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Molecular details of ovalbumin-pectin complexes at the air/water interface: A spectroscopic study

Kudryashova, E.V. (author), Visser, A.J.W.G. (author), van Hoek, A. (author), de Jongh, H.H.J. (author), TNO Kwaliteit van Leven (author)

To stabilize air-water interfaces, as in foams, the adsorption of surface-active components is a prerequisite. An approach to controlling the surface activity of proteins is noncovalent complex formation with a polyelectrolyte in the bulk phase. The molecular properties of egg white ovalbumin in a complex with pectin in the bulk solution and at...

article 2007

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Development of an on-line high performance liquid chromatography detection system for human cytochrome P450 1A2 inhibitors in extracts of natural products

Jeurissen, S.M.F. (author), Claassen, F.W. (author), Havlik, J. (author), Bouwmans, E.E. (author), Cnubben, N.H.P. (author), Sudhölter, E.J.R. (author), Rietjens, I.M.C.M. (author), van Beek, T.A. (author), TNO Kwaliteit van Leven (author)

An on-line HPLC screening method for detection of inhibitors of human cytochrome P450 1A2 in extracts was developed. HPLC separation of extracts is connected to a continuous methoxyresorufin-O-demethylation (MROD) assay in which recombinant human P450 1A2 converts methoxyresorufin to its fluorescent metabolite resorufin. The system was tested...

article 2007

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Binding, tuning and mechanical function of the 4-hydroxy-cinnamic acid chromophore in photoactive yellow protein

TNO Kwaliteit van Leven (author), van der Horst, M.A. (author), Arents, J.C. (author), Kort, R. (author), Hellingwerf, K.J. (author)

The bacterial photoreceptor protein photoactive yellow protein (PYP) covalently binds the chromophore 4-hydroxy coumaric acid, tuning (spectral) characteristics of this cofactor. Here, we study this binding and tuning using a combination of pointmutations and chromophore analogs. In all photosensor proteins studied to date the covalent linkage...

article 2007

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Comprehensive two-dimensional liquid chromatography and hyphenated liquid chromatography to study the degradation of poly(bisphenol A)carbonate

Coulier, L. (author), Kaal, E.R. (author), Hankemeier, T. (author), TNO Kwaliteit van Leven (author)

Size exclusion chromatography (SEC), gradient polymer elution chromatography (GPEC) and liquid chromatography at critical conditions (LC-CC) have been developed and applied to observe chemical changes in poly(bisphenol A)carbonate (PC) due to hydrolytic degradation. Especially LC-CC appeared to be very successful to observe differences in...

article 2005

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Tentative assignment of the potato serine protease inhibitor group as β-II proteins based on their spectroscopic characteristics

Centraal Instituut voor Voedingsonderzoek TNO (author), Pouvreau, L. (author), Gruppen, H. (author), van Koningsveld, G.A. (author), van den Broek, L.A.M. (author), Voragen, A.G.J. (author)

Potato serine protease inhibitor (PSPI) is the most abundant protease inhibitor group in potato tuber. The investigated PSPI isoforms have a highly similar structure at both the secondary and the tertiary level. From the results described, PSPI is classified as a β-II protein based on (1) the presence in the near-UV spectra of sharp peaks,...

article 2004

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Generic solid phase extraction-liquid chromatography-tandem mass spectrometry method for fast determination of drugs in biological fluids

Schellen, A. (author), Ooms, B. (author), van de Lagemaat, D. (author), Vreeken, R. (author), van Dongen, W.D. (author), TNO Voeding (author)

A generic method was developed for the fast determination of a wide range of drugs in serum or plasma. The methodology comprises generic solid-phase extraction, on-line coupled to gradient HPLC with tandem mass spectrometric detection (SPE-LC-MS/MS). The individual components of the SPE-LC-MS/MS system were optimized in an integrated approach to...

article 2003

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Spectrophotometric tool for the determination of the total carboxylate content in proteins; molar extinction coefficient of the enol ester from Woodward's reagent K reacted with protein carboxylates

Kosters, H.A. (author), de Jongh, H.H.J. (author), TNO Voeding (author)

A number of relevant properties of Woodward's reagent K have been determined, such as the stability of the reactant and the optimal reaction conditions of the reactant with protein carboxylates. A Woodward's reagent K stock solution was stable at 4°C for prolonged time, whereas upon storage at 22°C, almost 20% of the reactive compound was lost...

article 2003

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Fourier transform infrared spectroscopy with a sample deposition interface as a quantitative detector in size-exclusion chromatography

Kok, S.J. (author), Arentsen, N.C. (author), Cools, P.J.C.H. (author), Hankemeier, Th. (author), Schoenmakers, P.J. (author), Centraal Instituut voor Voedingsonderzoek TNO (author)

