] (Mededeling / Instituut voor biologisch en scheikundig onderzoek van landbouwgewassen no. 396) - 10
    plantkunde - tuinbonen - bodemkunde - vicia faba - botany - faba beans - soil science - vicia faba
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