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PubMed2006

A method for measuring semi- and non-volatile organic halogens by combustion ion chromatography.

Recent studies have shown that various semi- and non-volatile organohalogen compounds are ubiquitous in the environment: these include halogenated dioxins including chlorinated dioxins, other persistent organic pollutants (POPs), brominated flame retardants (BFRs), and perfluorooctane sulfonate (PFOS). However, monitoring and assessment of these compounds by the analyses of individual compounds and their isomers is onerous because of their low environmental concentrations and large number of compounds. In this study, we have developed a new method that is capable of screening and monitoring an array of organohalogen compounds efficiently by combustion ion chromatography (CIC) - the new analyzer that serially connects combustion furnace and ion chromatograph. Analyzer performance was evaluated in terms of its applicability, reproducibility, and sensitivity as limit of detection (LOD). Recoveries of organochlorine, organobromine, and organoiodine compounds by the CIC were between 97 and 105%; those of organofluorine compounds were from 86 to 91%. In all cases, the relative standard deviation of five analyses was 4% or smaller. The analyzer would exhibit good sensitivity for various environmental matrices (e.g., 2.8-31ng-X/g-soil, 1.4-16ng-X/L-water, and 9.2-100ng-X/m3N-gas). The method is fast and can provide information regarding the occurrence of organohalogen compounds within 1 or 2 days after sampling. Applicability of the new method for the assessment of contamination in flue gas and fly ash was also demonstrated. Our results show that the method is efficient to investigate emission sources and areas contaminated by organohalogen compounds.

Chromatography↗
PubMed2001

Metallic behavior and periodical valence ordering in a MMX chain compound, Pt(2)(EtCS(2))(4)I.

A new one-dimensional (1-D) halogen-bridged mixed-valence diplatinum(II,III) compound, Pt(2)(EtCS(2))(4)I (3), has been successfully synthesized from [Pt(2)(EtCS(2))(4)] (1) and [Pt(2)(EtCS(2))(4)I(2)] (2). These three compounds have been examined using UV-visible-near-IR, IR, polarized Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray crystal structure analyses (except for 1). Compound 3 was further characterized through electrical transport measurements, determination of the temperature dependence of lattice parameters, X-ray diffuse scattering, and SQUID magnetometry. 3 crystallizes in the monoclinic space group C2/c and exhibits a crystal structure consisting of neutral 1-D chains with a repeating -Pt-Pt-I- unit lying on the crystallographic 2-fold axis parallel to the b axis. The Pt-Pt distance at 293 K is 2.684 (1) A in the dinuclear unit, while the Pt-I distances are essentially equal (2.982 (1) and 2.978 (1) A). 3 shows relatively high electrical conductivity (5-30 S cm(-1)) at room temperature and undergoes a metal-semiconductor transition at T(M-S) = 205 K. The XPS spectrum in the metallic state reveals a Pt(2+) and Pt(3+) mixed-valence state on the time scale of XPS spectroscopy ( approximately 10(-17) s). In accordance with the metal-semiconductor transition, anomalies are observed in the temperature dependence of the crystal structure, lattice parameters, X-ray diffuse scattering, and polarized Raman spectra near T(M-S). In variable-temperature crystal structure analyses, a sudden and drastic increase in the Pt-I distance near the transition temperature is observed. Furthermore, a steep increase in U(22) of iodine atoms in the 1-D chain direction has been observed. The lattice parameters exhibit significant temperature dependence with drastic change in slope at about 205-240 K. This was especially evident in the unit cell parameter b (1-D chain direction) as it was found to lengthen rapidly with increasing temperature. X-ray diffraction photographs taken utilizing the fixed-film and fixed-crystal method for the metallic state revealed the presence of diffuse scattering with line shapes parallel to the a* axis indexed as (-, n + 0.5, l) (n; integer). Diffuse scattering with k = n + 0.5 is considered to originate from the 2-fold periodical ordering corresponding to -Pt(2+)-Pt(2+)-I-Pt(3+)-Pt(3+)-I- or -Pt(2+)-Pt(3+)-I-Pt(3+)-Pt(2+)-I- in an extremely short time scale. Diffuse lines corresponding to 2-D ordering progressively decrease in intensity below 252 K and are converted to the diffuse planes corresponding to 1-D ordering near T(M-S). Furthermore, diffuse planes condensed into superlattice reflections below T(M-S). Polarized Raman spectra show temperature dependence through a drastic low-energy shift of the Pt-I stretching mode and also through broadening of bands above T(M-S).

