scholarly journals Varing chemical equilibrium gives kinetic parameters

2013 ◽  
Author(s):  
Edward Flach ◽  
Santiago Schnell
Keyword(s):  
Steady State ◽  
Kinetic Parameters ◽  
Dynamic Behaviour ◽  
Dynamic Equilibrium ◽  
Parameter Estimates ◽  
Input Rate ◽  
Fitting In ◽  
State Concentration ◽  
Static Behaviour ◽  
Concentration Space

We are interested in finding the kinetic parameters of a chemical reaction. Previous methods for finding these parameters rely on the dynamic behaviour of the system. This means that the methods are time-sensitive and often rely on non-linear curve fitting. In the same manner as previous techniques, we consider the concentrations of chemicals in a reaction. However, we investigate the static behaviour of the reaction at dynamic equilibrium, or steady state. Here too, the chemical concentrations depend on the kinetic parameters of the reaction. In an open reaction, the static concentrations also depends on the rate of input of the source of reacting chemical. Controlling this input rate slides the steady state along a curve in concentration space. This curve is determined by the kinetic parameters. The plane of this curve is sufficient to find the kinetic parameters. The new method we propose uses only the steady state concentration values to determine the kinetic parameters of the reaction. These values are constant once dynamic equilibrium is achieved, and so can be read accurately. Readings can be repeated readily to reduce error. Thus this new technique is simple and could produce accurate kinetic parameter estimates.

scholarly journals Mathematical Modeling of Cyclic Voltammogram Curves of Copper Deposition

2021 ◽  
Author(s):  
Shuvodeep De
Keyword(s):  
Steady State ◽  
Kinetic Parameters ◽  
Deposition Rate ◽  
Surface Coverage ◽  
Dynamic Equilibrium ◽  
Rotating Disk Electrode ◽  
Copper Deposition ◽  
Cyclic Voltammogram ◽  
Additive Concentration ◽  
Organic Additives

The manufacturing of interconnects and the packaging of integrated circuits are achieved with electrodeposition of copper or other metals. In order to increase the rate of deposition, especially for the large features in packaging, forced convection is provided with certain agitation mechanisms. Although this reduces deposition time, it leads to non-uniform mass transport within each feature and between different features. Special organic additives are used in the solution during the process in order to tune the nucleation and growth of metal, as well as to modify the deposition rate and improve the uniformity. A mathematical model to describe the behavior of organic additives in conjugation with fluid flow and features of various geometry and dimensions is very much desired to facilitate chemistry and process development. In order to achieve this, the physiochemical kinetics of additive and their influence on the Cu deposition rate need to be described precisely. This presentation focuses on a method to extract the kinetic parameters describing the combined effect of multiple additives during copper deposition using rotating disk electrode (RDE). The one-dimensional steady state convection-diffusion equation for each of the chemical species including copper is solved by a semi-analytical method for a range of potentials. The boundary conditions of these differential equations are coupled on the surface of the RDE through the surface coverage of the absorbed species. The steady state of surface coverage of the species represents a dynamic equilibrium of three key processes i.e., adsorption, desorption, and consumption (incorporation). When equilibrium is achieved, the net rate of adsorption and desorption becomes equal to the rate of consumption. At each value of potential, the surface coverage of the additives is solved. At first, the solution is obtained with only one species known as suppressor and it was found that in a specific range of voltage and kinetic parameter multiple solutions of the surface coverage exist at same applied potential. This mathematically explains the S-shaped negative differential resistance (NDR) feature in experimental Cyclic Voltammogram (CV) curves. Figure 1 shows three such experimental S-shaped curves for different concentration of suppressors. The NDR region obtained in the theoretical CV curve is sensitive to the kinetic parameters of the additives. It is possible to match the theoretical and the experimental CV curves by optimizing the kinetic parameters. Determination of the kinetic parameters by particle swarm optimization using experimental data for multiple additive concentration will be discussed in detail in this talk.

Effect of Kinetic Parameters on the Dynamicsof Continuous Crystallizers

1998 ◽  
Vol 63 (1) ◽  
pp. 121-131 ◽  
Author(s):  
Jaroslav Nývlt
Keyword(s):  
Steady State ◽  
Kinetic Parameters ◽  
Production Rate ◽  
Crystal Size ◽  
Crystallization Process ◽  
Dynamic Behaviour ◽  
Nucleation And Growth ◽  
Suspension Concentration ◽  
Run Time ◽  
Periodic Cycles

Continuous crystallizers can exhibit periodic cycles of supersaturation, production rate, suspension concentration, crystal size and related quantities. These cycles are most pronounced at the beginning of the crystallization process and depend on the value of kinetic parameters whether they are damped during the run time. Apparently, the cycling behaviour of the crystallizing system depends on the value of ratio of the nucleation and growth exponents n/g. The higher the value of this ratio, the more pronounced is the instability of the system. Admixtures that have a significant effect on the kinetic parameters can dramatically affect the dynamic behaviour of crystallizers so that the steady state may not be established at all.

