scholarly journals Activation of brain hexokinase by magnesium ions and by magnesium ion–adenosine triphosphate complex

1972 ◽  
Vol 130 (1) ◽  
pp. 63-69 ◽  
Author(s):  
Daniel L. Purich ◽  
Herbert J. Fromm
Keyword(s):  
Simple Model ◽  
Complex Formation ◽  
Kinetic Data ◽  
Alternative Explanation ◽  
Metal Substrate ◽  
Magnesium Ion ◽  
Magnesium Ions ◽  
Substrate Complex ◽  
The Brain ◽  
Hill Plots

1. An alternative explanation for the kinetic data obtained by Bachelard (1971) for the brain hexokinase reaction is presented. 2. Apparently sigmoidal saturation curves for MgATP2− based upon Bachelard's (1971) studies can be corrected to hyperbolic curves by use of a stability constant for MgATP2− complex formation. 3. A number of other effects related to the concentration-dependent stability of the MgATP2− complex and to the presence of the inhibitory free uncomplexed ATP4− concentration are also explained in terms of a non-allosteric role for either Mg2+ or MgATP2− fully consistent with a number of previous reports on this enzyme. 4. A brief discussion of the validity of Hill plots in studies of multisubstrate co-operative enzymes is presented. 5. A simple model is presented that demonstrates how enzymes obeying Michaelis–Menten kinetics can demonstrate sigmoidal velocity responses if the true substrate of the reaction is the metal–substrate complex.

scholarly journals Allosteric activation of brain hexokinase by magnesium ions and by magnesium-ion–adenosine triphosphate complex

1971 ◽  
Vol 125 (1) ◽  
pp. 249-254 ◽  
Author(s):  
H. S. Bachelard
Keyword(s):  
Binding Sites ◽  
Magnesium Ion ◽  
Magnesium Ions ◽  
Allosteric Activation ◽  
Substrate Saturation ◽  
Number Of Binding Sites ◽  
High Concentrations ◽  
Substrate Binding Sites ◽  
Hill Plots ◽  
Allosteric Activator

1. Substrate-saturation curves of brain hexokinase for MgATP2− were sigmoidal at sub-saturating concentrations of glucose when the Mg2+/ATP ratio was maintained at 1:1. Under identical conditions, except that Mg2+ was present in excess, hyperbolic curves were observed. 2. The number of binding sites (calculated from Hill plots) is 1.8 at a Mg2+/ATP ratio 1:1, and 1.0 with excess of Mg2+. The apparent Km for MgATP2− is 6.5×10−4m at a Mg2+/ATP ratio 1:1, and 3.5×10−4m with excess of Mg2+. 3. Interdependence between substrate-binding sites was indicated by the effects of varying the concentration of glucose. The sigmoidality and deviation from Michaelis–Menten kinetics at a Mg2+/ATP ratio 1:1 became less pronounced with increasing glucose concentration. Also, although substrate-saturation curves for glucose were hyperbolic when the Mg2+/ATP ratio was 1:1, reciprocal plots were non-linear. These were linear with excess of Mg2+. 4. High concentrations of Mg2+ (Mg2+/ATP ratios above 5:1) were inhibitory. 5. The results are taken to indicate homotropic co-operative binding of MgATP2− and that Mg2+ is an allosteric activator. Possible implications in regulation are discussed.

scholarly journals The Force Cone Method Applied to Explain Hidden Whirls in Tribology

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3894
Author(s):  
Claus Mattheck ◽  
Christian Greiner ◽  
Klaus Bethge ◽  
Iwiza Tesari ◽  
Karlheinz Weber
Keyword(s):  
Finite Element ◽  
Free Surface ◽  
Simple Model ◽  
Alternative Explanation ◽  
Model Experiments ◽  
Complex Processes ◽  
Buried Interfaces ◽  
Internal Structures ◽  
Ideal Tool ◽  
Acting Force