Journal Article↗
PubMed1981

Structure--activity relationship in cinnamamides. 3. Synthesis and anticonvulsant activity evaluation of some derivatives of (E)- and (Z)-m-(trifluoromethyl)cinnamamide.

The (E)- and (Z)-m-(trifluoromethyl)-alpha, beta-dimethylcinnamamides and some of their N-alkyl derivatives were prepared and pharmacologically tested as anticonvulsant agents in order to verify if a ring substituent, like the m-CF3 group, different from a halogen but possessing the same electronic effect could lead to equally active compounds. Some (E)-m-(trifluoromethyl)-alpha-methyl- and -non-methyl-substituted-cinnamamides were also prepared and tested. In the alpha, beta-dimethyl series the results show that the m-CF3 group leads to products more active than the ones unsubstituted on the phenyl ring but still less active than the p-halogen-substituted compounds previously studied. In the alpha-methyl and non-methyl-substituted series, the trend shows the m-CF3 group being able to produce less toxic and, in some cases, more active products than the previously studied amides.

Animals↗
PubMed2000

Bronchodilation and structure-activity relationship studies on new 6-substituted benzimidazo[1,2-c]quinazolines.

Two series of 6-substituted benzimidazo[1,2-c]quinazolines (Ia-p and IIa-l) have been synthesized and characterized. The compounds were evaluated for their bronchodilator activity, in vitro and in vivo. All the test compounds exhibited good activity both in vivo and in vitro methods. The structure-activity relationships based on the results obtained for these series have also been studied. In the 6-alkyl substituted compounds II, a longer alkyl chain and a 4-substitution by an electron-withdrawing group in compounds I, showed more activity. The presence of halogens altered the biological activity in both series. Among the compounds tested, 10-iodo-6-(n-propyl)-benzimidazol[1,2-c]quinazoline (II) was found to be the most potent (% protection = 75%; relative activity = 1.1).

Alkylation↗
PubMed2002

Halogenated indole-3-acetic acids as oxidatively activated prodrugs with potential for targeted cancer therapy.

Substituted indole-3-acetic acid (IAA) derivatives, plant auxins with potential for use as prodrugs in enzyme-prodrug directed cancer therapies, were oxidised with horseradish peroxidase (HRP) and toxicity against V79 Chinese hamster lung fibroblasts was determined. Rate constants for oxidation by HRP compound I were also measured. Halogenated IAAs were found to be the most cytotoxic, with typical surviving fractions of <10(-3) after incubation for 2h with 100 microM prodrug and HRP.

Animals↗
PubMed2005

Removal of bulk dissolved organic carbon (DOC) and trace organic compounds by bank filtration and artificial recharge.

Bank filtration and artificial recharge provide an important drinking water source to the city of Berlin. Due to the practice of water recycling through a semi-closed urban water cycle, the introduction of effluent organic matter (EfOM) and persistent trace organic pollutants in the drinking water is of potential concern. In the work reported herein, the research objectives are to study the removal of bulk and trace organics at bank filtration and artificial recharge sites and to assess important factors of influence for the Berlin area. The monthly analytical program is comprised of dissolved organic carbon (DOC), UV absorbance (UVA254), liquid chromatography with organic carbon detection (LC-OCD), differentiated adsorbable organic halogens (AOX) and single organic compound analysis of a few model compounds. More than 1 year of monitoring was conducted on observation wells located along the flowpaths of the infiltrating water at two field sites that have different characteristics regarding redox conditions, travel time, and travel distance. Two transects are highlighted: one associated with a bank filtration site dominated by anoxic/anaerobic conditions with a travel time of up to 4-5 months, and another with an artificial recharge site dominated by aerobic conditions with a travel time of up to 50 days. It was found that redox conditions and travel time significantly influence the DOC degradation kinetics and the efficiency of AOX and trace compound removal.

