scholarly journals Studies on the mechanism and kinetics of the 2-oxoglutarate dehydrogenase system from pig heart

1977 ◽  
Vol 161 (3) ◽  
pp. 569-581 ◽  
Author(s):  
C L McMinn ◽  
J H Ottaway
Keyword(s):  
Initial Rate ◽  
Optimization Technique ◽  
Random Order ◽  
The Other ◽  
Rate Equations ◽  
Kinetic Properties ◽  
Ping Pong ◽  
System 2 ◽  
Dehydrogenase System ◽  
Oxoglutarate Dehydrogenase

1. The kinetic properties of the 2-oxoglutarate dehydrogenase system were investigated. To this end, initial-velocity studies were carried out by the method of Fromm [(1967) Biochim. Biophys. Acta 139, 221-230]. Reciprocal plots of the results did not agree with those expected for the Hexa Uni Ping Pong mechanism previously proposed for the system. 2. The measured initial velocities were fitted to initial-rate equations corresponding to several possible mechanisms by using a computer optimization technique. Statistical analyses performed on the results of the optimization studies indicated that one mechanism was a significantly better fit to the experimental data than the other mechanisms tested. This mechanism is one in which there is a random order of binding of NAD+ and CoA and release of succinyl-CoA, although the binding of 2-oxoglutarate and release of CO2 is still given a Ping Pong mechanism, which precedes the binding of the other substrates. These conclusions were supported by NADH-inhibition studies. 3. The usefulness of the method of fitting initial-rate data to rate equations and the applicability of the proposed enzymic mechanism to the enzyme complex are discussed.

scholarly journals Theoretical and Experimental Considerations for a Rapid and High Throughput Measurement of Catalase In Vitro

Antioxidants ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 21
Author(s):  
Ouardia Bendou ◽  
Ismael Gutiérrez-Fernández ◽  
Emilio L. Marcos-Barbero ◽  
Nara Bueno-Ramos ◽  
Ana I. González-Hernández ◽  
...  
Keyword(s):  
High Throughput ◽  
Catalase Activity ◽  
Initial Rate ◽  
Low Cost ◽  
Rate Equations ◽  
Small Scale ◽  
Kinetic Properties ◽  
H2o2 Decomposition ◽  
Suicide Inactivation

A rapid and high throughput protocol to measure the catalase activity in vitro has been designed. Catalase is an enzyme with unusual kinetic properties because it does not follow the standard Michaelis–Menten model and is inactivated by H2O2. This makes the analysis of the two rate equations of the second-ordered reactions of the kinetic model rather complex. A two-degree polynomial fitting of the experimental data is proposed after transforming the exponential form of the integrated rate equation of the [H2O2] into a polynomial using the Taylor series. The fitting is validated by establishing an experimental linear relationship between the initial rate of the H2O2 decomposition and the protein concentration, regardless of the suicide inactivation that catalase might undergo beyond t > 0. In addition, experimental considerations are taken into account to avoid statistical bias in the analysis of the catalase activity. ANOVA analyses show that the proposed protocol can be utilized to measure the initial rate of the H2O2 decomposition by catalase in 32 samples in triplicates if kept below 8 mM min−1 in the microplate wells. These kinetic and statistical analyses can pave the way for other antioxidant enzyme activity assays in microplate readers at small scale and low cost.

scholarly journals Purification and some kinetic properties of rat liver glucosamine synthetase

1971 ◽  
Vol 121 (4) ◽  
pp. 701-709 ◽  
Author(s):  
P. J. Winterburn ◽  
C. F. Phelps
Keyword(s):  
Rat Liver ◽  
Rate Equation ◽  
Protective Action ◽  
The Other ◽  
Kinetic Properties ◽  
Ph Optimum ◽  
Ph Values ◽  
Catalysed Reaction ◽  
Ping Pong ◽  
Feedback Inhibitor

1. Glucosamine synthetase (l-glutamine–d-fructose 6-phosphate aminotransferase, EC 2.6.1.16) was purified about 300-fold from rat liver by two techniques. One procedure utilized the protective action of fructose 6-phosphate and gave a relatively stable preparation, the other yielded an unstable enzyme (half-life of about 20h), free of contaminant activities, on which kinetic experiments were performed. Although the properties of the two preparations showed slight differences, the unstabilized form could be converted into the stabilized form. 2. During preparation the enzyme retained its sensitivity to the feedback inhibitor, UDP-N-acetylglucosamine. 3. The reversibility of the enzyme-catalysed reaction could not be demonstrated. There was no apparent requirement for a cofactor. 4. The pH optimum was at 7.5, at which pH the reaction obeyed a Ping Pong Bi Bi rate equation. At pH values outside the range 6.9–7.6 and at temperatures below 29°C the velocity was described by an ordered Bi Bi rate equation. 5. The molecular weight of the enzyme, determined by two procedures, was 360000–400000. 6. The aminotransferase was unable to utilize ammonia as a substrate.

