6 research outputs found
Legislative Documents
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Leaving Förster Resonance Energy Transfer Behind: Nanometal Surface Energy Transfer Predicts the Size-Enhanced Energy Coupling between a Metal Nanoparticle and an Emitting Dipole
The interaction of a fluorescent
molecule with a gold nanoparticle
is complex and can lead to excited-state enhancement or quenching.
Many attempts have been made to explain the observed interaction when
in close proximity to the metal surface; yet no single model has been
capable of explaining the observations. In this work, we show that
by accurately describing the interaction in terms of an induced image
dipole modified within the gold nanoparticle by the size-dependent
changes in absorptivity and dielectric constant, the oscillator interaction
can be fully described in terms of a surface-moderated interaction.
Comparison of experimental and theoretical data confirms the validity
of the model for a selected range of separation distances, nanoparticle
radii, and fluorescent molecule selection. The results of the study
illustrate the importance of nonradiative pathways for modifying the
decay of a fluorescent molecule by coupling to the image dipole, thus
providing a firm understanding of the reported variance in behavior
for an emitting species in close proximity to nanometal surfaces.
A more significant impact of the results is the ability to apply nanometal
surface energy transfer methods as a molecular ruler to probe physical
questions at much greater distances (>400 Ã…) than previously
achievable
Triangulating Nucleic Acid Conformations Using Multicolor Surface Energy Transfer
Optical
ruler methods employing multiple fluorescent labels offer
great potential for correlating distances among several sites, but
are generally limited to interlabel distances under 10 nm and suffer
from complications due to spectral overlap. Here we demonstrate a
multicolor surface energy transfer (McSET) technique able to triangulate
multiple points on a biopolymer, allowing for analysis of global structure
in complex biomolecules. McSET couples the competitive energy transfer
pathways of Förster Resonance Energy Transfer (FRET) with gold-nanoparticle
mediated Surface Energy Transfer (SET) in order to correlate systematically
labeled points on the structure at distances greater than 10 nm and
with reduced spectral overlap. To demonstrate the McSET method, the
structures of a linear B-DNA and a more complex folded RNA ribozyme
were analyzed within the McSET mathematical framework. The improved
multicolor optical ruler method takes advantage of the broad spectral
range and distances achievable when using a gold nanoparticle as the
lowest energy acceptor. The ability to report distance information
simultaneously across multiple length scales, short-range (10–50
Å), mid-range (50–150 Å), and long-range (150–350
Ã…), distinguishes this approach from other multicolor energy
transfer methods
Plasmid Transfection in Mammalian Cells Spatiotemporally Tracked by a Gold Nanoparticle
Recent advances in cell transfection have suggested that delivery of a gene on a gold nanoparticle (AuNP) can enhance transfection efficiency. The mechanism of transfection is poorly understood, particularly when the gene is appended to a AuNP, as expression of the desired exogenous protein is dependent not only on the efficiency of the gene being taken into the cell but also on efficient endosomal escape and cellular processing of the nucleic acid. Design of a multicolor surface energy transfer (McSET) molecular beacon by independently dye labeling a linearized plasmid and short duplex DNA (sdDNA) appended to a AuNP allows spatiotemporal profiling of the transfection events, providing insight into package uptake, disassembly, and final plasmid expression. Delivery of the AuNP construct encapsulated in Lipofectamine2000 is monitored in Chinese hamster ovary cells using live-cell confocal microscopy. The McSET beacon signals the location and timing of the AuNP release and endosomal escape events for the plasmid and the sdDNA discretely, which are correlated with plasmid transcription by fluorescent protein expression within the cell. It is observed that delivery of the construct leads to endosomal release of the plasmid and sdDNA from the AuNP surface at different rates, prior to endosomal escape. Slow cytosolic diffusion of the nucleic acids is believed to be the limiting step for transfection, impacting the time-dependent expression of protein. The overall protein expression yield is enhanced when delivered on a AuNP, possibly due to better endosomal escape or lower degradation prior to endosomal escape