Potassium pectate

Fig. 11.1. The CD spectra of the individual acidic polysaccharides and polypeptides (7) potassium pectate (2) alginate rich in L-guluronate (3) alginate rich in D-mannuronate 4) poly(L-lysine) (5) poly(D-lysine) ...

The CD spectra of d- and L-polylysines in the presence of potassium pectate are given in Figs. 11.2 and 11.3. The spectral shape of complexes with poly(L-lysine) clearly indicates the presence of induced a-helical structure. 

Fig. 113. The CD spectrum of poly(D-lysine), in the presence of potassium pectate potassium pectate with addition of 20% (/), 40% (2), 60% (5), 80% 4) and 100% (5) poly(D-Iysine)...

Calcium is important in the growth of meristematic tissues including both shoot and root tips. It frequently accumulates in cell walls and leaves in the form of calcium pectate. Calcium also apparently acts as an activator for certain enzymes and performs other metabolic functions that are not yet clearly defined. It seems to neutralize to some extent the undesirable effects of nutrients in the plant that are either undesirable or absorbed in improper amounts or ratios. Too much calcium may, however, depress the uptake of potassium and magnesium, but unlike these elements it is comparatively immobile in the plant. 

A series of O-acetyl derivatives of pectic acid has been prepared to study the intramolecular binding of Ca + ions to pectic acids. The electrostatic free enthalpy of dissociation of these polyacids and the rate of exchange of the counter-ion from Ca + to K+ were determined by potentiometric titration measurements. The binding of Ca + ions was characterized by the production of single ion affinity coefficients determined in solutions of the calcium salts of 0-acetyl pectic acids and by the circular dichroism measurements of calcium and potassium salts of the pectate derivatives. The intramolecular binding of Ca + ions to isolated pectate macromolecules is purely of electrostatic character in contrast to the intermolecular chelate binding of Ca + ions which takes place when the pectate macromolecules aggregate. 

These non-esterified galacturonic acid entities may be free acid or salts, with sodium, potassium, or calcium as the counter ion. The partly esterified pectin salts are further named pectinates, and the degree of esterification below 5%, was coined as pectates. 

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