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Photolytic cleavage of sulfonamide bonds.

It has been found that the sulfonamide bond is relatively susceptible to photolytic cleavage. The breakdown was effected either by irradiation with a source having a continuous emission above the wavelengths of 1800 angstroms or by another source emitting principally at 2537 angstroms. Less destruction of the amino acids was seen with the latter relative to the sulfonamide bond cleavage. The cleavage was not effected by irradiation at wavelengths greater than about 3000 angstroms. Side reactions were noted involving decarboxylation, demination, and destruction of certain susceptible amino acids such as tryptophan. In only one case was a product found that arose from cleavage of a carboxamide bond; glycyltyrosine gave glycine and tyrosine upon irradiation. A yield of 75 percent of the corresponding amino acid has been obtained by irradiation of tosylhistidine; yields of 75 to 100 percent have been obtained from sulfamic acid (NH(2)SO(3)H). A qualitative method for identifying sulfonylated amino acids is described.

Arginine↗

Method for group determination of total N-nitroso compounds and nitrite in fresh gastric juice by chemical denitrosation and thermal energy analysis.

A method for the determination of total N-nitroso compounds (NOC) and nitrite in fresh human gastric juice is described, which is based on earlier methods. A freshly obtained gastric juice sample is injected directly into refluxing ethyl acetate containing glacial acetic acid, HCl and HBr to determine the total concentration (A) of nitrite, total NOC and thermo- and acid-labile thermal energy analyser (TEA)-responsive compounds (TAC). Another fresh sample of the same juice (with or without the addition of sulfamic acid) is injected directly into refluxing ethyl acetate containing glacial acetic acid and HCl for determining the TAC level (B) and the total level (C) of nitrite and TAC. The NO released from nitrite, TAC and NOC is detected by TEA acting as a chemiluminescence detector. The differences between A and C and between C and B represent the concentrations of total NOC and nitrite, respectively. The method is rapid, reproducible (relative standard deviation 1-6%) and sensitive (detection limit 1.0 pmol). The behaviour of nitrite and NOC in the analytical system was studied and relevant techniques for the direct analysis of fresh gastric juice samples and for stabilization of fresh samples have been developed.

Differential Thermal Analysis↗

Is the negative charge on RNHSO3-M+ an essential requirement for sulfamate sweetness?

Although many structure-taste studies have been carried out on sulfamate (cyclamate) sweeteners, there are still some unanswered questions-notably whether the sulfamate anion, -NHSO(3)(-), is essential for sweetness in this class of compounds. The literature is contradictory on this point; therefore, 14 sulfamate esters RNHSO(3)R', which contain the sulfamate moiety but without the negative charge, i.e., -NHSO(3)(-), have been synthesized and tasted under standard conditions. Almost all of the esters were found to possess strong sweetness accompanied by bitterness. Because the esters had to be heated in water to 60 degrees C to dissolve them, it was necessary to check for partial hydrolysis to the free sulfamic acids, RNHSO(3)H, since they would be sweet and would invalidate the tasting results if formed. This was done by monitoring (gas-liquid chromatography) the formation of alcohol after heating. Negligible or very low hydrolysis to acid was found for all 14 esters. This work, in addition to answering an important structure-taste question, points the way to the potential use of suitable sulfamate esters as additives in situations where the more usual sodium sulfamate salts are unsuitable, for example, in hydrophobic media.

Anions↗

Carbonic anhydrase inhibitors: inhibition of isozymes I, II and IV with N-hydroxysulfonamides--a novel class of intraocular pressure lowering agents.

A series of N-hydroxy sulfonamides has been prepared by reaction of alkyl-, arylalkyl- and arylsulfonyl halides or sulfonic acid anhydrides with hydroxylamine. Structurally related inhibitors were also obtained from acyl chlorides and hydroxylamine, as well as by reaction of tosyl isocyanate with hydroxylamine, sulfamic acid and sulfamide. Inhibition of three carbonic anhydrase (CA) isozymes, hCA I, hCA II and bCA IV (h = human; b = bovine) with the prepared compounds has been investigated. Good inhibitors, as well as compounds with moderate activity against these isozymes were detected, depending on the R group to which the SO2NHOH or CONHOH moieties were attached. Susceptibility to inhibition was generally: hCA II > bCA IV >> hCA I. Some of the new inhibitors showed very good antiglaucoma action when administered directly into the eye in experimental animals, acting as more efficient intraocular pressure lowering agents as compared to the clinical drug dorzolamide. This constitutes an encouraging result for obtaining novel antiglaucoma drugs from this class of CA inhibitors.

