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PubMed2002

Crystal structure of bacterial morphinone reductase and properties of the C191A mutant enzyme.

The crystal structure of the NADH-dependent bacterial flavoenzyme morphinone reductase (MR) has been determined at 2.2-A resolution in complex with the oxidizing substrate codeinone. The structure reveals a dimeric enzyme comprising two 8-fold beta/alpha barrel domains, each bound to FMN, and a subunit folding topology and mode of flavin-binding similar to that found in Old Yellow Enzyme (OYE) and pentaerythritol tetranitrate (PETN) reductase. The subunit interface of MR is formed by interactions from an N-terminal beta strand and helices 2 and 8 of the barrel domain and is different to that seen in OYE. The active site structures of MR, OYE, and PETN reductase are highly conserved reflecting the ability of these enzymes to catalyze "generic" reactions such as the reduction of 2-cyclohexenone. A region of polypeptide presumed to define the reducing coenzyme specificity is identified by comparison of the MR structure (NADH-dependent) with that of PETN reductase (NADPH-dependent). The active site acid identified in OYE (Tyr-196) and conserved in PETN reductase (Tyr-186) is replaced by Cys-191 in MR. Mutagenesis studies have established that Cys-191 does not act as a crucial acid in the mechanism of reduction of the olefinic bond found in 2-cyclohexenone and codeinone.

Bacterial Proteins↗

PubMed2005

Topical application of representative multifunctional acrylates produced proliferative and inflammatory lesions in F344/N rats and B6C3F1 mice, and squamous cell neoplasms in Tg.AC mice.

Widespread human exposure to multifunctional acrylates is of concern, due to their inherent reactivity and irritating properties. Trimethylolpropane triacrylate (TMPTA) and pentaerythritol triacrylate (PETA) are industrially important representatives of multifunctional acrylates. The current studies characterized the toxicity of 3-month topical administration of technical grade TMPTA and PETA in F344/N rats and B6C3F1 mice, and evaluated the carcinogenic potential of TMPTA and PETA in hemizygous Tg.AC (v-Ha-ras) transgenic mice. Administration of 0.75, 1.5, 3, 6, and 12 mg/kg TMPTA and PETA for 3 months resulted in hyperplastic, degenerative, and necrotic lesions, accompanied by chronic inflammation of the skin, with severities generally increasing with dose. Lesions were slightly more severe in rats, when compared with mice, and illustrate the irritant potential of TMPTA and PETA. A similar dosage regimen was used for the 6-month study with Tg.AC mice. Topical application of TMPTA and PETA to Tg.AC mice showed dose-dependent increases in squamous cell papillomas at the site of application, with decreases in the latency of their appearance in mice receiving 3 mg/kg or greater. Papillomas, the reporter phenotype in Tg.AC mice, were accompanied by a few squamous cell carcinomas, along with hyperplastic and inflammatory lesions. Although chronic inflammation might have contributed to the development of the skin lesions, the dose-related nature of the induction of the skin papillomas in Tg.AC mice by TMPTA and PETA may reflect a potential for carcinogenicity.

Acrylates↗

PubMedDate not supplied

Compositional analysis of commercial PVC bottles and studies of aspects of specific and overall migration into foods and stimulants.

Plastics additives and processing aids present severe difficulties for the legislator attempting to establish meaningful controls. In many cases information both on the substances added to the plastic and on the species migrating into food, which may well be different, are lacking. In the studies reported, information has been sought on the actual components employed in two typical commercial plastics. Analysis has been carried out of both the composition and trace constituents of the ingredients of commercial PVC formulations used for manufacturing bottles for orange squash and cooking oil applications. Assessment of maximum leachable material was made by solvent extraction of the individual additives, which was compared with overall migration from the PVC bottles into food stimulants using proposed EEC Statutory Methods. Additionally, specific migration measurements of epoxidized soyabean oil, tris(nonylphenyl) phosphite, nonylphenol, pentaerythritol, and BHT antioxidant were carried out in food stimulants and where possible also in foods.

Chemical Phenomena↗

PubMed1985

Dermal oncogenicity bioassays of monofunctional and multifunctional acrylates and acrylate-based oligomers.

