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Sample records for large-aperture membrane active

  1. Large-Aperture Membrane Active Phased-Array Antennas

    NASA Technical Reports Server (NTRS)

    Karasik, Boris; McGrath, William; Leduc, Henry

    2009-01-01

    Large-aperture phased-array microwave antennas supported by membranes are being developed for use in spaceborne interferometric synthetic aperture radar systems. There may also be terrestrial uses for such antennas supported on stationary membranes, large balloons, and blimps. These antennas are expected to have areal mass densities of about 2 kg/sq m, satisfying a need for lightweight alternatives to conventional rigid phased-array antennas, which have typical areal mass densities between 8 and 15 kg/sq m. The differences in areal mass densities translate to substantial differences in total mass in contemplated applications involving aperture areas as large as 400 sq m. A membrane phased-array antenna includes patch antenna elements in a repeating pattern. All previously reported membrane antennas were passive antennas; this is the first active membrane antenna that includes transmitting/receiving (T/R) electronic circuits as integral parts. Other integral parts of the antenna include a network of radio-frequency (RF) feed lines (more specifically, a corporate feed network) and of bias and control lines, all in the form of flexible copper strip conductors on flexible polymeric membranes. Each unit cell of a prototype antenna (see Figure 1) contains a patch antenna element and a compact T/R module that is compatible with flexible membrane circuitry. There are two membrane layers separated by a 12.7-mm air gap. Each membrane layer is made from a commercially available flexible circuit material that, as supplied, comprises a 127-micron-thick polyimide dielectric layer clad on both sides with 17.5-micron-thick copper layers. The copper layers are patterned into RF, bias, and control conductors. The T/R module is located on the back side of the ground plane and is RF-coupled to the patch element via a slot. The T/R module is a hybrid multilayer module assembled and packaged independently and attached to the membrane array. At the time of reporting the information for

  2. Fabrication of large-aperture, high efficiency, Fresnel diffractive membrane optic for space telescope

    NASA Astrophysics Data System (ADS)

    Zhang, Jian; Li, Mengjuan; Yin, Ganghua; Jiao, Jianchao; Liu, Zhengkun; Xu, Xiangdong; Fu, Shaojun

    2016-10-01

    Diffractive optical system can be a favorable choice for large-aperture space telescope to reduce the mass and size of image system. To meet the demand of large-aperture, high efficiency, lightweight diffractive optic for high resolution remote sensing, a 200 mm diameter, 20 μmthick, 4-level diffractive membrane fabricated is shown to have over 62% diffraction efficiency into the +1 order, with 0.051 efficiency RMS. Over 66% diffraction efficiency is achieved for a 100 mm aperture membrane, with 0.023 efficiency RMS. The membrane thickness uniformity control is discussed and 8 nm wave front error RMS is achieved in 100 mm diameter.

  3. Structural-optical integrated analysis on the large aperture mirror with active mounting

    NASA Astrophysics Data System (ADS)

    Ren, Zhiyuan; Zhu, Jianqiang; Liu, Zhigang

    2016-11-01

    Deformation of the large aperture mirror caused by the external environment load seriously affects the optical performance of the optical system, and there is a limit to develop the shape quality of large aperture mirror with traditional mounting method. It is effective way to reduce the optical mirror distortion with active support method, and the structural-optical integrated method is the effective means to assess the merits of the mounting for large aperture mirror. Firstly, we proposes a new support scheme that uses specific boundary constraints on the large lens edges and imposes flexible torque to resist deformation induced by gravity to improve surface quantity of large aperture mirror. We calculate distortion of the large aperture mirror at the edges of the flexible torque respectively with the finite element method; secondly, we extract distortion value within clear aperture of the mirror with MATLAB, solve the corresponding Zernike polynomial coefficients; lastly, we obtain the peak-valley value (PV) and root mean square value (RMS) with optical-structural integrated analysis . The results for the 690x400x100mm mirror show that PV and RMS values within the clear aperture with 0.4MPa torques than the case without applying a flexible torque reduces 82.7% and 72.9% respectively. The active mounting on the edge of the large aperture mirror can greatly improve the surface quality of the large aperture mirror.

  4. Large aperture deformable mirror with a transferred single-crystal silicon membrane actuated using large-stroke PZT Unimorph Actuators

    NASA Technical Reports Server (NTRS)

    Hishinumat, Yoshikazu; Yang, Eui - Hyeok (EH)

    2005-01-01

    We have demonstrated a large aperture (50 mm x 50 mm) continuous membrane deformable mirror (DM) with a large-stroke piezoelectric unimorph actuator array. The DM consists of a continuous, large aperture, silicon membrane 'transferred' in its entirety onto a 20 x 20 piezoelectric unimorph actuator array. A PZT unimorph actuator, 2.5 mm in diameter with optimized PZT/Si thickness and design showed a deflection of 5.7 [m at 20V. An assembled DM showed an operating frequency bandwidth of 30 kHz and influence function of approximately 30%.

  5. Horizon: A Proposal for Large Aperture, Active Optics in Geosynchronous Orbit

    NASA Technical Reports Server (NTRS)

    Chesters, Dennis; Jenstrom, Del

    2000-01-01

    In 1999, NASA's New Millennium Program called for proposals to validate new technology in high-earth orbit for the Earth Observing-3 (NMP EO3) mission to fly in 2003. In response, we proposed to test a large aperture, active optics telescope in geosynchronous orbit. This would flight-qualify new technologies for both Earth and Space science: 1) a future instrument with LANDSAT image resolution and radiometric quality watching continuously from geosynchronous station, and 2) the Next Generation Space Telescope (NGST) for deep space imaging. Six enabling technologies were to be flight-qualified: 1) a 3-meter, lightweight segmented primary mirror, 2) mirror actuators and mechanisms, 3) a deformable mirror, 4) coarse phasing techniques, 5) phase retrieval for wavefront control during stellar viewing, and 6) phase diversity for wavefront control during Earth viewing. Three enhancing technologies were to be flight- validated: 1) mirror deployment and latching mechanisms, 2) an advanced microcontroller, and 3) GPS at GEO. In particular, two wavefront sensing algorithms, phase retrieval by JPL and phase diversity by ERIM International, were to sense optical system alignment and focus errors, and to correct them using high-precision mirror mechanisms. Active corrections based on Earth scenes are challenging because phase diversity images must be collected from extended, dynamically changing scenes. In addition, an Earth-facing telescope in GEO orbit is subject to a powerful diurnal thermal and radiometric cycle not experienced by deep-space astronomy. The Horizon proposal was a bare-bones design for a lightweight large-aperture, active optical system that is a practical blend of science requirements, emerging technologies, budget constraints, launch vehicle considerations, orbital mechanics, optical hardware, phase-determination algorithms, communication strategy, computational burdens, and first-rate cooperation among earth and space scientists, engineers and managers

  6. Development and testing of an actively controlled large-aperture Cassegrain Telescope for spacecraft deployment

    NASA Astrophysics Data System (ADS)

    Boone, Bradley G.; Bruzzi, Jonathan R.; Kluga, Bernard E.; Rogala, Eric W.; Hale, R. D.; Chen, Peter C.

    2004-10-01

    The National Aeronautics and Space Administration (NASA) is planning future deep space missions requiring space-based imaging reconnaissance of planets and recovery of imagery from these missions via optical communications. Both applications have similar requirements that can be met by a common aperture. The Johns Hopkins University Applied Physics Laboratory in collaboration with commercial and academic partners is developing a new approach to deploying and controlling large aperture (meter-class) optical telescopes on spacecraft that can be rapidly launched and deployed. The deployment mechanism uses flexible longeron struts to deploy the secondary. The active control system uses a fiber-coupled laser array near the focal plane that reflects four collimated laser beams off of the periphery of the secondary to four equally-disposed quad cell sensors at the periphery of the primary to correct secondary-to-primary misalignments and enable motion compensation. We describe a compensation technique that uses tip/tilt and piston actuators for quasi-static bias correction and dynamic motion compensation. We also describe preliminary optical tests using a commercial Schmidt-Cassegrain telescope in lieu of an ultra-lightweight composite Cassegrain, which is under development by Composite Mirror Applications, Inc. Finite element and ray trace modeling results for a 40 cm composite telescope design will also be described.

  7. Laboratory demonstration of a primary active mirror for space with the LATT: large aperture telescope technology

    NASA Astrophysics Data System (ADS)

    Briguglio, Runa; Biasi, Roberto; Gallieni, Daniele; Vettore, Christian; d'Amato, Francesco; Xompero, Marco; Arcidiacono, Carmelo; Lisi, Franco; Riccardi, Armando; Patauner, Christian; Lazzarini, Paolo; Tintori, Matteo; Duò, Fabrizio; Pucci, Mauro; Zuccaro Marchi, Alessandro; Maresi, Luca

    2016-07-01

    The LATT project is an ESA contract under TRP programme to demonstrate the scalability of the technology from ground-based adaptive mirrors to space active primary mirrors. A prototype spherical mirror based on a 40 cm diameter 1 mm thin glass shell with 19 contactless, voice-coil actuators and co-located position sensors have been manufactured and integrated into a final unit with an areal density lower than 20 kg/m2. Laboratory tests demonstrated the controllability with very low power budget and the survival of the fragile glass shell exposed to launch accelerations, thanks to an electrostatic locking mechanism; such achievements pushes the technology readiness level toward 5. With this prototype, the LATT project explored the feasibility of using an active and lightweight primary for space telescopes. The concept is attractive for large segmented telescopes, with surface active control to shape and co-phase them once in flight. In this paper we will describe the findings of the technological advances and the results of the environmental and optical tests.

  8. Large aperture diffractive space telescope

    DOEpatents

    Hyde, Roderick A.

    2001-01-01

    A large (10's of meters) aperture space telescope including two separate spacecraft--an optical primary objective lens functioning as a magnifying glass and an optical secondary functioning as an eyepiece. The spacecraft are spaced up to several kilometers apart with the eyepiece directly behind the magnifying glass "aiming" at an intended target with their relative orientation determining the optical axis of the telescope and hence the targets being observed. The objective lens includes a very large-aperture, very-thin-membrane, diffractive lens, e.g., a Fresnel lens, which intercepts incoming light over its full aperture and focuses it towards the eyepiece. The eyepiece has a much smaller, meter-scale aperture and is designed to move along the focal surface of the objective lens, gathering up the incoming light and converting it to high quality images. The positions of the two space craft are controlled both to maintain a good optical focus and to point at desired targets which may be either earth bound or celestial.

  9. the Large Aperture GRB Observatory

    SciTech Connect

    Bertou, Xavier

    2009-04-30

    The Large Aperture GRB Observatory (LAGO) aims at the detection of high energy photons from Gamma Ray Bursts (GRB) using the single particle technique (SPT) in ground based water Cherenkov detectors (WCD). To reach a reasonable sensitivity, high altitude mountain sites have been selected in Mexico (Sierra Negra, 4550 m a.s.l.), Bolivia (Chacaltaya, 5300 m a.s.l.) and Venezuela (Merida, 4765 m a.s.l.). We report on the project progresses and the first operation at high altitude, search for bursts in 6 months of preliminary data, as well as search for signal at ground level when satellites report a burst.

  10. Large Aperture Scintillometer Intercomparison Study

    NASA Astrophysics Data System (ADS)

    Kleissl, J.; Gomez, J.; Hong, S.-H.; Hendrickx, J. M. H.; Rahn, T.; Defoor, W. L.

    2008-07-01

    Two field studies with six large aperture scintillometers (LASs) were performed using horizontal and slant paths. The accuracy of this novel and increasingly popular technique for measuring sensible heat fluxes was quantified by comparing measurements from different instruments over nearly identical transects. Random errors in LAS measurements were small, since correlation coefficients between adjacent measurements were greater than 0.995. However, for an ideal set-up differences in linear regression slopes of up to 21% were observed with typical inter-instrument differences of 6%. Differences of 10% are typical in more realistic measurement scenarios over homogeneous natural vegetation and different transect heights and locations. Inaccuracies in the optics, which affect the effective aperture diameter, are the most likely explanation for the observed differences.

  11. Large aperture Fresnel telescopes/011

    SciTech Connect

    Hyde, R.A., LLNL

    1998-07-16

    At Livermore we`ve spent the last two years examining an alternative approach towards very large aperture (VLA) telescopes, one based upon transmissive Fresnel lenses rather than on mirrors. Fresnel lenses are attractive for VLA telescopes because they are launchable (lightweight, packagable, and deployable) and because they virtually eliminate the traditional, very tight, surface shape requirements faced by reflecting telescopes. Their (potentially severe) optical drawback, a very narrow spectral bandwidth, can be eliminated by use of a second (much smaller) chromatically-correcting Fresnel element. This enables Fresnel VLA telescopes to provide either single band ({Delta}{lambda}/{lambda} {approximately} 0.1), multiple band, or continuous spectral coverage. Building and fielding such large Fresnel lenses will present a significant challenge, but one which appears, with effort, to be solvable.

  12. Very Large Aperture Diffractive Space Telescope

    SciTech Connect

    Hyde, Roderick Allen

    1998-04-20

    A very large (10's of meters) aperture space telescope including two separate spacecraft--an optical primary functioning as a magnifying glass and an optical secondary functioning as an eyepiece. The spacecraft are spaced up to several kilometers apart with the eyepiece directly behind the magnifying glass ''aiming'' at an intended target with their relative orientation determining the optical axis of the telescope and hence the targets being observed. The magnifying glass includes a very large-aperture, very-thin-membrane, diffractive lens, e.g., a Fresnel lens, which intercepts incoming light over its full aperture and focuses it towards the eyepiece. The eyepiece has a much smaller, meter-scale aperture and is designed to move along the focal surface of the magnifying glass, gathering up the incoming light and converting it to high quality images. The positions of the two space craft are controlled both to maintain a good optical focus and to point at desired targets.

  13. Eyeglass. 1. Very large aperture diffractive telescopes.

    PubMed

    Hyde, R A

    1999-07-01

    The Eyeglass is a very large aperture (25-100-m) space telescope consisting of two distinct spacecraft, separated in space by several kilometers. A diffractive lens provides the telescope s large aperture, and a separate, much smaller, space telescope serves as its mobile eyepiece. Use of a transmissive diffractive lens solves two basic problems associated with very large aperture space telescopes; it is inherently launchable (lightweight, packagable, and deployable) it and virtually eliminates the traditional, very tight surface shape tolerances faced by reflecting apertures. The potential drawback to use of a diffractive primary (very narrow spectral bandwidth) is eliminated by corrective optics in the telescope s eyepiece; the Eyeglass can provide diffraction-limited imaging with either single-band (Deltalambda/lambda approximately 0.1), multiband, or continuous spectral coverage.

  14. Eyeglass. 1. Very large aperture diffractive telescopes

    SciTech Connect

    Hyde, R.A.

    1999-07-01

    The Eyeglass is a very large aperture (25{endash}100-m) space telescope consisting of two distinct spacecraft, separated in space by several kilometers. A diffractive lens provides the telescope{close_quote}s large aperture, and a separate, much smaller, space telescope serves as its mobile eyepiece. Use of a transmissive diffractive lens solves two basic problems associated with very large aperture space telescopes; it is inherently launchable (lightweight, packagable, and deployable) it and virtually eliminates the traditional, very tight surface shape tolerances faced by reflecting apertures. The potential drawback to use of a diffractive primary (very narrow spectral bandwidth) is eliminated by corrective optics in the telescope{close_quote}s eyepiece; the Eyeglass can provide diffraction-limited imaging with either single-band ({Delta}{lambda}/{lambda}{approximately}0.1), multiband, or continuous spectral coverage. {copyright} 1999 Optical Society of America

  15. Large aperture adaptive optics for intense lasers

    NASA Astrophysics Data System (ADS)

    Deneuville, François; Ropert, Laurent; Sauvageot, Paul; Theis, Sébastien

    2015-05-01

    ISP SYSTEM has developed a range of large aperture electro-mechanical deformable mirrors (DM) suitable for ultra short pulsed intense lasers. The design of the MD-AME deformable mirror is based on force application on numerous locations thanks to electromechanical actuators driven by stepper motors. DM design and assembly method have been adapted to large aperture beams and the performances were evaluated on a first application for a beam with a diameter of 250mm at 45° angle of incidence. A Strehl ratio above 0.9 was reached for this application. Simulations were correlated with measurements on optical bench and the design has been validated by calculation for very large aperture (up to Ø550mm). Optical aberrations up to Zernike order 5 can be corrected with a very low residual error as for actual MD-AME mirror. Amplitude can reach up to several hundreds of μm for low order corrections. Hysteresis is lower than 0.1% and linearity better than 99%. Contrary to piezo-electric actuators, the μ-AME actuators avoid print-through effects and they permit to keep the mirror shape stable even unpowered, providing a high resistance to electro-magnetic pulses. The MD-AME mirrors can be adapted to circular, square or elliptical beams and they are compatible with all dielectric or metallic coatings.

  16. Large Aperture, Scanning, L-Band SAR

    NASA Technical Reports Server (NTRS)

    Moussessian, Alina; Del Castillo, Linda; Bach, Vinh; Grando, Maurio; Quijano, Ubaldo; Smith, Phil; Zawadzki, Mark

    2011-01-01

    We have developed the first L-band membrane-based active phased array. The antenna is a 16x16 element patch array with dimensions of 2.3mx2.6m. The array uses membrane-compatible Transmit/Receive (T/R) modules for electronic beam steering. We will discuss the antenna design, the fabrication of this large array, the T/R module development, the signal distribution approach and the measured results of the array.

  17. Large Aperture, Scanning, L-Band SAR

    NASA Technical Reports Server (NTRS)

    Moussessian, Alina; DelCastillo, Linda; Bach, Vinh; Grando, Maurio; Quijano, Ubaldo; Smith, Phil; Zawadzki, Mark

    2011-01-01

    We have developed the first L-band membrane-based active phased array. The antenna is a 16x16 element patch array with dimensions of 2.3mx2.6m. The array uses membrane-compatible Transmit/Receive (T/R) modules for electronic beam steering. We will discuss the antenna design, the fabrication of this large array, the T/R module development, the signal distribution approach and the measured results of the array

  18. Saturation of the Large Aperture Scintillometer

    NASA Astrophysics Data System (ADS)

    Kohsiek, W.; Meijninger, W. M. L.; Debruin, H. A. R.; Beyrich, F.

    2006-10-01

    The saturation aspects of a large aperture (0.3 m) scintillometer operating over a 10-km path were investigated. Measurements were made over mainly forested, hilly terrain with typical maximum sensible heat fluxes of 300-400 W m -2, and over flat terrain with mainly grass, and typical maximum heat fluxes of 100-150 W m-2. Scintillometer-based fluxes were compared with eddy-correlation observations. Two different schemes for calculating the reduction of scintillation caused by saturation were applied: one based on the work of Hill and Clifford, the other based on Frehlich and Ochs. Without saturation correction, the scintillation fluxes were lower than the eddy-correlation fluxes; the saturation correction according to Frehlich and Ochs increased the scintillometer fluxes to an unrealistic level. Correcting the fluxes after the theory of the Hill and Clifford gave satisfying results

  19. Design of large aperture focal plane shutter

    NASA Astrophysics Data System (ADS)

    Hu, Jia-wen; Ma, Wen-li; Huang, Jin-long

    2012-09-01

    To satisfy the requirement of large telescope, a large aperture focal plane shutter with aperture size of φ200mm was researched and designed to realize, which could be started and stopped in a relative short time with precise position, and also the blades could open and close at the same time at any orientation. Timing-belts and stepper motors were adopted as the drive mechanism. Velocity and position of the stepper motors were controlled by the PWM pulse generated by DSP. Exponential curve is applied to control the velocity of the stepper motors to make the shutter start and stop in a short time. The closing/open time of shutter is 0.2s, which meets the performance requirements of large telescope properly.

  20. Low-cost Large Aperture Telescopes for Optical Communications

    NASA Technical Reports Server (NTRS)

    Hemmati, Hamid

    2006-01-01

    Low-cost, large-aperture optical receivers are required to form an affordable optical ground receiver network for laser communications. Among the ground receiver station's multiple subsystems, here, we only discuss the ongoing research activities aimed at reducing the cost of the large-size optics on the receiver. Experimental results of two different approaches for fabricating low-cost mirrors of wavefront quality on the order of 100-200X the diffraction limit are described. Laboratory-level effort are underway to improve the surface figure to better than 20X the diffraction limit.

  1. Design of large aperture, low mass vacuum windows

    SciTech Connect

    Leonhardt, W.J.; Mapes, M.

    1993-07-01

    Large vacuum vessels are employed downstream of fixed targets in High Energy Physics experiments to provide a long path for particles to traverse without interacting with air molecules. These vessels generally have a large aperture opening known as a vacuum window which employs a thin membrane to preserve the vacuum environment yet allows the particles to pass through with a minimal effect on them. Several large windows have been built using a composite of Kevlar/Mylar including circular windows to a diameter of 96.5 cm and rectangular windows up to 193 cm x 86 cm. This paper describes the design, fabrication, testing and operating experience with these windows and relates the actual performance to theoretical predictions.

  2. Design of large aperture, low mass vacuum windows

    SciTech Connect

    Leonhardt, W.J.; Mapes, M.

    1993-01-01

    Large vacuum vessels are employed downstream of fixed targets in High Energy Physics experiments to provide a long path for particles to traverse without interacting with air molecules. These vessels generally have a large aperture opening known as a vacuum window which employs a thin membrane to preserve the vacuum environment yet allows the particles to pass through with a minimal effect on them. Several large windows have been built using a composite of Kevlar/Mylar including circular windows to a diameter of 96.5 cm and rectangular windows up to 193 cm x 86 cm. This paper describes the design, fabrication, testing and operating experience with these windows and relates the actual performance to theoretical predictions.

  3. Development of large aperture composite adaptive optics

    NASA Astrophysics Data System (ADS)

    Kmetik, Viliam; Vitovec, Bohumil; Jiran, Lukas; Nemcova, Sarka; Zicha, Josef; Inneman, Adolf; Mikulickova, Lenka; Pavlica, Richard

    2015-01-01

    Large aperture composite adaptive optics for laser applications is investigated in cooperation of Institute of Plasma Physic, Department of Instrumentation and Control Engineering FME CTU and 5M Ltd. We are exploring opportunity of a large-size high-power-laser deformable-mirror production using a lightweight bimorph actuated structure with a composite core. In order to produce a sufficiently large operational free aperture we are developing new technologies for production of flexible core, bimorph actuator and deformable mirror reflector. Full simulation of a deformable-mirrors structure was prepared and validated by complex testing. A deformable mirror actuation and a response of a complicated structure are investigated for an accurate control of the adaptive optics. An original adaptive optics control system and a bimorph deformable mirror driver were developed. Tests of material samples, components and sub-assemblies were completed. A subscale 120 mm bimorph deformable mirror prototype was designed, fabricated and thoroughly tested. A large-size 300 mm composite-core bimorph deformable mirror was simulated and optimized, fabrication of a prototype is carried on. A measurement and testing facility is modified to accommodate large sizes optics.

  4. Very large aperture optics for space applications

    NASA Astrophysics Data System (ADS)

    Horwath, T. G.; Smith, J. P.; Johnson, M. T.

    1994-09-01

    A new type of space optics technology is presented which promises the realization of very large apertures (tens of meters), while packagable into lightweight, small volume containers compatible with conventional launch vehicles. This technology makes use of thin foils of circular shape which are uniformly mass loaded around the perimeter. Once unfurled and set into rapid rotation about the transversal axis, the foil is stretched into a perfectly flat plane by the centrifugal forces acting on the peripheral masses. The simplest applications of this novel technology are optically flat reflectors, using metallized foils of Mylar, Kevlar, or Kapton. Other more complex optical components can be realized by use of binary optics techniques, such as depositing holograms by selective local microscale removal of the reflective surface. Electrostatic techniques, in conjunction with an auxiliary foil, under local, distributed real-time control of the optical parameters, allow implementation of functions like beam steering and focal length adjustments. Gas pressurization allows stronger curvatures and thus smaller focal ratios for non-imaging applications. Limits on aperture are imposed primarily by manufacturing capabilities. Applications of such large optics in space are numerous. They range from military, such as space based lasers, to the civilian ones of power beaming, solar energy collection, and astronomy. This paper examines this simple and innovative concept in detail, discusses deployment and attitude control issues and presents approaches for realization.

  5. Ultrasonic material characterization using large-aperture PVDF receivers.

    PubMed

    Adamowski, J C; Buiochi, F; Higuti, R T

    2010-02-01

    This work describes the use of a large-aperture PVDF receiver in the measurement of liquid density and composite material elastic constants. The density measurement of several liquids is obtained with accuracy of 0.2% using a conventional NDE emitter transducer and a 70-mm-diameter, 52-microm P(VDF-TrFE) membrane with gold electrodes. The determination of the elastic constants is based on the phase velocity measurement. Diffraction can lead to errors around 1% in velocity measurement when using alternatively the conventional pair of ultrasonic transducers (1-MHz frequency and 19-mm-diameter) operating in through-transmission mode, separated by a distance of 100 mm. This effect is negligible when using a pair of 10-MHz, 19-mm-diameter transducers. Nevertheless, the dispersion at 10 MHz can result in errors of about 0.5%, when measuring the velocity in composite materials. The use of an 80-mm diameter, 52-microm-thick PVDF membrane receiver practically eliminates the diffraction effects in phase velocity measurement. The elastic constants of a carbon fiber reinforced polymer were determined and compared with the values obtained by a tensile test.

  6. A Future Large-Aperture UVOIR Space Observatory: Study Overview

    NASA Astrophysics Data System (ADS)

    Postman, Marc; Thronson, Harley A.; Feinberg, Lee; Redding, David; Stahl, H. Philip

    2015-01-01

    The scientific drivers for very high angular resolution coupled with very high sensitivity and wavefront stability in the UV and optical wavelength regime have been well established. These include characterization of exoplanets in the habitable zones of solar type stars, probing the physical properties of the circumgalactic medium around z < 2 galaxies, and resolving stellar populations across a broad range of galactic environments. The 2010 NRC Decadal Survey and the 2013 NASA Science Mission Directorate 30-Year Roadmap identified a large-aperture UVOIR observatory as a priority future space mission. Our joint NASA GSFC/JPL/MSFC/STScI team has extended several earlier studies of the technology and engineering requirements needed to design and build a single filled aperture 10-meter class space-based telescope that can enable these ambitious scientific observations. We present here an overview of our new technical work including a brief summary of the reference science drivers as well as in-depth investigations of the viable telescope architectures, the requirements on thermal control and active wavefront control systems, and the range of possible launch configurations.

  7. Eyeglass: A Very Large Aperture Diffractive Space Telescope

    SciTech Connect

    Hyde, R; Dixit, S; Weisberg, A; Rushford, M

    2002-07-29

    Eyeglass is a very large aperture (25-100 meter) space telescope consisting of two distinct spacecraft, separated in space by several kilometers. A diffractive lens provides the telescope's large aperture, and a separate, much smaller, space telescope serves as its mobile eyepiece. Use of a transmissive diffractive lens solves two basic problems associated with very large aperture space telescopes; it is inherently fieldable (lightweight and flat, hence packagable and deployable) and virtually eliminates the traditional, very tight, surface shape tolerances faced by reflecting apertures. The potential drawback to use of a diffractive primary (very narrow spectral bandwidth) is eliminated by corrective optics in the telescope's eyepiece. The Eyeglass can provide diffraction-limited imaging with either single-band, multiband, or continuous spectral coverage. Broadband diffractive telescopes have been built at LLNL and have demonstrated diffraction-limited performance over a 40% spectral bandwidth (0.48-0.72 {micro}m). As one approach to package a large aperture for launch, a foldable lens has been built and demonstrated. A 75 cm aperture diffractive lens was constructed from 6 panels of 1 m thick silica; it achieved diffraction-limited performance both before and after folding. This multiple panel, folding lens, approach is currently being scaled-up at LLNL. We are building a 5 meter aperture foldable lens, involving 72 panels of 700 {micro}m thick glass sheets, diffractively patterned to operate as coherent f/50 lens.

