排序方式: 共有78条查询结果,搜索用时 15 毫秒
1.
Two methods, e.g. initial rate method and thermokinetic reduced extent method were presented for studies on non-competitive
inhibition. Arginase-catalyzed the hydrolysis of L-arginine toL-ornithine and urea and the inhibition of this reaction by sodium fluoride were studied in the absence and presence of exogenous
of Mn2+at 37°C in 40 mM sodium barbiturate-hydrochloric acid buffer solution (pH 7.4). Both methods were successively used to determine
the values of K1. The advances and disadvantages of each method were compared in this paper. Exogenous Mn2+ could result in more sensitivity of arginase to F-1. Since the inhibition of arginase by F-1 depends on the pH values of the reaction system and behave as a non-competitive inhibition, it probably due to its small
volume and high electronic density allow it access to the activity site of the enzyme and replaces of μ-OH2 (or μ-OH) as the bridge ligand with Mn(II, II) cluster. However, further studies are necessary to determine the modes of
interaction of F-1 with bovine liver arginase.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
Xi Li Yi Liu Jun Wu Huigang Liang Songsheng Qu 《Journal of Thermal Analysis and Calorimetry》2002,67(3):589-595
The action of three kinds of the selenomorpholine compounds on a strain ofEscherichia coli was studied by microcalorimetry. Differences in their capacities to affect the metabolism of this bacterium were observed.
The extent and duration of the effect on the metabolism as judged from the rate constant (k) of Escherichia coli (in log phase) varied with the different drugs. The kinetics show that selenomorpholine compounds had an effect on the metabolism
process of Escherichia coli. The k of Escherichia coli in the presence of the drugs increased with the increasing concentrations of the drugs (C) at low concentration; but at high concentration, the rate constant decreased with the increasing concentrations of the drugs.
The experimental results reveal that the sequence of antibiotic activity of selenomorpholines is: N-selenomorpholinemethyl
succinimide and its hydrochloride>N-(α-selenomorpholinebenzyl) succinimide.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
4.
The thermokinetics of the formation reactions of cerium(III) n-dodecylbenzene sulfonate and cerium(III) stearate are studied by using a microcalorimeter. On the basis of experimental and
calculated results, three thermodynamics parameters (the activation enthalpies, the activation entropies, the activation free
energies), the rate constant, three kinetic parameters (the activation energies, the pre-exponential constant and the reaction
order) and the enthalpies of the reaction of preparing cerium(III) n-dodecylbenzene sulfonate in the temperature range of
20–35°C and cerium(III) stearate in the temperature range of44.6–62.8°C are obtained. The results showed that the title reactions
easily took place in the studied temperature.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
6.
F Xu L X Sun Z C Tan J G Liang T Zhang 《Journal of Thermal Analysis and Calorimetry》2006,83(1):187-191
Molar heat capacities
of acetaminophen were precisely measured with a small sample precision automated
adiabatic calorimeter over the temperature range from 80 to 330 K. A solid-solid
transition at 149.96 K was found from the Cp,m-T curve. The polynomial functions of Cp,.m(J
K-1 mol-1) vs. T were established
on the heat capacity measurements by means of the least square fitting method.
Thermal decomposition
processes of acetaminophen have been studied by thermogravimetry. And the
thermal decomposition kinetics parameters, such as activation energy E, pre-exponential factor A
and reaction order n, were calculated by
TG-DTG techniques with the Freeman-Carroll method, Kissinger method
and Ozawa method. Accordingly the thermal decomposition kinetics equation
of acetaminophen is expressed as: dα/dt=2.67·107e-89630/RT(1-α)0.23.
The process of fusion has been investigated through
DSC. The melting point, molar enthalpy and entropy of fusion are to be (441.89±0.04)
K, 26.49±0.44 kJ mol-1 and 59.80±1.01
J K-1 mol-1,
respectively. 相似文献
7.
Z. Xiancheng N. Zhaodong X. Yan Z. Yuanqin Z. Honglin 《Journal of Thermal Analysis and Calorimetry》1999,58(2):279-285
The power-time curves of two species of bacteria, Vibro metschnikovii, Vibro bollisae were determined calorimetrically by using a 2277 bioactivity monitor. The power-time curve equation of bacterial growth in the log phase can be expressed as
. A self-function recursion equation, fi=b1fi+1+b2fi+2, was obtained through the perfect non-linear function
. A linear equation, i/i+1=b1+b2i+2/i+1, was obtained by using the self-function recursion equation. The rate constants of bacterial growth k1, the time constant of the calorimeter k, the generation times G, and the pre-exponential factors A were obtained from the power—time curve equations.Power—time curve equations of bacterial growth in the log phase are expressed for V.metschnikovii as =1.05(e0.0228t–e–0.0175t), and for V. bollisae as =1.58(e0.0278t–e–0.0170t).This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
8.
X. C. Zeng Y. Chen S. Q. Cheng X. G. Meng Q. Wang 《Journal of Thermal Analysis and Calorimetry》1999,58(2):477-485
A novel method for the determination of rate constants of reactions, the time-variable method, is proposed in this paper. The method needs only three time points (t), peak heights () and pre-peak areas (), obtained from the measured thermoanalytical curve. It does not require the thermokinetic reaction to be completed. It utilizes data-processing on a computer to give the rate constants. Four reaction systems, including a first-order reaction, second-order reactions (with equal concentrations and with unequal concentrations) and a third-order reaction, were studied with this method. The method was validated and its theoretical basis was verified by the experimental results.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
9.
10.
在37 ℃, pH=7.4~9.4, 40 mmol?L-1的巴比妥钠-HCl缓冲体系中, 利用热动力学方法研究了NaF对精氨酸酶催化L-精氨酸水解反应的抑制作用. 实验结果表明, NaF对精氨酸酶反应的抑制作用, 属于非竞争性可逆抑制, 其抑制率依赖于反应体系的pH值, 底物L-精氨酸和外源Mn2+离子对相对抑制率和抑制常数的影响不显著. 在pH值为7.4, 外源锰离子浓度分别为0和0.167 mmol?L-1时的抑制常数分别为1.48和1.84 mmol?L-1. F-离子对精氨酸酶的抑制不是与底物L-精氨酸竞争酶的活性位, 而是影响了水分子与双核锰簇的桥式配位作用, 使反应过程中, 作为亲核试剂进攻L-精氨酸胍基碳的羟基离子难于生成或使其浓度减小, 从而降低了酶反应活性. 相似文献