scholarly journals New kinetic parameters for rat liver arginase measured at near-physiological steady-state concentrations of arginine and Mn2+

1992 ◽  
Vol 283 (3) ◽  
pp. 653-660 ◽  
Author(s):  
S Maggini ◽  
F B Stoecklin-Tschan ◽  
S Mörikofer-Zwez ◽  
P Walter
Keyword(s):  
Steady State ◽  
Kinetic Parameters ◽  
Rat Liver ◽  
Urea Cycle ◽  
Hill Coefficient ◽  
Regulatory Effect ◽  
Free System ◽  
State Concentration ◽  
Good Agreement

A cytosolic cell-free system from rat liver containing the last three enzymes of the urea cycle, a number of cofactors and the substrates aspartate and citrulline was shown to synthesize urea at near-physiological rates ranging between 0.40 and 1.25 mumol/min per g of liver. This system was used to determine the kinetic parameters for arginase. With saturating amounts of Mn2+ (30 microM), arginine remained at a steady-state concentration of 5-35 microM depending on the aspartate and citrulline supply. Vmax. at micromolar arginine concentrations was between 1.10 and 1.25 mumol/min per g of liver, the K0.5 (arginine) between 6.0 and 6.5 microM and positive co-operativity was observed (Hill coefficient 2). Omission of Mn2+ caused a significant accumulation of arginine during the incubation, suggesting a regulatory effect of arginase. Under these conditions, Vmax. was 1.10-1.65 mumol/min per g of liver and the Km (arginine) increased up to 14.4-21.1 microM. The apparent Ka for Mn2+ in the presence of physiological concentrations of ATP, Mg2+ and arginine was calculated to be maximally 8 microM. Initial-velocity experiments with millimolar arginine concentrations as the direct substrate gave the following results, which are in good agreement with literature data. In the absence of Mn2+, Vmax. was 71.3 mumol/min per g of liver and the Km (arginine) 1.58 mM. With 30 microM-Mn2+, Vmax. was 69.4 mumol/min per g of liver and the Km (arginine) decreased to 0.94 mM. On the basis of our results, we propose the presence of high-affinity and low-affinity sites for arginine on rat liver arginase and postulate that alterations in arginase activity arising from changes in the concentration of arginine and of the cofactor Mn2+ may contribute to the regulation of ureagenesis in vivo.

Regulation of cytosolic free Ca2+ concentration in acinar cells of rat pancreas

1983 ◽  
Vol 245 (3) ◽  
pp. G347-G357 ◽  
Author(s):  
H. Streb ◽  
I. Schulz
Keyword(s):  
Steady State ◽  
Incubation Medium ◽  
Minimal Medium ◽  
Acinar Cells ◽  
Pancreatic Acinar Cells ◽  
Atpase Inhibitor ◽  
Rat Pancreas ◽  
Mitochondrial Inhibitors ◽  
Pancreatic Cells ◽  
State Concentration

Ca2+ uptake into isolated exocrine pancreatic cells with highly permeable plasma membrane was determined by measuring the decrease in free Ca2+ concentration of the surrounding incubation medium with a Ca2+-specific electrode. In the presence of Mg-ATP and respiratory substrates the free Ca2+ concentration of the incubation medium decreased rapidly after addition of leaky cells until a stable medium free Ca2+ concentration of 4.2 +/- 0.1 X 10(-7) mol/l was obtained. Changes in the medium free Ca2+ concentration at steady state by addition of Ca2+ or EGTA were buffered by cellular uptake or release, respectively, until the steady-state free Ca2+ concentration was reestablished. When nonmitochondrial Ca2+ uptake was determined in the presence of a combination of mitochondrial inhibitors (10(-5) mol/l antimycin, 5 X 10(-6) mol/l oligomycin, and 10(-2) mol/l azide), the rate of uptake was considerably reduced, while the steady-state concentration was unaltered. In contrast, mitochondrial uptake that could be observed in the presence of the ATPase inhibitor vanadate (2 X 10(-3) mol/l) proceeded at the same rate as the control, but the minimal medium free Ca2+ concentration reached was 2.4 +/- 0.1 X 10(-7) mol/l higher than the control. Addition of secretagogues at steady-state free Ca2+ concentration resulted in a Ca2+ release of 0.73 +/- 0.08 nmol/mg protein. The increase in medium free Ca2+ concentration was entirely transient and followed by reuptake to the prestimulation level. The data indicate that a cytosolic free Ca2+ concentration of 4 X 10(-7) mol/l can be regulated in pancreatic acinar cells by a nonmitochondrial Mg2+-dependent Ca2+ pool.

