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PubMed2006

Electrochemical oxidation of benzene on boron-doped diamond electrodes.

This work presents an electrochemical investigation of the benzene oxidation process in aqueous solution on boron-doped diamond (BDD) electrodes. Additionally, in order to determine the main products generated during the oxidation process, electrolysis and high performance liquid chromatography experiments were carried out. The complete degradation of this compound was performed aiming to a further application in waste water treatment. The cyclic voltammetry studies indicate that benzene is irreversibly oxidized in acid medium (H2SO4 0.5 M) on the BDD electrode surface at 2.0 V versus Ag/AgCl in a diffusion controlled process. During the cycling, other products are generated, and a pair of peaks was observed that can be associated with the oxi-reduction of anyone of the following species: hydroquinone, benzoquinone, resorcinol or catechol. The electrolysis experiments were carried out at 2.4 and 2.5 V on the BDD electrode surface in a solution containing 1x10(-2) M of benzene (below the saturation concentration in aqueous solution), for 3 and 5 h, respectively. The main products measured were: hydroquinone, resorcinol, p-benzoquinone, catechol and phenol. The complete electrochemical benzene degradation was performed in the electrolysis experiments using a rotating BDD disc electrode (2.5 V for 5 h) and the main products detected were all measured at concentrations lower than 10(-5) M in this condition. The boron-doped diamond electrode had proved to be a valuable tool for the electrochemical degradation of the benzene, a very stable chemical compound.

Benzene↗
PubMed2005

Structure-activity relationship of the tocopherol-regeneration reaction by catechins.

The reaction rates (k(r)) of 5,7-diisopropyl-tocopheroxyl radical (Toc) with catechins (epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), epigallocatechin gallate (EGCG)) and related compounds (methyl gallate (MG), 4-methylcatechol (MC), and 5-methoxyresorcinol (MR)) have been measured by stopped-flow spectrophotometer. The k(r) values increased in the order of MR < < MG < EC < MC approximately ECG < EGC < EGCG in ethanol and 2-propanol/H(2)O (5/1, v/v) solutions, indicating that the reactivity of the OH groups in catechins increased in the order of resorcinol A-ring < < gallate G-ring < catechol B-ring < pyrogallol B-ring. The catechins which have lower oxidation potentials show higher reactivities. The rate constants for catechins in micellar solution showed notable pH dependence with one or two peaks around pH 9-11, because of the dissociation of various phenolic hydroxyl protons in catechins. The structure-activity relationship in the free-radical-scavenging reaction by catechins has been clarified by the detailed analyses of the pH dependence of k(r) values. The reaction rates increased remarkably with increasing the anionic character of catechins, that is, the electron-donating capacity of catechins. The mono anion form at catechol B-and resorcinol A-rings and dianion form at pyrogallol B-and gallate G-rings show the highest activity for free-radical-scavenging. It was found that catechins (EC, ECG, EGC, and EGCG) have activity similar to or higher than that of vitamin C in vitamin E regeneration at pH 7-12 in micellar solution.

Catechin↗
PubMed2001

Occurrence of gangliosides in the common squid and pacific octopus among protostomia.

Acidic lipids from tissues of the common squid Todarodes pacificus and the pacific octopus Octopus vulgaris were characterized. Hepatopancreatic tissues of both animals had complex compositions of resorcinol-positive acidic lipids, many of which became reactive with cholera toxin B subunit and anti-G(M1) antibody after in situ treatment with sialidase on TLC. One of the major acidic lipids in squid tissue was isolated and examined for its structure. This acidic lipid was identified to be the ganglioside G(D1a) based upon the susceptibility to sialidases of different substrate specificity, characterization of reaction products, and electrospray ionization-mass spectrometry of the lipid. Hepatopancreatic tissues of squid and octopus also contained acidic lipids that reacted with A2B5, a monoclonal antibody specific to c-series gangliosides. Cerebral ganglia of both animals expressed resorcinol-positive acidic lipids, though their compositional patterns differed from the hepatopancreatic tissues. N-Acetylneuraminic acid was identified as the main species in lipid-bound sialic acid in both tissues. The contents of lipid-bound sialic acid in cerebral ganglia were significantly lower than those of hepatopancreatic tissues in both animals. The present study presents the first evidence for the occurrence of gangliosides in protostomia.

