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.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Considerations on the shuttle mechanism of FeEDDHA chelates at the soil-root interface in case of Fe deficiency
    Schenkeveld, W.D.C. ; Reichwein, A.M. ; Temminghoff, E.J.M. ; Riemsdijk, W.H. van - \ 2014
    Plant and Soil 379 (2014)1-2. - ISSN 0032-079X - p. 373 - 387.
    strategy i plants - calcareous soil - lolium-perenne - metal uptake - iron uptake - complexes - eddha - chlorosis - isomers - montmorillonite
    A mechanism of action for the performance of Fe chelates as soil-applied fertilizer has been hypothesized by Lindsay and Schwab (J Plant Nutr 5:821-840, 1982), in which the ligand participates in a cyclic process of delivering Fe at the root surface and mobilizing Fe from the soil. This "shuttle mechanism" seems appealing in view of fertilizer efficiency, but little is known about its performance. The chelate FeEDDHA is a commonly used Fe fertilizer on calcareous soils. In this study, the performance of the shuttle mechanism has been examined for FeEDDHA chelates in soil interaction and pot trial experiments. The specificity of EDDHA ligands for chelating Fe from soils of low Fe availability is limited. Experimental support for a shuttle mechanism in soil-plant systems with FeEDDHA was found: specific metal mobilization only occurred upon FeEDDHA-facilitated Fe uptake. The mobilized metals originated at least in part from the root surface instead of the soil. The results from this study support the existence of a shuttle mechanism with FeEDDHA in soil application. If the efficiency of the shuttle mechanism is however largely controlled by metal availability in the bulk soil, it is heavily compromised by complexation of competing cations: Al, Mn and particularly Cu.
    FeEDDHA-facilitated Fe uptake in relation to the behaviour of FeEDDHA components in the soil-plant system as a function of time and dosage.
    Schenkeveld, W.D.C. ; Temminghoff, E.J.M. ; Reichwein, A.M. ; Riemsdijk, W.H. van - \ 2010
    Plant and Soil 332 (2010)1-2. - ISSN 0032-079X - p. 69 - 85.
    strategy i plants - calcareous soil - iron-chlorosis - acid o,p-eddha - pisum-sativum - eddha - bicarbonate - isomers - solubilization - fe(o,o-eddha)
    FeEDDHA products are widely used to prevent and remedy Fe chlorosis in crops grown on calcareous soils. These products consist of a mixture of FeEDDHA components: racemic o,o-FeEDDHA, meso o,o-FeEDDHA, o,p-FeEDDHA and rest-FeEDDHA. The FeEDDHA components differ in physical and chemical properties, and as a consequence also in effectiveness as Fe fertilizer. In order to efficiently match dose, frequency and moment of FeEDDHA application with the Fe requirements of plants, it is important to understand the behaviour of the FeEDDHA components in the soil-plant system as a function of time and dosage, and to relate this behaviour to Fe uptake by plants. These issues have been examined in a pot trial study with soybean plants (Glycine max (L.) Merr. cv Mycogen 5072) grown on calcareous soil from Santomera, Spain. Four FeEDDHA treatments (two compositions, two dosages) were applied prior to the set in of chlorosis. Leaching of FeEDDHA components was prevented. Plant and soil were sampled every week, for six weeks. From one week onward the Fe concentration in the pore water was largely gouverned by racemic and meso o,o-FeEDDHA. The concentration behaviour of the o,o-FeEDDHA isomers underwent two stages: a strong decline within the first week resulting from linear adsorption, and a gradual decline from one week onward. For meso o,o-FeEDDHA, unlike racemic o,o-FeDDHA, the gradual decline could be mathematically well described with an exponential decay function. Soybean plants mainly took up Fe in the progressed vegetative stage (3rd and 4th week) and in the reproductive stage, when the pods were being filled with seeds (6th week). Fe uptake and removal of racemic o,o-FeEDDHA from the soil system display a similar time-trend, whereas the removal of meso o,o-FeEDDHA had a plant-independent character. This indicates the removal of racemic o,o-FeEDDHA is to a larger extent plant-related
    A high intake of conjugated linoleic acid does not affect liver and kidney function tests in healthy human subjects
    Wanders, A.J. ; Leder, L. ; Banga, J.R. ; Katan, M.B. ; Brouwer, I.A. - \ 2010
    Food and Chemical Toxicology 48 (2010)2. - ISSN 0278-6915 - p. 587 - 590.
