Quantum dot-based resonance energy transfer and its growing appliaction in biology. Phys Chem Chem Phys
ABSTRACT We provide an overview of the progress made in the past few years in investigating fluorescence resonance energy transfer (FRET) using semiconductor quantum dots (QDs) and the application of QD-based FRET to probe specific biological processes. We start by providing some of the pertinent conceptual elements involved in resonance energy transfer, and then discuss why the Förster dipole-dipole mechanism applies to QD fluorophores. We then describe the unique QD photophysical properties of direct relevance to FRET and summarize the main advantages offered, along with some of the limitations encountered by QDs as exciton donors and/or acceptors. Next we describe the overall progress made and discuss a few representative examples where QD-based FRET sensing of specific biological processes has been demonstrated. We also detail some of the advances of single molecule FRET using QD-conjugates and highlight the unique information that can be extracted. We conclude by providing an assessment of where QD-based FRET investigations may be evolving in the near future.
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- "Therefore, an exciton is trapped in the CdSe core of the QDs. The overall exciton wave function is confined within the physical dimension of the nanocrystal and essentially localized at the center of the QDs vanishing at its edge . EET occurs between the confined lowest excited state in the CdSe quantum well and the absorbing S 0 → S 1 transition of the PCB chromophores. "
ABSTRACT: The present work describes results obtained on hybrid systems formed in aqueous buffer solution by self-assembly of different CdSe quantum dots (QDs) surrounded by a ZnS shell and functionalized by covering the surface with anionic and cationic groups and various isolated pigment-protein complexes from the light-harvesting antennae of photosynthetic organisms (light-harvesting complexes 1 and 2 (LH1 and LH2, respectively) from purple bacteria, phycobiliproteins (PBPs) from cyanobacteria and the rod-shaped PBP from the cyanobacterium Acaryochloris marina). Excitation energy transfer (EET) from QDs to PBP rods was found to take place with varying and highly temperature-dependent efficiencies of up to 90%. Experiments performed at room temperature on hybrid systems with different QDs show that no straightforward correlation exists between the efficiency of EET and the parameter J/(R(12)(6)) given by the theory of Förster resonance energy transfer (FRET), where J is the overlap integral of the normalized QD emission and PBP absorption and R(12) the distance between the transition dipole moments of donor and acceptor. The results show that the hybrid systems cannot be described as randomly orientated aggregates consisting of QDs and photosynthetic pigment-protein complexes. Specific structural parameters are inferred to play an essential role. The mode of binding and coupling seems to change with the size of QDs and with temperature. Efficient EET and fluorescence enhancement of the acceptor was observed at particular stoichiometric ratios between QDs and trimeric phycoerythrin (PE). At higher concentrations of PE, a quenching of its fluorescence is observed in the presence of QDs. This effect is explained by the existence of additional quenching channels in aggregates formed within hybrid systems. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.Biochimica et Biophysica Acta 04/2012; 1817(8):1461-70. DOI:10.1016/j.bbabio.2012.03.030 · 4.66 Impact Factor
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- "Fluorescence-activated cell sorting (FACS), the most popular application of flow cytometry, requires damage-free staining or labeling of cells to permit further processing after the initial sort. Förster resonance energy transfer (FRET)-based sensing might be capable of supplying more-dynamic information regarding biological processes   in comparison with standard fluorescent staining or labeling, but a robust pair of fluorescent molecules (a donor and an acceptor) is required. Fluorescence-lifetime imaging (FLIM), which is based on related principles, has also been developed for imaging of living cells . "
ABSTRACT: Sensing systems based on Förster resonance energy transfer (FRET) can be used to monitor enzymatic reactions, protein-protein interactions, changes in conformation, and Ca2+ oscillations in studies on cellular dynamics. We developed a series of FRET-based chimeric bioprobes, each consisting of fluorescent protein attached to a fluorescent dye. Green and red fluorescent proteins were used as donors and a series of Alexa Fluor dyes was used as acceptors. The basic fluorescent proteins were substituted with appropriate amino acids for recognition of the target (caspase-3) and subjected to site-directed modification with a fluorescent dye. Variants that retained similar emission profiles to the parent proteins were readily derived for use as FRET-based bioprobes with various fluorescent patterns by incorporating various fluorescent proteins and dyes, the nature of which could be adjusted to experimental requirements. All the constructs prepared functioned as bioprobes for quantitative measurement of caspase-3 activity in vitro. Introduction of the bioprobes into cells was so simple and efficient that activation of caspase-3 upon apoptosis could be monitored by means of cytometric analysis. FRET-based bioprobes are valuable tool for high-throughput flow-cytometric analysis of many cellular events when used in conjunction with other fluorescent labels or markers. Statistical dynamic studies on living cells could provide indications of paracrine signaling.Biochimica et Biophysica Acta 07/2011; 1823(2):215-26. DOI:10.1016/j.bbamcr.2011.07.006 · 4.66 Impact Factor
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- "Recently semiconductor nanocrystals with specific optical properties were developed that can be coupled with functional units isolated from biological organisms in establishing hybrid systems for different applications (for a review, see ). Among the various types of hybrid system design the coupling between quantum dots (QDs) and pigmentprotein complexes is of special interest in aiming at constructing systems for photovoltaics where QDs act as efficient light harvesting units. "
ABSTRACT: Hybrid systems were self-assembled in solution from surface treated CdSe/ZnS quantum dots (QDs) and isolated phycobiliprotein (PBP) complexes from the cyanobacterium Acaryochloris marina. The excitation energy transfer (EET) from the QDs to attached PBPs was analyzed by time correlated single photon counting and time integrated fluorescence measurements at different temperatures. It was found:(1)The green emission of the QDs (3.3 nm diameter of the CdSe core) in solution at 530 nm becomes strongly quenched after addition of PBPs.(2)The functional connection between QDs and PBPs via EET interrupts at temperatures below 273 K (0 °C)(3)This temperature dependent effect is fully reversible(4)EET from QDs to PBPs occurs with a time constant of about 140 ps and an efficiency of 85–90% for coupled QDs/PBP hybrid complexes.A model of the EET steps is presented which is based on data evaluation of the time integrated fluorescence emission and the time resolved measurement results via decay associated emission spectra (DAS). According to the theory of Förster Resonance Energy Tranfer (FRET) the average distance between the center of the QDs and the nearest neighbouring chromophore is estimated to be 3.2 nm.Photonics and Nanostructures - Fundamentals and Applications 04/2011; 9(2):190-195. DOI:10.1016/j.photonics.2010.07.004 · 1.79 Impact Factor