Animals↗
PubMed2002

Nonlinear function retention model in weak acid anion chromatography.

A nonlinear function retention model for anion chromatography is developed, which is able to predict the retention behavior of polyvalent weak acid anions using sodium hydroxide as eluent. The relationship between the retention factors of phosphate and resorcinol and eluent concentration was studied with sodium hydroxide as the eluent. Both retention factors of the analyte anions first increase then decrease with the increase of sodium hydroxide concentration. The estimated values agree with the measured values with correlation coefficients for phosphate and resorcinol of 0.9920 and 0.9916, respectively, which shows the nonlinear function model is a useful addition to the theory of anion chromatography. The model is able to optimize the separation of polyvalent weak acid anions.

Acids↗
PubMed2000

Interlaboratory comparison of the CB6F1-Tg rasH2 rapid carcinogenicity testing model.

Several genetically engineered mouse models are currently being examined for potential use in cancer hazard identification. We have undertaken an interlaboratory comparison of the performance of the CB6F1-Tg rasH2 transgenic mouse in cancer bioassays concurrently conducted in the United States and Japan. Chemicals selected for study included known human carcinogens (melphalan and cyclosporin A) and known rodent carcinogens (p-cresidine and vinyl carbamate) tested at carcinogenic doses, and non-carcinogens (p-anisidine and resorcinol) tested at appropriate high doses. Because of abdominal adhesions caused by the intraperitoneal dosing vehicle, melphalan was excluded from the study results. The remaining five studies showed similar results between the two laboratories conducting each study. Vinyl carbamate gave the strongest positive response inducing lung adenomas and carcinomas and splenic hemangiosarcomas. p-Cresidine was considered positive for urinary bladder transitional neoplasia. Cyclosporin A, p-anisidine, and resorcinol were negative in all studies. Although only five chemicals were successfully tested in this interlaboratory comparison, there was good concordance in outcome for the strong carcinogens and for the non-carcinogens. Successful testing of chemicals with less carcinogenic potential may require modifications in study design to include more animals and longer study duration.

Adenoma↗
PubMed1981

5,7-Dihydroxy-2-aminotetralin derivatives: synthesis and assessment of dopaminergic and adrenergic actions.

Replacement of the catechol 3,4-dihydroxylation pattern of certain adrenergic beta-phenethylamines by a resorcinol 3,5-dihydroxylation pattern has led to a greater selectivity of adrenergic agonist effects in certain molecules. This strategy has been applied to a series of dopaminergic agents derived from 2-aminotetralin, leading to a 5,7-dihydroxylation pattern. Traditional literature approaches to formation of a tetralin ring with this oxygenation pattern failed. A method was used which involved cyclization of 3,5-dimethoxybenzylsuccinic acid derivatives with pyridinium poly(HF) and subsequent modification of the tetralin ring. The resorcinol-derived 2-aminotetralins were less potent and less active dopaminergic agents than their catechol-derived isomers (5,6-dihydroxy and/or 6,7-dihydroxy). Certain of the subject compounds demonstrated alpha- and beta 1-adrenoceptor activating properties.

Animals↗
PubMed1997

Translational Isomerism in Some Two- and Three-Station [2]Rotaxanes.

The template-directed syntheses of three [2]rotaxanes are described. They all have dumbbell components, with both hydroquinone and resorcinol rings inserted into polyether chains terminated by tetraarylmethane stoppers, that become encircled during the key self-assembly processes by the tetracationic cyclophane, cyclobis(paraquat-p-phenylene), with its two pi-electron deficient bipyridinium units. It has been demonstrated by low-temperature (1)H NMR spectroscopy that the pi-electron deficient tetracationic cyclophane has a remarkably high preference to reside around the hydroquinone ring in these molecular shuttles. This observation illustrates how a very small constitutional difference-hydroquinone versus resorcinol recognition sites-can lead to the overwhelming preference for one translational isomer over another in this particular range of [2]rotaxanes.