    body-fat mass - overweight humans - obese humans - cla - mice - supplementation - metabolism - glucose - isomers - profile
    Conjugated linoleic acid (CIA) is consumed widely as a supplement. It Causes hepatomegaly in animals, but toxicological data in humans are limited We therefore studied the effect of a high daily intake of CIA on liver and kidney function in healthy subjects. Twenty Subjects received 14 6 g cis-9,trans-11 CIA and 4.7 g trans-10,cis-12 CIA isomers a day for 3 weeks. Liver and kidney function was measured at 0, 3, 7, 10, 16, and 21 days. Mean values of all tests remained within normal limits Lactate dehydrogenase (mean +/- SD) increased from 290 9 +/- 43.6 to 322.5 +/- 60.7 U/L (p = 0.04) on day 21. One subject exceeded the tipper limit of normal of 450 U/L on day 21. to 472 U/L and another showed an isolated elevation to 555 U/L on day 7. gamma-Glutamyltranspeptidase increased from 12 1 +/- 5 9 to 13 5 +/- 6.2 U/L (p = 0.002) No one exceeded the upper limit of 50 U/L for men and 40 U/L for women A daily intake of 19.3 g CIA for 3 weeks does not produce clinically relevant effects on markers of liver and kidney function in healthy volunteers. (C) 2009 Elsevier Ltd. All rights reserved.
    Automated procedure for candidate compound selection in GCMS metabolomics based on prediction of Kovats retention index
    Mihaleva, V.V. ; Verhoeven, H.A. ; Vos, C.H. de; Hall, R.D. ; Ham, R.C.H.J. van - \ 2009
    Bioinformatics 25 (2009)6. - ISSN 1367-4803 - p. 787 - 794.
    volatile organic-compounds - variable selection - genetic algorithms - mass-spectrometry - descriptors - strategy - isomers - variety - cancer - time
    Motivation: Matching both the retention index (RI) and the mass spectrum of an unknown compound against a mass spectral reference library provides strong evidence for a correct identification of that compound. Data on retention indices are, however, available for only a small fraction of the compounds in such libraries. We propose a quantitative structure - retention index model that enables the ranking and filtering of putative identifications of compounds for which the predicted RI falls outside a predefined window. Results: We constructed multiple linear regression and support vector regression (SVR) models using a set of descriptors obtained with a genetic algorithm as variable selection method. The SVR model is a significant improvement over previous models built for structurally diverse compounds as it covers a large range (360 to 4100) of RI values and gives better prediction of isomer compounds. The hit list reduction varied from 41% to 60% and depended on the size of the original hit list. Large hit lists were reduced to a greater extend compared to small hit lists.
    Effect of dietary starch or micro algae supplementation on rumen fermentation and milk fatty acid composition of dairy cows
    Boeckaert, C. ; Vlaeminck, B. ; Dijkstra, J. ; Issa-Zacharia, A. ; Nespen, T. van; Straalen, W. van; Fievez, V. - \ 2008
    Journal of Dairy Science 91 (2008). - ISSN 0022-0302 - p. 4714 - 4727.
