scholarly journals THE KINETICS OF PENETRATION

1930 ◽  
Vol 13 (6) ◽  
pp. 695-713 ◽  
Author(s):  
A. G. Jacques ◽  
W. J. V. Osterhout
Keyword(s):  
Living Cells ◽  
Low Ph ◽  
External Concentration ◽  
Time Curve ◽  
Rate Of Penetration ◽  
Velocity Constant ◽  
First Order ◽  
Ph Values ◽  
Concentration Of Ions ◽  
Kinetics Of

The rate of penetration of CO2 into living cells of Valonia has been studied at high and low pH values. The time curve of penetration appears to be of the first order but with a "velocity constant" which falls off from the start. The evidence indicates little penetration of ions. This is shown by (a) the similarity of velocity "constants" at high and low pH values, (b) the rate of penetration, which remains constant as long as the external concentration of undissociated CO2 remains constant no matter how much the concentration of ions varies.

scholarly journals THE PERMEABILITY OF LIVING CELLS TO DYES AS AFFECTED BY HYDROGEN ION CONCENTRATION

1922 ◽  
Vol 5 (2) ◽  
pp. 223-224 ◽  
Author(s):  
Marian Irwin
Keyword(s):  
Living Cell ◽  
Quantitative Method ◽  
Living Cells ◽  
Low Ph ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Rate Of Penetration ◽  
Cresyl Blue ◽  
Ph Values

1. An accurate quantitative method of measuring the penetration of dye into the living cell is described. 2. Cresyl blue is unable to penetrate rapidly unless the pH outside the cell is decidedly greater than that inside. The rate of penetration increases with increasing pH. 3. Around pH 9 penetration of the dye is rapid while the reverse is true of exosmosis. At low pH values (5.9) exosmosis is rapid and penetration is very slow.

Spectrochemical Behavior of Carcinogenic Polycyclic Aromatic Hydrocarbons in Biological Systems. Part II: A Theoretical Rate Model for BaP Metabolism in Living Cells

1996 ◽  
Vol 50 (11) ◽  
pp. 1352-1359 ◽  
Author(s):  
Ping Chiang ◽  
Kuang-Pang Li ◽  
Tong-Ming Hseu
Keyword(s):  
Rate Constant ◽  
Living Cells ◽  
Rate Model ◽  
Number Density ◽  
Order Process ◽  
Irreversible Reaction ◽  
First Order ◽  
Metabolism Rate ◽  
Polycyclic Aromatic ◽  
Kinetics Of

An idealized model for the kinetics of benzo[ a]pyrene (BaP) metabolism is established. As observed from experimental results, the BaP transfer from microcrystals to the cell membrane is definitely a first-order process. The rate constant of this process is signified as k1. We describe the surface–midplane exchange as reversible and use rate constants k2 and k3 to describe the inward and outward diffusions, respectively. The metabolism is identified as an irreversible reaction with a rate constant k4. If k2 and k3 are assumed to be fast and not rate determining, the effect of the metabolism rate, k4, on the number density of BaP in the midplane of the microsomal membrane, m3, can be estimated. If the metabolism rate is faster than or comparable to the distribution rates, k2 and k3, the BaP concentration in the membrane midplane, m3, will quickly be dissipated. But if k4 is extremely small, m3 will reach a plateau. Under conditions when k2 and k3 also play significant roles in determining the overall rate, more complicated patterns of m3 are expected.

scholarly journals Kinetics of thiamin cleavage by sulphite

1969 ◽  
Vol 113 (4) ◽  
pp. 611-615 ◽  
Author(s):  
J. Leichter ◽  
M. A. Joslyn
Keyword(s):  
Aqueous Solutions ◽  
Rate Constant ◽  
Sulphur Dioxide ◽  
First Order ◽  
Ph Values ◽  
Rate Of Reaction ◽  
Kinetics Of

Results are presented on the rate of thiamin cleavage by sulphite in aqueous solutions as affected by temperature (20–70°), pH(2·5–7·0), and variation of the concentration of either thiamin (1–20μm) or sulphite (10–5000μm as sulphur dioxide). Plots of the logarithm of percentage of residual thiamin against time were found to be linear and cleavage thus was first-order with respect to thiamin. At pH5 the rate was also found to be proportional to the sulphite concentration. In the pH region 2·5–7·0 at 25° the rate constant was 50m−1hr.−1 at pH5·5–6·0, and decreased at higher or lower pH values. The rate of reaction increased between 20° and 70°, indicating a heat of activation of 13·6kcal./mole.