Journal Article↗
PubMed1997

Shortcut Syntheses of Naturally Occurring 5-Alkylresorcinols with DNA-Cleaving Properties.

Resorcinols such as 1-5 bearing long alkyl- or alkenyl substituents at the C-5 position, including bola-formed bis-resorcinol derivatives, have recently been isolated from natural sources and were shown to exhibit exceptional DNA-cleaving properties under oxidative conditions. Previous synthetic approaches to such compounds seem inappropriately lengthy with regard to their structural simplicity. Disclosed is a very flexible synthesis which assembles these targets from triflate 7 and well accessible alkenes, dienes, enynes, or dienynes, respectively, by means of a boron-mediated reaction manifold. As a typical example, hexadeca-1,15-dien-8-yne 11 is hydroborated with 9-H-9-BBN at all possible sites, the alkenyl borane entity of the resulting tris-borane 12 is selectively cleaved off to afford the desired (Z)-alkene group in a stereoselective manner, the remaining two terminal alkylboranes are treated with NaOMe, and the bis-borate complex 13 thus formed is finally used as the nucleophile for a palladium-catalyzed Suzuki cross-coupling reaction with triflate 7. This sequence is carried out in one pot and provides product 14 in 62% overall yield. Demethylation of 14 (and analogues) can be conveniently achieved by means of 9-iodo-9-BBN to afford the natural product 5. The efficiency and flexibility of this unprecedented approach which combines different features of classical and modern boron chemistry is further demonstrated by the synthesis of anacardic and ginkgolic acid derivatives.

Journal Article↗
PubMedDate not supplied

Inhibition of thyroid peroxidase by dietary flavonoids.

Flavonoids are widely distributed in plant-derived foods and possess a variety of biological activities including antithyroid effects in experimental animals and humans. A structure-activity study of 13 commonly consumed flavonoids was conducted to evaluate inhibition of thyroid peroxidase (TPO), the enzyme that catalyzes thyroid hormone biosynthesis. Most flavonoids tested were potent inhibitors of TPO, with IC50 values ranging from 0.6 to 41 microM. Inhibition by the more potent compounds, fisetin, kaempferol, naringenin, and quercetin, which contain a resorcinol moiety, was consistent with mechanism-based inactivation of TPO as previously observed for resorcinol and derivatives. Other flavonoids inhibited TPO by different mechanisms, such as myricetin and naringin, showed noncompetitive inhibition of tyrosine iodination with respect to iodine ion and linear mixed-type inhibition with respect to hydrogen peroxide. In contrast, biochanin A was found to be an alternate substrate for iodination. The major product, 6,8-diiodo-biochanin A, was characterized by electrospray mass spectrometry and 1H-NMR. These inhibitory mechanisms for flavonoids are consistent with the antithyroid effects observed in experimental animals and, further, predict differences in hazards for antithyroid effects in humans consuming dietary flavonoids. In vivo, suicide substrate inhibition, which could be reversed only by de novo protein synthesis, would be long-lasting. However, the effects of reversible binding inhibitors and alternate substrates would be temporary due to attenuation by metabolism and excretion. The central role of hormonal regulation in growth and proliferation of thyroid tissue suggests that chronic consumption of flavonoids, especially suicide substrates, could play a role in the etiology of thyroid cancer.

Animals↗
PubMed2002

Adsorption and detection of some phenolic compounds by rice husk ash of Kenyan origin.