A polycentric growth model of gallium arsenide epitaxial layers from the gas phase with simultaneous diffusion, adsorption and chemical reaction

1988 ◽  
Vol 53 (12) ◽  
pp. 2995-3013
Author(s):  
Emerich Erdös ◽  
Jindřich Leitner ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma
Keyword(s):  
Growth Rate ◽  
Gallium Arsenide ◽  
Epitaxial Growth ◽  
Gas Phase ◽  
Surface Reaction ◽  
Quantitative Description ◽  
The Other ◽  
Rate Equations ◽  
Impact Interaction ◽  
Partial Pressures

For a quantitative description of the epitaxial growth rate of gallium arsenide, two models are proposed including two rate controlling steps, namely the diffusion of components in the gas phase and the surface reaction. In the models considered, the surface reaction involves a reaction triple - or quadruple centre. In both models three mechanisms are considered which differ one from the other by different adsorption - and impact interaction of reacting particles. In every of the six cases, the pertinent rate equations were derived, and the models have been confronted with the experimentally found dependences of the growth rate on partial pressures of components in the feed. The results are discussed with regard to the plausibility of individual mechanisms and of both models, and also with respect to their applicability and the direction of further investigations.

Expressive Microstructure in Music: A Preliminary Perceptual Assessment of Four Composers' "Pulses"

1989 ◽  
Vol 6 (3) ◽  
pp. 243-273 ◽  
Author(s):  
Bruno H. Repp
Keyword(s):  
Classical Music ◽  
Random Order ◽  
Preliminary Test ◽  
The Other ◽  
Musical Experience ◽  
General Music ◽  
Cyclic Patterns ◽  
Computer Controlled ◽  
Perceptual Assessment ◽  
Essential Prerequisite

According to a provocative theory set forth by Manfred Clynes, there are composer-specific cyclic patterns of (unnotated) musical microstructure that, when discovered and realized by a performer, help to give the music its characteristic expressive quality. Clynes, relying mainly on his own judgment as an experienced musician, has derived such personal "pulses" for several famous composers by imposing time and amplitude perturbations on computer-controlled performances of classical music and modifying them until they converged on some optimal expression. To conduct a preliminary test of the general music lover's appreciation of such "pulsed" performances, two sets of piano pieces by Beethoven, Haydn, Mozart, and Schubert, one in quadruple and the other in triple meter, were selected for this study. Each piece was synthesized with each composer's pulse and also without any pulse. These different versions were presented in random order to listeners of varying musical sophistication for preference judgments relative to the unpulsed version. There were reliable changes in listeners' pulse preferences across different composers' pieces, which affirms one essential prerequisite of Clynes' theory. Moreover, in several instances the "correct" pulse was preferred most, which suggests not only that these pulse patterns indeed capture composer- specific qualities, but also that listeners without extensive musical experience can appreciate them. In other cases, however, listeners' preferences were not as expected, and possible causes for these deviations are discussed.

Oxidation of combined ingestion of glucose and fructose during exercise

2004 ◽  
Vol 96 (4) ◽  
pp. 1277-1284 ◽  
Author(s):  
Roy L. P. G. Jentjens ◽  
Luke Moseley ◽  
Rosemary H. Waring ◽  
Leslie K. Harding ◽  
Asker E. Jeukendrup
Keyword(s):  
Power Output ◽  
Statistical Significance ◽  
Random Order ◽  
Carbohydrate Oxidation ◽  
Maximum Power ◽  
The Other ◽  
Cycling Exercise ◽  
Oxidation Rates ◽  
Maximum Power Output ◽  
Exercise Period