In tribologically loaded materials, folding instabilities and vortices lead to the formation of complex internal structures. This is true for geological as well as nanoscopic contacts. Classically, these structures have been described by Kelvin–Helmholtz instabilities or shear localization. We here introduce an alternative explanation based on an intuitive approach referred to as the force cone method. It is considered how whirls are situated near forces acting on a free surface of an elastic or elastoplastic solid. The force cone results are supplemented by finite element simulations. Depending on the direction of the acting force, one or two whirls are predicted by the simplified force cone method. In 3D, there is always a ring shaped whirl present. These modelling findings were tested in simple model experiments. The results qualitatively match the predictions and whirl formation was found. The force cone method and the experiments may seem trivial, but they are an ideal tool to intuitively understand the presence of whirls within a solid under a tribological load. The position of these whirls was found at the predicted places and the force cone method allows a direct approach to understand the complex processes in the otherwise buried interfaces of tribologically loaded materials.

A Study on the Influence of Cysteine and Magnesium Ions on Brain Dementia

2014 ◽  
Vol 487 ◽  
pp. 161-164
Author(s):  
Lu Yin ◽  
Shuang Yue Zhu
Keyword(s):  
Vascular Dementia ◽  
Plasma Homocysteine ◽  
Diagnosis And Treatment ◽  
Magnesium Ion ◽  
Disease Development ◽  
Mechanism Analysis ◽  
Magnesium Ions ◽  
Patients Âgés ◽  
Dementia Patients ◽  
Relationship Of

As the population ages, dementia disease is increasingly becoming the most concerned social problems. According to the cause of dementia, it can be divided into many kinds class, among them with Alzheimer's Disease (Alzheimers diseases, AD) and Vascular Dementia (Vascular Dementia, VD) are common. Data shows it accounts for nearly 60% of total AD dementia patients, VD (20%), but only 2% of patients could get timely diagnosis and treatment, make its cognitive damage to a certain extent suppress and improve. for untimely diagnosis and treatment, most patients makes the disease development worse. In recent years, studies have shown that plasma Homocysteine,Hcy levels associated with AD. And studies show that from the power of the risk factors to the mechanism analysis, dementia disease level correlation with magnesium ions. On this basis, this study of plasma homocysteine in patients with AD,VD and magnesium ion detection results were analyzed retrospectively. Discuss their levels between the distributio relationship of patients ages in AD and VD.

scholarly journals Williams Syndrome As a Model for Elucidation of the Pathway Genes - the Brain - Cognitive Functions: Genetics and Epigenetics

Acta Naturae ◽  
2014 ◽  
Vol 6 (1) ◽  
pp. 9-22 ◽  
Author(s):  
Е. А. Nikitina ◽  
A. V. Medvedeva ◽  
G. А. Zakharov ◽  
Е. V. Savvateeva-Popova
Keyword(s):  
Simple Model ◽  
Williams Syndrome ◽  
Cognitive Functions ◽  
Single Gene ◽  
Model Systems ◽  
Epigenetic Events ◽  
Simple Model System ◽  
And Behavior ◽  
Brain Behavior ◽  
The Brain

Genomic diseases or syndromes with multiple manifestations arise spontaneously and unpredictably as a result of contiguous deletions and duplications generated by unequal recombination in chromosomal regions with a specific architecture. The Williams syndrome is believed to be one of the most attractive models for linking genes, the brain, behavior and cognitive functions. It is a neurogenetic disorder resulting from a 1.5 Mb deletion at 7q11.23 which covers more than 20 genes; the hemizigosity of these genes leads to multiple manifestations, with the behavioral ones comprising three distinct domains: 1) visuo-spatial orientation; 2) verbal and linguistic defect; and 3) hypersocialisation. The shortest observed deletion leads to hemizigosity in only two genes: eln and limk1. Therefore, the first gene is supposed to be responsible for cardiovascular pathology; and the second one, for cognitive pathology. Since cognitive pathology diminishes with a patients age, the original idea of the crucial role of genes straightforwardly determining the brains morphology and behavior was substituted by ideas of the brains plasticity and the necessity of finding epigenetic factors that affect brain development and the functions manifested as behavioral changes. Recently, non-coding microRNAs (miRs) began to be considered as the main players in these epigenetic events. This review tackles the following problems: is it possible to develop relatively simple model systems to analyze the contribution of both a single gene and the consequences of its epigenetic regulation in the formation of the Williams syndromes cognitive phenotype? Is it possible to use Drosophila as a simple model system?

