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PubMed2001

Photogeneration of singlet oxygen (1O2) and free radicals (Sen*-, O2*-) by tetra-brominated hypocrellin B derivative.

To improve photodynamic activity of the parent hypocrellin B (HB), a tetra-brominated HB derivative (compound 1) was synthesized in high yield. Compared with HB, compound 1 has enhanced red absorption and high molar extinction coefficients. The photodynamic action of compound 1, especially the generation mechanism and efficiencies of active species (Sens*-, O2*- and 1O2) were studied using electron paramagnetic resonance (EPR) and spectrophotometric methods. In the deoxygenated DMSO solution of compound 1, the semiquinone anion radical of compound 1 is photogenerated via the self-electron transfer between the excited and ground state species. The presence of electron donor significantly promotes the reduction of compound 1. When oxygen is present, superoxide anion radical (O2*-) is formed via the electron transfer from Sens*- to the ground state molecular oxygen. The efficiencies of Sens*- and O2*- generation by compound 1 are about three and two times as much as that of HB, respectively. Singlet oxygen (1O2) can be produced via the energy transfer from triplet compound 1 to ground state oxygen molecules. The quantum yield of singlet oxygen (1O2) is 0.54 in CHCl3 similar to that of HB. Furthermore, it was found that the accumulation of Sens*- would replace that of O2*- or 1O2 with the depletion of oxygen in the sealed system.

Benzoquinones↗
PubMed2003

Derivatisation for liquid chromatography/electrospray mass spectrometry: synthesis of pyridinium compounds and their amine and carboxylic acid derivatives.

A simple method has been developed for the pre-column derivatisation of low molecular weight primary and secondary amines and carboxylic acids using quaternary nitrogen compounds to enhance their detection by liquid chromatography/electrospray ionisation mass spectrometry (LC/ESI-MS). The synthesis of seven novel quaternary nitrogen reagents is described. The derivatives are designed to be relatively small molecules to avoid some of the steric hindrance problems that may be associated with larger derivatisation reagents. The compounds have amine and carboxylic acid functional groups with which to derivatise carboxylic acids and amines, respectively. Two of the compounds contain a bromine atom in order to assess the advantages of a bromine isotope pattern in the mass spectra. This acts as a simple marker for derivatisation and enables data processing by cluster analysis. Activation of the carboxylic acid group was achieved by the use of either 1-chloro-4-methylpyridinium iodide (CMPI) or the more reactive 1-fluoro-4-methylpyridinium p-toluenesulphonate (FMP).1 Using both of these active reagents, the degree of nucleophilic substitution was investigated for the derivatisation of a variety of small molecules. Whilst giving some increase in the ESI-MS response for the derivatised compounds, the FMP itself acted as a derivatising reagent in a competing reaction. In the light of this finding, FMP was reacted with the test compounds separately and gave positive results as a derivatising reagent. Detection of the 'pre-charged' derivatives of amines and carboxylic acids by LC/ESI-MS was investigated with respect to their ESI response and chromatography.

Journal Article↗
PubMed2005

Hydride affinities of borane derivatives: novel approach in determining the origin of lewis acidity based on triadic formula.

The problem of intrinsic Lewis acidities of simple boron compounds (BH3-mXm, m = 0-3, X = F, Cl, Br, CH3, and OH) is assessed by their gas-phase hydride affinities (HAs). A simple and intuitively appealing picture of the interaction process including detachment of an electron from the hydride ion H-, capture of the pruned electron to the investigated Lewis acid (LA), and subsequent formation of the homolytic chemical bond between two newly created radicals is proposed. It enables transparent and straightforward dissection of the initial and final state effects, which taken together with the intermediate relaxation stabilization determine the trend of changes in the hydride affinities. The former effect is reflected in the electron affinities of the neutral Lewis acids given within Koopmans' approximation, while the final state effect involves properties of the formed Lewis acid-base adducts mirrored in the bond dissociation energy of the formed [LA-H]- chemical bond. It is demonstrated that unexpectedly low Lewis acidity of fluoroboranes relative to the corresponding chlorine and bromine derivatives can be traced down to the unfavorable Koopmans' electron affinities. Hence, it is a consequence of the initial state effect. In contrast, chloroboranes are more potent Lewis acids than fluoroboranes, because the relaxation and final state effects decisively influence their Lewis acidity. Finally, bromine-substituted borane compounds provide the most powerful studied Lewis acids. Their hydride affinities are result of a synergic interplay of the initial state, intermediate stabilization via relaxation, and final state effects. It is shown that Pearson's global hardness indices defined within his hard and soft acid-base (HSAB) principle fail to adequately predict and interpret the calculated hydride affinities.

