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PubMed2004

Novel adamantylated pyrimidines and their preliminary biological evaluations.

The synthesis of adamantylated pyrimidines was based on the reaction of 3-(adamantan-1-yl)-3-oxopropionic acid ethyl ester with urea, thiourea, guanidine as well as acetamidine, respectively. Then the compounds obtained were converted into respective bromo-, thio- and S-alkyl derivatives. The molecular structures for some compounds were studied by X-ray methods. The significant anticancer and antimicrobial properties of [2-(6-adamantan-1-yl-2-methylpyrimidin-4-ylthio)ethyl]dimethylamine were found.

Adamantane↗

PubMed2004

Intragastric formation and modulation of N-nitrosodimethylamine in a dynamic in vitro gastrointestinal model under human physiological conditions.

Human exposure to carcinogenic N-alkylnitrosamines can occur exogenously via food consumption or endogenously by formation of these compounds through nitrosation of amine precursors. Information on the intragastric formation of NDMA from complex mixtures of precursors and inhibitors in humans is not available. In this study the formation of N-nitrosodimethylamine (NDMA) has been quantitatively analysed in a dynamic in vitro gastrointestinal model, in which gastric conditions can be modulated and closely simulates the physiological situation in humans. Substantial amounts of NDMA were produced when nitrite and dimethylamine or codfish were simultaneously introduced into the model. However, humans are gradually exposed to nitrite by the intake of nitrate-containing food. Nitrate secreted in saliva is converted to nitrite by oral bacteria. To mimic the human exposure to nitrite in a realistic way, nitrite was gradually added into the gastric compartment, simulating the swallowing of nitrite containing oral fluid after the intake of nitrate at the level of 0.1-10 times the ADI. Under these conditions, the cumulative amounts of NDMA formed were 2.3-422 microg NDMA and 1.8-42.7 microg NDMA at a rapid and slow gastric pH decrease, respectively. Beside codfish, various fish species and batches in combination with nitrite, simulating the intake of for times the ADI of nitrate, were investigated. Herring, pollack and plaice were also able to induce NDMA formation. Mackerel, salmon and pike perch did not result in increased NDMA formation. Furthermore, the effect of nitrosation modulators on NDMA formation was investigated. Thiocyanate (2 mM) increased NDMA formation, but the increase was not statistically significant. In contrast, orange jus and tea effectively, but not totally, reduced the amount of NDMA formed in the gastric compartment. These experiments show that (1). the dynamic in vitro gastrointestinal model is an appropriate tool for mechanistic studies on the intragastric formation of nitrosamines, and (2). that the results obtained with this model are helpful in evaluating human cancer risk for the combined intake of codfish-like fish species and nitrate-containing vegetables.

Animals↗

PubMed2004

Fragmentation pathways of N(G)-methylated and unmodified arginine residues in peptides studied by ESI-MS/MS and MALDI-MS.

Protein methylation at arginine residues is a prevalent posttranslational modification in eukaryotic cells that has been implicated in processes from RNA-binding and transporting to protein sorting and transcription activation. Three main forms of methylarginine have been identified: N(G)-monomethylarginine (MMA), asymmetric N(G),N(G)-dimethylarginine (aDMA), and symmetric N(G),N'(G)-dimethylarginine (sDMA). To investigate gas-phase fragmentations and characteristic ions arising from methylated and unmodified arginine residues in detail, we subjected peptides containing these residues to electrospray triple-quadrupole tandem mass spectrometry. A variety of low mass ions including (methylated) ammonium, carbodiimidium, and guanidinium ions were observed. Fragment ions resulting from the loss of the corresponding neutral fragments (amines, carbodiimide, and guanidine) from intact molecular ions as well as from N- and C-terminal fragment ions were also identified. Furthermore, the peptides containing either methylated or unmodified arginines gave rise to abundant fragment ions at m/z 70, 112, and 115, for which cyclic ion structures are proposed. Electrospray ionization tandem mass spectra revealed that dimethylammonium (m/z 46) is a specific marker ion for aDMA. A precursor ion scanning method utilizing this fragment ion was developed, which allowed sensitive and specific detection of aDMA-containing peptides even in the presence of a five-fold excess of phosphorylase B digest. Interestingly, regular matrix-assisted laser desorption/ionization mass spectra recorded from aDMA- or sDMA-containing peptides showed metastable fragment ions resulting from cleavages of the arginine side chains. The neutral losses of mono- and dimethylamines permit the differentiation between aDMA and sDMA.