scholarly journals THE KINETICS OF EXOSMOSIS OF WATER FROM LIVING CELLS

1927 ◽  
Vol 10 (5) ◽  
pp. 659-664 ◽  
Author(s):  
Morton McCutcheon ◽  
Baldwin Lucke
Keyword(s):  
Osmotic Pressure ◽  
Salt Concentration ◽  
Driving Force ◽  
Temperature Characteristic ◽  
Living Cells ◽  
Velocity Constant ◽  
Osmotic Equilibrium ◽  
Kinetics Of

1. The rate of exosmosis of water was studied in unfertilized Arbacia eggs, in order to bring out possible differences between the kinetics of exosmosis and endosmosis. 2. Exosmosis, like endosmosis, is found to follow the equation See PDF for Equation, in which a is the total volume of water that will leave the cell before osmotic equilibrium is attained, x is the volume that has already left the cell at time t, and k is the velocity constant. 3. The velocity constants of the two processes are equal, provided the salt concentration of the medium is the same. 4. The temperature characteristic of exosmosis, as of endomosis, is high. 5. It is concluded that the kinetics of exosmosis and endosmosis of water in these cells are identical, the only difference in the processes being in the direction of the driving force of osmotic pressure.

scholarly journals The binding of cyanide to ferroperoxidase

1971 ◽  
Vol 122 (1) ◽  
pp. 79-87 ◽  
Author(s):  
Charles Phelps ◽  
Eraldo Antonini ◽  
Maurizio Brunori
Keyword(s):  
Sodium Dithionite ◽  
Affinity Constant ◽  
Kinetic Measurements ◽  
First Order ◽  
Ph Values ◽  
Cyanide Binding ◽  
Single Process ◽  
Ph Jump ◽  
Equilibrium And Kinetics ◽  
Kinetics Of

1. The equilibrium and kinetics of cyanide binding to ferroperoxidase were investigated. At pH9.1 the equilibrium and kinetic measurements agree closely and disclose a single process with an affinity constant of 1.1×103m@!-1 and combination and dissociation velocity constants of 29m-1·s-1 and 2.5×10-2s-1 respectively. 2. At pH values below 8 the affinity constant falls until at pH6.0 the ferroperoxidase·cyanide complex is no longer formed. This is shown to be associated with the formation of ferriperoxidase·cyanide complex in the mixture even in the presence of excess of sodium dithionite. 3. Rapid-pH-jump experiments show a fast pseudo-first-order interconversion between ferroperoxidase·cyanide complex at pH9.1 and ferriperoxidase·cyanide complex at pH6.0. 4. The kinetics of binding of cyanide to dithionite-reduced peroxidase at pH6.0 are complicated and radically different from those observed at pH9.1. 5. Above pH8 the change of affinity constant with pH is consistent with the undissociated species, HCN, being bound by the ferroperoxidase. The enthalpy for this process measured both by equilibrium and kinetic methods is about -8kcal/mol. 6. The binding of cyanide to reconstituted peroxidases, proto, meso and deutero, was investigated. 7. The results are discussed in relation to known data on cyanide binding to other haemoproteins.

scholarly journals Kinetics of aflatoxin B1 and G2 adsorption on Ca-clinoptilolite

2000 ◽  
Vol 65 (10) ◽  
pp. 715-723 ◽  
Author(s):  
Aleksandra Dakovic ◽  
Magdalena Tomasevic-Canovic ◽  
Vera Dondur ◽  
Aleksandra Vujakovic ◽  
Predrag Radosevic
Keyword(s):  
Adsorption Process ◽  
Order Reaction ◽  
Active Centers ◽  
Fast Reaction ◽  
First Order ◽  
Ph Values ◽  
Zero Order Reaction ◽  
Rate Method ◽  
Adsorption Rates ◽  
Kinetics Of

The kinetics of aflatoxins B1 and G2 adsorption on Ca-clinoptilolite at pH2 and 7, in aqueous electrolyte at 37?C were studied. For both aflatoxins, the adsorption process begins with a fast reaction whereby most of the toxin is adsorbed in the first few minutes. This fast process is followed by the significantly slower process of aflatoxin bonding at active centers of mineral adsorbent. The initial rate method showed that the fast adsorption process of aflatoxin ?1 and G2, at both pH values is a first order reaction, while the slow adsorption process of these aflatoxins is a zero order reaction. The adsorption indexes and adsorption rates for both examined toxins were pH dependent. In the investigated initial toxins concentration ranges (500-3000 ?g/dm3), high adsorption indexes were achieved (> 80 %).