Journal Article↗
PubMed1999

Halogenated environmental contaminants in perch (Perca fluviatilis) from Latvian coastal areas.

The environmental contamination situation in coastal areas of the former Soviet Union has up to now been more or less unknown. This study on perch (Perca fluviatilis), collected at three locations along the coast of Latvia during 1994 and 1995, provides concentrations of several ubiquitous environmental contaminants (PCBs, HCB, HCHs, 4,4'-DDT, 4,4'-DDE, 4,4'-DDD, trans-Nonachlor, 2,2',4,4'-tetrabromodiphenyl ether). The concentrations of total PCB were similar at all study locations [0.7-1.4 ppm on a lipid weight (l.w.) basis], although a site close to the City of Riga indicated the presence of a local PCB contamination source. The contamination source was identified mainly by a higher relative content of lower chlorinated PCB congeners in the samples. Local pollution sources were also indicated for HCH and DDT. A large variation in the HCH isomer composition between 1994 and 1995 at one location demonstrates short half-lives of HCHs in the environment. The brominated flame retardant compound 2,2',4,4'-tetrabromdiphenyl ether was present in the range of 6.4-10 ng/g l.w. in the perch. The clean-up method applied in this study allowed for quantification of two semi-polar contaminants frequently overlooked in Baltic biota, namely Dieldrin and bis(4-chlorophenyl) sulfone (BCPS). Concentrations of BCPS were remarkably high, i.e. in the same magnitude as the most abundant PCB congeners. The results presented shows that the contamination of, e.g. PCB in an area of the former Soviet Union, the Gulf of Riga, is similar to that observed in other parts of the Baltic area.

Animals↗
PubMed2006

POPs and organic polysufides in sediments of Lake Ladoga.

The study included one station close to a pollution source (depth 59 m) and another far from polluted areas (depth 40 m). Samples were analysed for organic chlorine, bromine and sulfur compounds. Samples taken with a corer were sliced to the layers of 0-1, 1-4, 4-7 cm etc. down to the depth of 34 cm. The dating was made with two independent methods, the 210Po method and with the soot particle counting method. The analyses were made with a multiresidue method. Gas chromatography was connected to low resolution mass spectrometry (LRMS) or to high resolution mass spectrometry (HRMS). A different extraction was applied to screen the possible occurrence of polysulfides. Typical chlorophenol and chlorohydrocarbon traces from chlorobleaching of pulp were non-detectable. Also PCDDs, PCDFs, PCBs and various organochloride pesticides, fire retardant residues PBDEs, PBDDs and PBDFs and polychlorinated phenyl salicylates were not detected. Instead, methylated dibenzothiophenes Me-DBTs and Di-Me-DBTs, typical traces of oil based defoamers used in e.g. paper mills were found in the surface layers of the polluted site. Polysulfides were analyzed from layers representing years 1955-1970 from the polluted site. The structures of five congeners were according to GC/MS dimethyl trisulfide, 1,2,3,4-tetrathiepane, pentathiane, 1,2,3,4-tetrathiane and 1,2,4,5-tetrathiepane. Many of the analyzed pollutants have not been reported earlier from Lake Ladoga. The only positive observations were from oil-based defoamers used in paper mills, and from polysulfides, which are either of natural origin or indicate a discharge in the 1950s and 1960s. Owing to the large spreadout and dilution, the concentrations are low even at moderate distances from the pollution centers.

Chlorophenols↗
PubMedDate not supplied

Structure-mutagenicity and structure-cytotoxicity studies on bromine-containing cysteine S-conjugates and related compounds.

