Quantitative Aspects of the Interaction of Carrageenan and Other Hydrocolloids with Polyvalent Cobalt Complexes

Abstract

SUMMARYCarrageenan, other sulfated polysaccharides, and carboxylic acid polysaccharides react with hexol nitrate, hexamine cobaltic chloride, and tris‐(ethylenediamine) ‐cobalt III chloride in aqueous solution to give precipitates which exhibit differential solubilities in solutions of simple salts. The turbidity (optical density) produced when the hydrocolloids are mixed with these cobalt complexes is proportional to the amount of hydrocolloid present. Salts inhibit the reaction, and, generally, the order of inhibition is: monovalent cations < divalent cations < trivalent cations.The temperature and pH of the reaction medium greatly influence the final turbidity developed. Generally, the complexes formed through the reaction of the sulfated polysaccharides and the cobalt complexes are less readily dissolved by solutions of simple salts than those formed by the carboxylic polysaccharides and the cobalt complexes. Neutral polysaccharides are not precipitated by the cobalt complexes, hence three component systems containing a sulfated, a carboxylic, and a neutral polysaccharide can be resolved and the individual components determined quantitatively. Good resolution was obtained with a mixture such as carrageenan (sulfated) plus algin (carboxylic) plus locust bean gum (neutral).Quantitative assay of those polysaccharides which form precipitates (turbidity) with the complexes can be done either by measuring the turbidity developed or by determining spectrophotometrically the amount of cobalt complex cation bound. These colored complexes have sharp absorption maxima: hexol nitrate, max = 490 mμ; hexaminecobalt chloride, max = 475 mμ; and tris‐(ethylenediamine)‐cobalt III chloride, max = 470 mμ.

On the Biology of Werner's Complex

“…The redox and magnetic properties of Co coordination complexes suggest possibilities for their use in imaging, diagnostics, and therapy [46, 47] . Earlier studies had examined briefly the use of Co complexes as analytical probes for sulfated GAG content, [48–52] but no effects on function were examined. A wide range of metal complexes may display antiviral activity, [53] but the results here point to the potential for target‐based rational development.…”

On the Biology of Werner's Complex

“…Ther edox and magnetic properties of Co coordination complexes suggest possibilities for their use in imaging,diagnostics,and therapy. [46,47] Earlier studies had examined briefly the use of Co complexes as analytical probes for sulfated GAGc ontent, [48][49][50][51][52] but no effects on function were examined. Aw ide range of metal complexes may display antiviral activity, [53] but the results here point to the potential for target-based rational development.…”

Glycans as Ligands in Bioinorganic Chemistry. Probing the Interaction of a Trinuclear Platinum Anticancer Complex with Defined Monosaccharide Fragments of Heparan Sulfate

“…The O -donor polyanions of glycan biomolecules may be receptors and possible targets in their own right for coordination compounds . Examples include the interaction of chromium­(V) compounds with sialic acids and its relevance to the toxicity and metabolism of chromium species ,, and the use of ruthenium bipyridines as fluorescent probes of heparin concentration. − Cobalt­(III) ammine complexes have also been proposed for the quantification of sulfated glycans including in clinical studies. − These apparently disparate examples testify to the broad relevance of metalloglycomics. Glycans offer a wide variety of binding possibilities from purely carboxylate-based (sialic acids and hyaluronan) to the mixed carboxylated and sulfated GAGs including heparin and heparan sulfate (HS) and the related dermatan and chondroitin sulfates .…”