    conjugated linoleic-acid - in-vitro examination - fish-oil - composition responses - docosahexaenoic acid - nutritional quality - biohydrogenation - isomers - trans - persistency
    Two experiments with rumen-fistulated dairy cows were conducted to evaluate the effects of feeding docosahexaenoic acid (DHA; C22:6 n-3)-enriched diets or diets provoking a decreased rumen pH on milk fatty acid composition. In the first experiment, dietary treatments were tested during 21-d experimental periods in a 4 x 4 Latin square design. Diets included a control diet, a starch-rich diet, a bicarbonate-buffered starch-rich diet, and a diet supplemented with DHA-enriched micro algae [Schizochytrium sp., 43.0 g/kg of dry matter intake (DMI)]. Algae were supplemented directly through the rumen fistula. The total mixed ration consisted of grass silage, corn silage, soybean meal, and a standard or glucogenic concentrate. The glucogenic and buffered glucogenic diet had no effect on rumen fermentation and milk fatty acid composition because, unexpectedly, no reduced rumen pH was detected. The algae diet had no effect on rumen pH but provoked decreased butyrate and increased isovalerate molar proportions in the rumen. In addition, algae supplementation affected rumen biohydrogenation of linoleic and linolenic acid as reflected in the modified milk fatty acid composition toward increased conjugated linoleic acid (CLA) cis-9 trans-11, CLA trans-9 cis-11, C18:1 trans-10, C18:1 trans-11, and C22:6 n-3 concentrations. Concomitantly, on average, a 45% decrease in DMI and milk yield was observed. Based on these drastic and impractical results, a second animal experiment was performed for 20 d in which 9.35 g/kg of total DMI of algae were incorporated in the concentrate and supplemented to 3 rumen-fistulated cows. Algae concentrate feeding increased rumen pH, which was associated with decreased rumen short-chain fatty acid concentrations. Moreover, a different shift in rumen short-chain fatty acid proportions was observed compared with the first experiment because molar proportions of butyrate, isobutyrate, and isovalerate increased, whereas acetate molar proportion decreased. The milk fatty acid profile changed as in experiment 1. However, the decrease in DMI and milk yield was less pronounced (on average 10%) at this algae supplementation level, whereas milk fat percentage decreased from 47.9 to 22.0 g/kg of milk after algae treatment. In conclusion, an algae supplementation level of about 10 g/kg of DMI proved effective to reduce the milk fat content and to modify the milk fatty acid composition toward increased CLA cis-9 trans-11, C18:1 trans, and DHA concentrations.
    High rate treatment of terephthalic acid production wastewater in a two-stage anaerobic bioreactor
    Kleerebezem, R. ; Beckers, J. ; Pol, L.W.H. ; Lettinga, G. - \ 2005
    Biotechnology and Bioengineering 91 (2005)2. - ISSN 0006-3592 - p. 169 - 179.
    4-methylbenzoic acid - baffled reactor - degradation - performance - inhibition - digestion - industry - isomers - sludge
    The feasibility was studied of anaerobic treatment of wastewater generated during purified terephthalic acid (PTA) production in two-stage upflow anaerobic sludge blanket (UASB) reactor system. The artificial influent of the system contained the main organic substrates of PTA-wastewater: acetate, benzoate, and terephthalate. Three parallel operated reactors were used for the second stage, and seeded with a suspended terephthalate degrading culture, with and without additional methanogenic granular sludge (two different types). The first stage UASB-reactor was seeded with methanogenic granular sludge. Reactors were operated at 37 degrees C and pH 7. During the first 300 days of operation a clear distinction between the biomass grown in both reactor stages was obtained. In the first stage, acetate and benzoate were degraded at a volumetric loading rate of 40 g-COD/L (.) day at a COD-removal efficiency of 95% within the first 25 days of operation. No degradation of terephthalate was obtained in the first stage during the first 300 days of operation despite operation of the reactor at a decreased volumetric loading rate with acetate and benzoate of 9 g-COD/L (.) day from day 150. Batch incubation of biomass from the reactor with terephthalate showed that the lag-phase prior to terephthalate degradation remained largely unchanged, indicating that no net growth of terephthalate degrading biomass occurred in the first stage reactor. From day 300, however, terephthalate degradation was observed in the first stage, and the biomass in this reactor could successfully be enriched with terephthalate degrading biomass, resulting in terephthalate removal capacities of 15 g-COD/L (.) day. Even though no single reason could be identified why (suddenly) terephthalate degradation was obtained after such a long period of operation, it is suggested that the solid retention time as well the prevailing reactor concentrations acetate and benzoate may have played an important role. From day 1 of operation, terephthalate was degraded in the second stage. In presence of methanogenic granular biomass, high terephthalate removal capacities were obtained in these reactors (15 g-COD/L (.) day) after approximately 125 days of operation. From the results obtained it is concluded that terephthalate degradation is the bottleneck during anaerobic treatment of PTA-wastewater. Pre-removal of acetate and benzoate in staged bioreactor reduces the lag-phase prior to terephthalate degradation in latter stages, and enables high rate treatment of PTA-wastewater. (c) 2005 Wiley Periodicals, Inc.
