Binding of cadmium and copper(II) ions to oligogalacturonic acids

1983 ◽  
Vol 48 (7) ◽  
pp. 1922-1935 ◽  
Author(s):  
Rudolf Kohn ◽  
Kveta Heinrichová ◽  
Anna Malovíková
Keyword(s):  
Uronic Acid ◽  
Multiple Equilibria ◽  
Carboxyl Groups ◽  
Polymerization Degree ◽  
Indicator Method ◽  
Ion Activity ◽  
Elimination Mechanism ◽  
Single Ion Activity ◽  
Degree Of Association ◽  
Positively Charged

The binding of Cu2+ and Cd2+ ions to potassium oligogalacturonates of polymerization degree DP 1 to 9 was investigated by ion-specific electrodes and by the metallochromic indicator method. The interaction was evaluated on the basis of degree of association β of cations (M2+) with carboxyl groups of the compounds examined and the single-ion activity coefficients of counterions γM2+. The results were compared with values corresponding to an electrostatic bond of Ca2+ ions to these oligomers. The Cd2+, and especially Cu2+ ions were bound in a considerable measure already to mono- and oligogalacturonates of a low polymerization degree very probably by a chelate bond. Precipitation of Cu- and Cd-oligogalacturonates takes place at a polymerization degree DP 5 and 8, respectively. Interpretation of results by the multiple equilibria theory evidenced that the Cu2+ ions were stoichiometrically bound to mono- and oligogalacturonates (one cation to two carboxyl groups) similarly, as with polymeric D-galacturonan. The results revise the early conception concerning the formation of a positively charged complex of Cu2+ ions (similarly also of Cd2+ and Pb2+ ions) with monogalacturonic acid of (MA)+ type, where A- is the anion of uronic acid. The results are a contribution to the elucidation of the elimination mechanism of these toxic cations from human body involving the oligomeric fragments of pectin as products of its enzymic degradation in the digestive tract.

Binding of lead cations to oligogalacturonic acids

1982 ◽  
Vol 47 (12) ◽  
pp. 3424-3431 ◽  
Author(s):  
Rudolf Kohn
Keyword(s):  
Human Body ◽  
Calcium Ions ◽  
Galacturonic Acid ◽  
Uronic Acid ◽  
The Other ◽  
Carboxyl Groups ◽  
Polymeric Chain ◽  
Polymerization Degree ◽  
Strong Decrease ◽  
Nitrate Ions

The activity of Pb2+ ions in solutions of lead oligogalacturonates of polymerization degree DP 1 to 5 (starting concentration of the investigated solutions 3.00 mmol (COOPb0.5) l-1, the ionic strenght of the solution I = 0.01 mol l-1, electrolyte KNO3, was determined by lead specific ion electrodes. The activity aPb2+ is independent on the kind of anion in very diluted solutions of lead perchlorate and nitrate. Ions of lead become bound quite firmly even to the monomeric D-galacturonic acid (association degree of Pb2+ ions to carboxyl groups of uronic acid β = 0.43). The increase of polymerization degree is associated with a strong decrease of the lead oligogalacturonate solubilities on one hand, and increase of the bond strenght of the Pb2+ ions to these oligomers on the other. The association degree of Pb2+ ions to carboxyl groups of the pentamer (β = 0.96) almost reaches the value found for the polymeric chain of pectate molecule (D-galacturonan); here, the stoichiometric binding of Pb2+ to two carboxyl groups takes place with a great deal of probability. Lead has been found to bind highly preferentially to oligogalacturonates even in the presence of calcium ions. Results presented in this paper help to clear the mechanism of elimination of lead from the human body through pectin and its oligomeric fragments.