Several important components of photocurable coatings were studied for dermal tumorigenic activity by repeated application to the skin of mice. The substances tested were 2-ethylhexyl acrylate (EHA) and methylcarbamoyloxyethyl acrylate (MCEA) (monomers); neopentyl glycol diacrylate (NPGDA), esterdiol-204-diacrylate (EDDA), and pentaerythritol tri(tetra)acrylate (PETA) (cross-linkers); and three acrylated urethane oligomers. For each bioassay, 40 C3H/HeJ male mice were dosed 3 times weekly on the dorsal skin for their lifetime with the highest dose of the test agent that caused no local irritation or reduction in body weight gain. Two negative control groups received acetone (diluent) only. A positive control group received 0.2% methylcholanthrene (MC). NPGDA and EHA had significant tumorigenic activity with tumor yields of eight and six tumor-bearing mice (three and two malignancies), respectively. The MC group had 34 mice with carcinomas and 1 additional mouse with a papilloma. MCEA had no dermal tumorigenic activity but resulted in early mortality. No skin tumors in the treatment area were observed in the other groups. Additional studies will be necessary to elucidate possible relationships between structure and tumorigenic activity for the acrylates.

Acrylates↗

PubMed1989

Analysis of the genotoxicity of nine acrylate/methacrylate compounds in L5178Y mouse lymphoma cells.

Nine acrylate/methacrylate esters were tested for the induction of mutations, aberrations and micronuclei in cultured L5178Y mouse lymphoma cells without exogenous activation. With the exception of 2-ethylhexyl acrylate, and dicyclopentenyloxyethyl methacrylate which produced equivocal mutagenic responses, the other seven compounds (2-hydroxyethyl acrylate, dicyclopentenyloxyethyl acrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, and pentaerythritol triacrylate) produced positive mutagenic responses with different potencies. For the mutagenic acrylates/methacrylates, primarily small-colony, trifluorothymidine (TFT)-resistant mutants were induced, suggesting a clastogenic mechanism that was supported by increased aberrations and micronucleus frequencies (except for trimethylolpropane trimethacrylate which was positive for aberration but not micronucleus induction). Generally, it was found that multifunctional compounds (esters with greater than 1 functional vinyl group) required lower concentrations than monofunctional compounds to induce maximal cytotoxic, mutagenic, and clastogenic responses. In addition, acrylates were generally more potent than their corresponding methacrylates. This information and these comparative activities will provide some guidance for setting priorities of concern for hazard consideration for acrylate/methacrylate ester compounds.

Acrylates↗

PubMed2001

Alternate-strand triple-helix formation by the 3'-3'-linked oligodeoxynucleotides with the intercalators at the junction point.

3'-3'-Linked oligodeoxynucleotides (ODNs) with the anthraquinonyl group at the junction point were synthesized on a DNA synthesizer using a controlled pore glass (CPG), which has pentaerythritol carrying the intercalator at one of the four hydroxymethyl groups. Stability of the triplexes with the target duplexes was studied by thermal denaturation. The 3'-3'-linked ODNs with the anthraquinonyl group enhanced the thermal stability of the triplexes when compared with those without the intercalator and the unmodified nonamer. The inhibitory activity of the 3'-3'-linked ODNs against the cleavage of the target DNA by the restriction enzyme Hind III was tested. It was found that the 3'-3'-linked ODN with the anthraquinonyl group at the junction point inhibited the cleavage by the enzyme more effectively than the nonamer and the 3'-3'-linked ODN without the intercalator.

Anthraquinones↗

PubMed2001

Potentiation of sildenafil-induced hypotension is minimal with nitrates generating a radical intermediate.

Recently the new specific phosphodiesterase-5 inhibitor sildenafil was introduced into therapy for erectile dysfunction. Because of the phosphodiesterase-5 inhibitor-induced increases of cyclic GMP in the vasculature, vasodilation in various vascular beds is induced, which in combination with various nitrovasodilators (e.g., when used simultaneously for the treatment of coronary artery disease), may lead to excessive hypotension. Thus nitrovasodilators are contraindicated when sildenafil may be used and reports of a number of accidents have recently been published. We therefore studied the acute interactions of glyceryl trinitrate (GTN), pentaerythritol tetranitrate (PETN), and isosorbide dinitrate (ISDN) with sildenafil in six chronically instrumented conscious dogs for each nitrate to assess the magnitude of blood pressure drops (and compensatory increases in heart rate) during a 24-h nitrate administration (infusion into the pulmonary artery). Sildenafil (3 mg/kg) was given orally (after a 24-h fast) 30 min after start of nitrate infusion. GTN, PETN, or ISDN (which follow different steps of metabolic conversion to nitric oxide) were applied at submaximal dosages leading to 90% of maximal coronary artery dilation at 1.5 microg/kg per min, 0.75 microg/kg per min, or 6 microg/kg per min, respectively. During GTN infusion sildenafil caused a maximum drop in mean blood pressure of 21 +/- 3 mm Hg (rise in heart rate from 117.0 +/- 7.2 to 126.0 +/- 6 .0/min) and during ISDN infusion of 18 +/- 3 mm Hg (rise in heart rate from 115.0 +/- 7.0 to 125 +/- 6/min), which was significantly less (p < 0.01) during PETN (only 6 +/- 1 mm Hg with a rise in heart rate from 107.0 +/- 5.0 to 122.0 +/- 7.0/min). When sildenafil is used during exposure to nitrates (e.g., in coronary artery disease), the PETN-induced drop in blood pressure at equi-effective dosages (with regard to coronary dilation) is substantially smaller compared with that of GTN or ISDN, which is probably because of lesser potentiation of phosphodiesterase-5 inhibitor-induced effects in the arteriolar bed, thus minimizing critical drops in blood pressure.