  8. Fabrication and applications of large aperture diffractive optics

    SciTech Connect

    Dixit, S; Britten, J B; Hyde, R; Rushford, M; Summers, L; Toeppen, J

    2002-02-19

    Large aperture diffractive optics are needed in high power laser applications to protect against laser damage during operation and in space applications to increase the light gathering power and consequently the signal to noise. We describe the facilities we have built for fabricating meter scale diffractive optics and discuss several examples of these.

  9. Mission definition for a large-aperture microwave radiometer spacecraft

    NASA Technical Reports Server (NTRS)

    Keafer, L. S., Jr.

    1981-01-01

    An Earth-observation measurements mission is defined for a large-aperture microwave radiometer spacecraft. This mission is defined without regard to any particular spacecraft design concept. Space data application needs, the measurement selection rationale, and broad spacecraft design requirements and constraints are described. The effects of orbital parameters and image quality requirements on the spacecraft and mission performance are discussed. Over the land the primary measurand is soil moisture; over the coastal zones and the oceans important measurands are salinity, surface temperature, surface winds, oil spill dimensions and ice boundaries; and specific measurement requirements have been selected for each. Near-all-weather operation and good spatial resolution are assured by operating at low microwave frequencies using an extremely large aperture antenna in a low-Earth-orbit contiguous mapping mode.

  10. Comparison of large aperture telescopes with parabolic and spherical primaries

    NASA Technical Reports Server (NTRS)

    Korsch, D.

    1986-01-01

    Quasi-Cassegrain-type four-mirror telescopes are compared to conventional two-mirror Cassegrain telescopes for use as high performance, very large aperture space telescopes. Spherical and parabolic primaries with continuous as well as segmented surfaces are considered. Imaging characteristics and misalignment sensitivities serve as the principal criteria of comparison. The evaluation shows that parabolic primaries yield superior wide-field performance, whereas spherical primaries hold distinct advantages regarding manufacturability and regarding certain alignment aspects in the case of segmentation.

  11. Zinc selenide-based large aperture photo-controlled deformable mirror.

    PubMed

    Quintavalla, Martino; Bonora, Stefano; Natali, Dario; Bianco, Andrea

    2016-06-01

    Realization of large aperture deformable mirrors with a large density of actuators is important in many applications, and photo-controlled deformable mirrors (PCDMs) represent an innovation. Herein we show that PCDMs are scalable realizing a 2-inch aperture device based on a polycrystalline zinc selenide (ZnSe) as the photoconductive substrate and a thin polymeric reflective membrane. ZnSe is electrically characterized and analyzed through a model that we previously introduced. The PCDM is then optically tested, demonstrating its capabilities in adaptive optics.

  12. Operational aspects of the Main Injector large aperture quadrupole (WQB)

    SciTech Connect

    Chou, W.; Bartelson, L.; Brown, B.; Capista, D.; Crisp, J.; DiMarco, J.; Fitzgerald, J.; Glass, H.; Harding, D.; Johnson, D.; Kashikhin, V.; /Fermilab

    2007-06-01

    A two-year Large Aperture Quadrupole (WQB) Project was completed in the summer of 2006 at Fermilab. [1] Nine WQBs were designed, fabricated and bench-tested by the Technical Division. Seven of them were installed in the Main Injector and the other two for spares. They perform well. The aperture increase meets the design goal and the perturbation to the lattice is minimal. The machine acceptance in the injection and extraction regions is increased from 40{pi} to 60{pi} mm-mrad. This paper gives a brief report of the operation and performance of these magnets. Details can be found in Ref [2].

  13. Large-aperture interferometer using local reference beam

    NASA Technical Reports Server (NTRS)

    Howes, W. L.

    1982-01-01

    A large-aperture interferometer was devised by adding a local-reference-beam-generating optical system to a schlieren system. Two versions of the interferometer are demonstrated, one employing 12.7 cm (5 in.) diameter schlieren optics, the other employing 30.48 cm (12 in.) diameter parabolic mirrors in an off-axis system. In the latter configuration a cylindrical lens is introduced near the light source to correct for astigmatism. A zone plate is a satisfactory decollimating element in the reference-beam arm of the interferometer. Attempts to increase the flux and uniformity of irradiance in the reference beam by using a diffuser are discussed.

  14. Metrology measurements for large-aperture VPH gratings

    NASA Astrophysics Data System (ADS)

    Zheng, Jessica R.; Gers, Luke; Heijmans, Jeroen

    2013-09-01

    The High Efficiency and Resolution Multi Element Spectrograph (HERMES) for the Australian Astronomical Observatory (AAO) uses four large aperture, high angle of incidence volume phase holographic gratings (VPHG) for high resolution `Galactic archaeology' spectroscopy. The large clear aperture, the high diffraction efficiency, the line frequency homogeneity, and mosaic alignment made manufacturing and testing challenging. We developed new metrology systems at the AAO to verify the performance of these VPH gratings. The measured diffraction efficiencies and line frequency of the VPH gratings received so far meet the vendor's provided data. The wavefront quality for the Blue VPH grating is good but the Green and Red VPH gratings need to be post polishing.

  15. Self-Referencing Hartmann Test for Large-Aperture Telescopes

    NASA Technical Reports Server (NTRS)

    Korechoff, Robert P.; Oseas, Jeffrey M.

    2010-01-01

    A method is proposed for end-to-end, full aperture testing of large-aperture telescopes using an innovative variation of a Hartmann mask. This technique is practical for telescopes with primary mirrors tens of meters in diameter and of any design. Furthermore, it is applicable to the entire optical band (near IR, visible, ultraviolet), relatively insensitive to environmental perturbations, and is suitable for ambient laboratory as well as thermal-vacuum environments. The only restriction is that the telescope optical axis must be parallel to the local gravity vector during testing. The standard Hartmann test utilizes an array of pencil beams that are cut out of a well-corrected wavefront using a mask. The pencil beam array is expanded to fill the full aperture of the telescope. The detector plane of the telescope is translated back and forth along the optical axis in the vicinity of the nominal focal plane, and the centroid of each pencil beam image is recorded. Standard analytical techniques are then used to reconstruct the telescope wavefront from the centroid data. The expansion of the array of pencil beams is usually accomplished by double passing the beams through the telescope under test. However, this requires a well-corrected, autocollimation flat, the diameter or which is approximately equal to that of the telescope aperture. Thus, the standard Hartmann method does not scale well because of the difficulty and expense of building and mounting a well-corrected, large aperture flat. The innovation in the testing method proposed here is to replace the large aperture, well-corrected, monolithic autocollimation flat with an array of small-aperture mirrors. In addition to eliminating the need for a large optic, the surface figure requirement for the small mirrors is relaxed compared to that required of the large autocollimation flat. The key point that allows this method to work is that the small mirrors need to operate as a monolithic flat only with regard to

  16. Large-aperture, high-damage-threshold optics for beamlet

    SciTech Connect

    Campbell, J.H.; Atherton, L.J.; DeYoreo, J.J.

    1996-06-01

    Beamlet serves as a test bed for the proposed National Ignition Facility (NIF) laser design and components. Therefore, its optics are similar in size and quality to those proposed for the NIF. In general, the optics in the main laser cavity and transport section of Beamlet are larger and have higher damage thresholds than the optics manufactured for any of the previous laser systems. In addition, the quality of the Beamlet optical materials is higher, leading to better wavefront quality, higher optical transmission, and lower-intensity modulation of the output laser beam than, for example, that typically achieved on Nova. In this article, the authors discuss the properties and characteristics of the large-aperture optics used on Beamlet.

  17. Large aperture Stark modulated retroreflector at 10.8 microns

    NASA Astrophysics Data System (ADS)

    Klein, M. B.; Sipman, R. H.

    1980-12-01

    The Stark effect was used to construct a longitudinal field amplitude modulator with a large aperture and a wide field of view. Important features of the modulator are its insensitivity to polarization and its incorporation of multiple interaction regions to increase the modulation depth. The Stark interaction which was employed makes use of a (C-13)O2 laser source (so that atmospheric absorption should be low) and a molecule (NH3) with a particularly large absorption cross section. The modulator is mounted directly on a corner cube reflector, which allows the remote modulation of a beacon laser. The device has an aperture of 5.5 cm, a field of view of 38 deg, and a measured modulation depth of 25% at 1.4 MHz.

  18. A Future Large-Aperture UVOIR Space Observatory: Reference Designs

    NASA Technical Reports Server (NTRS)

    Thronson, Harley; Rioux, Norman; Feinberg, Lee; Stahl, H. Philip; Redding, Dave; Jones, Andrew; Sturm, James; Collins, Christine; Liu, Alice

    2015-01-01

    Our joint NASA GSFC/JPL/MSFC/STScI study team has used community-provided science goals to derive mission needs, requirements, and candidate mission architectures for a future large-aperture, non-cryogenic UVOIR space observatory. We describe the feasibility assessment of system thermal and dynamic stability for supporting coronagraphy. The observatory is in a Sun-Earth L2 orbit providing a stable thermal environment and excellent field of regard. Reference designs include a 36-segment 9.2 m aperture telescope that stows within a five meter diameter launch vehicle fairing. Performance needs developed under the study are traceable to a variety of reference designs including options for a monolithic primary mirror.

  19. A future large-aperture UVOIR space observatory: reference designs

    NASA Astrophysics Data System (ADS)

    Rioux, Norman; Thronson, Harley; Feinberg, Lee; Stahl, H. Philip; Redding, Dave; Jones, Andrew; Sturm, James; Collins, Christine; Liu, Alice

    2015-09-01

    Our joint NASA GSFC/JPL/MSFC/STScI study team has used community-provided science goals to derive mission needs, requirements, and candidate mission architectures for a future large-aperture, non-cryogenic UVOIR space observatory. We describe the feasibility assessment of system thermal and dynamic stability for supporting coronagraphy. The observatory is in a Sun-Earth L2 orbit providing a stable thermal environment and excellent field of regard. Reference designs include a 36-segment 9.2 m aperture telescope that stows within a five meter diameter launch vehicle fairing. Performance needs developed under the study are traceable to a variety of reference designs including options for a monolithic primary mirror.

  20. Development of a large aperture Nb3Sn racetrack quadrupolemagnet

    SciTech Connect

    Ferracin, Paolo; Bartlett, Scott E.; Caspi, Shlomo; Dietderich,Daniel R.; Gourlay, Steven A.; Hannaford, Charles R.; Hafalia, AurelioR.; Lietzke, Alan F.; Mattafirri, Sara; McInturff, Alfred D.; Nyman,Mark; Sabbi, Gianluca

    2005-04-14

    The U.S. LHC Accelerator Research Program (LARP), a collaboration between BNL, FNAL, LBNL, and SLAC, has among its major objectives the development of advanced magnet technology for an LHC luminosity upgrade. The LBNL Superconducting Magnet Group supports this program with a broad effort involving design studies, Nb{sub 3}Sn conductor development, mechanical models, and basic prototypes. This paper describes the development of a large aperture Nb{sub 3}Sn racetrack quadrupole magnet using four racetrack coils from the LBNL Subscale Magnet (SM) Program. The magnet provides a gradient of 95 T/m in a 110 mm bore, with a peak field in the conductor of 11.2 T. The coils are prestressed by a mechanical structure based on a pre-tensioned aluminum shell, and axially supported with aluminum rods. The mechanical behavior has been monitored with strain gauges and the magnetic field has been measured. Results of the test are reported and analyzed.

  1. Phased Array Mirror Extendible Large Aperture (PAMELA) Optics Adjustment

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Scientists at Marshall's Adaptive Optics Lab demonstrate the Wave Front Sensor alignment using the Phased Array Mirror Extendible Large Aperture (PAMELA) optics adjustment. The primary objective of the PAMELA project is to develop methods for aligning and controlling adaptive optics segmented mirror systems. These systems can be used to acquire or project light energy. The Next Generation Space Telescope is an example of an energy acquisition system that will employ segmented mirrors. Light projection systems can also be used for power beaming and orbital debris removal. All segmented optical systems must be adjusted to provide maximum performance. PAMELA is an on going project that NASA is utilizing to investigate various methods for maximizing system performance.

  2. The modular design of large-aperture zoom system

    NASA Astrophysics Data System (ADS)

    Liu, Kai; Jiang, Kai; Yan, Peipei; Shan, Qiu-sha; Duan, Jing; Li, Gang

    2016-10-01

    According to the large aperture, long focal length zoom system design, the structure of the optical system based on the modular concept is proposed. The structure is constituted of an afocal compression telescope and a zoom system. The parts of each other are individually designed. The aberrations of them are independently. Because of this, the alignment of the system and the difficulty of test are greatly reduced. It is easily replaced by changing the zoom system parts, which can achieve other different focal length and ratio. Using afocal compression telescope greatly reduces the radial aperture of the zoom group, simplifies the system structure and reduces the cost. Meanwhile, the variable stop is placed in the vicinity of the primary mirror. It is instead of the zoom system used in floating variable stop. In addition, the problem about large aperture zoom system pupil matching is solved perfectly. In this article, four methods of pupil matching are given and the advantages and disadvantages of them are analyzed. Using this optical structure, a zoom system is designed, which is working in the visible wavelength band with variable focal length between 900mm and 4500mm, 500mm maximum aperture. The axial dimension of the system is less than 650mm. The maximum diameter of zoom system parts is less than 40 mm. Moreover, the distances of the zoom group and compensating group are all less than 60 mm. Besides, the motion curves of each other are given in the article. The Modulation Transfer Function (MTF) values of the system are greater than 0.3 at 48lp/mm across different focal length and field pointing on the axis. The design results show that the imaging quality is excellent, the structure is compact, and the alignment and test are easy. The imaging requirements of zoom system are all satisfied.

  3. Factors affecting the performance of large-aperture microphone arrays.

    PubMed

    Silverman, Harvey F; Patterson, William R; Sachar, Joshua

    2002-05-01

    Large arrays of microphones have been proposed and studied as a possible means of acquiring data in offices, conference rooms, and auditoria without requiring close-talking microphones. When such an array essentially surrounds all possible sources, it is said to have a large aperture. Large-aperture arrays have attractive properties of spatial resolution and signal-to-noise enhancement. This paper presents a careful comparison of theoretical and measured performance for an array of 256 microphones using simple delay-and-sum beamforming. This is the largest currently functional, all digital-signal-processing array that we know of. The array is wall-mounted in the moderately adverse environment of a general-purpose laboratory (8 m x 8 m x 3 m). The room has a T60 reverberation time of 550 ms. Reverberation effects in this room severely impact the array's performance. However, the width of the main lobe remains comparable to that of a simplified prediction. Broadband spatial resolution shows a single central peak with 10 dB gain about 0.4 m in diameter at the -3 dB level. Away from that peak, the response is approximately flat over most of the room. Optimal weighting for signal-to-noise enhancement degrades the spatial resolution minimally. Experimentally, we verify that signal-to-noise gain is less than proportional to the square root of the number of microphones probably due to the partial correlation of the noise between channels, to variation of signal intensity with polar angle about the source, and to imperfect correlation of the signal over the array caused by reverberations. We show measurements of the relative importance of each effect in our environment.

  4. Factors affecting the performance of large-aperture microphone arrays

    NASA Astrophysics Data System (ADS)

    Silverman, Harvey F.; Patterson, William R.; Sachar, Joshua

    2002-05-01

    Large arrays of microphones have been proposed and studied as a possible means of acquiring data in offices, conference rooms, and auditoria without requiring close-talking microphones. When such an array essentially surrounds all possible sources, it is said to have a large aperture. Large-aperture arrays have attractive properties of spatial resolution and signal-to-noise enhancement. This paper presents a careful comparison of theoretical and measured performance for an array of 256 microphones using simple delay-and-sum beamforming. This is the largest currently functional, all digital-signal-processing array that we know of. The array is wall-mounted in the moderately adverse environment of a general-purpose laboratory (8 m×8 m×3 m). The room has a T60 reverberation time of 550 ms. Reverberation effects in this room severely impact the array's performance. However, the width of the main lobe remains comparable to that of a simplified prediction. Broadband spatial resolution shows a single central peak with 10 dB gain about 0.4 m in diameter at the -3 dB level. Away from that peak, the response is approximately flat over most of the room. Optimal weighting for signal-to-noise enhancement degrades the spatial resolution minimally. Experimentally, we verify that signal-to-noise gain is less than proportional to the square root of the number of microphones probably due to the partial correlation of the noise between channels, to variation of signal intensity with polar angle about the source, and to imperfect correlation of the signal over the array caused by reverberations. We show measurements of the relative importance of each effect in our environment.

  5. BLAST: The Balloon-Borne Large Aperture Submillimeter Telescope

    NASA Technical Reports Server (NTRS)

    Devlin, Mark; Ade, Peter; Bock, Jamie; Dicker, Simon; Griffin, Matt; Gunderson, Josh; Halpern, Mark; Hargrave, Peter; Hughes, David; Klein, Jeff

    2004-01-01

    BLAST is the Balloon-borne Large-Aperture Sub-millimeter Telescope. It will fly from a Long Duration Balloon (LDB) platform from Antarctica. The telescope design incorporates a 2 m primary mirror with large-format bolometer arrays operating at 250, 350 and 500 microns. By providing the first sensitive large-area (10 sq. deg.) sub-mm surveys at these wavelengths, BLAST will address some of the most important galactic and cosmological questions regarding the formation and evolution of stars, galaxies and clusters. Galactic and extragalactic BLAST surveys will: (1) identify large numbers of high-redshift galaxies; (2) measure photometric redshifts, rest-frame FIR luminosities and star formation rates thereby constraining the evolutionary history of the galaxies that produce the FIR and sub-mm background; (3) measure cold pre-stellar sources associated with the earliest stages of star and planet formation; (4) make high-resolution maps of diffuse galactic emission over a wide range of galactic latitudes. In addition to achieving the above scientific goals, the exciting legacy of the BLAST LDB experiment will be a catalogue of 3000-5000 extragalactic sub-mm sources and a 100 sq. deg. sub-mm galactic plane survey. Multi-frequency follow-up observations from SIRTF, ASTRO-F, and Herschel, together with spectroscopic observations and sub-arcsecond imaging from ALMA are essential to understand the physical nature of the BLAST sources.

  6. Error analysis of large aperture static interference imaging spectrometer

    NASA Astrophysics Data System (ADS)

    Li, Fan; Zhang, Guo

    2015-12-01

    Large Aperture Static Interference Imaging Spectrometer is a new type of spectrometer with light structure, high spectral linearity, high luminous flux and wide spectral range, etc ,which overcomes the contradiction between high flux and high stability so that enables important values in science studies and applications. However, there're different error laws in imaging process of LASIS due to its different imaging style from traditional imaging spectrometers, correspondingly, its data processing is complicated. In order to improve accuracy of spectrum detection and serve for quantitative analysis and monitoring of topographical surface feature, the error law of LASIS imaging is supposed to be learned. In this paper, the LASIS errors are classified as interferogram error, radiometric correction error and spectral inversion error, and each type of error is analyzed and studied. Finally, a case study of Yaogan-14 is proposed, in which the interferogram error of LASIS by time and space combined modulation is mainly experimented and analyzed, as well as the errors from process of radiometric correction and spectral inversion.

  7. Fabrication of large aperture SiC brazing mirror

    NASA Astrophysics Data System (ADS)

    Li, Ang; Wang, Peipei; Dong, Huiwen; Wang, Peng

    2016-10-01

    The SiC brazing mirror is the mirror whose blank is made by assembling together smaller SiC pieces with brazing technique. Using such kinds of joining techniques, people can manufacture large and complex SiC assemblies. The key technologies of fabricating and testing SiC brazing flat mirror especially for large aperture were studied. The SiC brazing flat mirror was ground by smart ultrasonic-milling machine, and then it was lapped by the lapping smart robot and measured by Coordinate Measuring Machine (CMM). After the PV of the surface below 4um, we did classic coarse polishing to the surface and studied the shape of the polishing tool which directly effects removal amount distribution. Finally, it was figured by the polishing smart robot and measured by Fizeau interferometer. We also studied the influence of machining path and removal functions of smart robots on the manufacturing results and discussed the use of abrasive in this process. At last, an example for fabricating and measuring a similar SiC brazing flat mirror with the aperture of 600 mm made by Shanghai Institute of Ceramics was given. The mirror blank consists of 6 SiC sectors and the surface was finally processed to a result of the Peak-to-Valley (PV) 150nm and Root Mean Square (RMS) 12nm.

  8. Low mass large aperture vacuum window development at CEBAF

    SciTech Connect

    Keppel, C.

    1995-04-01

    Large aperture low mass vacuum windows are being developed for the HMS (High Momentum Spectrometer) and SOS (Short Orbit Spectrometer) spectrometers in Hall C at CEBAF. Because multiple scattering degrades the performance of a spectrometer it is important that the volume be evacuated and that the entrance and exit windows be as low mass as possible. The material used for such windows must be thin and light enough so as to have minimum effect of the beam, and at the same time, be thick and strong enough to operate reliably and safely. To achieve these goals, composite vacuum windows have been constructed of a thin sheet of Mylar with a reinforcing fabric. Reinforcing fabrics such as Kevlar and Spectra are available with tensile strengths significantly greater than that of Mylar. A thin layer of Myler remains necessary since the fabrics cannot achieve any sort of vacuum seal. The design, fabrication, testing, and operating experience with such composite windows for the Hall C spectrometers will be discussed.

  9. A low-cost large-aperture optical receiver for remote sensing and imaging applications

    NASA Astrophysics Data System (ADS)

    Hanes, Stephen A.

    2003-03-01

    An inexpensive large aperture (10 m class) receiver for optical wavelength imaging and remote sensing applications is discussed. The design was developed for active (laser illumination) imaging of remote objects using pupil plane measurement techniques, where relatively low optical quality collecting elements can be used. The approach is also well suited for conventional imaging at lower resolutions when light collection capability is of primary importance. The approach relies on a large aperture heliostat consisting of an array of flat mirror segments, like those used in solar collector systems, to collect light from the region of interest. The heliostat segments are tilted in a manner to concentrate the light, by making the light from all segments overlap at a common point, resulting in a region of higher intensity about the size of a segment at the heliostat "focus". A smaller secondary collector, consisting of a concave mirror located at the overlap point, further concentrates the light and forms a pupil image of the heliostat. Additional optics near the pupil image collimate the light for efficient transmission though a narrow band interference filter used to reduce sky background, and focus the light onto a PMT, or other sensor, for detection. Several design approaches for the collimating optics are discussed as well as system performance and limitations.

  10. Hybrid Electrostatic/Flextensional Mirror for Lightweight, Large-Aperture, and Cryogenic Space Telescopes

    NASA Technical Reports Server (NTRS)

    Patrick, Brian; Moore, James; Hackenberger, Wesley; Jiang, Xiaoning

    2013-01-01

    A lightweight, cryogenically capable, scalable, deformable mirror has been developed for space telescopes. This innovation makes use of polymer-based membrane mirror technology to enable large-aperture mirrors that can be easily launched and deployed. The key component of this innovation is a lightweight, large-stroke, cryogenic actuator array that combines the high degree of mirror figure control needed with a large actuator influence function. The latter aspect of the innovation allows membrane mirror figure correction with a relatively low actuator density, preserving the lightweight attributes of the system. The principal components of this technology are lightweight, low-profile, high-stroke, cryogenic-capable piezoelectric actuators based on PMN-PT (piezoelectric lead magnesium niobate-lead titanate) single-crystal configured in a flextensional actuator format; high-quality, low-thermal-expansion polymer membrane mirror materials developed by NeXolve; and electrostatic coupling between the membrane mirror and the piezoelectric actuator assembly to minimize problems such as actuator print-through.

  11. NST: Thermal Modeling for a Large Aperture Solar Telescope

    NASA Astrophysics Data System (ADS)

    Coulter, Roy

    2011-05-01

    Late in the 1990s the Dutch Open Telescope demonstrated that internal seeing in open, large aperture solar telescopes can be controlled by flushing air across the primary mirror and other telescope structures exposed to sunlight. In that system natural wind provides a uniform air temperature throughout the imaging volume, while efficiently sweeping heated air away from the optics and mechanical structure. Big Bear Solar Observatory's New Solar Telescope (NST) was designed to realize that same performance in an enclosed system by using both natural wind through the dome and forced air circulation around the primary mirror to provide the uniform air temperatures required within the telescope volume. The NST is housed in a conventional, ventilated dome with a circular opening, in place of the standard dome slit, that allows sunlight to fall only on an aperture stop and the primary mirror. The primary mirror is housed deep inside a cylindrical cell with only minimal openings in the side at the level of the mirror. To date, the forced air and cooling systems designed for the NST primary mirror have not been implemented, yet the telescope regularly produces solar images indicative of the absence of mirror seeing. Computational Fluid Dynamics (CFD) analysis of the NST primary mirror system along with measurements of air flows within the dome, around the telescope structure, and internal to the mirror cell are used to explain the origin of this seemingly incongruent result. The CFD analysis is also extended to hypothetical systems of various scales. We will discuss the results of these investigations.

  12. The Balloon-borne Large Aperture Submillimeter Telescope: BLAST

    NASA Astrophysics Data System (ADS)

    Truch, Matthew D. P.; Ade, P. A. R.; Bock, J. J.; Chapin, E. L.; Chung, J.; Devlin, M. J.; Dicker, S.; Griffin, M.; Gundersen, J. O.; Halpern, M.; Hargrave, P. C.; Hughes, D. H.; Klein, J.; MacTavish, C. J.; Marsden, G.; Martin, P. G.; Martin, T. G.; Mauskopf, P.; Netterfield, C. B.; Olmi, L.; Pascale, E.; Patanchon, G.; Rex, M.; Scott, D.; Semisch, C.; Thomas, N. E.; Tucker, C.; Tucker, G. S.; Viero, M. P.; Wiebe, D. V.

    2009-01-01

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a suborbital surveying experiment designed to study the evolutionary history and processes of star formation in local galaxies (including the Milky Way) and galaxies at cosmological distances. The BLAST continuum camera, which consists of 270 detectors distributed between three arrays, observes simultaneously in broadband (30%) spectral windows at 250, 350, and 500 microns. The optical design is based on a 2 m diameter telescope, providing a diffraction-limited resolution of 30" at 250 microns. The gondola pointing system enables raster mapping of arbitrary geometry, with a repeatable positional accuracy of 30"; postflight pointing reconstruction to <5" rms is achieved. The onboard telescope control software permits autonomous execution of a preselected set of maps, with the option of manual override. On this poster, we describe the primary characteristics and measured in-flight performance of BLAST. BLAST performed a test flight in 2003 and has since made two scientifically productive long-duration balloon flights: a 100 hour flight from ESRANGE (Kiruna), Sweden to Victoria Island, northern Canada in 2005 June; and a 250 hour, circumpolar flight from McMurdo Station, Antarctica in 2006 December. The BLAST collaboration acknowledges the support of NASA through grants NAG5-12785, NAG5-13301, and NNGO-6GI11G, the Canadian Space Agency (CSA), the Science and Technology Facilities Council (STFC), Canada's Natural Sciences and Engineering Research Council (NSERC), the Canada Foundation for Innovation, the Ontario Innovation Trust, the Puerto Rico Space Grant Consortium, the Fondo Institucional para la Investigacion of the University of Puerto Rico, and the National Science Foundation Office of Polar Programs.

