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1.
Twelve major anthocyanins identified in bilberry extracts were studied in vitro using capillary zone electrophoresis (CZE) for their reactions towards 2,2'-azobis(2-amidinopropane) (AAPH) radicals, hydrogen peroxides (H(2)O(2)) and tert-buthylhydroperoxides (t-BuOOH). Reactivity towards AAPH radicals was primarily determined by the aglycon structure, not by the type of sugar moiety. Delphinidins carrying three-hydroxyl groups on the B ring were most reactive followed by cyanidins, with two-hydroxyl groups. Further, methylation of the hydroxyl groups reduced reactivity towards AAPH radicals. However, reactivity of anthocyanins towards H(2)O(2) was not significantly affected by aglycon structure or by the type of sugar moiety; there being no marked difference in reaction rates among the anthocyanins. Reactivity towards t-BuOOH was essentially the same as towards H(2)O(2), although the reaction rate was several times smaller. Also, the reaction rate of anthocyanin towards peroxide was relatively high compared to that of (+)-catechin (approximately 30 times larger) measured as a reference antioxidant, whereas the reactivities of anthocyanins and (+)-catechin towards AAPH radicals were similar. 相似文献
2.
Hydrate that is exposed to fluid phases which are undersaturated with respect to equilibrium with the hydrate will dissociate
due to gradients in chemical potential. Kinetic rates of methane hydrate dissociation towards pure water and seawater is important
relative to hydrate reservoirs that are partly exposed towards the ocean floor. Corresponding results for carbon dioxide hydrate
is important relative to hydrate sealing effects related to storage of carbon dioxide in cold aquifers. In this work we apply
a phase field theory to the prediction of carbon dioxide hydrate and methane hydrate dissociation towards pure water at various
conditions, some of which are inside and some which are outside the stability regions of the hydrates with respect to temperature
and pressure. As expected from the differences in water solubility the methane hydrate dissolves significantly slower towards
pure water than carbon dioxide hydrate. 相似文献
3.
Styrene has been copolymerized to high conversions with vinylmethyl diacetoxysilane (VMDAS) and vinylmethyldiethoxysilane (VMDES) in bulk and in toluene at 60 using azobisisobutyronitrile (AIBN) as initiator. Acrylonitrile has also been copolymerized with VMDAS at 50 in bulk using AIBN. The compositions of the copolymers were determined from the silicon contents; reactivity ratios were calculated by the Kelen-Tüdös method. The reactivity ratio r1 (styrene) is higher for styrene-VMDES than for styrene-VMDAS, indicating higher reactivity of VMDAS towards polystyryl radical. VMDAS was found to be more reactive towards the polyacrylonitrile than towards the polystyrene radical. The influences of the silicon comonomer on properties such as intrinsic viscosity, solubility, molecular weight distribution and thermal behaviour were also studied. 相似文献
4.
The probes for metal ion induced chromo- and fluorogenic signalling responses alter their selectivity depending upon the nature of substituent as well as a function of solvent medium. 2 has shown selectivity towards Fe(III) ion, 4 towards Hg(II) ion while 3 is responsive towards both Fe(III) and Hg(II) ions. 相似文献
5.
E. Lukevics D. Zaruma J. Ashaks I. Shestakova I. Domracheva V. Bridane E. Yashchenko 《Chemistry of Heterocyclic Compounds》2009,45(2):182-187
A series of 2-methyl, 4-methyl, and 2,4-dimethyl-8-quinolineselenolates of ruthenium, rhodium, osmium, and iridium has been
synthesized and their cytotoxicity towards HT-1080 (human fibrosarcoma) and MG-22A (mouse hepatoma) tumor cells studied. It
was found that all of the osmium complexes had a high cytotoxicity towards both cell lines. Their toxicity towards the normal
mouse embryonic fibroblasts NIH-3T3 depends on the position and number of methyl groups in the quinoline ring and decreases
in the order 2-Me > 4-Me > 2,4-Me2. The greatest selectivity in cytoxic activity is noted for iridium 4-methyl-8-quinolineselenolate and ruthenium 2-methyl-8-quinolineselenolate.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 230–236, February, 2009. 相似文献
6.
Polydimethylsiloxane-based permeation passive air sampler. Part II: Effect of temperature and humidity on the calibration constants 总被引:1,自引:0,他引:1
Polydimethylsiloxane (PDMS) has low permeability towards water vapour and low energy of activation of permeation towards volatile organic compounds (VOCs) when compared to many other polymers. Suitability of the material for use in permeation-type passive air samplers was tested as it theoretically should reduce uptake rate variations due to temperature changes and eliminate or reduce complications arising from sorbent saturation by water vapour. The calibration constants of a simple autosampler vial-based permeation passive sampler equipped with a PDMS membrane (Waterloo Membrane Sampler®) were determined for various analytes at different temperatures. From the data, the activation energy of permeation for PDMS towards the analytes was determined. The analytes studied belonged to various classes of compounds with wide ranging polarities, including n-alkanes, aromatic hydrocarbons, esters and alcohols. The results confirmed Arrhenius-type relationship between temperature and calibration constant and the energy of activation of permeation for PDMS ranged from −5 kJ/mole for butylbenzene to −17 kJ/mole for sec-butylacetate. Calibration constants of the samplers towards n-alkanes and aromatic hydrocarbons determined at humidities between 30% and 91% indicated no statistically significant variations in the uptake rate with changes in humidity for 9 of the 11 analytes studied. The results confirmed the suitability of the sampler for deployment in high humidity areas and under varying temperature conditions. 相似文献
7.
