Spectroscopic and Binding Properties of Near-Infrared Tricarbocyanine Dyes to Double-Stranded DNA

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The noncovalent binding and spectroscopic properties of several near-infrared tricarbocyanine dyes with respect to sonicated calf-thymus DNA are reported. The dyes investigated were diethylthiatricarbocyanine iodide (DTTCI), diethyloxatricarbocyanine iodide (DOTCI), and 1,1',3,3,3',3'- hexamethylindotricarbocyanine iodide (HITCI), which are cationic and possess absorption maxima at 772, 695, and 750 nm, respectively, in DMSO. In buffered aqueous solutions, these dyes demonstrated extensive ground-state aggregation in aqueous solvents when compared to DMSO. In the presence of double-stranded DNA (dsDNA), the fluorescence emission spectra revealed enhancement ratios of bound-to-free dye ranging from 4.5 for DOTCI to 128 for DTTCI. Spectrophotometric titrations and Scatchard analyses of the dye-dsDNA complexes yielded nonlinear plots, suggestive of possible multiple binding sites on the DNA. Viscometric titrations of the complexes showed increased solution viscosities for DTTCI, consistent with an unraveling and lengthening of the dsDNA upon complexation. Fluorescence lifetime data of the dyedsDNA complexes showed longer lifetimes exhibited by these dyes in the presence of the dsDNA compared with those in solutions with no DNA.

Keywords: Dye/DNA interactions; Near-IR fluorescence

Document Type: Research Article

DOI: http://dx.doi.org/10.1366/0003702963906429

Affiliations: 1: Department of Chemistry, 232 Choppin Hall, Louisiana State University, Baton Rouge, Louisiana 70803-1804; present address: National Institute of Standards and Technology, Gaithersburg, MD 20899 2: Department of Chemistry, 232 Choppin Hall, Louisiana State University, Baton Rouge, Louisiana 70803-1804

Publication date: February 1, 1996

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