Arginine↗

PubMed2005

Histamine dehydrogenase from Rhizobium sp.: gene cloning, expression in Escherichia coli, characterization and application to histamine determination.

The gene encoding histamine dehydrogenase in Rhizobium sp. 4--9 has been cloned and overexpressed in Escherichia coli. The coding region of the gene was 2,079 bp and encoded a protein of 693 amino acids with a calculated molecular mass of 76,732 Da. This histamine dehydrogenase was related to histamine dehydrogenase from Nocardioides simplex (54.5% identical), trimethylamine dehydrogenase from Methylophilus methylotrophus (39.3% identical) and dimethylamine dehydrogenase from Hyphomicrobium X (38.1% identical), which have a covalent 6-S-cysteinyl flavin mononucleotide and a [4Fe--4S] cluster as redox cofactors. Sequence alignment and a UV-visible absorption spectrum supported the presence of these cofactors in this histamine dehydrogenase. The investigation of the enzymatic properties suggested that this enzyme exhibited the most excellent substrate specificity toward histamine among all amine oxidases or dehydrogenases found to date. The recombinant enzyme was able to be used for the colorimetric determination of histamine, which gave a linear calibration curve and identical data with conventional methods.

Animals↗

PubMed2003

Simultaneous detection of arginine, asymmetric dimethylarginine, symmetric dimethylarginine and citrulline in human plasma and urine applying liquid chromatography-mass spectrometry with very straightforward sample preparation.

Nitric oxide (NO) is synthesized by NO synthase from L-arginine, which can be competitively blocked by endogenous inhibitors such as asymmetric dimethylarginine (ADMA), but not by symmetric dimethylarginine (SDMA). ADMA is degraded by dimethylarginine dimethylaminohydrolase (DDAH) to dimethylamine and citrulline. A growing number of published clinical studies documented a strong correlation between increased ADMA blood levels and cardiovascular morbidity and mortality. We present here a highly sensitive method for the determination of this compounds in plasma and urine by means of HPLC-MS. The sample preparation is very simple and comprises only protein precipitation and concentration in the case of plasma samples and dilution in the case of urine. The samples are derivatized automatically with orthophthaldialdehyde and 2-mercaptoethanol, are separated on a 250 mm x 4 mm RP18 column by gradient elution with formate buffer/methanol and are detected by ESI-MS. The calibration functions are linear and cover the range from normal to pathologic concentration values of the analytes. The intra-day relative standard deviation (R.S.D.) of the assay for ADMA in plasma is 7.5% and the corresponding inter-day R.S.D. is 5.7%. In urine, these values for ADMA are 3.8 and 6.4%, respectively. All other analytes in plasma as well as in urine exhibit intra-day R.S.D. below 8%. The corresponding inter-day R.S.D. are all below 13%.

Arginine↗

PubMed2004

Determination of NG,NG-dimethyl-L-arginine, an endogenous NO synthase inhibitor, by gas chromatography-mass spectrometry.

