Nanometal Surface Energy Transfer in Optical Rulers, Breaking the FRET Barrier

Abstract

Optical-based distance measurements are essential for tracking biomolecular conformational changes, drug discovery, and cell biology. Traditional Forster resonance energy transfer (FRET) is efficient for separation distances up to 100 A. We report the first successful application of a dipole-surface type energy transfer from a molecular dipole to a nanometal surface that more than doubles the traditional Forster range (220 A) and follows a 1/R(4) distance dependence. We appended a 1.4 nm Au cluster to the 5' end of one DNA strand as the energy acceptor and a fluorescein (FAM) to the 5' end of the complementary strand as the energy donor. Analysis of the energy transfer on DNA lengths (15, 20, 30, 60bp), complemented by protein-induced DNA bending, provides the basis for fully mapping the extent of this dipole surface type mechanism over its entire usable range (50-250 A). Further, protein function is fully compatible with these nanometal-DNA constructs. Significantly extending the range of optical based methods in molecular rulers is an important leap forward for biophysics.

Experimental and Theoretical Investigation of the Distance Dependence of Localized Surface Plasmon Coupled Förster Resonance Energy Transfer

“…Plasmonic structures provide a route towards longer range non-radiative energy transfer (NRET) via nanometal surface energy transfer (NSET) or localised surface plasmon (LSP) coupled FRET. 5,6 The near-field of the plasmonic structure can modify the emission of a fluorophore. [7][8][9][10][11][12] Depending on the plasmonic properties of the metallic nanoparticle (MNP) it can lead to quenching or enhancement of the fluorophore emission.…”

Fluorescence quenching in graphene: A fundamental ruler and evidence for transverse plasmons

“…24 This law has repeatedly been found in subsequent studies of energy transfer involving various kinds of nanomaterials. 25 For graphene, the topic has been discussed by Swathi and Sebastian, treating the (instantaneous) longitudinal coupling between graphene and fluorescent material to lowest order, and again obtaining the z −4 law. 26 Here, we extend their calculations in three significant ways: (i) we include transverse decay channels in the calculations, (ii) the coupling between graphene and the electromagnetic field is taken to all orders, and (iii) we use the full (retarded) photon propagator.…”

Peptide-mediated core/satellite/shell multifunctional nanovehicles for precise imaging of cathepsin B activity and dual-enzyme controlled drug release

“…Theoretical and experimental studies have shown that the distance-dependent quenching of gold nanoparticles with diameters of 1-20 nm follow a 1/r 4 relationship, and this is termed NSET. 33 Unlike the Förster resonance energy transfer, whose efficiency is markedly dependent upon the spectral overlap level and separation distance (o10 nm) between the donor fluorophore and the acceptor fluorophore, NSET maintains the quenching character even with a separation distance of 22 nm, ensuring that the majority of the dye doped in the mesoporous silica hollow shell (thickness~20 nm) can be quenched. Thus, the hollow structure of the FHMSNs and the high sensitivity of NSET determines the high quenching efficiency, 34 creating a sensitive signal for probing proteases in living systems.…”