Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CATECHOL”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources
PubMed2006

Structure-DPPH* scavenging activity relationships: parallel study of catechol and guaiacol acid derivatives.

The scavenging behavior of a series of catechol and guaiacol acid derivatives toward DPPH(*) was examined having as a starting point the order of activity derived on the basis of theoretically calculated BDE values. The studied compounds were protocatechuic, homoprotocatechuic, dihydrocaffeic, and caffeic acids and also vanillic, homovanillic, dihydroferulic, and ferulic acids. Catechol and guaiacol were used as reference compounds. Observations from the parallel study were made with regard to structural features (number and position of hydroxyl groups and the side-carbon chain characteristics) that regulated the behavior of the compounds experimentally. The exceptional DPPH(*) scavenging behavior observed for homoprotocatechuic acid in ethanol and for caffeic acid in acetonitrile could not be supported by the respective BDE values. Ferulic was the most active among guaiacolic acids, whereas dihydroferulic exhibited the highest stoichiometry. Ionizable carboxylic groups seem to affect considerably the relative order of activity as was also evidenced using the ORAC assay. Questions raised about the validity of widely accepted views on criteria for SARs are discussed with regard to literature findings.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

Bis-catechol-substituted redox-reactive analogues of hexamethonium and decamethonium: stimulated affinity-dependent reactivity through iron peroxide catalysis.

Symmetrically bis-catechol-substituted analogues (1 and 2, respectively) of hexamethonium and decamethonium were synthesized and investigated as redox-activated affinity reagents toward the neurotoxin-binding sites of the nicotinic acetylcholine receptor (nAcChR), purified from Torpedo californica electroplax. These reagents bound to nAcChR with Kd = 1.8 x 10(-8) and 2.3 x 10(-7) M for 1 and 2, respectively. In the presence of a metal, Fe(II)/Fe(III), and peroxide, both reagents produced a rapid and efficient half-of-sites inactivation of neurotoxin-binding sites in the nAcChR in a concentration-dependent manner, which paralleled the extent of receptor binding of the reagents. In the absence of Fe(II)/Fe(III) peroxide, redox-dependent inactivation occurred for both 1 and 2 more slowly and only at concentrations much higher (10(3)-10(4) times) than those necessary to produce significant binding to nAcChR. However, receptor inactivation in the absence of added metal peroxide was still more efficient for 1 and 2 than observed previously for [(trimethylammonio)methyl]catechol (3), the prototypic redox-dependent affinity reagent after which 1 and 2 were patterned. Thus, the new reagents reported are expected to provide more efficient and selective conditions for redox-dependent inactivation at nAcChR and other macromolecular sites to which such reagents may be directed.

Animals↗
PubMed1993

Specific sequestering agents for the actinides. 21. Synthesis and initial biological testing of octadentate mixed catecholate-hydroxypyridinonate ligands.

