Search results for "apparatus"
showing 10 items of 192 documents
Goodpasture Antigen-binding Protein Is a Soluble Exportable Protein That Interacts with Type IV Collagen
2008
Goodpasture-antigen binding protein (GPBP) is a nonconventional Ser/Thr kinase for basement membrane type IV collagen. Various studies have questioned these findings and proposed that GPBP serves as transporter of ceramide between the endoplasmic reticulum and the Golgi apparatus. Here we show that cells expressed at least two GPBP isoforms resulting from canonical (77-kDa) and noncanonical (91-kDa) mRNA translation initiation. The 77-kDa polypeptide interacted with type IV collagen and localized as a soluble form in the extracellular compartment. The 91-kDa polypeptide and its derived 120-kDa polypeptide associated with cellular membranes and regulated the extracellular levels of the 77-kD…
Role of hydrophobic forces in bilayer adhesion and fusion.
1992
With the aim of gaining more insight into the forces and molecular mechanisms associated with bilayer adhesion and fusion, the surface forces apparatus (SFA) was used for measuring the forces and deformations of interacting supported lipid bilayers. Concerning adhesion, we find that the adhesion between two bilayers can be progressively increased by up to two orders of magnitude if they are stressed to expose more hydrophobic groups. Concerning fusion, we find that the most important force leading to direct fusion is the hydrophobic attraction acting between the (exposed) hydrophobic interiors of bilayers; however, the occurrence of fusion is not simply related to the strength of the attrac…
Role of calcium in the adhesion and fusion of bilayers.
1993
The interaction forces and fusion mechanisms of mixed zwitterionic-anionic phospholipid bilayers were measured with the surface forces apparatus. The bilayers were 3:1 mixtures of either dimyristoylphosphatidylcholine and dimyristoylphosphatidylglycerol (DMPC/DMPG) or dilauroylphosphatidylcholine and dilauroylphosphatidylglycerol (DLPC/DLPG), and experiments were carried out in NaCl solutions with and without CaCl2. In NaCl solutions, the forces between either mixed bilayer system were consistent with the DLVO (Derjaguin-Landau-Verwey-Overbeek) theory of repulsive electrostatic and attractive van der Waals forces, and fusion did not occur. At high pH (> 6) and in high (20 mM) NaCl concentra…
Adhesion and adhesion hysteresis of mica surfaces covered with bola-amphipiles in dry and humid air
1998
Abstract Bola-amphiphiles with spherical hydrophilic chinuclidinium head groups form laterally ordered monolayers on mica by adsorption from solution. To measure the surface adhesion, JKR-type compression/decompression cycles have been performed with the surface forces apparatus (SFA). In an inert atmosphere, the adhesion energy on increasing the contact area is much lower than predicted by wetting experiments. Furthermore, the pronounced adhesion hysteresis varies from sample to sample in a wide range, indicating a defect-rich surface. On increase of the relative humidity (rh), the reproducibility improves and the values for the adhesion energy measured on compression and decompression con…
Organelle pH studies using targeted avidin and fluorescein–biotin
2000
Abstract Background: Mammalian organelles of the secretory pathway are of differing pH. The pH values form a decreasing gradient: the endoplasmic reticulum (ER) is nearly neutral, the Golgi is mildly acidic and the secretory granules are more acidic still (∼pH 5). The mechanisms that regulate pH in these organelles are still unknown. Results: Using a novel method, we tested whether differences in H + ‘leak' and/or counterion conductances contributed to the pH difference between two secretory pathway organelles. A pH-sensitive, membrane-permeable fluorescein–biotin was targeted to endoplasmic-reticulum- and Golgi-localized avidin-chimera proteins in HeLa cells. In live, intact cells, ER pH (…
Comparison of Nonclassic and Classic Phenotype of Hypertrophic Cardiomyopathy Focused on Prognostic Cardiac Magnetic Resonance Parameters: A Single-C…
2022
Patients with nonclassic phenotypes (NCP)—more advanced stages of hypertrophic cardiomyopathy (HCM)—constitute an intriguing and heterogeneous group that is difficult to diagnose, risk-stratify, and treat, and often neglected in research projects. We aimed to compare cardiac magnetic resonance (CMR) parameters in NCP versus classic phenotypes (CP) of HCM with special emphasis given to the parameters of established and potential prognostic importance, including numerous variables not used in everyday clinical practice. The CMR studies of 88 patients performed from 2011 to 2019 were postprocessed according to the study protocol to obtain standard and non-standard parameters. In NCP, the late …
Portability in analytical chemistry: a green and democratic way for sustainability
2019
International audience; Recent advances in portability of analytical equipment have been considered to enlighten the advantages offered by portable instrumentation on greening the analytical methods. Their use drastically reduces sampling, sample stockage, and transport, thus avoiding environmental side effects and risks, also improving decision-making. The fact that portable instrumentation is, in general, less expensive than bench instruments and apparatuses makes also available the analytical tools for extended sectors of the population, thus making accessible the advantages derived from analytical methods. The role of sensor technology and portable miniaturized systems has been consider…
Modelling thermionic emission by using a two Level mechanical system
2008
The Boltzmann factor is at the basis of a great amount of thermodynamic and statistical physics, both classical and quantum. It describes the behaviour of natural systems that exchange energy with the environment. However, why does the expression have that specific form? The Feynman Lectures on Physics justifies it heuristically by referencing to the "exponential atmosphere" example. Thermodynamics textbooks usually give a more or less complete explanation that mainly involves a mathematical analysis, where it is hard to see the logic flow. Moreover, the necessary mathematics is not at the level of high school or college students' preparation. Here we present an experiment and a simulation …
A closer look at the cholesterol sensor
2002
Abstract Transport of the sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP)–SREBP complex from the endoplasmic reticulum (ER) to the Golgi is the central event mediating the cholesterol-feedback process in mammalian cells. A conformational change in SCAP is a crucial step; when cholesterol levels are high, the conformation of SCAP enables the SCAP–SREBP complex to associate with an insulin-induced gene (INSIG) retention protein in the ER. By contrast, when cholesterol levels are low, SCAP switches to a conformation that enables the dissociation of the retention protein and the association of SCAP–SREBP with COP II vesicles.
Polyphosphoinositide Metabolism and Golgi Complex Morphology in Hippocampal Neurons in Primary Culture is Altered by Chronic Ethanol Exposure
2012
Aims : Ethanol affects not only the cytoskeletal organization and activity, but also intracellular trafficking in neurons in the primary culture. Polyphosphoinositide (PPIn) are essential regulators of many important cell functions, including those mentioned, cytoskeleton integrity and intracellular vesicle trafficking. Since information about the effect of chronic ethanol exposure on PPIn metabolism in neurons is scarce, this study analysed the effect of this treatment on three of these phospholipids. Methods : Phosphatidylinositol (PtdIns) levels as well as the activity and/or levels of enzymes involved in their metabolism were analysed in neurons chronically exposed to ethanol. The level…