Subnanometer-Sized Copper Clusters: A Critical Re-evaluation of the Synthesis and Characterization of Cu8(MPP)4 (HMPP = 2-Mercapto-5-n-propylpyrimidine)
摘要:
We report a critical re-evaluation of the synthesis and characterization of Cu-8(MPP)(4). This product was reportedly formed by the reaction of Cu(NO3)(2) with 2-mercapto-5-n-propylpyrimidine (HMPP) and NaBH4, in ethanol, in the presence of [N(C8H17)(4)][Br]. In our hands, we found no experimental evidence to support the existence of Cu-8(MPP)(4) in the reaction mixture. Instead, we demonstrate that the material isolated from this reaction is a complex mixture containing [N(C8H17)(4)](+), Br-, NO3-, and 2-mercapto-5-n-propyl-1,6-dihydropyrimidine (H2MPP*), along with the Cu(I) coordination polymer, [Cu(MPP)](n). To support our conclusions, we have independently synthesized H2MPP* and [Cu(MPP)](n), as well as the related Cu(I) coordination complexes, [Cu(HMPP*)]n and [Cu-2(MPP*)](n). All new materials were characterized by NMR spectroscopy and mass spectrometry, while H2MPP*, [Cu(HMPP*)](n) (n = 4), and [Cu(MPP)](n) (n = 6) were also characterized by X-ray crystallography.
Determinants of Body Composition in Postmenopausal Women
摘要:
Background. Little is known about the effects of different levels of long-term physical activity on total body and regional fat and whether hormone replacement therapy interacts with physical activity level to affect body composition in postmenopausal women.Methods. We determined the associations between different levels of habitual physical activity, hormone replacement therapy (HRT), and total and regional body composition in postmenopausal women. Twenty sedentary, 20 active nonathletic, and 23 endurance-trained women (approximately half on HRT) had total and regional body composition assessed by dual-energy x-ray absorptiometry. The athletes and active nonathletic women had been active for the same number of years and the same number of hours per week.Results, The athletes and sedentary women weighed the same, but the active nonathletic groups on and not on HRT weighed 3-12 kg more (p < .05). Athletes had less trunk, arm, leg, and total body fat than sedentary and active nonathletic women (p < .05). Women on HRT tended to have lower total body (p = .07), but not regional, fat values. Linear regression analyses indicated that (V) over dot O-2 max in ml/kg/min was the major independent determinant of total and regional; body fat accounting for 52% to 70% of their variances. Athletes had greater caloric and carbohydrate intake than their less active peers, but all groups had similar protein, fat, saturated fat, monounsaturated fat, and polyunsaturated fat intakes.Conclusions. Intense training, but not low- to moderate-intensity physical activity, is associated with markedly lower levels of total and regional body fat in postmenopausal women. HRT has less of an effect on body composition than intense exercise training in postmenopausal women.
Synthesis of disulfides by laccase-catalyzed oxidative coupling of heterocyclic thiols
作者:Heba T. Abdel-Mohsen、Kavitha Sudheendran、Jürgen Conrad、Uwe Beifuss
DOI:10.1039/c3gc40106e
日期:——
A new method employing a laccase–mediator system as the catalyst and aerial oxygen as the oxidant has been developed for the oxidative coupling of heterocyclic thiols to the corresponding disulfides with yields up to 95% under mild reaction conditions.
Synthesis and antibacterial activity of novel ketolides with 11,12-sulfur contained aryl alkyl side chains
作者:Xiao-zhuo Chen、Peng Xu、Lu Liu、Dan Zheng、Ping-sheng Lei
DOI:10.1016/j.ejmech.2010.11.004
日期:2011.1
A novel series of ketolides with 11,12-sulfur contained aryl alkyl side chains were synthesized and evaluated for their antibacterial activity. These ketolides exhibited potent activity against key macrolide sensitive and resistant respiratory pathogens. The newly synthesized 9a, 9e, 9k and 9n showed a similar antimicrobial spectrum and comparable activity to telithromycin, the commercial ketolide antibacterial. (C) 2010 Elsevier Masson SAS. All rights reserved.
Benzenesulfonamides with pyrimidine moiety as inhibitors of human carbonic anhydrases I, II, VI, VII, XII, and XIII
Two groups of benzenesulfonamide derivatives, bearing pyrimidine moieties, were designed and synthesized as inhibitors of carbonic anhydrases (CA). Their binding affinities to six recombinant human CA isoforms I, II, VI, VII, XII, and XIII were determined by the thermal shift assay (TSA). The binding of several inhibitors was measured by isothermal titration calorimetry (ITC). Direct demonstration of compound inhibition was achieved by determining the inhibition constant by stopped-flow CO2 hydration assay. The most potent compounds demonstrated selectivity towards isoform I and affinities of 0.5 nM. The crystal structures of selected compounds in complex with CA II, XII, and XIII were determined to atomic resolution. Compounds described here were compared with previously published pyrimidinebenzene-sulfonamides.(1) Systematic structure-activity analysis of 40 compound interactions with six isoforms yields clues for the design of compounds with greater affinities and selectivities towards target CA isoforms. (C) 2013 Elsevier Ltd. All rights reserved.
Design of [(2-pyrimidinylthio)acetyl]benzenesulfonamides as inhibitors of human carbonic anhydrases
A series of [(2-pyrimidinylthio)acetyl]benzenesulfonamides were designed and synthesized. Their binding affinities as inhibitors of several recombinant human carbonic anhydrase (CA) isozymes were determined by isothermal titration calorimetry (ITC) and thermal shift assay (TSA). A group of compounds containing a chlorine atom in the benzenesulfonamide ring were found to exhibit higher selectivity but lower binding affinity toward tested CAs. The crystal structures of selected compounds in complex with CA II were determined to atomic resolution. Docking studies were performed to compare the binding modes of experimentally determined crystallographic structures with computational prediction of the pyrimidine derivative binding to CA II. Several compounds bound to select CAs with single-digit nanomolar affinities and could be used as leads for inhibitor development toward a select CA isozyme. (C) 2012 Elsevier Masson SAS. All rights reserved.
Controlling Cu2ZnSnS4 photocatalytic ability through alterations in sulfur availability
作者:Matthew J. Turnbull、Saghar Khoshmashrab、Zhiqiang Wang、Robert Harbottle、Tsun-Kong Sham、Zhifeng Ding
DOI:10.1016/j.cattod.2015.05.028
日期:2016.2
Cu2ZnSnS4 (CZTS) nanocrystals (NCs) were made via a one-pot solvothermal method with various amounts of available free-sulfur and a fixed amount of sulfur bound to 2-mercapto-5-n-propylpyrimidine (MPP). Varying the sulfur availability yields CZTS NCs of different stoichiometry, from which five distinct samples were analyzed for consistency both microscopically and macroscopically. As revealed by Xray absorption fine structure investigation, samples fabricated in the presence of decreased free-sulfur showed decreased CZTS character, with sporadic compositions and no long term order; however, when fabricated in the presence of no free-sulfur, sulfur from the degraded MPP was found incorporated into the CZTS structure. These NCs showed improved long-term order over standard synthetic procedure. The catalysis of methyl viologen (MV) from MV2+ to MV+ state by CZTS under light irradiation was used as the probe to test the photovoltaic nature. The photocatalysis was enhanced in the films made from NCs fabricated without available free-sulfur. This enhancement is consistent with the measured band gaps, with more ordered NCs showing a band gap that better matches the most intense regions of the solar spectrum. (C) 2015 Elsevier B.V. All rights reserved.