The linear octadentate ligand 3,4,3-LIHOPO, which contains four 1-hydroxy-2(1H)-pyridinone (1,2-HOPO) groups, is the most effective agent for in vivo chelation of Pu(IV) yet prepared. However, its clinical potential is limited by acute toxicity of the free ligand (but not Fe3+ complex) at high dosage. The high acidity of HOPO ligands and the much lower acidity of catechol (CAM) ligands suggested that mixed octadentate (CAM-HOPO) ligands containing one or two 1,2-HOPO and three (or two) catechol (CAM) groups might be as effective for Pu removal [fully eight-coordinated Pu(IV) complexes formed at pH > or = 6] and less toxic than 3,4,3-LIHOPO. Treatment of spermine with 3-(2,3-dimethoxybenzoyl)thiazol-idine-2-thione (1) (molar ratio 2:1) gave 1,14-bis(2,3-dimethoxybenzoyl)-1,5,10,14-tetraazatetradecane (2, DiCAM-spermine) in 80% yield. Addition of 2 to a 2-fold excess of the reaction product of 1-hydroxy-2-pyridone-6-carboxylic acid (HOPO-C) and 1,1'-carbonyldiimidazole (CDI) in N,N-dimethylformamide (DMF) and deprotection with BBr3 gave 1,14-bis(2,3-dihydroxybenzoyl)-5,10-bis(1-hydroxy-2-pyridon-6-oyl) -1,5,10,14-tetraaza-tetradecane [3, 3,4,3-LI(diCAM-diHOPO)] in 5% yield. Addition of 2 to an equimolar amount of the reaction product of HOPO-C and CDI in N,N-dimethylacetamide (DMAA), purification of the hexadentate intermediate, subsequent treatment with an equimolar amount of 2,3-dimethoxybenzoyl chloride (DMB), and deprotection with BBr3 gave 1,5,14-tris(2,3-dihydroxybenzoyl)-10-(1-hydroxy-2-pyridon-6-oyl)-1 ,5,10,14- tetraazatetradecane [4, 3,4,3-LI(triCAM-HOPO)] in 5% yield. Ligands were administered to mice [30 mumol kg-1 ip at 1 h or orally at 3 min after iv injection of plutonium(IV)-238 citrate, kill at 24 h]. Plutonium excretion after injection of either CAM-HOPO ligand was 700% of that for 24-h Pu-injected controls, 140% of that for mice given the tetracatecholate analogue 3,4,3-LICAM (significantly more, p < 0.01), but only 80% of that promoted by 3,4,3-LIHOPO (significantly less). Orally administered 3,4,3-LI-(diCAM-diHOPO) promoted significantly more Pu excretion than an equimolar amount of CaNa3DTPA. Potency of the CAM-HOPO ligands for in vivo chelation of Pu(IV) resembled that of structurally hexadentate tris-(hydroxypyridinonate) and tris(sulfocatecholate) ligands and functionally hexadentate tetrakis-(sulfocatecholate) and tetrakis(carboxycatecholate) ligands. The Pu complexes of the CAM-HOPO ligands are to some degree unstable at pH < 7.4, as judged by Pu residues in kidneys in excess of 24-h Pu-injected controls. Synthetic yields were insufficient for chemical investigations or evaluation of acute toxicity.(ABSTRACT TRUNCATED AT 400 WORDS)

Actinoid Series Elements↗
PubMed2002

Highly antibacterial active aminoacyl penicillin conjugates with acylated bis-catecholate siderophores based on secondary diamino acids and related compounds.

New acylated bis-catecholates and 1,3-benzoxazine-2,4-dione derivatives based on secondary diamino acids (N-(aminoalkyl)glycines, N-aminopropyl-alanine, and N-aminopropyl-4-aminovaleric acid), on N-(aminoalkyl)aminomethyl benzoic acids, on N-(aminoalkyl)aminomethyl phenoxyacetic acids, or on 3,5-diaminobenzoic acid were synthesized as artificial siderophores. The corresponding diamino acids were obtained from the diamines and oxocarboxylic acids by catalytic hydrogenation. The acylated bis-catecholates and 1,3-benzoxazine-2,4-diones were coupled with ampicillin or amoxicillin to new siderophore aminoacylpenicillin conjugates. These conjugates exhibited very strong antibacterial activity in vitro against Gram-negative bacterial pathogens including Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Escherichia coli, Klebsiella pneumoniae, and Serratia marcescens. The ampicillin derivative 7b (HKI 9924154) and the corresponding amoxicillin derivative 8 (HKI 9924155) represent the most active compounds. The conjugates can use bacterial iron siderophore uptake routes to penetrate the Gram-negative outer membrane permeability barrier. This was demonstrated by assays with mutants deficient in components of the iron transport systems. New siderophore penicillin V conjugates with the siderophore component attached to the phenyl ring of penicillin V are inactive against these Gram-negative bacteria.

Amino Acids↗
PubMed2002

Naphthalene diols: a new class of antioxidants intramolecular hydrogen bonding in catechols, naphthalene diols, and their aryloxyl radicals.

