scholarly journals The role of calcium ions in the stability and instability of a thermolysin-like protease

2011 ◽  
Vol 20 (8) ◽  
pp. 1346-1355 ◽  
Author(s):  
V. G. H. Eijsink ◽  
B. W. Matthews ◽  
G. Vriend
Keyword(s):  
Calcium Ions ◽  
Stability And Instability ◽  
The Stability

The Role of Calcium in the Isolation of Brush Borders from Epithelial Cells of Rat Small Intestine

1966 ◽  
Vol 1 (4) ◽  
pp. 415-424
Author(s):  
P. F. MILLINGTON ◽  
D. R. CRITCHLEY ◽  
P.W. A. TOVELL
Keyword(s):  
Small Intestine ◽  
Calcium Ions ◽  
Chelating Agent ◽  
Tris Buffer ◽  
Good Separation ◽  
The Third ◽  
Low Concentrations ◽  
Brush Borders ◽  
The Stability

A chelating agent such as EDTA or EGTA used with a dilute TRIS buffer at pH 7.2-7.5 was used in order to effect a good separation of brush borders from the epithelium of the small intestine. A good separation was not obtained in low concentrations of TRIS buffer or saline alone. Brush borders were not obtained when the calcium-chelate complex of EDTA or EGTA was used, and only a partial fractionation was obtained when the magnesium complex of EDTA was tried. The involvement of calcium was further illustrated by adding calcium salts directly to the fractionation medium; separation was prevented when sufficient calcium had been added to saturate the chelating agent. It was found that there was no precise optimum concentration for EDTA but a separation could not be obtained below 2.4 mM/1. The effect of changing the pH of the buffer was also investigated and it was demonstrated that the onset of the ability to release brush borders coincided approximately with the ionization of the third acid radical of the chelating agent. This is in keeping with the suggested hypothesis that EDTA acts by chelating calcium ions. From these and electron-microscope studies it is suggested that the binding of calcium ions is an important factor in the maintenance of the stability of the epithelial cell membrane.

Determinism and Stability in Physics

2018 ◽  
pp. 61-81
Author(s):  
Yemima Ben-Menahem
Keyword(s):  
Quantum Mechanics ◽  
Statistical Mechanics ◽  
Chaos Theory ◽  
Physical Sciences ◽  
Stability And Instability ◽  
Conceptual Relations ◽  
The Stability

This chapter examines the role of stability and determinism in physical theories such as statistical mechanics. In the physical sciences, the notions of stability and instability, no longer camouflaged in the language of necessity and contingency, are often used in a variety of contexts, from chaos theory to quantum mechanics. Physicists consider questions about the stability of states, orbits, and structures to be as fundamental as questions about determinism. Before expounding on the conceptual relations between stability and determinism in physics, the chapter discusses three interconnected problems that statistical mechanics has had to tackle: the meaning of probability in statistical mechanics, the link between probability and a system's dynamics, and the origin of directionality. It shows that the notions of determinism and stability are often conflated, giving rise to teleological thinking.

scholarly journals A fluorimetric study of the role of calcium ions in the stability of thermolysin

1977 ◽  
Vol 165 (3) ◽  
pp. 539-545 ◽  
Author(s):  
Angelo Fontana ◽  
Claudio Vita ◽  
Enrico Boccu' ◽  
Francesco M. Veronese
Keyword(s):  
Calcium Ions ◽  
Fluorescence Emission ◽  
Protein Molecule ◽  
Fluorescence Emission Spectrum ◽  
Guanidinium Chloride ◽  
Emission Maximum ◽  
Heat Stable ◽  
Tryptophan Residues ◽  
The Stability