Glutathione and cysteine S-conjugates of several haloalkenes are nephrotoxic and cytotoxic. Chloroalkene-derived S-(1-chloroalkenyl)-L-cysteine conjugates, but not fluoroalkene-derived S-(2,2-dihalo-1,1-difluorethyl)-L-cysteine conjugates, are mutagenic in the Ames test, although both types of S-conjugates are cytotoxic and nephrotoxic. Recent studies showed that bromine-containing S-(2,2-dihalo-1,1-difluoroethyl)-L-cysteine conjugates are mutagenic in the Ames test, thus challenging the generalization that S-(2,2-dihalo-1,1-difluoroethyl)-L-cysteine conjugates are not mutagenic. Hence a series of bromine-containing and bromine-lacking S-(2,2-dihalo-1,1-difluoroethyl)-L-cysteine conjugates was prepared, and their mutagenicity was assessed in the Ames test with Salmonella typhimurium TA2638 as the test strain. In addition, several indices of cytotoxicity, including cytotoxicity in LLC-PK1 cells, induction of Ca2+ release from pig kidney mitochondria, and DNA double-strand breaks in LLC-PK1 cells, were measured. The bromine-containing S-conjugates S-(2-bromo-2-chloro-1,1-difluoroethyl)-L- cysteine (BCD-FC), S-(2-bromo-1,1,2-trifluoroethyl)-L-cysteine (BTFC), and S-(2,2-dibromo-1,1-difluoroethyl)-L-cysteine (DBDFC) were mutagenic in the Ames test, whereas S-(2-chloro-1,1,2-trifluorethyl)-L-cysteine (CTFC), S-(2,2-dichloro-1,1-difluoroethyl)-L-cysteine (DCDFC), and S-(1,1,2,2-tetrafluoroethyl)-L-cysteine (TFC), which lack bromine, were not. BCDFC, BTFC, CTFC, DBDFC, and TFC were cytotoxic in LLC-PK1 cells, and their cytotoxicity was blocked by the cysteine conjugate beta-lyase inhibitor (aminooxy)acetic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

5-(2-Oxo-3-indolinylidene)thiazolidine-2,4-dione-1,3-di-Mannich base derivatives: synthesis and evaluation for antileukemic activity.

A novel series of 5-(2-oxo-3-indolinylidene)thiazolidine-2,4-dione, having the 1- and 3-positions of the isatin and thiazolidine rings respectively, substituted by various Mannich bases, was prepared. Five compounds were evaluated for antileukemic activity against P388 lymphocytic leukemia in the mouse. The di-Mannich base with a dimethylamino component exhibited the highest activity of the tested compounds. Introduction of bromine into the aromatic moiety of isatin ring (position 5) increased the activity of the parent molecule to a smaller extent.

Amines↗
PubMed1989

Carcinogenic activity associated with halogenated acetones and acroleins in the mouse skin assay.

Several chlorinated acetones have been identified in drinking water and these, as well as a number of chlorinated acroleins, are produced by chlorination of humic acid solutions. Many of these chlorinated compounds and the brominated acrolein analog were positive in the Ames Assay in the laboratory. To determine if carcinogenic activity was associated with these chemicals the following acetone derivatives: monochloro (MCA); 1,1-dichloro (1,1-DCA), 1,3-dichloro (1,3-DCA), 1,1,1-trichloro (1,1,1-TCA), 1,1,3-trichloro (1,1,3-TCA), and substituted acroleins: 2-chloro (CAC), 3,3-dichloro (DCAC), 2,3,3-trichloro (TCAC) and 2-bromo (BAC), were applied topically to SENCAR mice (25, 30, or 40/group) at the following dose levels: 50 mg/kg (MCA and 1,1,3-TCA); 50, 75 and 100 mg/kg (1,3-DCA); 100, 200 and 400 mg/kg (CAC, DCAC, and TCAC); 200 and 300 mg/kg (BAC); and 400, 600, and 800 mg/kg (1,1-DCA, and 1,1,1-TCA). Doses were applied six times over a 2-week period in 0.2 ml ethanol per application. 1,3-DCA was also tested with single doses of 37.5, 75, 150 and 300 mg/kg in 0.2 ml ethanol. Control animals received 0.2 ml ethanol per application as a single dose or multiple doses to match corresponding studies. Two weeks after the final dose, 1.0 microgram TPA in 0.2 ml acetone was applied three times weekly for 20 weeks. After 24 weeks the percentage of animals with tumors for dose groups above were: MCA (8); 1,1,3-TCA (10); 1,3-DCA, multiple doses (48, 45, 32); CAC (30, 28, 38); DCAC (3, 0, 0); TCAC (10, 5, 0); BAC (54, 43); 1,1-DCA (0, 5, 0); 1,1,1-TCA (10, 5, 0); 1,3-DCA, single doses (47, 47, 63, 20); controls (12--Table 3, 9--Table 4 average). These data show that 1,3-DCA, CAC and BAC, when applied topically, initiate tumors in the mouse skin. These chemicals administered orally in a 2% emulphor solution, at doses described in Table 3, did not initiate tumors in the mouse skin.

