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121.
4-Amino-2-mercaptopyrimidine self-assembled monolayer (AMP SAMs/Au) was prepared on a gold electrode. The AMP SAMs/Au was characterized by using attenuated total reflection-fourier transform infrared (ATR-FTIR) and A.C. Impedance. The electrochemical behavior of brucine on AMP SAMs/Au was studied by cyclic voltammetry (CV) and square wave adsorptive stripping voltammetry (SWASV). The modified electrode showed an excellent electrocatalytic activity for the redox of brucine. The catalytic current increased linearly with the concentration of brucine in the range of 4.0 x 10(-7) to 2.0 x 10(-4) mol l(-1) by square wave voltammetry response. The detection limit was 6.0 x 10(-8) mol l(-1).  相似文献   
122.
A method for 103Pd molecular plating onto the surface of the copper rod is reported. The optimal composition of the plating bath was: palladium chloride 2 g/l, ammonium hydroxide (28%) 150 ml/l, sodium hypophosphite 12 g/l, and ammonium chloride 37 g/l. The whole procedure of 103Pd molecular plating will last 50 minutes at 40 °C. This article provides valuable experience for the preparation of 103Pd seeds.  相似文献   
123.
The replacement of phenylethanethiolate (SC2Ph) ligands on 1.1 nm (core diameter) Au38(SC2Ph)24 monolayer-protected clusters (MPCs) with varied amounts of triphenylphosphine (PPh3) is investigated in methylene chloride. UV-vis spectra suggest that changes in the MPC Au core size occur when large amounts (> 10 equiv moles per cluster) of PPh3 are reacted with Au38(SC2Ph)24. 1H and 31P NMR spectra following the addition of smaller amounts (< 5 equiv moles) of PPh3 indicate that the reaction liberates a AuISC2Ph complex, as opposed to a SC2Ph thiol, disulfide, or anion. A 1H NMR kinetic study shows that the exchange is surprisingly rapid, even faster than exchanges of thiolates with other thiolates, at room temperature and in air. The reaction is slowed when cooled or conducted under Ar. The difference in potentials of the initial one-electron voltammetric reduction and oxidation of Au38(SC2Ph)24 decreases slightly upon reaction with small amounts of PPh3.  相似文献   
124.
Wang J  Pamidi PV 《Talanta》1995,42(3):463-467
Disposable amperometric sensors for hydrazines have been fabricated by a judicious tailoring of the surface of screen-printed electrodes. Strong electrocatalytic action towards the oxidation of hydrazines is achieved by incorporating cobalt phthalocyanine within the carbon inks or by covering the printed surface with a mixed valent ruthenium cyanide coating. The electrocatalytic behavior, sensor optimization and analytical performance are reported. The new sensor strips should facilitate on-site environmental and industrial monitoring of hydrazine compounds.  相似文献   
125.
Heavy metal cations Cd2+, Pb2+, and Hg2+ were added to substitute for Ca2+ in culture media to study their effect on the relationship between CaM and the proliferation of cultured rabbit aortic smooth muscle cells (ASMC). It was found that all the heavy metal cations studied stimulated the proliferation of ASMC in varying degrees, increased the CaM content in cells at late G1 stage and decreased the activity of cAMP PDE. These results suggest that the adverse effect of heavy metals may be related to the pathogenesis of atherosclerosis and hypertensive disease.  相似文献   
126.
Wang HY  Liu LD  Sun Y  Ma L  Li J 《Talanta》2000,52(2):201-209
Use of synchronous first-derivative fluorimetry for determination of gentamycin is described. Gentamycin reacts with acetylacetone and formaldehyde in pH 5.6 HOAc/NaOAc buffer solution to form N-gentamyl-2,6-dimethyl-3,5-diacethyl-1,4-dihydropyridine[I] which is a fluorescent substance. Spectra of [I] and the reagent blank can be separated with synchronous derivative fluorimetry, and gentamycin can be determined directly. The synchronous spectral peaks of [I] and the reagent blank are at 434 and 411 nm, respectively. The first-derivative peak of [I] is at 425 nm. Effects of pH, foreign ions, buffer system, and heating time on the determination of gentamycin have been examined. The linear regression equation of the calibration graph is C=0.0513H-0.0416, with a correlation coefficient of linear regression of 0.9978. C means total potency of gentamycin: U ml(-1); H means peak height in the linear regression equation calibration graph. The linear range for the determination of gentamycin is from 0.00 to 3.00 U ml(-1). Recovery is from 95.06 to 112.0%, R.S.D. of 3.8%. The results determined by the fluorimetric method agreed roughly with those by the microbiological method. The method is simple and has low detection limit.  相似文献   
127.