    Reductive dechlorination of B-hexachlorocyclohexane (B-HCH) by a Dehalobacter species in coculture with a Sedimentibacter species
    Doesburg, W.C.J. van; Eekert, M.H.A. van; Middeldorp, P.J.M. ; Balk, M. ; Schraa, G. ; Stams, A.J.M. - \ 2005
    FEMS microbiology ecology 54 (2005)1. - ISSN 0168-6496 - p. 87 - 95.
    gradient gel-electrophoresis - 16s ribosomal-rna - microbial dehalorespiration - gamma-hexachlorocyclohexane - enrichment culture - gen. nov. - degradation - alpha - bacterium - isomers
    An anaerobic coculture was enriched from a hexachlorocyclohexane (HCH) polluted soil. The coculture reductively dechlorinates the ß-HCH isomer to benzene and chlorobenzene in a ratio of 0.5¿2 depending on the amount of ß-HCH degraded. The culture grows with H2 as electron donor and ß-HCH as electron acceptor, indicating that dechlorination is a respiratory process. Phylogenetic analysis indicated that the coculture consists of two bacteria that are both related to gram-positive bacteria with a low G + C content of the DNA. One bacterium was identified as a Dehalobacter sp. This bacterium is responsible for the dechlorination. The other bacterium was isolated and characterized as being a Sedimentibacter sp. This strain is not able to dechlorinate ß-HCH. The Dehalobacter sp. requires the presence of Sedimentibacter for growth and dechlorination, but the function of the latter bacterium is not clear. This is the first report on the metabolic dechlorination of ß-HCH by a defined anaerobic bacterial culture.
    Ultratraces of carotenes in tomato purees : HPLC-TLS study
    Luterotti, S. ; Markovic, K. ; Franko, M. ; Bicanic, D.D. ; Vahcic, N. ; Doka, O. - \ 2003
    Review of Scientific Instruments 74 (2003)1. - ISSN 0034-6748 - p. 684 - 686.
    performance liquid-chromatography - thermal lens detection - trans-beta-carotene - ultrasensitive determination - lycopene - isomers - oxygen
    The present study was designed to provide information about (i) the profile of carotene pigments and (ii) trace quantities of lycopene and -carotene left in tomato purées. The ultrasensitive method comprising HPLC and thermal lens spectrometric (TLS) detection enabled us to detect as low as 0.3 and 1.1 ng ml¿1 lycopene and -carotene in purée extracts, respectively. Total concentration of -carotene and lycopene (varying from 3 to 170 ng g¿1) in the examined tomato purées may serve as an indicator of the carotene-specific antioxidative capacity of these products. Although conventional spectrophotometry can be used to rapidly assess the quality of products derived from tomatoes, a highly sensitive and selective method such as HPLC-TLS is needed for reliable analyses of samples such as, for example, those subjected to inappropriate storage and/or handling
    Het gehalte aan hexachloorcyclohexaan isomeren (HCH's) en heptachloor in tarwegries/ grint/zemelen
    Mazijk, R.J. van; Munsteren, A.J. van; Roos, A.H. ; Tuinstra, L.G.M.Th. - \ 1982
    Wageningen : RIKILT (Verslag / RIKILT 82.56) - 3
    hch - gechloreerde koolwaterstofinsecticiden - heptachloor - cyclodieeninsecticiden - isomeren - graanbijproducten - bolletjes - besmetting - hch - organochlorine insecticides - heptachlor - cyclodiene insecticides - isomers - cereal byproducts - pellets - contamination
    Inventarisatie van de contaminatie van tarwegries/grint/zemelen met HCH's over de periode november 1978-juli 1981 en heptachloor over de periode augustus 1980-juli 1981.
