1,720,959 research outputs found
Parallelized STED fluorescence nanoscopy.
No full textWe introduce a parallelized STED microscope featuring m = 4 pairs of scanning excitation and STED beams, providing m-fold increased imaging speed of a given sample area, while maintaining basically all of the advantages of single beam scanning. Requiring only a single laser source and fiber input, the setup is inherently aligned both spatially and temporally. Given enough laser power, the design is readily scalable to higher degrees of parallelization m
Fluoreszenznanoskopie einzelner DNA-Moleküle mit Fluoreszenzverhinderung durch stimulierte Emission (STED)
No full textScharfe Aufnahmen: STED-Nanoskopie (STED=stimulierte Fluoreszenzverhinderung) von einzelnen DNA-Strängen visualisiert Strukturen mit einer 5- bis 6fach höheren Auflösung als konfokale Mikroskopie (Konf), wie aus dem linken bzw. rechten Bild ersichtlich ist. Die STED-Technik enthüllt Strukturen der Größenordnung der DNA-Persistenzlänge (ca. 50 nm), ohne dabei in maßgeblicher Weise Photoschäden wie Bleichen oder DNA-Bruch zu verursachen
Parallelised STED nanoscopy
No full textOptische Nanoskopie hat sich als wertvolles Instrument für die Molekularbiologeentwickelt. Diese Methoden sind nicht mehr durch die Beugung des Lichtes begrenzt und führen zu neuen Herausforderungen. Das dafür erforderliche Schalten des molekularen Signals macht eine zeitlich sequentielle Signalaufnahme erforderlich und führt zu längeren Aufnahmezeiten mit steigender Auflösung. Um die Gesamtaufnahmezeit des Bildfeldes zu reduzieren und damit die Attraktivität der hochauflösenden optischen Methoden für die Biologie zu erhöhen ist eine Parallelisierung des Bildfeldes essenziell. Diese Arbeit befasst sich mit den fundamentalen Grenzen der parallelisierten Nanoskopie und beinhaltet die erste experimentelle Ausführung von parallelisierter Koordinaten-definierter Nanoskopie mit Fluoreszenzverhinderung durch stimulierte Emission (STED). Eine verlustfreie vierfache Parallelisierung wird durch polarisierende Strahlteiler und ein chromatisches segmentiertes Wellenplättchen, welches als formgestaltendes Element fungiert, ermöglicht. Eine gemeinsame Faserlichtquelle gewährleistet dass alle Laserstrahlen sowohl räumlich als auch zeitlich überlagert sind. Die zeitreduzierende Eigenschaft von Parallelisierung wurde nachgewiesen. Diese Arbeit führt außerdem eine neue Detektionsmethode in die Nanoskopie ein, welche die koinzidenten Photonen pro Laserzyklus detektiert.Der Effekt des Photonenantibunching von fluoreszenten Molekülen ermöglichtes die Anzahl von gleichzeitig angeregten Molekülen aus der Photonenstatistikheraus zu bestimmen. Dies erlaubt es Koordinaten-definierten Nanoskopiemethoden, wie STED, die Anzahl der fluoreszenten Molekülenim Fokus zu zählen
Maturation-Dependent HIV-1 Surface Protein Redistribution Revealed by Fluorescence Nanoscopy
No full textHuman immunodeficiency virus type 1 (HIV-1) buds from the cell as an immature particle requiring subsequent proteolysis of the main structural polyprotein Gag for morphological maturation and infectivity. Visualization of the viral envelope (Env) glycoprotein distribution on the surface of individual HIV-1 particles with stimulated emission depletion (STED) superresolution fluorescence microscopy revealed maturation-induced clustering of Env proteins that depended on the Gag-interacting Env tail. Correlation of Env surface clustering with the viral entry efficiency revealed coupling between the viral interior and exterior: Rearrangements of the inner protein lattice facilitated the alteration of the virus surface in preparation for productive entry. We propose that Gag proteolysis-dependent clustering of the sparse Env trimers on the viral surface may be an essential aspect of HIV-1 maturation
Fluorescence nanoscopy of single DNA molecules by using stimulated emission depletion (STED).
Get PDFClearing the haze: Stimulated emission depletion (STED) nanoscopy on single DNA strands reveals details with an up to five- to sixfold improved resolution over confocal microscopy (see images). Thus STED nanoscopy allows features to be distinguished down to the persistence length of DNA (ca. 50 nm) without promoting any significant additional photodamage, such as photobleaching or photonicking
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Tissue multicolor STED nanoscopy of presynaptic proteins in the calyx of held
Get PDFThe calyx of Held, a large glutamatergic terminal in the mammalian auditory brainstem has been extensively employed to study presynaptic structure and function in the central nervous system. Nevertheless, the nanoarchitecture of presynaptic proteins and subcellular components in the calyx terminal and its relation to functional properties of synaptic transmission is only poorly understood. Here, we use stimulated emission depletion (STED) nanoscopy of calyces in thin sections of aldehyde-fixed rat brain tissue to visualize immuno-labeled synaptic proteins including VGluT1, synaptophysin, Rab3A and synapsin with a lateral resolution of approximately 40 nm. Excitation multiplexing of suitable fluorescent dyes deciphered the spatial arrangement of the presynaptic phospho-protein synapsin relative to synaptic vesicles labeled with anti-VGluT1. Both predominantly occupied the same focal volume, yet may exist in exclusive domains containing either VGluT1 or synapsin immunoreactivity. While the latter have been observed with diffraction-limited fluorescence microscopy, STED microscopy for the first time revealed VGluT1-positive domains lacking synapsins. This observation supports the hypothesis that molecularly and structurally distinct synaptic vesicle pools operate in presynaptic nerve terminals
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