The non-covalent binding and spectroscopic properties of several near-infrared tricarbocyanine dyes to sonicated calf-thymus DNA is reported. The dyes investigated were diethylthiatricarbocyanine iodide (DTTCI), diethyloxatricarbocyanine iodide (DOTCI) and 1,1',3,3,3',3'-hexamethylindotricarbocyanine iodide (HDITCI), which are cationic and possess absorption maxima at 772 nm, 695 nm and 750 nm, respectively, in DMSO. In buffered aqueous solutions, these dyes demonstrated extensive ground state aggregation as seen by gross changes in the NIR absorption spectra. In the presence of double-stranded DNA (dsDNA), the absorption peak in the NIR was restored, indicative of dye-deaggregation. Inspection of the fluorescence emission spectra revealed enhancement ratios of bound-to-free dye ranging from 4.5 for DOTCI to 128 for DTTCI. Scatchard analyses of the dye-dsDNA complexes showed two linear regions, suggestive of at least two possible binding sites on the DNA. For DTTCI, the binding constants were 2.88 X 10⁴ M^-1 and 4.78 X 10³ M^-1.

Date Published: 8 May 1995
PDF: 11 pages
Proc. SPIE 2388, Advances in Fluorescence Sensing Technology II, (8 May 1995); doi: 10.1117/12.208482

Published in SPIE Proceedings Vol. 2388:
Advances in Fluorescence Sensing Technology II
Joseph R. Lakowicz, Editor(s)