Noradrenaline-induced calorigenesis in warm- or cold-acclimated rats. In vivo estimation of adrenoceptor concentration of noradrenaline effecting half-maximal response

1980 ◽  
Vol 58 (9) ◽  
pp. 1072-1077 ◽  
Author(s):  
Florent Depocas ◽  
Gloria Zaror-Behrens ◽  
Suzanne Lacelle
Keyword(s):  
Adipose Tissue ◽  
Steady State ◽  
Brown Adipose Tissue ◽  
Maximal Response ◽  
Brown Adipose ◽  
Acclimation Group ◽  
Arterial Plasma ◽  
State Concentration ◽  
Na Uptake

Desmethylimipramine (DMI, 1 mg DMI∙HCl kg−1) and normetanephrine (NMN, 1 μg min−1 g−0.74) were used to inhibit, respectively, neuronal and extraneuronal uptakes of noradrenaline (NA) during calorigenesis induced in barbital-sedated warm-acclimated (WA) or cold-acclimated (CA) rats by infusion of NA, a procedure which mimics the effects of NA released within calorigenic tissues in response to cold exposure. The doses of the inhibitors were selected for maximal effectiveness in potentiating calorigenic response and for minimal side effects. For rats of either acclimation group treated with DMI and NMN, with DMI only, or with neither inhibitor the doses of NA required to evoke approximately half-maximal calorigenic responses were, respectively, 0.5, 1.0, and 3.5 ng min−1 g−0.74. The corresponding steady-state concentrations of NA in arterial plasma averaged 14.3, 21.7, and 43.2 nM in the three groups of WA rats and 10.0, 14.8, and 31.9 nM in the three groups of CA rats. Reduction by NA uptake inhibitors of the circulating levels of NA necessary to stimulate calorigenesis, half-maximally, presumably in brown adipose tissue, indicates a reduction in the steepness of the NA concentration gradient between capillary plasma and synaptic clefts in that tissue. The steady-state concentration of NA in blood plasma of rats treated with DMI and NMN and infused with NA at a dose of 0.5 ng min−1 g−0.74 (~1 × 10−8 M) is a good estimate of the NA concentration required at calorigenic adrenoceptors to effect half-maximal activation. Presumably, this concentration is also an estimate of that resulting from NA released at nerve endings during cold-induced activation of nonshivering thermogenesis at half-maximal rates in brown adipose tissue.

scholarly journals Characterization of Nicotinamidases: Steady State Kinetic Parameters, Classwide Inhibition by Nicotinaldehydes, and Catalytic Mechanism

Biochemistry ◽  
2010 ◽  
Vol 49 (49) ◽  
pp. 10421-10439 ◽  
Author(s):  
Jarrod B. French ◽  
Yana Cen ◽  
Tracy L. Vrablik ◽  
Ping Xu ◽  
Eleanor Allen ◽  
...  
Keyword(s):  
Steady State ◽  
Kinetic Parameters ◽  
Catalytic Mechanism ◽  
Steady State Kinetic ◽  
State Kinetic

Divergent effects of intravenous GSH and cysteine on renal and hepatic GSH

1992 ◽  
Vol 263 (2) ◽  
pp. R348-R352 ◽  
Author(s):  
S. Aebi ◽  
B. H. Lauterburg
Keyword(s):  
Steady State ◽  
De Novo ◽  
Feedback Inhibition ◽  
Therapeutic Use ◽  
Steady State Concentration ◽  
De Novo Synthesis ◽  
State Concentration ◽  
Cellular Thiol

There is a growing interest in the therapeutic use of sulfhydryls. To assess the effect of glutathione (GSH) and cysteine on the cellular thiol status, thiols were administered intravenously to rats in doses ranging from 1.67 to 8.35 mmol/kg with and without pretreatment with 4 mmol/kg buthionine-[S,R]-sulfoximine (BSO), an inhibitor of GSH synthesis. One hour after administration of 1.67 mmol/kg GSH, the concentration of GSH rose from 5.2 +/- 1.0 to 8.4 +/- 0.9 mumol/g and from 2.5 +/- 0.5 to 3.7 +/- 0.7 mumol/g in liver and kidneys, respectively. After 8.35 mmol/kg, hepatic GSH did not increase further, but renal GSH rose to 6.7 +/- 1.8 mumol/g. Infusion of cysteine increased hepatic GSH to the same extent as intravenous GSH, but renal GSH did not increase after 1.67 mmol/kg and even significantly decreased to 0.6 +/- 0.2 mumol/g after 8.35 mmol/kg. In the presence of BSO, GSH resulted in a significant increase in renal but not hepatic GSH, suggesting that the kidneys take up intact GSH and indicating that the increment in hepatic GSH was due to de novo synthesis. The present data show that hepatic GSH can be markedly increased in vivo by increasing the supply of cysteine. Measurements of hepatic cysteine indicate that up to a concentration of approximately 0.5 mumol/g cysteine is a key determinant of hepatic GSH, such that the physiological steady-state concentration of GSH in the liver appears to be mainly determined by the availability of cysteine. At higher concentrations GSH does not increase further, possibly due to feedback inhibition of GSH synthesis or increased efflux.(ABSTRACT TRUNCATED AT 250 WORDS)

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