Binding of lead and copper(II) ions to starch and amylose 2,3-dicarboxy derivatives

1986 ◽  
Vol 51 (5) ◽  
pp. 1160-1169 ◽  
Author(s):  
Rudolf Kohn ◽  
Karol Tihlárik
Keyword(s):  
Ionic Strength ◽  
Multiple Equilibria ◽  
Copper Ions ◽  
Metal Cations ◽  
Lead Ions ◽  
High Concentration ◽  
Counter Ion ◽  
Ion Activity ◽  
Degree Of Association ◽  
Derivatives Of

The binding of Pb2+ and Cu2+ ions to starch and amylose 2,3-dicarboxy derivatives of degrees of oxidation DO = 0.09-0.74 was investigated. The interaction of the metal cations with the carboxy groups of the derivatives was evaluated in terms of the counter-ion activity, determined with ion specific electrodes. The binding is very strong; at DO ≥ 0.34, lead ions are bound quantitatively ( degree of association β = 0.999), copper ions are also bound to a great extent (β = 0.94-0.97). The complexation of copper with the ligands at ionic strength I = 0.15 mol 1-1 was treated in terms of multiple equilibria theory. Different complexes were found in dependence on the concentration ratios of the reactants; at a high excess of COO- groups with respect to Cu2+ ions, the latter are strongly bound and the number of COO- groups binding a Cu2+ cation is greater than 2, whereas at a sufficiently high concentration of Cu2+ ions the number of COO- groups binding a Cu2+ cation approaches the stoichiometric value of 2.

Binding of zinc cations to pectin and its oligomeric fragments

1983 ◽  
Vol 48 (11) ◽  
pp. 3154-3165 ◽  
Author(s):  
Anna Malovíková ◽  
Rudolf Kohn
Keyword(s):  
Human Body ◽  
Carboxyl Groups ◽  
Zinc Ions ◽  
Logarithmic Function ◽  
Polymerization Degree ◽  
Continuous Increase ◽  
The Stability ◽  
Esterification Degree ◽  
Zinc Cations ◽  
Degree Of Association

The activity of Zn2+ ions bound to carboxyl groups of pectin of esterification degree E 0 to 90% and to oligomeric potassium galacturonates of polymerization degree 1 to 7 was estimated by the metallochromic indicator (tetramethylmurexide) method. The zinc ions are stoichiometrically bound to pectin, one Zn2+ cation to two free carboxyl groups. The stability constant K of zinc pectinates strongly decreases with the increasing esterification degree in a relationship close to a linear logarithmic function, log K = f(E) similarly, as with the binding of Ca2+ ions to pectin. Pectin reveals a little higher selectivity to Zn2+ ions when considering this couple of cations. The zinc ions are bound to the monomeric D-galacturonic acid to a very low extent in contrast to some toxic cations as e.g. Pb2+, Cu2+, and Cd2+. A continuous increase of the degree of association of Zn2+ ions with carboxyl groups of oligomers takes place with the increasing polymerization degree. The validity of the increment additivity of terminal and inner uronic acid units to the final activity of zinc counterions bound to these oligomers was proved. The results are discussed from the standpoint of application of pectin as an active component of prophylactic diets against poisoning with cations of toxic metals with respect to the excretion of Zn2+ ions from the human body. Findings concerning the interaction of Zn2+ ions with pectin in dependence on its esterification degree (E) constitute a theoretical basis for a potential application of pectin as a useful ligand of Zn2+ ions in medical treatment of zinc deficiency in the human body.

Binding of calcium ions on acid polysaccharides of peach gum and distribution pattern of carboxyl groups in the macromolecule

1979 ◽  
Vol 44 (8) ◽  
pp. 2517-2525 ◽  
Author(s):  
Rudolf Kohn ◽  
Jozef Rosík ◽  
Jozef Kubala ◽  
Anna Malovíková
Keyword(s):  
Calcium Ions ◽  
Carboxyl Groups ◽  
Cd Spectra ◽  
Methyl Derivative ◽  
Molar Ratios ◽  
Ion Activity ◽  
Acid Polysaccharide ◽  
The Mean ◽  
Peach Gum ◽  
Single Ion Activity

