Bulk and single-molecule fluorescence studies of the saturation of the DNA double helix using YOYO-3 intercalator dye
- J Phys Chem B. 2012 Sep 27;116(38):11561-9. doi: 10.1021/jp303438d.
- 1. Department of Physical Chemistry, Faculty of Pharmacy, University of Granada, Cartuja Campus, 18071, Granada, Spain.
We report a thorough photophysical characterization of the interactions between double-stranded DNA (dsDNA) and the trimethine cyanine homodimer dye YOYO-3. The fluorescence emission of this dye is enhanced by intercalation within the DNA double helix. We have explored the saturation of the dsDNA by bound YOYO-3 at the single-molecule level by studying the single-pair Förster resonance energy transfer (FRET) from an energy donor, Alexa Fluor 488, tagged at the 5' end of the double helix and the energy acceptor, YOYO-3, bound to the same DNA molecule. The spontaneous binding of YOYO-3 gives rise to an effective distribution of different FRET efficiencies and, therefore, donor-acceptor (D-A) distances. These distributions reveal the existence of multiple states of YOYO-3. Steady-state and time-resolved fluorescence and circular dichroism confirmed the presence of a DNA-bound aggregate of YOYO-3, conspicuous at high dye/base pair ratios. The spectral features of the aggregate suggest that it may have the structure of a parallel H-aggregate.
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Research Areas: Others