Rice husk ash (RHA) obtained from a rice mill in Kenya has been used as an inexpensive and effective adsorbent (and reagent) for the removal (and detection) of some phenolic compounds in water. The abundantly available rice mill waste was used in dual laboratory-scale batch experiments to evaluate its potential in: (i) the removal of phenol, 1,3-dihydroxybenzene (resorcinol) and 2-chlorophenol from water; and (ii) the detection of 1,2-dihydroxybenzene (pyrocatechol) and 1,2,3-trihydroxybenzene (pyrogallol) present in an aqueous medium. The studies were conducted using synthetic water with different initial concentrations of the phenolic compounds. The effects of different operating conditions (such as contact time, concentration of the phenolic compounds, adsorbent quantity, temperature, and pH) were assessed by evaluating the phenolic compound removal efficiency as well as the extent of their color formation reactions (where applicable). RHA exhibits reasonable adsorption capacity for the phenolic compounds and follows both Langmuir and Freundlich isotherm models. Adsorption capacities of 1.53 x 10(-4), 8.07 x 10(-5), and 1.63 x 10(-6) mol g(-1) were determined for phenol, resorcinol and 2-chlorophenol, respectively. Nearly 100% adsorption of the phenolic compounds was possible and this depended on the weight of RHA employed. For the detection experiments, pyrocatechol and pyrogallol present in water formed coloured complexes with RHA, with the rate of colour formation increasing with temperature, weight of RHA, concentration of the phenolic compounds and sonication. This study has proven that RHA is a useful agricultural waste product for the removal and detection of some phenolic compounds.

Adsorption↗
PubMed2006

Anion binding by catechols--an NMR, optical and electrochemical study.

The X-ray structure of the ClC chloride channel made it clear that O-H...chloride interactions play a key role in important biological membrane-bound systems, however, surprisingly this type of interaction has only been rarely exploited for the development of synthetic anion receptors. This paper therefore reports the anion binding strengths and selectivities of some simple commercially available bis-phenols. In particular, we compare catechol (1,2-dihydroxybenzene) and resorcinol (1,3-dihydroxybenzene) which show interesting and different selectivities between the halide anions in acetonitrile solution. Catechol binds tetrabutylammononium (TBA) chloride almost 30 times more strongly than TBA bromide, whilst for resorcinol, this difference drops to a factor of ca. 3.5. It is suggested that this is a consequence of the bite angle of the chelating hydrogen bonding groups of catechol being particularly appropriate for effective binding of the smaller anion. The oxidation of catechol to ortho-quinone is perturbed by the addition of chloride anions, as probed via cyclic voltammetry, and this compound can therefore be considered to act as an electrochemical sensor for chloride. Nitrocatechol is able to bind chloride anions more strongly than catechol as a consequence of its enhanced acidity and hence greater hydrogen bond donor character. Furthermore, nitrocatechol senses the bound anion via changes in its UV-visible spectrum. Notably, binding still occurs even in the presence of small amounts of competitive solvents (e.g. water). This observation has biomimetic importance as wet acetonitrile has some similarity in terms of overall polarity and hydrogen bond competition to the solvent shielded interiors of biological macromolecules and membranes--such as the environment within the ClC chloride channel itself. Finally, we report that catechol undergoes a unique colorimetric response on the addition of basic anions, such as fluoride. We can assign this response as being due to oxidative degradation of catechol catalysed by the basic anions (which bind to, and deprotonate, the catechol). This process is somewhat analogous to the well-known metal catalysed oxidation of catechol which can take place in aqueous solution. The speed of response and easily monitored and distinctive colour change induced by fluoride anions indicates this may be a useful mechanism for exploitation in the development of selective fluoride sensors.

Journal Article↗
PubMed1998

Coordination of Zn2+ (and Cd2+) by prokaryotic metallothionein. Involvement of his-imidazole.