The use of a state-of-the-art commercial solvent-elimination interface for liquid chromatography-infrared spectroscopy is discussed from the perspective of quantitative analysis. The effect of eluent flow-rate is investigated with respect to the homogeneity of the deposit and the trace width along the deposition trace. Low flow-rates (50 μl/min...

article 2002

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Dephosphorylation-induced structural changes in β-casein and its amphiphilic fragment in relation to emulsion properties

Darewicz, M. (author), Dziuba, J. (author), Caessens, P.W.J.R. (author), Gruppen, H. (author), Instituut CIVO-Toxicologie en Voeding TNO (author)

To promote the understanding of the relationship between emulsifying and molecular properties of proteins/peptides, intact β-casein (βCN) and its amphipathic fragment, i.e. βCN (1-105/107) were dephosphorylated. Dephosphorylation was found not to change significantly their emulsifying properties. Since it is known that the structure of proteins...

article 2000

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Cofactor and substrate binding to vanadium chloroperoxidase determined by UV - VIS spectroscopy and evidence for high affinity for pervanadate

TNO Preventie en Gezondheid (author), Renirie, R. (author), Hemrika, W. (author), Piersma, S.R. (author), Wever, R. (author)

The vanadate cofactor in vanadium chloroperoxidase has been studied using UV-VIS absorption spectroscopy. A band is present in the near-UV that is red-shifted as compared to free vanadate and shifts in both position and intensity upon change in pH. Mutation of vanadate binding residues has a clear effect on the spectrum. Substrate-induced...

article 2000

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17α-Ethyl-5β-estrane-3α,17β-diol, a biological marker for the abuse of norethandrolone and ethylestrenol in slaughter cattle

van Puymbroeck, M. (author), Kuilman, M.E.M. (author), Maas, R.F.M. (author), Witkamp, R.F. (author), Leyssens, L. (author), van Miert, A.S.J.P.A.M. (author), Hendriks, L. (author), van der Zande, D.J.M. (author), Adriaensens, P. (author), Jacobs, M.-P. (author), Raus, J. (author), Centraal Instituut voor Voedingsonderzoek TNO (author)

The metabolism of the illegal growth promoter ethylestrenol (EES) was evaluated in bovine liver cells and subcellular fractions of bovine liver preparations. Incubations with bovine microsomal preparations revealed that EES is extensively biotransformed into norethandrolone (NE), another illegal growth promoter. Furthermore, incubations of...

article 1999

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Quantification of perifosine, an alkylphosphocholine anti-tumour agent, in plasma by pneumatically assisted electrospray tandem mass spectrometry coupled with high-performance liquid chromatography

Knebel, N.G. (author), Grieb, S. (author), Winkler, M. (author), Locher, M. (author), van der Vlis, E. (author), Verheij, E.R. (author), Centraal Instituut voor Voedingsonderzoek TNO (author)

An HPLC assay with tandem mass spectrometric detection in the positive-ion Turbo-Ion-Spray((TM)) (TISP) mode for the fast and sensitive determination of perifosine ((I), D-21266) in human plasma was developed, utilising the structural analogue, miltefosine ((II), D-18506), as internal standard. Automated solid-phase extraction of diluted plasma...

article 1999

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Heat-induced conformational changes of Ara h 1, a major peanut allergen, do not affect its allergenic properties

Koppelman, S.J. (author), Bruijnzeel-Koomen, C.A.F.M. (author), Hessing, M. (author), de Jongh, H.H.J. (author)

Ara h 1, a major peanut allergen was isolated, and its structure on secondary, tertiary, and quaternary level at ambient temperature was investigated using spectroscopic and biochemical techniques. Ara h 1 appeared to be a highly structured protein on a secondary level, possesses a clear tertiary fold, and is present as a trimeric complex. Heat...

article 1999

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Rat liver microsomal cytochrome P450-dependent oxidation of 3,5-disubstituted analogues of paracetamol

Bessems, J.G.M. (author), te Koppele, J.M. (author), van Dijk, P.A. (author), van Stee, L.L.P. (author), Commandeur, J.N.M. (author), Vermeulen, N.P.E. (author), Leiden/Amsterdam Ctr. for Drug Res., Division of Molecular Toxicology, Vrije Universiteit, De Boelelaan 1083, 1081 HV Amsterdam, Netherlands Dept. Vasc. Connective Tissue Res TNO Preventie en Gezondheid (author)

