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排序方式: 共有374条查询结果,搜索用时 31 毫秒
21.
Van Haandel MJ Claassens MM Van der Hout N Boersma MG Vervoort J Rietjens IM 《Biochimica et biophysica acta》1999,1435(1-2):22-29
For the first time saturating overall k(cat) values for horseradish peroxidase (HRP) catalysed conversion of phenols and anilines are described. These k(cat) values correlate quantitatively with calculated ionisation potentials of the substrates. The correlations for the phenols are shifted to higher k(cat) values at similar ionisation potentials as compared to those for anilines. (1)H-NMR T(1) relaxation studies, using 3-methylphenol and 3-methylaniline as the model substrates, revealed smaller average distances of the phenol than of the aniline protons to the paramagnetic Fe(3+) centre in HRP. This observation, together with a possibly higher extent of deprotonation of the phenols than of the anilines upon binding to the active site of HRP, may contribute to the relatively higher HRP catalysed conversion rates of phenols than of anilines. 相似文献
22.
Soffers AE Van Haandel MJ Boersma MG Tyrakowska B Laane C Rietjens IM 《Free radical research》1999,30(3):233-240
Quantitative structure activity relationships (QSARs) are described for the antioxidant activity of series of all-trans carotenoids. The antioxidant activity of the carotenoids is characterised by literature data for (i) their relative ability to scavenge the ABTS·+ radical cation, reflected by the so-called trolox equivalent antioxidant capacity (TEAC) value, (ii) their relative rate of oxidation by a range of free radicals, or (iii) their capacity to inhibit lipid peroxidation in multilamellar liposomes, leading to a decrease in formation of thiobarbituric acid reactive substances (TBARS). All these antioxidant values for radical scavenging action correlate quantitatively with computer-calculated ionisation potentials of the carotenoids. These correlations are observed both when the ionisation potential is calculated as the negative of the energy of the highest occupied molecular orbital (-E(HOMO)) of the molecule, or as the relative change in heat of formation (ΔΔHF) upon the one-electron oxidation of the carotenoids.
The calculations provide a theoretical assay able to characterise the intrinsic electron donating capacity of an antioxidant, in hydrophilic, hydrophobic or artificial membrane environment. 相似文献
The calculations provide a theoretical assay able to characterise the intrinsic electron donating capacity of an antioxidant, in hydrophilic, hydrophobic or artificial membrane environment. 相似文献
23.
Tyrakowska B Soffers AE Szymusiak H Boeren S Boersma MG Lemańska K Vervoort J Rietjens IM 《Free radical biology & medicine》1999,27(11-12):1427-1436
The influence of pH, intrinsic electron donating capacity, and intrinsic hydrogen atom donating capacity on the antioxidant potential of series of hydroxy and fluorine substituted 4-hydroxybenzoates was investigated experimentally and also on the basis of computer calculations. The pH-dependent behavior of the compounds in the TEAC assay revealed different antioxidant behavior of the nondissociated monoanionic form and the deprotonated dianionic form of the 4-hydroxybenzoates. Upon deprotonation the radical scavenging ability of the 4-hydroxybenzoates increases significantly. For mechanistic comparison a series of fluorobenzoates was synthesized and included in the studies. The fluorine substituents were shown to affect the proton and electron donating abilities of 4-hydroxybenzoate in the same way as hydroxyl substituents. In contrast, the fluorine substituents influenced the TEAC value and the hydrogen atom donating capacity of 4-hydroxybenzoate in a way different from the hydroxyl moieties. Comparison of these experimental data to computer-calculated characteristics indicates that the antioxidant behavior of the monoanionic forms of the 4-hydroxybenzoates is not determined by the tendency of the molecule to donate an electron, but by its ability to donate a hydrogen atom. Altogether, the results explain qualitatively and quantitatively how the number and position of OH moieties affect the antioxidant behavior of 4-hydroxybenzoates. 相似文献
24.
Boersma MG Solyanikova IP Van Berkel WJ Vervoort J Golovleva LA Rietjens IM 《Journal of industrial microbiology & biotechnology》2001,26(1-2):22-34
Of all NMR-observable isotopes 19F is the one most convenient for studies on the biodegradation of environmental pollutants and especially for fast initial
metabolic screening of newly isolated organisms. In the past decade we have identified the 19F NMR characteristics of many fluorinated intermediates in the microbial degradation of fluoroaromatics including especially
fluorophenols. In the present paper we give an overview of results obtained for the initial steps in the aerobic microbial
degradation of fluorophenols, i.e. the aromatic hydroxylation to di-, tri- or even tetrahydroxybenzenes ultimately suitable
as substrates for the second step, ring cleavage by dioxygenases. In addition we present new results from studies on the identification
of metabolites resulting from reaction steps following aromatic ring cleavage, i.e. resulting from the conversion of fluoromuconates
by chloromuconate cycloisomerase. Together the presented data illustrate the potential of the 19F NMR technique for (1) fast initial screening of biodegradative pathways, i.e. for studies on metabolomics in newly isolated
microorganisms, and (2) identification of relatively unstable pathway intermediates like fluoromuconolactones and fluoromaleylacetates.
