Formation of trans-2-[4-(dimethylamino)styryl]-3-ethyl-1,3-nzothiazolium perchlorate dimers in the presence of sodium polystyrene sulfonate formation of trans-2-[4-(dimethylamino)styryl]-3-ethyl-1,3-benzothiazolium perchlorate dimers in the presence of sodium polystyrene sulfonate

Abstract

The spectral properties of a novel thiofl avin T derivative, trans-2-[4-(dimethylamino)styryl]-3-ethyl-1,3- benzothiazolium perchlorate (DMASEBT), were studied in aqueous solutions in the presence of sodium polystyrene sulfonate (SPS). It was shown that SPS either could interact with dye monomers or initiate the formation of non-fl uorescent dye dimers depending on the concentration ratio of dye and polyelectrolyte. DMASEBT dimer formation in the presence of SPS produced a hypsochromic shift by 40 nm in the absorption spectrum and quenched fl uorescence. A bathochromic shift of the absorption spectrum and an increase of the fl uorescence intensity by an order of magnitude were observed if DMASEBT monomers interacted with SPS. Quantum-chemical analysis found that sandwich dimers (H-aggregates) were most stable. A comparison of DMASEBT spectra in the presence of SPS and amyloid fi brils showed that DMASEBT molecules were incorporated into amyloid fi brils as monomers. The spectral changes associated with this incorporation could not be explained by the formation of dye aggregates.