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821.
A novel hypoxanthine (Hx) microsensor was constructed. In this work, Nafion xanthine oxidase (XOD) and Au colloid were immobilized onto the surface of a Pt microelectrode. The enzyme biosensor displayed a quick and sensitive response to Hx. Under physiological conditions, a low detection limit, with high selectivity and sensitivity for Hx determination were obtained. The oxidation current [investigated using current-time (I-t) plots] was linear with Hx concentration ranging from 2.0 x 10(-7) to 2.0 x 10(-5) mol L(-1) with a calculated detection limit of 1.0 x 10(-7) mol L(-1) (S/N of 3). The biosensor should be promising for in vivo measurement of Hx without interferences and fouling. The change of Hx concentration in cardiac myocytes stimulated by L-arginine (L-Arg) and acetylcholine (Ach) was also studied. 相似文献
822.
Trifluoromethylation of alkyl radicals is emerging as a powerful tool for C(sp3)–CF3 bond formations. Based on the hypothesis of CF3 group transfer from Cu(II)–CF3 to alkyl radicals, a number of trifluoromethylation reactions have been developed, including trifluoromethylation of alkyl halides, decarboxylative trifluoromethylation of aliphatic carboxylic acids, C(sp3)–H trifluoromethylation, amino‐ and carbo‐trifluoromethylation of alkenes, etc. Challenges in this intriguing field are also discussed. 相似文献
823.
本文成功地运用了三跳动力学模型,通过相关函数和超精细分裂常数的关系, 推出了电子自旋共振波谱的线宽与基本线宽T_(2,0)~(-1)、溶液中各种异构体的超精细分裂常数、配体的交换寿命等之间的关系。求出了在290 K温度下(Ph_2C_2)Co(CO)[P(OEt)_3]_2的THF溶渡中P(OEt)_3配体的交换寿命是5.6×10~(-11)秒。 相似文献
824.
The influence of polyelectrolyte charges of polyurethane membrane surface on the growth of human endothelial cells 总被引:1,自引:0,他引:1
A novel technique to introduce free amino groups onto polyester scaffolds via aminolyzing the ester groups with diamine has been developed recently. The introduction of the free amino groups on these polyester surfaces provides us the possibility to modify polymer surface in a simpler manner, e.g. layer-by-layer assembly of charged species. By this technique, many negatively and positively charged biopolymers were deposited alternatively on polyurethane surface. The deposition process was monitored by fluorescence spectroscopy and advancing contact angle measurements. The result of human endothelial cells cultured in vitro showed that cells on negatively charged surface could not spread and flatten well due to the electrostatic repulsion. The lower attachment ratio induced the lower proliferation ratio. However, after the surface charge was inversed by collagen, both attachment and proliferation ratios increased to different extent. Observed under SEM, cells also presented a flat and spreading morphology. 相似文献
825.
826.
Dazhang Zhu Shilong Wang Xiaoyu Sun Yaming Ni Side Yao 《Frontiers of Chemistry in China》2007,2(4):354-358
The reaction mechanism between isoquinoline and ·OH radical in aqueous dilute solutions under different conditions was studied
by pulse radiolysis. The main characteristic peaks in these transient absorption spectra were attributed and the growth-decay
trends of several transient species were investigated. Under neutral or alkaline conditions, the reaction of ·OH radical and
isoquinoline produces OH-adducts with respective rate constants of 3.4 × 109 and 6.6 × 109 mol−1 · dm3 · s−1 while under acidic conditions, the isoquinoline was firstly protonated and then ·OH added to the benzene ring and produced
protonated isoquinoline OH-adducts with a rate constant of 3.9 × 109 mol−1 · dm3 · s−1. With a better understanding on radiolysis of isoquinoline, this study is of help for its degradation and for environmental
protection.
__________
Translated from Journal of Fudan University (Natural Science), 2006, 45(6): 774–778 [8BD1;81EA: 590D;65E6;5B66;62A5;(自然科学版)] 相似文献
827.
