1,720,997 research outputs found
Efficient Escape from Endosomes Determines the Superior Efficiency of Multicomponent Lipoplexes
No full textDesigner multicomponent lipoplexes have recently emerged as especially promising transfection candidates, since they are from 10 to 100 times more efficient than binary complexes usually employed for gene delivery purposes. Here, we show, for the first time, that after internalization binary complexes of lower transfection potency remain in compact perinuclear endosomes, while multicomponent systems have intrinsic endosomal rupture properties that allow plasmid DNA to escape from endosomes with extremely high efficiency. Endosomal rupture results in an extraordinarily homogeneous distribution of unbound plasmid DNA throughout the cytoplasm and in the nucleus
Image Mean Square Displacement analysis: a new method to study protein diffusion in cell membranes
No full textThe image mean square displacement..
Intracellular pH measurements made simple by fluorescent protein probes and the phasor approach to fluorescence lifetime imaging
No full textA versatile pH-dependent fluorescent protein was applied to intracellular pH measurements by means of the phasor approach to fluorescence lifetime imaging. By this fit-less method we obtain intracellular pH maps under resting or altered physiological conditions by single-photon confocal or two-photon microscopy. RI Bizzarri, Ranieri/H-1779-201
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Determination of particle number and brightness using a laser scanning confocal microscope operating in the analog mode
Full text linkWe describe a method to obtain the brightness and number of molecules at each pixel of an image stack obtained with a laser scanning microscope. The method is based on intensity fluctuations due to the diffusion of molecules in a pixel. For a detector operating in the analog mode, the variance must be proportional to the intensity. Once this constant has been calibrated, we use the ratio between the variance and the intensity to derive the particle brightness. Then, from the ratio of the intensity to the brightness we obtain the average number of particles in the pixel. We show that the method works with molecules in solution and that the results are comparable to those obtained with fluctuation correlation spectroscopy. We compare the results obtained with the detector operating in the analog and photon counting mode. Although the dynamic range of the detector operating in the photon counting mode is superior, the performance of the analog detector is acceptable under common experimental conditions. Since most commercial laser scanning microscopes operate in the analog mode, the calculation of brightness and number of particles can be applied to data obtained with these instruments, provided that the variance is proportional to the intensity. We demonstrate that the recovered brightness of mEGFP, independent of concentration, is similar whether measured in solution or in two different cell types. Furthermore, we distinguish between mobile and immobile components, and introduce a method to correct for slow variations in intensity
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Oligomerization of Concanavalin A in live cells detected by fluctuation analysis.
Full text linkGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
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