1,721,931 research outputs found
Protein dynamics by neutron scattering
No full textNeutron scattering techniques represent a powerful tool for characterizing both the structure and dynamical properties of bio-systems, for example, proteins and membranes interacting with their solvents. In this paper, Elastic Neutron Scattering (ENS) data collected at the Institut Laue-Langevin (Grenoble, France) on dry and D2O hydrated lysozyme by varying hydration level are presented, and compared with previously published data on the same protein system, also with the addition of bio-protectants. The data have been collected with three different spectrometers, i.e. IN13, IN10 and IN4. This set of ENS data gives direct access to the temperature behavior of both (i) theMean Square Displacement (MSD) and (ii) the characteristic systemrelaxation time. As a result, an explicative hypothesis on the relationship between the so-called "protein dynamical transition" (PDT) and the "fragile-to-strong dynamical crossover" (FSC) is formulated. Furthermore, by taking into proper account the effect of the finite instrumental energy resolution of the used spectrometers, the vibrational MSD of dry and hydrated lysozyme is calculated. The vibrationalMSD of the lysozyme in the dry state resulted to be higher than the one in the hydrated state; the latter reaches the former at a temperature value of T = 220 K that corresponds to the temperature at which the FSC occurs. As a result, a cage effect resulting from the hydration water on the protein surface is hypothesized and subsequently linked to the FSC. © 2013 Elsevier B.V. All rights reserved
From protein and its hydration water dynamics to controlling mechano-elasticity of cellular lipid membranes and cell migration via ionic liquids
No full textIn this invited Commentary, as requested, I will walk the reader through my research path starting from my first works on proteins and their hydration water dynamics to my most recent activity on the use of ionic liquids (ILs) as molecular handles to control and manipulate cell membrane mechano-elasticity and cell migration. In doing so I will comment on my research activity on polymers, proteins, natural bioprotectants, phospholipid bilayers, amyloids and cells, which I have carried out by combining several different experimental and computational approaches including neutron scattering, atomic force microscopy, classical molecular dynamics and ab initio calculations, used in tandem with several biological assays and a palette of complementary techniques ranging from calorimetry to static and dynamic light scattering. In parallel to this biophysical/chemical-physical core activity, a smaller portion of my interest and effort has been—I may say always—dedicated to the development of a new neutron scattering method/spectroscopy for dynamics based on “elastic” scattering. I will comment on this instrumental side of my research as well and show its relationship with the biophysical core of my activity. The overall picture that emerges is, from my personal prospective, of a coherent 13-year research path based on curiosity and a problem-solving approach, in which the fundamental importance of inter- and trans-disciplinary approaches and collaborations is emerging on the way, forecasting a prosper and intriguing future for physics in biology and in nanomedicine and bionanotechnology applications
Going 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
Visual sensitivity and bias oscillate phase-locked to saccadic eye movements
Full text linkOscillations in perceptual performance have been observed before and after a voluntary action, like hand, finger, and eye movements. In particular, discrimination accuracy of suprathreshold contrast stimuli oscillates in the delta range (2-3 Hz) phase-locked to saccadic eye movements. Importantly, saccadic suppression is embedded in phase with these long-lasting perceptual oscillations. It is debated whether these rhythmic modulations affect only appearance of high-contrast stimuli or whether absolute detection threshold is also modulated rhythmically. Here we measured location discrimination of a brief Gabor patch presented randomly between 1 s before and after a voluntary saccade and demonstrated that absolute contrast thresholds oscillated at a similar frequency to suprathreshold contrast discrimination. Importantly, saccadic suppression is also embedded in phase with absolute threshold oscillations. Interestingly, response bias was also found to oscillate at the same frequency in both tasks. However, the frequency was in the alpha range for bias, while it was in the delta range for sensitivity. These results demonstrate the presence of perisaccadic delta oscillations in visual sensitivity phase-locked to saccadic onset, and independent from response bias alpha oscillations. Overall, the present findings reinforce the suggestion of a leading role of oscillations in the temporal binding between eye-movement and visual processing timing
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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