  13. BLAST: A balloon-borne, large-aperture, submillimetre telescope

    NASA Astrophysics Data System (ADS)

    Wiebe, Donald Victor

    BLAST is a balloon-borne large-aperture, submillimetre telescope, which makes large area (1--200 square degree) surveys of Galactic and extragalactic targets. Since BLAST observes in the stratosphere, it is able to make broad-band observations between 200 mum and 550 mum which are difficult or impossible to perform from the ground. BLAST has been designed to probe star formation both in the local Galaxy and in the high redshift (z = 1--4) universe. Because BLAST is flown on an unmanned stratospheric balloon platform, it has been designed to be able to operate autonomously, without needing operator intervention to perform its scientific goals. This thesis includes an overview of the design of the BLAST platform, with emphasis on the command and control systems used to operate the telescope. BLAST has been flown on two long-duration balloon flights. The first of these, from Esrange, Sweden in June of 2005, acquired ˜70 hours of primarily Galactic data. During the second flight, from Willy Field, Antarctica in December of 2006, BLAST acquired ˜225 hours of both Galactic and extragalactic data. Operational performance of the platform during these two flights is reviewed, with the goal of providing insight on how future flights can be improved. Reduction of the data acquired by these large-format bolometer arrays is a challenging procedure, and techniques developed for BLAST data reduction are reviewed. The ultimate goal of this reduction is the generation of high quality astronomical maps which can be used for subsequent portions of data analysis. This thesis treats, in detail, the iterative, maximum likelihood map maker developed for BLAST. Results of simulations performed on the map maker to characterise its ability to reconstruct astronomical signals are presented. Finally, astronomical maps produced by this map maker using real data acquired by BLAST are presented, with a discussion on non-physical map pathologies resulting from the data reduction pipeline and

  14. Experimental instrumentation system for the Phased Array Mirror Extendible Large Aperture (PAMELA) test program

    NASA Technical Reports Server (NTRS)

    Boykin, William H., Jr.

    1993-01-01

    Adaptive optics are used in telescopes for both viewing objects with minimum distortion and for transmitting laser beams with minimum beam divergence and dance. In order to test concepts on a smaller scale, NASA MSFC is in the process of setting up an adaptive optics test facility with precision (fraction of wavelengths) measurement equipment. The initial system under test is the adaptive optical telescope called PAMELA (Phased Array Mirror Extendible Large Aperture). Goals of this test are: assessment of test hardware specifications for PAMELA application and the determination of the sensitivities of instruments for measuring PAMELA (and other adaptive optical telescopes) imperfections; evaluation of the PAMELA system integration effort and test progress and recommended actions to enhance these activities; and development of concepts and prototypes of experimental apparatuses for PAMELA.

  15. Large aperture laser beam alignment system based on far field sampling technique

    NASA Astrophysics Data System (ADS)

    Zhang, J. C.; Liu, D. Z.; Ouyang, X. P.; Kang, J.; Xie, X. L.; Zhou, J.; Gong, L.; Zhu, B. Q.

    2016-11-01

    Laser beam alignment is very important for high-power laser facility. Long laser path and large-aperture lens for alignment are generally used, while the proposed alignment system with a wedge by far-field sampling technique reduces both space and cost requirements. General alignment system for large-aperture laser beam is long in distance and large in volum because of taking near-field sampling technique. With the development of laser fusion facilities, the space for alignment system is limited. A new alignment system for large-aperture laser beam is designed to save space and reduce operating costs. The new alignment for large-aperture laser beam with a wedge is based on far-field sampling technique. The wedge is placed behind the spatial filter to reflect some laser beam as signal light for alignment. Therefore, laser beam diameter in alignment system is small, which can save space for the laser facility. Comparing to general alignment system for large-aperture laser beam, large-aperture lenses for near-field and far-field sampling, long distance laser path are unnecessary for proposed alignment system, which saves cost and space greatly. This alignment system for large-aperture laser beam has been demonstrated well on the Muliti-PW Facility which uses the 7th beam of the SG-Ⅱ Facility as pump source. The experimental results indicate that the average near-field alignment error is less than 1% of reference, and the average far-filed alignment error is less than 5% of spatial filter pinhole diameter, which meet the alignment system requirements for laser beam of Multi-PW Facility.

  16. APPLICATION OF LARGE APERTURE EMATS TO WELD INSPECTION

    SciTech Connect

    Maclauchlan, D. T.; Clark, S. P.; Hancock, J. W.

    2008-02-28

    One of the most significant developments in EMAT operation is the incorporation of phased array techniques. Phased array EMATs enable electronic beam steering and focusing while operating with temporally short pulses for good range resolution. Using phased array EMAT operation, multiple high powered pulsers are combined in the generation of the ultrasonic wave and multiple elements are combined in the reception of the ultrasonic wave, for improved sensitivity. EMATs make it practical to operate with shear horizontal (SH) waves and scan over a metal part's surface. An EMAT generated line force at the surface launches shear horizontal waves with uniform amplitude for beam angles from -90 deg. to 90 deg. Shear horizontal waves also reflect without mode conversion from surfaces that are parallel to the polarization of the shear wave displacements. The combination of these advantages makes phased array EMATs well suited for weld inspection. Recently, BWXT Services has developed a 32 active channel EMAT phased array system for operation up to 5 MHz. In addition, each element can be constructed with several sub-elements, alternating in polarity, to effectively multiply the number of active elements for a restricted range of beam angles. For example by using elements comprised of 4 sub elements, a 128 active element aperture designed for operation with a nominal 60 deg. beam angle provides good beam steering and focusing performance for 45 deg. to 70 deg. beam angles. The large active apertures allow the use of highly focused beams for good defect detection and high resolution imaging of weld defects. Application of this system to weld inspections has verified that good defect detection and imaging is possible. In addition, operation with SH waves has proven to provide improved detection of lack of fusion at the cap and root of the weld for certain weld geometries. The system has also been used to demonstrate the inspection of submerged metal arc welds while welding.

  17. Structural Feasibility Analysis of a Robotically Assembled Very Large Aperture Optical Space Telescope

    NASA Technical Reports Server (NTRS)

    Wilkie, William Keats; Williams, R. Brett; Agnes, Gregory S.; Wilcox, Brian H.

    2007-01-01

    This paper presents a feasibility study of robotically constructing a very large aperture optical space telescope on-orbit. Since the largest engineering challenges are likely to reside in the design and assembly of the 150-m diameter primary reflector, this preliminary study focuses on this component. The same technology developed for construction of the primary would then be readily used for the smaller optical structures (secondary, tertiary, etc.). A reasonable set of ground and on-orbit loading scenarios are compiled from the literature and used to define the structural performance requirements and size the primary reflector. A surface precision analysis shows that active adjustment of the primary structure is required in order to meet stringent optical surface requirements. Two potential actuation strategies are discussed along with potential actuation devices at the current state of the art. The finding of this research effort indicate that successful technology development combined with further analysis will likely enable such a telescope to be built in the future.

  18. Technology gap assessment for a future large-aperture ultraviolet-optical-infrared space telescope

    NASA Astrophysics Data System (ADS)

    Bolcar, Matthew R.; Balasubramanian, Kunjithapatham; Crooke, Julie; Feinberg, Lee; Quijada, Manuel; Rauscher, Bernard J.; Redding, David; Rioux, Norman; Shaklan, Stuart; Stahl, H. Philip; Stahle, Carl M.; Thronson, Harley

    2016-10-01

    The Advanced Technology Large Aperture Space Telescope (ATLAST) team identified five key technology areas to enable candidate architectures for a future large-aperture ultraviolet/optical/infrared (LUVOIR) space observatory envisioned by the NASA Astrophysics 30-year roadmap, "Enduring Quests, Daring Visions." The science goals of ATLAST address a broad range of astrophysical questions from early galaxy and star formation to the processes that contributed to the formation of life on Earth, combining general astrophysics with direct-imaging and spectroscopy of habitable exoplanets. The key technology areas are internal coronagraphs, starshades (or external occulters), ultra-stable large-aperture telescope systems, detectors, and mirror coatings. For each technology area, we define best estimates of required capabilities, current state-of-the-art performance, and current technology readiness level (TRL), thus identifying the current technology gap. We also report on current, planned, or recommended efforts to develop each technology to TRL 5.

  19. MICRONERVA: A Novel Approach to Large Aperture Astronomical Spectroscopy

    NASA Astrophysics Data System (ADS)

    Hall, Ryan; Plavchan, Peter; Geneser, Claire; Giddens, Frank; Spangler, Sophia

    2016-06-01

    MICRONERVA (MICRO Novel Exoplanet Radial Velocity Array) is a project to measure precise spectroscopic radial velocities. The cost of telescopes are a strong function of diameter, and light gathering power as opposed to angular resolution is the fundamental driver for telescope design for many spectroscopic science applications. By sacrificing angular resolution, many multiple smaller fiber-fed telescopes can be combined to synthesize the light gathering power of a larger diameter telescope at a lower effective cost. For our MICRONERVA prototype, based upon the larger MINERVA project, we will attempt to demonstrate that an array of four 8-inch CPC Celestron telescopes can be automated with sufficient active guiding precision for robust nightly robotic operations. The light from each telescope is coupled into single mode fibers, which are conveniently matched to the point spread function of 8-inch telescopes, which can be diffraction limited at red wavelengths in typical seeing at good observing sites. Additionally, the output from an array of single mode fibers provides stable output illumination of a spectrograph, which is a critical requirement of future precise radial velocity instrumentation. All of the hardware from the system is automated using Python programs and ASCOM and MaxIm DL software drivers. We will present an overview of the current status of the project and plans for future work. The detection of exoplanets using the techniques of MICRONERVA could potentially enable cost reductions for many types of spectroscopic research.

  20. Study on fine annealing process of the large-aperture K9 glasses

    NASA Astrophysics Data System (ADS)

    Gang, Wang; Bin, Liu Yi; Zheng, Li Li; Hui, Zhang; Lei, Xie; Min, Qiu Fu; Ping, Ma; Yao, Yan Ding

    2016-10-01

    Study on fine annealing process of the large-aperture K9 glasses was carried out in the report. The process parameters of glass placed way, fan speed and design of the cavity for keeping temperature uniformity were attained. By the fine annealing experiment, the stress distribution was improved evidently. The stress changed from Irregular distribution to consistency symmetric distribution and the stress max was reduced. The surface profile accuracy of the large-aperture K9 glasses was controlled steadily during CNC polishing.

  1. Off-axis multipass amplifier as a large aperture driver stage for fusion lasers.

    PubMed

    Murray, J E; Downs, D C; Hunt, J T; Hermes, G L; Warren, W E

    1981-03-01

    A multipass amplifier configuration is described which has potential as a large aperture, high gain driver stage for fusion laser systems. We avoid the present limitations of large aperture switches by using an off-angle geometry that does not require an optical switch. The saturated gain characteristics of this multipass amplifier are optimized numerically. Three potential problems are investigated experimentally, self-lasing, output beam quality, and amplified spontaneous emission output. The results indicate comparable cost for comparable performance to a linear chain, with some operational advantage for the multipass driver stage.

  2. Sub-aperture stitching test of a cylindrical mirror with large aperture

    NASA Astrophysics Data System (ADS)

    Xue, Shuai; Chen, Shanyong; Shi, Feng; Lu, Jinfeng

    2016-09-01

    Cylindrical mirrors are key optics of high-end equipment of national defense and scientific research such as high energy laser weapons, synchrotron radiation system, etc. However, its surface error test technology develops slowly. As a result, its optical processing quality can not meet the requirements, and the developing of the associated equipment is hindered. Computer Generated-Hologram (CGH) is commonly utilized as null for testing cylindrical optics. However, since the fabrication process of CGH with large aperture is not sophisticated yet, the null test of cylindrical optics with large aperture is limited by the aperture of the CGH. Hence CGH null test combined with sub-aperture stitching method is proposed to break the limit of the aperture of CGH for testing cylindrical optics, and the design of CGH for testing cylindrical surfaces is analyzed. Besides, the misalignment aberration of cylindrical surfaces is different from that of the rotational symmetric surfaces since the special shape of cylindrical surfaces, and the existing stitching algorithm of rotational symmetric surfaces can not meet the requirements of stitching cylindrical surfaces. We therefore analyze the misalignment aberrations of cylindrical surfaces, and study the stitching algorithm for measuring cylindrical optics with large aperture. Finally we test a cylindrical mirror with large aperture to verify the validity of the proposed method.

  3. Active membrane phased array radar

    NASA Technical Reports Server (NTRS)

    Moussessian, Alina; Del Castillo, Linda; Huang, John; Sadowy, Greg; Hoffman, James; Smith, Phil; Hatake, Toshiro; Derksen, Chuck; Lopez, Bernardo; Caro, Ed

    2005-01-01

    We have developed the first membrane-based active phased array in L-band (1.26GHz). The array uses membrane compatible Transmit/Receive (T/R) modules (membrane T/R) for each antenna element. We use phase shifters within each T/R module for electronic beam steering. We will discuss the T/R module design and integration with the membrane, We will also present transmit and receive beam-steering results for the array.

  4. Thermal Analysis of the Advanced Technology Large Aperture Space Telescope (ATLAST) 8 Meter Primary Mirror

    NASA Technical Reports Server (NTRS)

    Hornsby, Linda; Stahl, H. Philip; Hopkins, Randall C.

    2010-01-01

    The Advanced Technology Large Aperture Space Telescope (ATLAST) preliminary design concept consists of an 8 meter diameter monolithic primary mirror enclosed in an insulated, optical tube with stray light baffles and a sunshade. ATLAST will be placed in orbit about the Sun-Earth L2 and will experience constant exposure to the sun. The insulation on the optical tube and sunshade serve to cold bias the telescope which helps to minimize thermal gradients. The primary mirror will be maintained at 280K with an active thermal control system. The geometric model of the primary mirror, optical tube, sun baffles, and sunshade was developed using Thermal Desktop(R) SINDA/FLUINT(R) was used for the thermal analysis and the radiation environment was analyzed using RADCAD(R). A XX node model was executed in order to characterize the static performance and thermal stability of the mirror during maneuvers. This is important because long exposure observations, such as extra-solar terrestrial planet finding and characterization, require a very stable observatory wave front. Steady state thermal analyses served to predict mirror temperatures for several different sun angles. Transient analyses were performed in order to predict thermal time constant of the primary mirror for a 20 degree slew or 30 degree roll maneuver. This paper describes the thermal model and provides details of the geometry, thermo-optical properties, and the environment which influences the thermal performance. All assumptions that were used in the analysis are also documented. Parametric analyses are summarized for design parameters including primary mirror coatings and sunshade configuration. Estimates of mirror heater power requirements are reported. The thermal model demonstrates results for the primary mirror heated from the back side and edges using a heater system with multiple independently controlled zones.

  5. ATLAST-9.2: A Deployable Large Aperture UVOIR Space Telescope

    NASA Technical Reports Server (NTRS)

    Oegerle, William R.; Feinberg, L.; Purves, L.; Hyde, T.; Thronson, H.; Townsend, J.; Postman, M.; Bolcar, M.; Budinoff, J.; Dean, B.; Clampin, N.; Ebbets, D.; Gong, Q.; Gull, T.; Howard, J.; Jones, A.; Lyon, R.; Pasquale, B.; Perrygo, C.; Smith, S.; Thompson, P.; Woodgate, B.

    2010-01-01

    We present the results of a study of a deployable version of the Advanced Technology Large Aperture Space Telescope (ATLAST) that could be launched on an Evolved Expendable Launch Vehicle (EELV). ATLAST is a concept for a next-generation UVOIR observatory to follow HST and JWST. The observatory retains significant heritage from JWST, thereby taking advantage of technologies and engineering already developed for that mission. At the same time, we have identified several design changes to the JWST architecture, some of which are required due to the demanding wavefront error requirements at visible wavelengths. The optical telescope assembly has a segmented 9.2-meter aperture and consists of 36 hexagonal glass mirrors, each of which is I.3l5m in size (flat-to-flat). The telescope can be folded to fit in the 6.5m fairing on the planned upgrade to the Delta-IV heavy launch vehicle. Near-real time wavefront sensing and control is performed on-board the telescope using stars in the field of view to deliver diffraction limited imaging performance at 500nm wavelength. The optical design of the telescope provides an 8x20 arcmin FOV in which 4-5 instruments can be accommodated, plus fine guidance and wavefront sensors. Unlike JWST, the OTA sits at the end of a multi-gimbaled arm, allowing pitch and roll motion, and is isolated from the sunshield and spacecraft bus by an active isolation system. Our design permits servicing in order to extend the life of the observatory.

  6. Enzymatically active ultrathin pepsin membranes.

    PubMed

    Raaijmakers, Michiel J T; Schmidt, Thomas; Barth, Monika; Tutus, Murat; Benes, Nieck E; Wessling, Matthias

    2015-05-11

    Enzymatically active proteins enable efficient and specific cleavage reactions of peptide bonds. Covalent coupling of the enzymes permits immobilization, which in turn reduces autolysis-induced deactivation. Ultrathin pepsin membranes were prepared by facile interfacial polycondensation of pepsin and trimesoyl chloride. The pepsin membrane allows for simultaneous enzymatic conversion and selective removal of digestion products. The large water fluxes through the membrane expedite the transport of large molecules through the pepsin layers. The presented method enables the large-scale production of ultrathin, cross-linked, enzymatically active membranes.

  7. The development of large-aperture test system of infrared camera and visible CCD camera

    NASA Astrophysics Data System (ADS)

    Li, Yingwen; Geng, Anbing; Wang, Bo; Wang, Haitao; Wu, Yanying

    2015-10-01

    Infrared camera and CCD camera dual-band imaging system is used in many equipment and application widely. If it is tested using the traditional infrared camera test system and visible CCD test system, 2 times of installation and alignment are needed in the test procedure. The large-aperture test system of infrared camera and visible CCD camera uses the common large-aperture reflection collimator, target wheel, frame-grabber, computer which reduces the cost and the time of installation and alignment. Multiple-frame averaging algorithm is used to reduce the influence of random noise. Athermal optical design is adopted to reduce the change of focal length location change of collimator when the environmental temperature is changing, and the image quality of the collimator of large field of view and test accuracy are also improved. Its performance is the same as that of the exotic congener and is much cheaper. It will have a good market.

  8. Initial Technology Assessment for the Large-Aperture UV-Optical-Infrared (LUVOIR) Mission Concept Study

    NASA Technical Reports Server (NTRS)

    Bolcar, Matthew R.; Feinberg, Lee; France, Kevin; Rauscher, Bernard J.; Redding, David; Schiminovich, David

    2016-01-01

    The NASA Astrophysics Division's 30-Year Roadmap prioritized a future large-aperture space telescope operating in the ultra-violet/optical/infrared wavelength regime. The Association of Universities for Research in Astronomy envisioned a similar observatory, the High Definition Space Telescope. And a multi-institution group also studied the Advanced Technology Large Aperture Space Telescope. In all three cases, a broad science case is outlined, combining general astrophysics with the search for biosignatures via direct-imaging and spectroscopic characterization of habitable exoplanets. We present an initial technology assessment that enables such an observatory that is currently being studied for the 2020 Decadal Survey by the Large UV/Optical/Infrared (LUVOIR) surveyor Science and Technology Definition Team. We present here the technology prioritization for the 2016 technology cycle and define the required technology capabilities and current state-of-the-art performance. Current, planned, and recommended technology development efforts are also reported.

  9. The Advanced Technology Large Aperture Space Telescope (ATLAST): Science Drivers and Technology Developments

    NASA Technical Reports Server (NTRS)

    Postman, Marc; Brown, Tom; Sembach, Kenneth; Giavalisco, Mauro; Traub, Wesley; Stapelfeldt, Karl; Calzetti, Daniela; Oegerle, William; Rich, R. Michael; Stahl, H. Phillip; Tumlinson, Jason; Mountain, Matt; Soummer, Remi; Hyde, Tupper

    2011-01-01

    The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a concept for an 8-meter to 16-meter UVOIR space observatory for launch in the 2025-2030 era. ATLAST will allow astronomers to answer fundamental questions at the forefront of modern astrophysics, including "Is there life elsewhere in the Galaxy?" We present a range of science drivers and the resulting performance requirements for ATLAST (8 to 16 milliarcsecond angular resolution, diffraction limited imaging at 0.5 m wavelength, minimum collecting area of 45 square meters, high sensitivity to light wavelengths from 0.1 m to 2.4 m, high stability in wavefront sensing and control). We also discuss the priorities for technology development needed to enable the construction of ATLAST for a cost that is comparable to current generation observatory-class space missions. Keywords: Advanced Technology Large-Aperture Space Telescope (ATLAST); ultraviolet/optical space telescopes; astrophysics; astrobiology; technology development.

  10. Optomechanical analysis of the flexure mounting configuration of large-aperture laser transport mirror

    NASA Astrophysics Data System (ADS)

    Zhang, Zheng; Quan, Xusong; Wang, Hui; Liu, Tianye; Xiong, Zhao; Yuan, Xiaodong; Rong, Yiming

    2017-02-01

    Motivated by the demand to minimize the mount-induced wavefront aberration of the large-aperture laser transport mirror, a low-stress flexure mounting configuration is proposed. Specific optomechanical analyses, including theoretical modeling, numerical analysis and field experiment, are presented. The mechanical properties of the flexure support were studied specifically. Besides, the relation between the mounting forces and the root-mean-square of the gradients (GRMS) value of the mirror surface is studied. Then, the appropriate value of the bolt preload is set to 500N, with which the GRMS value is just 5.35 nm/cm. The results indicate that the flexure mounting configuration is indeed a feasible and promising method to solve the mount-induced distortion problem of large-aperture optics.

  11. Initial technology assessment for the Large-Aperture UV-Optical-Infrared (LUVOIR) mission concept study

    NASA Astrophysics Data System (ADS)

    Bolcar, Matthew R.; Feinberg, Lee; France, Kevin; Rauscher, Bernard J.; Redding, David; Schiminovich, David

    2016-07-01

    The NASA Astrophysics Division's 30-Year Roadmap prioritized a future large-aperture space telescope operating in the ultra-violet/optical/infrared wavelength regime. The Association of Universities for Research in Astronomy envisioned a similar observatory, the High Definition Space Telescope. And a multi-institution group also studied the Advanced Technology Large Aperture Space Telescope. In all three cases, a broad science case is outlined, combining general astrophysics with the search for biosignatures via direct-imaging and spectroscopic characterization of habitable exoplanets. We present an initial technology assessment that enables such an observatory that is currently being studied for the 2020 Decadal Survey by the Large UV/Optical/Infrared (LUVOIR) surveyor Science and Technology Definition Team. We present here the technology prioritization for the 2016 technology cycle and define the required technology capabilities and current state-of-the-art performance. Current, planned, and recommended technology development efforts are also reported.

  12. Research and validation of key measurement technologies of large aperture optical elements

    NASA Astrophysics Data System (ADS)

    Guo, Renhui; Chen, Lei; Jiang, Chao; Cao, Hui; Zhang, Huiqin; Zhou, Binbin; Song, Le

    2015-07-01

    A lot of optical components with large aperture are employed in high-power solid-state laser driver. These optical components are with high requirement on the surface shape, optical homogeneity and stress distribution. In order to test these parameters, different types of interferometers, surface profilers and stress meters from different manufacturers are needed. But the problem is the products from different manufacturers may provide different test results. To solve the problem, the research and verification of the key measurement technologies of large aperture optical components are carried out in this paper. The absolute flatness and optical homogeneity measurement methods are analyzed. And the test results of different interferometric software are compared. The test results from different surface profilers and stress meters are also compared. The consistency and reliability of different test software are obtained with the comparing results, which will guide users to select a suitable product.

  13. A Large-Aperture Acoustic Array to Observe Oceanic Density Structure

    DTIC Science & Technology

    1975-12-01

    Subtitle) ._,,, , , : A ^ARGE-APERTURb ^ COUSTIC ARRAY TO ^OBSERVE OCEANIC DENSITY STRUCTURE t 7. AUTHORfj; G. Thomas/Kaye READ INSTRUCTIONS...o CO (M MARINE PHYSICAL LABORATORY of the Scripps Institution of Oceanography San Diego, California 92132 A LARGE APERTURE ACOUSTIC ARRAY TO...Contracts Contract Effective Date: Contract Expiration Date; Amount of Contract: Layered Inhomogeneities N00014-69- A -0200-6038 \\ 1 April 1972 Jiß

  14. Partial feedback unstable resonator on small scale supersonic large aperture chemical laser

    NASA Astrophysics Data System (ADS)

    Wang, Hongyan; Wang, Rui; Li, Lei

    2015-05-01

    There is always a challenge on large aperture medium power laser's resonator design, stable resonator would supports significant higher order transverse modes, folded and telescope stable resonator are too complex and not preferred by engineers, unstable resonator need rather large round trip gain to compensate its high geometric out-coupling, which is difficult for this kind of laser since its gain length is limited due to the power level and large aperture. Partial feedback unstable resonator had been proposed to tackle this difficulty since the early days of laser development, however, the debates of its effect never stopped even with those distinguished optical resonator scientists such as Siegman, Anan'ev, and Weber. Recently integrated partial feedback unstable resonator design had been successfully demonstrated on a medium size chemical oxygen iodine laser. In this paper, we carry this resonator configuration on a small scale discharge driven supersonic nozzle array Hydrogen Fluoride chemical laser, a typical large aperture short gain length device. With magnification equals 4/3, we successfully get ten Watts level ring beam output.

  15. Low-stress mounting configuration design for large aperture laser transport mirror

    NASA Astrophysics Data System (ADS)

    Zhang, Zheng; Quan, Xusong; Yao, Chao; Wang, Hui

    2016-10-01

    TM1-6S1 large aperture laser transport mirror is a crucial optical unit of high power solid-state laser in the Inertial Confinement Fusion (ICF) facility. This article focuses on the low-stress and precise mounting method of large-aperture mirror. Based on the engineering practice of SG-III, the state-of-the-art and key problems of current mounting configuration are clarified firstly. Subsequently, a brand new low-stress mounting configuration with flexure supports is proposed. Opto-mechanical model of the mirror under mounting force is built up with elastic mechanics theory. Further, numerical methods and field tests are employed to verify the favorable load uniform capacity and load adjust capacity of flexure supports. With FEM, the relation between the mounting force from new configuration and the mirror surface distortion (wavefront error) is clarified. The novel mounting method of large aperture optics could be not only used on this laser transport mirror, but also on the other transmission optics and large crystals in ICF facilities.