A fully validated gas chromatographic-mass spectrometric (GC-MS) method for the accurate and precise quantification of NG,NG-dimethyl-L-arginine (asymmetric dimethylarginine, ADMA), an endogenous inhibitor of the NO synthase, in cell culture supernatants and in small volumes of plasma is described. ADMA was concentrated by solid phase extraction and converted to its methyl ester pentafluoropropionic amide derivative. The derivatives were analyzed without any further purification. Using gas chromatography-chemical ionization mass spectrometry, fragment ions at m/z 634 and m/z 640 were obtained for ADMA and for NG,NG-[2H6]-dimethyl-L-arginine ([2H6]-ADMA) as internal standard, respectively. [2H6]-ADMA was synthesized by reaction of L-ornithine fastened at bromcyan-agarose with dimethylamine. The limit of detection of the method was 2 fmol, while the limit of quantitation for cell culture supernatants was 0.05 microM. The method was validated in a concentration range of 0-1.2 microM in cell culture medium and 0-2 microM in 50 microl aliquots of human plasma. The precision was > or =97% and the accuracy was determined to be > or =94%. This method is fast, rugged and an alternative to high performance liquid chromatography (HPLC) analysis of ADMA in cell culture supernatants and small volumes of human plasma.

Arginine↗

PubMed2004

Particle formation in the hydrolysis of tetraethyl orthosilicate in pH buffer solution.

Particle formation in the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) was studied by varying pH (9.5-11) with the basic catalysts NH3, methylamine (MA), and dimethylamine (DMA) in the presence of 5 mol/m3 CH3COOH, which was chosen to suppress time variations of pH and ionic strength during the reaction. Spherical particles were formed for MA and DMA at catalyst concentrations of 0.02-0.2 kmol/m3 and for NH3 at catalyst concentrations of 0.1-1.5 kmol/m3. In a common range of catalyst concentrations for spherical particle formation, average particle size was largest for DMA and smallest for NH3. Hydrolysis rate of TEOS could be quantified by the use of buffer systems as a function of TEOS and OH- concentrations. A specific relation was not found between the hydrolysis and the particle size. The zeta potential of silica particles measured in the reaction solvent was in the order DMA < MA < NH3, and ionic strength, estimated from pH in the reactions, was in the order DMA approximately equal to MA > NH3. This suggested that the particle sizes were controlled by electrostatic particle interactions.

Acetates↗

PubMed2004

Mixed micelles containing sodium oleate: the effect of the chain length and the polar head group.

We have investigated the mixing behavior of binary mixtures of the alkylglucosides (CnG) octyl beta-D-glucoside and decyl D-glucoside in combination with sodium oleate (NaOl), and the amine oxide surfactants (AO) N,N-dimethyldodecylamine oxide, N,N-bis (2-hydroxyethyl)dodecylamine oxide, and 3-lauramidopropyl-N,N-dimethylamine oxide in combination with NaOl. From the equilibrium surface tension measurements, the critical micelle concentration (cmc) data were obtained as functions of the composition. Values of the cmc were analyzed according to both the regular solution model developed by Rubingh for mixed micelles and Maeda's formulation for ionic/nonionic mixed micelles. Two interaction parameters, beta and B1, were estimated from the regular solution model and Maeda's formulation, respectively. For NaOl/CnG mixed systems, a decrease in the hydrocarbon chain length of CnG resulted in a stronger interaction with NaOl from both beta and B1 values. For NaOl/AO mixed systems, the bulkiness of a polar head group of AO surfactants influenced the interaction between NaOl and AO. The dynamic surface tension measurements show that all surface tension values of surfactant solutions examined decreased with the time. We found that the time dependence of surface tension values for NaOl mixed systems was greatly influenced by the presence of NaOl rather than the other component.

Chemical Phenomena↗

PubMed2005

Silica coating of silver nanoparticles using a modified Stober method.

Silver nanoparticles prepared through a borohydride-reduction method were directly coated with silica by means of a seeded polymerization technique based on the Stober method. Various amine catalysts were used for initialization of a sol-gel reaction of TEOS with no need for a prior surface modification. Use of dimethylamine (DMA) as a catalyst was found to be necessary to obtain a proper coating. The silica shell thickness was varied from 28 to 76 nm for TEOS concentrations of 1-15 mM at 11.1 M water and 0.8 M DMA. The optical spectra of the core-shell silver-silica composite particles show a qualitative agreement with predictions by Mie theory.

Journal Article↗

PubMed2005

Preparation of Au/TiO2 nanocomposites and their catalytic activity for DPPH radical scavenging reaction.