Animals↗

PubMed1977

Allergic contact dermatitis from ultraviolet cured inks. Allergic contact sensitization to acrylates.

Eight men employed in the manufacture of ultraviolet cured inks developed allergic contact dermatitis predominantly on the exposed areas. Patch testing revealed sensitization to trimethylol propane triacrylate in seven employees, to 1,6-hexanediol diacrylate in six employees, to pentaerythritol triacrylatylate in four employees and to epoxy acrylate oligomers in three employees. Either cross-sensitization or concomitant sensitization may have accounted for the multiple reactions in several employees. One sensitized employee was patch tested with four different commercially available epoxy acrylate oligomers and reacted only to two, suggesting that variations possibly in chain length between these oligomers are important variables in the allergic reactions. The polyfunctional acrylic monomers and certain epoxy acrylate oligomers should be handled carefully to avoid the development of allergic contact dermatitis.

Acrylates↗

PubMed2006

Hydrogen tunnelling in enzyme-catalysed H-transfer reactions: flavoprotein and quinoprotein systems.

It is now widely accepted that enzyme-catalysed C-H bond breakage occurs by quantum mechanical tunnelling. This paradigm shift in the conceptual framework for these reactions away from semi-classical transition state theory (TST, i.e. including zero-point energy, but with no tunnelling correction) has been driven over the recent years by experimental studies of the temperature dependence of kinetic isotope effects (KIEs) for these reactions in a range of enzymes, including the tryptophan tryptophylquinone-dependent enzymes such as methylamine dehydrogenase and aromatic amine dehydrogenase, and the flavoenzymes such as morphinone reductase and pentaerythritol tetranitrate reductase, which produced observations that are also inconsistent with the simple Bell-correction model of tunnelling. However, these data-especially, the strong temperature dependence of reaction rates and the variable temperature dependence of KIEs-are consistent with other tunnelling models (termed full tunnelling models), in which protein and/or substrate fluctuations generate a configuration compatible with tunnelling. These models accommodate substrate/protein (environment) fluctuations required to attain a configuration with degenerate nuclear quantum states and, when necessary, motion required to increase the probability of tunnelling in these states. Furthermore, tunnelling mechanisms in enzymes are supported by atomistic computational studies performed within the framework of modern TST, which incorporates quantum nuclear effects.

Computer Simulation↗

PubMed1977

Effect of a myo-Inositol Antagonist, 2-O, C-Methylene-myo-Inositol, on the Metabolism of myo-Inositol-2-H and d-Glucose-1-C in Lilium longiflorum Pollen.

2-O,C-Methylene-myo-inositol (MMO), a myo-inositol (MI) antagonist, inhibits germination and tube elongation of pollen from Lilium longiflorum cv. Ace or 44. The presence of 5 mm MMO in Dickinson's pentaerythritol medium (Plant Physiol. 43:1-8) partially blocks germination. The tubes produced are short and fail to elongate. In the presence of MI, MMO's toxic effect is blocked. As little as 0.56 mm MI will maintain normal germination in the presence of 43 mm MMO, and pollen tubes continue to elongate for 2 to 3 hr. Eventually, the toxic action of MMO prevents further growth. MMO does not inhibit UDP-d-glucose dehydrogenase from lily pollen.Uptake of MI-2-(3)H and incorporation of tritium into galacturonic acid and pentose units of tube wall pectin are blocked by MMO. The site of this inhibition is undertermined. Uptake of d-glucose-1-(14)C and incorporation of (14)C into 70% ethyl alcohol-insoluble polysaccharides of germinated pollen are not blocked by MMO, but distribution of label into polysaccharide product is altered. In MMO-treated pollen, very little (14)C is found in uronic acid or pentose units. At 30 mm MMO, about two-thirds of the carbon flow from d-glucose to these pectic components is interrupted. MMO also alters d-glucose metabolism in the 70% ethyl alcohol-soluble fraction, but the compound involved must still be identified.These results offer fresh evidence of an intermediary role for MI during UDP-d-glucuronate biosynthesis in germinated pollen.

