Probing the amyloid protein aggregates with unsymmetrical monocationic trimethine cyanine dyes

Interaction of Novel Monomethine Cyanine Dyes with Proteins in Native and Amyloid States

“…All above findings show that despite the positive ADF values, the dyes under study readily associate also with the monomeric (native) proteins. It should also be noted that despite the observed positive ADF values of the cyanine dyes under study, their amyloid specificity is significantly lower in comparison with other amyloid markers [24][25][26][27][28]. In particular the estimated ADF values for the previously reported trimethine cyanine dyes [24] and phenyleneethynylene-based dyes [25] were about twice as large as those calculated in the present work.…”

“…It should also be noted that despite the observed positive ADF values of the cyanine dyes under study, their amyloid specificity is significantly lower in comparison with other amyloid markers [24][25][26][27][28]. In particular the estimated ADF values for the previously reported trimethine cyanine dyes [24] and phenyleneethynylene-based dyes [25] were about twice as large as those calculated in the present work. Moreover, the enhancement of the fluorescence intensity (ratio 0 / f I I ) in the presence of amyloid fibrils for the all dyes under investigation didn't exceed 10, while for some cyanine dyes [24,26], benzanthrone derivatives [27] and β-ketoenoles [28] binding preferences were significantly higher (values of 0 / f I I ratios were more than 50).…”

“…In particular the estimated ADF values for the previously reported trimethine cyanine dyes [24] and phenyleneethynylene-based dyes [25] were about twice as large as those calculated in the present work. Moreover, the enhancement of the fluorescence intensity (ratio 0 / f I I ) in the presence of amyloid fibrils for the all dyes under investigation didn't exceed 10, while for some cyanine dyes [24,26], benzanthrone derivatives [27] and β-ketoenoles [28] binding preferences were significantly higher (values of 0 / f I I ratios were more than 50). Specifically, the binding of a homodimeric derivative of oxazole yellow YOYO to amyloid fibrils was found to be accompanied by a 200-fold emission enhancement [14].…”

“…Notably, the sensitivity of the dye spectral properties to the changes in the protein environment was previously reported for Michler's hydrol blue and Nile red [22,23]. To determine the specificity of the examined cyanines to amyloid fibrils, the fluorescence spectral data were processed to the amyloid detection factor (ADF) characterizing the ability of a dye to selectively detect the fibrillar state over its native structure relative to the background fluorescence of the dye in buffer [24,25]:…”

Near-infrared fluorescent probes based on a quinoxaline skeleton for imaging nucleic acids in mitochondria

“…Traditional cyanine dyes have the advantages of large molar absorption coefficients and high fluorescence quantum yields through the adjustment of conjugate chain lengths, and the absorption spectra of cyanine dyes can be extended to the near-infrared region. [21][22][23][24][25] Besides, some heterocyclic compounds that contain nitrogen atoms are generally used as DNA insertions, and a positive charge enhances the tendency of molecules to bind to the DNA. [26][27][28][29] In view of the above points, two hemicyanine probes 1a and 1b, in which bioactive quinoxalinium was used to replace the salt structure in traditional cyanine dyes, were synthesized.…”