Binding of calcium ions to acetyl derivatives of pectin

1968 ◽  
Vol 33 (7) ◽  
pp. 2217-2225 ◽  
Author(s):  
R. Kohn ◽  
I. Furda
Keyword(s):  
Calcium Ions ◽  
Derivatives Of

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.

Activation of Prothrombin

1956 ◽  
Vol 186 (2) ◽  
pp. 343-349 ◽  
Author(s):  
John A. Penner ◽  
Walter H. Seegers
Keyword(s):  
Calcium Ions ◽  
Platelet Factor ◽  
Derivatives Of ◽  
Prothrombin Activation

In the activation of a prothrombin solution, only part of the prothrombin becomes biothrombin, some becomes autoprothrombin I and some becomes autoprothrombin II. Thrombin-thrombin is also obtained, and perhaps other derivatives of prothrombin are formed. Prothrombin thus has multiple potentialities and these can be developed in diverse ways. Ac-globulin, calcium ions and platelet factor 3 can be used to obtain autoprothrombin I. Thrombin and Ac-globulin transforms prothrombin to autoprothrombin II, while platelet factor 3 or calcium ions tend to inhibit the transformation. Since calcium ions and platelet factor 3 also function as activators in one of the prothrombin to biothrombin reactions they are either activators or inhibitors of prothrombin activation depending upon the specified conditions.

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.

Mitochondrial matrix calcium ions regulate energy production in myocardium: A cytochemical study

1990 ◽  
Vol 48 (2) ◽  
pp. 166-167
Author(s):  
W.A. Jacob ◽  
R. Hertsens ◽  
A. Van Bogaert ◽  
M. De Smet
Keyword(s):  
Energy Metabolism ◽  
Calcium Ions ◽  
Energy Production ◽  
Regulation Of Respiration ◽  
Free Calcium ◽  
Mitochondrial Matrix ◽  
Cytochemical Study ◽  
Nmr Techniques

In the past most studies of the control of energy metabolism focus on the role of the phosphorylation potential ATP/ADP.Pi on the regulation of respiration. Studies using NMR techniques have demonstrated that the concentrations of these compounds for oxidation phosphorylation do not change appreciably throughout the cardiac cycle and during increases in cardiac work. Hence regulation of energy production by calcium ions, present in the mitochondrial matrix, has been the object of a number of recent studies.Three exclusively intramitochondnal dehydrogenases are key enzymes for the regulation of oxidative metabolism. They are activated by calcium ions in the low micromolar range. Since, however, earlier estimates of the intramitochondnal calcium, based on equilibrium thermodynamic considerations, were in the millimolar range, a physiological correlation was not evident. The introduction of calcium-sensitive probes fura-2 and indo-1 made monitoring of free calcium during changing energy metabolism possible. These studies were performed on isolated mitochondria and extrapolation to the in vivo situation is more or less speculative.

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