ph6b00006_si_001.pdf (841.06 kB)
FRET from Multiple Pathways in Fluorophore-Labeled DNA
journal contribution
posted on 2016-02-24, 00:00 authored by Joseph S. Melinger, Ani Khachatrian, Mario
G. Ancona, Susan Buckhout-White, Ellen R. Goldman, Christopher M. Spillmann, Igor L. Medintz, Paul D. CunninghamBecause of their ease of design and
assembly, DNA scaffolds provide
a valuable means for organizing fluorophores into complex light harvesting
antennae. However, as the size and complexity of the DNA–fluorophore
network grows, it can be difficult to fully understand energy transfer
properties because of the large number of dipolar interactions between
fluorophores. Here, we investigate simple DNA–fluorophore networks
that represent elements of the more complex networks and provide insight
into the Förster Resonance Energy Transfer (FRET) processes
in the presence of multiple pathways. These FRET networks consist
of up to two Cy3 donor fluorophores and two Cy3.5 acceptor fluorophores
that are linked to a rigid dual-rail DNA scaffold with short interfluorophore
separation corresponding to 10 DNA base pairs (∼34 Å).
This configuration results in five FRET pathways: four hetero-FRET
and one homo-FRET pathway. The FRET properties are characterized using
a combination of steady-state and time-resolved spectroscopy and understood
using Förster theory. We show that the multiple FRET pathways
lead to an increase in FRET efficiency, in part because homo-FRET
between donor fluorophores provides access to parallel pathways to
the acceptor and thereby compensates for low FRET efficiency channels
caused by a static transition dipole distribution. More generally,
the results show that multiple pathways may be used in the design
of artificial light harvesting devices to compensate for inhomogeneities
and nonideal ensemble effects that degrade FRET efficiency.