1,8-Naphthalenediol, 5, and its 4-methoxy derivative, 6, were found to be potent H-atom transfer (HAT) compounds on the basis of their rate constants for H-atom transfer to the 2,2-di(4-t-octylphenyl)-1-picrylhydrazyl radical (DOPPH*), k(ArOH/DOPPH)*, or as antioxidants during inhibited styrene autoxidation, k(ArOH/ROO)*, initiated with AIBN. The rate constants showed that 5 and 6 are more active HAT compounds than the ortho-diols, catechol, 1, 2,3-naphthalenediol, 2, and 3,5-di-tert-butylcatechol, 3. Compound 6 has almost twice the antioxidant activity, k(ArOH/ROO)* = 6.0 x 10(6) M(-)(1) s(-1), of that of the vitamin E model compound, 2,2,5,7,8-pentamethyl-6-chromanol, 4. Calculations of the O-H bond dissociation enthalpies compared to those of phenols, (deltaBDEs), of 1-6 predict a HAT order of reactivity of 2 < 1 < 3 approximately 4 < 5 < 6 in general agreement with kinetic results. Calculations on the diols show that intramolecular H-bonding stabilizes the radicals formed on H-atom transfer more than it does the parent diols, and this effect contributes to the increased HAT activity of 5 and 6 compared to the activities of the catechols. For example, the increased stabilization due to the intramolecular H-bond of 5 radical over 5 parent of 8.6 kcal/mol was about double that of 2 radical over 2 parent of 4.6 kcal/mol. Linear free energy plots of log k(ArOH/DOPPH)* and log k(ArOH/ROO)* versus deltaBDEs for compounds 1-6 along with available literature values for nonsterically hindered monophenols placed the compounds on common scales. The derived Evans-Polanyi constants from the plots for the two reactions, alpha(DOPPH)* = 0.48 > alpha(ROO)* = 0.32, gave the expected order, since the ROO* reaction is more exothermic than the DOPPH* reaction. Compound 6 is sufficiently reactive to react directly with oxygen, and it lies off the log k(ArOH/ROO)* versus deltaBDE plot.

Antioxidants↗
PubMed2002

Synthesis of a new fluorescent probe specific for catechols.

[reaction: see text] The synthesis of a new fluorescent probe, specific for the catechol moiety, has been conducted by preparation of alpha,alpha-dibromomalonamides containing an appropriate fluorophore. N,N'-Bis-anthracen-9-ylmethyl-2,2-dibromomalonamide reacted with various catechols in the presence of cesium carbonate to generate highly fluorescent derivatives.

Anthracenes↗
PubMedDate not supplied

Synthesis and characterization of estrogen 2,3- and 3,4-quinones. Comparison of DNA adducts formed by the quinones versus horseradish peroxidase-activated catechol estrogens.

Catechol estrogens (CE) are among the major metabolites of estrone (E1) and 17 beta-estradiol (E2). Oxidation of these metabolites to semiquinones and quinones could generate ultimate carcinogenic forms of E1 and E2. The 2,3- and 3,4-quinones of E1 and E2 were synthesized by MnO2 oxidation of the corresponding CE, following the method for synthesizing E1-3,4-quinone [Abul-Hajj (1984) J. Steroid Biochem. 21, 621-622]. Characterization of these compounds was accomplished by UV, nuclear magnetic resonance, and mass spectrometry. The relative stability of these compounds was determined in DMSO/H2O (2:1) at room temperature, and the 3,4-quinones were more stable than the 2,3-quinones. The four quinones directly reacted with calf thymus DNA to form DNA adducts analyzed by the 32P-postlabeling method. The adducts were compared to those formed when the corresponding CE were activated by horseradish peroxidase (HRP) to bind to DNA. The E1- and E2-2,3-quinones formed much higher levels of DNA adducts than the corresponding 3,4-quinones. In addition, many of the adducts (70-90%) formed by the E1- and E2-2,3-quinones appeared to be the same as those formed by activation of 2-OHE1 or 2-OHE2 by HRP to bind to DNA. Little overlap was observed between the adducts formed by E1- and E2-3,4-quinones and HRP-activated 4-OHE1 and 4-OHE2. These results suggest that semiquinones and/or quinones are ultimate reactive intermediates in the peroxidatic activation of catechol estrogens.

Autoradiography↗
PubMed2003

Spectroscopic characterization of the 4-hydroxy catechol estrogen quinones-derived GSH and N-acetylated Cys conjugates.

