scholarly journals Surface Measurement of a Large Inflatable Reflector in Cryogenic Vacuum

Photonics ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 1
Author(s):  
Henry Quach ◽  
Hyukmo Kang ◽  
Siddhartha Sirsi ◽  
Aman Chandra ◽  
Heejoo Choi ◽  
...  
Keyword(s):  
Shape Change ◽  
Pressure Change ◽  
Membrane Properties ◽  
Surface Measurement ◽  
Membrane Structures ◽  
Thermal Vacuum ◽  
Pixel Resolution ◽  
Optical Surfaces ◽  
Cryogenic Vacuum ◽  
Initial Measurement

The metrology of membrane structures, especially inflatable, curved, optical surfaces, remains challenging. Internal pressure, mechanical membrane properties, and circumferential boundary conditions imbue highly dynamic slopes to the final optic surface. Here, we present our method and experimental results for measuring a 1 m inflatable reflector’s shape response to dynamic perturbations in a thermal vacuum chamber. Our method uses phase-measuring deflectometry to track shape change in response to pressure change, thermal gradient, and controlled puncture. We use an initial measurement as a virtual null reference, allowing us to compare 500 mm of measurable aperture of the concave f/2, 1-meter diameter inflatable optic. We built a custom deflectometer that attaches to the TVAC window to make full use of its clear aperture, with kinematic references behind the test article for calibration. Our method produces 500 × 500 pixel resolution 3D surface maps with a repeatability of 150 nm RMS within a cryogenic vacuum environment (T = 140 K, P = 0.11 Pa).

Dibucaine-Induced Modification of Sodium Transport in Toad Skin and of Model Membrane Structures

2001 ◽  
Vol 56 (7-8) ◽  
pp. 614-622 ◽  
Author(s):  
Mario Suwalsky ◽  
Carlos Schneider ◽  
Fernando Villena ◽  
Beryl Norris ◽  
Hernan Cárdenas ◽  
...  
Keyword(s):  
Human Erythrocyte ◽  
Shape Change ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Erythrocyte Membranes ◽  
Membrane Structures ◽  
Toad Skin ◽  
Large Unilamellar Vesicles ◽  
Human Erythrocyte Membranes ◽  
Membrane Models

The interaction of the local anesthetic dibucaine with the isolated toad skin and membrane models is described. The latter consisted of human erythrocytes, isolated unsealed human erythrocyte membranes (IUM), large unilamellar vesicles (LUV) of dimyristoylphosphati-dylcholine (DMPC) and phospholipid multilayers built-up of DMPC and dimyristoylphos-phatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. Results indicate a significant decrease in the potential difference (PD) and in the short-circuit current (Isc) after the application of dibucaine in toad skin, which may be interpreted as reflecting inhibition of the active transport of ions. This finding might be explained on the basis of the results ob­ tained from fluorescence spectroscopy and X-ray diffraction studies on membrane models. In fact, dibucaine induced structural perturbations in IUM, DMPC LUV and phospholipid multilayers. Scanning electron microscopy revealed that dibucaine induced erythrocyte stomatocytosis. According to the bilayer couple hypothesis an echinocytic type of shape change would have been expected given the preferential interaction of dibucaine with DMPC. Although it is still premature to define the molecular mechanism of action of dibucaine, the experimental results confirm the important role played by the phospholipid bilayers in the association of the anesthetic with cell membranes

Platelet Microtubule Subunit Proteins

1977 ◽  
Author(s):  
N. Crawford
Keyword(s):  
Cytochalasin B ◽  
Shape Change ◽  
Polyacrylamide Gel Electrophoresis ◽  
Membrane Properties ◽  
Antithrombotic Drugs ◽  
Essential Components ◽  
High Molecular Weight Proteins ◽  
Sites Of Action ◽  
Brain Tubulin