  16. Tracking marine mammals and ships with small and large-aperture hydrophone arrays

    NASA Astrophysics Data System (ADS)

    Gassmann, Martin

    Techniques for passive acoustic tracking in all three spatial dimensions of marine mammals and ships were developed for long-term acoustic datasets recorded continuously over months using custom-designed arrays of underwater microphones (hydrophones) with spacing ranging from meters to kilometers. From the three-dimensional tracks, the acoustical properties of toothed whales and ships, such as sound intensity and directionality, were estimated as they are needed for the passive acoustic abundance estimation of toothed whales and for a quantitative description of the contribution of ships to the underwater soundscape. In addition, the tracks of the toothed whales reveal their underwater movements and demonstrate the potential of the developed tracking techniques to investigate their natural behavior and responses to sound generated by human activity, such as from ships or military SONAR. To track the periodically emitted echolocation sounds of toothed whales in an acoustically refractive environment in the upper ocean, a propagation-model based technique was developed for a hydrophone array consisting of one vertical and two L-shaped subarrays deployed from the floating instrument platform R/P FLIP. The technique is illustrated by tracking a group of five shallow-diving killer whales showing coordinated behavior. The challenge of tracking the highly directional echolocation sounds of deep-diving (< 1 km) toothed whales, in particular Cuvier's beaked whales, was addressed by embedding volumetric small-aperture (≈ 1 m element spacing) arrays into a large-aperture (≈ 1 km element spacing) seafloor array to reduce the minimum number of required receivers from five to two. The capabilities of this technique are illustrated by tracking several groups of up to three individuals over time periods from 10 min to 33 min within an area of 20 km2 in the Southern California Bight. To track and measure the underwater radiated sound of ships, a frequency domain beamformer was

  17. A Large Aperture Lidar Observatory for Exploring the Interaction of Our Atmosphere with Space (Invited)

    NASA Astrophysics Data System (ADS)

    Thayer, J. P.; Gardner, C. S.; Swenson, G. R.

    2013-12-01

    The mesopause region has been the subject of intensive study during the past decade because it is recognized as a critical region connecting our sensible atmosphere to the near-space environment. Processes in this region include a host of wave dynamics, heat and constituent transport, turbulence, polar mesospheric cloud formation, and the influx of meteoric material. Moreover, the neutral gas properties above the mesopause from 100 - 200 km altitude are poorly characterized and are influenced by additional processes that include solar EUV absorption / ionization, eddy to molecular diffusion, neutral wind dynamo action, and geomagnetic activity. Thus, this altitude region is a complex confluence of space and atmosphere processes that ultimately determine its properties. Fundamentally these processes are operating in any planetary atmosphere and must be understood in order to advance understanding of habitability and sustainability of a planetary system. While observational and modeling capabilities are evolving, progress in characterizing neutral properties and related processes in the mesopause region and above has been inhibited because they cannot be observed in sufficient detail and at high enough altitudes with existing instrumentation. This is especially true of the neutral atmosphere from 50 - 1000 km, where observations of its properties, dynamics and thermal structure are either sparse or nonexistent. A Large-Aperture Lidar Observatory (LALO) would enable significant progress by providing critical measurements of atmospheric constituents and parameters at greatly enhanced resolution and at much higher altitudes than is possible today. A large telescope in combination with modern high-power lasers, would enable observations of the neutral atmosphere to 1000 km altitude with a sensitivity and resolution approximately 1000 times better than can be achieved with the most powerful lidar systems in operation today. There are no technology barriers to realizing

  18. An Engineering Design Reference Mission for a Future Large-Aperture UVOIR Space Observatory

    NASA Astrophysics Data System (ADS)

    Thronson, Harley A.; Bolcar, Matthew R.; Clampin, Mark; Crooke, Julie A.; Redding, David; Rioux, Norman; Stahl, H. Philip

    2016-01-01

    From the 2010 NRC Decadal Survey and the NASA Thirty-Year Roadmap, Enduring Quests, Daring Visions, to the recent AURA report, From Cosmic Birth to Living Earths, multiple community assessments have recommended development of a large-aperture UVOIR space observatory capable of achieving a broad range of compelling scientific goals. Of these priority science goals, the most technically challenging is the search for spectroscopic biomarkers in the atmospheres of exoplanets in the solar neighborhood. Here we present an engineering design reference mission (EDRM) for the Advanced Technology Large-Aperture Space Telescope (ATLAST), which was conceived from the start as capable of breakthrough science paired with an emphasis on cost control and cost effectiveness. An EDRM allows the engineering design trade space to be explored in depth to determine what are the most demanding requirements and where there are opportunities for margin against requirements. Our joint NASA GSFC/JPL/MSFC/STScI study team has used community-provided science goals to derive mission needs, requirements, and candidate mission architectures for a future large-aperture, non-cryogenic UVOIR space observatory. The ATLAST observatory is designed to operate at a Sun-Earth L2 orbit, which provides a stable thermal environment and excellent field of regard. Our reference designs have emphasized a serviceable 36-segment 9.2 m aperture telescope that stows within a five-meter diameter launch vehicle fairing. As part of our cost-management effort, this particular reference mission builds upon the engineering design for JWST. Moreover, it is scalable to a variety of launch vehicle fairings. Performance needs developed under the study are traceable to a variety of additional reference designs, including options for a monolithic primary mirror.

  19. Large aperture interferometer with phase-conjugate self-reference beam

    NASA Technical Reports Server (NTRS)

    Howes, W. L.

    1986-01-01

    A large aperture self-referencing interferometer consisting of a Twyman-Green interferometer using a self-pumped phase conjugator in series with test section optics is described and experimentally demonstrated. This interferometer provides twice the fringe shift of a Mach-Zehnder (M-Z) interferometer for a given optical phase change induced within the test section. It also provides greater irradiance in the reference beam than does a similar series setup utilizing a M-Z interferometer incorporating a local reference beam. Whereas the ordinary interferometer records instantaneous conditions, the new one records overage conditions if a BaTiO3 crystal is used as the phase conjugator.

  20. Spacecraft Conceptual Design for the 8-Meter Advanced Technology Large Aperture Space Telescope (ATLAST)

    NASA Technical Reports Server (NTRS)

    Hopkins, Randall C.; Capizzo, Peter; Fincher, Sharon; Hornsby, Linda S.; Jones, David

    2010-01-01

    The Advanced Concepts Office at Marshall Space Flight Center completed a brief spacecraft design study for the 8-meter monolithic Advanced Technology Large Aperture Space Telescope (ATLAST-8m). This spacecraft concept provides all power, communication, telemetry, avionics, guidance and control, and thermal control for the observatory, and inserts the observatory into a halo orbit about the second Sun-Earth Lagrange point. The multidisciplinary design team created a simple spacecraft design that enables component and science instrument servicing, employs articulating solar panels for help with momentum management, and provides precise pointing control while at the same time fast slewing for the observatory.

  1. Development of an efficient large-aperture high damage-threshold sol-gel diffraction grating.

    SciTech Connect

    Ashley, Carol S.; Rambo, Patrick K.; Schwarz, Jens; Dunphy, Darren Robert; Branson, Eric D.; Smith, Ian Craig; Johnson, William Arthur; Reed, Scott T.; Cook, Adam W.

    2005-03-01

    In order to develop the next generation of high peak intensity lasers, new grating technology providing higher damage thresholds and large apertures is required. The current assumption is that this technical innovation will be multilayer dielectric gratings, wherein the uppermost layer of a thin film mirror is etched to create the desired binary phase grating. A variant of this is explored with the upper grating layer being a lower density gelatin-based volume phase grating in either sol-gel or dichromated gelatin. One key benefit is the elimination of the etching step.

  2. End-to-End Assessment of a Large Aperture Segmented Ultraviolet Optical Infrared (UVOIR) Telescope Architecture

    NASA Technical Reports Server (NTRS)

    Feinberg, Lee; Bolcar, Matt; Liu, Alice; Guyon, Olivier; Stark,Chris; Arenberg, Jon

    2016-01-01

    Key challenges of a future large aperture, segmented Ultraviolet Optical Infrared (UVOIR) Telescope capable of performing a spectroscopic survey of hundreds of Exoplanets will be sufficient stability to achieve 10-10 contrast measurements and sufficient throughput and sensitivity for high yield Exo-Earth spectroscopic detection. Our team has collectively assessed an optimized end to end architecture including a high throughput coronagraph capable of working with a segmented telescope, a cost-effective and heritage based stable segmented telescope, a control architecture that minimizes the amount of new technologies, and an Exo-Earth yield assessment to evaluate potential performance.

  3. Research on new-style flexure supports method for large-aperture transport mirror mounting

    NASA Astrophysics Data System (ADS)

    Quan, Xusong; Zhang, Zheng; Xiong, Zhao; Wang, Hui; Yuan, Xiaodong; Liu, Changchun

    2016-10-01

    In high-power solid-state laser facility (SG-III), focusing laser beams into the target center with precision better than 50 microns (RMS) is dependent on the stringent specifications of thousands of large-aperture transport mirror units and is a huge challenge on the surface aberration control of mirrors. The current mirror's mounting techniques with screw fastening loads has several engineering conundrums - low control precision for loads (higher scatter even +/-30%), and low assembly-rectification efficiency ( 100 screws). To improve the current screw-fastening method, a new-style flexure supports method, which has a wonderful performance on uniform control of the external loads and only uses 30 screws, is proposed to mount the mirror (size: 610mm×440mm×85mm). With theoretical modeling and FEM analysis, the impacts of mounting loads on mirror's surface aberrations are analyzed and discussed in detail, and the flexure supports system is designed. Finally, with experimental research and case studies, the proposed flexure supports method shows a powerful performance on even control precision of external loads with scatter even less than +/-10%, which is a promising mounting process to replace the threaded fasteners mounting the large-aperture optics. These improvements can lay a foundation for mounting process consistency, robustness, and assembly-rectification efficiency of large optical component.

  4. Designs for a large-aperture telescope to map the CMB 10× faster.

    PubMed

    Niemack, Michael D

    2016-03-01

    Current large-aperture cosmic microwave background (CMB) telescopes have nearly maximized the number of detectors that can be illuminated while maintaining diffraction-limited image quality. The polarization-sensitive detector arrays being deployed in these telescopes in the next few years will have roughly 10⁴ detectors. Increasing the mapping speed of future instruments by at least an order of magnitude is important to enable precise probes of the inflationary paradigm in the first fraction of a second after the big bang and provide strong constraints on cosmological parameters. The CMB community has begun planning a next generation "Stage IV" CMB project that will be comprised of multiple telescopes with between 10⁵-10⁶ detectors to pursue these goals. This paper introduces the new crossed Dragone telescope and receiver optics designs that increase the usable diffraction-limited field-of-view, and therefore the mapping speed, by an order of magnitude compared to the upcoming generation of large-aperture instruments. Polarization systematics and engineering considerations are presented, including a preliminary receiver model to demonstrate that these designs will enable high efficiency illumination of >10⁵ detectors in a next generation CMB telescope.

  5. Eyeglass Large Aperture, Lightweight Space Optics FY2000 - FY2002 LDRD Strategic Initiative

    SciTech Connect

    Hyde, R

    2003-02-10

    A series of studies by the Air Force, the National Reconnaissance Office and NASA have identified the critical role played by large optics in fulfilling many of the space related missions of these agencies. Whether it is the Next Generation Space Telescope for NASA, high resolution imaging systems for NRO, or beam weaponry for the Air Force, the diameter of the primary optic is central to achieving high resolution (imaging) or a small spot size on target (lethality). While the detailed requirements differ for each application (high resolution imaging over the visible and near-infrared for earth observation, high damage threshold but single-wavelength operation for directed energy), the challenges of a large, lightweight primary optic which is space compatible and operates with high efficiency are the same. The advantage of such large optics to national surveillance applications is that it permits these observations to be carried-out with much greater effectiveness than with smaller optics. For laser weapons, the advantage is that it permits more tightly focused beams which can be leveraged into either greater effective range, reduced laser power, and/or smaller on-target spot-sizes; weapon systems can be made either much more effective or much less expensive. This application requires only single-wavelength capability, but places an emphasis upon robust, rapidly targetable optics. The advantages of large aperture optics to astronomy are that it increases the sensitivity and resolution with which we can view the universe. This can be utilized either for general purpose astronomy, allowing us to examine greater numbers of objects in more detail and at greater range, or it can enable the direct detection and detailed examination of extra-solar planets. This application requires large apertures (for both light-gathering and resolution reasons), with broad-band spectral capability, but does not emphasize either large fields-of-view or pointing agility. Despite

  6. Recent Enhancements of the Phased Array Mirror Extendible Large Aperture (PAMELA) Telescope Testbed at MSFC

    NASA Technical Reports Server (NTRS)

    Rakoczy, John; Montgomery, Edward E.; Lindner, Jeff

    2000-01-01

    Recent incremental upgrades to the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope testbed have enabled the demonstration of phasing (with a monochromatic source) of clusters of primary mirror segments down to the diffraction limit. PAMELA upgrades include an improved Shack-Hartmann wavefront sensor, passive viscoelastic damping treatments for the voice-coil actuators, mechanical improvement of mirror surface figures, and optical bench baffling. This report summarizes the recent PAMELA upgrades, discusses the lessons learned, and presents a status of this unique testbed for wavefront sensing and control. The Marshall Space Flight Center acquired the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope in 1993 after Kaman Aerospace was unable to complete integration and testing under the limited SDIO and DARPA funding. The PAMELA is a 36-segment, half-meter aperture, adaptive telescope which utilizes a Shack-Hartmann wavefront sensor, inductive coil edge sensors, voice coil actuators, imaging CCD cameras and interferometry for figure alignment, wavefront sensing and control. MSFC originally obtained the PAMELA to supplement its research in the interactions of control systems with flexible structures. In August 1994, complete tip, tilt and piston control was successfully demonstrated using the Shack-Hartmann wavefront sensor and the inductive edge sensors.

  7. Recent Enhancements of the Phased Array Mirror Extendible Large Aperture (PAMELA) Telescope Testbed at MSFC

    NASA Technical Reports Server (NTRS)

    Rakoczy, John; Burdine, Robert (Technical Monitor)

    2001-01-01

    Recent incremental upgrades to the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope testbed have enabled the demonstration of phasing (with a monochromatic source) of clusters of primary mirror segments down to the diffraction limit. PAMELA upgrades include in improved Shack-Hartmann wavefront sensor, passive viscoelastic damping treatments for the voice-coil actuators, mechanical improvement of mirror surface figures, and optical bench baffling. This report summarizes the recent PAMELA upgrades, discusses the lessons learned, and presents a status of this unique testbed for wavefront sensing and control. The Marshall Space Flight Center acquired the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope in 1993 after Kaman Aerospace was unable to complete integration and testing under the limited SDIO and DARPA funding. The PAMELA is a 36-segment, half-meter aperture, adaptive telescope which utilizes a Shack-Hartmann wavefront sensor, inductive coil edge sensors, voice coil actuators, imaging CCD cameras and interferometry for figure alignment, wavefront sensing and control. MSFC originally obtained the PAMELA to supplement its research in the interactions of control systems with flexible structures. In August 1994, complete tip, tilt and piston control was successfully demonstrated using the Shack-Hartmann wavefront sensor and the inductive edge sensors.

  8. Study on supporting force sensing and control during large aperture space mirror test

    NASA Astrophysics Data System (ADS)

    Zhang, Long; Hu, Wenqi; Zheng, Liehua; Hao, Peiming

    2016-10-01

    During the machining of large aperture lightweight space mirror, the mirror figure consistency between ground test and space mission is a problem. In order to effectively control the supporting deformation effect on test results in gravity environment, in view of a 1.2-m space mirror with back blind holes, a supporting method for optical axis horizontal test is proposed, with this method, mirror under test is positioned by three center hole surfaces and supported by six external hole surfaces. The effect of deformation caused by different supporting force value, area and position is analyzed by finite element method, the simulation results show that this supporting method can control the mirror supporting deformation within PV0.035λ rms0.005λ. The actual supporting system uses soft expansion mandrel to control the mirror position and pneumatic lever to realize the floating support. In order to ensure that the support force can evenly distribute on the contact surface, a pressure mapping system is adopted to measure the interface pressure between the mirror blind holes and the soft supporting pads for the first time. This method can meet the test requirements of rms=1/40λ mirror and provides a technical support for high precision test of large aperture space mirror with back blind holes.

  9. Research on the support structure of the primary mirror of large-aperture telescope

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Zhang, Jingxu

    2007-12-01

    Large-aperture telescope can be used in surveying battlefield, researching landform, searching object, real-time monitoring, imaging, detecting and identifying spatial targets and so on. A large-aperture telescope for achieving high resolution power is designed to monitor spatial target and image in real time. Real-time monitoring plays an important role in military conflicts. The orbit parameter of object, quantity, geometrical shape parameter and so on can be obtained by detect spatial target. With the development of optical technology, people require larger aperture in optics-electronic (O-E) system. By increasing optical aperture, the ability of collecting light and resolution power in the system can be enhanced. But the support structure of the primary mirror of large-aperture telescope will be a very difficult problem. With the increase of primary mirror aperture, the weight of the primary mirror will become larger than before. The root mean square (rms) of the primary mirror is affected by many factors, such as deadweight, deformation of heat, environment and so on. Due to the primary mirror of telescope is an important component of telescope system. By reducing the weight of primary mirror, precision of the system is ensured. During the designing phase, one can consider the supporting project of the primary mirror synthetically and analyze it roundly according to technical requirement of optical system and the effect factors. The final structural design can be reasonable. In an astronomical telescope, the surface of reflector is an important part for collecting dark radiation of celestial bodies. Its surface shape will have an effect on collecting efficiency of telescope radiant energy directly. So the rms must be very high. Optical system of large aperture, small wavelength and small focus can receive maximal light intensity. For ground-based optical astronomical telescope, the design proposed in the paper can satisfy the requirement of the possible

  10. Active microrheology of smectic membranes.

    PubMed

    Qi, Zhiyuan; Ferguson, Kyle; Sechrest, Yancey; Munsat, Tobin; Park, Cheol Soo; Glaser, Matthew A; Maclennan, Joseph E; Clark, Noel A; Kuriabova, Tatiana; Powers, Thomas R

    2017-02-01

    Thin fluid membranes embedded in a bulk fluid of different viscosity are of fundamental interest as experimental realizations of quasi-two-dimensional fluids and as models of biological membranes. We have probed the hydrodynamics of thin fluid membranes by active microrheology using small tracer particles to observe the highly anisotropic flow fields generated around a rigid oscillating post inserted into a freely suspended smectic liquid crystal film that is surrounded by air. In general, at distances more than a few Saffman lengths from the meniscus around the post, the measured velocities are larger than the flow computed by modeling a moving disklike inclusion of finite extent by superposing Levine-MacKintosh response functions for pointlike inclusions in a viscous membrane. The observed discrepancy is attributed to additional coupling of the film with the air below the film that is displaced directly by the shaft of the moving post.

  11. Active microrheology of smectic membranes

    NASA Astrophysics Data System (ADS)

    Qi, Zhiyuan; Ferguson, Kyle; Sechrest, Yancey; Munsat, Tobin; Park, Cheol Soo; Glaser, Matthew A.; Maclennan, Joseph E.; Clark, Noel A.; Kuriabova, Tatiana; Powers, Thomas R.

    2017-02-01

    Thin fluid membranes embedded in a bulk fluid of different viscosity are of fundamental interest as experimental realizations of quasi-two-dimensional fluids and as models of biological membranes. We have probed the hydrodynamics of thin fluid membranes by active microrheology using small tracer particles to observe the highly anisotropic flow fields generated around a rigid oscillating post inserted into a freely suspended smectic liquid crystal film that is surrounded by air. In general, at distances more than a few Saffman lengths from the meniscus around the post, the measured velocities are larger than the flow computed by modeling a moving disklike inclusion of finite extent by superposing Levine-MacKintosh response functions for pointlike inclusions in a viscous membrane. The observed discrepancy is attributed to additional coupling of the film with the air below the film that is displaced directly by the shaft of the moving post.

  12. Modeling Electrically Active Viscoelastic Membranes

    PubMed Central

    Roy, Sitikantha; Brownell, William E.; Spector, Alexander A.

    2012-01-01

    The membrane protein prestin is native to the cochlear outer hair cell that is crucial to the ear's amplification and frequency selectivity throughout the whole acoustic frequency range. The outer hair cell exhibits interrelated dimensional changes, force generation, and electric charge transfer. Cells transfected with prestin acquire unique active properties similar to those in the native cell that have also been useful in understanding the process. Here we propose a model describing the major electromechanical features of such active membranes. The model derived from thermodynamic principles is in the form of integral relationships between the history of voltage and membrane resultants as independent variables and the charge density and strains as dependent variables. The proposed model is applied to the analysis of an active force produced by the outer hair cell in response to a harmonic electric field. Our analysis reveals the mechanism of the outer hair cell active (isometric) force having an almost constant amplitude and phase up to 80 kHz. We found that the frequency-invariance of the force is a result of interplay between the electrical filtering associated with prestin and power law viscoelasticity of the surrounding membrane. Paradoxically, the membrane viscoelasticity boosts the force balancing the electrical filtering effect. We also consider various modes of electromechanical coupling in membrane with prestin associated with mechanical perturbations in the cell. We consider pressure or strains applied step-wise or at a constant rate and compute the time course of the resulting electric charge. The results obtained here are important for the analysis of electromechanical properties of membranes, cells, and biological materials as well as for a better understanding of the mechanism of hearing and the role of the protein prestin in this mechanism. PMID:22701528

  13. A conceptual design of a large aperture microwave radiometer geostationary platform

    NASA Technical Reports Server (NTRS)

    Garn, Paul A.; Garrison, James L.; Jasinski, Rachel

    1992-01-01

    A conceptual design of a Large Aperture Microwave Radiometer (LAMR) Platform has been developed and technology areas essential to the design and on-orbit viability of the platform have been defined. Those technologies that must be developed to the requirement stated here for the LAMR mission to be viable include: advanced radiation resistant solar cells, integrated complex structures, large segmented reflector panels, sub 3 kg/m(exp 2) areal density large antennas, and electric propulsion systems. Technology areas that require further development to enhance the capabilities of the LAMR platform (but are not essential for viability) include: electrical power storage, on-orbit assembly, and on-orbit systems checkout and correction.

  14. Diffractive imaging analysis of large-aperture segmented telescope based on partial Fourier transform

    NASA Astrophysics Data System (ADS)

    Dong, Bing; Qin, Shun; Hu, Xinqi

    2013-09-01

    Large-aperture segmented primary mirror will be widely used in next-generation space-based and ground-based telescopes. The effects of intersegment gaps, obstructions, position and figure errors of segments, which are all involved in the pupil plane, on the image quality metric should be analyzed using diffractive imaging theory. Traditional Fast Fourier Transform (FFT) method is very time-consuming and costs a lot of memory especially in dealing with large pupil-sampling matrix. A Partial Fourier Transform (PFT) method is first proposed to substantially speed up the computation and reduce memory usage for diffractive imaging analysis. Diffraction effects of a 6-meter segmented mirror including 18 hexagonal segments are simulated and analyzed using PFT method. The influence of intersegment gaps and position errors of segments on Strehl ratio is quantitatively analyzed by computing the Point Spread Function (PSF). By comparing simulation results with theoretical results, the correctness and feasibility of PFT method is confirmed.

  15. THE BALLOON-BORNE LARGE APERTURE SUBMILLIMETER TELESCOPE (BLAST) 2006: CALIBRATION AND FLIGHT PERFORMANCE

    SciTech Connect

    Truch, Matthew D. P.; Devlin, Mark J.; Dicker, Simon R.; Klein, Jeff; Ade, Peter A. R.; Griffin, Matthew; Hargrave, Peter C.; Mauskopf, Philip; Moncelsi, Lorenzo; Pascale, Enzo; Bock, James J.; Chapin, Edward L.; Halpern, Mark; Marsden, Gaelen; Gundersen, Joshua O.; Hughes, David H.; Martin, Peter G.; Netterfield, C. Barth; Olmi, Luca; Patanchon, Guillaume

    2009-12-20

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) operated successfully during a 250 hr flight over Antarctica in 2006 December (BLAST06). As part of the calibration and pointing procedures, the red hypergiant star VY CMa was observed and used as the primary calibrator. Details of the overall BLAST06 calibration procedure are discussed. The 1sigma uncertainty on the absolute calibration is accurate to 9.5%, 8.7%, and 9.2% at the 250, 350, and 500 mum bands, respectively. The errors are highly correlated between bands resulting in much lower errors for the derived shape of the 250-500 mum continuum. The overall pointing error is < 5'' rms for the 36'', 42'', and 60'' beams. The performance of optics and pointing systems is discussed.

  16. End-to-end assessment of a large aperture segmented ultraviolet optical infrared (UVOIR) telescope architecture

    NASA Astrophysics Data System (ADS)

    Feinberg, Lee; Rioux, Norman; Bolcar, Matthew; Liu, Alice; Guyon, Olivier; Stark, Chris; Arenberg, Jon

    2016-07-01

    Key challenges of a future large aperture, segmented Ultraviolet Optical Infrared (UVOIR) Telescope capable of performing a spectroscopic survey of hundreds of Exoplanets will be sufficient stability to achieve 10^-10 contrast measurements and sufficient throughput and sensitivity for high yield exo-earth spectroscopic detection. Our team has collectively assessed an optimized end to end architecture including a high throughput coronagraph capable of working with a segmented telescope, a cost-effective and heritage based stable segmented telescope, a control architecture that minimizes the amount of new technologies, and an exo-earth yield assessment to evaluate potential performance. These efforts are combined through integrated modeling, coronagraph evaluations, and exo-earth yield calculations to assess the potential performance of the selected architecture. In addition, we discusses the scalability of this architecture to larger apertures and the technological tall poles to enabling these missions.

  17. End-to-End Assessment of a Large Aperture Segmented Ultraviolet Optical Infrared (UVOIR) Telescope Architecture

    NASA Technical Reports Server (NTRS)

    Feinberg, Lee; Rioux, Norman; Bolcar, Matthew; Liu, Alice; Guyon, Oliver; Stark, Chris; Arenberg, Jon

    2016-01-01

    Key challenges of a future large aperture, segmented Ultraviolet Optical Infrared (UVOIR) Telescope capable of performing a spectroscopic survey of hundreds of Exoplanets will be sufficient stability to achieve 10^-10 contrast measurements and sufficient throughput and sensitivity for high yield Exo-Earth spectroscopic detection. Our team has collectively assessed an optimized end to end architecture including a high throughput coronagraph capable of working with a segmented telescope, a cost-effective and heritage based stable segmented telescope, a control architecture that minimizes the amount of new technologies, and an Exo-Earth yield assessment to evaluate potential performance. These efforts are combined through integrated modeling, coronagraph evaluations, and Exo-Earth yield calculations to assess the potential performance of the selected architecture. In addition, we discusses the scalability of this architecture to larger apertures and the technological tall poles to enabling it.

  18. The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) 2005: Calibration and Targeted Sources

    NASA Astrophysics Data System (ADS)

    Truch, Matthew; BLAST Collaboration

    2007-12-01

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) operated successfully during a 100-hour flight from northern Sweden in June 2005 (BLAST05). As part of the calibration and pointing procedures, several compact sources were mapped, including solar system, Galactic, and extragalactic targets, specifically Pallas, CRL 2688, LDN 1014, IRAS 20126+4104, IRAS 21078+5211, IRAS 21307+5049, IRAS 22134+5834, IRAS 23011+6126, K3-50, W 75N, Mrk 231, NGC 4565, and Arp 220 (this last source being our primary calibrator). The BLAST observations of each compact source are described, flux densities and spectral energy distributions are reported, and these are compared with previous measurements at other wavelengths. BLAST was particularly useful for constraining the slope of the submillimeter continuum.