Estrogens, including the natural hormones estrone (E(1)) and estradiol (E(2)), are thought to be involved in tumor induction. Specifically, catechol estrogen quinones (CEQs) derived from the catechol estrogens 4-hydroxyestrone (4-OHE(1)) and 4-hydroxyestradiol (4-OHE(2)) react with DNA and form DNA adducts (Cavalieri, E. L., et al. (1997) Proc. Natl Acad. Sci. U.S.A. 94, 10037). CEQs are also conjugated with GSH, a reaction that prevents damage to DNA, providing biomarkers of exposure to CEQs. Current detection limits for these analytes by HPLC with multichannel electrochemical detection are in the picomole range (Devanesan, P., et al. (2001) Carcinogenesis 22, 489). To improve the detection limit of CEQ-derived conjugates, spectrophotometric monitoring was investigated. Fluorescence and/or phosphorescence spectra of the 4-OHE(1), 4-OHE(2), Cys, N-acetylcysteine (NAcCys), 4-OHE(1)-2-SG, and 4-OHE(2)-2-SG conjugates and their decomposition products 4-OHE(1)-2-NAcCys and 4-OHE(2)-2-NAcCys were obtained at 300 and 77 K. It is shown that (i) 4-OHE(1)- and 4-OHE(2)-derived SG and NAcCys conjugates are weakly fluorescent at 300 K (with the emission maximum at 332 nm) but strongly phosphorescent at 77 K; (ii) Cys and NAcCys exhibit fluorescence and phosphorescence only at 77 K; and (iii) 4-OHE(1) and 4-OHE(2) are weakly fluorescent at 300 and 77 K and not phosphorescent. The phosphorescence spectra of SG and NAcCys conjugates are characterized by a weak origin band at approximately 383 nm and two intense vibronic bands at 407 and 425 nm. After they are cooled from 300 to 77 K, the total luminescence intensity of SG and NAcCys conjugates increases by a factor of approximately 150 predominantly due to phosphorescence enhancement. Theoretical calculations revealed, in agreement with the experimental data, that the lowest singlet (S(1)) and triplet (T(1)) states of 4-OHE(2)-2-NAcCys are of n,pi* and pi,pi* character, respectively, leading to a large intersystem crossing yield and strong phosphorescence. The limit of detection (LOD) for CEQ-derived conjugates, based on phosphorescence measurements, is in the low femtomole range. The concentration LOD is approximately 10(-9) M. Therefore, we propose that capillary electrophoresis interfaced with low temperature phosphorescence detection can be used to test for human exposure to CEQs by analyzing urine.

Acetylcysteine↗
PubMed2005

Tyrosinase-catalyzed oxidation of 17beta-estradiol: structure elucidation of the products formed beyond catechol estrogen quinones.

This paper reports a systematic characterization of the products formed by oxidation of 17beta-estradiol (1) with tyrosinase/O2 at low concentrations of physiological relevance. With the substrate at 1-10 nM concentration, the main reaction products included, beside the catechol estrogens 2-hydroxyestradiol (2) and 4-hydroxyestradiol (3), 6-oxo-2-hydroxyestradiol (4), 9,11-dehydro-2-hydroxyestradiol (6), 6,7-dehydro-2-hydroxyestradiol (7), and 9,11-dehydro-4-hydroxyestradiol (10). At higher estradiol concentrations, e.g., 1 microM, 6,7,8,9-dehydro-2-hydroxyestradiol (5) and the dimeric products 8 and 9 were also formed. The origin of these products from oxidative routes of 2 and 3 was established. Overall, the results of this study disclose novel aspects of the reactivity of 1 with the tyrosinase/O2 system and provide the first inventory of the oxidation products of catechol estrogen quinones.

Catalysis↗
PubMedDate not supplied

Identification of catechol and hydroquinone metabolites of 4-monochlorobiphenyl.