Optical Biosensors Based on Enzyme-Substrate Complex Formation

1994 ◽  
pp. 129
Author(s):  
D.A. Moss ◽  
A. Ritter ◽  
W. Andlauer ◽  
H.J. Ache
Keyword(s):  
Complex Formation ◽  
Optical Biosensors ◽  
Substrate Complex ◽  
Enzyme Substrate

Transient-Phase and Steady-State Kinetics for Enzyme Activation

1973 ◽  
Vol 51 (6) ◽  
pp. 806-814 ◽  
Author(s):  
Nasrat H. Hijazi ◽  
Keith J. Laidler
Keyword(s):  
Steady State ◽  
Kinetic Data ◽  
Enzyme Activation ◽  
Transient Phase ◽  
Time Curve ◽  
Substrate Complex ◽  
Enzyme Substrate ◽  
Substrate Activation ◽  
Steady State Kinetics ◽  
Special Case

A non-steady-state analysis has been worked out for two mechanisms in which an activator Q can become attached to an enzyme–substrate complex EA, the species EAQ breaking down more rapidly than EA. It is shown that if EAQ breaks down into EQ + product there can be no steady state. If, however, EAQ breaks down into E + Q + product, the transient phase is followed by a steady state in which the product versus time curve is linear. A special case of this mechanism is when Q is the substrate (substrate activation). Some published kinetic data on carboxypeptidase are analyzed with reference to the equations derived.

scholarly journals A method for extracting rate constants from initial rates of stopped-flow kinetic data: application to a physiological electron-transfer reaction

1993 ◽  
Vol 294 (1) ◽  
pp. 211-213 ◽  
Author(s):  
H B Brooks ◽  
V L Davidson
Keyword(s):  
Electron Transfer ◽  
Rate Constants ◽  
Kinetic Data ◽  
Transfer Reaction ◽  
Dissociation Constants ◽  
Accurate Method ◽  
Electron Transfer Reaction ◽  
Stopped Flow ◽  
Methylamine Dehydrogenase ◽  
Substrate Complex

The most commonly used methods for analysis of stopped-flow kinetic data require performing a series of measurements in which one reactant is varied at concentrations significantly greater than the concentration of the other reactant. For enzyme-catalysed reactions this may not be possible, because the dissociation constants for the enzyme-substrate complex are often of the same order of magnitude as the high concentrations of enzyme that must frequently be used in stopped-flow studies. An alternative method of data analysis is presented which allows the determination of microscopic rate constants from initial rates of stopped-flow kinetic data in which substrate is varied in a range of concentrations approximately the same as the enzyme. This method also provides a simple and accurate method for determining k4, the rate of the reverse reaction. This method has been used to describe a physiological electron transfer reaction between a quinoprotein, methylamine dehydrogenase, and a copper protein, amicyanin. At 20 degrees C, the rate of the electron-transfer reaction from methylamine dehydrogenase to amicyanin was 24 s-1, and the dissociation constant for complex-formation was 1.9 microM.

scholarly journals The process of magnesium ion modification of titanium surface and the sustained-release of magnesium ions from its surface

2020 ◽  
Vol 39 (3) ◽  
pp. 509-516
Author(s):  
Hanako SAKATSUME ◽  
Masatoshi TAKAHASHI ◽  
Mary Wambui KANYI ◽  
Yoshinaka SHIMIZU ◽  
Yukyo TAKADA
Keyword(s):  
Sustained Release ◽  
Titanium Surface ◽  
Magnesium Ion ◽  
Magnesium Ions ◽  
Modification Of Titanium
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