  19. Advanced Technology Large-Aperture Space Telescope: Science Drivers and Technology Developments

    NASA Technical Reports Server (NTRS)

    Postman, Marc; Brown, Tom; Sembach, Kenneth; Glavallsco, Mauro; Traub, Wesley; Stapelfeldt, Karl; Calzetti, Daniela; Oegerle, William; Rich, R. Michael; Stahl, H. Philip; Tumlinson, Jason; Mountain, Matt; Soummer, Remi; Hyde, Tupper

    2012-01-01

    The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a concept for an 8- to 16-m ultraviolet optical near Infrared space observatory for launch in the 2025 to 2030 era. ATLAST will allow astronomers to answer fundamental questions at the forefront of modern astrophysics, including: Is there life elsewhere in the Galaxy? We present a range of science drivers and the resulting performance requirements for ATLAST (8- to 16-marcsec angular resolution, diffraction limited imaging at 0.5 micron wavelength, minimum collecting area of 45 sq m, high sensitivity to light wavelengths from 0.1 to 2.4 micron, high stability in wavefront sensing and control). We also discuss the priorities for technology development needed to enable the construction of ATLAST for a cost that is comparable to that of current generation observatory-class space missions.

  20. Interference data correction methods for lunar observation with a large-aperture static imaging spectrometer.

    PubMed

    Zhang, Geng; Wang, Shuang; Li, Libo; Hu, Xiuqing; Hu, Bingliang

    2016-11-01

    The lunar spectrum has been used in radiometric calibration and sensor stability monitoring for spaceborne optical sensors. A ground-based large-aperture static image spectrometer (LASIS) can be used to acquire the lunar spectral image for lunar radiance model improvement when the moon orbits over its viewing field. The lunar orbiting behavior is not consistent with the desired scanning speed and direction of LASIS. To correctly extract interferograms from the obtained data, a translation correction method based on image correlation is proposed. This method registers the frames to a reference frame to reduce accumulative errors. Furthermore, we propose a circle-matching-based approach to achieve even higher accuracy during observation of the full moon. To demonstrate the effectiveness of our approaches, experiments are run on true lunar observation data. The results show that the proposed approaches outperform the state-of-the-art methods.

  1. The Balloon-borne Large Aperture Submillimetre Telescope (BLAST) and BLASTPol

    NASA Astrophysics Data System (ADS)

    Pascale, Enzo; Pascale

    2013-01-01

    Balloon observations from Antarctica have proven an effective and efficient way to address open Cosmological questions as well as problems in Galactic astronomy. The Balloon-borne Large Aperture Submillimetre Telescope (BLAST) is a sub-orbital mapping experiment which uses 270 bolometric detectors to image the sky in three wavebands centred at 250, 350 and 500 μm with a 1.8 m telescope. In the years before Herschel launched, BLAST provided data of unprecedented angular and spectral coverage in frequency bands close to the peak of dust emission in star forming regions in our Galaxy, and in galaxies at cosmological distances. More recently, BLASTPol was obtained by reconfiguring the BLAST focal plane as a submillimetric polarimeter to study the role that Galactic magnetic fields have in regulating the processes of star-formation. The first and successful BLASTPol flight from Antarctica in 2010 is followed by a second flight, currently scheduled for the end of 2012.

  2. ATLAST-9.2m: a Large-Aperture Deployable Space Telescope

    NASA Technical Reports Server (NTRS)

    Oergerle, William; Feinberg, Lee D.; Purves, Lloyd R.; Hyde, T. Tupper; Thronson, Harley A.; Townsend, Jacqueline A.; Postman, Marc; Bolear, Matthew R.; Budinoff, Jason G.; Dean, Bruce H.; Clampin, Mark C.; Ebbets, Dennis C.; Gong, Qian; Gull, Theodore R.; Howard, Joseph M.; Jones, Andrew L.; Lyon, Richard G.; Pasquale, Bert A.; Perrygo, Charles; Smith, Jeffrey S.; Thompson, Patrick L.; Woodgate, Bruce E.

    2010-01-01

    We present results of a study of a deployable version of the Advanced Technology Large-Aperture Space Telescope (ATLAST), designed to operate in a Sun-Earth L2 orbit. The primary mirror of the segmented 9.2-meter aperture has 36 hexagonal 1.315 m (flat to flat) glass mirrors. The architecture and folding of the telescope is similar to JWST, allowing it to fit into the 6.5 m fairing of a modest upgrade to the Delta-IV Heavy version of the Evolved Expendable Launch Vehicle (EELV). We discuss the overall observatory design, optical design, instruments, stray light, wavefront sensing and control, pointing and thermal control, and in-space servicing options.

  3. Large-aperture chirped volume Bragg grating based fiber CPA system.

    PubMed

    Liao, Kai-Hsiu; Cheng, Ming-Yuan; Flecher, Emilie; Smirnov, Vadim I; Glebov, Leonid B; Galvanauskas, Almantas

    2007-04-16

    A fiber chirped pulse amplification system at 1558 nm was demonstrated using a large-aperture volume Bragg grating stretcher and compressor made of Photo-Thermal-Refractive (PTR) glass. Such PTR glass based gratings represent a new type of pulse stretching and compressing devices which are compact, monolithic and optically efficient. Furthermore, since PTR glass technology enables volume gratings with transverse apertures which are large, homogeneous and scalable, it also enables high pulse energies and powers far exceeding those achievable with other existing compact pulse-compression technologies. Additionally, reciprocity of chirped gratings with respect to stretching and compression also enables to address a long-standing problem in CPA system design of stretcher-compressor dispersion mismatch.

  4. Large-aperture chirped volume Bragg grating based fiber CPA system

    NASA Astrophysics Data System (ADS)

    Liao, Kai-Hsiu; Cheng, Ming-Yuan; Flecher, Emilie; Smirnov, Vadim I.; Glebov, Leonid B.; Galvanauskas, Almantas

    2007-04-01

    A fiber chirped pulse amplification system at 1558nm was demonstrated using a large-aperture volume Bragg grating stretcher and compressor made of Photo-Thermal-Refractive (PTR) glass. Such PTR glass based gratings represent a new type of pulse stretching and compressing devices which are compact, monolithic and optically efficient. Furthermore, since PTR glass technology enables volume gratings with transverse apertures which are large, homogeneous and scalable, it also enables high pulse energies and powers far exceeding those achievable with other existing compact pulse-compression technologies. Additionally, reciprocity of chirped gratings with respect to stretching and compression also enables to address a long-standing problem in CPA system design of stretcher-compressor dispersion mismatch.

  5. A Large Aperture, High Energy Laser System for Optics and Optical Component Testing

    SciTech Connect

    Nostrand, M C; Weiland, T L; Luthi, R L; Vickers, J L; Sell, W D; Stanley, J A; Honig, J; Auerbach, J; Hackel, R P; Wegner, P J

    2003-11-01

    A large aperture, kJ-class, multi-wavelength Nd-glass laser system has been constructed at Lawrence Livermore National Lab which has unique capabilities for studying a wide variety of optical phenomena. The master-oscillator, power-amplifier (MOPA) configuration of this ''Optical Sciences Laser'' (OSL) produces 1053 nm radiation with shaped pulse lengths which are variable from 0.1-100 ns. The output can be frequency doubled or tripled with high conversion efficiency with a resultant 100 cm{sup 2} high quality output beam. This facility can accommodate prototype hardware for large-scale inertial confinement fusion lasers allowing for investigation of integrated system issues such as optical lifetime at high fluence, optics contamination, compatibility of non-optical materials, and laser diagnostics.

  6. Large Aperture "Photon Bucket" Optical Receiver Performance in High Background Environments

    NASA Technical Reports Server (NTRS)

    Vilnrotter, Victor A.; Hoppe, D.

    2011-01-01

    The potential development of large aperture groundbased "photon bucket" optical receivers for deep space communications, with acceptable performance even when pointing close to the sun, is receiving considerable attention. Sunlight scattered by the atmosphere becomes significant at micron wavelengths when pointing to a few degrees from the sun, even with the narrowest bandwidth optical filters. In addition, high quality optical apertures in the 10-30 meter range are costly and difficult to build with accurate surfaces to ensure narrow fields-of-view (FOV). One approach currently under consideration is to polish the aluminum reflector panels of large 34-meter microwave antennas to high reflectance, and accept the relatively large FOV generated by state-of-the-art polished aluminum panels with rms surface accuracies on the order of a few microns, corresponding to several-hundred micro-radian FOV, hence generating centimeter-diameter focused spots at the Cassegrain focus of 34-meter antennas. Assuming pulse-position modulation (PPM) and Poisson-distributed photon-counting detection, a "polished panel" photon-bucket receiver with large FOV will collect hundreds of background photons per PPM slot, along with comparable signal photons due to its large aperture. It is demonstrated that communications performance in terms of PPM symbol-error probability in high-background high-signal environments depends more strongly on signal than on background photons, implying that large increases in background energy can be compensated by a disproportionally small increase in signal energy. This surprising result suggests that large optical apertures with relatively poor surface quality may nevertheless provide acceptable performance for deep-space optical communications, potentially enabling the construction of cost-effective hybrid RF/optical receivers in the future.

  7. Pulse power requirements for large aperture optical switches based on plasma electrode Pockels cells

    SciTech Connect

    Rhodes, M.A.; Taylor, J.

    1992-06-01

    We discuss very large-aperture optical switches (greater than 30 [times] 30 cm) as an enabling technology for inertial confinement fusion drivers based on multipass laser amplifiers. Large-scale laser fusion drivers such as the Nova laser have been based on single-pass amplifier designs in part because of the unavailability of a suitable large-aperture switch. We are developing an optical switch based on a Pockels cell employing plasma-electrodes. A plasma-electrode Pockels cell (PEPC) is a longitudinal-mode Pockels cell in which a plasma discharge is formed on each side of an electro-optic crystal (typically KDP or deuterated KDP, often designated KD*P). The plasmas formed on either side of the crystal act as transparent electrodes for a switching-pulse and are intended to allow uniform charging of the entire crystal. The switching-pulse is a nominally rectangular high-voltage pulse equal to the half-wave voltage V[sub x] ( 8 kV for KD*P or 17 kV for KDP) and is applied across the crystal via the plasma-electrodes. When the crystal is charged to V[sub x], the polarization of an incoming, linearly polarized, laser beam is rotated by 90[degree]. When used in conjunction with an appropriate, passive polarizer, an optical switch is thus realized. A switch with a clear aperture of 37 [times] 37 cm is now in construction for the Beamlet laser which will serve as a test bed for this switch as well as other technologies required for an advanced NOVA laser design. In this paper, we discuss the unique power electronics requirements of PEPC optical switches.

  8. Pulse power requirements for large aperture optical switches based on plasma electrode Pockels cells

    SciTech Connect

    Rhodes, M.A.; Taylor, J.

    1992-06-01

    We discuss very large-aperture optical switches (greater than 30 {times} 30 cm) as an enabling technology for inertial confinement fusion drivers based on multipass laser amplifiers. Large-scale laser fusion drivers such as the Nova laser have been based on single-pass amplifier designs in part because of the unavailability of a suitable large-aperture switch. We are developing an optical switch based on a Pockels cell employing plasma-electrodes. A plasma-electrode Pockels cell (PEPC) is a longitudinal-mode Pockels cell in which a plasma discharge is formed on each side of an electro-optic crystal (typically KDP or deuterated KDP, often designated KD*P). The plasmas formed on either side of the crystal act as transparent electrodes for a switching-pulse and are intended to allow uniform charging of the entire crystal. The switching-pulse is a nominally rectangular high-voltage pulse equal to the half-wave voltage V{sub x} ( 8 kV for KD*P or 17 kV for KDP) and is applied across the crystal via the plasma-electrodes. When the crystal is charged to V{sub x}, the polarization of an incoming, linearly polarized, laser beam is rotated by 90{degree}. When used in conjunction with an appropriate, passive polarizer, an optical switch is thus realized. A switch with a clear aperture of 37 {times} 37 cm is now in construction for the Beamlet laser which will serve as a test bed for this switch as well as other technologies required for an advanced NOVA laser design. In this paper, we discuss the unique power electronics requirements of PEPC optical switches.

  9. Focal aberrations of large-aperture HOPG von-Hàmos x-ray spectrometers

    NASA Astrophysics Data System (ADS)

    Zastrau, U.; Brown, C. R. D.; Döppner, T.; Glenzer, S. H.; Gregori, G.; Lee, H. J.; Marschner, H.; Toleikis, S.; Wehrhan, O.; Förster, E.

    2012-09-01

    Focal aberrations of large-aperture highly oriented pyrolytic graphite (HOPG) crystals in von-Hàmos geometry are investigated by experimental and computational methods. A mosaic HOPG crystal film of 100 μm thickness diffracts 8 keV x-rays. This thickness is smaller than the absorption depth of the symmetric 004-reflection, which amounts to 257 μm. Cylindrically bent crystals with 110mm radius of curvature and up to 100 mm collection width produce a X-shaped halo around the focus. This feature vanishes when the collection aperture is reduced, but axial spectral profiles show that the resolution is not affected. X-ray topography reveals significant inhomogeneous crystallite domains of 2±1mm diameter along the entire crystal. Rocking curves shift by about ±20arcmin between domains, while their full width at half-maximum varies between 30 and 50 arcmin. These inhomogeneities are not imprinted at the focal spot, since the monochromatically reflecting area of the crystal is large compared to inhomogeneities. Ray-tracing calculations using a Monte-Carlo-based algorithm developed for mosaic crystals reproduce the X-shaped halo in the focal plane, stemming from the mosaic defocussing in the non-dispersive direction in combination with large apertures. The best achievable resolution is found by analyzing a diversity of rocking curve widths, source sizes and crystal thicknesses for 8 keV x-rays to be ΔE/E ~ 10-4. Finally a general analytic expression for the shape of the aberration is derived.

  10. Development of atmospheric pressure plasma processing machine tool for large aperture optics

    NASA Astrophysics Data System (ADS)

    Su, Xing; Wu, Yangong; Zhang, Peng; Xin, Qiang; Wang, Bo

    2016-10-01

    In recent years, major projects, such as National Ignition Facility and Laser Mégajoule, have generated great demands for large aperture optics with high surface accuracy and low Subsurface Damage (SSD) at the mean time. In order to remove SSD and improve surface quality, optics is fabricated by sub-aperture polishing. However, the efficiency of the sub-aperture polishing has been a bottleneck step for the optics manufacturing. Atmospheric Pressure Plasma Processing (APPP) as an alternate method offers high potential for speeding up the polishing process. This technique is based on chemical etching, hence there is no physical contact and no damage is induced. In this paper, a fast polishing machine tool is presented which is designed for fast polishing of the large aperture optics using APPP. This machine tool employs 3PRS-XY hybrid structure as its framework. There is a platform in the 3PRS parallel module to support the plasma generating system. And the large work piece is placed on the XY stage. In order to realize the complex motion trajectory for polishing the freeform optics, five axis of the tool operate simultaneously. To overcome the complexity of inverse kinematics calculation, a dedicated motion control system is also designed for speeding up the motion response. For high removal rate, the individual influence of several key processing parameters is investigated. And under specific production condition, this machine tool offers a high material over 30mm3/min for fused silica substrates. This results shows that APPP machine tool has a strong potential for fast polishing large optics without introducing SSD.

  11. Topology optimization-based lightweight primary mirror design of a large-aperture space telescope.

    PubMed

    Liu, Shutian; Hu, Rui; Li, Quhao; Zhou, Ping; Dong, Zhigang; Kang, Renke

    2014-12-10

    For the large-aperture space telescope, the lightweight primary mirror design with a high-quality optical surface is a critical and challenging issue. This work presents a topology optimization-based design procedure for a lightweight primary mirror and a new mirror configuration of a large-aperture space telescope is obtained through the presented design procedure. Inspired by the topology optimization method considering cast constraints, an optimization model for the configuration design of the mirror back is proposed, through which the distribution and the heights of the stiffeners on the mirror back can be optimized simultaneously. For the purpose of minimizing the optical surface deviation due to self-weight and polishing pressure loadings, the objective function is selected as to maximize the mirror structural stiffness, which can be achieved by minimizing the structural compliance. The total mass of the primary mirror is assigned as the constraint. In the application example, results of the optimized design topology for two kinds of mass constraints are presented. Executing the design procedure for specific requirements and postprocessing the topology obtained of the structure, a new mirror configuration with tree-like stiffeners and a multiple-arch back in double directions is proposed. A verification model is constructed to evaluate the design results and the finite element method is used to calculate the displacement of the mirror surface. Then the RMS deviation can be obtained after fitting the deformed surface by Zernike polynomials. The proposed mirror is compared with two classical mirrors in the optical performance, and the comparison results demonstrate the superiority of the new mirror configuration.

  12. A method on error analysis for large-aperture optical telescope control system

    NASA Astrophysics Data System (ADS)

    Su, Yanrui; Wang, Qiang; Yan, Fabao; Liu, Xiang; Huang, Yongmei

    2016-10-01

    For large-aperture optical telescope, compared with the performance of azimuth in the control system, arc second-level jitters exist in elevation under different speeds' working mode, especially low-speed working mode in the process of its acquisition, tracking and pointing. The jitters are closely related to the working speed of the elevation, resulting in the reduction of accuracy and low-speed stability of the telescope. By collecting a large number of measured data to the elevation, we do analysis on jitters in the time domain, frequency domain and space domain respectively. And the relation between jitter points and the leading speed of elevation and the corresponding space angle is concluded that the jitters perform as periodic disturbance in space domain and the period of the corresponding space angle of the jitter points is 79.1″ approximately. Then we did simulation, analysis and comparison to the influence of the disturbance sources, like PWM power level output disturbance, torque (acceleration) disturbance, speed feedback disturbance and position feedback disturbance on the elevation to find that the space periodic disturbance still exist in the elevation performance. It leads us to infer that the problems maybe exist in angle measurement unit. The telescope employs a 24-bit photoelectric encoder and we can calculate the encoder grating angular resolution as 79.1016'', which is as the corresponding angle value in the whole encoder system of one period of the subdivision signal. The value is approximately equal to the space frequency of the jitters. Therefore, the working elevation of the telescope is affected by subdivision errors and the period of the subdivision error is identical to the period of encoder grating angular. Through comprehensive consideration and mathematical analysis, that DC subdivision error of subdivision error sources causes the jitters is determined, which is verified in the practical engineering. The method that analyze error

  13. Large-aperture broadband sapphire windows for common aperture, target acquisition, tracking, and surveillance systems

    NASA Astrophysics Data System (ADS)

    Askinazi, Joel

    1997-06-01

    State of the art optical sensing systems performing target acquisition/tracking and surveillance functions are being designed to incorporate a number of sensors into one package. These include visual and MWIR cameras, FLIRs, and laser range finders. These combined systems are being configured to view through a common aperture window. Typical window diameters are to eleven inches, but some surveillance applications have windows approaching twenty inches in diameter. These sensor windows typically operate in hostile environments including very high pressure differentials, large thermal gradients, and severe rain and sand abrasion. EMI/EMC protection and de-icing capabilities are also commonly required. For airborne applications and to minimize thermal gradients, thinner, lightweight, high strength windows are also necessary. Sapphire is an ideal window material to satisfy these requirements due to its high strength, UV-MWIR bandpass, minimal optical scatter, excellent index of refraction homogeneity and very high scratch/impact resistance. Associated optical fabrication, grid lithography and optical coating processes have been developed at Hughes Danbury for sapphire windows. This paper addresses the development of a family of large aperture, broadband sapphire windows which also provide EMI/EMC protection and de-icing capabilities. The resulting design configuration and performance characteristics are also addressed. Future technology development requirements are also discussed.

  14. Study on the method to test large-aperture hyperboloid convex mirror

    NASA Astrophysics Data System (ADS)

    Meng, Xiaohui; Dong, Huiwen; Guo, Wen; Wang, Huijun

    2014-08-01

    There are numerous reflecting optical system designs that call for large-aperture convex surfaces, such as secondary mirror in on-axis three mirror anastigmatic (TMA). Several methods to test high accuracy hyperboloid convex surfaces are introduced separately in this paper. A kind of arrangement is chosen to test a surface with diameter of 420mm, radius of 1371mm, and conic K -2.1229. The CGH compensator for testing is designed, which is made up of illumination lens and hologram test plate with designed residual wavefront aberration less than 0.001λ (RMS). The second transmitted method that is equipped with a technical flat surface coating by Ag film in the bottom of surface mirror under test, which form an auto-collimation optical system to eliminate the aberration. The Hindle-Simpson test that requires a larger meniscus lens to compensate the optical aberration, and the designed result of optical test system is less than 0.0016λ. Contrasting the CGH compensator and the second transmitted method, the Hindle-Simpson testing method has the advantage of it is easily to manufacture and adjust; meanwhile the test result is stable and has been less affected by the environment. It has been found that the method is rational and reliable, and it can fulfill the requirement of manufacturing and testing process for hyperboloid convex mirrors.

  15. Metrological characterization of a large aperture Fizeau for x-ray mirrors measurement

    NASA Astrophysics Data System (ADS)

    Vannoni, Maurizio; Freijo Martín, Idoia

    2015-06-01

    The European XFEL is a large facility under construction in Hamburg, Germany. It will provide a transversally fully coherent x-ray radiation with outstanding characteristics: high repetition rate (up to 2700 pulses with a 0.6 milliseconds long pulse train at 10Hz), short wavelength (down to 0.05 nm), short pulse (in the femtoseconds scale) and high average brilliance (1.61025 photons / s / mm2 / mrad2/ 0.1% bandwidth). Due to the very short wavelength and very high pulse energy, all the mirrors need to have high quality surface, to be very long, and at the same time to implement an effective cooling system. Matching these tight specifications and assessing them with high precision optical measurements is very challenging. In order to measure the mirrors and to characterize their interaction with the mechanical mounts, we equipped a Metrology Laboratory with a Large Aperture Fizeau. The system is a classical 100 mm diameter commercial Fizeau, with an additional expander providing a 300 mm diameter. Despite the commercial nature of the system, special care has been done in the polishing of the reference flats and in the expander quality. In this report, we show the preparation of the instrument, the calibration and the performance characterization, together with some preliminary results. We also describe the approach that we want to follow for the x-rays mirrors measurements. The final goal will be to characterize very long mirrors, almost 1 meter long, with nanometer accuracy.

  16. Determination of Turbulent Sensible Heat Flux over a Coastal Maritime Area Using a Large Aperture Scintillometer

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Hyun

    2015-11-01

    Scintillometers have been widely used in estimating the surface-layer sensible heat flux (Q_H) over natural and urban surfaces, but their application over water bodies is rare. Here, a large aperture scintillometer (LAS) was deployed over a coastal maritime area (`a beach') with an optical path distance of 1 km to investigate LAS capability in estimating the sensible heat fluxes. The measurements were conducted for clear days in the cold season, characterized by a warmer sea surface than the overlying air throughout the studied days. The LAS-derived Q_H showed a significant diurnal variability of 10-150 W m^{-2} at the coastal site, and it was found that local thermal advection and tidal change at the site largely influenced the diurnal variability. A series of sensitivity tests indicated that the uncertainty in the LAS-derived Q_H was less than 11 %, except when De Bruin's similarity function was used. The overall results demonstrate that the LAS system can detect the magnitude and variability of the turbulent heat exchange at the coastal site with high temporal resolution, suggesting its usefulness for estimating Q_H in the coastal maritime environment.

  17. Time-gated ballistic imaging using a large aperture switching beam.

    PubMed

    Mathieu, Florian; Reddemann, Manuel A; Palmer, Johannes; Kneer, Reinhold

    2014-03-24

    Ballistic imaging commonly denotes the formation of line-of-sight shadowgraphs through turbid media by suppression of multiply scattered photons. The technique relies on a femtosecond laser acting as light source for the images and as switch for an optical Kerr gate that separates ballistic photons from multiply scattered ones. The achievable image resolution is one major limitation for the investigation of small objects. In this study, practical influences on the optical Kerr gate and image quality are discussed theoretically and experimentally applying a switching beam with large aperture (D = 19 mm). It is shown how switching pulse energy and synchronization of switching and imaging pulse in the Kerr cell influence the gate's transmission. Image quality of ballistic imaging and standard shadowgraphy is evaluated and compared, showing that the present ballistic imaging setup is advantageous for optical densities in the range of 8 < OD < 13. Owing to the spatial transmission characteristics of the optical Kerr gate, a rectangular aperture stop is formed, which leads to different resolution limits for vertical and horizontal structures in the object. Furthermore, it is reported how to convert the ballistic imaging setup into a schlieren-type system with an optical schlieren edge.

  18. 8 Meter Advanced Technology Large-Aperture Space Telescope (ATLAST-8m)

    NASA Technical Reports Server (NTRS)

    Stahl, H. Philip

    2010-01-01

    ATLAST-8m (Advanced Technology Large Aperture Space Telescope) is a proposed 8-meter monolithic UV/optical/NIR space observatory (wavelength range 110 to 2500 nm) to be placed in orbit at Sun-Earth L2 by NASA's planned Ares V heavy lift vehicle. Given its very high angular resolution (15 mas @ 500 nm), sensitivity and performance stability, ATLAST-8m is capable of achieving breakthroughs in a broad range of astrophysics including: Is there life elsewhere in the Galaxy? An 8-meter UVOIR observatory has the performance required to detect habitability (H2O, atmospheric column density) and biosignatures (O2, O3, CH4) in terrestrial exoplanet atmospheres, to reveal the underlying physics that drives star formation, and to trace the complex interactions between dark matter, galaxies, and intergalactic medium. The ATLAST Astrophysics Strategic Mission Concept Study developed a detailed point design for an 8-m monolithic observatory including optical design; structural design/analysis including primary mirror support structure, sun shade and secondary mirror support structure; thermal analysis; spacecraft including structure, propulsion, GN&C, avionics, power systems and reaction wheels; mass and power budgets; and system cost. The results of which were submitted by invitation to NRC's 2010 Astronomy & Astrophysics Decadal Survey.

  19. The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) 2005: Calibration and Targeted Sources

    NASA Astrophysics Data System (ADS)

    Truch, M. D. P.; Ade, P. A. R.; Bock, J. J.; Chapin, E. L.; Devlin, M. J.; Dicker, S.; Griffin, M.; Gundersen, J. O.; Halpern, M.; Hargrave, P. C.; Hughes, D. H.; Klein, J.; Marsden, G.; Martin, P. G.; Mauskopf, P.; Netterfield, C. B.; Olmi, L.; Pascale, E.; Patanchon, G.; Rex, M.; Scott, D.; Semisch, C.; Tucker, C.; Tucker, G. S.; Viero, M. P.; Wiebe, D. V.

    2008-07-01

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) operated successfully during a 100 hr flight from northern Sweden in 2005 June (BLAST05). As part of the calibration and pointing procedures, several compact sources were mapped, including solar system, Galactic, and extragalactic targets, specifically Pallas, CRL 2688, LDN 1014, IRAS 20126+4104, IRAS 21078+5211, IRAS 21307+5049, IRAS 22134+5834, IRAS 23011+6126, K3-50, W75N, and Mrk 231. One additional source, Arp 220, was observed and used as our primary calibrator. Details of the overall BLAST05 calibration procedure are discussed here. The BLAST observations of each compact source are described, flux densities and spectral energy distributions are reported, and these are compared with previous measurements at other wavelengths. The 250, 350, and 500 μm BLAST data can provide useful constraints to the amplitude and slope of the submillimeter continuum, which in turn may be useful for the improved calibration of other submillimeter instruments.

