1,721,061 research outputs found
Cardiolipin effects on the gating behaviour and reconstitution of MscL and MscS
No full textThe mechanosensitive channels of large (MscL) and small (MscS) conductance act as osmosensors in bacterial cells against hypo-osmotic shock. MscL has been extensively studied by reconstitution into liposomes, however MscS has proved more difficult to reconstitute, requiring high protein-lipid ratios. We recently published an improved reconstitution method for both MscL and MscS in soy azolectin, a mixture that contains lipids, sugars and sterols. We have expanded these results and show here the effect of both individual and mixtures of lipids on the reconstitution and channel gating behaviour of co-reconstituted MscL and MscS
Neuartige Optobiomechatronik-Systemtechnologien in Kardio- und Skelettmuskelumgebung von Medizin- und Lebenswissenschaften
No full textThe mechanical properties of their environment and mechanical stimuli from their surroundings are essential factors for the development and behaviour of biological organisms. However, a lot of the aspects of the mechanical interactions of organisms are little understood due to the complexity of applying mechanical stimuli to or detecting mechanical stimuli from organisms on a cellular level in conjunction with detailed observation of the resulting reactions. Three devices were developed and manufactured in the course of this thesis, each of which is able to interact mechanically with biological samples in different modalities while maintaining optical access to the samples in order to record high-resolution microscopy images, documenting the sample response to mechanical stimuli. A number of software solutions were developed to accompany the devices, ranging from graphical user interfaces for device control to 3D image analysis tools. The systems were applied to biomedical research projects together with collaborators in the respective fields, which contributed to the refinement of the system hard- and software according to the specific needs of the investigation. The MechaMorph system is specialised in 1D linear mechanical interaction and was used to show that mechanical load alters the sub-cellular structure of dystrophic skeletal muscle fibres more than that of healthy skeletal muscle fibres. The IsoStretcher provides a means for planar isotropic mechanostimulation in 2D and could show that calcium waves could be induced in cardiac myocytes by a stimulus of quick release of planar strain. The PiezoGRIN system was designed to compress samples isotropically in 3D via high hydrostatic pressure. The changes in sub-cellular morphology parameters of skeletal muscle tissue could be tracked during pressure-induced contracture with the help of the system, indicating that the calcium concentration in the sample immersion solution might alter the contracture behaviour. All three systems were designed with cost efficiency and simplicity in mind, to provide easily reproducible, reliable and adaptable platforms for defined mechanical interaction with biological samples and the option for high-resolution optical observation to the mechanobiology community
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
Patch clamp characterization of the effect of cardiolipin on MscS of E-coli
No full textThe bacterial mechanosensitive channels MscS and MscL are gated by an increase in membrane tension when the bacterium experiences hypoosmotic shock. It has been well established that membrane lipids modulate the mechanosensitivity and gating behavior of these channels. The focus of this study is a negatively charged phospholipid, cardiolipin, which has been shown to localize at curved regions of the bacterial cell, including the poles and the septum, and to have a strong preference for binding to membrane proteins. Here we characterize the effect of cardiolipin on MscS, the mechanosensitive channel of small conductance, using patch-clamp electrophysiology. We compare the gating kinetics and mechanosensitivity of the channel in both azolectin and mixtures of pure lipids DOPE/DOPC liposomes with and without cardiolipin. In azolectin liposomes, the addition of 10 % cardiolipin abolishes hysteresis of MscS, but MscL remains largely unaffected, indicating that cardiolipin may stabilize the closed state of MscS. On the other hand, mixtures of DOPE/DOPC abolish the hysteresis gating of MscS even in the absence of cardiolipin, and the addition of cardiolipin increases the opening and closing thresholds of both MscS and MscL. In addition, we show that MscS gates more frequently when cardiolipin is present in both the azolectin and pure lipid systems; this dose-dependent effect ultimately destabilizes the open state of MscS and we consider the functional implications of this cardiolipin effect in the bacterial osmotic response. Our results show that cardiolipin modulates the mechanosensitivity and gating characteristics of MscS, indicating its important role in the physiology of bacterial cells
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
Systematic discovery of the ‘force-from-lipid’ principles
No full textThe functioning of bacterial mechanosensitive channels is governed by the lipid environment in which they are embedded. Several physical parameters such as lipid charge, saturation and topography, work in concert during transmission of tension from the bilayer onto the ion channel, thus making it a difficult task to dissect the contribution of each parameter to the channel's mechanosensitivity
A High-Throughput Technique for Screening Novel Antibacterial Agents Targeting Bacterial Mechanosensitive Channels
No full textMechanosensitive Ion channels are essential for maintaining cellular homeostasis. It has been proposed that they function as osmotically activated emergency valves, guarding against membrane rupture by opening pores to release excessive turgor pressure. Interfering with their function suggests many novel mechanisms to complement conventional antimicrobials to kill or inhibit growth of bacterial pathogens. Typical of this class of mechanosensitive channel are the large conduction homopentameric bacterial channel, MscL (MW∼17kDa) and the small conduction homoheptameric bacterial channel, MscS (∼37kDa)
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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