Acetamides↗

Cleaning procedures for small dental instruments prior to sterilization.

Observations were made in an institutional setting on the quality of cleaning of dental burs. Assessments were made by scanning electron microscopy of surface contamination and change to the surface quality of burs before and after use, and as a result of different cleaning procedures. The most significant finding was the corrosive action on carbon steel burs of a phosphoric acid based cleaning solution in routine use at the time. We show by comparison the effectiveness and non-corrosive nature of an alternative detergent based on sulfamic acid, and propose a suitable cleaning routine. Two other findings are presented: new burs as unpackaged are unacceptable for use without first being subjected to a cleaning process (we recommend a suitable procedure); and there is a need for distilled water rather than tap water rinsing after detergent use. It is an important part of an institution's responsibility to monitor cleaning, sterilizing and supply services; the scanning electron microscope is a valuable adjunct in this aspect of quality assurance.

Communicable Disease Control↗

Spectrophotometric detection of iodide and chromic (III) in urine after oxidation to iodine and chromate (VI).

Tests for oxidizing adulterants in urine are a continuing challenge to the drug-testing program. Iodine was found to destroy morphine and 6-acetylmorphine almost immediately. The effects were less evident on 11 -nor-delta9-tetrahydrocannabinol-9-carboxylic acid (THC-acid). When the urine solution was tested for iodine by a chromogenic substrate, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), no iodine was detected. Masking drug and adulterant simultaneously made iodine a preferred oxidizing adulterant for drug abusers. In this study, the reduced iodide was oxidized by sodium nitrite to iodine. The excess nitrite was decomposed by sulfamic acid and the iodine was detected by ABTS. Linearity was 12.7 to 635 mg/L (0.1 to 5 mmol/L, y = 0.9966x + 0.0016, R2 = 1.0000). Precisions (coefficient of variation) were within +/- 4.1% and quantitative accuracies were within 97% of expected values (n=5). Chromate, iodate, periodate, and persulfate interfered with the method. To alleviate the problem, the positive specimens were tested again by an iodine-specific method. After oxidation, the samples were treated with sodium azide and ammonium thiocyanate. In presence of thiocyanate, the azide reduced iodine to iodide almost immediately, and the solutions showed negative response to ABTS. The results were compared with that of a control group tested without thiocyanate. When iodine was present, the ratios of thiocyanate to control were less than 6%. Chromate was also found to destroy THC-acid in urine, and during storage most of the chromate changed to chromic (III). In this study, chromic was oxidized to chromate by hydrogen peroxide and sodium hydroxide and detected by 1,5-diphenylcarbazide. Linearity was 5.2 to 156 mg/L (0.1 to 3.0 mmol/L, y = 1.0285x - 0.0034, R2 = 0.9998). Precisions were within +/- 8.5% and quantitative accuracies were within 92% of expected values (n=5). The test was not interfered by other oxidizing agents. Both iodide and chromic oxidation methods showed urine backgrounds less than 1.27 and 0.52 mg/L, respectively (< 0.01 mmol/L). It indicated that a response more than 10 times of the background could be considered as oxidant contamination or adulteration of urine specimens.

Chromium↗

A diffusive sampler for personal monitoring of toluene diisocyanate (TDI) exposure; Part II: Laboratory and field evaluation of the dosimeter.

A passive monitor for TDI which utilizes microporous Teflon diffusion membranes and a 0.5% sulfuric acid (H2SO4) absorbing medium was evaluated. The collection rate of TDI is proportional to exposure dose from 10 to at least 300 ppb.hr, and response is equivalent for 2,4- and 2,6-TDI. Collection rate is independent of humidity and normal atmospheric pressure variations, while temperature causes a decrease of 1.0% per degree centigrade. Negative interference caused by ambient nitrogen dioxide (NO2) is eliminated by addition of sulfamic acid (HSO3 NH2) to the collecting medium. N-ethylmorpholine is a positive interferent. Field testing of the sampler against a reference impinger technique indicated a positive bias when TDI is aerosolized.