The cesium enolate of 6-phenyl-alpha-tetralone (CsPAT) has a lambda(max) in THF at about 387 nm, but the variation with concentration is too small for application of singular value decomposition. Proton-transfer studies with several indicators show that CsPAT forms monomer-tetramer mixtures with a tetramerization equilibrium constant, K(1,4) = 2.3 x 10(11) M(-3). The pK of the monomer is 23.39 on a scale where fluorene is assigned 22.9 (per hydrogen). For comparison, the lithium enolate, LiPAT, is also a monomer-tetramer with K(1,4) = 4.7 x 10(10) M(-3) and a monomer pK = 14.22. HMPA in large amounts promotes dissociation to monomer with both enolates. Ion-pair S(N)2 initial rates were measured for CsPAT with several alkyl halides and with methyl tosylate and compared with other rates with LiPAT. In all cases, the enolate monomers are much more reactive than the aggregates. Reaction of CsPAT with alkyl halides is generally C-alkylation but HMPA promotes increasing amounts of O-alkylation. A new indicator, 11-methyl-11H-benzo[b]fluorene, has a pK on the cesium scale of 23.39.  相似文献   
128.
胆汁酸盐对胆红素钙沉淀过程的影响   总被引:1,自引:0,他引:1  
研究了六种人胆汁主要胆汁酸盐对胆红素钙沉淀形成过程的影响。用曲线拟合法处理数据取得热力学及动力学参数。结果表明,六种胆汁酸盐都表现动力学和热力学抑制,而且抑制作用有浓度依赖关系。在一定条件下出现诱导期。虽然不同胆汁酸盐的作用结果相似,但在相同条件下,二羟基胆汁酸和三羟基胆汁酸影响程度不同。  相似文献   
129.
We present a numerically exact calculation of rovibrational levels of a five-atom molecule. Two contracted basis Lanczos strategies are proposed. The first and preferred strategy is a two-stage contraction. Products of eigenfunctions of a four-dimensional (4D) stretch problem and eigenfunctions of 5D bend-rotation problems, one for each K, are used as basis functions for computing eigenfunctions and eigenvalues (for each K) of the Hamiltonian without the Coriolis coupling term, denoted H0. Finally, energy levels of the full Hamiltonian are calculated in a basis of the eigenfunctions of H0. The second strategy is a one-stage contraction in which energy levels of the full Hamiltonian are computed in the product contracted basis (without first computing eigenfunctions of H0). The two-stage contraction strategy, albeit more complicated, has the crucial advantage that it is trivial to parallelize the calculation so that the CPU and memory costs are independent of J. For the one-stage contraction strategy the CPU and memory costs of the difficult part of the calculation scale linearly with J. We use the polar coordinates associated with orthogonal Radau vectors and spherical harmonic type rovibrational basis functions. A parity-adapted rovibrational basis suitable for a five-atom molecule is proposed and employed to obtain bend-rotation eigenfunctions in the first step of both contraction methods. The effectiveness of the two methods is demonstrated by calculating a large number of converged J = 1 rovibrational levels of methane using a global potential energy surface.  相似文献   
130.
To support preclinical pharmacokinetic investigation of 1-[4-[2-(4-bromobenzene-sulfonaminoethyl)phenylsufonyl]-3-(trans-4-methylcyclohexyl)urea (G004), a rapid, sensitive and specific high-performance liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS) method was developed and validated. Glibenclamide was employed as internal standard. After liquid–liquid extraction the analyte was analyzed on a Kromasil C18 column (150 × 2.0 mm i.d.) with a mobile phase consisted of acetonitrile–water (0.05% acetic acid), 30:70 (v/v). The flow rate was 0.2 mL min−1. Detection was performed on a quadrupole mass spectrometer using an electrospray ionization interface and the selected-ion monitoring (SIM) mode. The retention time was about 3.5 and 4.2 min for Glibenclamide and G004, respectively. The assay was linear over the concentration range of 2.0–500.0 ng mL−1. Extraction Recovery of G004 in rat plasma was more than 87%. The intra- and inter-assay precision was lower than 11.5% (CV). This validated method was successfully applied to the pharmacokinetics of G004 in rats.  相似文献   
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