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PubMed1990

[Pollution of indoor air in large-scale kitchens and laundries by volatile halogenated hydrocarbons].

The study demonstrates that the agents used for dishwashing and in the central laundry are already slightly contamined with halogenated hydrocarbons and formaldehyde. Analyses of the washing lyes yield considerably higher concentrations of halogenated hydrocarbons. Especially in the dishwater a relatively high concentration of trichloromethane (chloroform) was detected. Obviously these halogenated hydrocarbons are also present in relatively high concentrations in the air of the corresponding working places. However, the concentrations of individual halogenated hydrocarbons and formaldehyde are clearly below the respective threshold limit values.

Air Pollutants, Occupational↗

PubMed2001

Halogen bonding: a paradigm in supramolecular chemistry.

The term halogen bonding describes the tendency of halogen atoms to interact with lone pair possessing atoms. The binding features and structural properties of halogen bonding are discussed and applied to drive the intermolecular self-assembly of hydrocarbons and perfluorocarbons in chemo-, site-, and enantioselective supramolecular synthesis. The halogen bonding is thus an effective and reliable tool in crystal engineering at the disposal of the supramolecular chemist.

Journal Article↗

PubMed2007

Bond orders and atomic properties of the highly deformed halogenated fullerenes C60F18 and C60Cl30 derived from their charge densities.

The experimental charge densities of the halogenated C(60) fullerenes C(60)F(18) and C(60)Cl(30) were determined from high-resolution X-ray data sets measured with conventional Mo(Kalpha) radiation at 20 K for C(60)Cl(30) and with synchrotron radiation at 92 K for the fluorine compound. Bond topological and atomic properties were analyzed by using Bader's AIM theory. For the different C--C bonds, which vary in lengths between 1.35 and 1.70 A bond orders n between n=2 and significantly below n=1 were calculated from the bond topological properties at the bond critical points (BCP's). The low bond orders are seen for 5/6 bonds with each contributing carbon carrying a halogen atom. By integration over Bader's zero flux basins in the electron density gradient vector field atomic properties were also obtained. In contrast to free C(60), in which all carbon atoms have a uniform volume of 11 A(3) and zero charge, atomic volumes vary roughly between 5 and 10 A(3) in the halogenated compounds. Almost zero atomic charges are also found in the Cl derivative but a charge separation up to +/-0.8 e exists between C and F in C(60)F(18) due to the higher fluorine electronegativity, which is also seen in the electrostatic potential for which the electronegativity difference between carbon and fluorine, and the addition to one hemisphere of the fullerene cage leads to a strong potential gradient along the C(60)F(18) molecule. From the summation over all atomic volumes it follows that the halogen addition does not only lead to a dramatic distortion of the C(60) cage but also to a significant shrinkage of its volume.

Journal Article↗

PubMed2002

Knoop hardness depth profiles and compressive strength of selected dental composites polymerized with halogen and LED light curing technologies.

After the first light-emitting diode (LED) light curing units (LCUs) became available commercially, a comparison of mechanical properties between materials polymerized with conventional halogen lamps and this new technology was required. This study, therefore, investigated the curing performance of two conventional commercial halogen LCUs (Translux CL, Spectrum800), a custom-made LED LCU prototype, and one of the first commercially available LED LCUs (LUXoMAX). The Spectrum800 was adjusted to a similar irradiance to the custom-made LED LCU prototype. Both technologies were compared by measuring compressive strength and Knoop hardness depth profiles for selected dental composites polymerized for 20 or 40 s. Four dental composites (Z100, Spectrum TPH, Solitaire2, and Definite) were used. Two of these composites (Solitaire2 and Definite) contain co-initiators in addition to the standard photoinitiator camphorquinone. In general, the material hardness obtained with the LUXoMAX was statistically significantly (p < 0.05) lower at the depths of 0.1, 1.0, 1.9, and 3.1 mm, for all composites and curing times, than for the other three LCUs. The LED LCU prototype achieved, with one exception, up to a depth of 1.9 mm a material hardness for the composites Z100, Spectrum TPH and Solitaire2 that was not statistically significant different (p < 0.05) from the hardness obtained with the halogen LCUs. At a greater depth (3.1 mm), however, the LED LCU prototype showed statistically significantly lower hardness values than the halogen units. The compressive strength test showed at a 95% confidence level that similar compressive strengths were achieved with the LCUs LUXoMAX and Spectrum800, and the Translux and LED LCU prototype.