1. Fluorimetric techniques were used to characterize the environment of tryptophan residues in thermolysin and apo-thermolysin. The apo-thermolysin was obtained by dissolving the enzyme in the presence of 10mm-EDTA, which removed the functional Zn2+ ion and the four Ca2+ ions/molecule from the enzyme. 2. At 25°C in aqueous solution the fluorescence-emission spectrum of the native holoenzyme, on excitation at 290nm, was essentially characteristic of tryptophan, with an emission maximum at 333nm. The emission maximum of the apoenzyme is red-shifted to 338nm and the relative intensity of fluorescence is decreased by 10%, both effects indicating some unfolding of the protein molecule, with the indole groups being transferred to a more hydrophilic environment. 3. Fluorescence quenching studies using KI, N′-methylnicotinamide hydrochloride and acrylamide indicated a more open structure in the apoenzyme, with the tryptophan residues located in a negatively charged environment. 4. The thermal properties of the apoenzyme, as monitored by fluorescence-emission measurements, are dramatically changed with respect to the native holoenzyme. In fact, whereas the native enzyme is heat-stable up to about 80°C, for the apoenzyme a thermal transition is observed near 48°C. The apoenzyme is also unstable to the action of unfolding agents such as urea and guanidinium chloride, much as for other globular proteins from mesophilic organisms. 5. The functional Zn2+ ion does not contribute noticeably to the stability of thermolysin. 6. It is concluded that a major role in the structural stability of thermolysin is played by the Ca2+ ions, which have a bridging function within this disulphide-free protein molecule.

The Effects of Collisions with Neutral Particles on the Instability of Two Superposed Composite Plasmas Streaming Through Porous Medium

1999 ◽  
Vol 54 (6-7) ◽  
pp. 411-416 ◽  
Author(s):  
Mohamed Fahmy El-Sayed
Keyword(s):  
Porous Medium ◽  
Unstable Mode ◽  
Instability Criterion ◽  
Stable Configuration ◽  
Neutral Particles ◽  
Fluid Velocities ◽  
Stability And Instability ◽  
The Stability ◽  
The Magnetic Field

Abstract The effects of collisions with neutral atoms on the hydromagnetic stability of the plane interface separating two streaming superposed composite plasmas of uniform densities in a porous medium are investigated. In the absence of fluid velocities, it is found, for a potentially stable configuration, that the system remains stable, while for a potentially unstable configuraion, the unstable system becomes stable under a certain condition of the wavenumber depending on the values of the fluid densities, Alfvén velocities, and the orientation of the magnetic field. The porosity of the porous medium does not have any significant effect on the stability criterion. In the presence of fluid velocities, it is found that, the instability criterion is independent of the permeability of the medium and the collision effects with neutral particles. The criterion determing the stability does not depend on the permeability of the medium but depends on the density of neutral particles. The porosity of the medium is found to have a significant effect on both the stability and instability criteria in this case. The role of the permeability of the medium, the collisional frequency, and the porosity of the porous medium on the growth rate of the unstable mode is examined analitically. Routh’s test of stability is applied to confirm the above results.

Mitochondrial matrix calcium ions regulate energy production in myocardium: A cytochemical study

1990 ◽  
Vol 48 (2) ◽  
pp. 166-167
Author(s):  
W.A. Jacob ◽  
R. Hertsens ◽  
A. Van Bogaert ◽  
M. De Smet
Keyword(s):  
Energy Metabolism ◽  
Calcium Ions ◽  
Energy Production ◽  
Regulation Of Respiration ◽  
Free Calcium ◽  
Mitochondrial Matrix ◽  
Cytochemical Study ◽  
Nmr Techniques

In the past most studies of the control of energy metabolism focus on the role of the phosphorylation potential ATP/ADP.Pi on the regulation of respiration. Studies using NMR techniques have demonstrated that the concentrations of these compounds for oxidation phosphorylation do not change appreciably throughout the cardiac cycle and during increases in cardiac work. Hence regulation of energy production by calcium ions, present in the mitochondrial matrix, has been the object of a number of recent studies.Three exclusively intramitochondnal dehydrogenases are key enzymes for the regulation of oxidative metabolism. They are activated by calcium ions in the low micromolar range. Since, however, earlier estimates of the intramitochondnal calcium, based on equilibrium thermodynamic considerations, were in the millimolar range, a physiological correlation was not evident. The introduction of calcium-sensitive probes fura-2 and indo-1 made monitoring of free calcium during changing energy metabolism possible. These studies were performed on isolated mitochondria and extrapolation to the in vivo situation is more or less speculative.