Polychlorinated biphenyls (PCBs) may be metabolically activated to electrophiles, which bind to proteins and nucleic acids. One activation scheme involves the formation of reactive arene oxide intermediates during cytochrome P450-catalyzed hydroxylation. We propose a second activation pathway whereby PCB catechol and hydroquinone metabolites may be oxidized to reactive semiquinones and/or quinones. By employing 4-monochlorobiphenyl (4-MCB) as a model substrate and liver microsomes from rats treated with phenobarbital and 3-methyl-cholanthrene, five monol and three diol metabolites were identified. The major metabolite was 4-chloro-4'-monohydroxybiphenyl, followed by, in decreasing order, 4-chloro-3',4'-dihydroxybiphenyl, unknown B (a monol), 4-chloro-2',3'-dihydroxybiphenyl, 4-chloro-3'-hydroxybiphenyl, 4-chloro-2',5'-dihydroxybiphenyl, unknown A (a monol), and 4-chloro-2'-monohydroxybiphenyl. A trace of a dihydrodiol was detected by GC/MS. To elucidate the source of the diols, 4-MCB and the synthetic monol metabolites 4-chloro-2'-/-3'-/-4'-monohydroxybiphenyls were each employed as substrates in incubations with microsomes from rats treated with phenobarbital, 3-methylcholanthrene, or both inducers. The three diol metabolites were all produced from 4-MCB in incubations with microsomes from 3-methylcholanthrene-treated rats, but incubations with microsomes from phenobarbital-treated rats did not yield detectable amounts of 4-chloro-2',3'-dihydroxybiphenyl. 4-Chloro-2',3'-dihydroxybiphenyl was only found as a product of 4-chloro-2'-monohydroxybiphenyl. The 4-chloro-2',5'-dihydroxybiphenyl was found in extracts of incubations with 4-chloro-2'- and -3'-monohydroxybiphenyls, while the 4-chloro-3',4'-dihydroxybiphenyl was the only product found from 4-chloro-3'- and -4'-monohydroxybiphenyls. No other chlorinated diols were detected by GC/MS. These data suggest that the major route of biosynthesis of the diols was via a second hydroxylation step and not aromatization of dihydrodiols derived from primary arene oxides. We propose a scheme for the in vitro synthesis of the catechol and hydroquinone metabolites, which may be precursors for electrophilic semiquinone or quinone products with the potential for cytotoxic and genotoxic effects.

Animals↗
PubMedDate not supplied

Molecular characteristics of catechol estrogen quinones in reactions with deoxyribonucleosides.

Estrogens can have two roles in the induction of cancer: stimulating proliferation of cells by receptor-mediated processes, and generating electrophilic species that can covalently bind to DNA. The latter role is thought to proceed through catechol estrogen metabolites, which can be oxidized to o-quinones that bind to DNA. Four estrogen-deoxyribonucleoside adducts were synthesized by reaction of estrone 3,4-quinone (E1-3,4-Q), 17 beta-estradiol 3,4-quinone (E2-3,4-Q), or estrone 2,3-quinone (E1-2,3-Q) with deoxyguanosine (dG) or deoxyadenosine (dA) in CH3CO2H/H2O (1:1). Reaction of E1-3,4-Q or E2-3,4-Q with dG produced specifically 7-[4-hydroxyestron-1(alpha, beta)-yl]guanine (4-OHE1-1(alpha, beta)-N7Gua) or 7-[4-hydroxyestradiol-1(alpha, beta)-yl]-guanine (4-OHE2-1(alpha, beta)-N7Gua), respectively, in 40% yield, with loss of deoxyribose. These two quinones did not react with dA, deoxycytidine, or thymidine. When E1-2,3-Q was reacted with dG or dA, N2-(2-hydroxyestron-6-yl)deoxyguanosine (2-OHE1-6-N2dG, 10% yield) and N6-(2-hydroxyestron-6-yl)deoxyadenosine (2-OHE1-6-N6dA, 80% yield), respectively, were formed. These adducts provide insight into the type of DNA damage that can be caused by o-quinones of the catechol estrogens. The estrogen 3,4-quinones are expected to produce depurinating guanine adducts that are lost from DNA, generating apurinic sites, whereas the 2,3-quinones would form stable adducts that remain in DNA, unless repaired. The adducts reported here will be used as references in studies to elucidate the structure of estrogen adducts in biological systems.

Chromatography, High Pressure Liquid↗
PubMed2000

Purification and catalytic properties of two catechol 1,2-dioxygenase isozymes from benzoate-grown cells of Acinetobacter radioresistens.

Two catechol 1,2-dioxygenase (C1,2O) isozymes (IsoA and IsoB) have been purified to homogeneity from a strain of Acinetobacter radioresistens grown on benzoate as the sole carbon and energy source. IsoA and IsoB are both homodimers composed of a single type of subunit with molecular mass of 38,600 and 37,700, Da respectively. In conditions of low ionic strength, IsoA can aggregate as a trimer, in contrast to IsoB, which maintains the dimeric structure, as also supported by the kinetic parameters (Hill numbers). IsoA is identical to the enzyme previously purified from the same bacterium grown on phenol, whereas the IsoB is selectively expressed using benzoate as carbon source. This is the first evidence of the presence of differently expressed C1,2O isozymes in A. radioresistens or more generally of multiple C1,2O isozymes in benzoate-grown Acinetobacter cells. Purified IsoA and IsoB contain approximately 1 iron(III) ion per subunit and both show electronic absorbance and EPR features typical of Fe(III) intradiol dioxygenases. The kinetic properties of the two enzymes such as the specificities toward substituted catechols, the main catalytic parameters, and their behavior in the presence of different kind of inhibitors are, unexpectedly, very similar, in contrast to most of the previously known dioxygenase isozymes.

Acinetobacter↗
PubMed1998

Novel catecholate-type siderophore analogs based on a myo-inositol scaffold.

A novel 1,3,5-triamino-myo-inositol derivative is presented as a readily available scaffold for the design of tripodal siderophore mimetics. Based on this scaffold, various hexadentate catecholate-type siderophore analogs were synthesized by attaching the catechols to the inositol scaffold via spacer units of different structure and length. The potential to tune the polarity of the inositol containing siderophore analogs has also been demonstrated by varying the protection group strategy. The siderophore activity of the prepared siderophore analogs was examined by cross-feeding tests with various Gram-negative bacteria and mycobacteria.

Catechols↗
PubMed2001

Plant catechols prevent lipid peroxidation in human plasma and erythrocytes.

The antioxidant activity of several plant catechol derivatives was tested in buffer, plasma, and human erythrocytes. In buffer, chlorogenic acid (CGA), caffeic acid (CA), and dihydrocaffeic acid (DCA) reduced ferric iron equally well in the ferric reducing antioxidant power (FRAP) assay. Low concentrations of the polyphenols enhanced the ability of plasma to reduce ferric iron by about 10%. In plasma, lipid hydroperoxide and F2-isoprostane formation induced by a water-soluble free radical initiator were reduced by CGA at concentrations as low as 20 microM. During incubation at 37 degrees C, human erythrocytes took up DCA, but not CGA, and intracellular DCA enhanced the ability of erythrocytes to reduce extracellular ferricyanide. When intact erythrocytes were exposed to oxidant stress generated by liposomes containing small amounts of lipid hydroperoxides, extracellular CGA at a concentration of 5 microM decreased both lipid peroxidation in the liposomes, and spared alpha-tocopherol in erythrocyte membranes. These results suggest that the catechol structure of these compounds convey the antioxidant effect in plasma and in erythrocytes.

Antioxidants↗
PubMed2002

Catechol-O-methyltransferase polymorphism and endometriosis.

PURPOSE: Catechol-O-methyltransferase (COMT) inactivates the estradiol metabolites, 2-hydroxy and 4-hydroxy catechols, which have been implicated in the pathogenesis of endometriosis. A COMT valine to methionine polymorphism (G-to-A) in exon 4 of the COMT gene is polymorphic in the human population, with 25% of Caucasians being homozygous for the low-activity allele (COMT-L) of the enzyme. In a case-control study we investigated whether this COMT polymorphism is associated with endometriosis. METHODS: Polymerase chain reaction was performed to analyze the COMT genotype among women with surgically and histologically confirmed endometriosis (study group; n = 91) and in women without evidence of endometriosis confirmed by laparoscopy or laparotomy (control group; n = 92). RESULTS: Allele frequencies for the low-activity allele (COMT-L) among women with endometriosis and controls were 0.50 and 0.50, respectively (p = 0.999; odds ratio = 1.0, 95% CI: 0.66-1.51). CONCLUSIONS: Our results suggest that the valine to methionine polymorphism in exon 4 of the COMT gene is not associated with the risk of endometriosis compared to a surgical control population.

Adolescent↗
PubMedDate not supplied

[Catechol siderophore, produced by thermoresistent strain of Bacillus licheniformis VK21].

