Impact of high pyruvate concentration on kinetics of rabbit muscle lactate dehydrogenase

In order to evaluate the effectiveness of l-lactate dehydrogenase (LDH) from rabbit muscle as a regenerative catalyst of the biologically important cofactor nicotinamide adenine dinucleotide (NAD), the kinetics over broad concentrations were studied to develop a suitable kinetic rate expression. Despite robust literature describing the intricate complexations, the mammalian rabbit muscle LDH lacks a quantitative kinetic rate expression accounting for simultaneous inhibition parameters, specifically at high pyruvate concentrations. Product inhibition by l-lactate was observed to reduce activity at concentrations greater than 25 mM, while expected substrate inhibition by pyruvate was significant above 4.3 mM concentration. The combined effect of ternary and binary complexes of pyruvate and the coenzymes led to experimental rates as little as a third of expected activity. The convenience of the statistical software package JMP allowed for effective determination of experimental kinetic constants and simplification to a suitable rate expression:

Special features of the compensation effect in non-isothermal kinetics of solid-phase reactions

The appearance of the compensation effect (logA=a+bE) in non-isothermal kinetics of solid-phase reactions is discussed. An analytical expression of the compensation effect is derived in the form $$InA = In\frac{{E\left( {\frac{{dT}}{{dt}}} \right)_s }}{{RT_s^2 }} + \frac{E}{{RT_s }}$$ It is demonstrated that the compensation effect appears in a number of chemical reactions if theT _s and rate constant values are close. Experimental data confirm the theoratical discussion.     

The mechanism of thermal decomposition of ionic oxalates

A mechanism for the thermal decomposition of ionic oxalates has been proposed on the basis of three quantitative relationships linking the quantitiesr _c/r _i (the ratio of the Pauling covalent radius and the cation radius of the metal atom in hexacoordination) andΣI _i (the sum of the ionization potentials of the metal atom in kJ mol^?1) with the onset oxalate decomposition temperature (T _d) (Eq. 1) the average C-C bond distance (¯d) (Eq. 2), and the activation energy of oxalate decomposition (E _a) (Eq. 3): (1) $$T_d = 516 - 1.4006\frac{{r_c }}{{r_i }}(\sum I_i )^{\frac{1}{2}}$$ (2) $$\bar d = 1.527 + 5.553 \times 10^{ - 6} \left( {122 - \frac{{r_c }}{{r_i }}(\sum I_i )^{\frac{1}{2}} } \right)^2$$ (3) $$E_a = 127 + 1.4853 \times 10^{ - 6} \left( {\left( {\frac{{r_c }}{{r_i }}} \right)^2 \sum I_i - 9800} \right)^2$$ On the basis of these results it is proposed that the thermal decomposition of ionic oxalates follows a mechanism in which the C-O bond ruptures first. From Eq. 3 it is further proposed that strong mutual electronic interactions between the oxalate and the cations restrict the essential electronic reorganization leading to the products, thereby increasingE _a.     

Effects of washing conditions on the thermal decomposition behaviour of gelled UO3 microspheres

DTA, TG and DTG curves obtained in various atmospheres using different heating rates were used together with X-ray examinations to study the thermal decomposition mechanisms of two types of gelled UO₃ microspheres: ammonia-washed (UN) and hot water-washed (UH) microspheres. The kinetics of the thermal decompositions were studied. The specific reaction rate constantk _r for the decomposition of UO₃ to U₃O₈ could be expressed in terms of the activation energy and the pre-exponential factor by the expressions: $$\begin{gathered} K_r (s^{ - 1} ) = 1.277 \times 10^{18} \exp \frac{{ - 295.4}}{{RT}}for the UN spheres, \hfill \\ K_r (s^{ - 1} ) = 8.406 \times 10^{19} \exp \frac{{ - 263.2}}{{RT}}for the UH spheres. \hfill \\ \end{gathered} $$      