A Statistical Study of Process Variables to Optimize a High Speed Curtain Coater: Part I

TAPPI Journal ◽  
2009 ◽  
Vol 8 (1) ◽  
pp. 20-26 ◽  
Author(s):  
PEEYUSH TRIPATHI ◽  
MARGARET JOYCE ◽  
PAUL D. FLEMING ◽  
MASAHIRO SUGIHARA
Keyword(s):  
Boundary Layer ◽  
Experimental Design ◽  
High Speed ◽  
Statistical Study ◽  
Process Variables ◽  
High Speeds ◽  
The Stability ◽  
Air Removal ◽  
Removal System

Using an experimental design approach, researchers altered process parameters and material prop-erties to stabilize the curtain of a pilot curtain coater at high speeds. Part I of this paper identifies the four significant variables that influence curtain stability. The boundary layer air removal system was critical to the stability of the curtain and base sheet roughness was found to be very important. A shear thinning coating rheology and higher curtain heights improved the curtain stability at high speeds. The sizing of the base sheet affected coverage and cur-tain stability because of its effect on base sheet wettability. The role of surfactant was inconclusive. Part II of this paper will report on further optimization of curtain stability with these four variables using a D-optimal partial-facto-rial design.

The identity policy and its effect in the stability of Middle East after 2010

2019 ◽  
pp. 434
Author(s):  
Ali Hussein Kadhim Alesammi
Keyword(s):  
Middle East ◽  
International Relations ◽  
Social Construct ◽  
Stability And Instability ◽  
The Social ◽  
The Stability ◽  
International Interactions ◽  
Regional Interests ◽  
Political Groups ◽  
Identity Policy

Since 2010 Middle East have many events or what they call "Arab spring events" which it result of overthrow governments and the rise of new political groups, all of this elements was resulting of many international and regional activities and making new regional and international axles, as well as the intersections of the different regional interests, therefore this research will try to study the stability and instability in the region as an independent variable not according to the neorealism or neoliberalism theories, but according to the constructivism theory which it base their assumptions on:  "In the international relations the non-physical structures of international interactions are determined by the identities of the players, which in turn determine the interests that determine the behavior of international players." So the research questions are: 1-What is the identity policy and haw affect in international relations? 2-How the social construct affect in international relations? 3-How the elite's identities for the main actors in the Middle East affect in the regional axles?  

The Role of Hydrophobicity in the Stability and pH-Switchability of (RXDX)4 and Coumarin-RXDX Conjugate β-Sheets

2020 ◽  
Author(s):  
Ryan Weber ◽  
Martin McCullagh
Keyword(s):  
Biological Imaging ◽  
Ph Sensing ◽  
Hydrophobic Residue ◽  
Ideal Candidate ◽  
Self Assembling ◽  
Sensing Applications ◽  
Β Sheets ◽  
The Stability ◽  
Dynamics Simulations

<p>pH-switchable, self-assembling materials are of interest in biological imaging and sensing applications. Here we propose that combining the pH-switchability of RXDX (X=Ala, Val, Leu, Ile, Phe) peptides and the optical properties of coumarin creates an ideal candidate for these materials. This suggestion is tested with a thorough set of all-atom molecular dynamics simulations. We first investigate the dependence of pH-switchabiliy on the identity of the hydrophobic residue, X, in the bare (RXDX)<sub>4</sub> systems. Increasing the hydrophobicity stabilizes the fiber which, in turn, reduces the pH-switchabilty of the system. This behavior is found to be somewhat transferable to systems in which a single hydrophobic residue is replaced with a coumarin containing amino acid. In this case, conjugates with X=Ala are found to be unstable and both pHs while conjugates with X=Val, Leu, Ile and Phe are found to form stable β-sheets at least at neutral pH. The (RFDF)<sub>4</sub>-coumarin conjugate is found to have the largest relative entropy value of 0.884 +/- 0.001 between neutral and acidic coumarin ordering distributions. Thus, we posit that coumarin-(RFDF)<sub>4</sub> containing peptide sequences are ideal candidates for pH-sensing bioelectronic materials.</p>

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