Composite Resins↗

PubMed2004

Extension of the PDDG/PM3 and PDDG/MNDO semiempirical molecular orbital methods to the halogens.

The new semiempirical methods, PDDG/PM3 and PDDG/MNDO, have been parameterized for halogens. For comparison, the original MNDO and PM3 were also reoptimized for the halogens using the same training set; these modified methods are referred to as MNDO' and PM3'. For 442 halogen-containing molecules, the smallest mean absolute error (MAE) in heats of formation is obtained with PDDG/PM3 (5.6 kcal/mol), followed by PM3' (6.1 kcal/mol), PDDG/MNDO (6.6 kcal/mol), PM3 (8.1 kcal/mol), MNDO' (8.5 kcal/mol), AM1 (11.1 kcal/mol), and MNDO (14.0 kcal/mol). For normal-valent halogen-containing molecules, the PDDG methods also provide improved heats of formation over MNDO/d. Hypervalent compounds were not included in the training set and improvements over the standard NDDO methods with sp basis sets were not obtained. For small haloalkanes, the PDDG methods yield more accurate heats of formation than are obtained from density functional theory (DFT) with the B3LYP and B3PW91 functionals using large basis sets. PDDG/PM3 and PM3' also give improved binding energies over the standard NDDO methods for complexes involving halide anions, and they are competitive with B3LYP/6-311++G(d,p) results including thermal corrections. Among the semiempirical methods studied, PDDG/PM3 also generates the best agreement with high-level ab initio G2 and CCSD(T) intrinsic activation energies for S(N)2 reactions involving methyl halides and halide anions. Finally, the MAEs in ionization potentials, dipole moments, and molecular geometries show that the parameter sets for the PDDG and reoptimized NDDO methods reduce the MAEs in heats of formation without compromising the other important QM observables.

Journal Article↗

PubMed1981

Synthesis of dehydroepiandrosterone sulfatide and 16 alpha-halogenated steroids.

Dehydroepiandrosterone sulfatide was prepared in a 68% yield by the reaction of 5-androstene-3 beta-ol-17-one 3 sulfate (silver salt) with dipalmitoyl alpha-iodopropylene glycol. The sulfatide was found to be a more potent inhibitor of human glucose-6-phosphate dehydrogenase than dehydroepiandrosterone. 16 alpha-Halogenated steroids also were prepared by direct halogenation of the steroid or indirect halogenation of an appropriate steroidal intermediate. Among various halogenated steroids, 16 alpha-bromoepiandrosterone was 50 times as potent as dehydroepiandrosterone as an inhibitor of glucose-6-phosphate dehydrogenase.

Animals↗

PubMed2003

Cytotoxicity and oxidative stress caused by dental adhesive systems cured with halogen and LED lights.

