5 research outputs found
Coherent Exciton Delocalization in a Two-State DNA-Templated Dye Aggregate System
Coherent exciton
delocalization in dye aggregate systems gives
rise to a variety of intriguing optical phenomena, including J- and
H-aggregate behavior and Davydov splitting. Systems that exhibit coherent
exciton delocalization at room temperature are of interest for the
development of artificial light-harvesting devices, colorimetric detection
schemes, and quantum computers. Here, we report on a simple dye system
templated by DNA that exhibits tunable optical properties. At low
salt and DNA concentrations, a DNA duplex with two internally functionalized
Cy5 dyes (i.e., dimer) persists and displays predominantly J-aggregate
behavior. Increasing the salt and/or DNA concentrations was found
to promote coupling between two of the DNA duplexes via branch migration,
thus forming a four-armed junction (i.e., tetramer) with H-aggregate
behavior. This H-tetramer aggregate exhibits a surprisingly large
Davydov splitting in its absorbance spectrum that produces a visible
color change of the solution from cyan to violet and gives clear evidence
of coherent exciton delocalization
DNA-Controlled Excitonic Switches
Fluorescence resonance energy transfer (FRET) is a promising
means
of enabling information processing in nanoscale devices, but dynamic
control over exciton pathways is required. Here, we demonstrate the
operation of two complementary switches consisting of diffusive FRET
transmission lines in which exciton flow is controlled by DNA. Repeatable
switching is accomplished by the removal or addition of fluorophores
through toehold-mediated strand invasion. In principle, these switches
can be networked to implement any Boolean function
Programmable Periodicity of Quantum Dot Arrays with DNA Origami Nanotubes
To fabricate quantum dot arrays with programmable periodicity, functionalized DNA origami nanotubes were developed. Selected DNA staple strands were biotin-labeled to form periodic binding sites for streptavidin-conjugated quantum dots. Successful formation of arrays with periods of 43 and 71 nm demonstrates precise, programmable, large-scale nanoparticle patterning; however, limitations in array periodicity were also observed. Statistical analysis of AFM images revealed evidence for steric hindrance or site bridging that limited the minimum array periodicity
Multiscaffold DNA Origami Nanoparticle Waveguides
DNA origami templated self-assembly
has shown its potential in
creating rationally designed nanophotonic devices in a parallel and
repeatable manner. In this investigation, we employ a multiscaffold
DNA origami approach to fabricate linear waveguides of 10 nm diameter
gold nanoparticles. This approach provides independent control over
nanoparticle separation and spatial arrangement. The waveguides were
characterized using atomic force microscopy and far-field polarization
spectroscopy. This work provides a path toward large-scale plasmonic
circuitry
Modeling and Analysis of Intercalant Effects on Circular DNA Conformation
The
large-scale conformation of DNA molecules plays a critical role in
many basic elements of cellular functionality and viability. By targeting
the structural properties of DNA, many cancer drugs, such as anthracyclines,
effectively inhibit tumor growth but can also produce dangerous side
effects. To enhance the development of innovative medications, rapid
screening of structural changes to DNA can provide important insight
into their mechanism of interaction. In this study, we report changes
to circular DNA conformation from intercalation with ethidium bromide
using all-atom molecular dynamics simulations and characterized experimentally
by translocation through a silicon nitride solid-state nanopore. Our
measurements reveal three distinct current blockade levels and a 6-fold
increase in translocation times for ethidium bromide-treated circular
DNA as compared to untreated circular DNA. We attribute these increases
to changes in the supercoiled configuration hypothesized to be branched
or looped structures formed in the circular DNA molecule. Further
evidence of the conformational changes is demonstrated by qualitative
atomic force microscopy analysis. These results expand the current
methodology for predicting and characterizing DNA tertiary structure
and advance nanopore technology as a platform for deciphering structural
changes of other important biomolecules