摘要:

AbstractThe kinetic Ising model in the mean field approximation has been applied to study the equilibrium and kinetic behaviors of protein folding‐unfolding. Thermodynamics and kinetics of protein folding‐unfolding are related by an elementary process of folding ↔ unfolding of peptide bonds. As a demonstration, we analyze, using the presented theory, the equilibrium and kinetics properties of Leu94Val mutant of horse cyt.c(Biochemistry35, 5538 (1996).) and several characteristic properties are deduced using our theoretical

ISSN:0009-4536    

DOI:10.1002/jccs.200300050

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractThe stability constants of Mg2+, Ca2+, Sr2+and Ba2+perchlorates with 2,4‐diamino‐3,5‐dicyanothiophene (DADCT) have been determined at 15, 25, 35, 45 and 55 °C in 10, 20 and 30% (w/w) propanol‐1‐water mixtures using the conductometric technique.The conductometric data were analysed using a model 1:1 stoichiometry by which the stability constants, Ks, and the limiting molar conductance were obtained. The plots of specific conductance versus the molar ratio [A]o/[Cn+]osuggest that the stoichiometry of metal ion complexes is of a 1:1 complex.The stability constants tend to decrease with the atomic number as well as the ionic radii in the order Mg>Ca>Sr>Ba in 10%>20%>30% (w/w) propanol‐1‐water solvents. This trend was found to agree exactly with the Irving‐Williams series for all the systems under investigation.The thermodynamic parameters, ΔGo, ΔHoand ΔSo, for the complexation processes of all the complexes were evaluated and their significa

ISSN:0009-4536    

DOI:10.1002/jccs.200300051

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractKinetic studies on the formation of charge transfer complexes of 2‐(1H)‐pyridinethione with π‐acceptors p‐chloranil and p‐bromanil in dipolar aprotic solvent N,N‐dimethylformamide have been carried out spectrophotometrically at various temperatures. The reaction follows an overall third order rate equation, through first order with respect to π‐acceptors and second order with respect to the 2‐(1H)‐pyridinethione. The rates were found to increase with increasing temperature. Activation parameters, ΔH≠ and ΔS≠ have been calculated for the charge transfer complexes. The structure of the products was confirmed by their elemental analysis, IR,1H NMR and mass spectrometry. Conductometric method has been used to investigate the electron donor‐acceptor complex formation. The stoichiometries of these complexes have been established and their conductance (σP−) and molar conducti

ISSN:0009-4536    

DOI:10.1002/jccs.200300052

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractThe taurocholate (TC) to lecithin (L) molar ratio (K) and molecular weight of mixed TC‐L micelles coexisting with simple TC micelles were determined by employing laser light‐scattering measurement and an interaction model of mixed and simple micelles. When the nonmixed micellar taurocholate (NMTC) concentration was greater than 25 mM, the K value and molecular weight of mixed TC‐L micelles were ∼ 4.3 and ∼ 20,000 daltons, respectively, at an L concentration of 6 mM, and ∼ 2.0 and ∼ 35,000 daltons at L concentrations of 12 mM and 21 mM. A quantitative model of the formation of simple TC micelles and mixed TC‐L micelles indicated that, when the NMTC concentration was greater than 25 mM, mixed TC‐L micelles were unstable at low L levels because of low concentrati

ISSN:0009-4536    

DOI:10.1002/jccs.200300053

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractThe synthesis and spectroscopic characterization of novel organotin(IV) complexes are described. The monomeric compound possesses trans octahedral, and the dimeric complex is of six‐coordinated skew trapezoidal bipyramidal geometry. The triorganotin(IV) complexes are assigned a polymeric trigonal bipyramidal and a tetrahedral structure. The ED50test showed toxicity to brine shrimp naupli and bio‐activities tests of the compounds exhibited antibacterial, antifungal and excellent anti‐tumour activ