The aim of the present study was to investigate the cytotoxicity of two "one bottle" adhesive systems after polymerization with a conventional halogen or a light emitting diode (LED) lamp. We hypothesized that different polymerization sources might enhance the intracellular production of reactive oxygen species (ROS), leading to reduced cell survival. Two "one bottle" adhesive systems (Optibond Solo and Scotchbond One) were cured with a commercial halogen (Optilux 500) and an LED source (Elipar Freelight, 3 M). The specimens were extracted for 24 h in complete cell culture medium or in phosphate-buffered saline (PBS). Endothelial cells (ECV 304) were exposed to the extracts for 24 h and survival rates were evaluated by the MTT assay. Then, ROS generation was monitored by the oxidation-sensitive fluorescent probe 2'7'-dichlorofluorescin diacetate (DCFH-DA). Extracts from all materials except for Optibond Solo polymerized with the halogen lamp were rated significantly cytotoxic. Scotchbond One cured with LED was the most toxic material, which reduced cell survival to about 23% compared with control cultures. Significantly higher amounts of ROS were produced in cell cultures treated with adhesives polymerized with the LED lamp compared with the materials cured with the commercial halogen light source. We demonstrated that the production of intracellular ROS by extracts of the adhesive systems depended on the light sources used for curing of the materials. These results suggested a possible link between ROS production and cytotoxic activity.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1983

In vitro studies of the adrenal metabolism of halogenated side-chain analogues of cholesterol.

The cholesterol side-chain cleavage enzyme system of rat adrenal mitochondria and rat adrenocortical carcinoma cells was found to metabolize three halogenated side-chain cholesterol analogues to pregnenolone. The analogues were 26-bromocholesterol, 26-nor-25(RS)-bromocholesterol and 26-iodocholesterol. The addition of Ca2+ to rat adrenal mitochondria did not produce an increase in the rate of metabolism of the halogenated sterol to pregnenolone. The brominated sterols suppressed the de novo sterol biosynthesis of rat adrenocortical carcinoma cells. The experimental findings are supportive of the notion that a halogen atom at such a position in a sterol is analogous to a hydroxyl group but unlike a proton. ACTH, therefore, may not be a requirement for the uptake and utilization of such sterols. The halogenated sterols may have a use as probes in the study of sterol transfer into and within cells.

Adrenal Cortex Neoplasms↗

PubMed1976

The binding of lac repressor and the catabolite gene activator protein to halogen-substituted analogues of poly[d(A-T)].

We have measured the binding of two regulatory proteins to the complete halogen-substituted series of poly[d(A-T)] analogues. Both the lac repressor and the catabolite gene activator protein were found to bind more strongly to all of the halogen-substituted DNAs than they do to poly[d(A-T)]. For both proteins, the order of binding preference is poly[d(A-ioU)] is greater than poly[d(A-brU)] is greater than or equal to poly[d(A-clU)] is greater than poly[d(A-flU)] is greater than poly[d(A-T)]. Quantitative data on the binding of these proteins to poly[d(A-U)] is also given. The significance of these results for the mechanism of protein-DNA interaction is discussed. This is the first report that an activator protein binds more strongly to a halogen-substituted DNA; we discuss this result with regard to the mechanism of action of bromodeoxyruidine and other halogen-substituted base analogues on the inhibition and induction of differentiation in eucaryotic cells.

Bacterial Proteins↗

PubMed1978

Sites of direct and indirect halogenation of albumin.

The sites of radiohalogenation in proteins vary with the labeling method and the pH of the labeling reaciton. We have directly halogenated albumin with carrier-free radioiodide by three methods (pH range 2.2--9.3), and with carrier-free radiobromide by the chloroperoxidase method (pH range 2.2--4.6). Albumin was also indirectly halogenated by attaching a radioiodinated acylating agent, N-succinimidyl-3-(4-hydroxyphenyl) propionate (SHPP). The labeled proteins were proteolyzed enzymatically at neutral pH and the labeled amino acids produced were analyzed by liquid chromatography. Iodination at pH 7 yielded predominantly monoiodotyrosine, but at lower pH, fewer tyrosyl residues are labeled and a greater number of unstable sulfur-iodine bonds are formed at cysteinyl residues. Bromination with chloroperoxidase resulted in a high degree of labeling of cysteinyl residues at pH 2.8, the condition for optimum activity of this halogenating enzyme. Indirect halogenation with SHPP resulted in labeling of mid-chain lysyl, histidyl and tyrosyl residues.