Au/TiO2 nanocomposites have been prepared by UV photolysis or chemical reduction of a Au(III) complex formed on a spherical or a rodlike TiO2 support, and their catalytic activity for 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging reaction was investigated. The chemical reduction with dimethylamine borane (DMAB) provided smaller gold nanoparticles than those synthesized by UV photolysis. Type of the TiO2 also affected the size of gold particles; smaller gold particles were deposited on the spherical TiO2 support than on rodlike one. For the radical scavenging reaction, the Au/TiO2 nanocomposites prepared by chemical reduction exhibited a higher catalytic activity than those photochemically prepared, and rodlike TiO2 provided a higher activity than spherical one. The effects of preparation methods and type of TiO2 supports on the catalytic activity are discussed.

Journal Article↗

PubMed2005

Synthesis of submicrometer-sized titania spherical particles with a sol-gel method and their application to colloidal photonic crystals.

A synthetic method for preparing submicrometer-sized titania particles is proposed, which is based on hydrolysis of titanium alkoxide with the use of a cosolvent and an amine catalyst for alkoxide hydrolysis. The preparation was performed with different amines of ammonia, methylamine (MA), and dimethylamine (DMA) in different solvents of ethanol/acetonitrile, ethanol/methanol, ethanol/acetone, ethanol/acetonitrile, and ethanol/formamide for 0.1-0.3 M water and 0.03 M titanium tetraisopropoxide (TTIP) at temperatures of 10-50 degrees C. The use of the ethanol/acetonitrile solvent with MA was required for preparing monodispersed, spherical particles. The number average of the titania particle sizes and their coefficient of variation were varied from 143 to 551 nm and from 5.7 to 20.6%, respectively, with reaction temperature and concentrations of water and MA. Colloidal crystals of titania particles fabricated with a sedimentation method revealed reflection peaks attributed to Bragg's diffraction. Annealing at 100-1000 degrees C led to shrinkage and crystallization of titania particles followed by an increase in the refractive index of titania particles.

Journal Article↗

PubMed2006

Preparation of an aminated macroreticular resin adsorbent and its adsorption of p-nitrophenol from water.

A chloromethylated styrene-divinylbenzene copolymer was post-cross-linked through Friedel-Crafts reaction to get a macroreticular resin adsorbent NA-01, and then chemically modified by dimethylamine to obtain an aminated adsorbent NA-01A. Batch adsorption runs of p-nitrophenol from aqueous solution onto adsorbent NA-01A were conducted to evaluate the effect of amino group on adsorption. The adsorption capacity of p-nitrophenol on NA-01A increased noticeably by comparison with the mother adsorbent. A linear relationship was observed between the adsorption capacity of NA-01A caused by amination and the equilibrium concentration of p-nitrophenol in aqueous solution, which can be reasonably elucidated by a modified isotherm equation based on the Freundlich model. The breakthrough curves on both adsorbents were experimentally determined and also predicted by the mathematic model based on the non-linear wave propagation theory and the corresponding isotherm model. The model based on the Freundlich model gave a good prediction of the breakthrough curve on NA-01, but a deviation occurred for NA-01A when C/C0 less than 0.3. However, another model based on the modified isotherm equation provided a better prediction for the breakthrough curves on NA-01A.

Adsorption↗

PubMed2006

Prediction of N-nitrosodimethylamine (NDMA) formation as a disinfection by-product.

This study investigated the possibility of a statistical model application for the prediction of N-nitrosodimethylamine (NDMA) formation. The NDMA formation was studied as a function of monochloramine concentration (0.001-5mM) at fixed dimethylamine (DMA) concentrations of 0.01mM or 0.05mM. Excellent linear correlations were observed between the molar ratio of monochloramine to DMA and the NDMA formation on a log scale at pH 7 and 8. When a developed prediction equation was applied to a previously reported study, a good result was obtained. The statistical model appears to predict adequately NDMA concentrations if other NDMA precursors are excluded. Using the predictive tool, a simple and approximate calculation of NDMA formation can be obtained in drinking water systems.