Hydrothermal crystallization kinetics of m-ZrO2 and t-ZrO2

1990 ◽  
Vol 5 (11) ◽  
pp. 2698-2705 ◽  
Author(s):  
Raymond P. Denkewicz ◽  
Kevor S. TenHuisen ◽  
James H. Adair
Keyword(s):  
Crystallization Kinetics ◽  
Low Ph ◽  
Formation Mechanisms ◽  
Gel Structure ◽  
Hydrothermal Conditions ◽  
High Ph ◽  
Ph Values ◽  
Ph Conditions ◽  
Apparent Activation Energies ◽  
Kinetics Of

The isothermal nucleation and crystallization kinetics of hydrothermally prepared monoclinic and tetragonal ZrO2 have been determined at various pH conditions. It is shown that monoclinic ZrO2 precipitates at low pH whereas at high pH tetragonal ZrO2 crystallizes from an amorphous zirconium (hydrous) oxide, Zr(OH)xOy, precursor. At intermediate pH conditions mixtures of the polymorphs are formed suggestive of kinetically competing particle formation mechanisms. The data are explained by the proposed existence of three controlling regimes for the formation of crystalline ZrO2: dissolution/precipitation at low pH, a solubility controlled regime at intermediate pH values, and a gel structure controlled regime at high pH. Apparent activation energies for the nucleation and crystallization of monoclinic and tetragonal ZrO2 formed under hydrothermal conditions are presented.

scholarly journals Mechanistic studies of carboxypeptidase Y from Saccharomyces cerevisiae. pH and pD profiles and inactivation at low pH (pD) values

1980 ◽  
Vol 187 (3) ◽  
pp. 843-849 ◽  
Author(s):  
W T Chang ◽  
K T Douglas
Keyword(s):  
Tertiary Structure ◽  
Low Ph ◽  
Carboxypeptidase Y ◽  
Mechanistic Studies ◽  
Ph Profile ◽  
First Order ◽  
Steady State Kinetics ◽  
Ph Dependent ◽  
Kinetics Of ◽  
Hydrolysis Of

Steady-state kinetics of carboxypeptidase Y, a proteinase from yeast, were studied by using the reaction of 4-nitrophenyl trimethylacetate as a probe. The pH profile of kcat. is sigmoidal in H2O-based buffers for the carboxypeptidase Y-catalysed hydrolysis of this ester (kcat. referring to the rate of deacylation of trimethylacetyl-carboxypeptidase Y). The corresponding pD profile in 2H2O is doubly sigmoidal, with inflexions at pD approximately 3.8 and approximately 6.8. The ionization of pKDapp. approximately 3.8 is caused by a rapid inactivation in 2H2O media by a process that is only slowly reversed on transfer to pH 7.00 phosphate buffer in H2O. The corresponding inactivation in H2O-based buffers of low pH is considerably slower (approximately 30-fold), follows a first-order rate-dependence and is very strongly pH-dependent, indicating some form of co-operative change in enzyme tertiary structure.

Deposition of Functionalized Polyethylenimine-Dye onto Cotton and Wool Fibres

2014 ◽  
Vol 18 (1) ◽  
pp. 36-49 ◽  
Author(s):  
A.G. Hassabo ◽  
A. Mendrek ◽  
C. Popescu ◽  
H. Keul ◽  
M. Möller
Keyword(s):  
Deposition Process ◽  
Good Alternative ◽  
Kinetics Of Adsorption ◽  
First Order ◽  
Ph Values ◽  
First Order Kinetics ◽  
Colour Strength ◽  
Equilibrium Data ◽  
Amine Groups ◽  
Kinetics Of

Functionalized polyethylenimine–dye (FPEI) is prepared by mixing branched polyethyleneimine (PEI), in which its primary amine groups are modified at different ratios with a quaternary ammonium coupler (QI), and reactive dyestuff (RD) (QI/RD = 0/100, 20/80, 40/60, 60/40 and 80/20 mole/mole %). The deposition of FPEI from an aqueous solution onto the surface of cotton and wool fibres is studied. The adsorption of a charged polymer from an aqueous medium by cotton and wool fibres is investigated at different pH values, and the uptake of colour on fibres is measured by Datacolor and UVVIS spectrophotometers. The study of the kinetics of adsorption shows that pseudo-first-order kinetics provide the best correlation of the experimental data. The equilibrium data indicate that the deposition process onto both cotton and wool follows the Langmuir isotherm. In terms of colour strength (K/S value) the coated fibres compare well with those dyed with a commercial dyestuff, C.I. Basic Red 51, which suggests that the coating is a good alternative to classical dyeing.

An infrared assay of the kinetics of phosphate-release from physiological substrates in living cells

2014 ◽  
Author(s):  
Ren Zhongyuan ◽  
Do Leduy ◽  
Saida Mebarek ◽  
Nermin Keloglu ◽  
Saandia Ahamada ◽  
...  
Keyword(s):  
Living Cells ◽  
Phosphate Release ◽  
Kinetics Of ◽  
Physiological Substrates
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