Pulse-radiolysis and spectral studies of the interaction of cetylpyridinium chloride and methylene blue with connective-tissue glycosaminoglycans and related compounds.

1. Hydrated electrons produced by pulse radiolysis were used to study the interaction of polyanionic glycosaminoglycans and related compounds with the counterions Methylene Blue and cetylpyridinium chloride. 2. The effect of added salt (potassium chloride) on the interaction indicates that the relative binding affinities, with respect to the types of anionic site present, increases for both counterions in the order CO(2) (-)<CO(2) (-)+O.SO(3) (-)<CO(2) (-)+O.SO(3) (-) +N.SO(3) (-)<O.SO(3) (-). The interactions of the polyanions with cetylpyridinium chloride are considerably stronger than those with Methylene Blue. 3. The effects of added salt on the metachromasia resulting from polyanion-Methylene Blue interaction were examined spectrophotometrically. 4. The collective results demonstrate a direct relationship between anionic site-dye binding and metachromasia, although a residual dye binding can be detected by pulse radiolysis when metachromasia is completely removed.