Microtubule subunit proteins have been isolated and purified from pig platelet homogenates and reassembled in vitro to form structures similar to those seen in the intact platelet. The major subunit protein tubulin has many of the properties of neurotubulin; it is a 6S dimer protein which binds colchicine and can be split into two non-identical monomers [α and β] in discontinuous alkaline SDS Polyacrylamide gel electrophoresis. Present also in the preparation are two/three high molecular weight proteins [8–12% of the total protein] which are similar to those seen in brain tubulin preparations and appear to be essential components in the reassembly process. An antibody has been raised to platelet tubulin and used for the fluorescent visualisation of cell microtubules. Their morphological distribution has been contrasted with that of structures stained with anti-actin antisera and the effect of colchicine, cytochalasin B and low temperatures on the specificity of these antibodies has been investigated. Some views will be presented on the equilibrium which exists in platelets between microtubular subunit proteins and the fully formed microtubules. Because of the possible cytoskeletal importance of the microtubules in shape change phenomena and their role in controlling membrane properties, factors which directionally influence this equilibrium may be important sites of action for antithrombotic drugs.

scholarly journals Anti-Bacterial Properties of Cannabigerol Toward Streptococcus mutans

2021 ◽  
Vol 12 ◽  
Author(s):  
Muna Aqawi ◽  
Ronit Vogt Sionov ◽  
Ruth Gallily ◽  
Michael Friedman ◽  
Doron Steinberg
Keyword(s):  
Electron Microscopy ◽  
Streptococcus Mutans ◽  
Nile Red ◽  
Membrane Properties ◽  
Physiological Adaptation ◽  
Membrane Structures ◽  
Iodide Uptake ◽  
Gram Positive ◽  
Membrane Hyperpolarization ◽  
Acid Tolerant

Streptococcus mutans (S. mutans) is a gram-positive facultatively anaerobic bacterium and the most common pathogen associated with tooth caries. The organism is acid tolerant and can undergo physiological adaptation to function effectively in acid environments such as carious dental plaque. Some cannabinoids have been found to have potent anti-microbial activity against gram-positive bacteria. One of these is the non-psychoactive, minor phytocannabinoid Cannabigerol (CBG). Here we show that CBG exhibits anti-bacterial activities against S. mutans. CBG halts the proliferation of planktonic growing S. mutans, which is affected by the initial cell density. High-resolution scanning electron microscopy showed that the CBG-treated bacteria become swollen with altered membrane structures. Transmission electron microscopy provided data showing that CBG treatment leads to intracellular accumulation of membrane structures. Nile red, DiOC2(3) and laurdan staining demonstrated that CBG alters the membrane properties, induces membrane hyperpolarization, and decreases the membrane fluidity. CBG-treated bacteria showed increased propidium iodide uptake and reduced calcein AM staining, suggesting that CBG increases the membrane permeability and reduces the metabolic activity. Furthermore, CBG prevented the drop in pH caused by the bacteria. In summary, we present here data showing the mechanisms by which CBG exerts its anti-bacterial effect against S. mutans.

scholarly journals Anandamide alters the membrane properties, halts the cell division and prevents drug efflux in multidrug resistant Staphylococcus aureus

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shreya Banerjee ◽  
Ronit Vogt Sionov ◽  
Mark Feldman ◽  
Reem Smoum ◽  
Raphael Mechoulam ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Division ◽  
Nile Red ◽  
Public Health Problem ◽  
Multidrug Resistant ◽  
Membrane Properties ◽  
Drug Efflux ◽  
Membrane Structures ◽  
Bacterial Membranes ◽  
Dose Dependent

AbstractAntibiotic resistance is a serious public health problem throughout the world. Overcoming methicillin and multidrug-resistant Staphylococcus aureus (MRSA/MDRSA) infections has become a challenge and there is an urgent need for new therapeutic approaches. We have previously demonstrated that the endocannabinoid Anandamide (AEA) can sensitize MRSA to antibiotics. Here we have studied the mechanism of action using a MDRSA clinical isolate that are sensitized by AEA to methicillin and norfloxacin. We found that AEA treatment halts the growth of both antibiotic-sensitive and antibiotic-resistant S. aureus. The AEA-treated bacteria become elongated and the membranes become ruffled with many protrusions. AEA treatment also leads to an increase in the percentage of bacteria having a complete septum, suggesting that the cell division is halted at this stage. The latter is supported by cell cycle analysis that shows an accumulation of bacteria in the G2/M phase after AEA treatment. We further observed that AEA causes a dose-dependent membrane depolarization that is partly relieved upon time. Nile red staining of the bacterial membranes indicates that AEA alters the membrane structures. Importantly, 4′-6-diamidino-2-phenylindole (DAPI) accumulation assay and ethidium bromide efflux (EtBr) assay unveiled that AEA leads to a dose-dependent drug accumulation by inhibiting drug efflux. In conclusion, our study demonstrates that AEA interferes with cell division, alters the membrane properties of MDRSA, and leads to increased intracellular drug retention, which can contribute to the sensitization of MDRSA to antibiotics.