  20. Distribution-dependent total exoplanet yield for a large aperture space telescope

    NASA Astrophysics Data System (ADS)

    Morris, Evan; Schiminovich, David

    2017-01-01

    A major scientific goal for future large aperture space telescopes is the discovery and characterization of habitable earth-like planets around FGK+M stars out to 10-20 pc. Using the design and observing plan for such a mission, we calculated the total exoplanet yield of a direct imaging survey, with detections including but not limited to potential earth analogs. In light of uncertainty of exoplanet occurrence rates, we used several of the best available exoplanetary distribution functions and assumed architectures to produce a Monte Carlo simulation of nearby planetary systems and observational parameters, and assessed detectability across the sample. Our calculations show a range of yields depending on the assumed distribution functions. We also compare our predictions to those of other detection methods in order to identify areas of parameter space (e.g. radius, period) uniquely constrained by direct imaging. In general, our calculations suggest that a higher completeness can be achieved with direct imaging, which will allow for calculation of a more accurate occurrence rate in local space.

  1. The measurement and analysis of wavefront structure from large aperture ICF optics

    SciTech Connect

    Wolfe, C.R.; Lawson, J.K.

    1995-05-30

    This paper discusses the techniques, developed over the past year, for high spatial resolution measurement and analysis of the transmitted and/or reflected wavefront of large aperture ICF optical components. Parts up to 400 mm {times} 750 mm have been measured and include: laser slabs, windows, KDP crystals and lenses. The measurements were performed using state-of-the-art commercial phase shifting interferometers at a wavelength of 633 {mu}m. Both 1 and 2-D Fourier analysis have been used to characterize the wavefront; specifically the Power Spectral Density, (PSD), function was calculated. The PSDs of several precision optical components will be shown. The PSD(V) is proportional to the (amplitude){sup 2} of components of the Fourier frequency spectrum. The PSD describes the scattered intensity and direction as a function of scattering angle in the wavefront. The capability of commercial software is limited to 1-D Fourier analysis only. We are developing our own 2-D analysis capability in support of work to revise specifications for NIF optics. 2-D analysis uses the entire wavefront phase map to construct 2D PSD functions. We have been able to increase the signal-to-noise relative to 1-D and can observe very subtle wavefront structure.

  2. Large-Aperture Wide-Bandwidth Anti-Reflection-Coated Silicon Lenses for Millimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Datta, R.; Munson, C. D.; Niemack, M. D.; McMahon, J. J.; Britton, J.; Wollack, E. J.; Beall, J.; Devlin, M. J.; Fowler, J.; Gallardo, P.; Hubmayr, J.; Irwin, K.; Newburgh, L.; Nibarger, J. P.; Page, L.; Quijada, M. A.; Schmitt, B. L.; Staggs, S. T.; Thornton, R.; Zhang, L.

    2013-01-01

    The increasing scale of cryogenic detector arrays for sub-millimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n = 3.4, low loss, and relatively high thermal conductivity is a nearly optimal material for these purposes, but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coffecient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating. We have fabricated and coated silicon lenses as large as 33.4 cm in diameter with coatings optimized for use between 125-165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30 deg. with low cross-polarization. We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to sub-millimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth.

  3. Large-aperture Wide-bandwidth Antireflection-coated Silicon Lenses for Millimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Datta, R.; Munson, C. D.; Niemack, M. D.; McMahon, J. J.; Britton, J.; Wollack, Edward J.; Beall, J.; Devlin, M. J.; Fowler, J.; Gallardo, P.; Hubmayr, J.; Irwin, K.; Newburgh, L.; Nibarger, J. P.; Page, L.; Quijada, Manuel A.; Schmitt, B. L.; Staggs, S. T.; Thornton, R.; Zhang, L.

    2013-01-01

    The increasing scale of cryogenic detector arrays for submillimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n 3.4, low loss, and high thermal conductivity is a nearly optimal material for these purposes but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coefficient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three-axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating.We have fabricated silicon lenses as large as 33.4 cm in diameter with micromachined layers optimized for use between 125 and 165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30deg with low cross polarization.We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to submillimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth.

  4. A Future Large-Aperture UVOIR Space Observatory: Key Technologies and Capabilities

    NASA Technical Reports Server (NTRS)

    Bolcar, Matthew Ryan; Stahle, Carl M.; Balasubramaniam, Kunjithapatham; Clampin, Mark; Feinberg, Lee D.; Mosier, Gary E.; Quijada, Manuel A.; Rauscher, Bernard J.; Redding, David C.; Rioux, Norman M.; Shaklan, Stuart B.; Stahl, H. Philip; Thronson, Harley A.

    2015-01-01

    We present the key technologies and capabilities that will enable a future, large-aperture ultravioletopticalinfrared (UVOIR) space observatory. These include starlight suppression systems, vibration isolation and control systems, lightweight mirror segments, detector systems, and mirror coatings. These capabilities will provide major advances over current and near-future observatories for sensitivity, angular resolution, and starlight suppression. The goals adopted in our study for the starlight suppression system are 10-10 contrast with an inner working angle of 20 milliarcsec and broad bandpass. We estimate that a vibration and isolation control system that achieves a total system vibration isolation of 140 dB for a vibration-isolated mass of 5000 kg is required to achieve the high wavefront error stability needed for exoplanet coronagraphy. Technology challenges for lightweight mirror segments include diffraction-limited optical quality and high wavefront error stability as well as low cost, low mass, and rapid fabrication. Key challenges for the detector systems include visible-blind, high quantum efficiency UV arrays, photon counting visible and NIR arrays for coronagraphic spectroscopy and starlight wavefront sensing and control, and detectors with deep full wells with low persistence and radiation tolerance to enable transit imaging and spectroscopy at all wavelengths. Finally, mirror coatings with high reflectivity ( 90), high uniformity ( 1) and low polarization ( 1) that are scalable to large diameter mirror substrates will be essential for ensuring that both high throughput UV observations and high contrast observations can be performed by the same observatory.

  5. The Advanced Technology Large-Aperture Space Telescope (ATLAST) Technology Roadmap

    NASA Technical Reports Server (NTRS)

    Stahle, Carl; Balasubramanian, K.; Bolcar, M.; Clampin, M.; Feinberg, L.; Hartman, K.; Mosier, C.; Quijada, M.; Rauscher, B.; Redding, D.; Shaklan, S.; Stahl, P.; Thronson, H.

    2014-01-01

    We present the key technologies and capabilities that will enable a future, large-aperture ultravioletopticalinfrared (UVOIR) space observatory. These include starlight suppression systems, vibration isolation and control systems, lightweight mirror segments, detector systems, and mirror coatings. These capabilities will provide major advances over current and near-future observatories for sensitivity, angular resolution, and starlight suppression. The goals adopted in our study for the starlight suppression system are 10-10 contrast with an inner working angle of 40 milliarcsec and broad bandpass. We estimate that a vibration and isolation control system that achieves a total system vibration isolation of 140 dB for a vibration-isolated mass of 5000 kg is required to achieve the high wavefront error stability needed for exoplanet coronagraphy. Technology challenges for lightweight mirror segments include diffraction-limited optical quality and high wavefront error stability as well as low cost, low mass, and rapid fabrication. Key challenges for the detector systems include visible-blind, high quantum efficiency UV arrays, photon counting visible and NIR arrays for coronagraphic spectroscopy and starlight wavefront sensing and control, and detectors with deep full wells with low persistence and radiation tolerance to enable transit imaging and spectroscopy at all wavelengths. Finally, mirror coatings with high reflectivity ( 90), high uniformity ( 1) and low polarization ( 1) that are scalable to large diameter mirror substrates will be essential for ensuring that both high throughput UV observations and high contrast observations can be performed by the same observatory.

  6. Development of Large-Aperture, Light-Weight Fresnel Lenses for Gossamer Space Telescopes

    SciTech Connect

    Sham, D; Hyde, R; Weisberg, A; Early, J; Rushford, M; Britten, J

    2002-04-29

    In order to examine more distant astronomical objects, with higher resolution, future space telescopes require objectives with significantly larger aperture than presently available. NASA has identified a progression in size from the 2.4m aperture objective currently used in the HUBBLE space telescope[l,2], to 25m and greater in order to observe, e.g., extra-solar planets. Since weight is a crucial factor for any object sent into space, the relative weight of large optics over a given area must be reduced[3]. The areal mass density of the primary mirror for the Hubble space telescope is {approx}200 kg/m{sup 2}. This is expected to be reduced to around 15 kg/m{sup 2} for the successor to Hubble--the next generation space telescope (NGST)[4]. For future very large aperture telescopes needed for extra-solar planet detection, the areal mass density must be reduced even further. For example, the areal mass density goal for the Gossamer space telescopes is < 1 kg/m{sup 2}. The production of lightweight focusing optics at >10m size is also an enabling technology for many other applications such as Earth observation, power beaming, and optical communications.

  7. Switch-zoom optical system design of large aperture ground-based photoelectric detection

    NASA Astrophysics Data System (ADS)

    Yan, Peipei; Liu, Kai; Duan, Jing; Jiang, Kai; Shan, Qiusha

    2016-10-01

    Binary optics can be used to increase optical performances, decrease size and weight, and decrease systems costs in numerous applications. By means of hybrid diffractive-refractive, a switch-zoom optical system of catadioptric large aperture ground-based photoelectric detection is designed. The characteristic of the system is that it is a compact optical system without moving parts which can get two focal lengths. And the quality of image approaches the diffraction limited. Ritchey-Chrétien (R-C) mirror and a field lens are common for long-focus system and short-focus system. Two refract groups transmitting optical system are used for zooming. In order to satisfy the demand of energy regulation, it is designed afocal beam between field lens and later refract optical system. Filter and variable density plate are placed in it to guarantee the imaging quality. The focal length is 3750mm and F number is 7.5 for the long-focus system, and the focal length is 1850mm and F number is 3.75 for the short-focus system. Former part and later lens of the system are both perfect imaging. They can be fabricated and detected independently. So the design demand can be satisfied better and the imaging quality can be improved.

  8. Analysis of temporal contrast degradation due to wave front deviation in large aperture ultra-short pulse focusing system

    NASA Astrophysics Data System (ADS)

    Zhu, Ping; Xie, Xinglong; Zhu, Jianqiang; Zhu, Haidong; Yang, Qingwei; Kang, Jun; Guo, Ailin; Gao, Qi

    2014-11-01

    In extremely intense laser system used for plasma physics experiments, temporal contrast is an important property of the ultra-short pulse. In this paper, we theoretically study the temporal contrast degradation due to wave front deviation in large aperture ultra-short pulse focusing system. Two-step focusing fast Fourier transform (FFT) algorithm with the coordinate transform based on Fresnel approximation in space domain and Fourier integral transform method in time domain were used to simulate the focusing process spatially and temporally, in which the spatial distribution of ultra-short pulse temporal contrast characteristics at the focal spot is related to the wave front in large aperture off-axis parabolic mirror focusing optical system. Firstly, temporal contrast degradation due to wave front noise with higher spatial frequency is analyzed and appropriate evaluation parameter for large aperture ultra-short pulse focusing system is put forward from the perspective of temporal contrast. Secondly, the influence of wave front distortion with lower spatial frequency on temporal contrast is revealed comparing different degradation characteristics of various aberrations. At last, a method by controlling and optimizing the wave front to prevent temporal contrast degradation in large aperture ultra-short laser system is proposed, which is of great significance for high temporal contrast petawatt laser facilities.

  9. How Membrane-Active Peptides Get into Lipid Membranes.

    PubMed

    Sani, Marc-Antoine; Separovic, Frances

    2016-06-21

    The structure-function relationship for a family of antimicrobial peptides (AMPs) from the skin of Australian tree frogs is discussed and compared with that of peptide toxins from bee and Australian scorpion venoms. Although these membrane-active peptides induce a similar cellular fate by disrupting the lipid bilayer integrity, their lytic activity is achieved via different modes of action, which are investigated in relation to amino acid sequence, secondary structure, and membrane lipid composition. In order to better understand what structural features govern the interaction between peptides and lipid membranes, cell-penetrating peptides (CPPs), which translocate through the membrane without compromising its integrity, are also discussed. AMPs possess membrane lytic activities that are naturally designed to target the cellular membrane of pathogens or competitors. They are extremely diverse in amino acid composition and often show specificity against a particular strain of microbe. Since our antibiotic arsenal is declining precariously in the face of the rise in multiantibiotic resistance, AMPs increasingly are seen as a promising alternative. In an effort to understand their molecular mechanism, biophysical studies of a myriad of AMPs have been reported, yet no unifying mechanism has emerged, rendering difficult the rational design of drug leads. Similarly, a wide variety of cytotoxic peptides are found in venoms, the best known being melittin, yet again, predicting their activity based on a particular amino acid composition or secondary structure remains elusive. A common feature of these membrane-active peptides is their preference for the lipid environment. Indeed, they are mainly unstructured in solution and, in the presence of lipid membranes, quickly adsorb onto the surface, change their secondary structure, eventually insert into the hydrophobic core of the membrane bilayer, and finally disrupt the bilayer integrity. These steps define the molecular

  10. Fluid transport by active elastic membranes

    NASA Astrophysics Data System (ADS)

    Evans, Arthur A.; Lauga, Eric

    2011-09-01

    A flexible membrane deforming its shape in time can self-propel in a viscous fluid. Alternatively, if the membrane is anchored, its deformation will lead to fluid transport. Past work in this area focused on situations where the deformation kinematics of the membrane were prescribed. Here we consider models where the deformation of the membrane is not prescribed, but instead the membrane is internally forced. Both the time-varying membrane shape and the resulting fluid motion result then from a balance between prescribed internal active stresses, internal passive resistance, and external viscous stresses. We introduce two specific models for such active internal forcing: one where a distribution of active bending moments is prescribed, and one where active inclusions exert normal stresses on the membrane by pumping fluid through it. In each case, we asymptotically calculate the membrane shape and the fluid transport velocities for small forcing amplitudes, and recover our results using scaling analysis.

  11. The next generation balloon-borne large aperture submillimeter telescope (BLAST-TNG)

    NASA Astrophysics Data System (ADS)

    Dober, Bradley Jerald

    Large areas of astrophysics, such as precision cosmology, have benefited greatly from large maps and datasets, yielded by telescopes of ever-increasing number and ability. However, due to the unique challenges posed by submillimeter polarimetry, the study of molecular cloud dynamics and star formation remain stunted. Previously, polarimetry data was limited to a few vectors on only the brightest areas of molecular clouds. This made drawing statistically-driven conclusions a daunting task. However, the successful flight of the Balloon-born Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) generated maps with thousands of independent polarization measurements of molecular clouds, and ushered in a new era of empirical modeling of molecular cloud dynamics. Now that the potential benefits from large-scale maps of magnetic fields in molecular clouds had been identified, a successor that would truly unlock the secrets must be born. The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG), the successor to BLASTPol, has the ability to make larger and more detailed maps of magnetic fields in molecular clouds. It will push the field of star formation into a statistics-driven, empirical realm. With these large, detailed datasets, astronomers will be able to find new relationships between the dust dynamics and the magnetic fields. The field will surge to a new level of understanding. One of the key enabling technologies of BLAST-TNG is its three arrays of polarization-sensitive Microwave Kinetic Inductance Detectors (MKIDs). MKIDs are superconducting RLC circuits with a resonant frequency that shifts proportionally to the amount of incident radiation. The key feature of MKIDs is that thousands of detectors, each with their own unique resonant frequency, can be coupled to the same readout line. This technology will be able to drive the production of large-scale monolithic arrays, containing tens or hundreds of thousands of detectors

  12. Advances in deployable structures and surfaces for large apertures in space

    NASA Astrophysics Data System (ADS)

    Santiago-Prowald, J.; Baier, H.

    2013-12-01

    Large apertures in space have applications for telecommunications, Earth observation and scientific missions. This paper reviews advances in mechanical architectures and technologies for large deployable apertures for space antennas and telescopes. Two complementary approaches are described to address this challenge: the deployment of structures based on quasi-rigid members and highly flexible structures. Regarding the first approach, deployable articulated structures are classified in terms of their kinematics as 3D or planar linkages in multiple variants, resulting in different architectures of radial, peripheral or modular constructions. A dedicated discussion on the number of degrees of freedom and constraints addresses the deployment reliability and thermo-elastic stability of large elastic structures in the presence of thermal gradients. This aspect has been identified as a design driver for new developments of peripheral ring and modular structures. Meanwhile, other design drivers are maintained, such as the optimization of mass and stiffness, overall accuracy and stability, and pragmatic aspects including controlled industrial development and a commitment to operators' needs. Furthermore, reflecting surface technologies and concepts are addressed with a view to the future, presenting advances in technical solutions for increasing apertures and reducing areal mass densities to affordable levels for future missions. Highly flexible materials capable of producing ultra-stable shells are described with reference to the state of the art and new developments. These concepts may enable large deployable surfaces for antennas and telescopes, as well as innovative optical concepts such as photon sieves. Shape adjustment and shape control of these surfaces are described in terms of available technologies and future needs, particularly for the reconfiguration of telecommunications antennas. In summary, the two complementary approaches described and reviewed cover the

  13. BLAST-TNG: A Next Generation Balloon-borne Large Aperture Submillimeter Polarimeter

    NASA Astrophysics Data System (ADS)

    Fissel, Laura M.; Ade, Peter; Angilè, Francesco E.; Campbell Ashton, Peter; Austermann, Jason Edward; Billings, Tashalee; Che, George; Cho, Hsiao-Mei; Cunningham, Maria R.; Davis, Kristina; Devlin, Mark J.; Dicker, Simon; Dober, Bradley; Fukui, Yasuo; Galitzki, Nicholas; gao, jiansong; Gordon, Sam; Groppi, Christopher E.; Hillbrand, Seth; Hilton, Gene; Hubmayr, Hannes; Irwin, Kent; Jones, Paul; Klein, Jeffrey; li, dale; Li, Zhi-Yun; lourie, nathan; Lowe, Ian; Mani, Hamdi; Martin, Peter G.; Mauskopf, Philip; McKenney, Christopher; Nati, Federico; Novak, Giles; Pascale, Enzo; pisano, giampaolo; Pereira Santos, Fábio; Scott, Douglas; Sinclair, Adrian; Diego Diego Soler, Juan; tucker, carole; Underhill, Matthew; Vissers, Michael; Williams, Paul

    2017-01-01

    Measurements of polarized thermal dust emission can be used to map magnetic fields in the interstellar medium. Recently, BLASTPol, the Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry, has published the most detailed map ever made of a giant molecular cloud forming high-mass stars. I will present an overview of The Next Generation BLAST polarimeter (BLAST-TNG), the successor telescope to BLASTPol, which maps linearly polarized dust emission at 250, 350 and 500 μm. BLAST-TNG utilizes a 2.5-meter carbon-fiber primary mirror that illuminates focal plane arrays containing over 3,000 microwave kinetic inductance detectors. This new polarimeter has an order of magnitude increase in mapping speed and resolution compared to BLASTPol and we expect to make over 500,000 measurements of magnetic field orientation per flight. BLAST-TNG will have the sensitivity to map entire molecular cloud complexes as well as regions of diffuse high Galactic latitude dust. It also has the resolution (FWHM = 25’’ at 250 μm) necessary to trace magnetic fields in prestellar cores and dense filaments. BLAST-TNG will thus provide a crucial link between the low resolution Planck all-sky maps and the detailed but narrow field of view polarimetry capabilities of ALMA. For our first Antarctic flight in December 2017 we are putting out a call for shared-risk proposals to fill 25% of the available science time. In addition, BLAST-TNG data will be publicly released within a year of the publication of our first look papers, leaving a large legacy data set for the study of the role played by magnetic fields in the star formation process and the properties of interstellar dust.

  14. Tethered Formation Configurations: Meeting the Scientific Objectives of Large Aperture and Interferometric Science

    NASA Technical Reports Server (NTRS)

    Farley, Rodger E.; Quinn, David A.; Brodeur, Stephen J. (Technical Monitor)

    2001-01-01

    With the success of the Hubble Space Telescope, it has become apparent that new frontiers of science and discovery are made every time an improvement in imaging resolution is made. For the HST working primarily in the visible and near-visible spectrum, this meant designing, building, and launching a primary mirror approximately three meters in diameter. Conventional thinking tells us that accomplishing a comparable improvement in resolution at longer wavelengths for Earth and Space Science applications requires a corresponding increase in the size of the primary mirror. For wavelengths in the sub-millimeter range, a very large telescope with an effective aperture in excess of one kilometer in diameter would be needed to obtain high quality angular resolution. Realistically a single aperture this large is practically impossible. Fortunately such large apertures can be constructed synthetically. Possibly as few as three 34 meter diameter mirrors flying in precision formation could be used to collect light at these longer wavelengths permitting not only very large virtual aperture science to be carried out, but high-resolution interferometry as well. To ensure the longest possible mission duration, a system of tethered spacecraft will be needed to mitigate the need for a great deal of propellant. A spin-stabilized, tethered formation will likely meet these requirements. Several configurations have been proposed which possibly meet the needs of the Space Science community. This paper discusses two of them, weighing the relative pros and cons of each concept. The ultimate goal being to settle on a configuration which combines the best features of structure, tethers, and formation flying to meet the ambitious requirements necessary to make future large synthetic aperture and interferometric science missions successful.

  15. Tethered Formation Configurations: Meeting the Scientific Objectives of Large Aperture and Interferometric Science

    NASA Technical Reports Server (NTRS)

    Farley, Rodger E.; Quinn, David A.

    2004-01-01

    With the success of the Hubble Space Telescope, it has become apparent that new frontiers of science and discovery are made every time an improvement in imaging resolution is made. For the HST working primarily in the visible and near-visible spectrum, this meant designing, building and launching a primary mirror approximately three meters in diameter. Conventional thinking tells us that accomplishing a comparable improvement in resolution at longer wavelengths for Earth and Space Science applications requires a corresponding increase in the size of the primary mirror. For wavelengths in the sub-millimeter range, a very large telescope with an effective aperture in excess of one kilometer in diameter would be needed to obtain high quality angular resolution. Realistically a single aperture this large is practically impossible. Fortunately such large apertures can be constructed synthetically. Possibly as few as three 3 - 4 meter diameter mirrors flying in precision formation could be used to collect light at these longer wavelengths permitting not only very large virtual aperture science to be carried out, but high-resolution interferometry as well. To ensure the longest possible mission duration, a system of tethered spacecraft will be needed to mitigate the need for a great deal of propellant. A spin-stabilized, tethered formation will likely meet these requirements. Several configurations have been proposed which possibly meet the needs of the Space Science community. This paper discusses two of them, weighing the relative pros and cons of each concept. The ultimate goal being to settle on a configuration which combines the best features of structure, tethers and formation flying to meet the ambitious requirements necessary to make future large synthetic aperture and interferometric science missions successful.

  16. Construction and Characterization of a Large Aperture Blackbody for Infrared Radiometer Calibration

    NASA Astrophysics Data System (ADS)

    Park, Chul-Woung; Yoo, Yong Shim; Kim, Bong-Hak; Chun, Sejong; Park, Seung-Nam

    2011-08-01

    A large aperture blackbody (LABB) with a diameter of 1 m has been successfully constructed for calibrating radiation thermometers and infrared radiometers with a wide field of view in the temperature range between 10 °C and 90 °C. The blackbody is a 1 m long cylindro-conical cavity with a diameter of 1.1 m. Its conical bottom has an apex angle of 120°. To achieve good temperature stability and uniformity, the cavity is integrated to a water-bath to which the pressurized water is supplied from a reservoir. To reduce the convection heat loss from the cavity to the ambient, the cavity is purged of the dried air that passes through a coiled tube immersed in the reservoir. For an uncertainty evaluation of the LABB, its temperature stability was measured by using a reference radiation thermometer (RRT) and a platinum resistance thermometer (PRT), and its radiance temperature distributions on the aperture plane were measured by using a thermal camera. Measuring the spectral emissivity of the coating material, the effective emissivity of the blackbody was calculated to be 0.9955 from 1 μm to 15 μm. The expanded uncertainty of the radiance temperature scale was evaluated based on the PRT readings, which vary from 0.3 °C to 0.5 °C ( k = 2) in the temperature range. The temperature scale is validated by comparing with the RRT of which the temperature scale is realized by a multiple fixed-point calibration.

  17. OASIS 1.0: Very Large-Aperture High-Power Lidar for Exploring Geospace

    NASA Astrophysics Data System (ADS)

    Chu, X.; Smith, J. A.; Chen, C.; Zhao, J.; Yu, Z.; Gardner, C. S.

    2015-12-01

    A new initiative, namely OASIS (the Observatory for Atmosphere Space Interaction Studies), has called for a very large-aperture high-power (VLAHP) lidar as its first step forward to acquire the unprecedented measurement capabilities for exploring the space-atmosphere interaction region (SAIR). Currently, there exists a serious observational gap of the Earth's neutral atmosphere above 100 km. Information on neutral winds and temperatures and on the plasma-neutral coupling in the SAIR, especially between 100 and 200 km, is either sparse or nonexistent. Fully exploring the SAIR requires measurements of the neutral atmosphere to complement radar observations of the plasma. Lidar measurements of neutral winds, temperatures and species can enable these explorations. Many of these topics will be addressed with the VLAHP lidar. Discoveries of thermospheric neutral Fe, Na and K layers up to nearly 200 km at McMurdo, Antarctica and other locations on Earth, have opened a new door to observing the neutral thermosphere with ground-based instruments. These neutral metal layers provide the tracers for resonance Doppler lidars to directly measure the neutral temperatures and winds in the thermosphere, thus enabling the VLAHP lidar dream! Because the thermospheric densities of these metal atoms are many times smaller than the layer peak densities near 90 km, high power-aperture product lidars, like the VLAHP lidar, are required to derive scientifically useful measurements. Furthermore, several key technical challenges for VLAHP lidar have been largely resolved in the last a few years through the successful development of Fe and Na Doppler lidars at Boulder. By combining Rayleigh and Raman with resonance lidar techniques and strategically operating the VLAHP lidar next to incoherent scatter radar and other complementary instruments, the VLAHP lidar will enable new cutting-edge exploration of the geospace. These new concepts and progresses will be introduced in this paper.

  18. Determining suitability of Large Aperture Scintillometer for validating remote sensing based evapotranspiration maps

    NASA Astrophysics Data System (ADS)

    Paul, G.; Gowda, P. H.; Howell, T. A.; Basu, S.; Colaizzi, P. D.; Marek, T.