The acid polysaccharide of peach gum and its macromolecular products of a gradual degradation by acid hydrolysis were characterized by molecular weight (Mw) and molar ratios of both uronic acids and neutral saccharide units. The single-ion activity coefficient of calcium ions (γCa2+) bound to these acid polysaccharides and to the corresponding aldobiouronic acids was measured and CD spectra of potassium and calcium salts of these compounds were recorded. It was ascertained that Ca2+ ions are bound to carboxyl groups of polysaccharides under study by an electrostatic bond in molecular disperse solutions. The mean distance of the neighboring carboxyl groups b = 0.83 to 1.00 nm, calculated from the measured values γCa2+ indicates a very close arrangement of uronic acid units, which does not undergo alteration with the stepwise degradation of the macromolecule. The obtained results let us conclude that the main chain of the polysaccharide is substituted in longer segments by D-glucuronic acid units and its 4-O-methyl derivative (monomeric side chains), at least at each second D-galactose unit.

Binding of lead and copper(II) cations to hemicelluloses of rye bran

1986 ◽  
Vol 51 (10) ◽  
pp. 2250-2258 ◽  
Author(s):  
Rudolf Kohn ◽  
Zdena Hromádková ◽  
Anna Ebringerová
Keyword(s):  
Uronic Acid ◽  
Equilibrium Solution ◽  
Glucuronic Acid ◽  
The Other ◽  
Carboxyl Groups ◽  
Stoichiometric Ratio ◽  
Molar Ratios ◽  
Free Ions ◽  
Uronic Acid Content ◽  
The Relationship

Several fractions of acid hemicelluloses isolated from rye bran were characterized by molar ratios of saccharides (D-Xyl, L-Ara, D-Glc, D-Gal) and 4-O-methyl-D-glucuronic acid and protein content. Binding of Pb2+ and Cu2+ ions to these acid polysaccharides was considered according to function (M)b = f([M2+]f), expressing the relationship between the amount of metal (M)b bound to 1 g of the substance and the concentration of free ions [M2+]f in the equilibrium solution and according to the association degree β of these cations with carboxyl groups of uronic acid at a stoichiometric ratio of both components in the system under investigation. Acid hemicelluloses contained only a very small portion of uronic acid ((COOH) 0.05-0.18 mmol g-1); the model polysaccharide, 4-O-methyl-D-glucurono-D-xylan of beech, was substantially richer in uronic acid content ((COOH) 0.73 mmol g-1). Consequently, the amount of lead and copper bound to acid hemicelluloses is very small ((M)b 0.017-0.025 mmol g-1) at [M2+]f = 0.10 mmol l-1. On the other hand, much greater amount of cations ((M)f 0.09-0.10 mmol g-1) was bound to the glucuronoxylan. The association degree β was like with the majority of samples (β = 0.31-0.38). The amount of lead and copper(II) bound to acid hemicelluloses from rye bran is several times lower than that bound to dietary fiber isolated from vegetables (cabbage, carrot), rich in pectic substances.

Binding of calcium, lead, and copper(II) cations to galactaric and 2,5-furandicarboxylic acids and to D-galacturonic acid and its derivatives

1986 ◽  
Vol 51 (5) ◽  
pp. 1150-1159 ◽  
Author(s):  
Rudolf Kohn ◽  
Ján Hirsch
Keyword(s):  
Galacturonic Acid ◽  
Uronic Acid ◽  
Indicator Method ◽  
Cu Complex ◽  
Carboxylate Groups ◽  
Counter Ions ◽  
Galactaric Acid ◽  
Furandicarboxylic Acid ◽  
The Difference ◽  
Calcium Lead