A solution of the exponential integral in the non-isothermal kinetics for linear heating

A simple and satisfactorily accurate solution of the exponential integral in the nonisothermal kinetic equation for linear heating is proposed: $$\mathop \smallint \limits_0^T e^{ - E/RT} dT = \frac{{RT^2 }}{{E + 2RT}}e^{ - E/RT} $$      

Der Einfluss unterschiedlicher Trägheitsmomente auf die Thermodiffusion von H35Cl,D35Cl,H37Cl und D37Cl

The analysis of measurements of the thermal diffusion factor α in the systems H³⁵Cl/H³⁷Cl, D³⁵Cl/D³⁷Cl and H³⁵Cl/D³⁵Cl shows that α may be approximated by the expression α = C_m \frac{{m_1 ? m_2 }}{{m_1 + m_2 }} + C_\theta \frac{{\theta _1 ? \theta _2 }}{{\theta _1 + \theta _2 }}.     

The kinetics of silylation of hydroxylated silica 1: Aerosil

The kinetics of the silylation of hydroxylated silica, the non-porous Aerosil using trimethylchlorosilane, under various reaction conditions has been investigated by a gravimetric technique and found to follow the law:

To the problem of applying the equation of Kolmogorov,Erofeev, Kazeev,Avrami and Mampel to the kinetics of non-isothermal transformations

The possibility of applying the KEKAM equation -In (1?α)=kt ⁿ to the kinetics of non-isothermal transformations is discussed. The derived form of this equation in the shape $$\frac{{d\alpha }}{{dt}} = nk^{1/n} (1 - \alpha )[ - \ln (1 - \alpha )]^{1 - 1/n} ,$$ according to the logic of the reasoning, cannot be applied to kinetic curves under the conditions of programmed heating.     

Some observations on the scaled-particle theory of solutions and the surface tension of solvents

The energy necessary to form a cavity of appropriate size for a solute can be calculated by use of the scaled-particle theory if the effective hard-sphere diameter σ₁ of the solvent is known. A method is presented for obtaining σ₁ for solvents for which gas-solubility data are not available. The method is based on an empirical correlation between the surface tension of the solvent and the function $$\frac{1}{{\sigma _1^2 }}\left[ {\frac{{3y}}{{1 - y}} + \frac{1}{2}{\text{ }}\left( {\frac{{3y}}{{1 - y}}} \right)^2 } \right]$$ a function which appears in expressions for the surface tension and the cavity energy in the scaled-particle theory. Some general observations about the cavity energies for large solutes (≥6 Å diameter) are also made.     

New approximation for the general temperature integral

A new approximation has been proposed for calculation of the general temperature integral $ \int\limits_0^T {T^m } e^{ - E/RT} dT $ \int\limits_0^T {T^m } e^{ - E/RT} dT , which frequently occurs in the nonisothermal kinetic analysis with the dependence of the frequency factor on the temperature (A=A ₀ T ^m). It is in the following form:

Löslichkeit von Nickelferrit in Säuren

The kinetics of the dissolution of nickel ferrite in acids (HCl, HNO₃) was studied. The kinetic equation of the \(\frac{{dx}}{{dt}} = s_0 k (1 - x)^3\) type was derived on the base of the experimental results obtained, and the dissolution rate constantsK andk are calculated.     

Preparation and electrochemical properties of {\hbox{N}}{{\hbox{d}}_{{{2} - x}}}{\hbox{S}}{{\hbox{r}}_x}{\hbox{Fe}}{{\hbox{O}}_{{{4} + \delta }}} cathode materials for intermediate-temperature solid oxide fuel cells