    The reactivity of substituted purines in strongly basic medium : the occurrence of geometrical isomerism in the anions of aromatic amino compounds
    Kos, N.J. - \ 1981
    Landbouwhogeschool Wageningen. Promotor(en): H.C. van der Plas. - Wageningen : Kos - 107
    aminen - azinen - chemische reacties - chemie - kinetica - purinen - pyridazinen - pyrimidines - stereochemie - isomeren - heterocyclische verbindingen - amines - azines - chemical reactions - chemistry - kinetics - purines - pyridazines - pyrimidines - stereochemistry - isomers - heterocyclic compounds
    In this thesis two subjects are described: a. the amination of substituted purines by potassium amide in liquid ammonia and b. the occurrence of geometri cal isomerism in the anions of aromatic amino compounds.

    It is shown that the first step in the amination of purines, being present as anions under these strongly basic conditions, is the formation of a σ-adduct as position 6 to give a 6-amino-1,6-dihydropurinide. If position 6 is occupied by a blocking group an attack at position 2 or 8 does not occur. The further reaction course depends on the nature of the substituents and their position in the purine ring. i. If a leaving group (Cl,SCH 3 ) is present at the same position where the amide ion has attacked, this substituent is expelled (S N (AE) mechanism). In case no leaving group is present a Chichibabin amination occurs due to expulsion of a hydride ion from position 6 (this reaction is described in Chapter 2).

    The Chichibabin amination can also occur at position 6 when a leaving group (Cl,SCH 3 ) is present at position 8. ii. In the last-mentioned system a tele substitution is possible besides the S N (AE) reaction. This reaction is exemplified in the conversion of 8-chloropurine into adenine (formed besides 8-chloro adenine). The σ-adduct at position 6 is protonated at position 8, after which dehydrohalogenation occurs (S N (AE) tele , see Chapter 3). iii. If a leaving group is present at position 2 (Cl,F,SCH 3 ) the σ-adduct at position 6 undergoes ring opening of the pyrimidine ring with expulsion of the leaving group. The resulting imidazole derivative undergoes ring closure to give a 2-aminopurine. This type of reaction is referred to as an S N (ANRORC) mechanism and is described in Chapter 4.

    It has been established that in an S N (AE) mechanism the second step, involving the expulsion of the leaving group, is fast; the intermediary a-adduct cannot be observed. However, in the Chichibabin amination, tele amination and reaction according to the S N (ANRORC) mechanism, the second step is slow and therefore the σ-adduct can be observed by low temperature NMR spectroscopy.

    In Chapter 5 a new method is presented for the reductive removal of amino and alkylamino groups from position 6 of 9-substituted purines with sodium in liquid ammonia. The reaction involves reduction of the N(1) - C(6) bond, followed by elimination. This reaction is of special interest since the alternative method for the removal of amino groups i.e. the diazotization cannot be used with alkylamino groups. Therefore this new method is especially useful for the deamination of 6-(alkylamino)-9-substituted purines.

    In the last part of this thesis the occurrence of geometrical isomerism in the anions of aromatic amino compounds in liquid ammonia containing potassium amide is described. It is shown that this phenomenon occurs even in anilines, where the rotational barrier will be lower than in azaaromatic systems. This is confirmed by the occurrence of coalescence with increasing temperature (Chapter 6). The 1H and 13C NMR spectra of the anions of aminopyridines, aminopyrimidines and N-methylaminopyridines are assigned to the syn - and anti isomers. It has been revealed that in all these anions the ortho hydrogen atom in the s yn position relative to the lone pair resonates at a lower field than the hydrogen atom in the anti position. For the 13C NMR shifts of the ortho carbon atoms it was found that in the anions of N-methylaminopyridines the ortho carbon atom in the syn position relative to the lone pair resonates at lower field than the ortho carbon atom in the anti position. In the anions of aminopyridines and aminopyrimidines this phenomenon is reversed. We have also shown that the presence of a methyl group ortho to the anionic amino group causes a preference for the isomer, in which the proton of the NH group is in a syn position relative to the methyl group. This is explained in terms of the electron pair being "larger" than a proton, but it is possible that the preferred isomer is also stabilized by a better solvation and by an electronical effect.

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