Journal of Industrial Microbiology & Biotechnology (2001) 26, 22–34.
Received 20 April 2000/ Accepted in revised form 22 May 2000 相似文献
25.
Fokkema MR Smit EN Martini IA Woltil HA Boersma ER Muskiet FA 《Prostaglandins, leukotrienes, and essential fatty acids》2002,67(5):345-356
BACKGROUND: Early suspicion of essential fatty acid deficiency (EFAD) or omega3-deficiency may rather focus on polyunsaturated fatty acid (PUFA) or long-chain PUFA (LCP) analyses than clinical symptoms. We determined cut-off values for biochemical EFAD, omega3-and omega3/22:6omega3 [docosahexaenoic acid (DHA)]-deficiency by measurement of erythrocyte 20:3omega9 (Mead acid), 22:5omega6/20:4omega6 and 22:5omega6/22:6omega3, respectively. METHODS: Cut-off values, based on 97.5 percentiles, derived from an apparently healthy omnivorous group (six Dominica breast-fed newborns, 32 breast-fed and 27 formula+LCP-fed Dutch low-birth-weight infants, 31 Jerusalem infants, 33 Dutch 3.5-year-old infants, 69 omnivorous Dutch adults and seven Dominica mothers) and an apparently healthy group with low dietary LCP intake (81 formula-fed Dutch low-birth-weight infants, 12 Dutch vegans). Cut-off values were evaluated by their application in an EFAD suspected group of 108, mostly malnourished, Pakistani children, three pediatric patients with chronic fat-malabsorption (abetal-ipoproteinemia, congenital jejunal and biliary atresia) and one patient with a peroxisomal beta-oxidation disorder. RESULTS: Erythrocyte 20:3omega9, 22:5omega6/20:4omega6 and 22:5omega6/22:6omega3 proved age-dependent up to 0.2 years. Cut-off values for ages above 0.2 years were: 0.46mol% 20:3omega9 for EFAD, 0.068mol/mol 22:5omega6/20:4omega6 for omega3-deficiency, 0.22mol/mol 22:5omega6/22:6omega3 for omega3/DHA-marginality and 0.48mol/mol 22:5omega6/22:6omega3 for omega3/DHA-deficiency. Use of RBC 20:3omega9 and 22:5omega6/20:4omega6 cut-off values identified 20.4% of the Pakistani subjects as EFAD+omega3-deficient, 12.9% as EFAD+omega3-sufficient, 38.9% as EFA-sufficient+omega3-deficient and 27.8% as EFA-sufficient+omega3-sufficient. The patient with the peroxisomal disorder was classified as EFA-sufficient, omega3-sufficient (based on RBC 22:5omega6/20:4omega6) and omega3/DHA-deficient (based on RBC 22:5omega6/22:6omega3). The three other pediatric patients were classified as EFAD, omega3-deficient and omega3/DHA-deficient. CONCLUSION: Use of the combination of the present cut-off values for EFA, omega3 and omega3/DHA status assessment, as based on 97.5 percentiles, may serve for PUFA supplement intervention until better concepts have emerged. 相似文献
26.
Childhood celiac disease may lead to a failure of statural growth. After institution of a gluten-free diet most patients exhibit catch-up growth. Catch-up growth is a remarkable phenomenon characterized by a supranormal height velocity. One of the hypothetical mechanisms of catch-up growth is that an increased activity of the somatotrophic axis is involved. In order to provide further insight in the physiology of catch-up growth, auxological and endocrine changes were prospectively studied in 28 children with newly diagnosed celiac disease. The results demonstrate a malnutrition-like state of the somatotrophic axis at the time of diagnosis and a rapid recovery of this axis towards normal functioning after institution of the gluten-free diet. Although several correlations between these endocrine alterations and auxological parameters were detected, it is questionable whether the endocrine changes are the driving force behind catch-up growth. 相似文献
27.