Cathodic materials $ {\hbox{N}}{{\hbox{d}}_{{{2} - x}}}{\hbox{S}}{{\hbox{r}}_x}{\hbox{Fe}}{{\hbox{O}}_{{{4} + \delta }}} $ (x?=?0.5, 0.6, 0.8, 1.0) with K₂NiF₄-type structure, for use in intermediate-temperature solid oxide fuel cells (IT-SOFCs), have been prepared by the glycine?Cnitrate process and characterized by XRD, SEM, AC impedance spectroscopy, and DC polarization measurements. The results have shown that no reaction occurs between an $ {\hbox{N}}{{\hbox{d}}_{{{2} - x}}}{\hbox{S}}{{\hbox{r}}_x}{\hbox{Fe}}{{\hbox{O}}_{{{4} + \delta }}} $ electrode and an Sm_0.2Gd_0.8O_1.9 electrolyte at 1,200?°C, and that the electrode forms a good contact with the electrolyte after sintering at 1,000?°C for 2?h. In the series $ {\hbox{N}}{{\hbox{d}}_{{{2} - x}}}{\hbox{S}}{{\hbox{r}}_x}{\hbox{Fe}}{{\hbox{O}}_{{{4} + \delta }}} $ (x?=?0.5, 0.6, 0.8, 1.0), the composition $ {\hbox{N}}{{\hbox{d}}_{{{1}.0}}}{\hbox{S}}{{\hbox{r}}_{{{1}.0}}}{\hbox{Fe}}{{\hbox{O}}_{{{4} + \delta }}} $ shows the lowest polarization resistance and cathodic overpotential, 2.75????cm² at 700?°C and 68?mV at a current density of 24.3?mA?cm^?2 at 700?°C, respectively. It has also been found that the electrochemical properties are remarkably improved the increasing Sr content in the experimental range.     

Formalkinetische Behandlung des Masseverlustes bei thermischen Abbauprozessen von Polymeren unter nichtisothermen Bedingungen

On the basis of the formal basic relation $$\frac{{d\alpha }}{{dt}} = A \cdot e^ - \frac{E}{{RT}}(1 - \alpha )^n $$ methods of calculating kinetic values from non-isothermal thermogravimetric curves have been critically evaluated. It has been established that in general integral methods are preferable to differential methods. Methods basing on a series expansion of the exponential integral $$\int\limits_0^T {e^ - \frac{{ET}}{{RT}}} dT$$ are applicable without limitations to any cases. It has been concluded that the integral method suggested by Zsakó is the most reliable.     

Electron capture by protons from theK-shell of H and Ar

Whenever a collision takes place between charged particles, the first Born approximation for electron capture from hydrogenlike ions (Z _T ,e) by a bare nucleusZ _P , must be modified in order to account for the long-range Coulomb effects. One of the simplest ways to fulfill this requirement is provided by theT-matrix of the following form: $$T_{if}^{(1)} = \left\langle {\Phi _f exp\left\{ { - i\frac{{Z_T (Z_p - 1)}}{\upsilon } ln (\upsilon R + v \cdot R)} \right\}\left| {\frac{{Z_P }}{R} - \frac{{Z_P }}{{r_P }}} \right| exp\left\{ {i\frac{{Z_P (Z_T - 1)}}{\upsilon } ln (\upsilon R + v \cdot R)} \right\}\Phi _i } \right\rangle $$ where Φ's are the usual unperturbed channel states andZ's are the nuclear charges. In this transition amplitude, both initial and final scattering states satisfy the correct asymptotic boundary conditions in their respective channels. In the present paper, detailed computation of theK-shell cross sections is carried out for charge exchange in H⁺-H and H⁺-Ar collisions. The results are in good agreement with experimental data.     

The correlation between isothermal and non-isothermal kinetics in thermogravimetry

It is shown that the total differential of the function of the amount of conversion versus temperature and time (=f(T, t)) is equal to zero non-isothermal kinetics at constant heating rate. Hence, the mathematical expression used in the literature for the rate of the non-isothermal transformation, , is not valid.     

Elektrometrische Untersuchungen über die Geschwindigkeit der Bildung von Cu2S in ammoniakalischen Lösungen von Cu+-Ionen mittels Thioacetamid, 4. Mitt.