Dimethylnitrosamine↗

PubMed2005

NMR spectroscopic-based metabonomic investigation on the acute biochemical effects induced by Ce(NO3)3 in rats.

An integrated metabonomic approach based on high-resolution (1)H NMR spectroscopy has been applied to the investigation of the acute biochemical effects caused by Ce(NO(3))(3) in rats. Male Wistar rats were separated into 8 groups and each was treated with one of following compounds, mercury II chloride (HgCl(2)), 2-bromoethanamine hydrobromide (BEA), carbon tetrachloride (CCl(4)), alpha-naphthylisothiocyanate (ANIT), and three doses of Ce(NO(3))(3) (i.p. 2, 10 and 50mg/kg body weight). Urine was collected over a 48-h time course, and serum and tissue samples (liver and kidney) were gained after exposure to Ce(NO(3))(3) for 48 h. Histopathology and plasma clinical chemistry were also performed for all the tissue and plasma samples. Urine and serum samples were analyzed by 600 MHz (1)H NMR spectroscopy. All the (1)H NMR spectra were data-processed and analyzed using principal components analysis or hierarchical clustering analysis to show the time- and dose-dependent biochemical variations induced by Ce(NO(3))(3). Metabolic profiles of urinary (1)H NMR spectra from animals treated with Ce(NO(3))(3) exhibited an increase in trimethylamine N-oxide (TMAO), dimethylamine (DMA), dimethylglycine (DMG), taurine (Tau) and amino acids (valine, leucine and isoleucine), together with a decrease in citrate. The (1)H NMR spectral analysis of serum presented the elevation of acetone, acetoacetate, lactate and creatinine levels. These findings indicated the impairment of fatty acid beta-oxidation in liver mitochondria and renal lesions. This work illustrates the high reliability of NMR-based metabonomic approach on the study of the biochemical effects induced by rare earths.

Animals↗

PubMed2006

Elevated plasma concentrations of the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine in citrullinemia.

Citrullinemia is an inborn error of the urea cycle with deficiency of the argininosuccinate synthase. It is characterized by elevated concentrations of l-citrulline and decreased levels of l-arginine in body fluids. Asymmetric dimethylarginine is an endogenous inhibitor of nitric oxide synthase that converts l-arginine to l-citrulline and nitric oxide (NO). Asymmetric dimethylarginine is hydrolyzed by the enzyme dimethylarginine dimethylaminohydrolase to l-citrulline and dimethylamine. Elevation of l-citrulline in citrullinemia prompted us to study the l-arginine/NO pathway in this disorder. In 8 children with citrullinemia (3 days to 3 years of age), elevated plasma levels of asymmetric dimethylarginine (P = .028) were found compared with age-matched healthy children. We hypothesize that the l-arginine/NO pathway plays a role in the pathophysiology of citrullinemia.

Arginine↗

PubMed2006

Dominant lethal effects of 2,4-D in Biomphalaria glabrata.

Dominant lethal effects of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) were evaluated in the freshwater snail Biomphalaria glabrata. Wild-type snails were exposed during 10 days to 50, 75 and 100ppm of 2,4-D dimethylamine salt (2,4-D DMA) and paired with non-exposed albino snails 1, 11, 25 and 40 days after the exposure. The offspring of the non-exposed albino snails was scored for lethal malformations. One day after the exposure, a significant effect was observed at 75 and 100ppm without a dose-response relationship. After 11 days, the effect was observed only at the highest dose. After 25 days, significant increases in the dominant lethal effects occurred at 50 and 75ppm; effects were directly related to the doses. Background levels of lethal malformations were resumed after 40 days. Although the major and direct measure of dominant lethal mutations is the rate of lethal malformations in the heterozygous offspring of the albino snails, the sensitivity of the assay was substantially increased with the evaluation of all non-viable embryos, that are the sum of those with lethal malformations, identified or not as wild-type.