The purpose of the present study was to examine whether combined ingestion of a large amount of fructose and glucose during cycling exercise would lead to exogenous carbohydrate oxidation rates >1 g/min. Eight trained cyclists (maximal O2consumption: 62 ± 3 ml·kg-1·min-1) performed four exercise trials in random order. Each trial consisted of 120 min of cycling at 50% maximum power output (63 ± 2% maximal O2consumption), while subjects received a solution providing either 1.2 g/min of glucose (Med-Glu), 1.8 g/min of glucose (High-Glu), 0.6 g/min of fructose + 1.2 g/min of glucose (Fruc+Glu), or water. The ingested fructose was labeled with [U-13C]fructose, and the ingested glucose was labeled with [U-14C]glucose. Peak exogenous carbohydrate oxidation rates were ∼55% higher ( P < 0.001) in Fruc+Glu (1.26 ± 0.07 g/min) compared with Med-Glu and High-Glu (0.80 ± 0.04 and 0.83 ± 0.05 g/min, respectively). Furthermore, the average exogenous carbohydrate oxidation rates over the 60- to 120-min exercise period were higher ( P < 0.001) in Fruc+Glu compared with Med-Glu and High-Glu (1.16 ± 0.06, 0.75 ± 0.04, and 0.75 ± 0.04 g/min, respectively). There was a trend toward a lower endogenous carbohydrate oxidation in Fruc+Glu compared with the other two carbohydrate trials, but this failed to reach statistical significance ( P = 0.075). The present results demonstrate that, when fructose and glucose are ingested simultaneously at high rates during cycling exercise, exogenous carbohydrate oxidation rates can reach peak values of ∼1.3 g/min.

scholarly journals Unification of Graphs and Relations in Mizar

2020 ◽  
Vol 28 (2) ◽  
pp. 173-186
Author(s):  
Sebastian Koch
Keyword(s):  
Binary Relation ◽  
The Other ◽  
Other Hand ◽  
System 2 ◽  
Definition Of

Summary A (di)graph without parallel edges can simply be represented by a binary relation of the vertices and on the other hand, any binary relation can be expressed as such a graph. In this article, this correspondence is formalized in the Mizar system [2], based on the formalization of graphs in [6] and relations in [11], [12]. Notably, a new definition of createGraph will be given, taking only a non empty set V and a binary relation E ⊆ V × V to create a (di)graph without parallel edges, which will provide to be very useful in future articles.

The Philosophy of African Logic

2017 ◽  
pp. 96-121
Author(s):  
Jonathan O. Chimakonam
Keyword(s):  
Formal System ◽  
Cultural Influence ◽  
Formal Logic ◽  
Cross Cultural ◽  
The Other ◽  
Prototype System ◽  
African Philosophy ◽  
System 2 ◽  
The One ◽  
Universal Applicability

The chapter aims to do two things: 1) a rigorous presentation of philosophy of African logic and 2) to do this from the perspective of Ezumezu (an African) logic. The chapter will proceed by defining the three aspects of Ezumezu logic namely: 1) as a formal system, 2) as methodology, and 3) as a philosophy of African logic. My inquiry in this work primarily is with the philosophy of African logic but it will also cut across formal logic and methodology in addition. In the first section, I will attempt to show how the cultural influence behind the formulation of the principles of African logic justifies such a system as relative on the one hand, and how the cross-cultural applications justify it as universal on the other. I believe that this is where African philosophical assessment of African logic ought to begin because most critics of the idea of African logic agitate that an African system of logic, if it is ever possible, must necessarily lack the tincture of universal applicability. Afterwards, I will narrow my inquiry down to the African philosophy appraisal of African logic with an example of Ezumezu system. This focus is especially critical because it purveys a demonstration of a prototype system of an African logic. In the section on some principles of Ezumezu logic, I will attempt to accomplish the set goal of this chapter by presenting and discussing some principles of Ezumezu logic which I had formulated in earlier works in addition to formulating a few additional ones. The interesting thing to note here is that these principles are/will all (be) articulated from the African background ontology. I will conclude by throwing further light on the merits, nature and promises of an African logic tradition.

Derivation of Initial Rate Equations for Low-temperature Water Gas Shift Reaction over Pt–Re/ZrO2Catalysts

2010 ◽  
Vol 39 (2) ◽  
pp. 144-145 ◽  
Author(s):  
Hajime Iida ◽  
Takumi Yamamoto ◽  
Masaru Inagaki ◽  
Akira Igarashi
Keyword(s):  
Low Temperature ◽  
Initial Rate ◽  
Water Gas Shift ◽  
Rate Equations ◽  
Water Gas Shift Reaction ◽  
Shift Reaction ◽  
Water Gas ◽  
Temperature Water

Rapidreaction between unifunctional molecules and molecules unifunctional at one position and n-functional at another

1957 ◽  
Vol 10 (2) ◽  
pp. 99 ◽  
Author(s):  
HG Higgins
Keyword(s):  
The Other ◽  
Rate Equations ◽  
Amino Group

Rate equations for the reaction between A and B, where B is unifunctional, and A is unifunctional at one and n-functional at the other of two independent positions, lead to expressions for the final relative concentrations of the reactants and products in terms of the initial concentrations of A and B, the ratio of the velocity constants at the two positions on A, and the functionality n. These results are applied to the reaction of tryptophane with p-diazobenzenesulphonic acid, in which it appears that the indole group reacts somewhat faster than the amino group.

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