    2013-12-01

    Scintillation method is a relatively new technique for measuring the sensible heat and water fluxes over land surfaces. Path integrating capabilities of scintillometer over heterogeneous landscapes make it a potential tool for comparing the energy fluxes derived from remote sensing based energy balance algorithms. For this reason, scintillometer-derived evapotranspiration (ET) fluxes are being used to evaluate remote sensing based energy balance algorithms for their ability to estimate ET fluxes. However, LAS' (Large Aperture Scintillometer) ability to derive ET fluxes is not thoroughly tested. The objective of this study was to evaluate LAS- and Surface Energy Balance System (SEBS)-derived fluxes against lysimetric data to determine LAS' suitability for validating remote sensing based evapotranspiration (ET) maps. The study was conducted during the Bushland Evapotranspiration and Agricultural Remote sensing EXperiment - 2008 (BEAREX-08) at the USDA-ARS Conservation and Production Research Laboratory (CPRL), Bushland, Texas. SEBS was coded in a GIS environment to retrieve ET fluxes from the high resolution imageries acquired using airborne multispectral sensors. The CPRL has four large weighing lysimeters (3 m long x 3 m wide x 2.4 m deep), each located in the middle of approximately 5 ha fields, arranged in a block pattern. The two lysimeter fields located on the east (NE and SE) were managed under irrigated conditions, and the other two lysimeters on the west (NW and SW) were under dryland management. Each lysimeter field was equipped with an automated weather station that provided measurements for net radiation (Rn), Ts, soil heat flux (Go), Ta, relative humidity, and wind speed. During BEAREX08, the NE and SE fields were planted to cotton on May 21, and the NW and SW dryland lysimeters fields were planted to cotton on June 5. One LAS each was deployed across two large dryland lysimeter fields (NW and SW) and two large irrigated lysimeter fields (NE and SE). The

  19. Large-aperture high-resolution x-ray collimator for the Solar Maximum Mission.

    PubMed

    Nobles, R A; Acton, L W; Joki, E G; Leibacher, J W; Peterson, R C

    1980-09-01

    A description is presented of a flight-qualified large-aperture 12 x 12-sec of arc angular resolution multigrid x-ray collimator developed for the Solar Maximum Mission (SMM) flat crystal spectrometer. This collimator, designed for the 1.4-22.4-A wavelength range, utilizes an optical bench/metering structure to align and support prealigned grid subassemblies. One advantage of this scheme is to provide ready access to the grid subassemblies for inspection and/or servicing. The optical bench is a lightweight, rigid, and stable aluminum honeycomb structure. Aluminum is a viable material choice in this application because of the good thermal control expected in the SMM instrument package. The grids are of a compound and bimetallic design, having 63.5-microm square holes on an 88.9-microm spacing in 8-microm thick gold, which is in turn supported by a 76-microm thick Invar grid having 600-microm square holes on a 739-microm spacing. The small apertures in the gold provide the 12-sec of arc collimation with the Invar grids providing wide angle off-axis blocking out to an ~35-min of arc view angle. The collimator has seven individual channels, four of a 5.1- x 10-cm area and three of a 1.3- x 10-cm area. Laboratory measurements gave an average angular resolution of 12.5-sec of arc FWHM with 0.259 transmission for the large area channels and 12.0 sec of arc and 0.200 transmission for the small area channels. A hypothetical perfectly aligned collimator would have 12.5-sec of arc resolution and 0.300 transmission. A thermal filter composed of two layers of ~1000-A thick aluminum prevents solar heating of the front collimator grids by absorbing longer wavelength radiation while passing most of the x radiation in the band of interest. The filter was flight qualified by passing a protoflight acoustic test environment of 147-dB total sound level, 20-microN/M(2) reference, for 1-min duration.

  20. Research on 2x1 plasma electrode electro-optical switch with large aperture

    NASA Astrophysics Data System (ADS)

    Zhang, Xiong Jun; Zheng, Kui Xing; Feng, B.; Wu, D. S.; Lu, J. P.; Tian, X. L.; Jin, F.; Sui, Zhan; Wei, Xiaofeng; Zhang, Xiaomin

    2005-01-01

    In conceptual design of the prototype for SG-III facility, a full aperture electro-optical switch was placed between the cavity mirror and the main amplifier to isolate the reflected beams. The beam on the cavity mirror is 240mm×240mm square. Pockells cells of conversional design with coaxial ring electrodes can not scale to such large square aperture. In the 1980s, a plasma electrode Pockels cell (PEPC) concept was invented at LLNL. It uses transparent plasma electrode formed through gas discharge as the electrodes to apply the voltage across switching crystal to rotate the polarization of a transmitted laser beam. And it can be scaled to large aperture with thin crystal. So the switch which would be used in SG-III is based on this technology. The technical integration line as a prototype of SG-III laser is actually a 4×2 beam bundle. And the full aperture optical switch is mechanically designed four apertures as a removable unit, and electrically two 2×1 PEPC putting together. So we built a 2×1 PEPC to develop the technology first. The 2×1 PEPC is a sandwich structure made of an insulating mid plane between a pair of plasma chambers. The frame of both plasma chambers are machining in duralumin. Each chamber is installed with a planar magnetic cathode and four segments spherical anodes made from stainless steel. The cathode and anode are insulated from the housing with a special shell made from plastic, and plasma is insulated from the housing by an 80-μm-thick anodic coating on the duralumin. The two plasma chambers are separated by a mid plane of glass frame with two square holes. The two holes are filled by two electro-optical crystals with a 240-mm square aperture. With the optimized operating pressure and the electrical parameters, a very good homogeneity and low resistivity plasma electrode is obtained. Finally we tested its switching performance to simulate the case that it will be used in the SG-III prototype facility. It works with a quarter wave

  1. Developing Magnetorheological Finishing (MRF) Technology for the Manufacture of Large-Aperture Optics in Megajoule Class Laser Systems

    SciTech Connect

    Menapace, J A

    2010-10-27

    Over the last eight years we have been developing advanced MRF tools and techniques to manufacture meter-scale optics for use in Megajoule class laser systems. These systems call for optics having unique characteristics that can complicate their fabrication using conventional polishing methods. First, exposure to the high-power nanosecond and sub-nanosecond pulsed laser environment in the infrared (>27 J/cm{sup 2} at 1053 nm), visible (>18 J/cm{sup 2} at 527 nm), and ultraviolet (>10 J/cm{sup 2} at 351 nm) demands ultra-precise control of optical figure and finish to avoid intensity modulation and scatter that can result in damage to the optics chain or system hardware. Second, the optics must be super-polished and virtually free of surface and subsurface flaws that can limit optic lifetime through laser-induced damage initiation and growth at the flaw sites, particularly at 351 nm. Lastly, ultra-precise optics for beam conditioning are required to control laser beam quality. These optics contain customized surface topographical structures that cannot be made using traditional fabrication processes. In this review, we will present the development and implementation of large-aperture MRF tools and techniques specifically designed to meet the demanding optical performance challenges required in large-aperture high-power laser systems. In particular, we will discuss the advances made by using MRF technology to expose and remove surface and subsurface flaws in optics during final polishing to yield optics with improve laser damage resistance, the novel application of MRF deterministic polishing to imprint complex topographical information and wavefront correction patterns onto optical surfaces, and our efforts to advance the technology to manufacture large-aperture damage resistant optics.

  2. A New Type of X-ray Condenser Lenses with Large Apertures Fabricated by Rolling of Structured Films

    SciTech Connect

    Simon, M.; Reznikova, E.; Nazmov, V.; Grund, T.; Last, A.

    2010-04-06

    In order to meet the demand for X-ray lenses with large apertures and, hence, photon flux, a new type of X-ray lenses has been developed: Rolled prismatic X-ray lenses feature a vast number of refracting surfaces to increase transparency and aperture, respectively. Prototypes of such lenses have been fabricated by molding and rolling of a structured polyimide film. In this work, rolled prismatic X-ray lenses are pictured, and results of first tests performed at the ANKA storage ring in Karlsruhe are presented.

  3. In-situ monitoring of surface post-processing in large aperture fused silica optics with Optical Coherence Tomography

    SciTech Connect

    Guss, G M; Bass, I l; Hackel, R P; Mailhiot, C; Demos, S G

    2008-02-08

    Optical Coherence Tomography is explored as a method to image laser-damage sites located on the surface of large aperture fused silica optics during post-processing via CO{sub 2} laser ablation. The signal analysis for image acquisition was adapted to meet the sensitivity requirements for this application. A long-working distance geometry was employed to allow imaging through the opposite surface of the 5-cm thick optic. The experimental results demonstrate the potential of OCT for remote monitoring of transparent material processing applications.

  4. Algorithms for finely adjusting etch depths to improve the diffraction efficiency uniformity of large-aperture BSG

    NASA Astrophysics Data System (ADS)

    Wu, Lixiang; Qiu, Keqiang; Liu, Ying; Fu, Shaojun

    2015-03-01

    Beam sampling gratings (BSGs) employed in high-power laser systems usually have large aperture so that the adequate uniformity of diffraction efficiency is difficult to obtain. We proposed a deterministic method using controllable non-uniform etch to improve the efficiency uniformity of large-aperture BSGs. During the ion beam etching (IBE) process, etch depths are finely adjusted by the dynamic leaf. The motion trajectory of the dynamic leaf is calculated using the fine adjustment algorithm. Simulations are conducted on the basis of a typical example. The simulation predictions show that the cumulative error is 0.067 nm and about 99.1% of depth differences are in the range of the required etch depth tolerance, which suggests that the diffraction efficiency uniformity of BSG is expected to be effectively improved and thus can meet the requirement of a RMS of 5%. As a cost-effective solution, it also has a broad prospect in many optical fabrication fields, especially for the fabrication of large optics.

  5. Electro-Mechanical Simulation of a Large Aperture MOEMS Fabry-Perot Tunable Filter

    NASA Technical Reports Server (NTRS)

    Kuhn, Jonathan L.; Barclay, Richard B.; Greenhouse, Matthew A.; Mott, D. Brent; Satyapal, Shobita; Powers, Edward I. (Technical Monitor)

    2000-01-01

    We are developing a micro-machined electrostatically actuated Fabry-Perot tunable filter with a large clear aperture for application in high through-put wide-field imaging spectroscopy and lidar systems. In the first phase of this effort, we are developing key components based on coupled electro-mechanical simulations. In particular, the movable etalon plate design leverages high coating stresses to yield a flat surface in drum-head tension over a large diameter (12.5 mm). In this approach, the cylindrical silicon movable plate is back etched, resulting in an optically coated membrane that is suspended from a thick silicon support ring. Understanding the interaction between the support ring, suspended membrane, and coating is critical to developing surfaces that are flat to within stringent etalon requirements. In this work, we present the simulations used to develop the movable plate, spring suspension system, and electrostatic actuation mechanism. We also present results from tests of fabricated proof of concept components.

  6. Research on precision grinding processing and compensation finishing experiment for mid-large- aperture square aspheric optical element

    NASA Astrophysics Data System (ADS)

    Nie, Fengming; Li, Zhanguo; Wang, Dasen; Zhang, Guangping; Guo, Chengjun; Pei, Ning; Li, Yupeng

    2014-08-01

    This paper analyzes dot-line envelope grinding principle, which is applicable to mid-large- aperture square aspheric optical element, determines the mathematical process control model based on X/Y/C three-axis aspheric grinding machine, We develop the appropriate high-precision aspheric grinding manufacturing and measurement systems software, using the plane grinding wheel to do the grinding experiments and the repeated compensation processing experiment. The experiments show that: high-precision aspheric grinding manufacturing and measurement systems software can be realized axisymmetric aspheric high-precision machining control and measurement; using compensation processing of the X/Y/C three-axis aspheric grinding machine which can effectively improve the precision PV value, surface error from the initial processing of the PV value :12 μm to the compensation processing of the PV value :3 μm .

  7. The Advanced Technology Large Aperture Space Telescope (ATLAST): Science Drivers, Technology Developments, and Synergies with Other Future Facilities

    NASA Technical Reports Server (NTRS)

    Postman, Marc; Brown, Tom; Sembach, Kenneth; Giavalisco, Mauro; Traub, Wesley; Stapelfeldt, Karl; Calzetti, Daniela; Oegerle, William; Rich, R. Michael; Stahl, H. Philip; Tumlinson, Jason; Mountain, Matt; Soummer, Remi; Hyde, Tupper

    2011-01-01

    The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a concept for an 8-meter to 16-meter UVOIR space observatory for launch in the 2025-2030 era. ATLAST will allow astronomers to answer fundamental questions at the forefront of modern astrophysics, including "Is there life elsewhere in the Galaxy?" We present a range of science drivers that define the main performance requirements for ATLAST (8 to 16 milliarcsec angular resolution, diffraction limited imaging at 0.5 m wavelength, minimum collecting area of 45 square meters, high sensitivity to light wavelengths from 0.1 m to 2.4 m, high stability in wavefront sensing and control). We will also discuss the synergy between ATLAST and other anticipated future facilities (e.g., TMT, EELT, ALMA) and the priorities for technology development that will enable the construction for a cost that is comparable to current generation observatory-class space missions.

  8. Design studies of large aperture, high-resolution Earth science microwave radiometers compatible with small launch vehicles

    NASA Technical Reports Server (NTRS)

    Schroeder, Lyle C.; Bailey, M. C.; Harrington, Richard F.; Kendall, Bruce M.; Campbell, Thomas G.

    1994-01-01

    High-spatial-resolution microwave radiometer sensing from space with reasonable swath widths and revisit times favors large aperture systems. However, with traditional precision antenna design, the size and weight requirements for such systems are in conflict with the need to emphasize small launch vehicles. This paper describes tradeoffs between the science requirements, basic operational parameters, and expected sensor performance for selected satellite radiometer concepts utilizing novel lightweight compactly packaged real apertures. Antenna, feed, and radiometer subsystem design and calibration are presented. Preliminary results show that novel lightweight real aperture coupled with state-of-the-art radiometer designs are compatible with small launch systems, and hold promise for high-resolution earth science measurements of sea ice, precipitation, soil moisture, sea surface temperature, and ocean wind speeds.

  9. Comparison of Turbulent Sensible Heat Flux Determined by Large-Aperture Scintillometer and Eddy Covariance over Urban and Suburban Areas

    NASA Astrophysics Data System (ADS)

    Zhang, He; Zhang, Hongsheng

    2015-01-01

    Field observations of the atmospheric boundary layer were made over urban and suburban areas in the Yangtze River Delta, China. Sensible heat fluxes were obtained by eddy-covariance (EC) systems and large-aperture scintillometers (LASs). The results indicated that (1) the sensible heat flux obtained by LAS was less noisy and slightly larger than that obtained by EC over both urban and suburban surfaces; (2) the values of were higher when the correlation coefficient of vertical wind speed and temperature () was smaller. Lower values of were due to low-frequency trends. The urban values of were smaller than suburban values at low values; (3) the sensible heat flux determined by LAS was improved by use of the Monin-Obukhov similarity theory of the temperature structure parameter over urban and suburban areas, and the improvement is more significant over urban surface areas.

  10. Active membrane cholesterol as a physiological effector.

    PubMed

    Lange, Yvonne; Steck, Theodore L

    2016-09-01

    Sterols associate preferentially with plasma membrane sphingolipids and saturated phospholipids to form stoichiometric complexes. Cholesterol in molar excess of the capacity of these polar bilayer lipids has a high accessibility and fugacity; we call this fraction active cholesterol. This review first considers how active cholesterol serves as an upstream regulator of cellular sterol homeostasis. The mechanism appears to utilize the redistribution of active cholesterol down its diffusional gradient to the endoplasmic reticulum and mitochondria, where it binds multiple effectors and directs their feedback activity. We have also reviewed a broad literature in search of a role for active cholesterol (as opposed to bulk cholesterol or lipid domains such as rafts) in the activity of diverse membrane proteins. Several systems provide such evidence, implicating, in particular, caveolin-1, various kinds of ABC-type cholesterol transporters, solute transporters, receptors and ion channels. We suggest that this larger role for active cholesterol warrants close attention and can be tested easily.

  11. Large-aperture MOEMS Fabry-Perot interferometer for miniaturized spectral imagers

    NASA Astrophysics Data System (ADS)

    Rissanen, Anna; Langner, Andreas; Viherkanto, Kai; Mannila, Rami

    2015-02-01

    VTT's optical MEMS Fabry-Perot interferometers (FPIs) are tunable optical filters, which enable miniaturization of spectral imagers into small, mass producible hand-held sensors with versatile optical measurement capabilities. FPI technology has also created a basis for various hyperspectral imaging instruments, ranging from nanosatellites, environmental sensing and precision agriculture with UAVs to instruments for skin cancer detection. Until now, these application demonstrations have been mostly realized with piezo-actuated FPIs fabricated by non-monolithical assembly method, suitable for achieving very large optical apertures and with capacity to small-to-medium volumes; however large-volume production of MEMS manufacturing supports the potential for emerging spectral imaging applications also in large-volume applications, such as in consumer/mobile products. Previously reported optical apertures of MEMS FPIs in the visible range have been up to 2 mm in size; this paper presents the design, successful fabrication and characterization of MEMS FPIs for central wavelengths of λ = 500 nm and λ = 650 nm with optical apertures up to 4 mm in diameter. The mirror membranes of the FPI structures consist of ALD (atomic layer deposited) TiO2-Al2O3 λ/4- thin film Bragg reflectors, with the air gap formed by sacrificial polymer etching in O2 plasma. The entire fabrication process is conducted below 150 °C, which makes it possible to monolithically integrate the filter structures on other ICdevices such as detectors. The realized MEMS devices are aimed for nanosatellite space application as breadboard hyperspectral imager demonstrators.

  12. New technologies for the actuation and controls of large aperture lightweight quality mirrors

    NASA Technical Reports Server (NTRS)

    Lih, S. S.; Yang, E. H.; Gullapalli, S. N.; Flood, R.

    2003-01-01

    This paper presents a set of candidate components: MEMS based large stroke (>100 microns) ultra lightweight (0.01 gm) discrete inch worm actuator technology, and a distributed actuator technology, in the context of a novel lightweight active flexure-hinged substrate concept that uses the nanolaminate face sheet.

  13. Activated Membrane Patches Guide Chemotactic Cell Motility

    PubMed Central

    Hecht, Inbal; Skoge, Monica L.; Charest, Pascale G.; Ben-Jacob, Eshel; Firtel, Richard A.; Loomis, William F.; Levine, Herbert; Rappel, Wouter-Jan

    2011-01-01

    Many eukaryotic cells are able to crawl on surfaces and guide their motility based on environmental cues. These cues are interpreted by signaling systems which couple to cell mechanics; indeed membrane protrusions in crawling cells are often accompanied by activated membrane patches, which are localized areas of increased concentration of one or more signaling components. To determine how these patches are related to cell motion, we examine the spatial localization of RasGTP in chemotaxing Dictyostelium discoideum cells under conditions where the vertical extent of the cell was restricted. Quantitative analyses of the data reveal a high degree of spatial correlation between patches of activated Ras and membrane protrusions. Based on these findings, we formulate a model for amoeboid cell motion that consists of two coupled modules. The first module utilizes a recently developed two-component reaction diffusion model that generates transient and localized areas of elevated concentration of one of the components along the membrane. The activated patches determine the location of membrane protrusions (and overall cell motion) that are computed in the second module, which also takes into account the cortical tension and the availability of protrusion resources. We show that our model is able to produce realistic amoeboid-like motion and that our numerical results are consistent with experimentally observed pseudopod dynamics. Specifically, we show that the commonly observed splitting of pseudopods can result directly from the dynamics of the signaling patches. PMID:21738453

  14. Quantitative comparison of terahertz emission from (100) InAs surfaces and a GaAs large-aperture photoconductive switch at high fluences.

    PubMed

    Reid, Matthew; Fedosejevs, Robert

    2005-01-01

    InAs has previously been reported to be an efficient emitter of terahertz radiation at low excitation fluences by use of femtosecond laser pulses. The scaling and saturation of terahertz emission from a (100) InAs surface as a function of excitation fluence is measured and quantitatively compared with the emission from a GaAs large-aperture photoconductive switch. We find that, although the instantaneous peak radiated terahertz field from (100) InAs exceeds the peak radiated signals from a GaAs large-aperture photoconductive switch biased at 1.6 kV/cm, the pulse duration is shorter. For the InAs source the total energy radiated is less than can be obtained from a GaAs large-aperture photoconductive switch.

  15. Large Aperture Acoustic Array

    DTIC Science & Technology

    1989-07-01

    1730 GMT. Several propagation models, encompassing normal mode, parabolic equation, fast field and eigenray approaches, were compared using the array... eigenray ) was chosen as the prediction vehicle due to its robust simplicity in this application where the amplitude is controlled by two dominant paths...to the program as a slant range assuming a homogeneous medium with a sound speed of 1500 in/s. This is not normally the case, and for the Septeller

  16. Spaceborne Microwave Instrument for High Resolution Remote Sensing of the Earth's Surface Using a Large-Aperture Mesh Antenna

    NASA Technical Reports Server (NTRS)

    Njoku, E.; Wilson, W.; Yueh, S.; Freeland, R.; Helms, R.; Edelstein, W.; Sadowy, G.; Farra, D.; West, R.; Oxnevad, K.

    2001-01-01

    This report describes a two-year study of a large-aperture, lightweight, deployable mesh antenna system for radiometer and radar remote sensing of the Earth from space. The study focused specifically on an instrument to measure ocean salinity and Soil moisture. Measurements of ocean salinity and soil moisture are of critical . importance in improving knowledge and prediction of key ocean and land surface processes, but are not currently obtainable from space. A mission using this instrument would be the first demonstration of deployable mesh antenna technology for remote sensing and could lead to potential applications in other remote sensing disciplines that require high spatial resolution measurements. The study concept features a rotating 6-m-diameter deployable mesh antenna, with radiometer and radar sensors, to measure microwave emission and backscatter from the Earth's surface. The sensors operate at L and S bands, with multiple polarizations and a constant look angle, scanning across a wide swath. The study included detailed analyses of science requirements, reflector and feedhorn design and performance, microwave emissivity measurements of mesh samples, design and test of lightweight radar electronic., launch vehicle accommodations, rotational dynamics simulations, and an analysis of attitude control issues associated with the antenna and spacecraft, The goal of the study was to advance the technology readiness of the overall concept to a level appropriate for an Earth science emission.

  17. Cavity-excited Huygens' metasurface antennas for near-unity aperture illumination efficiency from arbitrarily large apertures.

    PubMed

    Epstein, Ariel; Wong, Joseph P S; Eleftheriades, George V

    2016-01-21

    One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators.

  18. DM/LCWFC based adaptive optics system for large aperture telescopes imaging from visible to infrared waveband.

    PubMed

    Sun, Fei; Cao, Zhaoliang; Wang, Yukun; Zhang, Caihua; Zhang, Xingyun; Liu, Yong; Mu, Quanquan; Xuan, Li

    2016-11-28

    Almost all the deformable mirror (DM) based adaptive optics systems (AOSs) used on large aperture telescopes work at the infrared waveband due to the limitation of the number of actuators. To extend the imaging waveband to the visible, we propose a DM and Liquid crystal wavefront corrector (DM/LCWFC) combination AOS. The LCWFC is used to correct the high frequency aberration corresponding to the visible waveband and the aberrations of the infrared are corrected by the DM. The calculated results show that, to a 10 m telescope, DM/LCWFC AOS which contains a 1538 actuators DM and a 404 × 404 pixels LCWFC is equivalent to a DM based AOS with 4057 actuators. It indicates that the DM/LCWFC AOS is possible to work from visible to infrared for larger aperture telescopes. The simulations and laboratory experiment are performed for a 2 m telescope. The experimental results show that, after correction, near diffraction limited resolution USAF target images are obtained at the wavebands of 0.7-0.9 μm, 0.9-1.5 μm and 1.5-1.7 μm respectively. Therefore, the DM/LCWFC AOS may be used to extend imaging waveband of larger aperture telescope to the visible. It is very appropriate for the observation of spatial objects and the scientific research in astronomy.

  19. Seasonal variability of turbulent fluxes over a vegetated subtropical coastal wetland measured by large aperture scintillometry and eddy covariance

    NASA Astrophysics Data System (ADS)

    Guyot, Adrien; Gray, Michael; Riesenkamp, Michiel; Lockington, David; McGowan, Hamish

    2016-04-01

    Subtropical coastal wetlands are particularly susceptible to the impacts of climate variability: their recharge rates strongly depend on rainfall, and the occurrence of prolonged droughts or wet periods have direct consequences for wetland health and bio-diversity. There is therefore a need to close the water budget of these ecosystems and this requires the quantification of rates of evaporation/evapotranspiration. However, few studies have documented land-atmosphere exchanges over wetlands for which water level varies considerably during a typical annual cycle. Here, we present a year of turbulent flux observations over a wetland on the subtropical coast of eastern Australia. Large Aperture Scintillometry and Eddy Covariance are used to derive sensible heat fluxes. Latent heat fluxes are also derived through an energy balance for both instruments' observations and also directly through Eddy Covariance. Careful sensitivity analysis of the instrumental footprints, seasonal variations of land surface parameters such as roughness length and displacement height are examined and subsequent uncertainties in the derived turbulent fluxes are discussed. Finally we show how these observations can also help better understand hydrological processes at the catchment scale.

  20. Cavity-excited Huygens' metasurface antennas for near-unity aperture illumination efficiency from arbitrarily large apertures

    PubMed Central

    Epstein, Ariel; Wong, Joseph P. S.; Eleftheriades, George V.

    2016-01-01

    One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators. PMID:26790605

  1. LUPUS I observations from the 2010 flight of the Balloon-borne large aperture submillimeter telescope for polarimetry

    SciTech Connect

    Matthews, Tristan G.; Chapman, Nicholas L.; Novak, Giles; Ade, Peter A. R.; Hargrave, Peter C.; Nutter, David; Angilè, Francesco E.; Devlin, Mark J.; Klein, Jeffrey; Benton, Steven J.; Fissel, Laura M.; Gandilo, Natalie N.; Netterfield, Calvin B.; Chapin, Edward L.; Fukui, Yasuo; Gundersen, Joshua O.; Korotkov, Andrei L.; Moncelsi, Lorenzo; Mroczkowski, Tony K.; Olmi, Luca; and others

    2014-04-01

    The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) was created by adding polarimetric capability to the BLAST experiment that was flown in 2003, 2005, and 2006. BLASTPol inherited BLAST's 1.8 m primary and its Herschel/SPIRE heritage focal plane that allows simultaneous observation at 250, 350, and 500 μm. We flew BLASTPol in 2010 and again in 2012. Both were long duration Antarctic flights. Here we present polarimetry of the nearby filamentary dark cloud Lupus I obtained during the 2010 flight. Despite limitations imposed by the effects of a damaged optical component, we were able to clearly detect submillimeter polarization on degree scales. We compare the resulting BLASTPol magnetic field map with a similar map made via optical polarimetry. (The optical data were published in 1998 by J. Rizzo and collaborators.) The two maps partially overlap and are reasonably consistent with one another. We compare these magnetic field maps to the orientations of filaments in Lupus I, and we find that the dominant filament in the cloud is approximately perpendicular to the large-scale field, while secondary filaments appear to run parallel to the magnetic fields in their vicinities. This is similar to what is observed in Serpens South via near-IR polarimetry, and consistent with what is seen in MHD simulations by F. Nakamura and Z. Li.

  2. A fundamental mode Nd:GdVO4 laser pumped by a large aperture 808 nm VCSEL

    NASA Astrophysics Data System (ADS)

    Hao, Y. Q.; Ma, J. L.; Yan, C. L.; Liu, G. J.; Ma, X. H.; Gong, J. F.; Feng, Y.; Wei, Z. P.; Wang, Y. X.; Zhao, Y. J.

    2013-05-01

    A fundamental mode Nd:GdVO4 laser pumped by a vertical cavity surface emitting laser (VCSEL) is experimentally demonstrated. The VCSEL has a circular output-beam which makes it easier for it to be directly coupled to a Nd:GdVO4 microcrystal. In our research, a large aperture 808 nm VCSEL, with a multi-ring-shaped aperture (MRSA) and an almost Gaussian-shaped far-field profile, is used as the pumping source. Experimental results for the Nd:GdVO4 laser pumped by the VCSEL are presented. The maximum output peak power of 0.754 W is obtained under a pump peak power of 1.3 W, and the corresponding opto-optic conversion efficiency is 58.1%. The average slope efficiency is 65.8% from the threshold pump power of 0.2 W to the pump power of 1.3 W. The laser beam quality factors are measured to be {M}x2=1.2 0 and {M}y2=1.1 5.

