Synthesis of water-soluble, ring-substituted squaraine dyes and their evaluation as fluorescent probes and labels was written by Tatarets, Anatoliy L.;Fedyunyayeva, Irina A.;Dyubko, Tatyana S.;Povrozin, Yevgeniy A.;Doroshenko, Andrey O.;Terpetschnig, Ewald A.;Patsenker, Leonid D.. And the article was included in Analytica Chimica Acta in 2006.Reference of 146368-07-2 This article mentions the following:
A series of ring-substituted squaraines absorbing and emitting in the red and NIR spectral region was synthesized and their spectral and photophys. properties (quantum yields, fluorescence lifetimes) and photostabilities were measured and compared to Cy5, a commonly used fluorescent label. The absorption maxima in aqueous media were between 628 and 667 nm and the emission maxima are between 642 and 685 nm. Squaraine dyes exhibit high extinction coefficients (163,000-265,000 M-1 cm-1) and lower quantum yields (2-7%) in aqueous buffer but high quantum yields (up to 45%) and long fluorescence lifetimes (up to 3.3 ns) in presence of BSA. Dicyanomethylene- and thio-substituted squaraines exhibit an addnl. absorption around 400 nm with extinction coefficients between 21,500 and 44,500 M-1 cm-1. These dyes are excitable not only with red but also with blue diode lasers or light emitting diodes. Due to the favorable spectral and photophys. properties these dyes can be used as fluorescent probes and labels for intensity- and fluorescence lifetime-based biomedical applications. In the experiment, the researchers used many compounds, for example, 1-Ethyl-2,3,3-trimethyl-3H-indol-1-ium-5-sulfonate (cas: 146368-07-2Reference of 146368-07-2).
1-Ethyl-2,3,3-trimethyl-3H-indol-1-ium-5-sulfonate (cas: 146368-07-2) belongs to indole derivatives. Indole exists overwhelmingly in the 1H-indole form as do other simple indoles. They are capable of binding to a variety of receptors with high affinity and thus have applications in a wide range of therapeutic areas.Reference of 146368-07-2
Referemce:
Indole alkaloid derivatives as building blocks of natural products from聽Bacillus thuringiensis聽and聽Bacillus velezensis聽and their antibacterial and antifungal activity study,
Preparation of Indole Containing Building Blocks for the Regiospecific Construction of Indole Appended Pyrazoles and Pyrroles