scholarly journals Designing 3D Membrane Modules for Gas Separation Based on Hollow Fibers from Poly(4-methyl-1-pentene)

Membranes ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 36
Author(s):  
Svetlana Yu. Markova ◽  
Anton V. Dukhov ◽  
Martin Pelzer ◽  
Maxim G. Shalygin ◽  
Thomas Vad ◽  
...  
Keyword(s):  
Polymeric Membranes ◽  
Membrane Properties ◽  
Membrane Structures ◽  
Shell Side ◽  
Textile Processing ◽  
Separation Processes ◽  
Flow Mixing ◽  
Volatile Organic ◽  
Membrane Modules ◽  
Improve Mass Transfer

Designing hollow fiber (HF) membrane modules occupies one of the key positions in the development of efficient membrane processes for various purposes. In developing HF membrane modules, it is very important to have a uniform HF distribution and flow mixing in the shell side to significantly improve mass transfer and efficiency. This work suggests the application of different textile 3D HF structures (braided hoses and woven tape fabrics). The 3D structures consist of melt-spun, dense HFs based on poly(4-methyl-1-pentene) (PMP). Since the textile processing of HFs can damage the wall of the fiber or close the fiber bore, the membrane properties of the obtained structures are tested with a CO2/CH4 mixture in the temperature range of 0 to 40 °C. It is shown that HFs within the textile structure keep the same transport and separation characteristics compared to initial HFs. The mechanical properties of the PMP-based HFs allow their use in typical textile processes for the production of various membrane structures, even at a larger scale. PMP-based membranes can find application in separation processes, where other polymeric membranes are not stable. For example, they can be used for the separation of hydrocarbons or gas mixtures with volatile organic compounds.

scholarly journals Membrane curvature allosterically regulates the phosphatidylinositol cycle, controlling its rate and acyl-chain composition of its lipid intermediates

2018 ◽  
Vol 293 (46) ◽  
pp. 17780-17791 ◽  
Author(s):  
José Carlos Bozelli ◽  
William Jennings ◽  
Stephanie Black ◽  
Yu Heng Hou ◽  
Darius Lameire ◽  
...  
Keyword(s):  
Physical Properties ◽  
Lipid Composition ◽  
Gaussian Curvature ◽  
Acyl Chain ◽  
Membrane Lipid ◽  
Membrane Curvature ◽  
Membrane Properties ◽  
Membrane Structures ◽  
Membrane Lipid Composition ◽  
Signaling Events

Signaling events at membranes are often mediated by membrane lipid composition or membrane physical properties. These membrane properties could act either by favoring the membrane binding of downstream effectors or by modulating their activity. Several proteins can sense/generate membrane physical curvature (i.e. shape). However, the modulation of the activity of enzymes by a membrane's shape has not yet been reported. Here, using a cell-free assay with purified diacylglycerol kinase ϵ (DGKϵ) and liposomes, we studied the activity and acyl-chain specificity of an enzyme of the phosphatidylinositol (PI) cycle, DGKϵ. By systematically varying the model membrane lipid composition and physical properties, we found that DGKϵ has low activity and lacks acyl-chain specificity in locally flat membranes, regardless of the lipid composition. On the other hand, these enzyme properties were greatly enhanced in membrane structures with a negative Gaussian curvature. We also found that this is not a consequence of preferential binding of the enzyme to those structures, but rather is due to a curvature-mediated allosteric regulation of DGKϵ activity and acyl-chain specificity. Moreover, in a fine-tuned interplay between the enzyme and the membrane, DGKϵ favored the formation of structures with greater Gaussian curvature. DGKϵ does not bear a regulatory domain, and these findings reveal the importance of membrane curvature in regulating DGKϵ activity and acyl-chain specificity. Hence, this study highlights that a hierarchic coupling of membrane physical property and lipid composition synergistically regulates membrane signaling events. We propose that this regulatory mechanism of membrane-associated enzyme activity is likely more common than is currently appreciated.