Berlin↗
PubMed1975

New aromatic diamidines with central alpha-oxyalkane or alpha, omega-dioxyalkane chains. Structure-activity relationships for the inhibition of trypsin, pancreatic kallikrein, and thrombin and for the inhibition of the overall coagulation process.

A series of omega-amidinophenylalkyl amidinophenyl ethers was synthesized and examined for inhibitory activity against trypsin, pancreatic kallikrein, and thrombin. Modifications of the compounds included lengthening of the alkane chain, variation in the position of the amidino groups, and substitution of halogen on the benzene rings. The compounds act as competitive reversible inhibitors, and many of them possess considerable potency. An outstanding trypsin inhibitor was found in 4-amidinophenylethyl 4 amidino-2-bromophenyl ether (compound 7) with a Ki value of 7.3 x 10(-8) M (pH 8.1, 37 degrees). A number of aromatic diamidines with a central dioxyalkane chain were similarly studied. Here, 1-(4-amidino-2-iodophenoxy)-5-(3-amidinophenoxy)pentane (compound 32) was a highly effective inhibitor of bovine thrombin (Ki = 1.1 x 10(-6) M), of human thrombin, and of the overall clotting process of human plasma.

Amidines↗
PubMed2005

Analysis of dichloroacetic acid in rat blood and tissues by hydrophilic interaction liquid chromatography with tandem mass spectrometry.

Dichloroacetic acid (DCA) is a compound found in chlorinated drinking water. In addition, the compound is a metabolite of several halogenated solvents, including trichloroethylene (TCE) and perchloroethylene (PCE). Exposure to DCA is of concern because high doses of the compound have been shown to cause cancer in laboratory animals. Dosages of TCE administered to animals in cancer studies are designed to elicit maximal DCA formation in vivo, whereas levels of DCA to which individuals are exposed in drinking water are very low. Analysis of DCA in biological samples has been quite challenging. Derivatizing reagents commonly used to convert DCA into a more volatile form for analysis by gas chromatography (GC) have been found to convert trichloroacetic acid (TCA), a major metabolite of TCE and PCE, into DCA. High-performance liquid chromatography (HPLC) analysis does not require derivatization of DCA and can thus avoid this problem. However, the most popular stationary phases in HPLC columns do not retain small, polar compounds such as DCA well. The liquid chromatography/tandem mass spectrometry (LC/MS/MS) method described in this paper uses hydrophilic interaction liquid chromatography (HILIC), a type of chromatography that is able to retain these small, polar compounds. Method validation was performed using the United States Food and Drug Administration (USFDA) and International Conference on Harmonziation (ICH) Guidance for Industry: Bioanalytical Method Validation as a guide. Levels of DCA found in rats dosed with 2 g/kg TCE were 17.2 ng/mL (liver), 262.4 ng/mL (kidney), 175.1 ng/mL (lung), and 39.5 ng/mL (blood).

Animals↗
PubMed1998

Characterization of the maleylacetate reductase MacA of Rhodococcus opacus 1CP and evidence for the presence of an isofunctional enzyme.

Maleylacetate reductases (EC 1.3.1.32) have been shown to contribute not only to the bacterial catabolism of some usual aromatic compounds like quinol or resorcinol but also to the degradation of aromatic compounds carrying unusual substituents, such as halogen atoms or nitro groups. Genes coding for maleylacetate reductases so far have been analyzed mainly in chloroaromatic compound-utilizing proteobacteria, in which they were found to belong to specialized gene clusters for the turnover of chlorocatechols or 5-chlorohydroxyquinol. We have now cloned the gene macA, which codes for one of apparently (at least) two maleylacetate reductases in the gram-positive, chlorophenol-degrading strain Rhodococcus opacus 1CP. Sequencing of macA showed the gene product to be relatively distantly related to its proteobacterial counterparts (ca. 42 to 44% identical positions). Nevertheless, like the known enzymes from proteobacteria, the cloned Rhodococcus maleylacetate reductase was able to convert 2-chloromaleylacetate, an intermediate in the degradation of dichloroaromatic compounds, relatively fast and with reductive dehalogenation to maleylacetate. Among the genes ca. 3 kb up- and downstream of macA, none was found to code for an intradiol dioxygenase, a cycloisomerase, or a dienelactone hydrolase. Instead, the only gene which is likely to be cotranscribed with macA encodes a protein of the short-chain dehydrogenase/reductase family. Thus, the R. opacus maleylacetate reductase gene macA clearly is not part of a specialized chlorocatechol gene cluster.