In mammalian metallothionein Zn2+ is exclusively coordinated to Cys-thiolate to form clusters in which the metal is thermodynamically stable but also kinetically labile. By contrast, little is known about coordination to prokaryotic metallothionein, SmtA. 3 nmol of Zn2+ nmol-1 SmtA were displaced by 8 nmol of p-(hydroxymercuri)phenylsulfonate implicating eight of the nine Cys in the coordination of three metal ions. None of the Zn2+ associated with SmtA was accessible to 4-(2-pyridylazo)resorcinol prior to the addition of p-(hydroxymercuri)phenylsulfonate. An unusual feature of SmtA is the presence of three His residues, and we have investigated whether these contribute to metal coordination. Less Zn2+ was associated with purified SmtA(H40R/H49R/H55R), in which all three His residues were substituted with Arg, and approximately one equivalent of Zn2+ was immediately accessible to 4-(2-pyridylazo)resorcinol. Following incubation of SmtA with 111Cd, three 111Cd resonances were detected, two in a range expected for CdS4 and the third indicative of either CdNS3 or CdN2S2 coordination. Two-dimensional TOCSY 1H NMR and 111Cd-edited 1H NMR showed two His residues bound to 111Cd, confirming CdN2S2 coordination. The pH of half-dissociation of Zn2+ increased from 4.05 for SmtA to 5.37 for SmtA(H40R/H49R/H55R). Equivalent values for single His mutants SmtA(H40R), SmtA(H49R), and SmtA(H55R) were 4.62, 4.48, and 3.81, respectively, revealing that conversion of His40 or His49 to Arg impairs Zn2+ binding at the CdN2S2 and CdS4 sites. Only approximately two equivalents of Zn2+ were associated with purified SmtA(H49R). The appearance of a fourth 111Cd resonance at lower pH suggests that an alternative CdN2S2 site also exists.

Amino Acid Sequence↗
PubMed2006

Functional characterization of desaturases involved in the formation of the terminal double bond of an unusual 16:3Delta(9,12,150) fatty acid isolated from Sorghum bicolor root hairs.

Sorgoleone, produced in root hair cells of sorghum (Sorghum bicolor), is likely responsible for much of the allelopathic properties of sorghum root exudates against broadleaf and grass weeds. Previous studies suggest that the biosynthetic pathway of this compound initiates with the synthesis of an unusual 16:3 fatty acid possessing a terminal double bond. The corresponding fatty acyl-CoA serves as a starter unit for polyketide synthases, resulting in the formation of 5-pentadecatrienyl resorcinol. This resorcinolic intermediate is then methylated by an S-adenosylmethionine-dependent O-methyltransferase and subsequently dihydroxylated, yielding the reduced (hydroquinone) form of sorgoleone. To characterize the corresponding enzymes responsible for the biosynthesis of the 16:3 fatty acyl-CoA precursor, we identified and cloned three putative fatty acid desaturases, designated SbDES1, SbDES2, and SbDES3, from an expressed sequence tag (EST) data base prepared from isolated root hairs. Quantitative real-time RT-PCR analyses revealed that these three genes were preferentially expressed in sorghum root hairs where the 16:2 and 16:3 fatty acids were exclusively localized. Heterologous expression of the cDNAs in Saccharomyces cerevisiae revealed that recombinant SbDES2 converted palmitoleic acid (16:1Delta(9)) to hexadecadienoic acid (16:2Delta(9,12)), and that recombinant SbDES3 was capable of converting hexadecadienoic acid into hexadecatrienoic acid (16:3Delta(9,12,15)). Unlike other desaturases reported to date, the double bond introduced by SbDES3 occurred between carbons 15 and 16 resulting in a terminal double bond aliphatic chain. Collectively, the present results strongly suggest that these fatty acid desaturases represent key enzymes involved in the biosynthesis of the allelochemical sorgoleone.

Amino Acid Sequence↗
PubMed2004

Some biochemical properties of polyphenol oxidase from celery.

Polyphenol oxidase (PPO, EC 1.14.18.1) was extracted from celery roots (Apium graveolens L.) with 0.1 M phosphate buffer, pH 7.0. The PPO was partially purified by (NH4)2SO4 and dialysis. Substrate specificity experiments were carried out with catechol, pyrogallol, L-DOPA, p-cresol, resorcinol, and tyrosine. The Km for pyrogallol, catechol, and L-DOPA were 4.5, 8.3, and 6.2mM, respectively, at 25 degrees C. Data for Vmax/Km values, which represent catalytic efficiency, show that pyrogallol has the highest value. The optimum pH and temperature were determined with catechol, pyrogallol, and L-DOPA. Optimum pH was 7.0 for catechol and L-DOPA, and 7.5 for pyrogallol. Optimum temperatures for maximum PPO activity were 25 degrees C for pyrogallol, 40 degrees C for catechol, and 45 degrees C for L-DOPA. Heat inactivation studies showed a decrease in enzymatic activity at temperatures above 60 degrees C. The order of inhibitor effectiveness was: L-cysteine > ascorbic acid > glycine > resorcinol > NaCl.

