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  • Testing the Münch Hypothesis of Long Distance Phloem Transport in Plants

    Long distance transport in plants occurs in sieve tubes of the phloem. The pressure flow hypothesis introduced by Ernst Münch in 1930 describes a mechanism of osmotically generated pressure differentials that are supposed to drive the movement of sugars and other solutes in the phloem, but this hypothesis has long faced major challenges. The key issue is whether the conductance of sieve tubes, including sieve plate pores, is sufficient to allow pressure flow. We show that with increasing distance between source and sink, sieve tube conductivity and turgor increases dramatically in Ipomoea nil. Our results provide strong support for the Münch hypothesis, while providing new tools for the investigation of one of the least understood plant tissues.
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  • "The Leica Digital Light Sheet Module – a Clever Example of Thinking Out of the Box"

    Bram van den Broek is a postdoctoral fellow at the Netherlands cancer institute in Amsterdam where he supports the advanced microscopy techniques in the laboratory of Kees Jalink. Working with Leica Microsystems as a collaboration partner for beta-testing of microscopes he enjoys very much.
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  • How to Measure FRET

    Here, I will expand, including what to measure when doing FRET. There are a number of approaches to FRET quantification: 1. Sensitized Emission – This two-channel imaging technique uses an algorithm that corrects for excitation and emission crosstalk.
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  • Multiple Microscopy Modes in a Single Sweep with Supercontinuum White Light

    Lasers have been critical to the advancement on confocal microscopy, and the white light laser (WLL) offers particular advantages. Finessing WLL output for bioimaging is a complex task, though, and traditional approaches retain key limitations. But acousto-optical beamsplitting enables smoother operation, leading to enhanced microscopy capabilities.
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  • Label-free FLIM

    Many biological samples exhibit autofluorescence. Its often broad spectra can interfere with fluorescent labeling strategies. This application letter demonstrates how autofluorescence can serve as an intrinsic contrast in fluorescence lifetime imaging microscopy (FLIM) resulting in multi-color image stacks.
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  • FRET with FLIM

    FLIM combines lifetime measurements with imaging: lifetimes obtained for each image pixel are color-coded to produce additional image contrast. Thus, FLIM delivers information about the spatial distribution of a fluorescent molecule together with information about its biochemical status or nano-environment. A typical application of FLIM is FLIM-FRET. FRET is a well-established technique to study molecular interactions. It scrutinizes protein binding and estimates intermolecular distances on an Angström scale as well.
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  • Quantitative Fluorescence

    Seeing is believing – and measuring is knowing. Microscopes generate images that are not only used for illustration, but are also subject to quantification. More advanced techniques use illumination patterns (without image formation) or do not generate an image at all – but are still microscopical techniques. These F-techniques are becoming increasingly important in current biosciences.
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  • Live-cell Imaging Techniques

    The understanding of complex and/or fast cellular dynamics is an important step for exploring biological processes. Therefore, today’s life science research is increasingly focusing on dynamic processes like cell migration, morphological changes of cells, organs or whole animals and physiological (e.g. changes of intracellular ion composition) events in living specimens in real time.
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  • FLIM-FRET in Solutions

    FRET efficiency can be measured based on fluorescence lifetime microscopy (FLIM). FLIM-FRET allows analysis of molecular interactions both in vitro and in vivo. This article describes the use of FLIM in the time domain (TCSPC) to measure FRET in vitro in a biochemical assay using a Cerulean-Citrine construct.
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  • A mTurquoise-Based cAMP Sensor for Both FLIM and Ratiometric Read-Out Has Improved Dynamic Range

    FRET-based sensors for cyclic Adenosine Mono Phosphate (cAMP) have revolutionized the way in which this important intracellular messenger is studied. The currently prevailing sensors consist of the cAMP-binding protein Epac1, sandwiched between suitable donor- and acceptor fluorescent proteins (FPs).
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  • Choose Your Excitation Wavelength

    Although time correlated single photon counting (TCSPC) is the method of choice for fluorescence lifetime quantification, it requires dedicated instrumentation including a pulsed laser source, a photon counting card, and a fast detector.
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  • ATP Changes the Fluorescence Lifetime of Cyan Fluorescent Protein via an Interaction with His148

    Recently, we described that ATP induces changes in YFP/CFP fluorescence intensities of Fluorescence Resonance Energy Transfer (FRET) sensors based on CFP-YFP. To get insight into this phenomenon, we employed fluorescence lifetime spectroscopy to analyze the influence of ATP on these fluorescent proteins in more detail. Using different donor and acceptor pairs we found that ATP only affected the CFP-YFP based versions.
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