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Reference Compounds (reference + compound)
Selected AbstractsChemInform Abstract: Crystalline Aluminum Hydroxy Fluorides , Suitable Reference Compounds for 19F Chemical Shift Trend Analysis of Related Amorphous Solids.CHEMINFORM, Issue 40 2008Rene Koenig Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] 13C/12C Ratios of endogenous urinary steroids investigated for doping control purposesDRUG TESTING AND ANALYSIS, Issue 2 2009Thomas Piper Abstract In order to detect the misuse of endogenous anabolic steroids such as testosterone by athletes a total of n = 1734 suspicious urine samples were investigated by gas chromatography/combustion/isotope ratio mass spectrometry throughout the years 2005, 2006 and 2007. The 13C/12C ratio of a target substance (androsterone, a testosterone metabolite) was compared to the 13C/12C ratio of an endogenous reference compound (11,-hydroxyandrosterone). N = 1340 samples were investigated due to elevated testosterone/epitestosterone ratios, with n = 87 (6.5%) exceptional findings regarding their isotopic ratios. An additional n = 164 samples were investigated because of elevated dehydroepiandrosterone concentrations, with n = 2 (1.2%) exceptional findings. The remainder were subjected to isotope ratio analysis because of elevated androsterone levels or because this was requested by sports federations. Significant differences between female and male samples were found for the 13C/12C ratios of androsterone and 11,-hydroxyandrosterone but not for samples taken in or out of competition. A further n = 645 samples originating from other World Anti-Doping Agency accredited laboratories, mainly throughout Europe as well as South America, South Africa and Southeast Asia, were investigated. The 13C/12C ratios of the urinary steroids differ significantly for each geographical region, reflecting the dietary status of the individuals. The system stability over time has been tested by repeated injections of a standard solution and repeated processing of frozen stored blank urine. Despite a drift over time in absolute 13C/12C ratios, no significant change in the difference of 13C/12C (11,-hydroxyandrosterone) minus 13C/12C (androsterone) could be observed. Copyright © 2009 John Wiley & Sons, Ltd. Copyright © 2009 John Wiley & Sons, Ltd. [source] Comparative study on the antimicrobial activities of different sandalwood essential oils of various originFLAVOUR AND FRAGRANCE JOURNAL, Issue 3 2006Leopold Jirovetz Abstract In total, eight samples of different sandalwoods [Amyris balsamifera L., Santalum album L. and Santalum spicatum (R.Br.) A.DC.] and a mixture of , - and , -santalols, as well as eugenol as reference compound, were tested by an agar dilution and agar diffusion method for their antimicrobial activities against the yeast Candida albicans, the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacteria Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae. The main compounds of each essential oil were investigated by gas chromatographic,spectroscopic (GC-FID and GC,MS) and ,olfactory methods to obtain information about the inßuence of these volatiles on the observed antimicrobial effects. For the santalol mixture, as well as for one S. album and one S. spicatum sample with moderate concentrations of santalols, antimicrobial activity was found against all the strains used. The A. balsamifera sample, containing only a small quantity of , -santalol and nearly no , -santalol, showed high effects only against Klebsiella pneumoniae, while against the other strains weak or no activity was observed. Therefore, santalols in medium and/or high concentrations in sandalwood oils show a significant inßuence on antimicrobial potential in such natural products. Copyright © 2006 John Wiley & Sons, Ltd. [source] Kinetic and product study of the gas-phase reaction of sabinaketone with OH radicalINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2007Nathalie Carrasco Sabinaketone is one major photooxidation product of sabinene, an important biogenic volatile organic compound. This article provides the first product study and the second rate constant determination of its reaction with OH radicals. Experiments were investigated under controlled conditions for pressure and temperature in the LISA indoor simulation chamber using FTIR spectrometry. Kinetic study was carried out at 295 ± 2 K and atmospheric pressure using the relative rate technique with isoprene as the reference compound. The rate constant was found to be ksabinaketone + OH = (7.1 ± 1.0) × 10,12 molecule,1 cm3 s,1. Acetone and formaldehyde were detected as products of the reaction with the respective yields of Racetone = 0.9 ± 0.2 and RHCHO = 1.2 ± 0.3. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 415,421, 2007 [source] Gas-phase reaction of hydroxyl radicals with m -, o - and p -cresolINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 9 2006Cecile Coeur-Tourneur The gas-phase reaction of oxygenated aromatic compounds m -cresol, o -cresol, and p -cresol with hydroxyl radicals has been studied by GC-MS. Experiments have been performed in a large-volume photoreactor (8000 L) at 294 ± 2 K and atmospheric pressure. The relative kinetic method was used to determine the rate constants for these reactions, with 1,3,5-trimethylbenzene as a reference compound. The rate constants obtained are kOH(m -cresol) = (5.88 ± 0.92) × 10,11 cm3 molecule,1 s,1, kOH(o -cresol) = (4.32 ± 0.52) × 10,11 cm3 molecule,1 s,1, and kOH(p -cresol) = (4.96 ± 0.75) × 10,11 cm3 molecule,1 s,1. The degradation products observed and their respective molar yields were methyl-1,4-benzoquinone 12.4 ± 1.2%, 5-methyl-2-nitrophenol 1.5 ± 0.3%, and 3-methyl-2-nitrophenol 1.4 ± 0.3% from m -cresol, methyl-1,4-benzoquinone 5.6 ± 0.9%, and 6-methyl-2-nitrophenol 4.7 ± 0.8% from o -cresol, and 4-methyl-2-nitrophenol 17.2 ± 2.5% from p -cresol. This kinetic and product data are compared with the literature, and the reaction mechanisms are discussed. Our results are in accordance with the previous studies (Atkinson, J Phys Chem Ref Data 1989, Monograph (1), 1,246; Atkinson and Aschmann, Int J Chem Kinet 1990, 22, 59,67; Atkinson et al., Environ Sci Technol 1992, 26, 1397,1403; Atkinson et al., J Phys Chem 1978, 82, 2759,2805; Olariu et al., Atmos Environ 2002, 36, 3685,3697; Semadeni et al., Int J Chem Kinet 1995, 27, 287,304) and confirm the methyl-1,4-benzoquinone yields determined by a different experimental technique (long-path Fourier transform infrared FT-IR (Olariu et al., 2002)). © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 553,562, 2006 [source] Kinetics of the gas-phase reaction of CF3OC(O)H with OH radicals at 242,328 KINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 6 2004L. Chen The rate constants, k1, of the reaction of CF3OC(O)H with OH radicals were measured by using a Fourier transform infrared spectroscopic technique in an 11.5-dm3 reaction chamber at 242,328 K. OH radicals were produced by UV photolysis of an O3,H2O,He mixture at an initial pressure of 200 Torr. Ozone was continuously introduced into the reaction chamber during UV irradiation. With CF3OCH3 as a reference compound, k1 at 298 K was (1.65 ± 0.13) × 10,14 cm3 molecule,1 s,1. The temperature dependence of k1 was determined as (2.33 ± 0.42) × 10,12 exp[,(1480 ± 60)/T] cm3 molecule,1 s,1; possible systematic uncertainty could add an additional 20% to the k1 values. The atmospheric lifetime of CF3OC(O)H with respect to reaction with OH radicals was calculated to be 3.6 years. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 337,344 2004 [source] Rate constants for the gas-phase reaction of CF3CF2CF2CF2CF2CHF2 with OH radicals at 250,430 KINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 1 2004L. Chen The rate constants k1 for the reaction of CF3CF2CF2CF2CF2CHF2 with OH radicals were determined by using both absolute and relative rate methods. The absolute rate constants were measured at 250,430 K using the flash photolysis,laser-induced fluorescence (FP-LIF) technique and the laser photolysis,laser-induced fluorescence (LP-LIF) technique to monitor the OH radical concentration. The relative rate constants were measured at 253,328 K in an 11.5-dm3 reaction chamber with either CHF2Cl or CH2FCF3 as a reference compound. OH radicals were produced by UV photolysis of an O3,H2O,He mixture at an initial pressure of 200 Torr. Ozone was continuously introduced into the reaction chamber during the UV irradiation. The k1 (298 K) values determined by the absolute method were (1.69 ± 0.07) × 10,15 cm3 molecule,1 s,1 (FP-LIF method) and (1.72 ± 0.07) × 10,15 cm3 molecule,1 s,1 (LP-LIF method), whereas the K1 (298 K) values determined by the relative method were (1.87 ± 0.11) × 10,15 cm3 molecule,1 s,1 (CHF2Cl reference) and (2.12 ± 0.11) × 10,15 cm3 molecule,1 s,1 (CH2FCF3 reference). These data are in agreement with each other within the estimated experimental uncertainties. The Arrhenius rate constant determined from the kinetic data was K1 = (4.71 ± 0.94) × 10,13 exp[,(1630 ± 80)/T] cm3 molecule,1 s,1. Using kinetic data for the reaction of tropospheric CH3CCl3 with OH radicals [k1 (272 K) = 6.0 × 10,15 cm3 molecule,1 s,1, tropospheric lifetime of CH3CCl3 = 6.0 years], we estimated the tropospheric lifetime of CF3CF2CF2CF2CF2CHF2 through reaction with OH radicals to be 31 years. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 26,33, 2004 [source] Kinetics of the gas-phase reaction of n -C6,C10 aldehydes with the nitrate radicalINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2003Jun Noda Rate coefficients for gas-phase reaction between nitrate radicals and the n -C6,C10 aldehydes have been determined by a relative rate technique. All experiments were carried out at 297 ± 2 K, 1020 ± 10 mbar and using synthetic air or nitrogen as the bath gas. The experiments were made with a collapsible sampling bag as reaction chamber, employing solid-phase micro extraction for sampling and gas chromatography/flame ionization detection for analysis of the reaction mixtures. One limited set of experiments was carried out using a glass reactor and long-path FTIR spectroscopy. The results show good agreement between the different techniques and conditions employed as well as with previous studies (where available). With butanal as reference compound, the determined values (in units of 10,14 cm3 molecule,1 s,1) for each of the aldehydes were as follows: hexanal, 1.7 ± 0.1; heptanal, 2.1 ± 0.3; octanal, 1.5 ± 0.2; nonanal, 1.8 ± 0.2; and decanal, 2.2 ± 0.4. With propene as reference compound, the determined rate coefficients were as follows: heptanal, 1.9 ± 0.2; octanal, 2.0 ± 0.3; and nonanal, 2.2 ± 0.3. With 1-butene as reference compound, the rate coefficients for hexanal and heptanal were 1.6 ± 0.2 and 1.8 ± 0.1, respectively. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 120,129, 2003 [source] Kinetics and products of the reactions of selected diols with the OH radicalINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2001Heidi L. Bethel Using a relative rate method, rate constants have been measured at 296 ± 2 K for the gas-phase reactions of OH radicals with 1,2-butanediol, 2,3-butanediol, 1,3-butanediol, and 2-methyl-2,4-pentanediol, with rate constants (in units of 10,12 cm3 molecule,1 s,1) of 27.0 ± 5.6, 23.6 ± 6.3, 33.2 ± 6.8, and 27.7 ± 6.1, respectively, where the error limits include the estimated overall uncertainty of ±20% in the rate constant for the reference compound. Gas chromatographic analyses showed the formation of 1-hydroxy-2-butanone from 1,2-butanediol, 3-hydroxy-2-butanone from 2,3-butanediol, 1-hydroxy-3-butanone from 1,3-butanediol, and 4-hydroxy-4-methyl-2-pentanone from 2-methyl-2,4-pentanediol, with formation yields of 0.66 ± 0.11, 0.89 ± 0.09, 0.50 ± 0.09, and 0.47 ± 0.09, respectively, where the indicated errors are the estimated overall uncertainties. Pathways for the formation of these products are presented, together with a comparison of the measured and estimated rate constants and product yields. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 310,316, 2001 [source] Exact mass measurement on an electrospray ionization time-of-flight mass spectrometer: error distribution and selective averagingJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2003Jiejun Wu Abstract An automated, accurate and reliable way of acquiring and processing flow injection data for exact mass measurement using a bench-top electrospray ionization time-of-flight (ESI-TOF) mass spectrometer is described. Using Visual Basic programs, individual scans were selected objectively with restrictions on ion counts per second for both the compound of interest and the mass reference peaks. The selected ,good scans' were then subjected to two different data-processing schemes (,combine-then-center' and ,center-then-average'), and the results were compared at various ion count limit settings. It was found that, in general, the average of mass values from individual scans is more accurate than the centroid mass value of the combined (same) scans. In order to acquire a large number of good scans in one injection (to increase the sampling size for statistically valid averaging), an on-line dilution chamber was added to slow down the typically rapid mass chromatographic peak decay in flow-injection analysis. This simple addition worked well in automation without the need for manual sample dilution. In addition, by dissolving the reference compound directly into the mobile phase, manual syringe filling can be eliminated. Twenty-seven samples were analyzed with the new acquisition and process routines in positive electrospray ionization mode. For the best method found, the percentage of samples with RMS error less than 5 ppm was 100% with repetitive injection data (6 injections per sample), and 95% with single injection data. Afterwards, 31 other test samples were run (with MW ranging from 310 to 3493 Da, 21 samples in ESI+ and 10 in ESI, mode) and processed with similar parameters and 100% of them were mass-calculated to RMS error less than 5 ppm also. Copyright © 2003 John Wiley & Sons, Ltd. [source] CH3CH2SCH3,+,OH radicals: temperature-dependent rate coefficient and product identification under atmospheric pressure of air,JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 10 2010Gabriela Oksdath-Mansilla Abstract Relative rate coefficients have been determined for the gas-phase reaction of hydroxyl (OH) radicals with ethyl methyl sulfide (EMS) using isobutene as a reference compound. The experiments were performed in a 1080,L quartz glass photoreactor in the temperature range of 286,313,K at a total pressure of 760,±,10,Torr synthetic air using in situ FTIR absorption spectroscopy to monitor the concentration-time behaviors of reactants and products. OH radicals were produced by the 254,nm photolysis of hydrogen peroxide (H2O2). The kinetic data obtained were used to derive the following Arrhenius expression valid in the temperature range of 286,313,K (in units of cm3,molecule,1,s,1): The rate coefficient displays a negative temperature dependence and low pre-exponential factor which supports the existence of an addition mechanism for the reaction involving reversible OH-adduct formation. The results are compared with previous data of other sulfides from the literature and are rationalized in terms of structure,reactivity relationships. Additionally, product identification of the title reaction was performed for the first time by the FTIR technique under atmospheric conditions. Sulfur dioxide, formaldehyde, and formic acid were observed as degradation products in agreement with the two possible reaction channels (addition/abstraction). Copyright © 2010 John Wiley & Sons, Ltd. [source] UV-photodimerization in uracil-substituted dendrimers for high density data storageJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2007Brian Lohse Abstract Two series of uracil-functionalized dendritic macromolecules based on poly (amidoamine) PAMAM and 2,2-bis(hydroxymethylpropionic acid) bis-MPA backbones were prepared and their photoinduced (2,+2,) cycloaddition reactions upon exposure to UV light at 257 nm examined. Dendrimers up to 4th generation were synthesized and investigated as potential materials for high capacity optical data storage with their dimerization efficiency compared to uracil as a reference compound. This allows the impact of increasing the generation number of the dendrimers, both the number of chromophores, as well as the different steric environments, on the performance of each series of dendrimers to be investigated. The (uracil)12 -[G-2]-bis-MPA and (uracil)8 -[G-1]-PAMAM were observed to have high dimerization efficiency in solution with different behavior being observed for the PAMAM and bis-MPA dendrimers. The dendrimers with the best dimerization efficiency in solution were then examined in the solid state as thin films cast on quartz plates, and their film qualities along with their photodimerization performance studied. High quality films with a transmission response of up to 70% in 55 s. when irradiated at 257 nm with an intensity of 70 mW/cm2 could be obtained suggesting future use as recording media for optical data storage. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4401,4412, 2007 [source] Antigenotoxic effect of extract from Cynara cardunculus L.PHYTOTHERAPY RESEARCH, Issue 1 2008E. Miadokova Abstract The extract of artichoke Cynara cardunculus L. (CCE) was investigated for its potential antigenotoxic and antioxidant effects using four experimental model systems. In the Saccharomyces cerevisiae mutagenicity/antimutagenicity assay, CCE significantly reduced the frequency of 4-nitroquinoline- N -oxide-induced revertants at the ilv1 locus and mitotic gene convertants at the trp5 locus in the diploid Saccharomyces cerevisiae tester strain D7. In the simultaneous toxicity and clastogenicity/anticlastogenicity assay, it exerted an anticlastogenic effect against N-nitroso- N,-methylurea-induced clastogenicity in the plant species Vicia sativa L. On the contrary, despite CCE not being mutagenic itself, in the preincubation Ames assay with metabolic activation, it significantly increased the mutagenic effect of 2-aminofluorene in the bacterial strain Salmonella typhimurium TA98. In the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay, CCE exhibited considerable antioxidant activity. The SC50 value representing 0.0054% CCE corresponds to an antioxidant activity of 216.8 µm ascorbic acid which was used as a reference compound. Although the mechanism of CCE action still remains to be elucidated, different possible mechanisms are probably involved in the CCE antigenotoxic effects. It could be concluded that CCE is of particular interest as a suitable candidate for an effective chemopreventive agent. Copyright © 2007 John Wiley & Sons, Ltd. [source] Synthesis and Antifungal Activity of 1-Aryl-3-phenethylamino-1-propanone Hydrochlorides and 3-Aroyl-4-aryl-1-phenethyl-4-piperidinolsARCHIV DER PHARMAZIE, Issue 5 2010Ebru Mete Abstract Mono-Mannich bases, 1-aryl-3-phenethylamino-1-propanone hydrochlorides, 1a, 2a, 3a, 4a, 5a, 6a, 7a, 8a, 9a, and semi-cyclic mono-Mannich bases, 3-aroyl-4-aryl-1-phenethyl-4-piperidinols, 1b, 2b, 3b, 4b, 5b, 6b, 7b, 8b, 9b, were synthesized by a non-classical Mannich reaction. The aryl part was: C6H5 for 1a, 1b; 4-CH3C6H4 for 2a, 2b; 4-CH3OC6H4 for 3a, 3b; 4-ClC6H4 for 4a, 4b; 4-FC6H4 for 5a, 5b; 4-BrC6H4 for 6a, 6b; 2,4-(Cl)2C6H3 for 7a, 7b; 4-NO2C6H4 for 8a, 8b; and C4H3S(2-yl) i. e., 2-thienyl for 9a, 9b. Piperidinol compounds 2b, 3b, 4b, 5b, 7b, 8b, and 9b are reported here for the first time. The synthesized compounds were tested against seven types of plant pathogenic fungi and three types of human pathogenic fungi using the agar dilution assay. Itraconazole was tested against Candida parapsilosis as the reference compound, while Nystatin was tested as the reference compound against the other fungi. Compounds 1a, 1b, 2a, 4a, 4b, 5a, 5b, 6a, 7a, 8a, 9a, and 9b can be selected as model compounds to develop new antifungal agents against the human pathogen Microsporum canis. Compounds 8a and 8b, which had a similar antifungal activity compared with the reference compound Nystatin against the plant pathogen Aspergillus flavus, can serve as model compounds to develop new antifungal agents to solve agricultural problems. [source] The complete chirospectroscopic signature of the peptide 310 -helix in aqueous solutionBIOPOLYMERS, Issue 1 2004Claudio Toniolo Abstract We synthesized by solution methods a water-soluble, terminally blocked heptapeptide based on five markedly helicogenic, C, -tetrasubstituted ,-amino acids C, -methyl- L -norvalines and two strongly hydrophilic 2-amino-3-[1-(1,4,7-triazacyclononane)]- L -propanoic acid residues at positions 2 and 5. A Fourier transform infrared absorption and NMR analysis in deuterated chloroform and aqueous solutions of the heptapeptide and two side-chain protected synthetic precursors confirmed our working hypothesis that all oligomers are folded in the 310 -helical conformation. Based on these findings, we exploited this heptapeptide as a chiral reference compound for detailed electronic CD, vibrational CD, and Raman optical activity characterizations of the 310 -helix in aqueous solution. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004 [source] Transplacental transfer of citalopram, fluoxetine and their primary demethylated metabolites in isolated perfused human placentaBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 9 2002Tuija Heikkinen Objective To investigate the transplacental transfer and the effects of protein binding on the transfer of citalopram, desmethylcitalopram, fluoxetine and desmethylfluoxetine in the isolated perfused human placenta model. Design Prospective observational study. Methods Fifteen term human placentas were obtained immediately after delivery with maternal consent and a 2-hour non-recirculating perfusion cycle of a single placental cotyledon was set up. Citalopram (1230 nmol/L) and desmethylcitalopram (600 nmol/L) or fluoxetine (1455 nmol/L) and desmethylfluoxetine (1525 nmol/L) were added to the maternal reservoir and their appearance to the fetal circulation was followed by repeated measurements. To investigate the effect of protein binding on the transfer of citalopram and fluoxetine, nine additional perfusions were performed without albumin in the perfusion medium. Citalopram and desmethylcitalopram concentrations were measured by reversed-phase high performance liquid chromatography. Fluoxetine and desmethylfluoxetine concentrations was measured by gas chromatography and antipyrine (used as a reference compound) concentrations spectrophotometrically. Results The mean (SD) steady-state transplacental transfer (TPTSS%) for citalopram, desmethylcitalopram, fluoxetine and desmethylfluoxetine was 9.1%, 5.6% (P= 0.017 compared with citalopram), 8.7% and 9.1%, respectively, calculated as the ratio between the steady-state concentrations in fetal venous and maternal arterial sides. The TPTSS%s of citalopram, desmethylcitalopram, fluoxetine and desmethylfluoxetine were 86%, 50%, 88% and 91% of that of freely diffusable antipyrine. The absence of albumin significantly reduced the transfer of citalopram and fluoxetine (TPTSS% 1.1% and 4.8%, respectively) but not the transfer of antipyrine. Conclusion Citalopram, fluoxetine and desmethylfluoxetine all cross the human placenta, and may, therefore, affect the perinatal outcome of infants exposed to these drugs during pregnancy. The transfer of desmethylcitalopram was significantly lower, which in the clinical setting may suggest lower fetal exposure of serotonin re-uptake inhibition by citalopram compared with fluoxetine. The presence of albumin was necessary for the transplacental transfer of both citalopram and fluoxetine. [source] The transplacental transfer of the macrolide antibiotics erythromycin, roxithromycin and azithromycinBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 6 2000Gynaecology), Tuija Heikkinen Consultant (Obstetrics Objective To investigate the transplacental transfer of the macrolide antibiotics erythromycin, roxithromycin and azithromycin. Methods Twenty-one term placentas were obtained with maternal consent immediately after delivery and a two-hour nonrecirculating perfusion of a single placental cotyledon was performed. Erythromycin (2 ,g/mL), roxithromycin (2 ,g/mL) and azithromycin (0.3 ,g/mL) were infused to the maternal inflow at a constant rate, with antipyrine as a reference compound, and their appearance in the fetal circulation was followed. Drug concentrations were measured by high performance liquid chromatography for 120 min. Results The mean transplacental transfers (TPTss) for erythromycin, roxithromycin and azithromycin were 3.0%, 4.3% and 2.6%, respectively, calculated as the ratio between the steady state concentrations in fetal venous and maternal arterial sides. Similar results were obtained when the TPT was calculated as the absolute amount of drug transferred across the placenta during 2-hour perfusion (TPTA). No significant differences were found among the three macrolides in TPTSS (P= 0.39) or TPTA (P= 0.35). The TPTSS of erythromycin, roxithromycin and azithromycin were 41%, 35% and 32% of the freely diffusable reference compound antipyrine, respectively. Steady state was reached in 60 minutes in each perfusion indicating sufficient perfusion time. Conclusion The limited transplacental transfer of erythromycin, roxithromycin and azithromycin suggests compromised efficacy in the treatment of fetal infections. On the other hand, the placenta seems to produce an effective barrier reducing the fetal exposure when these three macrolides are used to treat maternal infections. [source] Tuning the Magnetic Moment of [Ru2(DPhF)3(O2CMe)L]+ Complexes (DPhF=N,N, -Diphenylformamidinate): A Theoretical Explanation of the Axial Ligand InfluenceCHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2010Carmen Barral Dr. Abstract The magnetic behaviour of the compounds containing the [Ru2(DPhF)3(O2CMe)]+ ion (DPhF,=N,N, -diphenylformamidinate) shows a strong dependence on the nature of the ligand bonded to the axial position. The new complexes [Ru2(DPhF)3(O2CMe)(OPMe3)][BF4],0.5,CH2Cl2 (1, 0.5,CH2Cl2) and [Ru2(DPhF)3(O2CMe)(4-pic)][BF4] (2) (4-pic=4-methylpyridine) clearly display this influence. Complex 1,0.5,CH2Cl2 shows a magnetic moment corresponding to a S=3/2 system affected by the common zero-field splitting (ZFS) and a weak antiferromagnetic interaction, whereas complex 2 displays an intermediate behaviour between S=3/2 and S=1/2 systems. The experimental data of complex 1 are fitted with a model that considers the ZFS effect using the Hamiltonian ,D=S,D,S. The weak antiferromagnetic coupling is introduced as a perturbation, using the molecular field approximation. DFT calculations demonstrate that, in the [Ru2(O2CMe)(DPhF)3(L)]+ complexes, the energy level of the metal,metal molecular orbitals is strongly dependent on the nature of the axial ligand (L). This study reveals that the increase in the ,-acceptor character of L leads to a greater split between the ,* and ,* HOMO orbitals. The influence of the axial ligand in the relative energy between the doublet and quartet states in this type of complexes was also analysed. This study was performed on the new complexes 1,0.5,CH2Cl2 and 2. The previously isolated [Ru2(DPhF)3(O2CMe)(OH2)][BF4],0.5,CH2Cl2 (3, 0.5,CH2Cl2) and [Ru2(DPhF)3(O2CMe)(CO)][BF4],CH2Cl2 (4,CH2Cl2) complexes were also included in this study as