Apium↗
PubMed1997

Isolation and structural characterization of glycosphingolipids of in vitro propagated bovine aortic endothelial cells.

Neutral glycosphingolipids and gangliosides were isolated from 3.7 x 10(9) primary bovine aortic endothelial cells and structurally characterized by immunological and chemical methods. Glucosyl- and lactosylceramide were detected as the main neutral glycosphingolipids (28% and 40% of total orcinol stain, respectively); LcOse3Cer and nLcOse4Cer were expressed to somewhat minor amounts (16% and 10% of total orcinol stain, respectively), and nLcOse6Cer occurred only in trace quantities. No neutral glycosphingolipids of the ganglio-series (GgOse3Cer and GgOse4Cer) and the globo-series (GbOse4Cer and the Forssman antigen) have been detected; only traces of GbOse3Cer were identified by TLC immunostaining. Positive CD15 bands obtained by TLC overlay with anti-Gal beta1-4(Fuc alpha1-3)GlcNAc beta1-R antibody indicated the presence of lipid bound Lewisx antigen, whereas the isomeric Lewis(a) structure (Gal beta1-3(Fuc alpha1-4)GlcNAc beta1-R) was not detectable. G(M3) substituted with Neu5Gc and Neu5Ac in a 2:1 ratio was the major ganglioside comprising about 95% within the whole ganglioside fraction. G(M3)-structures were further characterized by FAB-MS and GC-MS of the native compounds and their permethylated derivatives. C18-sphingosine was the only long chain base, whereas variation occurred due to C(24:0,24:1) and C16 fatty acids. Terminally alpha2-3 sialylated neolacto-series gangliosides with nLcOse4- and nLcOse6Cer (<5% of total resorcinol stain) were found in almost equal quantities, whereas no alpha2-6 sialylated counterparts were detected. Fucosylated gangliosides with poly-N-acetyllactosaminyl chains (sialyl Lewis[x], sialyl Lewisa, and VIM-2 antigen) and sulfoglucuronylneolacto series structures with HNK-1 epitope were not detectable in the acidic glycosphingolipid fraction by TLC immunostaining. Gangliotetraose-type gangliosides G(M1) and G(D1a) (<1 % of total resorcinol stain) as well as traces of G(D1b) and G(T1b) have been distinctly identified by combined choleragenoid-TLC-immunostaining and previous neuraminidase treatment. The expression of dominant glycosphingolipids lactosylceramide and G(M3)(Neu5Gc) was proved by indirect immunofluorescence microscopy of cell layers grown in chamber slides, each showing different plasma membrane and subcellular distribution patterns. The results provide the basis for investigation of the role of glycosphingolipids as cell surface antigens of cellular interaction as well as receptors for blood components and macromolecules of the extracellular matrix.

Animals↗
PubMed1999

Isolation and structural characterization of glycosphingolipids of in vitro propagated human umbilical vein endothelial cells.