A preliminary evaluation of a new enzyme immunoassay to detect Chlamydia pneumoniae-specific antibodies 总被引:3,自引:0,他引:3
Ossewaarde JM Tuuminen T Boersma WG Sandström M Palomäki P Boman J 《Journal of microbiological methods》2000,43(2):117-125
New enzyme immunoassays (EIAs) for determination of specific IgG, IgA, and IgM antibody titers to Chlamydia pneumoniae were evaluated independently in three research laboratories. Specificity of the EIAs was enhanced by removing LPS from the chlamydial antigen. The performance of these EIAs was evaluated in comparison with the microimmunofluorescence (MIF) test using specimens from: (i) a group of adult patients with community-acquired pneumonia (CAP) previously diagnosed as having an acute chlamydial infection by the complement fixation test or the whole inclusion fluorescence test; (ii) from a group of adult patients with acute respiratory tract infections; and (iii) from a group of young children consecutively presenting with acute respiratory tract infections. The MIF test and the EIAs detected acute infections in paired serum specimens from 12 of 14 patients from the first group. Eleven of these 12 patients were positive in both tests. The MIF test detected seven acute infections in single convalescence serum specimens from eight patients. Two of these were also positive in the EIAs. Paired serum specimens from the second group of adult patients (n=12) were collected during an epidemic of C. pneumoniae. The EIAs detected six acute infections. The MIF test detected two additional patients with acute infections. From the group of young children (n=30), the EIAs detected two patients with acute infections. Our conclusion from this preliminary evaluation is that these EIAs could be useful for laboratory diagnosis of acute C. pneumoniae infections. Comprehensive prospective studies should provide suitable data to calculate the sensitivity, specificity, and predictive values. 相似文献
28.
19F Nuclear Magnetic Resonance as a Tool To Investigate Microbial Degradation of Fluorophenols to Fluorocatechols and Fluoromuconates 总被引:1,自引:0,他引:1
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Marelle G. Boersma Tatiana Y. Dinarieva Wouter J. Middelhoven Willem J. H. van Berkel Joel Doran Jacques Vervoort Ivonne M. C. M. Rietjens 《Applied microbiology》1998,64(4):1256-1263
A method was developed to study the biodegradation and oxidative biodehalogenation of fluorinated phenols by 19F nuclear magnetic resonance (NMR). Characterization of the 19F NMR spectra of metabolite profiles of a series of fluorophenols, converted by purified phenol hydroxylase, catechol 1,2-dioxygenase, and/or by the yeast-like fungus Exophiala jeanselmei, provided possibilities for identification of the 19F NMR chemical shift values of fluorinated catechol and muconate metabolites. As an example, the 19F NMR method thus defined was used to characterize the time-dependent metabolite profiles of various halophenols in either cell extracts or in incubations with whole cells of E. jeanselmei. The results obtained for these two systems are similar, except for the level of muconates observed. Altogether, the results of the present study describe a 19F NMR method which provides an efficient tool for elucidating the metabolic pathways for conversion of fluorine-containing phenols by microorganisms, with special emphasis on possibilities for biodehalogenation and detection of the type of fluorocatechols and fluoromuconates involved. In addition, the method provides possibilities for studying metabolic pathways in vivo in whole cells. 相似文献
29.
Ben C Collins Ludovic CJ Gillet Lorenz C Blum Lin‐Yang Cheng Olga Vitek Jeppe Mouritsen Genevieve Lachance Tim D Spector Emmanouil T Dermitzakis Ruedi Aebersold 《Molecular systems biology》2015,11(2)
The degree and the origins of quantitative variability of most human plasma proteins are largely unknown. Because the twin study design provides a natural opportunity to estimate the relative contribution of heritability and environment to different traits in human population, we applied here the highly accurate and reproducible SWATH mass spectrometry technique to quantify 1,904 peptides defining 342 unique plasma proteins in 232 plasma samples collected longitudinally from pairs of monozygotic and dizygotic twins at intervals of 2–7 years, and proportioned the observed total quantitative variability to its root causes, genes, and environmental and longitudinal factors. The data indicate that different proteins show vastly different patterns of abundance variability among humans and that genetic control and longitudinal variation affect protein levels and biological processes to different degrees. The data further strongly suggest that the plasma concentrations of clinical biomarkers need to be calibrated against genetic and temporal factors. Moreover, we identified 13 cis‐SNPs significantly influencing the level of specific plasma proteins. These results therefore have immediate implications for the effective design of blood‐based biomarker studies. 相似文献
30.
Nermina Buljubasic K. Martijn Akkerhuis Sanneke P. M. de Boer Jin M. Cheng Hector M. Garcia-Garcia Mattie J. Lenzen Rohit M. Oemrawsingh Linda C. Battes Melissa Rijndertse Evelyn Regar Patrick W. Serruys Robert-Jan van Geuns Eric Boersma Isabella Kardys 《PloS one》2015,10(10)