Amino Acid Sequence↗
PubMed1987

Stability of I-653 in soda lime.

Stability is an important characteristic of a halogenated volatile anesthetic because breakdown may produce toxic compounds. The resistance to breakdown by soda lime of a new halogenated volatile anesthetic, I-653, was compared with the resistances found for halothane, isoflurane, and sevoflurane. The four anesthetics were injected concurrently into flasks containing 500 ml of gas and 100 g of soda lime maintained at 40, 60, and 80 degrees C. Four or five flasks were tested at each temperature. The rate of anesthetic degradation increased as temperature increased. Degradation was greatest with sevoflurane and least with I-653. At 80 degrees C, the rate of degradation per hr was 92.2 +/- 5% with sevoflurane; 16.0 +/- 1.6% with halothane; 13.1 +/- 3.7% with isoflurane; and 0.44 +/- 0.26% with I-653 (means +/- SD). The in vitro stability of I-653 suggests that it may strongly resist biodegradation.

Anesthesia, Inhalation↗
PubMed2002

Halo-enediynes: probing the electronic and stereoelectronic contributions to the Bergman cycloaromatization.

A series of halogen-substituted cyclic enediynes were prepared with use of carbenoid coupling strategy. DFT analysis, initially used to identify synthesis candidates, was also employed to rationalize the propensity for cycloaromatization of the compounds. In all cases studied the halogen atom had a strongly retardative effect on the thermal Bergman cycloaromatization reaction. The isolation of the first C-9 monochloroenediyne is noteworthy, and may find application in prodrug design.

Alkynes↗
PubMed2005

Mutant-selective thyromimetics for the chemical rescue of thyroid hormone receptor mutants associated with resistance to thyroid hormone.

The thyroid hormone receptors (TRs) are ligand-dependent transcription factors that control the expression of multiple genes involved in development and homeostasis in response to thyroid hormone (triiodothyronine, T3). Mutations to TRbeta that reduce or abolish ligand-dependent transactivation function are associated with resistance to thyroid hormone (RTH), an autosomal dominant human genetic disease. A series of neutral alcohol-based compounds, based on the halogen-free thyromimetic GC-1, have been designed, synthesized, and evaluated in cell-based assays for their ability to selectively rescue three of the most common RTH-associated mutations (i.e., Arg320 --> Cys, Arg320 --> His, and Arg316 --> His) that affect the basic carboxylate-binding arginine cluster of TRbeta. Several analogues show improved potency and activity in the mutant receptors relative to the parent compound GC-1. Most significantly, two of these mutant-complementing thyromimics show high potency and activity with a strong preference for the mutant receptors over wild-type TRalpha(wt), that is associated with the cardiotoxic actions of T3. The compounds were evaluated in reporter gene assays using the four common thyroid hormone response elements, DR4, PAL, F2 (LAP), and TSH, and show activities and selectivites consistent with their unique potential as agents to selectively rescue thyroid function to these RTH-associated mutants.

Acetates↗
PubMed2006

Substituted 2-phenyl-benzimidazole derivatives: novel compounds that suppress key markers of allergy.

The pharmacotherapy of allergy and asthma has traditionally focused on the effecter molecules of the allergic cascade, while neglecting targets that play an early role in their development. Reasoning that IgE is central to the expansion of atopic diseases, we identified and extended a novel family of 2-(substituted phenyl)-benzimidazole inhibitors of IgE response. Pharmacological activity depends on an intact phenylbenzimidazole-bis-amide backbone, and is optimized by the presence of lipophilic terminal groups composed of either bis cycloalkyl or combinations of aliphatic and halogen-substituted aromatic groups. These compounds also inhibit IL-4 and IL-5 responses in T cells and CD23 expression on B cells, with potencies that parallel their inhibition of IgE. The broad profile of these compounds thus underscores their potential for treating the multifarious pathology of asthma.