Air Pollutants, Occupational↗

Metabolism of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline in human hepatocytes: 2-amino-3-methylimidazo[4,5-f]quinoxaline-8-carboxylic acid is a major detoxification pathway catalyzed by cytochrome P450 1A2.

Metabolic pathways of the mutagen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) remain incompletely characterized in humans. In this study, the metabolism of MeIQx was investigated in primary human hepatocytes. Six metabolites were characterized by UV and mass spectroscopy. Novel metabolites were additionally characterized by 1H NMR spectroscopy. The carcinogenic metabolite, 2-(hydroxyamino)-3,8-dimethylimidazo[4,5-f]quinoxaline, which is formed by cytochrome P450 1A2 (P450 1A2), was found to be transformed into the N(2)-glucuronide conjugate, N(2)-(beta-1-glucosiduronyl)-2-(hydroxyamino)-3,8-dimethylimidazo[4,5-f]quinoxaline. The phase II conjugates N(2)-(3,8-dimethylimidazo[4,5-f]quinoxalin-2-yl)sulfamic acid and N(2)-(beta-1-glucosiduronyl)-2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, as well as the 7-oxo derivatives of MeIQx and N-desmethyl-MeIQx, 2-amino-3,8-dimethyl-6-hydro-7H-imidazo[4,5-f]quinoxalin-7-one (7-oxo-MeIQx), and 2-amino-6-hydro-8-methyl-7H-imidazo[4,5-f]quinoxalin-7-one (N-desmethyl-7-oxo-MeIQx), thought to be formed exclusively by the intestinal flora, were also identified. A novel metabolite was characterized as 2-amino-3-methylimidazo[4,5-f]quinoxaline-8-carboxylic acid (IQx-8-COOH), and it was the predominant metabolite formed in hepatocytes exposed to MeIQx at levels approaching human exposure. IQx-8-COOH formation is catalyzed by P450 1A2. This metabolite is a detoxication product and does not induce umuC gene expression in Salmonella typhimurium strain NM2009. IQx-8-COOH is also the principal oxidation product of MeIQx excreted in human urine [Turesky, R., et al. (1998) Chem. Res. Toxicol. 11, 217-225]. Thus, P450 1A2 is involved in both the metabolic activation and detoxication of this procarcinogen in humans. Analogous metabolism experiments were conducted with hepatocytes of untreated rats and rats pretreated with the P450 inducer 3-methylcholanthrene. Unlike human hepatocytes, the rat cell preparations did not produce IQx-8-COOH but catalyzed the formation of 2-amino-3,8-dimethyl-5-hydroxyimidazo[4,5-f]quinoxaline as a major P450-mediated detoxication product. In conclusion, our results provide evidence of a novel MeIQx metabolism pathway in humans through P450 1A2-mediated C(8)-oxidation of MeIQx to form IQx-8-COOH. This biotransformation pathway has not been detected in experimental animal species. Considerable interspecies differences exist in the metabolism of MeIQx by P450s, which may affect the biological activity of this mutagen and must be considered when assessing human health risk.

Animals↗

A spectrophotometric assay for nitrate in an excess of nitrite.

Miranda et al. have developed a method for simultaneous evaluation of nitrate and nitrite concentrations using reduction of nitrate by vanadium(III) combined with detection by the acidic Griess reaction [K.M. Miranda, M.G. Espey, D.A. Wink, A rapid, simple spectrophotometric method for simultaneous detection of nitrate and nitrite, Nitric Oxide 5 (2001) 62-71]. The sensitivity of the nitrate assay decline if the mixture analyzed contains a large excess of nitrite relative to nitrate, for instance, in the case of oxidation products of nitric oxide (NO) in aerated solutions, or in sweat. By this reason nitrite should be removed before the nitrate assay, if [NO2-]>>[NO3-]. Here we lay out an improved method allowing the above limitation to be erased, using sulfamic acid for nitrite removal. We also describe some modifications that enhance the reproducibility of the assay.