Ortiz Mellet C Defaye J García Fernández JM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(9):1982-1990
Results obtained over the past decade towards the preparation of multitopic carbohydrate architectures combining the molecular inclusion capabilities of cyclomaltooligosaccharide receptors (cyclodextrins, CDs) and the recognition properties of saccharide ligands towards biological receptors are discussed. The potential of these new sugar-based "intelligent" transporters for site specific delivery of therapeutics is outlined. 相似文献
8.
采用巨正则Monte Carlo(GCMC)方法讨论了不同温度、压力及管径下,碳纳米管对H2S/N2混合物(主体相体积比为1∶99)的吸附分离选择性.结果表明,随着碳纳米管管径的增大,H2S的吸附选择性先增加后减小;而(11,0)碳纳米管(管径为0.86 nm)对H2S的选择性最高,这种选择性与管径的关系是由几何效应和能量效应共同决定的.针对(11,0)碳纳米管讨论了温度和压力对H2S吸附量和选择性的影响.模拟结果表明,随着温度上升,H2S的吸附量和选择性都呈先增加后减小的趋势;随着压力增加,H2S的吸附量和选择性都有所下降.本文模拟结果可为含硫气体混合物的吸附分离提供一定参考. 相似文献
9.
Synthetic polymers for capture and detection of microorganisms 总被引:1,自引:0,他引:1
Methods for the detection of pathogens and their deactivation are of paramount importance for public health and security. In this review we highlight some recent examples of sophisticated synthetic polymers and macromolecular constructs that can be used to interact selectively with target pathogens. The biomimetic properties of these materials lend themselves not just to high specificity interactions with target pathogens, but also towards novel capture and deactivation mechanisms. These are the first steps towards combined diagnostics/therapeutics against pathogens. 相似文献
10.
《Journal of organometallic chemistry》2006,691(1-2):9-19
Simple organometallic cluster analogues of tamoxifen containing triosmium or dicobalt carbonyl fragments have been prepared. Attempts at elaboration of these towards the tamoxifen skeleton were hampered by sensitivity of the cluster–ligand linkage towards the McMurry coupling conditions. Preliminary biological tests on various substrates indicate that the transition metal carbonyl fragment increases lipophilicity dramatically and reduces affinity for the estrogen receptor. 相似文献
11.
FaFuYANG HongYuGUO JianRongLIN YuanYinCHEN 《中国化学快报》2003,14(5):453-455
Reacting calix[6]arene hexaesters with poly(ethyleneimine),a series of calix[6]amidesbased polymers were obtained for the first time.It is found that they show high absorption capacities towards soft cations comparing to hard cations,and the absorption abilities enhanced with the increasing of calixarene content,which may indicates the cavity of calixarene plays crucial role in absorption.Polymer 2c shows good selective absorption capability towards Ag^ among the tested cations. 相似文献
12.
A concise, two-step eco-friendly approach towards the synthesis of 5-sulfenyl tetrazole derivatives of indoles and pyrroles, is reported. The synthesis comprises the oxone-mediated thiocyanation of the starting heterocycles towards intermediate 3-thiocyanato indoles and 2-thiocyanato pyrroles, and their subsequent treatment with sodium azide in 2-propanol/water under zinc bromide promotion. 相似文献
13.
14.
D. M. Cox R. Brickman K. Creegan A. Kaldor 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,19(4):353-355
We have examined the reactivity and saturation of small gold clusters (cations, neutrals and anions) towards several molecules and find that specific small gold clusters exhibit a pronounced variation in their reactivity towards hydrogen, methane and oxygen. The reactivity not only depends strongly on cluster size but also on the cluster charge state. For example, small (n<15) gold cations react readily with D2, but no evidence of reaction is observed for the anions under our experimental conditions. Similar behavior is seen for methane. With oxygen only even atom (odd electron) anions are reactive, and Au 10 + is the only cation which exhibits evidence of reaction. The global features (small cluster cations reactive towards H2, CH4, but large ones not reactive, odd electron anions reactive towards O2) are qualitatively explained by appealing to a simple frontier orbital picture. The uptake of deuterium and methane on gold clusters also exhibits a pronounced size dependence with D/Au varying from a high of 3 for the dimer to zero for clusters containing more than 15 Au atoms. Comparison of the methane and deuterium saturation behavior leads us to suggest that methane is dissociated and bound as CH3 and H. 相似文献
15.
