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Selected AbstractsComparison of DNA-Reactive Metabolites from Nitrosamine and Styrene Using Voltammetric DNA/Microsomes SensorsELECTROANALYSIS, Issue 9 2009Sadagopan Krishnan Abstract Voltammetric sensors made with films of polyions, double-stranded DNA and liver microsomes adsorbed layer-by-layer onto pyrolytic graphite electrodes were evaluated for reactive metabolite screening. This approach features simple, inexpensive screening without enzyme purification for applications in drug or environmental chemical development. Cytochrome P450 enzymes (CYPs) in the liver microsomes were activated by an NADPH regenerating system or by electrolysis to metabolize model carcinogenic compounds nitrosamine and styrene. Reactive metabolites formed in the films were trapped as adducts with nucleobases on DNA. The DNA damage was detected by square-wave voltammetry (SWV) using Ru(bpy) as a DNA-oxidation catalyst. These sensors showed a larger rate of increase in signal vs. reaction time for a highly toxic nitrosamine than for the moderately toxic styrene due to more rapid reactive metabolite-DNA adduct formation. Results were consistent with reported in vivo TD50 data for the formation of liver tumors in rats. Analogous polyion/ liver microsome films prepared on 500,nm silica nanoparticles (nanoreactors) and reacted with nitrosamine or styrene, provided LC-MS or GC analyses of metabolite formation rates that correlated well with sensor response. [source] The First Anionic Thia-Fries Rearrangements at Ferrocene: Ready Access to Trifluoromethylsulfonyl-Substituted Hydroxyferrocenes and an Extremely High Interannular Stereoinduction between Cyclopentadienyl LigandsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 8 2010Georg Werner Abstract Attempts originally directed towards the generation of ferrocyne (1,2-dehydroferrocene, 4) and ferrocenediyne (1,2,1,,2,-tetradehydroferrocene, 5) by triflate elimination from the respective ferrocenyl triflates led to the discovery of the first anionic thia-Fries rearrangements at a five-membered ring. These reactions take place with remarkable efficiency under very mild reaction conditions and yield the respective trifluoromethylsulfonyl-substituted ferrocenols. Most remarkably, the reaction starting from 1,1,-ferrocenediyl ditriflate (9) adopts an extremely high interannular stereoinduction in that exclusively the meso rearrangement product, meso -2,2,-bis(trifluoromethylsulfonyl)-1,1,-ferrocenediol (16), is formed, the corresponding racemic product 17 is not observed. It is shown that the second anionic thia-Fries rearrangement proceeds at a much larger rate than the first one. The stereochemistry and the high rate of this reaction are explained on the basis of electronic as well as steric considerations. The redox behavior of some of the unprecedented ferrocene derivatives has been characterized by cyclovoltammetry. [source] EFFECTS OF SAMPLING CONDITIONS ON TEMPORAL PERCEPTION OF BITTERNESS IN YERBA MATE (ILEX PARAGUARIENSIS) INFUSIONSJOURNAL OF SENSORY STUDIES, Issue 3 2004AMALIA CALVIŅO ABSTRACT Time-intensity (TI) methodology and a trained panel were used to characterize the perceived bitterness of Yerba mate (YM) Ilex paraguariensis infusions. Two sampling procedures (sip and spit; sip and swallow) and two conditions for residence time in mouth (free or fixed duration of 5 s until spit or swallow) were evaluated. At a fixed duration the maximum bitterness as well as the time to reach it showed a significant YM concentration dependence. No change on bitterness was observed by swallowing or spitting YM infusions except a larger rate of decay of the response (vr) at spit condition. Dynamic bitterness at free sampling time showed that the decision period to spit or swallow the YM infusion approximately duplicated the fixed one of 5 s. [source] Intraindividual, right,left comparison of topical 5-aminolevulinic acid photodynamic therapy vs.JOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 9 20095% imiquimod cream for actinic keratoses on the upper extremities Abstract Backround, Actinic keratoses (AKs) are considered as in situ squamous cell carcinoma. Early and effective treatment is important. Objective, To compare the efficacy, cosmetic outcome and patient preference of 5-aminolevulinic acid photodynamic therapy (ALA-PDT) with that of 5% imiquimod (IMIQ) cream in patients with AKs on the dorsa of hands and forearms. Methods, Subjects received two ALA-PDT treatment sessions and one or two courses of imiquimod (three times per week for 4 weeks each). Treatments were randomly allocated to alternate upper extremities. Assessments included lesion response one and six months after treatment, cosmetic outcome evaluated by the investigators and patients' preference 6 months after treatment. Efficacy end point included the individual AK lesion clearance rate. Results, Thirty patients with 256 lesions were included in the study. At the first follow-up, treatment with ALA-PDT resulted in significantly larger rate of cured lesions relative to 5% IMIQ cream (70.16% vs. 18.26%). At the second follow-up both treatments showed a high rate of cured lesions (65.32% for PDT vs. 55.65% for IMIQ cream). Response rates obtained in grade I lesions were higher for both treatments (71.64% for PDT vs. 72.13% for IMIQ), while treatment with PDT resulted in a significant larger rate of cured grade II lesions (57.89% for PDT vs. 37.03 for IMIQ). Difference in cosmetic outcome was not statistically significant. Results for subject preference favoured ALA-PDT. Conclusions, Our study shows that ALA-PDT and 5% IMIQ cream are both attractive treatment options for upper extremities AKs with comparable efficacy and cosmetic outcomes. Conflicts of interest None declared. [source] The Origin of the Improved Efficiency and Stability of Triphenylamine-Substituted Anthracene Derivatives for OLEDs: A Theoretical Investigation,CHEMPHYSCHEM, Issue 17 2008Bing Yang Dr. Abstract Herein, we describe the molecular electronic structure, optical, and charge-transport properties of anthracene derivatives computationally using density functional theory to understand the factors responsible for the improved efficiency and stability of organic light-emitting diodes (OLEDs) with triphenylamine (TPA)-substituted anthracene derivatives. The high performance of OLEDs with TPA-substituted anthracene is revealed to derive from three original features in comparison with aryl-substituted anthracene derivatives: 1) the HOMO and LUMO are localized separately on TPA and anthracene moieties, respectively, which leads to better stability of the OLEDs due to the more stable cation of TPA under a hole majority-carrier environment; 2) the more balanceable hole and electron transport together with the easier hole injection leads to a larger rate of hole,electron recombination, which corresponds to the higher electroluminescence efficiency; and 3) the increasing reorganization energy for both hole and electron transport and the higher HOMO energy level provide a stable potential well for hole trapping, and then trapped holes induce a built-in electric field to prompt the balance of charge-carrier injection. [source] | ||||||||||