Electron multiplying CCD based detection for spatially resolved fluorescence correlation spectroscopy

Technische Universität Dresden, Dresden, Saxony, Germany
Optics Express (Impact Factor: 3.53). 07/2006; 14(12):5013-20. DOI: 10.1364/OE.14.005013
Source: PubMed

ABSTRACT Fluorescence correlation spectroscopy (FCS) is carried out with an electron multiplying CCD (EMCCD). This new strategy is compared to standard detection by an avalanche photo diode showing good agreement with respect to the resulting autocorrelation curves. Applying different readout modes, a time resolution of 20 micros can be achieved, which is sufficient to resolve the diffusion of free dye in solution. The advantages of implementing EMCCD cameras in wide-field ultra low light imaging, as well as in multi-spot confocal laser scanning microscopy, can consequently also be exploited for spatially resolved FCS. First proof-of-principle FCS measurements with two excitation volumes demonstrate the advantage of the flexible CCD area detection.

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    ABSTRACT: Fluorescence correlation spectroscopy (FCS) is used to study the movements and the interactions of biomolecules at extremely dilute concentrations, yielding results with good spatial and temporal resolutions. Using a number of technical developments, FCS has become a versatile technique that can be used to study a variety of sample types and can be advantageously combined with other methods. Unlike other fluorescence-based techniques, the analysis of FCS data is not based on the average intensity of the fluorescence emission but examines the minute intensity fluctuations caused by spontaneous deviations from the mean at thermal equilibrium. These fluctuations can result from variations in local concentrations owing to molecular mobility or from characteristic intermolecular or intramolecular reactions of fluorescently labeled biomolecules present at low concentrations. Here, we provide a basic introduction to FCS, including its technical development and theoretical basis, experimental setup of an FCS system, adjustment of a setup, data acquisition, and analysis of FCS measurements. Finally, the application of FCS to the study of lipid bilayer membranes and to living cells is discussed.
    Cold Spring Harbor Protocols 07/2014; 2014(7):pdb.top081802. DOI:10.1101/pdb.top081802 · 4.63 Impact Factor
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    01/2012: pages 210-245; Oxford: Academic Press.
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    ABSTRACT: The development of techniques to probe interfacial molecular transport is important for understanding and optimizing surface-based analytical methods including surface-enhanced spectroscopies, biological assays and chemical separations. Single-molecule-fluorescence imaging and tracking has been used to measure lateral diffusion rates of fluorescent molecules at surfaces, but the technique is limited to the study of slower diffusion, where molecules must remain relatively stationary during acquisition of an image in order to build up sufficient intensity in a spot to detect and localize the molecule. While faster time resolution can be achieved by fluorescence-correlation spectroscopy (FCS), where intensity fluctuations in a small spot are related to the motions of molecules on the surface, long-lived adsorption events arising from surface inhomogeneity can overwhelm the correlation measurement and mask the surface diffusion of the moving population. Here, we exploit a combination of these two techniques, imaging-FCS, for measurement of fast interfacial transport at a model chromatographic surface. This is accomp¬lished by rapid imaging of the surface using an electron-multiplied-charged-coupled-device (CCD) camera, while limiting the acquisition to a small area on the camera to allow fast framing rates. The total intensity from the sampled region is autocorrelated to determine surface diffusion rates of molecules with millisecond time resolution. The technique allows electronic control over the acquisition region, which can be used to avoid strong adsorption sites and thus minimize their contribution to the measured autocorrelation decay and to vary the acquisition area to resolve surface diffusion from adsorption and desorption kinetics. As proof of concept, imaging-FCS was used to measure surface diffusion rates, interfacial populations, and adsorption-desorption rates of 1,1'-dioctadecyl-3,3,3'3'-tetramethylindo¬carbo-cyanine (DiI) on planar C18- and C1-modified surfaces.
    Analytical Chemistry 06/2014; 86(15). DOI:10.1021/ac5014354 · 5.83 Impact Factor

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