Calibration↗

Carbonic anhydrase inhibitors: synthesis and inhibition of cytosolic/tumor-associated carbonic anhydrase isozymes I, II, IX, and XII with N-hydroxysulfamides--a new zinc-binding function in the design of inhibitors.

A small library of N-hydroxysulfamides was synthesized by an original approach in order to investigate whether this zinc-binding function is efficient for the design of inhibitors targeting the cytosolic (hCA I and II) and transmembrane, tumor-associated (hCA IX and XII) isozymes of carbonic anhydrase (CA, EC 4.2.1.1). The parent derivative, N-hydroxysulfamide was a more potent inhibitor as compared to sulfamide or sulfamic acid against all isozymes, with inhibition constants in the range of 473 nM-4.05 microM. Its substituted n-decyl-, n-dodecyl-, benzyl-, and biphenylmethyl-derivatives were less inhibitory against hCA I (K(I)s in the range of 5.8-8.2 microM) but more inhibitory against hCA II (K(I)s in the range of 50.5-473 nM). The same situation was true for the tumor-associated isozymes, with K(I)s in the range of 353-790 nM against hCA IX and 372-874 nM against hCA XII. Some sulfamides/sulfamates possessing similar substitution patterns have also been investigated for the inhibition of these isozymes, being shown that in some particular cases sulfamides are more efficient inhibitors as compared to the corresponding sulfamates. Potent CA inhibitors targeting the cytosolic or tumor-associated CA isozymes can thus be designed from various classes of sulfonamides, sulfamides, or sulfamates and their derivatives, considering the extensive interactions in which the inhibitor and the enzyme active site are engaged, based on recent X-ray crystallographic data.

Amides↗

Reaction of cyclohexylamine with hypochlorite and enhancement of oxidation of plasma sulfhydryl groups by hypochlorite in vitro.

In this study we investigated the reaction of cyclamate and its major metabolite, cyclohexylamine (CyhNH2), with NaOCl. NaOCl at 100 microM was allowed to react with various concentrations of cyclamate and CyhNH2, and the reactivity was compared with those of reduced glutathione (GSH) and ascorbic acid. The results showed that CyhNH2 was less reactive with NaOCl than GSH but was slightly more reactive than ascorbic acid at concentrations below 50 microM. CyhNH2 at 75 and 100 microM did not further decrease NaOCl. Cyclamate was much less reactive than CyhNH2, with only 43% loss in NaOCl at 100 microM cyclamate. When human blood plasma was incubated with 0.75 microM NaOCl, inclusion of CyhNH2 enhanced oxidation of sulfhydryl groups in a concentration-dependent manner, with complete oxidation of SH groups at 7.5 mM CyhNH2. Cyclamate had no effect. This enhancement by CyhNH2 suggests the formation of reactive products from the reaction of CyhNH2 with NaOCl. Absorption spectra demonstrated that reaction of CyhNH2 with NaOCl at pH 7.4 produced N-monochloramine, as evidenced by the appearance of a new peak at 245 nm and by the disappearance of the 292-nm peak of NaOCl. Cyclamate, which contains a sulfamic acid instead of a primary amine, also reacted with NaOCl at pH 7.4, but the reaction was much less pronounced and the product was probably not monochloramine since the peak was at 270 nm rather than at 245 nm. Because cyclamate is an important sweetener in many countries for people with diabetes mellitus, the possibility exists that CyhNH2 may enhance oxidation of important proteins by HOCl/OCl-.

Ascorbic Acid↗

A transient model of mass transfer and kinetics in a passive vapor sampler.