representative examples of spin-admixed and low-spin configurations, respectively. The [Ru2(DPhF)3(O2CMe)]+ (5) unit was used as a reference compound. These theoretical studies are in accordance with the different magnetic behaviour experimentally observed. [source] Studies on Properties of p -Nitrophenylazo Calix[4]arene DerivativesCHINESE JOURNAL OF CHEMISTRY, Issue 2 2003Jin Chuan-Ming Abstract The p -nitrophenylazo calix[4]arene derivatives 1a-1d with nonlinear optical (NLO) properties were prepared by the diazo-coupling reaction of calix[4]arene with p -nitrophenyl diazonium. The diazotization reaction of p -nitroaniline was carried out with isoamyl nitrite as a source of nitrous add in EtONa/EtOH under refluxing condition. X-Ray crystallographic analysis and 1H NMR spectra reveal that they exist as cone conformation in crystal state or in solution. HRS measurements at 1064 nm in THF indicate that p -nitro-phenylazo calix[4]arenes have higher hyperpolarizability ,z values than the corresponding reference compound 4-(4-nitrophenylazo)-2, 6-dimethyl-phenol, without red shift of the charge transfer band. The tetrakis p -nitrophenylazo calix[4]arene (2) with longer alkyl chains can form monolayer at the air/water interface. [source] Urtica dioica agglutinin: Separation, identification, and quantitation of individual isolectins by capillary electrophoresis and capillary electrophoresis,mass spectrometryELECTROPHORESIS, Issue 9 2005Markus Ganzera Abstract With benign prostatic hyperplasia (BPH) being a major health problem in ageing men, alternative therapeutic approaches (e.g., with phytopharmaceuticals) are of great interest. Based on pharmacological evidences, one of the most promising options in that respect are the lectins found in Urtica dioica (stinging nettle) roots. In this study the qualitative and quantitative analysis of individual isolectins in U. dioica extracts is described, which is the first report on using capillary electrophoresis (CE) for the analysis of lectins in plant material at all. By utilizing a 200 mM sodium acetate buffer (pH 3.75) a baseline separation and determination of four closely related isolectins was feasible within 20 min in the aqueous plant extracts. The individual compounds were identified based on reference compounds as well as data obtained from CE-mass spectrometry (MS) experiments. After modifying the optimized CE conditions to 100 mM ammonium formate buffer with pH 3.75 and a voltage of 15 kV, the isolectins were clearly assignable in positive electrospray ionization (ESI) mode. The quantitative results obtained by CE (the total lectin content varied from 0 to 0.42% in the samples) were accurate (recovery rates of spiked samples between 92.5 and 96.2%), precise (relative standard deviation < 5%) and in good agreement to those obtained by High-performance liquid chromatography (HPLC). As for peak resolution, assignable compounds and required separation time the newly developed CE method was clearly advantageous over the determination achieved by LC. [source] Vapor pressures and enthalpies of sublimation of 17 polychlorinated dibenzo- p -dioxins and five polychlorinated dibenzofuransENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2004Xian-Wei Li Abstract An apparatus for vapor pressure measurement with a very small cell by the mass-loss Knudsen effusion technique was tested with solid benzoic acid and anthracene. The vapor pressure and enthalpy of sublimation results of the two reference compounds were in good agreement with accepted literature data. The vapor pressures at different temperatures of 17 polychlorinated dibenzo- p -dioxins (including dibenzo- p -dioxin) and five polychlorinated dibenzofurans (including dibenzofuran) were measured with the apparatus, and the enthalpies of sublimation of the 22 dioxins and furans were derived from the temperature dependence of vapor pressure. The results were systematically compared with the literature data. [source] Magneto,Structural Correlations in Discrete MnII -WV Cyano-Bridged Assemblies with Polyimine LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2010Robert Podgajny Abstract We present the magneto,structural correlations for two novel discrete cyano-bridged assemblies based on cationic complexes of manganese(II) with diimine ligands and octacyanotungstate(V) ions. The crystal structure of [MnII(terpy)(dmf)(H2O)2][MnII(terpy)(H2O)(dmf)(,-NC)WV(CN)7]2·6H2O (1) (terpy = 2,2,;6,,2,-terpyridine, dmf = dimethylformamide) contains dinuclear {MnIIWV}, cyano-bridged anions, while the crystal structure of [MnII(phen)3]2[MnII(phen)2(,-NC)2WV(CN)6]2(ClO4)2·9H2O (2) (phen = 1,10-phenanthroline) is built of tetranuclear {MnII2WV2}2, square anions. Intramolecular Mn,W magnetic interactions through the cyano bridges are represented by magnetic coupling constants J = ,39 cm,1 for the {MnIIWV}, unit in 1 and J1 = ,25.7 and J2 = ,16.7 cm,1 for the {MnII2WV2}2, unit in 2. J and J1 represent relatively strong W,CN,Mn interactions and are ascribed to the bridges in b positions of TPRS-8 (trigonal prism square-face bicapped) of [W(CN)8]3, polyhedra, favoring the strongest electronic interactions between the d,d orbital of W and the ,* orbitals of CN,, whereas J2 is related to the m vertex of [W(CN)8]3,. The magnetic properties of 1 and 2 are compared with reference compounds and discussed in the context of the type of coordination polyhedra of [W(CN)8]3, as well as the metric parameters of cyano-bridged W,CN,Mn linkages. We found the type of coordination polyhedra and bridging