Reexamination of the Kirkwood-Westheimer theory of electrostatic effects. 4. Effect of N-substitution on the dissociation constants of some .alpha.,.omega.-amino acids

1979 ◽  
Vol 44 (4) ◽  
pp. 615-619 ◽  
Author(s):  
John T. Edward ◽  
Patrick G. Farrell ◽  
Jean Claude Halle ◽  
Jitka Kirchnerova ◽  
Robert Schaal ◽  
...  
Keyword(s):  
Amino Acids ◽  
Dissociation Constants ◽  
Electrostatic Effects ◽  
Alpha Omega

Re-examination of the Kirkwood–Westheimer theory of electrostatic effects. II. Possible conformations of α,ω-amino-acids in aqueous solutions, as deduced from dissociation constants

1978 ◽  
Vol 56 (8) ◽  
pp. 1122-1129 ◽  
Author(s):  
John T. Edward ◽  
Patrick G. Farrell ◽  
John L. Job ◽  
Bo-Long Poh
Keyword(s):  
Amino Acids ◽  
Aqueous Solutions ◽  
Dissociation Constants ◽  
Random Coil ◽  
Similar Calculation ◽  
Electrostatic Effects ◽  
Different Temperatures ◽  
Tentative Explanation ◽  
Fully Extended Conformation ◽  
Good Agreement

The first and second dissociation constants of the ten homologous a, α,ω-amino-acids [Formula: see text] have been determined by a potentiometric method at different temperatures, and hence the thermodynamic parameters ΔG0, ΔH0, and ΔS0 were computed. Calculation by Kirkwood–Westheimer theory of ΔG10 for the first (carboxyl) dissociation, assuming the conformation of the polymethylene chain to be intermediate between the random-coil and the fully extended conformation, gives results in good agreement with experiment for the longer chains. A similar calculation of ΔG20 for the second (ammonium) dissociation gives results in fair agreement with theory for the very long chains (n = 7–10), but in disagreement for shorter chains. A tentative explanation based on electrostatic effects on hydration of the ammonium group is advanced.

Chelating polymers. I. The synthesis and acid dissociation behavior of several N-(p-vinylbenzenesulfonyl)-substituted diaminopolyacetic acid monomers, monomeric analogues, and related intermediates

1970 ◽  
Vol 48 (1) ◽  
pp. 163-175 ◽  
Author(s):  
R. M. Genik-Sas-Berezowsky ◽  
I. H. Spinner
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Dissociation Constants ◽  
Acid Dissociation ◽  
Inductive Effects ◽  
Cyclic Amide ◽  
Amino Acid Analogues ◽  
Related Compounds ◽  
Chelating Polymers ◽  
Made In

Two new chelating monomers, N-(p-vinylbenzenesulfonyl)1,2-diaminoethane-N′,N′-diacetic (SS-EDDA) and -N,N′,N′-triacetic (SS-ED3A) acids, as well as several monomeric analogues and related intermediates have been prepared. In addition, 2-oxo-1-piperazine acetic (S-KP), 3-oxo-1-piperazine acetic (U-KP), and 2-oxo-1,4-piperazine diacetic (3-KP) acids have been synthesized and the interconvertibility between these cyclic amides and their unsubstituted linear amino acid analogues, ethylene-diamine-N,N′-diacetic (S-EDDA), -N,N-diacetic (U-EDDA), and -N,N,N′-triacetic (ED3A) acids respectively, was demonstrated.The acid dissociation constants of the various amino acids were determined potentiometrically at 25° and μ = 0.1 M(KNO3) and the results were compared with the hydrogen ion affinities of related compounds. Dissociation schemes were proposed for all the compounds based on these results. Rationalizations of the linear amino acid and the cyclic amide dissociation constants were made in terms of the effects of cyclization and the inductive effects of neighboring groups. These rationalizations were found to be helpful in clarifying the dissociation schemes previously proposed for several of the linear amino acids.

scholarly journals The combination curves, hydrogen ion regulating power and dissociation constants of gelatin

1931 ◽  
Vol 108 (756) ◽  
pp. 224-232 ◽  
Keyword(s):  
Amino Acids ◽  
Dissociation Constants ◽  
Hydrogen Ion ◽  
New Method ◽  
Equivalent Weight ◽  
Acid Base ◽  
Buffer Capacities ◽  
Alkaline Range ◽  
Undissociated Molecule

The existing titrations of gelatin with acid and alkali have been found to refer mainly to solutions containing approximately 1 per cent. of the dry material, while the few titrations in 0·1 per cent. solutions are not in agreement. A series of titrations with alkali at both concentrations of gelatin has been made with a view to deciding whether the combining weight is really affected by the concentration. From the collected data, the combining or equivalent weight has been calculated by a new method based on the theory of buffer mixtures, and incidentally, the buffer capacities at the different concentrations have been determined. The equivalent so found has been compared with those which have been deduced by other methods. The equivalents of the 1·0 per cent. and 0·1 per cent. solutions in the alkaline range have also been calculated by another method using constants, and found to differ from one another. The equivalents as acid and as base have been deduced in various ways from the combination curves and also from the cleavage products, and these acid/base ratios have been compared. Finally by treating gelatin as a simple ampholyte, apparent constants have been calculated both on the undissociated molecule or older and on the "amphoteric ion" or newer theory. Although gelatin is undoubtedly amphoteric in its nature, yet its curves of combination ( p H plotted against x = added acid or alkali) differ greatly from those of simple amino-acids such as glycine, as is easily seen by comparing the types which have been portrayed by Harris (1923, 1925, 1930).

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