A transient model of vapor contaminant diffusion and homogeneous reaction in a two-compartment passive sampler was formulated. The mathematical analysis considered finite reaction kinetics, bulk air boundary-layer effects, and the solubility of the vapor contaminant in the liquid absorbing/reacting medium. The model was evaluated using experimentally measured Cl2 uptake rates in a series of samplers of different dimensions containing a 0.1% aqueous sulfamic acid solution in the absorbing medium chamber. The theory predicts accurately the effects of sampler diameter, stagnant air chamber path length, and sampler orientation with respect to the flowing air on Cl2 uptake, with an average error of less than 10%. Chlorine uptake in a 33-mm diameter sampler with a 10.8-mm path length was found to be essentially independent of wind direction and varied by approximately 23% for wind speeds ranging from 5.1 to 203 cm s-1 (10-400 ft min-1). Calculations show that the sampler is sensitive to wind speed partly because of the Cl2 hydrolysis reaction, which produces HOCl and drops the vapor phase concentration of chlorine to near zero at the stagnant air/absorbing medium chamber interface, regardless of the rate of homogeneous reaction between HOCl and sulfamate anions. If the solubility of the vapor contaminant in the liquid absorbing medium were to obey Henry's Law (no hydrolysis reaction) and the homogeneous trapping reaction were sufficiently slow, then model calculations show that contaminant uptake could be controlled solely by reaction kinetics, although the sampling rates would be lower than those observed and predicted for the Cl2 case.

Air Pollutants, Occupational↗

Potential sources of copper contamination of farm milk supplies measured by atomic absorption spectrophotometry.

A method was developed to use atomic absorption spectrophotometry for copper measurements in milk filtrates prepared from equal volumes of milk and 20% trichloracetic acid. Results are reported for 11 farms for water supplies, wash and rinse solutions, and milk. Copper below 10 mug/liter was found at the well for the 5 farms with their own spring supply. Averages and ranges for all 11 farms in mug/liter were 33 (0 to 156) at the cold water tap in the milk house, 220 (8 to 1,360) at the hot water tap, 246 (8 to 1,722) in the wash sink with added detergent and hot water, and 275 (9 to 1,823) after using the wash solution. Rinse solution with hypochlorite in cold water showed a rise from 31 (1 to 157) before use to 51 (5 to 206) after use. Copper in milk averaged 99 mug/liter (72 to 163). In spite of relatively high copper in wash solutions, copper in milk was not correlated postively, giving rise to question whether adsorbed copper from such solutions can contribute much copper to milk. Thorough rinsing with low copper cold water and a high dilution ratio in milk were seen as mitigating factors. Direct contact of milk with copper bearing metals presented a greater opportunity for contamination. Removal of substantial amounts of copper from pipe lines and bulk tanks with sulfamic acid was demonstrated.

Agriculture↗

A simplified and convenient laboratory-scale preparation of 14N or 15N high molecular weight poly(dichlorophosphazene) directly from PCl5.

A simple and convenient one-pot synthesis of THF solutions of high molecular weight poly(dichlorophosphazene) [NPCl(2)](n), or the (15)N isotopomer [(15)NPCl(2)](n), starting directly from PCl(5) and NH(4)Cl or (15)NH(4)Cl in a solution of 1,2,4-trichlorobenzene in the presence of sulfamic acid and calcium sulfate dihydrate, is described. The solutions of [NPCl(2)](n) in THF, which are obtained free of poly(tetrahydrofuran) by preparing them in the presence of K(2)CO(3), can be reacted directly with phenols, biphenols, or even HO-CH(2)CF(3) in the presence of K(2)CO(3) or Cs(2)CO(3) to obtain, after a very simple workup, the corresponding polyphosphazene derivatives almost free of chlorine.

Journal Article↗

In vitro cytotoxicity of hepsulfam against human tumor cell lines and primary human tumor colony forming units.

Hepsulfam (sulfamic acid 1,7-heptanediyl ester, NSC 329680) is an alkylating agent currently in Phase I clinical trials. Hepsulfam was developed as an analog of busulfan, an alkylating agent that is used to treat patients with chronic myelogenous leukemia and for marrow ablation prior to bone marrow transplantation. The objective of this study was to identify the spectrum of human tumor cells that were sensitive to hepsulfam. The following three cytotoxicity assays were employed to evaluate the in vitro cytotoxic potential of hepsulfam: 1) primary human tumors were exposed to three levels of hepsulfam for a one hour or continuous exposure, and growth in soft agar was determined; 2) human non-tumor cells and tumor cell lines were compared in an assay that measured the conversion of 14C-glucose to 14CO2 as an index of viability; and 3) the toxicity of hepsulfam to hematopoietic progenitor cells was determined in a progenitor cell colony forming assay. Cytotoxicity was not observed for human tumor cells following one hour hepsulfam exposures; in contrast, marked dose-dependent cytotoxicity was observed with continuous exposures. In human tumor cell lines, the cytotoxicity of hepsulfam was compared directly with busulfan at equimolar concentrations. Hepsulfam was more cytotoxic than busulfan in all cell lines tested. Cytotoxic activity was seen in lung, melanoma, kidney, breast, colon, ovary and brain tumor cells. These results, along with the information obtained from Phase I trials, will facilitate selection of patients who could receive this agent in Phase II efficacy trials.