mode of [W(CN)8]3, to be the most important factors influencing the magnitude of the Mn,W magnetic interaction. [source] Synthesis of Polyamines from Ethylenediamine and Their Platinum(II) Complexes, Potential Antitumor AgentsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2006Mara Rubia Costa Couri Abstract This work describes the synthesis and characterization of five new amine ligands and also the preparation and characterization of their respective platinum(II) complexes by reaction with K2PtCl4 in water. These ligands were obtained by treatment of different halides or epoxides with ethylenediamine. Cytotoxic activity and cellular accumulation of three complexes were investigated in a human small-cell lung carcinoma cell line and its cisplatin resistant subline. The introduction of a spacer (cycle) between the two platinum atoms leads to a significant decrease in cytotoxic activity. At equitoxic doses, the intracellular platinum concentrations found for compounds 12 and 15 were significantly higher than those found for the reference compounds, cisplatin, carboplatin, or compound 9. This fact suggests that the formation of adducts between compounds 12 and 15 and the putative pharmacological target, DNA, is less favored. If these compounds bind more slowly to DNA, interaction with other intracellular ligands such as sulfur-containing molecules will become relevant and it may be the reason for the elevated intracellular platinum concentrations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Close Proximity Dibenzo[a,c]phenazine,Fullerene Dyad: Synthesis and Photoinduced Singlet Energy TransferEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2010Rajeev K. Dubey Abstract A dibenzo[a,c]phenazine,fullerene (DBPZ-C60) dyad in which two chromophores are linked in close proximity to each other has been synthesized and studied in detail by optical spectroscopy to explore a new energy donor,acceptor system. The dyad was prepared by Prato reaction between 11-formyldibenzo[a,c]phenazine and fullerene. 3,5-Di- tert -butylbenzyl group was introduced onto the fulleropyrrolidine unit to achieve adequate solubility of the dyad. A thorough study of the photophysical properties of the dyad and relevant reference compounds, performed by means of steady state and time resolved spectroscopic measurements, has revealed the presence of highly efficient (ca. 98,%) and extremely fast (ken = 5,×,1011 s,1) intramolecular photoinduced singlet,singlet energy-transfer process from singlet excited state of the DBPZ moiety to fullerene. In both polar and nonpolar environment transduction of singlet excited state energy governs the excited state deactivation, but the efficiency and rate of energy transfer were found to be higher in nonpolar solvents in comparison to polar. The DBPZ singlet excited state decays within 2 and 4.7 ps in toluene andbenzonitrile, respectively, via singlet,singlet energy transfer to produce a fullerene singlet excited state which decays with a life time of 1.5 ns to give a very long-lived fullerene triplet state as final populated excited state. [source] A Novel Bis(zinc,porphyrin),Oxoporphyrinogen Donor,Acceptor Triad: Synthesis, Electrochemical, Computational and Photochemical StudiesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2006Jonathan P. Hill Abstract The first example of a porphyrin-quinonoid donor,acceptor triad featuring (tetraphenylporphinato)zinc(II) moieties covalently attached to an oxoporphyrinogen through its macrocyclic nitrogen atoms is reported. This arrangement of chromophores results in an interesting interplay between the electron-donating zinc,porphyrin(s) and the electron/energy accepting oxoporphyrinogen. The optical absorption of the triad reveals features corresponding to both the donor and acceptor entities. The geometry and electronic structure of the triad deduced from B3LYP/3-21G(*) calculations reveal an absence of inter-chromophoric interactions and localization of the HOMO on one zinc,porphyrin group and the LUMO on the oxoporphyrinogen scaffold. The electrochemical redox states of the triad were established from a comparative electrochemistry of the triad and the reference compounds. Both steady-state and time-resolved emission studies revealed quenching of the singlet excited state of zinc,porphyrin in the triad, and the free-energy calculations performed using Weller's approach indicate the possibility of electron transfer from the singlet excited zinc,porphyrin group to the oxoporphyrinogen in polar solvents. Time-resolved fluorescence studies reveal excited state energy transfer from zinc,porphyrin to oxoporphyrinogen in nonpolar solvents, while nanosecond transient absorption studies combined with time-resolved fluorescence studies in polar solvents are indicative of the occurrence of photoinduced charge separation from the singlet excited zinc,porphyrin to the oxoporphyrinogen. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Hydrogen Bonding of Fluorinated Saccharides in Solution: F Acting as H-Bond Acceptor in a Bifurcated H-Bond of 4-Fluorinated Levoglucosans,HELVETICA CHIMICA ACTA, Issue 10 2007Bruno Bernet Abstract 4-Fluorinated levoglucosans were synthesised to test if OH,,,F H-bonds are feasible even when the O,,,F distance is increased. The fluorinated 1,6-anhydro- , - D -glucopyranoses were synthesised from 1,6,:,3,4-dianhydro- , - D -galactopyranose (8). Treatment of 8 with KHF2 and KF gave 43% of 4-deoxy-4-fluorolevoglucosan (9), which was transformed into the 3- O -protected derivatives 13 by silylation and 15 by silylation, acetylation, and desilylation. 