scholarly journals Acidic dissociation constant and related thermodynamic quantities for diethanolammonium ion in water from 0 to 50 °C

1962 ◽  
Vol 66A (1) ◽  
pp. 71 ◽  
Author(s):  
Vincent E. Bower ◽  
Robert A. Robinson ◽  
Roger G. Bates
Keyword(s):  
Dissociation Constant ◽  
Thermodynamic Quantities ◽  
Acidic Dissociation ◽  
Acidic Dissociation Constant

QSTR mathematical models for the toxicity of aliphatic carboxylic acids on tetrahymena pyriformis

2013 ◽  
Vol 22 (2) ◽  
Author(s):  
Zoița Mărioara Berinde
Keyword(s):  
Dissociation Constant ◽  
Carboxylic Acids ◽  
Aquatic Toxicity ◽  
Tetrahymena Pyriformis ◽  
Refraction Index ◽  
Linear Regression Models ◽  
Acidic Dissociation ◽  
Growth Assay ◽  
Aliphatic Carboxylic Acids ◽  
Acidic Dissociation Constant

The present work represents an attempt to improve QSTR models for aquatic toxicity of 3838 aliphatic carboxylic acids tested in the Tetrahymena pyriformis population growth assay, using the topological index ZEP and the following nine main electrotopological and molecular descriptors: acidic dissociation constant, 1-octanol/water partition coefficient, the energy of the lowest unoccupied molecular orbital, acidic dissociation constant, molar refractivity, refraction index, surface tension, polarizability and, electrotopological states. Several different relations between toxicity [loglog(IGC50-1)] and the molecular and topological properties were examined, and a group of multiple linear regression models with high fitness scores were generated.

Influence of certain urinary solutes on acidic dissociation constant of ammonium at 37°C

1960 ◽  
Vol 15 (1) ◽  
pp. 125-127 ◽  
Author(s):  
Norman Bank ◽  
William B. Schwartz
Keyword(s):  
Ionic Strength ◽  
Dissociation Constant ◽  
High Concentration ◽  
Acidic Dissociation ◽  
Discernible Effect ◽  
Hückel Theory ◽  
Acidic Dissociation Constant

The acidic dissociation constant (pKa ' ) of ammonium was studied at 37 °C over a physiologic range of ionic strength. It was demonstrated that certain ions commonly found in high concentration in urine had no discernible effect on the pka' other than that resulting from their contribution to ionic strength. Urea in a concentration of 0.5 moles/l. had no significant effect on pka '. The data are taken to indicate that in urines of usual composition, ammonium pka ' should closely follow the predictions of Debye-Hückel theory. Submitted on June 19, 1959

scholarly journals Equilibrium and Kinetic Properties of the Interaction between Tetrodotoxin and the Excitable Membrane of the Squid Giant Axon

1970 ◽  
Vol 55 (3) ◽  
pp. 309-335 ◽  
Author(s):  
Leon Andres Cuervo ◽  
William J. Adelman
Keyword(s):  
Dissociation Constant ◽  
Rate Constants ◽  
Sodium Current ◽  
Giant Axon ◽  
Kinetic Properties ◽  
Bathing Solution ◽  
Thermodynamic Quantities ◽  
Partial Recovery ◽  
Reactive Site ◽  
Membrane Complex

Squid giant axons were treated with tetrodotoxin (TTX) in concentrations ranging from 1 nM to 25 nM and the resulting decrease in sodium current was followed in time using the voltage clamp technique. The removal of TTX from the bathing solution produced only partial recovery of the sodium current. This suggests that the over-all interaction is more complex than just a reversible reaction. By correcting for the partial irreversibility of the decrease in sodium current, a dissociation constant of 3.31 x 10-9 M was calculated for the reaction between TTX and the reactive site of the membrane. The data obtained fit a dose-response curve modified to incorporate the correction for partial irreversibility when calculated for a one-to-one stoichiometry. The fit disagreed with that calculated for a reaction between two molecules of TTX with a single membrane-reactive site, but neither supported nor disproved the possibility of a complex formed by two reactive sites with one molecule of TTX. Values of the rate constants for the formation and dissociation of the TTX-membrane complex, k1 and k2, respectively, were obtained from the kinetic data. The values are: k1 = 0.202 x 108 M-1, and k2 = 0.116 min-1. The magnitude of the dissociation constant derived from these values is 5.74 x 10-9 M, which has the same order of magnitude as that obtained from equilibrium measurements. Arrhenius plots of the rate constants gave values for the thermodynamic quantities of activation.

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