To investigate in detail the expression of glycosphingolipids (GSLs) on endothelial cells, 4.85 x 10(9) human umbilical vein endothelial cells (HUVECs) were cultivated in a 2 l bioreactor using microcarriers as a support for anchorage dependent growing cells. Neutral GSLs and gangliosides were isolated and their structures were determined by TLC immunostaining, fast atom bombardment-mass spectrometry (FAB-MS) of the native GSLs, and gas chromatography-electron impact mass spectrometry (GC-EIMS) of partially methylated alditol acetates. GbOse4Cer, GbOse3Cer, and LacCer, all carrying mainly C24- and C16-fatty acid beside C18-sphingosine, were detected as the major neutral GSLs (36%, 23%, and 15% of the total orcinol stain, respectively); GlcCer, nLcOse4Cer, and nLcOse6Cer were expressed to substantial minor amounts (9%, 12%, and 5% of the total orcinol stain, respectively). TLC immunostaining revealed the presence of lipid bound Lewisx antigen, whereas the isomeric Lewisa structure was detectable only in very low quantities. GM3(Neu5Ac) with C18-sphingosine was the major ganglioside constituting about 90% of the whole ganglioside fraction. The fatty acid composition was determined by GC-MS of fatty acid methyl esters, indicating the predominance of C24- and C16-substituted GM3(Neu5Ac), followed by C18- and C22-substituted species. Terminally alpha2-3 sialylated neolacto-series ganglioside IV3Neu5Ac-nLcOse4Cer was the second most abundant ganglioside in HUVECs (8% of the total resorcinol stain), and IV6Neu5Ac-nLcOse4Cer and VI3Neu5Ac-nLcOse6Cer (together less than 2% of total resorcinol stain) were found in minor quantities. Lipid bound sialyl Lewisx antigen with poly-N-acetyllactosaminyl chains, and traces of gangliotetraose-type gangliosides GM1 and GD1a were identified by TLC immunostaining. The expression of dominant neutral GSLs LacCer, GbOse3Cer, and GbOse4Cer, and of ganglioside GM3(Neu5Ac) was assayed by indirect immunofluorescence microscopy of cell layers grown in chamber slides, each showing different plasma membrane and subcellular distribution patterns. The complete structural characterization of GSLs from HUVECs contributes to our understanding about their functional role, not only of the carbohydrate but also of the lipid moiety, as receptors for bacterial toxins, as cell surface antigens of cellular interaction and as receptors for blood components and macromolecules of the extracellular matrix.

Bioreactors↗
PubMed1990

Hypothyroidism in textile workers.

Four cases of overt hypothyroidism, three of whom were men in their early forties, had occurred over a period of 6 years at a textile factory where thiourea and resorcinol were used in the finishing departments. A follow-up survey of 189 men and 48 women (44 per cent of employees) revealed 12 new cases of varying grades of hypothyroidism, categorized after the system proposed by Evered. These included a case of mild hypothyroidism in a male worker, who subsequently received thyroid hormone replacement therapy as a hospital out-patient. A full occupational hygiene survey was carried out to determine possible sources of exposure to thiourea and resorcinol. Although we were unable to demonstrate a statistically significant occurrence of biochemically and immunologically detectable disturbances in thyroid function among this workforce, we did note that three of the original index cases and several of those workers with varying degrees of minor dysfunction in the follow-up study seemed to cluster in locations where exhausted fumes could accumulate.

Adult↗
PubMed1995

Purification and reaction mechanism of arylsulfate sulfotransferase from Haemophilus K-12, a mouse intestinal bacterium.

A novel type of sulfotransferase, arylsulfate sulfotransferase [EC 2.8.2.22], was purified to homogeneity from Haemophilus K-12, a mouse intestinal bacterium. The purified enzyme (M(r) 290,000) is composed of four subunits (M(r) 70,000). The best donor substrate was 4-methylumbelliferyl sulfate, followed by beta-naphthyl sulfate, p-nitrophenyl sulfate (PNS), and alpha-naphthyl sulfate. The best acceptor substrate was alpha-naphthol, followed by phenol and resorcinol. The apparent Km for PNS using phenol as an acceptor and that for phenol and resorcinol. The apparent Km for PNS using phenol as an acceptor and that for phenol using PNS as a donor substrate were determined to be 0.095 and 0.71 mM, respectively. One of the reaction products, p-nitrophenol inhibited the enzyme noncompetitively with respect to PNS, but competitively with respect to alpha-naphthol. The Ki values of PNP for PNS and alpha-naphthol were 0.89 and 0.12 mM, respectively. The other reaction product, alpha-naphthyl sulfate, inhibited the enzyme competitively with respect to PNS, but non-competitively with respect to alpha-naphthol. The Ki values of alpha-naphthyl sulfate for PNS and for alpha-naphthol were 2.72 and 1.7 mM. These results suggest that the sulfate transfer reaction proceeds according to a ping pong bi bi mechanism.

Animals↗