The property of certain biological compounds to change the color of such dyes as toluidine blue or thionine. For example, glycosaminoglycans/proteoglycans found in cartilage matrix and mast cell granules will stain red or violet instead of blue with toluidine blue. The phenomenon is apparently caused by a change in the electronic structure of the dye molecule as it interacts with the electrons of the binding polymer and other dye molecules.
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