Binding of calcium ions to 2,3-dicarboxy derivatives of pectic acid

1986 ◽  
Vol 51 (10) ◽  
pp. 2259-2270 ◽  
Author(s):  
Anna Malovíková ◽  
Rudolf Kohn
Keyword(s):  
Activity Coefficient ◽  
Calcium Ions ◽  
High Selectivity ◽  
Carboxyl Groups ◽  
Free Enthalpy ◽  
Pectic Acid ◽  
Considerable Degradation ◽  
Oxidation Degradation ◽  
Derivatives Of ◽  
Low Activity

Using a two-step oxidation of pectic acid (85% of D-galacturonan in the preparation) a series of 2,3-dicarboxy derivatives (Na+ form) was prepared containing 4.2 to 8.5 mmol of carboxyl groups per gram (COOH g-1). After the centrifugation of the diluted suspensions of the Ca-salts of these polyacids the activity of the calcium counterions (aCa2+) was determined using the metallochromic indicator (tetramethylmurexide) and the activity coefficient γCa2+ was calculated. Using potentiometric titrations of polyacids with potassium and calcium hydroxides the decrease in electrostatic free enthalpy, Δ(Gel/N)KCa, of the cation exchange Ca2+ → 2 K+ was determined. In the course of the oxidation, degradation of the macromolecules took place, characterized by the limit viscosity number [η]. In spite of the considerable degradation, preparations with higher oxidation degrees display a high selectivity in the exchange of cations Ca2+ → 2 K+, similar to that determined recently by us in 2,3-dicarboxy derivatives of starch and amylose. The strong binding of Ca2+ ions to the investigated substances is also documented by very low activity coefficient values, γCa2+, ranging from 0.057 to 0.037.

Intramolecular binding of calcium ions to L-guluronan and D-galacturonan

1981 ◽  
Vol 46 (7) ◽  
pp. 1701-1707 ◽  
Author(s):  
Rudolf Kohn ◽  
Anna Malovíková
Keyword(s):  
Activity Coefficients ◽  
Calcium Ions ◽  
Uronic Acid ◽  
Total Activity ◽  
Polymeric Chain ◽  
Polymerization Degree ◽  
Pectic Acid ◽  
Calcium Salts ◽  
Macromolecule Chain ◽  
Derivatives Of

The values of activity coefficients γCa2+, determined earlier in solutions of calcium oligoguluronates and oligogalacturonates of various polymerization degree n, were interpreted. Values γCa2+ corresponding to an intramolecular Ca2+ bond to a polymeric chain of L-guluronan and D-galacturonan were obtained by extrapolation of functions γCa2+ = f(1/n) and γCa2+ = f((n-2)/n) to lim n → ##h. The γCa2+ values were compared with those determined in solutions of calcium salts of O-acetyl derivatives of pectic acid and D-mannuronan. In molecular disperse solutions the Ca2+ ions are bound to L-guluronan and D-galacturonan by an electrostatic bond. The course of the above-mentioned functions leads to the conclusion that both terminal uronic acid units in polyuronates under study bind Ca2+ ions less firmly than do the inner units in the macromolecule chain. The linear course of the function γCa2+ = f((n-2)/n) for L-guluronan proves the additivity of contribution of the terminal and inner uronic acid units to the total activity of Ca2+ counterions bound to L-guluronan.

Binding of calcium ions to 2,3-dicarboxy derivatives of starch and amylose

1984 ◽  
Vol 49 (9) ◽  
pp. 2116-2129 ◽  
Author(s):  
Rudolf Kohn ◽  
Karol Tihlárik
Keyword(s):  
Calcium Ions ◽  
Corn Starch ◽  
Spatial Arrangement ◽  
Ring Cleavage ◽  
Carboxyl Groups ◽  
Linear Charge ◽  
Oxidation Degree ◽  
Linear Charge Density ◽  
Macromolecule Chain ◽  
Derivatives Of

