Determination of the second stoichiometric dissociation constants of glycine in aqueous sodium or potassium chloride solutions at 298.15 K

2003 ◽  
Vol 81 (12) ◽  
pp. 1462-1470 ◽  
Author(s):  
Jaakko I Partanen ◽  
Pekka M Juusola ◽  
Pentti O Minkkinen ◽  
Virginie Verraes
Keyword(s):  
Ionic Strength ◽  
Dissociation Constant ◽  
Dissociation Constants ◽  
Glass Electrode ◽  
Ionic Strength Dependence ◽  
Electrode Cell ◽  
Ion Activity ◽  
Strength Dependence ◽  
Single Ion Activity

Equations were determined for the calculation of the second stoichiometric (molality scale) dissociation constant, Km2, of glycine, in aqueous NaCl and KCl solutions at 298.15 K, from the thermodynamic dissociation constant, Ka2, of this acid and the ionic strength, Im, of the solution. The ionic strength of the solutions considered in this study is determined mostly by the salt alone, and the equations for Km2 were based on the single-ion activity coefficient equations of the Hückel type. New data measured by potentiometric titrations in a glass electrode cell were used in the estimation of the parameters for the Hückel equations of glycine species. By means of the calculation method suggested in this study, Km2 can be obtained almost within experimental error up to an Im of about 1.0 mol kg–1 for glycine in NaCl and KCl solutions. The Km2 values obtained by these methods were also compared with the values suggested in the literature for this quantity.Key words: ionic strength dependence, stoichiometric dissociation constant, Debye–Hückel equation, potentiometry, glycine.

Re-evaluation of the second thermodynamic dissociation constants of α-alanine, valine, and leucine using potentiometric data measured for aqueous potassium chloride solutions at 298.15 K

2005 ◽  
Vol 83 (1) ◽  
pp. 46-56 ◽  
Author(s):  
Jaakko I Partanen ◽  
Pekka M Juusola ◽  
Virginie Verraes
Keyword(s):  
Amino Acids ◽  
Ionic Strength ◽  
Activity Coefficient ◽  
Potentiometric Titration ◽  
Dissociation Constants ◽  
Ionic Strength Dependence ◽  
Harned Cell ◽  
Titration Data ◽  
Single Ion Activity ◽  
Potentiometric Data

Equations were developed for the calculation of the second stoichiometric (molality scale) dissociation constants (Km2) of α-alanine, valine, and leucine in aq. KCl solutions at 298.15 K from the revised thermodynamic dissociation constants (Ka2) of these acids and the ionic strength (Im) of the solutions. The ionic strength of the solutions considered in this study is determined mostly by KCl alone, and the equations for Km2 were based on the single-ion activity coefficient equations of the Hückel type. The existing literature data obtained from Harned cell measurements and new potentiometric titration data were used to revise the Ka2 values of the three amino acids. The values (1.295 ± 0.013) × 10–10, (1.894 ± 0.009) × 10–10, and (1.685 ± 0.011) × 10–10 were obtained from the new potentiometric titration data for α-alanine, valine, and leucine, respectively. For alanine and valine, the new Ka2 values are also supported by the Harned cell data used, but the value (1.80 ± 0.02) × 10–10 obtained for leucine from these data is significantly different. The potentiometric values are recommended here. The activity coefficient equations for the calculation of Km2 values were also determined from the new potentiometric data. By means of the activity coefficient equations obtained for these three amino acids for KCl solutions, Km2 can be evaluated almost within experimental error up to an Im of about 1.0 mol kg–1. The Km2 values calculated by this method are also compared with the values suggested in the literature.Key words: ionic strength dependence, stoichiometric dissociation constant, Debye-Hückel equation, potentiometry, α-alanine, valine, leucine.

The ionic strength dependence of chromatin folding

1978 ◽  
Vol 36 (2) ◽  
pp. 220-221
Author(s):  
F. Thoma ◽  
TH. Koller
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Ionic Strength ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Carbon Supports ◽  
Ionic Strength Dependence ◽  
Chromatin Folding ◽  
Strength Dependence ◽  
Preparation Techniques

Under a variety of electron microscope specimen preparation techniques different forms of chromatin appearance can be distinguished: beads-on-a-string, a 100 Å nucleofilament, a 250 Å fiber and a compact 300 to 500 Å fiber.Using a standardized specimen preparation technique we wanted to find out whether there is any relation between these different forms of chromatin or not. We show that with increasing ionic strength a chromatin fiber consisting of a row of nucleo- somes progressively folds up into a solenoid-like structure with a diameter of about 300 Å.For the preparation of chromatin for electron microscopy the avoidance of stretching artifacts during adsorption to the carbon supports is of utmost importance. The samples are fixed with 0.1% glutaraldehyde at 4°C for at least 12 hrs. The material was usually examined between 24 and 48 hrs after the onset of fixation.