Acetone↗
PubMed2002

Psammaplin A, a chitinase inhibitor isolated from the Fijian marine sponge Aplysinella rhax.

Several brominated tyrosine derived compounds, psammaplins A (1), K (2) and L (3) as well as bisaprasin (4) were isolated from the Fijian marine sponge Aplysinella rhax during a bioassay guided isolation protocol. Their structures were determined using NMR and MS techniques. Psammaplin A was found to moderately inhibit chitinase B from Serratia marcescens, the mode of inhibition being non-competitive. Crystallographic studies suggest that a disordered psammaplin A molecule is bound near the active site. Interestingly, psammaplin A was found to be a potent antifungal agent.

Animals↗
PubMed2005

Synthesis and structure of Ta4S9Br8. An emergent family of early transition metal chalcogenide clusters.

Single crystals of Ta4S9Br8 are obtained by heating Ta, S, and Br2 at 400 degrees C in a 4.0:9.0:4.0 molar ratio in a 44% yield. The structure was determined by X-ray analysis and consists of molecular clusters [Ta4(mu4-S)(mu-S2)4Br8]. The tantalum atoms form a square with long Ta...Ta distances (3.30 angstroms), with four S2 ligands bridging the Ta-Ta edges and one capping the square. Each Ta atom has two terminal bromine atoms. The compound is diamagnetic and has only two electrons for metal-metal bonding. IR and Raman spectral studies with the use of 34S allow to identify characteristic vibrations S-S (537 cm(-1)) and Ta4-mu4-S (407 cm(-1)). The compound is soluble in CH3CN, giving a dark-red solution with a characteristic electronic spectrum, which was assigned on the base of DFT calculations. ESI-MS spectra of the solutions show formation of [[Ta4S9Br8]Br]- associates.

Journal Article↗
PubMed1994

The metal-ion-free oxidoreductase from Streptomyces aureofaciens has an alpha/beta hydrolase fold.

The crystal structure of the bromoperoxidase A2 from Streptomyces aureofaciens (ATCC 10762) has been determined by isomorphous replacement and refined to 2.05 A resolution with an R-value of 18.4%. The enzyme catalyzes the bromination of organic compounds in the presence of bromide and peroxide. The structure confirms the absence of cofactors such as metal ions or haem groups and shows the general topology of the alpha/beta hydrolase fold. The active centre is at the end of a deep pocket and includes a catalytic triad of Ser 98, Asp 228 and His 257. The active centre is connected by a narrow tunnel to a second pocket on the enzyme surface.

Amino Acid Sequence↗
PubMed2003

Role of Acinetobacter calcoaceticus 3,4-dihydrocoumarin hydrolase in oxidative stress defence against peroxoacids.

The physiological role of a bifunctional enzyme, 3,4-dihydrocoumarin hydrolase (DCH), which is capable of both hydrolysis of ester bonds and organic acid-assisted bromination of organic compounds, was investigated. Purified DCH from Acinetobacter calcoaceticus F46 catalysed dose- and time-dependent degradation of peracetic acid. The gene (dch) was cloned from the chromosomal DNA of the bacterium. The dch ORF was 831 bp long, corresponding to a protein of 272 amino acid residues, and the deduced amino acid sequence showed high similarity to those of bacterial serine esterases and perhydrolases. The dch gene was disrupted by homologous recombination on the A. calcoaceticus genome. The dch disruptant strain was more sensitive to growth inhibition by peracetic acid than the parent strain. On the other hand, the recombinant Escherichia coli cells expressing dch were more resistant to peracetic acid. A putative catalase gene was found immediately downstream of dch, and Northern blot hybridization analysis revealed that they are transcribed as part of a polycistronic mRNA. These results suggested that in vivo DCH detoxifies peroxoacids in conjunction with the catalase, i.e. peroxoacids are first hydrolysed to the corresponding acids and hydrogen peroxide by DCH, and then the resulting hydrogen peroxide is degraded by the catalase.