ISSN:0009-4536    

DOI:10.1002/jccs.200300054

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractTreatment of [Ru]C=CPh (1, [Ru] = (η5‐C5H5)(dppe)Ru, dppe = Ph2PCH2CH2PPh2) with PhN=C=S at room temperature affords the [2 + 2] cycloaddition product (2) which contains a four‐membered‐ring heterocycle. A series of cationic S‐alkylated ruthenium vinylidene complexes [Ru]=C=C(Ph)C(=NPh)SCH2R+(3a, R = CONH2;3b, R = CH=CH2;3c, R =p‐C6H4CF3) and N‐alkylated ruthenium vinylidene complexes [Ru]=C=C(Ph)C(=S)N(Ph)CH2R+(4b, R = CH=CH2;4c, R =p‐C6H4CF3) are prepared from2with organic halides at room temperature with high yields. Deprotonation of3aand3cbyn‐Bu4NOH in acetone induces novel cyclization reactionsviaC‐C bond formation and yields neutral five‐membered‐ring heterocyclic complexes (5a, R = CONH2;5c, R =p‐C6H4CF3). In a similar manner, deprotonation of4band4cby NaOMe in CH2Cl2also induces another cyclization to yield the pyrrole‐2‐thione complexes (6b, R = CH=CH2;6c, R =p‐C6H4CF3). At room temperature,5cisomerizes to the 2‐aminothi

ISSN:0009-4536    

DOI:10.1002/jccs.200300055

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractA poly(4‐vinylpyridine)/mercury film electrode (PVP/MFE) was applied for the determination of trace amounts of zinc ion by square‐wave anodic stripping voltammetry. The PVP/MFE shows better mechanical stability, higher sensitivity, and enhanced resistance to common ions and surface‐active compounds than conventional mercury film electrodes. Various experimental parameters affecting the performance of the PVP/MFE in Zn(II) determination were optimized. Under the optimized conditions, the PVP/MFE shows a linear response up to 50 μg l−1with a detection limit (S/N = 3) of 1.7 μg l−1. The practical applicability of the electrode was evaluated through the analytical estimation of Zn(II) in various r

ISSN:0009-4536    

DOI:10.1002/jccs.200300056

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractThe nitrile ligands undergo hydrolysis to amides under mild conditions when Ru(NH3)5NCR2+(R = 4‐py, 4‐pyCH3+and CH=CHCN) complexes are oxidized to Ru(III). The rate of hydrolysis of Ru(NH3)5NCpy3+increases with the increase in acid concentration as a result of the protonation of the pyridyl nitrogen. The kinetic results yield the rate constant of the hydrolysis for Ru(NH3)5NCpyH4+complex as 0.12 s−1at μ = 1.0 M HCl/LiCl, greater than that of a deprotonated species by nearly two orders of magnitude. The enormous increase in rate for the protonated complex arises mainly from the increase in electron withdrawing power due to protonation which will decrease the electron density on the nitrile carbon and make it easier for the nucleophilic attack of the water mo

ISSN:0009-4536    

DOI:10.1002/jccs.200300057

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractIn this paper, the effect of polar potentials on Schiff base self‐assembled monolayers was mainly investigated by the Electrochemical Impedance Spectroscopy (EIS) method. Different polar potentials and polarizing times were applied to this newly created monolayer, with an intention to reveal the relationship between the polar potential and the structure of this monolayer. The result showed that different polar potentials correspond to different complex resistance (Nyquist) plots, and the effect of polarizing time on this monolayer is regular and could be detected and reflected by the EIS plots conveniently. The results also demonstrated that the content of a C=N group related with the packing degree of this monolayer intimately, and the lower content of a C=N group corresponds to a denser structure of the monolayer, which could be presented by the value of electron transfer resistance (Rct). The main meaning of our work is to have developed one novel way that could reflect the relationship between the structure of the monolayer and the polar potential, which surely will encourage further experiments not only on Schiff bases but on other self‐assembled monolayer containing active gro

ISSN:0009-4536    

DOI:10.1002/jccs.200300058

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractSilica gel was used as the starting material to synthesize nano‐sized quartz in the presence of alkaline solution. The experiments were carried out in autoclaves under the conditions of 0.25 M NaOH solution, 210 °C, and vapor pressure.SiO2‐X2and α‐cristobalite appear as the intermediate unstable phases during the synthesis of quartz which occurs as a single stable phase in the synthetic product after 26 hour experiments. The growth of quartz can be separated into a fast linear growth with the rate of 75.3 nm/hr and a slow one with the rate of 1.4 nm/hr. It is shown that quartz begins to grow at 16.1 hours and the fast growth changes abruptly to the slow one at about 26.7 hours after the start of the experiments. On the other hand, nucleation occurs from 20 to 28 hours.For the synthetic quartz, an amount of about 32% of the population is nano‐sized, but most of the population (about 78%) lies between 50 nm and 300 nm, and the geometric mean size is about 182 nm.From the results of this preliminary study, it is encouraging that a high percentage of nano‐sized quartz could possibly be produced if suitable experimental conditions

ISSN:0009-4536    

DOI:10.1002/jccs.200300059

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY