Abstract
The fluorescence of thiacyanine (THIA) dye is greatly enhanced on binding to polyanions due to the reduction in internal conversion of the excitation energy of the dye. Glycosaminoglycans (chondroitin sulphates (CS) A, B and C; heparin) and the synthetic polyanion poly(vinylsulphate) (PVS), in addition to enhancing the fluorescence of THIA, facilitate the formation of an exciplex between excited THIA and cool acridine orange (AO), both bound to the polymers. Of the three chondroitin sulphates, chondroitin sulphate C (CSC) is the most efficient in enhancing the fluorescence of THIA and facilitating the formation of an exciplex. The efficiency of heparin in this respect is comparable with that of CSC,and poly(vinyl sulphate) is even more efficient. In 20% (v/v) ethanol the association constant of THIA—CSC is reduced to one-tenth of its value in water. Aqueous ethanol also partially inhibits exciplex formation between the two dyes bound to chondroitin sulphates, although the effect is less prominent in the case of CSC.
Published Version
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