Bromine↗

PubMed1985

5'-Deoxy-5'-methylthioadenosine phosphorylase--III. Role of the enzyme in the metabolism and action of 5'-halogenated adenosine analogs.

5'-Deoxy-5'-halogenated adenosines are alternative substrates for 5'-deoxy-5'-methylthioadenosine phosphorylase (MTAPase), an enzyme responsible for the metabolism of 5'-deoxy-5'-methylthioadenosine (MTA), a by-product of polyamine biosynthesis. The relative reactivity of these nucleosides with MTAPase from HL-60 human promyelocytic leukemia cells is MTA greater than 5'-deoxy-5'-fluoroadenosine (5'-FlAdo) greater than 5'-chloro-5'-deoxyadenosine (5'-ClAdo) greter than 5'-bromo-5'-deoxyadenosine (5'-BrAdo) greater than 5'-deoxy-5'-iodoadenosine (5'-IAdo). In MTAPase-containing cells, the adenine released from the 5'-halogenated adenosine was incorporated into adenine nucleotide pools; cleavage by (MTAPase appeared to be the rate-limiting step in this process. 5'-BrAdo and 5'-IAdo were growth inhibitors (EC50 values less than 10 microM) of MTAPase-containing cell lines (HL-60 human promyelocytic leukemia and the L5178Y murine lymphoblastic leukemia) but were much less active (EC50 values greater than 65 microM) against MTAPase-deficient cell lines (the CCRF-CEM human T cell leukemia and the L1210 murine leukemia). The full cytotoxicity of these compounds, therefore, appeared to be related to their phosphorolysis by MTAPase. Indirect evidence suggests that 5-halogenated ribose-1-phosphate derivatives of 5'-BrAdo or 5'-IAdo produced by the MTAPase reaction were the active metabolites of these 5'-halogenated adenosines.

Adenine Nucleotides↗

PubMed1996

Accumulation of extractable organic halogens (EOX) by the freshwater mussel, Anodonta cygnea L., exposed to chlorine bleached pulp and paper mill effluents.

Freshwater mussels, Anodonta cygnea L., were collected in a lowly polluted area in north-eastern France, and exposed during 28 days at three sites up and downstream of a chlorine bleached pulp and paper mill effluent Water, sediment and mussel samples were collected at regular intervals and analyzed for halogenated organic residues using the sum parameters AOX (Adsorbable Organic Halogen) and EOX (Extractable Organic Halogen). The survey of the water showed a chronic contamination by organic halogens of the water and the sediment downstream of the pulp and paper mill sewer. Mussels exposed upstream of the mill showed no significant variation of their EOX tissue concentration. In contrast, progressive accumulation of EOX occurred with the exposure time in mussels exposed downstream of the mill. No steady state of the EOX concentration was observed after four weeks of exposure.

Animals↗

PubMed1987

Developmental toxicity of halogenated acetonitriles: drinking water by-products of chlorine disinfection.

The developmental toxicity of acetonitrile and 5 halogenated derivatives was examined with an in vivo teratology screen adapted for use in the Long-Evans rat. The screen was extended to an evaluation of growth till postnatal Days 41-42, and weight of several organs at sacrifice. Acetonitrile was without developmental effects even at doses toxic to the dam. Of the halogenated compounds, treatment with trichloroacetonitrile (TCAN) and dichloroacetonitrile (DCAN) resulted in reduced fertility and increased early implantation failure. There was no effect on litter size in females bearing live litters, but pup birth weight was reduced in all litters exposed to halogenated compounds. Perinatal survival of the pups was adversely impacted by DCAN and TCAN. Postnatal growth till Day 4 was reduced by DCAN and bromochloroacetonitrile (BCAN) while growth till Day 42 was consistently affected only by TCAN. Some general observations were made on the usefulness of the criteria used in the screen, and TCAN, the most toxic of the halogenated compounds, was selected for further in-depth evaluation.

