Probes cyanine

Long-Wavelength Probes and Labels Based on Cyanines... 

Reference [33] describes recent progress on cyanine probes that bind noncova-lently to DNA, with a special emphasis on the relationship between the dye structure and the DNA binding mode. Some of the featured dyes form well-defined helical aggregates using DNA as a template. This reference also includes spectroscopic data for characterizing these supramolecular assemblies as well as the monomeric complexes. 

Compared to oxo-squaraines or other ring-substituted squaraines, amino-squaraines 39 [45, 52, 112] have ionic character, similar to open-chain cyanine dyes, and due to the positive net charge, these dyes are to some extend water-soluble. Amino-squaraines absorb and emit at longer wavelength than the corresponding oxo-squaraines the absorption maxima are between 650-710 nm (eM = 85,000-300,000 M-1cm-1) [45, 112], The increase in solvent polarity is accompanied by a hypsochromic shift of the absorption. Amino-squaraine dyes are potentially used as fluorescent probes but because their photostability is inferior to those of oxo-squaraines and other ring substituted squaraines of similar structure, their applications are rather limited. 

Due to their low sensitivity toward the environment, cyanine dyes are perfect candidates as fluorescent labels. Squaraine dyes on the other hand display a highly environment-sensitive response and are therefore not only useful as fluorescent probes and labels but also, in particular, well-suited for lifetime-based applications. 

Due to their displayed higher photostability, indolenine-based cyanines and squaraines are preferred for the design of fluorescent tracers. Dicyanomethylene- and thio-squaraines with substituted squaraine oxygens also show potential as highly photostable fluorescent probes. 

Sato S, Tsunoda M, Suzuki M, Kutsuna M, Takido-uchi K, Shindo M, Mizuguchi H, Obara H, Ohya H (2009) Synthesis and spectral properties of polymethine-cyanine dye-nitroxide radical hybrid compounds for use as fluorescence probes to monitor reducing species and radicals. Spectrochim Acta A 71 2030-2039... 

Licha K, Hessenius C, Becker A, Henklein P, Bauer M, Wisniewski S, Wiedenmann B, Semmler W (2001) Synthesis, characterization, and biological properties of cyanine-labeled somatostatin analogues as receptor-targeted fluorescent probes. Bioconjugate Chem 12 44—50... 

Keywords Cyanine dyes Excited state absorption Polymethine dyes Pump-probe Two-photon absorption Z-scan... 

Kiyose K, Kojima H, Urano Y et al (2006) Development of a ratiometric fluorescent zinc ion probe in near-infrared region, based on tricarbo-cyanine chromophore. J Am Chem Soc 128 6548-6549... 

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