Treatment of two kinds of ferrocenyl-substituted carboxylate ligands (3-ferrocenyl-2-crotonic acid, HOOC-CH=(CH(3))CFc (Fc=(eta(5)-C(5)H(5))Fe(eta(5)-C(5)H(4))) or O-ferrocecarbonyl benzoic acid, o-HOOCC(6)H(4)COFc with Pb(OAc)(2).3H(2)O, Zn(OAc)(2).2H(2)O, or Cd(OAc)(2).2H(2)O) resulted in four novel ferrocene-containing coordination polymers [[Pb(mu(2)-eta(2)-OOCCH=(CH(3))CFc)(2)].MeOH](n) (1), [[Zn(o-OOCC(6)H(4)COFc)(2)(4,4'-bipy)(H(2)O)(2)].2MeOH.2H(2)O](n) (4,4'-bipy = 4,4'-bipyridine) (2), [[Cd(o-OOCC(6)H(4)COFc)(2)(bpe)(MeOH)(2)].2H(2)O](n) (bpe = 1,2-bis(4-pyridyl)ethene) (3), and [Pb(o-OOCC(6)H(4)COFc)(eta(2)-o-OOCC(6)H(4)COFc)(bpe)](n)() (4). Their crystal structures have been characterized by single X-ray determinations. In polymer 1, Pb(II) ions are bridged by tridentate FcC(CH(3))=CHCOO(-) anions, forming an infinite chain [Pb(mu(2)-eta(2)-OOC=CH(CH(3))CFc)(2)](n). In polymers 2-4, there are three kinds of components, metal ions, o-FcCOC(6)H(4)COO(-) units, and organic bridging ligands. The bipyridine-based ligands connect metal ions leading to a one-dimensional chain with o-FcCOC(6)H(4)COO(-) units acting as monodentate or chelate ligands in the side chain. Such coordination polymers containing ferrocenyl-substituted carboxylate and bipyridine-based ligands are very rare. The solution-state differential pulse voltammetries of polymers 1-4 were determined. The results indicate that the half-wave potential of the ferrocenyl moieties is influenced by the Pb(II) ions in polymer 1 and strongly influenced by Zn(II), Cd(II), or Pb(II) ions in polymers 2-4. The thermal properties of the four polymers were also investigated. 相似文献
828.
Perfluorooctanoyl modified poly(vinyl alcohol)s (FPVA) were prepared by means of substituting a small amountof hydroxyl groups on the backbone of poly(vinyl alcohol), for which the initial degree of polymerization is equal to 1750.The substitution extent, defined by the number of substituting units in a chain, for the four FPVA samples was in the range of0.5-5 perfluorooctanoyl groups per chain. The FPVA samples with the highest substitution extent still had good solubility inwater. It was shown by experimental measurement at 30.0±0.1℃ that the surface tension of the aqueous solution of thehighest substituted FPVA decreased to 16.6 mN/In at a higher concentration, e.g about 0.1 g/mL. Obviously,macromolecules of FPVA exhibit a very strong tendency to adsorb at the air-water interface, because the hydrophobicperfluorooctanoyl groups in FPVA have a very high surface activity as they are in small molecular fluorinated surfactants.The chain conformation of such a model polymer adsorbed on the air-water interface was also discussed. 相似文献
829.
Wang Zhong-Ming Lin Hua-Kuan Zhou Zhi-Fen Zhu Shou-Rong Chen Yun-Ti Murmann R. Kent 《Transition Metal Chemistry》2000,25(5):562-567
The kinetics of the reaction of CH2O with a quasi-aromatic metal complex (1,1,2,8,9,9-hexamethyl-4,6-dioxa-5-hydro-3,7,10,14-tetraazacyclotetradecane-2,7,10,12-tetraene)copper(II), [Cu(PnAO)-6H]0 (AH), have been studied spectrophotometrically under neutral conditions in 1/3(v/v) MeOH–H2O. The Cu, 2N, 3C quasi-aromatic heterocyclic ring in AH is highly reactive towards CH2O at the central-aromatic-carbon atom, C(12) and the following reaction mechanism is proposed.
The compounds AH, A—CH2OH and A—CH2—A were isolated and identified by i.r spectroscopy and by elemental analysis. The kinetic data supported the proposed reaction sequence. All reactions were second order overall. The rate constants and corresponding activation parameters for every step were obtained and are discussed. 相似文献
830.
本文报道了用流动放电-化学发光技术测定O(~3P)和硅烷化学反应速率常数.在293—413K范围内, 结果为k=(1.05±0.36)×10~(-10)exp[(-3.06±0.10) kcal·mol~(-1) /RT] cm~3·molecule~(-1)·s~(-1)并用过渡态理论将上述实验结果外推到200—2000 K范围内. 计算结果以三参数公式表示为: k=7.67×10~(-19) T~(2.59) exp(-720 cal·mol~(-1)/RT) cm~3·molecule~(-1)·s~(-1). 相似文献