Abnormalities, Drug-Induced↗

PubMed2004

Plasma arc versus halogen light curing of orthodontic brackets: a 12-month clinical study of bond failures.

The purpose of this randomized clinical trial was to evaluate the clinical performance of brackets cured with 2 different light-curing units (conventional halogen light and plasma arc light); 83 patients treated with fixed appliances were included in the study. With the "split-mouth" design, each patient's mouth was divided into 4 quadrants. In 42 randomly selected patients, the maxillary left and mandibular right quadrants were cured with the halogen light, and the remaining quadrants were cured with the plasma arc light. In the other 41 patients, the quadrants were inverted. A total of 1434 stainless steel brackets were examined: 717 were cured with a conventional halogen light for 20 seconds; the remaining 717 were cured with the plasma arc light for 5 seconds. The number, cause, and date of bracket failures were recorded for each light-curing unit over 12 months. Statistical analysis was performed with the Fisher exact test, the Kaplan-Meier survival estimates, and the log-rank test. No statistically significant differences were found between the total bond failure rates of the brackets cured with the halogen light and those cured with the plasma arc light. Neither were significant differences found when the clinical performances of the maxillary versus mandibular arches or the anterior versus posterior segments were compared. These findings demonstrate that plasma arc lights are an advantageous alternative to conventional light curing, because they significantly reduce the curing time of orthodontic brackets without affecting the bond failure rate.

Acid Etching, Dental↗

PubMed2003

Photoinitiator dependent composite depth of cure and Knoop hardness with halogen and LED light curing units.

Light curing units (LCUs) are used for the polymerization of dental composites. Recent trends in light curing technology include replacing the halogen LCUs with LCUs using light emitting diodes (LEDs) reducing curing times and varying the LCUs light output within a curing cycle. This study investigated the time dependence of the Knoop hardness and depth of cure of dental composites polymerized with a halogen LCU (Trilight) and two LED LCUs (the commercial Freelight and custom-made LED LCU prototype). The halogen LCU was used in the soft-start (exponential increase of output power) and standard mode. Four dental composites (Z100, Spectrum, Definite, Solitaire2) were selected, two of them (Definite, Solitaire2) contain co-initiators in addition to the standard photoinitiator camphorquinone. The depth of cure obtained with the Trilight in the standard mode was statistically significantly greater (p < 0.05) than that obtained with the LED LCUs for all materials and curing times. The custom made LED LCU prototype (LED63) achieved a statistically significantly greater depth of cure than the commercial LED LCU Freelight for all materials and curing times. There was no statistical difference in Knoop hardness at the 95% confidence level at the surface of the 2 mm thick sample between the LED63 or Trilight (standard mode) for the composite Z100 for all times, and for Spectrum for 20s and 40s curing time. The composites containing co-initiators showed statistically significantly smaller hardness values at the top and bottom of the samples if LED LCUs were used instead of halogen LCUs. The experiment revealed that the depth of cure test does not and the Knoop hardness test does discriminate between LCUs, used for the polymerization of composites containing photoinitiators in addition to camphorquinone.

Composite Resins↗

PubMed1997

Mutation induction and mutation frequency decline in halogen light-irradiated Escherichia coli K-12 AB1157 strains.

The effects of halogen light irradiation on reversion of argE3-->Arg+ in E. coli K12 strain AB1157 and its mfd- mutant, and on mutation frequency decline (MFD) after transiently incubating irradiated bacteria under non-growing conditions were studied. The induction of mutations, the mutational specificity, and the MFD effect had the same characteristic features as those seen in E. coli B strains after irradiation with 254 nm UV light. MFD which is due to repair of premutagenic lesion in the transcribed strand of glnU gene and prevents mutations leading to supB formation, was not observed in halogen light-induced mutations in the mfd-1 strain. Overproduction of UmuD'C proteins led to a large increase in mutation frequency, which was much greater in mfd- than in mfd+ strains. In bacteria irradiated with halogen light and incubated immediately in a rich medium to express mutations, the formation of supB predominated strongly over that of supE(ochre) in mfd- cells but was at a similar level in mfd+ cells. Introduction of zcf117::Tn10 to AB1157 strain makes cells more sensitive to halogen light irradiation, whereas introduction of mfd-1 does not.