Meso tetrakis ortho-, meta-, and para-N-alkylpyridiniopor-phyrins: kinetics of copper(II) and zinc(II) incorporation and zinc porphyrin demetalation

2003 ◽  
Vol 07 (03) ◽  
pp. 139-146 ◽  
Author(s):  
Peter Hambright ◽  
Ines Batinić-Haberle ◽  
Ivan Spasojević
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Effective Charge ◽  
Methyl Ethyl ◽  
Ionic Strength Dependence ◽  
Zinc Porphyrin ◽  
Cationic Porphyrin ◽  
Strength Dependence ◽  
Acid Catalyzed ◽  
Kinetics Of

The relative reactivities of the tetrakis( N -alkylpyridinium- X - yl )-porphyrins where X = 4 (alkyl = methyl, ethyl, n -propyl) , X = 3 (methyl) , and X = 2 (methyl, ethyl, n -propyl, n -butyl, n -hexyl, n -octyl) were studied in aqueous solution. From the ionic strength dependence of the metalation rate constants, the effective charge of a particular cationic porphyrin was usually larger when copper(II) rather than zinc(II) was the reactant. The kinetics of ZnOH + incorporation and the acid catalyzed removal of zinc from the porphyrins in 1.0 M HCl were also studied. In general, the more basic 4- (para-) and 3- (meta-) isomers were the most reactive, followed by the less basic 2- (ortho-) methyl to n -butyl derivatives, with the lipophilic ortho n -hexyl and n -octyl porphyrins the least reactive.

Ionic Strength Dependence of Protonation Constants ofN-Alkyl Substituted Open Chain Diamines in NaClaq

2004 ◽  
Vol 49 (1) ◽  
pp. 109-115 ◽  
Author(s):  
Francesco Crea ◽  
Concetta De Stefano ◽  
Ottavia Giuffrè ◽  
Silvio Sammartano
Keyword(s):  
Ionic Strength ◽  
Protonation Constants ◽  
Ionic Strength Dependence ◽  
Open Chain ◽  
Strength Dependence

NaCl and CaCl2 activity coefficients in mixed aqueous solutions

1965 ◽  
Vol 20 (6) ◽  
pp. 1332-1336 ◽  
Author(s):  
Edward W. Moore ◽  
James W. Ross
Keyword(s):  
Ionic Strength ◽  
Activity Coefficients ◽  
Technical Assistance ◽  
Osmotic Coefficients ◽  
Electrode System ◽  
Glass Electrode ◽  
Concentration Data ◽  
Harned's Rule ◽  
Potentiometric Measurement

In the investigation of numerous physiological phenomena it is the activity of an ion species which is desired, rather than stoichiometric concentration. The calculation of mean ionic activity from known concentration data requires accurate activity coefficients (ggr). This report concerns the determination of ggrNaCl and ggrCaCl2 in mixed NaCl-CaCl2 solutions by potentiometric measurement with a sodium-selective glass electrode-Ag/AgCl electrode system over the ionic strength range 0.05–0.5 m. Log ggrNaCl varied linearly, at constant total ionic strength, with the ionic strength of CaCl2 in the mixture, in accordance with Harned's rule. From data thus obtained, ggrCaCl2 coefficients in such mixed solutions have been calculated and compared with values calculated from published osmotic data. Resulting activity coefficient curves for ggrCaCl2 are presented over the concentration range encountered in serum and other extracellular fluids. Note: (With the Technical Assistance of Leonard Kaye and Leonard L. Anderson) glass electrodes; ion interaction; electrolyte metabolism; Harned's rule; membrane transport; osmotic coefficients Submitted on March 11, 1965

Which value for the first dissociation constant of carbonic acid should be used in biological work?

1991 ◽  
Vol 260 (5) ◽  
pp. C1113-C1116 ◽  
Author(s):  
R. W. Putnam ◽  
A. Roos
Keyword(s):  
Ionic Strength ◽  
Activity Coefficient ◽  
Dissociation Constant ◽  
Carbonic Acid ◽  
Mass Action ◽  
Bicarbonate Concentration ◽  
Apparent Dissociation Constant ◽  
Logarithmic Form ◽  
Ion Activity ◽  
Hasselbalch Equation

The apparent first dissociation constant of carbonic acid has been defined in different ways in the literature. Harned and co-workers (8-10) have defined it in terms of molalities of the participating species, including H ions: Ks = mHmHCO3/mCO2. In contrast, Hastings and Sendroy have defined an apparent constant in which acidity is expressed as H ion activity: K'1 = aHmHCO3/mCO2. These constants differ by a factor gamma H, the activity coefficient of H ions at the prevailing ionic strength. Therefore, pK'1 is greater than pKs by an amount equal to -log gamma H, which, at mu = 0.16 M, is approximately 0.1. It is important that the correct value for the apparent dissociation constant or its logarithmic form be entered in the mass action expression or in the Henderson-Hasselbalch equation in order to prevent significant errors in the computation by means of these equations of quantities that cannot be directly measured. Specifically, for the derivation of bicarbonate concentration from PCO2 and pH (-log aH), pK'1 is to be used and not an uncorrected pKs.

Sign in / Sign up

Export Citation Format

Share Document