The binding of Ca2+, Pb2+, and Cu2+ ions to galactaric and 2,5-furandicarboxylic acids and of Pb2+ and Cu2+ ions to D-galacturonic acid, its α-methylglycoside, and (methyl-4-deoxy-α-D-galactopyranosid)uronic acid was evaluated in terms of the activity coefficients of the counter-ions and the degrees of their association with the carboxylate groups of the acids. The activity of Ca2+ ions was determined by the metallochromic indicator method with tetramethylmurexide, that of Pb2+ and Cu2+ ions, with ion specific electrodes. Galactaric acid bids 89.5% Ca2+ ions, practically all (99.9%) Pb2+ ions and nearly all (98.6% Cu2+ ions, mostly with the formation of insoluble salts. As little as 7.6% Ca2+, 34.0% Pb2+, and 23.9% Cu2+ were bound to 2,5-furandicarboxylic acid in the form of soluble complexes, and slightly more, 4.1% Ca2+, 43.9% Pb2+, and 38.0% Cu2+, to D-galacturonic acid. The difference in the degrees of binding to galactaric acid and 2,5-furandicarboxylic acid is due to the different flexibility of their molecular skeletons. The activities of Pb2+ and Cu2+ ions in solutions of salts of D-galacturonic acid and its derivatives indicate that the OH group at C(4) of D-galacturonic acid takes part in the complexation. For the Pb2+ complex, the OH group at C(1) of the unsubstituted acid in the β-anomeric form also seems to participate in the complexation; this is not the case with the similar Cu complex.

scholarly journals Towards the Understanding of Water-in-Salt Electrolytes: Individual Ion Activities and Liquid Junction Potentials in Highly Concentrated Aqueous Solutions

2021 ◽  
Author(s):  
Damien Degoulange ◽  
Nicolas Dubouis ◽  
Alexis Grimaud
Keyword(s):  
Activity Coefficients ◽  
Operating Voltage ◽  
Redox Potentials ◽  
Liquid Junction ◽  
Nernst Potential ◽  
Concentrated Electrolytes ◽  
Ion Activity ◽  
Ion Activities ◽  
Single Ion Activity ◽  
Increased Activity

Highly concentrated electrolytes were recently proposed to improve the performances of aqueous electrochemical systems by delaying the water splitting and increasing the operating voltage for battery applications. While advances were made regarding their implementation in practical devices, debate exists regarding the physical origin for the delayed water reduction occurring at the electrode/electrolyte interface. Evidently, one difficulty resides in our lack of knowledge regarding ions activity arising from this novel class of electrolyte, it being necessary to estimate the Nernst potential of associated redox reactions such as Li<sup>+</sup> intercalation or the hydrogen evolution reaction. In this work, we first measured the potential shift of electrodes selective to either Li<sup>+</sup>, H<sup>+</sup> or Zn<sup>2+</sup> ions from diluted to highly concentrated regimes in LiCl or LiTFSI solutions. Observing similar shifts for these different cations and environments, we establish that shifts in redox potentials from diluted to highly concentrated regime originates in large from an increase junction potential, it being dependent on the ions activity coefficients that increase with concentration. While our study shows that single ion activity coefficients, unlike mean ion activity coefficients, cannot be captured by any electrochemical means, we demonstrate that protons concentration increases by approximatively two orders of magnitude from 1 mol.kg<sup>-1</sup> to 15-20 mol.kg<sup>-1</sup> solutions. Combined with the increased activity coefficients, this increases the activity of protons and thus the pH of highly concentrated solutions which appears acidic.

scholarly journals The Effects of Salts on the Stability of the Collagen Helix Under Acidic Conditions

1968 ◽  
Vol 21 (4) ◽  
pp. 821 ◽  
Author(s):  
Anne FW oodlock ◽  
BS Harrap
Keyword(s):  
Thermal Stability ◽  
Carboxyl Groups ◽  
Neutral Ph ◽  
Acid Ph ◽  
Helix Stability ◽  
Acidic Conditions ◽  
Anions And Cations ◽  
The Stability ◽  
Thermal Stability Of ◽  
Positively Charged

In the acid pH region, the relative effects of various salts on the thermal stability of the collagen helix are quite different from their effects at neutral pH. The magnitude of the decrease in thermal stability brought about by the salts studied depends mainly on the nature and concentration of the anion and very little on the nature of the cation, whereas at neutral pH the nature of both anions and cations affects the collagen helix stability, the effects of the two ions being roughly additive. The magnitude of the effect of salts at acid pH is much greater than that at neutral pH whereas for a non-ionized denaturant, urea, the magnitudes at both neutral and acid pH are similar. The data are discussed in terms of possible interactions between salts and the positively charged protein with particular consideration of the effects of salts on the pKa of protein carboxyl groups.

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