Spectroscopic study of cyanine dyes interacting with the biopolymer, DNA

Nanostructuring Lipophilic Dyes in Water Using Stable Vesicles, Quatsomes, as Scaffolds and Their Use as Probes for Bioimaging

“…On the contrary, when loaded with DiD and DiR, the formation of nonfluorescent aggregates determines a rapid decrease of the FONs' brightness. Thus, cyanines with longer conjugated structures experience stronger π–π interactions upon nanostructuration, as observed in previous works where cyanines with different polymethine chain sizes were intercalated into DNA strands …”

“…Thus, cyanines with longer conjugated structures experience stronger π-π interactions upon nanostructuration, as observed in previous works where cyanines with different polymethine chain sizes were intercalated into DNA strands. [31] Photostability of DiD in EtOH and of DiD-loaded QSs in water was analyzed by monitoring the evolution over time of the absorbance under continuous laser irradiation ( Figure S9, Supporting Information). Relevant photodecomposition quantum yields, determined according to the Belfield method, [32] were obtained (see Table S2 in the Supporting Information).…”

DNA Photocleavage in the Near-Infrared Wavelength Range by 2-Quinolinium Dicarbocyanine Dyes

“…In contrast, individual groove-bound monomers and groove-bound dimers do not exhibit exciton coupling and instead tend to generate positive ICD signals [7,45]. The ICDs of cyanine intercalators are relatively weak and are either positive [45] or negative [5,43,46], depending on the orientation of the transition moment of the dye relative to the dyad axis of the DNA duplex [47]. This being said, we recorded circular dichroism spectra of brominated dye 4 as a function of increasing CT DNA concentration.…”

“…In our first experiment, absorption titrations were conducted in which small amounts of CT DNA titrant were sequentially added to a solution containing a fixed amount of dye 4 ( Figure 5). Raising DNA concentration is known to disrupt cyanine aggregation in favor of the formation monomeric dye [5,7,42]. These changes in aggregation state are often reflected in the absorption spectra of the dye.…”

“…These features make it possible for the monomeric and/or aggregated forms of many carbocyanine dyes to form stable complexes with double-helical DNA. Modes of cyanine binding, which include intercalation, groove binding, and external electrostatic interactions, depend upon the structure and aggregation state of the dye [4][5][6][7]. Many cyanines exhibit excellent optical properties that include high absorption coefficients, high fluorescence quantum yields, and absorption and emission maxima that are easily tuned by alternating terminal heterocyclic groups and by lengthening the dye's central polymethine chain.…”