Acinetobacter calcoaceticus↗
PubMed1983

Allergic contact dermatitis due to highly reactive halogenated compounds.

10 cases of dermatitis in a fine organic chemicals plant are reported. These cases were all due to exposure to chemical compounds with reactive bromine or chlorine atoms. This type of chemical is always extremely irritant, but evidence is put forward to suggest that these cases were the result of allergic sensitization. Chemicals with reactive halogen atoms should always be handled with extreme care and patch testing should be approached with caution.

Adult↗
PubMed1985

Purification and characterization of hydrolytic haloalkane dehalogenase from Xanthobacter autotrophicus GJ10.

A new enzyme, haloalkane dehalogenase, was isolated from the 1,2-dichloroethane-utilizing bacterium Xanthobacter autotrophicus GJ10. The purified enzyme catalyzed the hydrolytic dehalogenation of n-halogenated C1 to C4 alkanes, including chlorinated, brominated, and iodinated compounds. The highest activity was found with 1,2-dichloroethane, 1,3-dichloropropane, and 1,2-dibromoethane. The enzyme followed Michaelis-Menten kinetics, and the Km for 1,2-dichloroethane was 1.1 mM. Maximum activity was found at pH 8.2 and 37 degrees C. Thiol reagents such as p-chloromercuribenzoate and iodoacetamide rapidly inhibited the enzyme. The protein consists of a single polypeptide chain of a molecular weight of 36,000, and its amino acid composition and N-terminal sequence are given.

Amino Acid Sequence↗
PubMed1983

The metabolism of tryptophan and 7-chlorotryptophan in Pseudomonas pyrrocinia and Pseudomonas aureofaciens.

Pseudomonas pyrrocinia ATCC 15958 and a mutant strain (ACN) of Pseudomonas aureofaciens ATCC 15926 possess a mechanism for the degradation of the tryptophan side chain. Indole, indole-3-carboxylic acid, indole-3-acetic acid and the corresponding compounds chlorinated or brominated at position 7, as well as indole-3-pyruvate and 7-chloroindole-3-pyruvate, were isolated from bacterial cultures. The chlorinated indole derivatives were isolated after the addition of 7-chloro-DL-tryptophan to cultures of P. pyrrocinia whereas their bromo analogues were found in the culture medium of the mutant strain ACN of P. aureofaciens, grown in the presence of sodium bromide. Enzymatic studies show that tryptophan is transaminated to indole-3-pyruvate, which is transformed to indole-3-acetaldehyde. Dehydrogenation of indole-3-acetaldehyde leads to indole-3-acetic acid, which is further metabolized to indole-3-carboxaldehyde, and converted by dehydrogenation to indole-3-carboxylic acid. Indole is formed by the spontaneous decarboxylation of indole-3-carboxylic acid.

Amino Acid Isomerases↗
PubMed1999

Synthesis of 3-aryl-1-[(4-phenyl-1-piperazinyl)butyl]indazole derivatives and their affinity to 5-HT1A serotonin and dopamine D1 receptors.

Eight 3-arylindazole derivatives have been synthesized and their affinity to 5-HT1A serotonin and D1 dopamine receptors was investigated by radioligand analysis. Quantitative structure-activity relationships were studied using the Free-Wilson model. An increase in affinity to dopamine D1 receptors within substituents Br > Cl > CH3 at the 5-position of the 3-arylindazole molecule has been observed. Addition of a chlorine atom to the ortho-position the of phenyl ring let to even highest activity. Replacement of the hydrogen atom at the first position of the 3-arylindazole on the (phenylpiperazine)butyl substituent caused an increase of affinity and did not change the trends of affinity dependence on structure. An inverse dependence on the structure of the studied compounds was observed for the serotonin 5-HT1A receptors. Compounds containing a methyl group at the 5-position of molecule were more active than compounds containing halogens. A chlorine atom at the ortho-position of the phenyl ring decreased affinity. Replacement of the hydrogen atom at the first position of the molecule on the phenylpiperazine)butyl substituent led to an increase in affinity. Selectivity of the studied compounds varied within a wide range. Generally, the presence of the 3-aryl-indazole fragment in the new buspirone analogues increased their affinity to dopamine receptors and reduced their affinity to serotonin receptors. Compounds containing a bromine atom in the 3-arylindazole moiety may be promising ligands for D1 receptors.

8-Hydroxy-2-(di-n-propylamino)tetralin↗