Distance Dependence of Single-Fluorophore Quenching by Gold Nanoparticles Studied on DNA Origami
ABSTRACT We study the distance-dependent quenching of fluorescence due to a metallic nanoparticle in proximity of a fluorophore. In our single-molecule measurements, we achieve excellent control over structure and stoichiometry by using self-assembled DNA structures (DNA origami) as a breadboard where both the fluorophore and the 10 nm metallic nanoparticle are positioned with nanometer precision. The single-molecule spectroscopy method employed here reports on the co-localization of particle and dye, while fluorescence lifetime imaging is used to directly obtain the correlation of intensity and fluorescence lifetime for varying particle to dye distances. Our data can be well explained by exact calculations that include dipole-dipole orientation and distances. Fitting with a more practical model for nanosurface energy transfer yields 10.4 nm as the characteristic distance of 50% energy transfer. The use of DNA nanotechnology together with minimal sample usage by attaching the particles to the DNA origami directly on the microscope coverslip paves the way for more complex experiments exploiting dye-nanoparticle interactions.
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ABSTRACT: Superquenching of the laser dye, coumarin 153 (C153), by 16–59 nm gold nanoparticles (AuNPs) is reported from the steady state and time-resolved fluorometric investigations. Quenching of the steady state fluorescence of C153 and its fluorescence lifetime reveals energy transfer from the probe to AuNP in the photoexcited state. The Stern–Volmer constants (KSV, 107–109 mol−1 dm3) determined from the quenching of the donor lifetime in the presence of AuNPs of varying sizes are orders of magnitude higher than those for the normal photochemical quenching processes. The quenching efficiency increases with an increase in the size of the nanoparticles. The importance of the work lies in providing a new and simple system to be exploited for developing biosensor with high degree of sensitivity.Journal of Photochemistry and Photobiology A Chemistry 08/2012; 242:44–50. DOI:10.1016/j.jphotochem.2012.05.027 · 2.29 Impact Factor
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ABSTRACT: We report a gold nanoparticle (AuNP)-based fluorescence quenching system via metal coordination for the simple assay of protease activity. Carboxy AuNPs (5 nm in core diameter) functioned as both quenchers and metal chelators without requiring further modification with multidentate ligands; therefore, they were strongly associated with the hexahistidine regions of dye-tethered peptides in the presence of Ni(II) ions, leading to notable fluorescence quenching over the varying molar ratios of dye to AuNP. Upon the addition of matrix metalloproteinase-7 (MMP-7), the fluorescent intensity was efficiently recovered in one-pot mixture especially at 10:1–100:1 molar ratios of dye to AuNP. Consequently, the dequenching degree was dependent on the MMP-7 concentration in a hyperbolic manner, ranging from as low as 10 to 1,000 ng mL−1. In this regard, we anticipate that the developed system will give us a general way to construct nanoparticle–dye conjugates and will find applications in the analyses of many other proteases mediating significant biological processes with low background and high sensitivity.12/2012; 45(4). DOI:10.1007/s13404-012-0070-9
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ABSTRACT: The DNA origami method is an extraordinarily powerful and robust method for the assembly of almost arbitrarily shaped nanoscale objects made from DNA. Technological advances such as DNA origami and the availability of a range of computational tools have transformed DNA self-assembly from an art into a genuine engineering discipline. Investigators with diverse backgrounds are now beginning to use the origami method in their field of research. Potential applications range from single molecule bio- and nanophysics over structural biology to synthetic biology and nanomedicine. This article discusses the transition of DNA nanotechnology to molecular scale engineering and describes, citing several examples, the power and utility of DNA origami for scientific research.Frontiers in Life Science 06/2012; 6(1-2). DOI:10.1080/21553769.2012.745453 · 0.17 Impact Factor