2,4-Dichlorophenoxyacetic Acid↗

PubMed2004

Novel carbon-11 labeled 4-dimethylamino-but-2-enoic acid [4-(phenylamino)-quinazoline-6-yl]-amides: potential PET bioprobes for molecular imaging of EGFR-positive tumors.

We have previously reported of labeled reversible and irreversible EGFR inhibitors, such as 4-(3,4-dichloro-6-fluoroanilino)-6,7-dimethoxyquinazoline (ML01) and 6-acrylamido-4-(3,4-dichloro-6-fluoroanilino)quinazoline (ML03), to be suboptimal as imaging agents. On the basis of these studies, a new generation of novel, more chemically stable irreversible inhibitors was labeled with carbon-11 as potential positron emission tomography (PET) biomarkers for molecular imaging of epidermal growth factor receptor (EGFR)-positive tumors. In these new labeled, irreversible inhibitors the acryl-amide group at the 6-position of the quinazoline ring was replaced with a 4-dimethylamino-but-2-enoic amide. The nonlabeled compounds were evaluated in vitro to determine their EGFR autophosphorylation IC(50) values. The IC(50) values indicated that these new irreversible compounds possess similar potencies towards the EGFR, as the parent compound, ML03. These compounds were labeled with carbon-11 at the dimethylamine moiety, using the well known labeling reagent C-11 MeI. The labeling procedure was automated using a commercial module. The final products were obtained with 10% decay corrected radiochemical yield, 99% radiochemical purity, 96% chemical purity, and a high specific activity of 2.7 Ci/micromol EOB. The high potency of these new labeled bioprobes towards the EGFR establishes their potential to serve as PET agents for molecular imaging of EGFR-positive tumors.

Biomarkers, Tumor↗

PubMed2004

Chemical inhibition of PCDD/F formation in incineration processes.

This review summarises results of our pilot-scale experiments to find suitable inhibitors for preventing the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) during waste incineration and to specify the role of the main factors affecting the inhibition process, and is based on doctoral dissertation of Ruokojaärvi (2002). Results of previous experiments reported by other researchers are also presented and compared with ours. The detailed aims of our experiments were (1) to compare the effects of different inhibitors on PCDD/F formation during incineration in a pilot plant, (2) to investigate the role of the particle size distribution of the flue gas on the inhibition of PCDD/Fs, and (3) to find the main parameters affecting PCDD/F inhibition in waste incineration. Prevention of the formation of PCDD/Fs with chemical inhibitors and the effects of different supply points, feed temperatures and process parameters were studied in a pilot scale incinerator (50 kW) using light heating oil and refuse-derived fuel as test fuels. Various concentrations of the gaseous inhibitors (sulfur dioxide, ammonia, dimethylamine and methyl mercaptan) were sprayed into the flue gases after the furnace, in addition to which urea was dissolved in water and injected in at different concentrations. The residence time of the flue gas between the furnace and the PCDD/F sampling point was varied in the tests. In another set of urea tests, urea-water solutions at three concentrations were mixed with the RDF prior to incineration. PCDD/F and chlorophenol concentrations, together with other flue gas parameters (e.g. temperature, O2, CO, CO2 and NO), were analysed in the cooling flue gases. The gaseous and liquid inhibitors both notably reduced PCDD/F concentrations in the flue gas, the reductions achieved with the gaseous inhibitors varying from 50 to 78%, with dimethyl amine the most effective, while that produced with urea was up to 90%. The PCDD/F reductions were greater at increased inhibitor concentrations and with increased residence time of the flue gas between the furnace and the sampling point. PCDD/F concentrations in the particle phase decreased much more markedly than those in the gas phase. The urea inhibitor did not alter the particle size distribution of the PCDD/Fs when the amount of inhibitor was adequate. Chemical inhibitors seem to offer a very promising technique for preventing the formation of PCDD/Fs in waste incineration. The addition of urea to the fuel before combustion proved to be very effective approach and could be a useful technique even in the full-scale incinerators.

Journal Article↗