4-Deoxy-4-methyllevoglucosan (19) and 4-deoxylevoglucosan (21) were prepared as reference compounds that can only form a bivalent H-bond from HOC(2) to OC(5). They were synthesised from the iPr3Si-protected derivative of 8. Intramolecular bifurcated H-bonds from HOC(2) to FC(4) and OC(5) of the 4-fluorinated levoglucosans in CDCl3 solution are evidenced by the 1H-NMR scalar couplings h1J(F,OH) and 3J(H,OH). The OH,,,F H-bond over an O,,,F distance of ca. 3.0,Å is thus formed in apolar solvents, at least when favoured by the simultaneous formation of an OH,,,O H-bond. [source] Kinetics and mechanisms of OH-initiated oxidation of small unsaturated alcoholsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2010Kenshi Takahashi Smog chamber relative rate techniques were used to measure rate coefficients of (5.00 ± 0.54) × 10,11, (5.87 ± 0.63) × 10,11, and (6.49 ± 0.82) × 10,11 cm3 molecule,1 s,1 in 700 Torr air at 296 ± 1 K for reactions of OH radicals with allyl alcohol, 1-buten-3-ol, and 2-methyl-3-buten-2-ol, respectively; the quoted uncertainties encompass the extremes of determinations using two different reference compounds. The OH-initiated oxidation of allyl alcohol in the presence of NOx gives glycolaldehyde in a molar yield of 0.85 ± 0.08; the quoted uncertainty is two standard deviations. Oxidation of 2-methyl-3-buten-2-ol gives acetone and glycolaldehyde in molar yields of 0.66 ± 0.06 and 0.56 ± 0.05, respectively. The reaction of OH radicals with allyl alcohol, 1-buten-3-ol, and 2-methyl-3-buten-2-ol proceeds predominately via addition to the >CCH2 double bond with most of the addition occurring to the terminal carbon. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 151,158, 2010 [source] Rate coefficients for the gas-phase reactions of OH radicals with methylbutenols at 298 KINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2004Takashi Imamura The relative-rate method has been used to determine the rate coefficients for the reactions of OH radicals with three C5 biogenic alcohols, 2-methyl-3-buten-2-ol (k1), 3-methyl-3-buten-1-ol (k2), and 3-methyl-2-buten-1-ol (k3), in the gas phase. OH radicals were produced by the photolysis of CH3ONO in the presence of NO. Di- n -butyl ether and propene were used as the reference compounds. The absolute rate coefficients obtained with the two reference compounds agreed well with each other. The O3 and O-atom reactions with the target alcohols were confirmed to have a negligible contribution to their total losses by using two kinds of light sources with different relative rates of CH3ONO and NO2 photolysis. The absolute rate coefficients were obtained as the weighted mean values for the two reference compound systems and were k1 = (6.6 ± 0.5) × 10,11, k2 = (9.7 ± 0.7) × 10,11, and k3 = (1.5 ± 0.1) × 10,10 cm3 molecule,1 s,1 at 298 ± 2 K and 760 torr of air. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 379,385 2004 [source] Kinetics for the gas-phase reactions of OH radicals with the hydrofluoroethers CH2FCF2OCHF2, CHF2CF2OCH2CF3, CF3CHFCF2OCH2CF3, and CF3CHFCF2OCH2CF2CHF2 at 268,308 KINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 6 2003L. Chen Rate constants were determined for the reactions of OH radicals with the hydrofluoroethers (HFEs) CH2FCF2OCHF2(k1), CHF2CF2OCH2CF3 (k2), CF3CHFCF2OCH2CF3(k3), and CF3CHFCF2OCH2CF2CHF2(k4) by using a relative rate method. OH radicals were prepared by photolysis of ozone at UV wavelengths (>260 nm) in 100 Torr of a HFE,reference,H2O,O3,O2,He gas mixture in a 1-m3 temperature-controlled chamber. By using CH4, CH3CCl3, CHF2Cl, and CF3CF2CF2OCH3 as the reference compounds, reaction rate constants of OH radicals of k1 = (1.68) × 10,12 exp[(,1710 ± 140)/T], k2 = (1.36) × 10,12 exp[(,1470 ± 90)/T], k3 = (1.67) × 10,12 exp[(,1560 ± 140)/T], and k4 = (2.39) × 10,12 exp[(,1560 ± 110)/T] cm3 molecule,1 s,1 were obtained at 268,308 K. The errors reported are ± 2 SD, and represent precision only. We estimate that the potential systematic errors associated with uncertainties in the reference rate constants add a further 10% uncertainty to the values of k1,k4. The results are discussed in relation to the predictions of Atkinson's structure,activity relationship model. The dominant tropospheric loss process for the HFEs studied here is considered to be by the reaction with the OH radicals, with atmospheric lifetimes of 11.5, 5.9, 6.7, and 4.7 years calculated for CH2FCF2OCHF2, CHF2CF2OCH2CF3, CF3CHFCF2OCH2CF3, and CF3CHFCF2OCH2CF2CHF2, respectively, by scaling from the lifetime of CH3CCl3. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 239,245, 2003 [source] Design and preparation of polyphenyl distance markers for solid-state 19F NMRISRAEL JOURNAL OF CHEMISTRY, Issue 3-4 2000Kenji Monde With 13C-labeled samples, it is possible to measure internuclear distances up to 7 Å by solid-state NMR, thus providing a powerful tool for probing ligand,receptor interactions. However, limitations in measurable distances and appreciable natural abundant 13C background signals present problems in solid-state 13C NMR. In order to overcome these disadvantages, a set of reference compounds with known F,F distances, namely, quinolinol, p -biphenyl, and p -terphenyl-bearing trifluoromethyl and trifluoromethylthio groups, have been synthesized. The preparation of these reference compounds and means for diluting these references in solid-state NMR are described. [source] | |||||||||||||||||||||||||||||||||||||