A series of 2,3-dicarboxy derivatives of oxidation degree DO(d.c.) 0.13 to 0.90 was prepared by a two-stage oxidation of corn starch and amylose. The activity coefficient γCa2+ of calcium counterions was estimated in solutions of calcium salts of these carboxy derivatives in a 3.00 mmol (COOCa0.5)l-1 concentration by a metallchromic indicator (tetramethylmurexide) method. A loss of electrostatic free enthalpy, Δ(Gel/N)KCa, due to the exchange of Ca2+ → 2K+ cations was determined by potentiometric titrations of the investigated polyacids and pectinic acids of various linear charge density of the macromolecule employing potassium and calcium hydroxides. 2,3-Dicarboxy derivatives of starch and amylose show a considerably strong binding of calcium ions even at low oxidation degree of the starting polysaccharides in contrast to solutions of the corresponding pectinates and carboxymethyl derivatives of cellulose and amylose. The strong bond of calcium ions to 2,3-dicarboxy derivatives of starch and amylose is ascribed to a favourable spatial arrangement of two neighbouring carboxyl groups at C(2) and C(3) of the oxidized D-glucose units due to a flexibility of the macromolecule chain at sites of the pyrane ring cleavage.

Influence of Calcium Ions on the Plant Cell Surface: Membrane Fusions and Conformational Changes

1974 ◽  
Vol 32 ◽  
pp. 154-155
Author(s):  
D. James Morré ◽  
Charles E. Bracker ◽  
William J. VanDerWoude
Keyword(s):  
Cell Wall ◽  
Cell Surface ◽  
Conformational Changes ◽  
Calcium Ions ◽  
Surface Membrane ◽  
Carboxyl Groups ◽  
Cross Linking ◽  
Ultrastructural Evidence ◽  
Glycine Max L ◽  
Wall Extensibility

Calcium ions in the concentration range 5-100 mM inhibit auxin-induced cell elongation and wall extensibility of plant stems. Inhibition of wall extensibility requires that the tissue be living; growth inhibition cannot be explained on the basis of cross-linking of carboxyl groups of cell wall uronides by calcium ions. In this study, ultrastructural evidence was sought for an interaction of calcium ions with some component other than the wall at the cell surface of soybean (Glycine max (L.) Merr.) hypocotyls.

The role of secondary alcoholic groups of D-galacturonan in its degradation with exo-D-galacturonanase

1980 ◽  
Vol 45 (2) ◽  
pp. 427-434 ◽  
Author(s):  
Kveta Heinrichová ◽  
Rudolf Kohn
Keyword(s):  
Acetyl Derivative ◽  
Competitive Inhibitor ◽  
Hydroxyl Groups ◽  
Pectic Acid ◽  
Substrate Complex ◽  
Enzyme Substrate ◽  
The Individual ◽  
Degradation Degree ◽  
Derivatives Of

The effect of exo-D-galacturonanase from carrot on O-acetyl derivatives of pectic acid of variousacetylation degree was studied. Substitution of hydroxyl groups at C(2) and C(3) of D-galactopyranuronic acid units influences the initial rate of degradation, degree of degradation and its maximum rate, the differences being found also in the time of limit degradations of the individual O-acetyl derivatives. Value of the apparent Michaelis constant increases with increase of substitution and value of Vmax changes. O-Acetyl derivatives act as a competitive inhibitor of degradation of D-galacturonan. The extent of the inhibition effect depends on the degree of substitution. The only product of enzymic reaction is D-galactopyranuronic acid, what indicates that no degradation of the terminal substituted unit of O-acetyl derivative of pectic acid takes place. Substitution of hydroxyl groups influences the affinity of the enzyme towards the modified substrate. The results let us presume that hydroxyl groups at C(2) and C(3) of galacturonic unit of pectic acid are essential for formation of the enzyme-substrate complex.

Beziehungen zwischen Rotationsisomerie, Wasserstoffbrücken-Bindung und Substituenteneffekten der organischen Chemie / Relations between Rotational Isomerism, Hydrogen Bonding, and Substituent Effects in Organic Chemistry

1972 ◽  
Vol 27 (6) ◽  
pp. 663-674 ◽  
Author(s):  
Gotthard H. Krause ◽  
Herbert Hoyer
Keyword(s):  
Hydrogen Bonding ◽  
Substituent Effects ◽  
Intramolecular Hydrogen Bonding ◽  
Rotational Isomerism ◽  
Proton Acceptor ◽  
Single Bond ◽  
Free Enthalpy ◽  
Acceptor Group ◽  
Intramolecular Hydrogen ◽  
Derivatives Of

The change of free enthalpy involved in intramolecular hydrogen bonding is smaller if the proton acceptor group can rotate round a single bond, as compared to proton acceptor groups which are fixed in a position optimal for hydrogen bonding. Also, the free enthalpy change is altered when the rotation of the proton acceptor is sterically restricted. This is demonstrated by comparing the absorptions of carbonyl stretching vibrations in the infrared spectra of certain compounds showing rotational isomerism. In the present study derivatives of 5-hydroxy-2,2-dimethyl-6-carbomethoxychromanone- (4), 3-nitrosalicylaldehyde and 3-nitro-2-hydroxy-acetophenones substituted in the position 5 and 6 are examined.