1. The cytochrome P450-dependent binding of paracetamol and a series of 3,5-disubstituted paracetamol analogues (R = -F, -Cl, -Br, -I, -C(H)3, -C2H5, -iC3H7) have been determined with β-naphthoflavone (βNF)-induced rat liver microsomes and produced reverse type I spectral changes. K(s,app) varied from 0.14 mM for 3,5-diiC3H7-paracetamol to 2.8...

article 1996

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Enzyme kinetics and substrate selectivities of rat glutathione S-transferase isoenzymes towards a series of new 2-substituted 1-chloro-4-nitrobenzenes

van der Aar, E.M. (author), Buikema, D. (author), Commandeur, J.N.M. (author), te Koppele, J.M. (author), van Ommen, B. (author), van Bladeren, P.J. (author), Vermeulen, N.P.E. (author), Leiden/Amsterdam Ctr. for Drug Res., Department of Pharmacochemistry, Vrije Universiteit, De Boelelaan 1083, 1081 HV, Amsterdam, Netherlands TNO Preventie en Gezondheid TNO Voeding (author)

1. Four different rat glutathione S-transferase (GST) isoenzymes, belonging to three different classes, were examined for their GSH conjugating capacity towards 11 2-substituted 1-chloro-4-nitrobenzene derivatives. Significant differences were found in their enzyme kinetic parameters K(m), k(cat) and k(cat)/K(m). 2. Substrates with bulky...

article 1996

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Differences in cytochrome P450-mediated biotransformation of 1,2- dichlorobenzene by rat and man: Implications for human risk assessment

Hissink, A.M. (author), Oudshoorn, M.J. (author), van Ommen, B. (author), Haenen, G.R.M.M. (author), van Bladeren, P.J. (author)

The oxidative biotransformation of 1, 2-dichlorobenzene (1, 2-DCB) was investigated using hepatic microsomes from male Wistar, Fischer-344 and Sprague-Dawley (SD) rats, phenobarbital (PB)- and isoniazid (ISO) pretreated male Wistar rats and from man. In addition, microsomes from cell lines selectively expressing one cytochrome P450 (P4502E1, 1A1...

article 1996

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In vitro inhibition of rat and human glutathione S-transferase isoenzymes by disulfiram and diethyldithiocarbamate

Ploemen, J.-P.H.T.M. (author), van Iersel, M.L.P.S. (author), Wormhoudt, L.W. (author), Commandeur, J.N.M. (author), Vermeulen, N.P.E. (author), van Bladeren, P.J. (author)

The drug disulfiram (DSF, Antabuse®) has been used in the therapy of alcohol abuse. It is a potent inhibitor of aldehyde dehydrogenase. Its reduced form, diethyldithiocarbamate (DDTC), and further metabolites show similar activities. DSF and DDTC have also been widely used to inhibit mixed-function oxidases. In this study, the reversible...

article 1996

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Characterization of sulfur mustard induced structural modifications in human hemoglobin by liquid chromatography-tandem mass spectrometry

Noort, D. (author), Verheij, E.R. (author), Hulst, A.G. (author), de Jong, L.P.A. (author), Benschop, H.P. (author), Prins Maurits Laboratorium TNO TNO Voeding (author)

In this paper we describe the use of tandem mass spectrometry to identify modified sites in human hemoglobin after in vitro exposure to bis(2- chloroethyl) sulfide (sulfur mustard). Globin isolated from human whole blood which had been exposed to sulfur mustard was degraded with trypsin, and the digests were analyzed by micro LC/MS. Alkylated...

article 1996

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Detection of salicylate and its hydroxylated adducts 2,3- and 2,5-dihydroxybenzoic acids as possible indices for in vivo hydroxyl radical formation in combination with catechol- and indoleamines and their metabolites in cerebrospinal fluid and brain tissue

Sloot, W.N. (author), Gramsbergen, J.B.P. (author), Instituut CIVO-Toxicologie en Voeding TNO (author)

It has been suggested that salicylate (SA) hydroxylation can be used to detect hydroxyl radical formation in vivo. Here we describe a rapid and sensitive HPLC method using ultraviolet absorbance (UV) and electrochemical detection (EC) to detect SA (UV), its hydroxylated adducts 2,3- and 2,5- dihydroxybenzoic acids (DHBA) and catechol in...

article 1995

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Rapid determination of abamectin in lettuce and cucumber by high-performance liquid chromatography

Centraal Instituut voor Voedingsonderzoek TNO (author), Vuik, J. (author)

A rapid, sensitive and reliable method is presented for the determination of trace amounts of abamectin in lettuce and cucumber. Abamectin consists of ≥ 80% avermectin B1a and ≤ 20% avermectin B1b. Vegetables were extracted with ethyl acetate and the extract was purified by solid-phase extraction using Sep-Pak silica cartridges. The purified...

article 1991