The two dimensional structure of tetrazolium-mucopolysaccharide complexes deduced from reactivity studies

The formation of complexes between mucopolysaccharides and tetrazolium salts has been studied both by turbidimetry and nephelometry. The technique of laser nephelometry allows the detection of colloidal aggregates in systems which may, by turbidimetric methods, be ambiguous. The results indicate that binding of tetrazolium salts to polyanions can result in soluble as well as insoluble complexes; the monotetrazolium salts form soluble complexes and the ditetrazolium compounds form insoluble complexes. The insoluble complexes are stable at relatively low pH, and are disrupted during reduction to the formazan. Complex formation is decreased at high ratios of heparin to tetrazolium, and divalent cations, even at high concentration, do not precipitate mucopolysaccharides. It is concluded that stable ionic interactions with spatial charge separation are responsible for the cross linking of the mucopolysaccharides and the formaiton of large insoluble aggregates.