Administration, Oral↗
PubMed2001

Microbial biosynthesis of halometabolites.

Halometabolites are compounds that are commonly found in nature and they are produced by many different organisms. Whereas bromometabolites can mainly be found in the marine environment, chlorometabolites are predominately produced by terrestrial organisms; iodo- and fluorocompounds are only produced infrequently. The halogen atoms are incorporated into organic compounds by enzyme-catalyzed reactions with halide ions as the halogen source. For over 40 years haloperoxidases were thought to be responsible for the incorporation of halogen atoms into organic molecules. However, haloperoxidases lack substrate specificity and regioselectivity, and the connection of haloperoxidases with the in vivo formation of halometabolites has never been demonstrated. Recently, molecular genetic investigations showed that, at least in bacteria, a different class of halogenases is involved in halometabolite formation. These halogenases were found to require FADH2, which can be produced from FAD and NADH by unspecific flavin reductases. In addition to FADH2, oxygen and halide ions (chloride and bromide) are necessary for the halogenation reaction. The FADH2-dependent halogenases show substrate specificity and regioselectivity, and their genes have been detected in many halometabolite-producing bacteria, suggesting that this type of halogenating enzymes constitutes the major source for halometabolite formation in bacteria and possibly also in other organisms.

Anti-Bacterial Agents↗
PubMed2001

Response mechanisms of thermionic detectors with enhanced nitrogen selectivity.

The response mechanisms of a thermionic detector with enhanced nitrogen selectivity operating in an inert gas environment were investigated. According to accepted theory, the analyte has to contain electronegative functional groups in order for negative ions to be formed by the extraction of electrons from the thermionic source. This leads to a selective detector response for compounds containing nitro groups or multiple halogens. However, in the tests described here, polycyclic aromatic nitrogen hydrocarbons (PANHs), acridines, and carbazoles were used as reference substances. These compounds contain no electronegative functional groups. None of the investigated acridines exhibited any response from the detector, but carbazoles generated a strong structure-related detector response. By examining partial charges for all hydrogens of all individual carbazoles and acridine, it was demonstrated that the acidic hydrogen atom attached to the nitrogen heteroatom of the carbazoles has a strong influence on the detector response. Ionization of carbazoles may occur by dissociation of the nitrogen-hydrogen bond during contact with the thermionic surface. Support for this theory was provided by the linear relationship between the relative detector response and the deprotonization energy of the carbazoles (coefficients of determination of 0.90 and 0.98 for linear and quadratic models, respectively, were obtained). Further, there appeared to be no linear relationship between the detector response and electron affinity of the carbazoles, (R2 value, 0.32). Thus, the mechanism involved in ionization of the carbazoles is probably not direct electron transfer from the thermionic surface to the carbazoles. Principal component analysis (PCA) showed that the thermal conductivity of chemically inert detector gases also has an influence on the detector response. The investigated gases were helium, neon, nitrogen, carbon dioxide, and argon. It was found that thermal conductivity can be used to rank the detector response for the carbazoles, and there was no discernible response when helium, which has the highest thermal conductivity, was used as the detector gas.

Journal Article↗
PubMed2005

The taming of capsaicin. Reversal of the vanilloid activity of N-acylvanillamines by aromatic iodination.

Aromatic iodination ortho to the phenolic hydroxyl reverts the activity of the ultrapotent vanilloid agonist resiniferatoxin (RTX, 1a), generating the ultrapotent antagonist 5'-iodoRTX (1b). To better understand the role of iodine in this remarkable switch of activity, a systematic investigation on the halogenation of vanillamides, a class of compounds structurally simpler than resiniferonoids, was carried out. The results showed that (a) the antagonistic activity depends on the site of halogenation and is maximal at C-6', (b) iodine is more efficient than chlorine and bromine at reverting the agonistic activity, and (c) iodine-carbon exchange decreases antagonist activity. Iodine-induced reversal of vanilloid activity was also observed in vanillamides more powerful than capsaicin, but a poor correlation was found between agonistic and antagonistic potencies, suggesting that differences exist in the way vanillamides and their 6'-iodo derivatives bind to TRPV1.' '

Bromine↗