1,720,960 research outputs found
A mid-infrared laser microscope for the time-resolved study of light-induced protein conformational changes
No full textWe have developed a confocal laser microscope operating in the mid-infrared range for the study of light-sensitive proteins, such as rhodopsins. The microscope features a co-aligned infrared and visible illumination path for the selective excitation and probing of proteins located in the IR focus only. An external-cavity tunable quantum cascade laser provides a wavelength tuning range (5.80-6.35 mu m or 1570-1724 cm(-1)) suitable for studying protein conformational changes as a function of time delay after visible light excitation with a pulsed LED. Using cryogen-free detectors, the relative changes in the infrared absorption of rhodopsin thin films around 10(-4) have been observed with a time resolution down to 30 ms. The measured full-width at half maximum of the Airy disk at lambda= 6.08 mu m in transmission mode with a confocal arrangement of apertures is 6.6 mu m or 1.1.. Dark-adapted sample replacement at the beginning of each photocycle is then enabled by exchanging the illuminated thin-film location with the microscope mapping stage synchronized to data acquisition and LED excitation and by averaging hundreds of time traces acquired in different nearby locations within a homogeneous film area. We demonstrate that this instrument provides crucial advantages for time-resolved IR studies of rhodopsin thin films with a slow photocycle. Time-resolved studies of inhomogeneous samples may also be possible with the presented instrument
Infrared Nanospectroscopy and Terahertz Irradiation of Pathological Protein Aggregates
No full textα-Synuclein (αS) is of wide interest because its aggregation is a hallmark of many neurodegenerative disorders, including Parkinson’s disease. Here, we are using the atomic force microscopy-assisted infrared nanospectroscopy to investigate its aggregation into nanoscale fibrils and describe the secondary structure change of the protein during aggregation. Perspective THz irradiation experiments have been designed and are being set up, with the aim of modifying the secondary structure of proteins and/or aggregates through prolonged THz irradiation with CW sources
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
Conformational changes of an oriented film of photosensitive proteins observed by polarized ATR infrared spectroscopy
No full textWe apply polarized Attenuated Total Reflection Fourier Transform Infrared spectroscopy (ATR-FTIR) to study conformational changes of the prototype photosensitive protein bacteriorhodopsin (BR). The experiments are performed on hundreds-nanometer-thick films of stacked membrane patches embedding BR molecules. Moreover, we report our results on functionalization of silicon surfaces that are preliminary to further experiments involving faced-down silicon substrates on ATR crystal in order to increase the sensitivity down to very thin protein films
Mid-Infrared nanospectroscopy to probe protein conformation at the nanoscale
No full textPhotothermal atomic force microscopy-assisted infrared nanospectroscopy is applied to investigate protein conformation at the nanoscale. In the framework of protein aggregation, the possibility to probe protein conformation on nanometr-sized structures, enabled us to identify structural differences among fibrils formed under different conditions. By adopting a difference IR nanospectroscopy approach (visible light ON-visible light OFF), we then probed, for the first time, subtle transient conformational changes of light-sensitive protein receptors embedded in individual native cell membrane patches
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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