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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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  • Practical Guide for Excellent GSDIM Super-Resolution Images

    Do you know that most protists and bacteria lack in one feature that each of our body cell has? Our cells are touch and communicate with one another. They send and receive a variety of signals that coordinate their behavior to act together as a functional multicellular organism. Exploring the way of cellular communication and the ways how the cell surface interacts to organize tissues and body structures is of great interest. Kees Jalink and his team of scientists at the Netherlands Cancer Institute (NKI) in Amsterdam obtained new scientific insights into the molecular architecture of hemidesmosomes, cytoskeletal components, cell surface receptors and vesicular proteins with the help of Ground-State-Depletion (GSD)/ dSTORM microscopy. In this interview, Kees Jalink comments on their developments in imaging chambers, buffer conditions and image analysis to get the perfect super resolution image.
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  • Translation Microscopy (TRAM) for Super-Resolution Imaging

    Super-resolution microscopy is transforming our understanding of biology but accessibility is limited by its technical complexity, high costs and the requirement for bespoke sample preparation. We present a novel, simple and multi-color super-resolution microscopy technique, called translation microscopy (TRAM), in which a super-resolution image is restored from multiple diffraction-limited resolution observations using a conventional microscope whilst translating the sample in the image plane.
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  • Individual Macromolecule Motion in a Crowded Living Cell

    There is solid evidence for analyzing fluorescence correlation and dual color fluorescence crosscorrelation spectroscopy data ( FCS and dual color FCCS) in cellular applications by equations based on anomalous subdiffusion. Using equations based on normal diffusion causes artifacts of the fitted biological system response parameters and of the interpretations of the FCS and dual color FCCS data in the crowded environment of living cells. Equations based on normal diffusion are not valid in living cells. The original article embraces the status of the experimental situation and touches obstacles that still hinder the applications of single molecules in the cellular environment.
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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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  • You May Not Know Theodor Förster but You Know His Work: FRET

    If you think FRET stands for Fluorescence Resonance Energy Transfer, you are wrong … in good company but wrong. FRET actually stands for Förster Resonance Energy Transfer. Find out why and more about FRET in this article.
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  • Video Talk by Daniel Axelrod: Total Internal Reflection Fluorescence (TIRF) Microscopy

    Total Internal Reflection Fluorescence (TIRF) Microscopy is a technique that only illuminates dye molecules near a surface. In this video, the pioneer of TIRF Microscopy describes what this technique is used for, explains the principles of the evanescent wave, gives many examples of different microscope configurations used in TIRF, and shows how polarized light TIRF can be used to image membrane orientation.
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  • Towards Digital Photon Counting Cameras for Single-molecule Optical Nanoscopy

    A SPAD array camera with single-photon sensitivity and zero read-out noise allows for the detection of extremely weak signals at ultra-fast imaging speeds. With temporal resolution in the order of micro-seconds, a SPAD array camera offers great potential for live-cell imaging with super-resolution.
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  • Abstracts of the 3rd European Super-Resolution User-Club Meeting

    The 3rd meeting of the Leica Super-Resolution User Club was held from June 17th to 19th, 2013 in collaboration with Alberto Diaspro and the Italian Institute of Technology (IIT) in Genoa. Confocal and widefield super-resolution users from ten European countries took three days’ out to deepen their knowledge on super-resolution techniques and applications and make use of an opportunity for full exchange of experiences.
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  • Detectors for Sensitive Detection: HyD

    This article discusses detectors (more precisely: sensors), that are employed in single point, i.e. true confocal scanning microscopes. The sensors in such systems are usually photomultiplier tubes. Also, the silicon pendants of PMTs are used for particular applications, especially single-molecule measurements. A new development has led to chimeric devices called hybrid detector (HyD) which unite benefits of both technologies.
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  • Abstracts of the 2nd European Super-Resolution User-Club Meeting

    The 2nd meeting of the Leica Super-resolution User club was held from September 25 to 27, 2012 in collaboration with the Science for Life Laboratory at the Karolinska Institute, Stockholm, Sweden. With a mixture of engaging talks by key experts in the field of super-resolution microscopy and stimulating discussion sessions, the meeting proved as popular as last year’s event, attracting a wide range of scientists interested in both confocal and widefield super-resolution and sample preparation techniques.
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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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  • Fluorescence Correlation Spectroscopy

    Fluorescence correlation spectroscopy ( FCS ) measures fluctuations of fluorescence intensity in a sub-femtolitre volume to detect such parameters as the diffusion time, number of molecules or dark states of fluorescently labeled molecules. The technique was independently developed by Watt Webb and Rudolf Rigler during the early 1970s.
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  • Widefield Super-Resolution with GSDIM

    Great advancements in biology have been possible by using fluorescence microscopy. So far, the resolution of the images was limited due to physical constraints. In the past couple of years, new methods evolved circumventing these limitations and bringing fluorescence microscopy to a new level of resolution, boosting the possibilities in science with fluorescence microscopes.
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  • Total Internal Reflection Fluorescence (TIRF) Microscopy

    Total internal reflection fluorescence (TIRF) is a special technique in fluorescence microscopy developed by Daniel Axelrod at the University of Michigan, Ann Arbor in the early 1980s. TIRF microscopy delivers images with an outstandingly high axial resolution below 100 nm. This allows the observation of membrane-associated processes.
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  • Applications of TIRF Microscopy in Life Science Research

    The special feature of TIRF microscopy is the employment of an evanescent field for fluorophore excitation. Unlike standard widefield fluorescence illumination procedures with arc lamps, LEDs or lasers, the evanescent field only penetrates the specimen by about 100 nm starting from the coverslip/medium interface.
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  • Förster Resonance Energy Transfer (FRET)

    The Förster Resonance Energy Transfer (FRET) phenomenon offers techniques that allow studies of interactions in dimensions below the optical resolution limit. FRET describes the transfer of the energy from an excited state of a donor molecule to an acceptor molecule. Unlike absorption or emission of photons, FRET is a non-radiative energy exchange and consequently not a variation of light-matter interactions.
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  • How Widefield Super-Resolution GSDIM Images are Created

    The localization microscopy technique GSDIM is a proven technology to achieve super-resolution images with a resolution of up to 20 nm. In the following tutorial we will describe the basic principles and features of GSDIM.
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  • Step by Step Guide to the Molecular Basics of GSDIM Microscopy

    Ground state depletion microscopy followed by individual molecule return (GSDIM) is a super-resolution technique based on single molecule localization (Localization Microscopy). To localize single molecules and create a high resolution image the ensemble of overlapping fluorophores (in a diffraction-limited setup) has to be broken up. Individual fluorophores must be temporally "separated" to allow high precision detection of single molecules. This tutorial will explain the molecular basics of GSDIM.
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  • A Guide to Super-Resolution Fluorescence Microscopy

    For centuries, cell biology has been based on light microscopy and at the same time been limited by its optical resolution. However, several new technologies have been developed recently that bypass this limit.
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