Abstract
Conventional Förster resonance energy transfer (FRET) processes involving a pair of fluorophore and organic quencher are restricted to an upper distance limit of ~10 nm. The application of a metal nanoparticle as a quencher can overcome the distance barrier of the traditional FRET technique. However, no standard distance dependence of this resonance energy transfer (RET) process has been firmly established. We have investigated the nonradiative energy transfer process between an organic donor (fluorescein) and gold nanoparticle quencher connected by double stranded (ds) DNA. The quenching efficiency of the gold nanoparticle as a function of distance between the donor and acceptor was determined by time-resolved lifetime analyses of the donor. Our results showed a 1/d4 distance dependence for the RET process for longer distances (>10 nm) and 1/d6 distance dependence for shorter distances (<10 nm). Our results clearly indicate the applicability of metal nanoparticle based quenchers for studying systems that exceed the 10 nm FRET barrier.
Highlights
An investigation of molecular interactions and conformational changes of biomolecules such as proteins and nucleic acids is imperative to understand their structural and functional properties [1,2,3,4,5]
The use of metal nanoparticles as an acceptor in the energy transfer process has been claimed to surmount the distance-barrier of the conventional Förster resonance energy transfer (FRET) method, offering a promising alternative to investigate conformational changes of macromolecules [8,9,10] the resonance energy transfer (RET) between the donor fluorophore and the acceptor nanoparticle takes place at a longer distance, no standard rule for its distance dependence has been established [11,12,13]
The FRET process, which follows a 1/d6 distance dependence, is regulated by the electromagnetic coupling of two dipoles involved in the conventional organic donor–acceptor system
Summary
An investigation of molecular interactions and conformational changes of biomolecules such as proteins and nucleic acids is imperative to understand their structural and functional properties [1,2,3,4,5]. Förster resonance energy transfer (FRET), a fluorescence-based “spectroscopic ruler” technique [1], involves the nonradiative energy transfer between a pair of organic donor and acceptor molecules and is an attractive optical method to probe distancedependent structural properties of a molecular system [1,2,3].
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