Arginine↗

PubMedDate not supplied

QSAR modeling of oxidative stress in vitro following hepatocyte exposures to halogenated methanes.

Volatile halogenated aliphatic compounds are among those chemicals that can cause oxidative stress in vitro and in vivo. Relationships can be identified between the potential of these chemicals to elicit certain biological responses and their specific chemical descriptors, such as molecular orbital energies (LUMO) or partition coefficients (logP). A quantitative structure-activity relationship (QSAR) model has not been reported previously for the potential of a series of brominated and chlorinated methanes to induce oxidative stress in primary rat hepatocytes. By utilizing a novel in vitro methodology to expose cultures of rat primary hepatocytes to volatile chemicals, biological responses were assessed from exposures of hepatocytes to individual halogenated methanes. Indicators of lipid peroxidation, reactive oxygen species and cytotoxicity were measured. For the 10 brominated and chlorinated methanes tested, semi-empirical molecular orbital methods were used to calculate the physical/chemical descriptors used in the QSAR models. These models were used to explain the relative potential for a given halogenated methane to induce markers of oxidative stress or related damage in vitro. The results showed that certain descriptors, such as the molecular orbital energies, bond lengths, and lipophilicity are quantitatively correlated with induction of indicators for oxidative stress and cytotoxicity by halogenated methanes in primary rat hepatocytes.

Animal Testing Alternatives↗

PubMed2001

Simultaneous determination of halogenated derivatives of alkylphenol ethoxylates and their metabolites in sludges, river sediments, and surface, drinking, and wastewaters by liquid chromatography-mass spectrometry.

A quantitative solid-phase extraction-liquid chromatography/mass spectrometry (SPE-LC/MS) method is described for the simultaneous analysis of halogenated byproducts of alkylphenolic compounds and their degradation products formed during chlorine disinfection in the presence of bromide ions. Compounds analyzed include brominated and chlorinated nonylphenol ethoxylates (XN-PEOs); octylphenol ethoxylates (XOPEOs); nonylphenols (XNP); nonylphenoxycarboxylates (XNPECs) and their precursors nonionic surfactants, alkylphenol ethoxylates (APEOs); and their metabolites formed during sewage treatment, alkylphenoxycarboxylates (APECs) and alkylphenols (APs). Target compounds were concentrated from water samples using a C18 SPE procedure. Extracts were analyzed using reversed phase LC/MS. The performances of both atmospheric pressure chemical ionization (APCI) and electrospray (ESI) interfaces were compared. ESI offered better sensitivity and specificity for a higher range of oligomers. Detection limits (LODs) for water samples were from 20 to 100 ng/L; and for sediment samples, from 2 to 10 microg/kg. Slightly higher LODs were obtained for sludge samples (5-25 microg/kg). Halogenated byproducts were found in sludge from Barcelona drinking water treatment plant in concentrations of 220 microg/kg for BrNP, 430 microg/kg for BrNPEOs (nEO = 1 - 2), and 1600 microg/kg for BrNPEOs (nEO = 3 - 15). The concentration of ClNPEOs was estimated to be in the order of 660 microg/kg (assuming the same response as BrNPEOs). Halogenated OPEOs were also identified, and their concentration was approximately 50 times lower than the concentration of NPEOs analogues. To our knowledge, this is the first method described that allows simultaneous determination of alkyphenol ethoxylates and halogenated derivatives, including degradation products.

Chromatography, High Pressure Liquid↗