Alkaloids of the Australian Rutaceae: Melicope fareana. IV. Some Reactions of 1-Methyl-4-quinolone-3-carboxyic Acid, a Degradation Product of the Alkaloids

1949 ◽  
Vol 2 (2) ◽  
pp. 272 ◽  
Author(s):  
JR Price
Keyword(s):  
Nitric Acid ◽  
Carboxylic Acid ◽  
Hydrochloric Acid ◽  
Degradation Product ◽  
Carboxyl Groups ◽  
Methyl Groups ◽  
Derivatives Of

Melicopine, melicopidine, and melicopicine are each oxidized by nitric acid to the same acid, C11H9O3N. Decarboxylation gives 1-methyl-4-quinolone (I) and the acid is shown to be 1-methyl-4-quinolone-3-carboxylic acid (II). The 3- and 6- mononitro-, 3,6-dinitro-, and 2-hydroxy-3,6-dinitro- derivatives of 1-methyl-4-quinolone have been prepared and the orientation of the substituents established by oxidation of the hydroxydinitro- compound to 5-nitro-N-methylanthranilic acid. 1-Methy1-4-quinolone-3-carboxylic acid is readily converted to a tetrahydro- derivative. The carboxyl groups in II and in the tetrahydro- acid are reduced by zinc and hydrochloric acid to methyl groups.

scholarly journals The dissociation constants of the carboxyl and hydroxyl groups in some insoluble and sol-forming polysaccharides

1946 ◽  
Vol 185 (1003) ◽  
pp. 431-447 ◽  
Keyword(s):  
Potassium Chloride ◽  
Chloride Ions ◽  
Wheat Starch ◽  
Carboxyl Groups ◽  
Hydroxyl Groups ◽  
Dissociation Curve ◽  
Two Phase ◽  
Pectic Acid ◽  
Phase Systems ◽  
Dissociation Curves

In order to establish the conditions under which the buffering of insoluble substance may most usefully be studied, suspensions of fibre cellulose, hemicellulose and xylan have been examined to determine the relationship between pH and the degree of dissociation of their carboxyl groups. The materials were suspended in normal potassium chloride solution, in order to confine local gradients of hydrion. concentration to the immediate vicinity of each charged buffer group. Under these conditions the dissociation curves are all of the simple Henderson type with a common constant pK = 2·95 (N /100 hydrochloric acid in normal potassium chloride being taken as pH 2 ). Sols of arabic and pectie acid follow the same dissociation curve, showing that the dissociation of the carboxyl groups is not necessarily influenced by the state of aggregation. Within the accuracy of these measurements, uronic and gluconic carboxyls have the same pK . The dissociation of pectic acid departs from the Henderson curve in the same general way as the dissociation curve of maleic acid differs from that of fumaric acid. It is suggested that some of the carboxyls in pectic acid are linked by hydrogen bridges. To a less extent such linkage may also occur in alginic acid below pH 3 when a gel is formed. The pK . for the first stage of acid dissociation of the hydroxyl groups in wheat starch is close to 13·3. The same value was obtained whether potassium hydroxide, calcium hydroxide or barium hydroxide was used. The alkalis were made up in normal solutions of the corresponding chlorides. The same constant holds for alginate within the limits of experimental error. The dissociation in cellulose up to pH 13·5 is much less than in starch. Using a new method based on a determination of the ratio of chloride ions to hydroxyl ions, the dissociations of starch and cellulose were measured in 5N alkali (approximately pH 14·7). The second pK of starch is estimated at roughly 15·0. The cellulose, largely mercerized at this pH, exhibited a dissociation not much less than that of starch, and agreeing closely with the prediction of Neale. An insoluble buffer substance suspended in an electrolyte solution is a two-phase system. The hydrion dissociation can be determined in two-phase systems over a greater pH range than is possible in one-phase systems.

Sign in / Sign up

Export Citation Format

Share Document