Journal Article↗

PubMed2005

Crystallization and preliminary structure determination of Escherichia coli Mfd, the transcription-repair coupling factor.

Transcription-repair coupling factors (TRCFs) are SF2 ATPases that couple transcription to DNA-damage repair by recognizing and removing RNA polymerase-elongation complexes stalled at DNA lesions and recruiting the nucleotide excision-repair machinery to the damaged sites. As a first step towards understanding the TRCF mechanism, the 130 kDa Escherichia coli TRCF (the product of the mfd gene) has been overexpressed, purified and crystallized using an unusual precipitant, pentaerythritol ethoxylate. Initial phases were obtained using single-wavelength anomalous dispersion with a highly redundant 4 A resolution data set collected from selenomethionyl-substituted crystals and dramatically improved by density modification and phase extension to 3.2 A resolution. Model building and refinement, which are in progress, will provide insight into transcription-coupled DNA-repair pathways, as this represents the first TRCF to be crystallized to date.

Bacterial Proteins↗

PubMed2006

Crystallization and preliminary characterization of three different crystal forms of human saposin C heterologously expressed in Pichia pastoris.

The amphiphilic saposin proteins (A, B, C and D) act at the lipid-water interface in lysosomes, mediating the hydrolysis of membrane building blocks by water-soluble exohydrolases. Human saposin C activates glucocerebrosidase and beta-galactosylceramidase. The protein has been expressed in Pichia pastoris, purified and crystallized in three different crystal forms, diffracting to a maximum resolution of 2.5 A. Hexagonal crystals grew from 2-propanol-containing solution and contain a single molecule in the asymmetric unit according to the Matthews coefficient. Orthorhombic and tetragonal crystals were both obtained with pentaerythritol ethoxylate and are predicted to contain two molecules in the asymmetric unit. Attempts to determine the respective crystal structures by molecular replacement using either the known NMR structure of human saposin C or a related crystal structure as search models have so far failed. The failure of the molecular-replacement method is attributed to conformational changes of the protein, which are known to be required for its biological activity. Crystal structures of human saposin C therefore might be the key to mapping out the conformational trajectory of saposin-like proteins.

Crystallization↗

PubMed2005

An epidemic of occupational contact dermatitis from an acrylic glue.

Dermatological examinations were performed in 81 workers involved in the manufacture of electric coils for television displays, who had worked for 4 years in contact with a glue containing isobornyl acrylate, acrylic acid, N,N dimethyleneacrylamide, phosphine oxide, bis(2,6-dimethoxybenzoyl) (2,4,4-trimethylpentyl)- and beta-carboxyethyl acrylate. The glue was cured by 350-500-nm ultraviolet and visible radiations. Acrylate-specific dermal lesions were detected in 21 (25.9%) people. Occupational irritant contact dermatitis was diagnosed in 12 (15%) of the workers and occupational allergic contact dermatitis in 9 (11.2%). 12 people reacted to acrylates. Cross-reactions with methacrylates were not observed. The highest number of positive tests was obtained with triethyleneglycol diacrylate (10 people) and diethyleneglycol diacrylate (9), followed by 1,6-hexanediol diacrylate (5), 1,4-butanediol diacrylate (4), beta-carboxyethyl acrylate (3), tripropyleneglycol diacrylate (2) and pentaerythritol triacrylate (2). No cases of allergy to isobornyl acrylate, N,N-methylenebisacrylamide or phosphine oxide were noted.

Acrylates↗

PubMed1996

Occupational conjunctivitis associated with type IV allergy to methacrylates.