Thermophilic and thermoresistant strains of bacilli were screened on a medium containing Chrome Azurol S for producers of siderophores. It was found that the Bacillus licheniformis VK21 strain dramatically increases secretion of the metabolite, a chelator of Fe3+, in response to addition of manganese(II) salts. The growth of the producer on a minimum medium containing MnSO4 under the conditions of iron deficiency is accompanied by the accumulation of a catechol product, the content of which reaches a maximum at the beginning of the stationary growth phase of culture. In the presence of FeCl3, the amount of the catechol product in the medium considerably decreases. The siderophore, called SVK21, was isolated from the cultural medium and purified by reversed phase HPLC, and its siderophore function was confirmed by the test for the restoration of growth of producer cells in a medium containing EDTA. The UV spectrum of the siderophore has absorption maxima at 248 and 315 nm. According to amino acid analysis and NMR spectrometry, the metabolite SVK21 is 2,3-dihydroxybenzoyl-glycyl-threonine. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2003, vol. 29, no. 6; see also http://www.maik.ru.

Bacillus↗
PubMed2004

Human catechol O-methyltransferase genetic variation: gene resequencing and functional characterization of variant allozymes.

Catechol O-methyltransferase (COMT) plays an important role in the metabolism of catecholamines, catecholestrogens and catechol drugs. A common COMT G472A genetic polymorphism (Val108/158Met) that was identified previously is associated with decreased levels of enzyme activity and has been implicated as a possible risk factor for neuropsychiatric disease. We set out to 'resequence' the human COMT gene using DNA samples from 60 African-American and 60 Caucasian-American subjects. A total of 23 single nucleotide polymorphisms (SNPs), including a novel nonsynonymous cSNP present only in DNA from African-American subjects, and one insertion/deletion were observed. The wild type (WT) and two variant allozymes, Thr52 and Met108, were transiently expressed in COS-1 and HEK293 cells. There was no significant change in level of COMT activity for the Thr52 variant allozyme, but there was a 40% decrease in the level of activity in cells transfected with the Met108 construct. Apparent K(m) values of the WT and variant allozymes for the two reaction cosubstrates differed slightly, but significantly, for 3,4-dihydroxybenzoic acid but not for S-adenosyl-L-methionine. The Met108 allozyme displayed a 70-90% decrease in immunoreactive protein when compared with WT, but there was no significant change in the level of immunoreactive protein for Thr52. A significant decrease in the level of immunoreactive protein was also observed in hepatic biopsy samples from patients homozygous for the allele encoding Met108. These observations represent steps toward an understanding of molecular genetic mechanisms responsible for variation in COMT level and/or properties, variation that may contribute to the pathophysiology of neuropsychiatric disease.

Animals↗
PubMed2005

Electrochemical oxidation of catecholamines and catechols at carbon nanotube electrodes.

The differences in the electrochemical oxidation of two commonly known catecholamines, dopamine and norepinephrine, and one catechol, dihydroxyphenylacetic acid (DOPAC), at three different types of carbon based electrodes comprising conventionally polished glassy carbon (GC), nitrogen-doped carbon nanotubes (N-CNTs), and non-doped CNTs were assessed. Raman microscopy and X-ray photoelectron spectroscopy (XPS) were employed to evaluate structural and compositional properties. Raman measurements indicate that N-CNT electrodes have ca. 2.4 times more edge plane sites over non-doped CNTs. XPS data show no evidence of oxygen functionalities at the surface of either CNT type. N-CNTs possess 4.0 at. % nitrogen as pyridinic, pyrrolic, and quaternary nitrogen functionalities that result in positively charged carbon surfaces in neutral and acidic solutions. The electrochemical behavior of the various carbon electrodes were investigated by cyclic voltammetry conducted in pH 5.8 acetate buffer. Semiintegral analysis of the voltammograms reveals a significant adsorptive character of dopamine and norepinephrine oxidation at N-CNT electrodes. Larger peak splittings, DeltaE(p), for the cyclic voltammograms of both catecholamines and a smaller DeltaE(p) for the cyclic voltammogram for DOPAC at N-CNT electrodes suggest that electrostatic interactions hinder oxidation of cationic dopamine and norepinephrine, but facilitate anionic DOPAC oxidation. These observations were supported by titrimetry of solid suspensions to determine the pH of point of zero charge (pH(pzc)) and estimate the number of basic sites for both CNT varieties. This study demonstrates that carbon purity, the presence of exposed edge plane sites, surface charge, and basicity of CNTs are important factors for influencing adsorption and enhancing the electrochemical oxidation of catecholamines and catechols.

Catecholamines↗