The role of acid sphingomyelinase and modulation of sphingolipid metabolism in bacterial infection

2018 ◽  
Vol 399 (10) ◽  
pp. 1135-1146 ◽  
Author(s):  
Alexander Simonis ◽  
Alexandra Schubert-Unkmeir
Keyword(s):  
Intracellular Signaling ◽  
Bacterial Infections ◽  
Bacterial Pathogens ◽  
Infection Process ◽  
Acid Sphingomyelinase ◽  
Membrane Properties ◽  
Sphingolipid Metabolism ◽  
Membrane Structures ◽  
Key Enzyme ◽  
And Function

AbstractAcid sphingomyelinase (ASM) is a key enzyme in sphingolipid metabolism that converts sphingomyelin to ceramide, thereby modulating membrane structures and signal transduction. Bacterial pathogens can manipulate ASM activity and function, and use host sphingolipids during multiple steps of their infection process. An increase in ceramides upon infection results in the formation of ceramide-enriched membrane platforms that serve to cluster receptor molecules and organize intracellular signaling molecules, thus facilitating bacterial uptake. In this review, we focus on how extracellular bacterial pathogens target ASM and modulate membrane properties and signaling pathways to gain entry into eukaryotic cells or induce cell death. We describe how intracellular pathogens interfere with the intralysosomal functions of ASM to favor replication and survival. In addition, bacteria utilize their own sphingomyelinases as virulence factors to modulate sphingolipid metabolism. The potential of ASM as a target for treating bacterial infections is also discussed.

scholarly journals Modernization of NASA Johnson Space Center’s Chamber A to support Cryogenic Vacuum Optical Testing of the James Webb Space Telescope (JWST)

2021 ◽  
Vol 64 (1) ◽  
pp. 30-41
Author(s):  
Mary Cerimele ◽  
Jonathan Homan ◽  
Sam Garcia ◽  
Jaime Garza ◽  
Gabriel Hirsch ◽  
...  
Keyword(s):  
Vacuum Chamber ◽  
High Vacuum ◽  
Vacuum System ◽  
Thermal Vacuum ◽  
Space Telescope ◽  
James Webb Space Telescope ◽  
Cryogenic Vacuum ◽  
Optical Test ◽  
The World ◽  
Helium Refrigeration

Abstract NASA is the mission lead for the James Webb Space Telescope (JWST), the next of the “Great Observatories,” scheduled for launch in 2021. NASA is directly responsible for the integration and test (I&T) program that culminated in an end-to-end cryo vacuum optical test of the flight telescope and instrument module in Chamber A at NASA Johnson Space Center. Historic Chamber A is the largest thermal vacuum chamber at Johnson Space Center and one of the largest space simulation chambers in the world. Chamber A has undergone a major modernization effort to support the deep cryogenic, vacuum and cleanliness requirements for testing the JWST. This paper describes the upgrades to the Chamber A facility: Thermal Shrouds, Helium Refrigeration, Liquid Nitrogen System, High Vacuum System, Clean Airflow System, and Utilities.

Role of spectrin in membrane fusion and in shape change of human erythrocyte ghost

1978 ◽  
Vol 36 (2) ◽  
pp. 328-329
Author(s):  
Hideo Hayashi ◽  
Yoshikazu Hirai ◽  
John T. Penniston
Keyword(s):  
Conformational Changes ◽  
Human Erythrocyte ◽  
Shape Change ◽  
Membrane Surface ◽  
Slight Modification ◽  
Active Role ◽  
Main Role ◽  
Bank Blood ◽  
Human Erythrocyte Ghost

Spectrin is a membrane associated protein most of which properties have been tentatively elucidated. A main role of the protein has been assumed to give a supporting structure to inside of the membrane. As reported previously, however, the isolated spectrin molecule underwent self assemble to form such as fibrous, meshwork, dispersed or aggregated arrangements depending upon the buffer suspended and was suggested to play an active role in the membrane conformational changes. In this study, the role of spectrin and actin was examined in terms of the molecular arrangements on the erythrocyte membrane surface with correlation to the functional states of the ghosts.Human erythrocyte ghosts were prepared from either freshly drawn or stocked bank blood by the method of Dodge et al with a slight modification as described before. Anti-spectrin antibody was raised against rabbit by injection of purified spectrin and partially purified.

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