No abstract available.
Kinetics* ; Wrist*

The Michaelis-Menten equation is one of the best-known models describing the enzyme kinetics of in vitro drug elimination experiments, and takes a form of equation relating reaction rate (V) to the substrate concentration ([S]) via the maximum reaction rate (Vmax) and the Michaelis constant (Km). The current study was conducted to compare the accuracy and precision of the parameter estimates in the Michaelis-Menten equation from various estimation methods using simulated data. One thousand replicates of simulated [S] over serial time data were generated using the results of a previous study, incorporating additive or combined error models as a source of random variables in the Monte-Carlo simulation using R. From each replicate of simulated data, Vmax and Km were estimated by five different methods, including traditional linearization methods and nonlinear ones without linearization using NONMEM. The relative accuracy and precision of the estimated parameters were compared by the median values and their 90% confidence intervals. Overall, Vmax and Km estimation by nonlinear methods (NM) provided the most accurate and precise results from the tested 5 estimation methods. The superiority of parameter estimation by NM was even more evident in the simulated data incorporating the combined error model. The current simulation study suggests that NMs using a program such as NONMEM provide more reliable and accurate parameter estimates of the Michaelis-Menten equation than traditional linearization methods in in vitro drug elimination kinetic experiments.
In Vitro Techniques ; Kinetics ; Methods

Fructose 1,6 bisphosphate adolase A and C (FPA A4 and C44) have been found to bind specifically to heparin in physiological ionic strength. The researcher found that activity of FPA was inhibited by heparin. The inhibition of FPA A4 and C4 depend on the degree of sulfation. Inhibition activity FPA of heparin increase directly proportional to molecule lenghth. Kinetic studies showed that: inhibitory mode of heparin on FPA was the linear mixed type inhibition, in which velocity can be driven to zero at high heparin concentration
Kinetics ; Fructose-Bisphosphate Aldolase ; Heparin

The kinetics of inhibition of Na-K-ATPase activity by o, 0-dimethyl o-(2,2-dichlorovinyl) phosphate(DDVP) was investigated with homogenerate of rabbit cerebral cortex. The results were summarized as the follows : 1. Inhibition of Na-K-ATPase activity by DDVP showed a dose-dependent manner with an estimated I5.0 of 3.5x10(-4) M. 2. Altered pH and activity curves for Na-K-ATPase activity demonstrated comparable inhibition by DDVP in buffered acidic, neutral and alkaline pH renges. 3. Kinetic studies of cationic-substrate activation of Na-K-ATPase showed noncompetitive with respect to substrate and K+ and a mixed type inhibition with respect to Na+. These results suggest that DDVP appeared to exert its effects on Na-K-ATPase activity by interfering with the formation of Na-dependent phosphoenzyme.
Cerebral Cortex* ; Dichlorvos* ; Hydrogen-Ion Concentration ; Kinetics

No abstract available.
DNA* ; Kinetics* ; Nervous System Neoplasms* ; Nervous System*

High temperature liquid water (HTLW) has drawn increasing attention as an environmentally benign medium for organic chemical reactions, especially acid-/base-catalyzed reactions. Non-catalyzed hydrolyses of gallotannin and tara tannin in HTLW for the simultaneous preparation of gallic acid (GA) and pyrogallol (PY) are under investigation in our laboratory. In this study, the hydrolysis kinetics of gallotannin and tara tannin were determined. The reaction is indicated to be a typical consecutive first-order one in which GA has formed as a main intermediate and PY as the final product. Selective decomposition of tannin in HTLW was proved to be possible by adjusting reaction temperature and time. The present results provide an important basic data and reference for the green preparation of GA and PY.
Catalysis ; Hydrolysis ; Kinetics ; Tannins ; chemistry ; Temperature

Internal-loop granular sludge bed nitrifying reactor is a new type of aerobic nitrifying equipment and has shown a good potential for nitrification. To study the flow pattern and construct the flow model, the tracer tests were performed using pulse stimulus-response technique. Based on the experimental results, the flow pattern in the settling section and the circulating section of reactor were analyzed by axial dispersion model and tank-in-series model, respectively. The dispersion number D/uL of 0.00148 in the settling section indicates that its flow pattern is similar to plug flow reactor (PFR), and the series number N of 1.021 in the circulating section indicates that its flow pattern is similar to continuously stirred tank reactor (CSTR). During steady state, the theoretic hydraulic retention time is 360 min, and the actual hydraulic retention time is 341.2 min. The percentage of dead space in the reactor is 5.22%, thereinto the dead space caused by biomass (db ) is 0.75 % and the hydraulic dead space (dh) is 4.47%, which shows that the structural performance of the reactor is excellent. Based on the experiments and analysis, a model of CSTR and PFR in series was constructed. The actual hydraulic retention time distribution of the reactor is in good agreement with the model predictions. Since the relative error between them is 8.56%, the model is accurate to describe the flow pattern. The results have laid a foundation for the kinetic model of the reactor and will be helpful for its design and operation.
Bioreactors ; Kinetics ; Models, Theoretical ; Nitrites ; metabolism ; Sewage

The kinetics of immobilized cells of Brevibacterium ammoniagenes MA-2 and Brevibacterium flavum MA-3 cells were studied. By means of both a theoretical analysis of diffusion in the gel particles and an experimental determination of apparent kinetic parameters, the intrinsic kinetic parameters of immobilized cells of B. ammoniagenes MA-2 and B. flavum MA-3 cells were obtained.
Brevibacterium ; isolation & purification ; metabolism ; physiology ; Kinetics

OBJECTIVEIn this study, we examined the biodegradation of Dichloroethylene (DCE) by two strains of aerobic bacteria.

METHODSUsing batch experiments, we measured the biodegradation rates of DCE and the residual concentrations of DCE for each bacterial strain. The varying trends in biodegradation rates with different initial concentrations of DCE were fitted to kinetic models.

RESULTSThe biodegradation kinetics of DCE by the strain DT-X, which uses toluene as co-metabolic substrate, fitted the Monod model (corresponding parameters: v(max)=0.0075 h(-1), K(s)=2.12 mg/L). The biodegradation kinetics of DCE by the strain DT-M, which uses 1,1-Dichloroethylene as single substrate, fitted the Haldane model (parameters: v(max) =0.0046 h(-1), K(s)=4.25 mg/L, K(i)=8.47 mg/L).

CONCLUSIONThe substrate removal rate constant of 1,1-Dichloroethylene of the co-metabolic strain DT-X was much higher than that of strain DT-M. The substrate removal rates obtained from both bacterial strains in this study were higher than those reported in similar studies.

Three-dimensional thermoluminescence (TL) spectra from MgAl2O4 irradiated with UV light were measured over 300~600 K and 300~800 nm. The peak positions of TL glow curves were shifted to lower temperature with increasing the exposure time of UV light. The 476 K TL glow curve is due to the second kinetics and its activation energy and escape frequency factor are calculated to be 0.85 eV and 1.92x10(6) sec(-1), respectively. The TL spectra were split into 530 nm and 700 nm emission bands which were associated with V(2+) and Cr(2+), respectively. The linearity range of 700 nm emission band is smaller than that of 530 nm emission band, but the saturation time of 700 nm emission band is longer than that of 530 nm emission band.
Aluminum* ; Kinetics ; Magnesium* ; Ultraviolet Rays ; United Nations