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Photonics of Trimethine Cyanine Dyes as Probes for Biomolecules

“…In particular, in [ 111 ], when studying the noncovalent interaction of dye 15 with dsDNA, an increase in the quantum yield of intersystem crossing of 15 to the T state in a complex with DNA was found. The decay kinetics of the T state of the dye in the presence of dsDNA were biexponential, which corresponded to the T states of two types of dye–DNA complexes, probably surface (in the groove) and intercalation complexes, which had different spectral and kinetic characteristics.…”

“…Quenching of the T states of trimethine cyanine dyes by dissolved oxygen (O 2 ) in complexes with DNA was studied in a number of works [ 31 , 38 , 42 , 106 , 111 , 112 ]. It occurs much more slowly than in the absence of DNA (with sensitization of triplet states of the dyes in the solution).…”

“…When T states of the dyes are quenched by O 2 by the mechanism of energy transfer to form singlet oxygen ( 1 O 2 ), the diffusion-controlled quenching rate constant k q (O 2 ) includes the spin-statistical factor 1/9, and in water one can expect k q (O 2 ) = 1/9 k dif ~3 × 10 9 mol −1 L s −1 . Indeed, k q (O 2 ) was found to be 1.2 × 10 9 mol −1 L s −1 upon oxygen quenching of dye 15 T state sensitized by sodium anthracene-2-sulfonate in water [ 111 ].…”

“…The values of k q (O 2 ) in complexes with ds- and ssDNA were found to be significantly lower than 1/9 k dif , which indicates significant steric hindrances to the quenching process in the complexes. For example, in a complex with dsDNA of dye 15 (DTC), k q (O 2 ) = 1.5 × 10 8 and 4.5 × 10 8 mol −1 L s −1 were found for the short-lived and long-lived T components, respectively [ 111 ]; for dye 20, this was k q (O 2 ) = 4.3 × 10 8 mol −1 L s −1 , and for 21 , this was k q (O 2 ) = 6.0 × 10 8 mol −1 L s −1 [ 42 ]. In the case of ssDNA for 20 k q (O 2 ) = 3.0 × 10 8 mol −1 L s −1 [ 30 ].…”

Synthesis, absorption and fluorescence spectral characteristics of trinucleus dimethine cyanine dyes as fluorescent probes for DNA detection

“…The fluorescence enhancement of trinucleus dimethine cyanine dyes bound to DNA was attributable to the fact that on photoexcitation a lack of free rotation around the internuclear bridge made isomerisation around the C-C bonds of the methine chain difficult; and subsequently nonradiative deactivation of the excited state was not possible, causing the dye to fluoresce. 22,23 Upon binding with DNA, 3a-3d maintained their high Stokes shift and showed a red shift, owing to a more efficient ICT in the excited state between the terminal heterocyclic aromatic and the pyridimium group.…”