Quantitative studies of the rate of Cu₂S-formation by thioacetamide (TAA) were made with the help of the polarographic method of continuous registration at constant potential, and the following equation for the reaction rate between Cu⁺-ions andTAA in ammoniacal solutions was derived: 1 $$ - \frac{{d[Cu^I ]}}{{dt}} = k \cdot \frac{{[Cu^I ] \cdot [CH_3 CSNH_2 ]}}{{[NH_3 H_2 O]^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$2$}}} \cdot [H^ + ]}}\frac{{^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 4}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$4$}}} }}{{^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 {10}}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{${10}$}}} }} \cdot \frac{{f_{Cu} }}{{f_{H^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 {10}}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{${10}$}}} } }}$$ The value at 25.0° of the rate constantk is (1.6±0.2)·10^?2 mole^7/20·litre^?7/20·sec^?1. The validity of equation (1) has been proved over the pH range 8.5–9.5 and the ammonia concentration of 4.0·10^?2–4.0·10^?1 mole per litre, by only a small excess ofTAA and moderate reaction rates.     

Elektrometrische Untersuchungen über die Ag2S-Bildungsgeschwindigkeit in ammoniakalischen Lösungen von Ag+-Ionen mittels Thioacetamid, 5. Mitt.

On basis of polarographic method of continuous registration at constant potential, the quantitative investigation of the rate of Ag₂S formation by thioacetamide (TAA) was performed and, the following equation for the reaction rate between Ag⁺-ions andTAA in ammoniacal solutions has been derived: 1 $$ - \frac{{d[Ag^I ]}}{{d t}} = k \cdot \frac{{[Ag^I ] \cdot [CH_3 CSNH_2 ]^{1/4} }}{{[H^ + ]^{1/10} }} \cdot \frac{{fAg}}{{f_H^{1/10} }}$$ The value, at 25.0^o, of the rate constantk is (6.8±0.4)· ·10^?2 mole^?3/20·litre^3/20·sec^?1. The validity of equation (1) has been proved over the pH range 8.3–10.8 and the ammonia concentration of 5.6·10^?2–1.0 mole per litre, by only a small excess ofTAA and moderate reaction rates.     

Kinetik und Mechanismus der Oxydation von 1,2,4,5-Tetramethylbenzol in essigsaurem Medium

The liquid phase oxidation of 1.2.4.5-tetramethylbenzene catalysed by cobaltous acetate and promoted by KBr in acetic acid was kinetically studied. In view of deriving the kinetic equation for the absorption of oxygen, a number of experiments were carried out. The values of the activation energy and of the preexponentA=10¹⁴ were determined as well. The resulting kinetic equation: $$ - \frac{{d\left[ {O_2 } \right]}}{{d\tau }} = 10^{14} \cdot \exp \left( { - \frac{{84,460 \times 10^3 }}{{RT}}} \right) \cdot C_{C_6 H_2 (CH_3 )_4 }^{0,5} \cdot C_{Co(OAc)_2 }^{0,5} \cdot C_{KBr}^{0,5} $$ is in accordance with the theoretically derived expression of this type.     

Algorism for the solution of the exponential integral in non-isothermal kinetics at linear heating

The solution of the exponential integral at linear heating for the general case that the activation energy linearly depends on temperature according toE(T)=E ₀+RBT is

Über das polarographische Verhalten der syn- und anti-Isomeren der Ketoxime

Both the syn(α)- and the anti(β)-isomers of 4-chlorobenzophenoneoxime show two polarographic steps; the first is limited by diffusion kinetics, but the second solely by diffusion. As with aldoximes, the limiting current ratioi ₁/i ₂ decreases with increasing concentration of the organic solvent; at equal concentration one can write

$$\left( {\frac{{i_1 }}{{i_2 }}} \right)_\alpha< \left( {\frac{{i_1 }}{{i_2 }}} \right)_\beta $$