On rare occasions, exposure to methacrylates (MAs) may induce mucosal symptoms. Three patients, two dental laboratory workers and one hearing aid laboratory worker, are presented. All three had allergic contact dermatitis from MAs which disappeared after avoidance of contact with uncured MA compounds. Two of the patients, the dental laboratory assistant and the hearing aid worker, had also developed symptoms of conjunctivitis. Both were exposed to chemically curable and light-curable MAs. The association between their conjunctivitis and type IV allergy to MAs was supported by the following observations: 1) sensitization to several MAs including methylMA, 2-hydroxyethylMA, ethyleneglycol diMA, triethyleneglycoldiMA, tetrahydrofurfuryldiMA, and 1,4-butanedioldiMA, as well as to pentaerythritol triacrylate; 2) simultaneous appearance of their eye symptoms and allergic contact dermatitis; 3) high exposure to MAs because of disturbances of ventilation; 4) disappearance of the eye symptoms during holidays; and 5) opthalmologist's findings of follicular conjunctivitis with some papillae, eosinophilia, and lymphocytosis in conjunctival scrapings corresponding to allergic contact conjunctivitis. In addition, the activation of eosinophils in the conjunctival scrapings was demonstrated with the monoclonal antibody technique, and an elevated level of eosinophilic cationic protein was found in the tear fluid. Our cases suggest that conjunctivitis may be caused by type IV allergy to MAs, although type I allergy (even though prick tests were negative), other hypersensitivity mechanisms, or irritation cannot be excluded. 4H-Gloves seem to give adequate hand protection even to allergic patients. More attention should be paid to ventilation systems if MA exposure occurs. In some cases, patients with eye symptoms need to be patch tested.

Conjunctivitis, Allergic↗

PubMed1991

Effects of alkyl alcohols and related chemicals on rat liver structure and function. I. Induction of two distinct types of megamitochondria.

The effects of alkyl alcohols and related chemicals on the ultrastructure of mitochondria in the rat hepatocyte were studied. The following three different groups of chemicals were tested: Group 1: alkyl alcohols with straight carbon chains (ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-octanol, 1-dodecanol and 1-octadecanol); Group 2: tert- and cyclo-compounds (tert-butanol, cyclo-pentanol, and cyclo-hexanol); and Group 3: polyhydroxy alcohols (ethylene glycol, propylene glycol, 1, 3-propanediol, glycerol and pentaerythritol). Results obtained were summarized as follows: 1) Ethanol, 1-propanol, 1-butanol, 1-pentanol and 1-octanol had essentially the same effects on the mitochondrial ultrastructure: a mixed population of small and enlarged mitochondria with poorly developed cristae; 1-dodecanol induced ultrastructural changes of mitochondria of two distinct types: a mixed population of small and enlarged mitochondria with poorly developed cristae in some hepatocytes and remarkably enlarged mitochondria with well-developed cristate in others; and 1-octadecanol induced remarkably enlarged mitochondria in all hepatocytes. 2) Chemicals belonging to group 2 and group 3 induced essentially the same changes as those induced by 1-octadecanol. More than one month was required to induce those changes. The mechanism by which those ultrastructural mitochondrial changes were induced is not clear, but the present results may suggest that the hydroxy group (-OH) common to all these chemicals in some way accounts for the phenomenon.

1-Butanol↗

PubMed1977

Comparative effects of glyceryl trinitrate on venous and arterial smooth muscle in vitro; relevance to antianginal activity.

1. A quantitative in vitro study has been made of the actions of glyceryl trinitrate and sodium nitrite on vascular smooth muscle (dog femoral artery and saphenous vein; rat portal vein); these have been compared with the actions of papaverine, isoprenaline, salbutamol, pentaerythritol tetranitrate and trimetazidine. 2. Glyceryl trinitrate was more active on the saphenous vein than on the femoral artery in inhibiting noradrenaline and potassium-induced tone. 3. Unlike glyceryl trinitrate, sodium nitrite and isoprenaline, papaverine and diazoxide inhibited noradrenaline-induced contractions of venous and arterial smooth muscle to the same extent. 4. The selective dilator effects of glyceryl trinitrate on venous smooth muscle may explain its action in alleviating the pain of angina pectoris. It is suggested that the use of these three vascular smooth muscle preparations (arterial, and veins with and without spontaneous myogenic activity) is a useful initial screening procedure for prospective antianginal drugs acting by venodilatation.

Angina Pectoris↗

PubMed1977

Contact dermatitis from polyfunctional acrylic monomers.

Five out of 26 men employed formulating radiation drying printing ink developed eczematous dermatitis. Positive patch tests were obtained with two polyfunctional acrylic monomers, pentaerythritol triacrylate and trimethylol propane triacrylate and with formulations containing these in four affected employees. Cross sensitization was observed to dipentaerythritol monohydroxy pentaacrylate in each case. A fifth employee appeared to have developed irritant dermatitis from contact with these materials.

Acrylates↗

PubMed1977

Allergic dermatitis due to a triacrylate in ultraviolet cured inks.

Investigation of a dermatitis incident involving the handling of UV type inks by press minders is described. Patch tests pinpointed one acrylic component of the UV ink (pentaerythritol triacrylate) as the causal sensitizer. Factors influencing the identification and incidence of sensitization to the same chemical in different work situations are discussed as are lessons in terms of prevention under the Health and Safety at Work Act 1974.

Acrylates↗