Siegfried Bsler Annette Brunck Rolf Jautelat Ekkehard Winterfeldt 《Helvetica chimica acta》2000,83(8):1854-1880
Aiming towards spiroketal‐modified artificial cephalostatin molecules, two orthogonal approaches were investigated. First, the introduction of 17‐O‐functionality into hecogenin derivatives with a closed spiroketal moiety was accomplished by different remote‐oxidation procedures. These allowed the synthesis of tetradecacyclic artificial cephalostatin molecules with improved tumor‐inhibiting properties. Second, a novel reduction‐oxidation pathway for spiroketal opening in sapogenins was discovered, which should provide the basis for a broad access towards spiroketal‐modified building blocks for cephalostatins. 相似文献
16.
《Journal of Energy Chemistry》2017,26(6):1153-1159
Designing the low cost, active, durable, and alcohol-tolerant cathode catalysts towards the oxygen reduction reaction(ORR) is significant for the large-scale commercialization of direct alcohol fuel cells.Recently, Pd-based nanocrystals have attracted attention as Pt-alternative cathode catalysts towards the ORR in the alkaline electrolyte. Unfortunately, the pristine Pd-based nanocrystals lack the selectivity towards the ORR due to their inherent activity for the alcohol molecule oxidation reaction in the alkaline electrolyte. In this work, polyethyleneimine(PEI) modified Au Pd alloy nanocrystals with Au-rich Au Pd alloy cores and Pd-rich Pd Au alloy shells(AuPd@PdAu-PEI) are successfully synthesized using a traditional chemical reduction method in presence of PEI. The rotating disk electrode(RDE) technique is applied to evaluate the ORR performance of AuPd@PdAu-PEI nanocrystals. Compared with commercial Pd black,AuPd@PdAu-PEI nanocrystals show significantly enhanced activity and durability towards the ORR, and simultaneously exhibit particular alcohol tolerance towards the ORR in the alkaline electrolyte. 相似文献
17.
Vishal Budhija Phebe H. van Langevelde Konstantin B. Krause Dr. Beatrice Cula Dr. D. G. H. Hetterscheid Dr. Matthias Schwalbe 《欧洲无机化学杂志》2023,26(14):e202200743
Synthesis, characterization and reactivity studies of a hetero-dicopper complex, particularly towards oxygen reduction are presented. A bischlorido copper(II) trishistidine-type coordination unit is positioned directly above a copper porphyrin unit. The close distance between the two coordination fragments is secured by a rigid xanthene backbone. Surprisingly, the dinuclear complex is not active towards oxygen reduction unlike the earlier published mononuclear analogues with a bispyridylamine copper center. However, the compound architecture of this multinuclear metal complex is interesting and can play an important role in the development of new catalysts for ORR. 相似文献
18.
Although lipase from Pseudomonas cepacia (PCL) shows high enantioselectivity towards many secondary alcohols, it usually exhibits only low to moderate enantioselectivity towards primary alcohols. To increase this enantioselectivity, we optimised the reaction conditions for the PCL-catalysed hydrolysis of esters of three chiral primary alcohols: 2-methyl-3-phenyl-1-propanol 1, 2-phenoxy-1-propanol 2 and solketal 3. The enantioselectivity towards 1-acetate increased from E=16 to 38 upon changing the solvent from ethyl ether/phosphate buffer to 30% n-propanol in phosphate buffer and increased again to E ≥190 upon changing the substrate from 1-acetate to 1-heptanoate. The same changes increased the enantioselectivity towards alcohol 2 from E=17 to 70, but did not significantly increase the enantioselectivity towards alcohol 3. The best solvent was similar to the solvent used to crystallise the open form of PCL and likely stabilises the open form of PCL. This stabilisation may increase the enantioselectivity by removing kinetic contributions from a non-enantioselective lid-opening step. We determined the kinetic contribution of the lid-opening step by measuring the interfacial activation of PCL. The activation energy for the PCL-catalysed hydrolysis of ethyl acetate was at least 2.6 kcal/mol lower in the presence of a water–organic solvent interface. 相似文献
19.
Ritesh Gautam Ian Geniza Scott T. Iacono Chadron M. Friesen Abby R. Jennings 《Molecules (Basel, Switzerland)》2022,27(5)
Perfluoropyridine (PFPy) is an organofluorine compound that has been employed for a variety of applications, from straightforward chemical synthesis to more advanced functions, such as fluorinated networks and polymers. This can be directly attributed to the highly reactive nature of PFPy, especially towards nucleophilic aromatic substitution (SNAr). The aim of this review is to highlight the discovery and synthesis of PFPy, discuss its reactive nature towards SNAr, and to summarize known reports of the utilization and thermal analysis of PFPy containing fluoropolymers and fluorinated network materials. 相似文献
20.
Raphael I Ngochindo 《Journal of Chemical Sciences》1992,104(3):377-382
Benzaldehyde is shown to be a more suitable electrophile than carbon dioxide in reactions involving the lithio derivatives
of 2-(N-methylpyrrol-2-yl) oxazolines. The relative reactivities of the C3-Li and C5-Li bonds in ethereal solvents are examined.
The 2-oxazolino group at a 2-position in N-substituted pyrrole is shown to possess an activating effect on the 5-position
towards lithiation, and eliminates the propensity of the pyrrole nucleus towards polymerisation. The conditions for removal
of the 2-protecting group are explored. 相似文献