Antineoplastic Agents↗

Magic-angle sample spinning electron paramagnetic resonance--instrumentation, performance, and limitations.

An electron paramagnetic resonance (EPR) setup for line narrowing experiments with fast sample spinning at variable angles between the rotation axis and the static magnetic field is described and applied in the magic-angle sample spinning (MAS) EPR experiment at X-band frequencies (9.5 GHz). Sample spinning speeds up to 17 kHz at temperatures down to 200 K can be achieved with rotors of 4-mm outer and 2.5-mm inner diameter without severe losses in microwave amplitude compared to standard pulse EPR probeheads. A phase cycle is introduced that provides pure absorption MAS EPR spectra and allows one to distinguish between positive and negative frequency offsets (pseudo-quadrature detection). Possible broadening mechanisms in MAS EPR spectra are discussed. It is demonstrated both by theory and by experiment that the MAS EPR experiment requires excitation bandwidths that are comparable to the total spectral width, since otherwise destructive interference between contributions of spins with similar resonance offsets suppresses the signal. Experimental observations on the E(1) center in gamma-irradiated silica glass and on the SO(-)(3) radical in gamma-irradiated sulfamic acid are reported.

Electron Spin Resonance Spectroscopy↗

Measurement of nitrosodimethylamine by capillary gas chromatography-mass spectrometry with the 15N-labelled compound as an internal standard.

Artifactual formation of N-nitrosodimethylamine during the extraction procedure from aminopyrine and nitrite was examined. The use of the basic pH condition was the most effective in preventing artifactual formation. Sulfamic acid or ascorbic acid was partially effective in preventing artifactual formation. Since significant losses of volatile N-nitrosodimethylamine occur during the extraction and concentration steps, we analyzed N-nitrosodimethylamine by combined gas chromatography mass spectrometry with 15N-nitrosodimethylamine as an internal standard. The use of a fused silica capillary column enabled us to obtain a fine separation of the chromatogram. This methodology was applied to our model experiment, which was performed to locate the formation of N-nitrosodimethylamine when a rabbit was exposed to NO2 after the administration of aminopyrine. SO3 inhaled together with NO2 was found to increase the nitrosation.

Aminopyrine↗

Determination of urinary 4,4'-methylenedianiline and its acetylated metabolites by solid-phase extraction and HPLC analysis with UV and electrochemical detection.

An analytical procedure based on solid-phase extraction and high-performance liquid chromatography using both ultraviolet and electrochemical detection was developed to determine, without derivatization, stable urinary forms of 4,4'-methylenedianiline (MDA) and of its acetylated metabolites at the micrograms/l level, in post-shift urine from 63 exposed workers. The determination of MDA, N-acetyl MDA (MAMDA) and N,N'-diacetyl MDA (DAMDA) was achieved on the non-hydrolysed urine samples, and that of total MDA on urine samples after alkaline hydrolysis. It was necessary to protect urine samples with sulfamic acid in order to stabilize amines and to improve the precision and accuracy of the analyses. Under these conditions, unstable labile conjugates were determined as their parent stable amine. The distribution of total MDA, MDA, MAMDA and DAMDA was assessed in 116 urine samples. Their relative concentrations (arithmetic means) were found to be in the following order: total MDA > MAMDA > MDA > DAMDA. While MAMDA represented more than 50% of total MDA, MDA and DAMDA were lower than 15% and 3% respectively. Acetylation of MDA, described as a possible pathway of detoxication, is confirmed to be an important metabolization route in humans, essentially through the monoacetylated metabolite. However, the individual ratio MAMDA/total MDA was found to vary widely (roughly from 0% to 100%).

Acetylation↗