  3. MRF Applications: On the Road to Making Large-Aperture Ultraviolet Laser Resistant Continuous Phase Plates for High-Power Lasers

    SciTech Connect

    Menapace, J A; Davis, P J; Steele, W A; Hachkowski, M R; Nelson, A; Xin, K

    2006-10-26

    Over the past two years we have developed MRF tools and procedures to manufacture large-aperture (430 X 430 mm) continuous phase plates (CPPs) that are capable of operating in the infrared portion (1053 nm) of high-power laser systems. This is accomplished by polishing prescribed patterns of continuously varying topographical features onto finished plano optics using MRF imprinting techniques. We have been successful in making, testing, and using large-aperture CPPs whose topography possesses spatial periods as low as 4 mm and surface peak-to-valleys as high as 8.6 {micro}m. Combining this application of MRF technology with advanced MRF finishing techniques that focus on ultraviolet laser damage resistance makes it potentially feasible to manufacture large-aperture CPPs that can operate in the ultraviolet (351 nm) without sustaining laser-induced damage. In this paper, we will discuss the CPP manufacturing process and the results of 351-nm/3-nsec equivalent laser performance experiments conducted on large-aperture CPPs manufactured using advanced MRF protocols.

  4. Estimation of turbulent sensible heat and momentum fluxes over a heterogeneous urban area using a large aperture scintillometer

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Hyun; Lee, Jun-Ho; Kim, Bo-Young

    2015-08-01

    The accurate determination of surface-layer turbulent fluxes over urban areas is critical to understanding urban boundary layer (UBL) evolution. In this study, a remote-sensing technique using a large aperture scintillometer (LAS) was investigated to estimate surface-layer turbulent fluxes over a highly heterogeneous urban area. The LAS system, with an optical path length of 2.1 km, was deployed in an urban area characterized by a complicated land-use mix (residential houses, water body, bare ground, etc.). The turbulent sensible heat ( Q H) and momentum fluxes (τ) were estimated from the scintillation measurements obtained from the LAS system during the cold season. Three-dimensional LAS footprint modeling was introduced to identify the source areas ("footprint") of the estimated turbulent fluxes. The analysis results showed that the LAS-derived turbulent fluxes for the highly heterogeneous urban area revealed reasonable temporal variation during daytime on clear days, in comparison to the land-surface process-resolving numerical modeling. A series of sensitivity tests indicated that the overall uncertainty in the LAS-derived daytime Q H was within 20%-30% in terms of the influence of input parameters and the nondimensional similarity function for the temperature structure function parameter, while the estimation errors in τ were less sensitive to the factors of influence, except aerodynamic roughness length. The 3D LAS footprint modeling characterized the source areas of the LAS-derived turbulent fluxes in the heterogeneous urban area, revealing that the representative spatial scales of the LAS system deployed with the 2.1 km optical path distance ranged from 0.2 to 2 km2 (a "micro- a scale"), depending on local meteorological conditions.

  5. Architectural study of active membrane antennas

    NASA Technical Reports Server (NTRS)

    Moussessian, A.; DiDomenico, L.; Edelstein, W.

    2002-01-01

    One method to dramatically reduce the weight, volume and associated cost of space-based SyntheticAperture Radars (SAR) is to replace the conventional rigid manifold antenna architecture with a flexible thin-film membrane. This has been successfully demonstrated as a passive array. To further reduce the cost and weight and provide 2D scanning required by space-based applications we also need to integrate the Transmit/Receive (TR) function into the inflatable antenna elements. This paper explores the constraints that must be placed on the active electronics of a flexible antenna array as well as some of the preliminary work in this area.

  6. Large-Aperture [O I] 6300 A Photometry of Comet Hale-Bopp: Implications for the Photochemistry of OH

    NASA Technical Reports Server (NTRS)

    Morgenthaler, Jeffrey P.; Harris, Walter M.; Scherb, Frank; Anderson, Christopher M.; Oliversen, Ronald J.; Doane, Nathaniel E.; Combi, Michael R.; Marconi, Maximus L.; Smyth, William H.

    2001-01-01

    Large-aperture photometric observations of comet Hale-Bopp (C/1995 O1) in the forbidden red line of neutral oxygen ([O I] 6300 angstroms) with the 150 mm dual-etalon Fabry-Perot spectrometer that comprises the Wisconsin H-alpha Mapper and a 50 mm dual-etalon Fabry-Perot spectrometer at the McMath-Pierce main telescope from 1997 late February to mid April yield a total metastable O((sup 1)D) production rate of (2.3-5.9) x 10(exp 30)/s. Applying the standard H2O and OH photodissociation branching ratios, we derive a water production rate, Q(H2O), of (2.6-6.1) x 10(exp 31)/s, which disagrees with Q(H2O = 1x10(exp 31)/s determined by independent H2O, OH, and H measurements. Furthermore, our own [O I] 6300 observations of the inner coma (< 30,000 km) using the 3.5 m Wisconsin-Indiana-Yale-NOAO telescope Hydra and Densepak multi-object spectrographs yield Q(H2O) = 1 x 10(exp 31)/s. Using our [O I] 6300 data, which cover spatial scales ranging from 2,000 to 1x10(exp 6) km, and a complementary set of wide-field ground-based OH images, we can constrain the sources of the apparent excess O((sup 1)D) emission to the outer coma, where photodissociation of OH is assumed to be the dominant O((sup 1)D) production mechanism. From production rates of other oxygen-bearing volatiles (e.g., CO and CO2), we can account for at most 30% of the observed excess O((sup 1)D) emission. Since even less O((sup 1)D) should be coming from other sources (e.g., electron excitation of neutral O and distributed nonnuclear sources of H2O), we hypothesize that the bulk of the excess O((sup 1)D) is likely coming from photodissociating OH. Using the experimental OH photo-dissociation cross section of Nee and Lee at Ly-alpha as a guide in modifying the theoretical OH cross sections of van Dishoeck and Dalgarno, we can account for approximately 60% of the observed O((sup 1)D) excess without requiring major modifications to the other OH branching ratios or the total OH photodissociation lifetime.

  7. Estimating Evapotranspiration over Heterogeneously Vegetated Surfaces using Large Aperture Scintillometer, LiDAR, and Airborne Multispectral Imagery

    NASA Astrophysics Data System (ADS)

    Geli, H. M.; Neale, C. M.; Pack, R. T.; Watts, D. R.; Osterberg, J.

    2011-12-01

    Estimates of evapotranspiration (ET) over heterogeneous areas is challenging especially in water-limited sparsely vegetated environments. New techniques such as airborne full-waveform LiDAR (Light Detection and Ranging) and high resolution multispectral and thermal imagery can provide enough detail of sparse canopies to improve energy balance model estimations as well as footprint analysis of scintillometer data. The objectives of this study were to estimate ET over such areas and develop methodologies for the use of these airborne data technologies. Because of the associated heterogeneity, this study was conducted over the Cibola National wildlife refuge, southern California on an area dominated with tamarisk (salt cedar) forest (90%) interspersed with arrowweed and bare soil (10%). A set of two large aperture scintillometers (LASs) were deployed over the area to provide estimates of sensible heat flux (HLAS). The LASs were distributed over the area in a way that allowed capturing different surface spatial heterogeneity. Bowen ratio systems were used to provide hydrometeorological variables and surface energy balance fluxes (SEBF) (i.e. Rn, G, H, and LE) measurements. Scintillometer-based estimates of HLAS were improved by considering the effect of the corresponding 3D footprint and the associated displacement height (d) and the roughness length (z0) following Geli et al. (2011). The LiDAR data were acquired using the LASSI Lidar developed at Utah State University (USU). The data was used to obtain 1-m spatial resolution DEM's and vegetation canopy height to improve the HLAS estimates. The BR measurements of Rn and G were combined with LAS estimates, HLAS, to provide estimates of LELASas a residual of the energy balance equation. A thermal remote sensing model namely the two source energy balance (TSEB) of Norman et al. (1995) was applied to provide spatial estimates of SEBF. Four airborne images at 1-4 meter spatial resolution acquired using the USU airborne

  8. Cable theory in neurons with active, linearized membranes.

    PubMed

    Koch, C

    1984-01-01

    This investigation aims at exploring some of the functional consequences of single neurons containing active, voltage dependent channels for information processing. Assuming that the voltage change in the dendritic tree of these neurons does not exceed a few millivolts, it is possible to linearize the non-linear channel conductance. The membrane can then be described in terms of resistances, capacitances and inductances, as for instance in the small-signal analysis of the squid giant axon. Depending on the channel kinetics and the associated ionic battery the linearization yields two basic types of membrane: a membrane modeled by a collection of resistances and capacitances and membranes containing in addition to these components inductances. Under certain specified conditions the latter type of membrane gives rise to a membrane impedance that displays a prominent maximum at some nonzero resonant frequency fmax. We call this type of membrane quasi-active, setting it apart from the usual passive membrane. We study the linearized behaviour of active channels giving rise to quasi-active membranes in extended neuronal structures and consider several instances where such membranes may subserve neuronal function: 1. The resonant frequency of a quasi-active membrane increases with increasing density of active channels. This might be one of the biophysical mechanisms generating the large range over which hair cells in the vertebrate cochlea display frequency tuning. 2. The voltage recorded from a cable with a quasi-active membrane can be proportional to the temporal derivative of the injected current. 3. We modeled a highly branched dendritic tree (delta-ganglion cell of the cat retina) using a quasi-active membrane. The voltage attenuation from a given synaptic site to the soma decreases with increasing frequency up to the resonant frequency, in sharp contrast to the behaviour of passive membranes.(ABSTRACT TRUNCATED AT 400 WORDS)

  9. Lipase immobilized catalytically active membrane for synthesis of lauryl stearate in a pervaporation membrane reactor.

    PubMed

    Zhang, Weidong; Qing, Weihua; Ren, Zhongqi; Li, Wei; Chen, Jiangrong

    2014-11-01

    A composite catalytically active membrane immobilized with Candida rugosa lipase has been prepared by immersion phase inversion technique for enzymatic synthesis of lauryl stearate in a pervaporation membrane reactor. SEM images showed that a "sandwich-like" membrane structure with a porous lipase-PVA catalytic layer uniformly coated on a polyvinyl alcohol (PVA)/polyethersulfone (PES) bilayer was obtained. Optimum conditions for lipase immobilization in the catalytic layer were determined. The membrane was proved to exhibit superior thermal stability, pH stability and reusability than free lipase under similar conditions. In the case of pervaporation coupled synthesis of lauryl stearate, benefited from in-situ water removal by the membrane, a conversion enhancement of approximately 40% was achieved in comparison to the equilibrium conversion obtained in batch reactors. In addition to conversion enhancement, it was also found that excess water removal by the catalytically active membrane appears to improve activity of the lipase immobilized.

  10. The evolution of endothermy: role for membranes and molecular activity.

    PubMed

    Else, Paul L; Turner, N; Hulbert, A J

    2004-01-01

    On the basis of the comparative approach and three models of metabolism (endothermic and ectothermic vertebrates, body mass, and mammalian development), we suggest that a few common cellular processes, linked either directly or indirectly to membranes, consume the majority of energy used by most organisms; that membranes act as pacemakers of metabolism through changes in lipid composition, altering membrane characteristics and the working environment of membrane proteins--specifically, that changes in the membrane environment similarly affect the molecular activities (specific rates of activity) of membrane-bound proteins; and that polyunsaturation of membranes increases whereas monounsaturation decreases the activity of membrane proteins. Experiments designed to test this theory using the sodium pump support this supposition. Potential mechanisms considered include fluidity, electrical fields, and related surface area requirements of lipids. In considering the evolution of endothermy in mammals, for example, if the first mammals were small, possibly nocturnal and active organisms, all these factors would favour increased polyunsaturation of membranes. Such changes (from monounsaturated to polyunsaturated membranes) would allow membranes to set the pace of metabolism in the evolution of endothermy.

  11. Magnetically Activated Self-Cleaning Membranes

    DTIC Science & Technology

    2010-06-01

    available nanofiltration membranes were modified by growing polymer brushes from the surface of the membrane. Two different polymerization methods have been...dimethylaminopyridine DMF: n,n-dimethylformamide EDC: 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide HEMA: 2-hydroxyethylmethacrylate NF: Nanofiltration NHS... nanofiltration , oily wastewaters, rejection, superparamagnetic nanoparticles Acknowledgements The financial support of the Strategic Environmental Research

  12. Influence of membrane lipid composition on flavonoid-membrane interactions: Implications on their biological activity.

    PubMed

    Selvaraj, Stalin; Krishnaswamy, Sridharan; Devashya, Venkappayya; Sethuraman, Swaminathan; Krishnan, Uma Maheswari

    2015-04-01

    The membrane interactions and localization of flavonoids play a vital role in altering membrane-mediated cell signaling cascades as well as influence the pharmacological activities such as anti-tumour, anti-microbial and anti-oxidant properties of flavonoids. Various techniques have been used to investigate the membrane interaction of flavonoids. These include partition coefficient, fluorescence anisotropy, differential scanning calorimetry, NMR spectroscopy, electrophysiological methods and molecular dynamics simulations. Each technique will provide specific information about either alteration of membrane fluidity or localization of flavonoids within the lipid bilayer. Apart from the diverse techniques employed, the concentrations of flavonoids and lipid membrane composition employed in various studies reported in literature also are different and together these variables contribute to diverse findings that sometimes contradict each other. This review highlights different techniques employed to investigate the membrane interaction of flavonoids with special emphasis on erythrocyte model membrane systems and their significance in understanding the nature and extent of flavonoid-membrane interactions. We also attempt to correlate the membrane localization and alteration in membrane fluidity with the biological activities of flavonoids such as anti-oxidant, anti-cancer and anti-microbial properties.

  13. Technology Development for the Advanced Technology Large Aperture Space Telescope (ATLAST) as a Candidate Large UV-Optical-Infrared (LUVOIR) Surveyor

    NASA Technical Reports Server (NTRS)

    Bolcar, Matthew R.; Balasubramanian, Kunjithapatha; Clampin, Mark; Crooke, Julie; Feinberg, Lee; Postman, Marc; Quijada, Manuel; Rauscher, Bernard; Redding, David; Rioux, Norman; Shaklan, Stuart; Stahl, H. Philip; Stahle, Carl; Thronson, Harley

    2015-01-01

    The Advanced Technology Large Aperture Space Telescope (ATLAST) team has identified five key technologies to enable candidate architectures for the future large-aperture ultraviolet/optical/infrared (LUVOIR) space observatory envisioned by the NASA Astrophysics 30-year roadmap, Enduring Quests, Daring Visions. The science goals of ATLAST address a broad range of astrophysical questions from early galaxy and star formation to the processes that contributed to the formation of life on Earth, combining general astrophysics with direct-imaging and spectroscopy of habitable exoplanets. The key technologies are: internal coronagraphs, starshades (or external occulters), ultra-stable large-aperture telescopes, detectors, and mirror coatings. Selected technology performance goals include: 1x10?10 raw contrast at an inner working angle of 35 milli-arcseconds, wavefront error stability on the order of 10 pm RMS per wavefront control step, autonomous on-board sensing & control, and zero-read-noise single-photon detectors spanning the exoplanet science bandpass between 400 nm and 1.8 µm. Development of these technologies will provide significant advances over current and planned observatories in terms of sensitivity, angular resolution, stability, and high-contrast imaging. The science goals of ATLAST are presented and flowed down to top-level telescope and instrument performance requirements in the context of a reference architecture: a 10-meter-class, segmented aperture telescope operating at room temperature (290 K) at the sun-Earth Lagrange-2 point. For each technology area, we define best estimates of required capabilities, current state-of-the-art performance, and current Technology Readiness Level (TRL) - thus identifying the current technology gap. We report on current, planned, or recommended efforts to develop each technology to TRL 5.

  14. Technology development for the Advanced Technology Large Aperture Space Telescope (ATLAST) as a candidate large UV-Optical-Infrared (LUVOIR) surveyor

    NASA Astrophysics Data System (ADS)

    Bolcar, Matthew R.; Balasubramanian, Kunjithapatham; Clampin, Mark; Crooke, Julie; Feinberg, Lee; Postman, Marc; Quijada, Manuel; Rauscher, Bernard; Redding, David; Rioux, Norman; Shaklan, Stuart; Stahl, H. Philip; Stahle, Carl; Thronson, Harley

    2015-09-01

    The Advanced Technology Large Aperture Space Telescope (ATLAST) team has identified five key technologies to enable candidate architectures for the future large-aperture ultraviolet/optical/infrared (LUVOIR) space observatory envisioned by the NASA Astrophysics 30-year roadmap, Enduring Quests, Daring Visions. The science goals of ATLAST address a broad range of astrophysical questions from early galaxy and star formation to the processes that contributed to the formation of life on Earth, combining general astrophysics with direct-imaging and spectroscopy of habitable exoplanets. The key technologies are: internal coronagraphs, starshades (or external occulters), ultra-stable large-aperture telescopes, detectors, and mirror coatings. Selected technology performance goals include: 1x10-10 raw contrast at an inner working angle of 35 milli-arcseconds, wavefront error stability on the order of 10 pm RMS per wavefront control step, autonomous on-board sensing and control, and zero-read-noise single-photon detectors spanning the exoplanet science bandpass between 400 nm and 1.8 μm. Development of these technologies will provide significant advances over current and planned observatories in terms of sensitivity, angular resolution, stability, and high-contrast imaging. The science goals of ATLAST are presented and flowed down to top-level telescope and instrument performance requirements in the context of a reference architecture: a 10-meter-class, segmented aperture telescope operating at room temperature (~290 K) at the sun-Earth Lagrange-2 point. For each technology area, we define best estimates of required capabilities, current state-of-the-art performance, and current Technology Readiness Level (TRL) - thus identifying the current technology gap. We report on current, planned, or recommended efforts to develop each technology to TRL 5.

  15. Comparison of CNES spherical and NASA hemispherical large aperture integrating sources. I - Using a laboratory transfer spectroradiometer. II - Using the SPOT-2 satellite instruments

    NASA Technical Reports Server (NTRS)

    Guenther, B.; Mclean, J.; Leroy, M.; Henry, P.

    1990-01-01

    CNES spherical and NASA hemispherical large aperture calibration sources are examined using a laboratory transfer spectroradiometer and SPOT-2 instruments. The sources, collected at Matra in France during October 1987, are compared in terms of absolute calibration, linearity, and uniformity. The laboratory transfer spectroradiometer data reveal that the calibration results correspond to within about 7 percent absolute accuracy level and the linearity of the CNES source with lamp level is good. It is observed using the satellite data that both sources have an excellent uniformity over a 4 deg field of view.

  16. Plane-polar Fresnel and far-field computations using the Fresnel-Wilcox and Jacobi-Bessel expansions. [for large aperture antennas

    NASA Technical Reports Server (NTRS)

    Rahmat-Samii, Y.; Galindo-Israel, V.

    1981-01-01

    It is pointed out that the computation of the Fresnel fields for large aperture antennas is significant for many applications. The present investigation is concerned with an approach for the effective utilization of the coefficients of the Jacobi-Bessel series for the far-field to obtain an analytically continuous representation of the antenna field which is valid from the Fresnel region into the far field. Attention is given to exact formulations and closed form solutions, Fresnel and Fresnel small angle approximations, aspects of field expansion, the accuracy of the Fresnel and Fresnel small angle approximations, and the Jacobi-Bessel expansion applied to the Fresnel small angle approximation.

  17. The Structural Basis of Cholesterol Activity in Membranes

    SciTech Connect

    Olsen, Brett N.; Bielska, Agata; Lee, Tiffany; Daily, Michael D.; Covey, Douglas F.; Schlesinger, Paul H.; Baker, Nathan A.; Ory, Daniel S.

    2013-10-15

    Although the majority of free cellular cholesterol is present in the plasma membrane, cholesterol homeostasis is principally regulated through sterol-sensing proteins that reside in the cholesterol-poor endoplasmic reticulum (ER). In response to acute cholesterol loading or depletion, there is rapid equilibration between the ER and plasma membrane cholesterol pools, suggesting a biophysical model in which the availability of plasma membrane cholesterol for trafficking to internal membranes modulates ER membrane behavior. Previous studies have predominantly examined cholesterol availability in terms of binding to extramembrane acceptors, but have provided limited insight into the structural changes underlying cholesterol activation. In this study, we use both molecular dynamics simulations and experimental membrane systems to examine the behavior of cholesterol in membrane bilayers. We find that cholesterol depth within the bilayer provides a reasonable structural metric for cholesterol availability and that this is correlated with cholesterol-acceptor binding. Further, the distribution of cholesterol availability in our simulations is continuous rather than divided into distinct available and unavailable pools. This data provide support for a revised cholesterol activation model in which activation is driven not by saturation of membrane-cholesterol interactions but rather by bulk membrane remodeling that reduces membrane-cholesterol affinity.

  18. Development of active-transport membrane devices

    SciTech Connect

    Laciak, D.V.

    1994-07-01

    This report introduces the concept of Air Products` AT membranes for the separation of NH{sub 3} and CO{sub 2} from process gas streams and presents results from the first year fabrication concept development studies.

  19. Active membrane having uniform physico-chemically functionalized ion channels

    DOEpatents

    Gerald, II, Rex E; Ruscic, Katarina J; Sears, Devin N; Smith, Luis J; Klingler, Robert J; Rathke, Jerome W

    2012-09-24

    The present invention relates to a physicochemically-active porous membrane for electrochemical cells that purports dual functions: an electronic insulator (separator) and a unidirectional ion-transporter (electrolyte). The electrochemical cell membrane is activated for the transport of ions by contiguous ion coordination sites on the interior two-dimensional surfaces of the trans-membrane unidirectional pores. One dimension of the pore surface has a macroscopic length (1 nm-1000 .mu.m) and is directed parallel to the direction of an electric field, which is produced between the cathode and the anode electrodes of an electrochemical cell. The membrane material is designed to have physicochemical interaction with ions. Control of the extent of the interactions between the ions and the interior pore walls of the membrane and other materials, chemicals, or structures contained within the pores provides adjustability of the ionic conductivity of the membrane.

  20. Relationship between peptide membrane curvature generation and bactericidal activities

    NASA Astrophysics Data System (ADS)

    Schmidt, Nathan; Lee, Michelle; Kuo, David; Ouellette, Andre; Wong, Gerard

    2013-03-01

    Many amphipathic peptides and amphipathic domains in proteins can restructure biological membranes. Two examples are host defense antimicrobial peptides (AMPs) which disrupt and destabilize the cell membranes of microbes, and apolipoproteins which help stabilize nanoscale lipid aggregates. We use complementary x-ray and bacterial cell assays to elucidate the molecular length scale membrane deformations generated by amphipathic peptides with different structural motifs and relate these deformations to their activities on bacteria. Small angle x-ray scattering is used to study the interactions of model membranes with prototypical AMPs and consensus peptides from the amphipathic domains in apolipoproteins. By characterizing the nanoscale curvature deformations induced by these two distinct classes of membrane restructuring peptides we will discuss the role of amino acid composition on curvature generation. Bactericidal assays are used to access the in vivo activities of different amphipathic peptide motifs in order to understand the relationships between cell viability and membrane curvature generation.

  1. Research on the technique of large-aperture off-axis parabolic surface processing using tri-station machine and its applicability.

    PubMed

    Zhang, Xin; Luo, Xiao; Hu, Haixiang; Zhang, Xuejun

    2015-09-01

    In order to process large-aperture aspherical mirrors, we designed and constructed a tri-station machine processing center with a three station device, which bears vectored feed motion of up to 10 axes. Based on this processing center, an aspherical mirror-processing model is proposed, in which each station implements traversal processing of large-aperture aspherical mirrors using only two axes, while the stations are switchable, thus lowering cost and enhancing processing efficiency. The applicability of the tri-station machine is also analyzed. At the same time, a simple and efficient zero-calibration method for processing is proposed. To validate the processing model, using our processing center, we processed an off-axis parabolic SiC mirror with an aperture diameter of 1450 mm. The experimental results indicate that, with a one-step iterative process, the peak to valley (PV) and root mean square (RMS) of the mirror converged from 3.441 and 0.5203 μm to 2.637 and 0.2962 μm, respectively, where the RMS reduced by 43%. The validity and high accuracy of the model are thereby demonstrated.

  2. Mechanical properties that influence antimicrobial peptide activity in lipid membranes.

    PubMed

    Marín-Medina, Nathaly; Ramírez, Diego Alejandro; Trier, Steve; Leidy, Chad

    2016-12-01

    Antimicrobial peptides are small amphiphilic proteins found in animals and plants as essential components of the innate immune system and whose function is to control bacterial infectious activity. In order to accomplish their function, antimicrobial peptides use different mechanisms of action which have been deeply studied in view of their potential exploitation to treat antibiotic-resistant bacterial infections. One of the main mechanisms of action of these peptides is the disruption of the bacterial membrane through pore formation, which, in some cases, takes place via a monomer to oligomer cooperative transition. Previous studies have shown that lipid composition, and the presence of exogenous components, such as cholesterol in model membranes or carotenoids in bacteria, can affect the potency of distinct antimicrobial peptides. At the same time, considering the membrane as a two-dimensional material, it has been shown that membrane composition defines its mechanical properties which might be relevant in many membrane-related processes. Nevertheless, the correlation between the mechanical properties of the membrane and antimicrobial peptide potency has not been considered according to the importance it deserves. The relevance of these mechanical properties in membrane deformation due to peptide insertion is reviewed here for different types of pores in order to elucidate if indeed membrane composition affects antimicrobial peptide activity by modulation of the mechanical properties of the membrane. This would also provide a better understanding of the mechanisms used by bacteria to overcome antimicrobial peptide activity.

  3. Effect of activated sludge properties and membrane operation conditions on fouling characteristics in membrane bioreactors.

    PubMed

    Choi, Hyeok; Zhang, Kai; Dionysiou, Dionysios D; Oerther, Daniel B; Sorial, George A

    2006-06-01

    Biofouling control is considered to be a major challenge in operating membrane bioreactors (MBRs) for the treatment of wastewater. This study examined the impact of biological, chemical, and physical properties of activated sludge on membrane filtration performance in laboratory-scale MBRs. Sludges with different microbial communities were produced using pseudo-continuous stirred-tank reactors and pseudo-plug flow reactors treating a synthetic paper mill wastewater. Various filtration resistances were used to investigate membrane fouling characteristics, and molecular biology tools targeting 16S ribosomal DNA gene sequences were used to identify predominant bacterial populations in the sludges or attached to the fouled membranes. Filtration experiments using axenic cultures of Escherichia coli, Acinetobacter calcoaceticus, and Gordonia amarae were also performed to better understand the initiation and development of biofouling. The results showed that the tendency of membranes to biofoul depended upon membrane operating conditions as well as the properties of the activated sludge in the MBR systems. Specific bacterial populations, which were not dominant in the activated sludges, were selectively accumulated on the membrane surface leading to the development of irreversible biofouling.

  4. A common landscape for membrane-active peptides

    PubMed Central

    Last, Nicholas B; Schlamadinger, Diana E; Miranker, Andrew D

    2013-01-01

    Three families of membrane-active peptides are commonly found in nature and are classified according to their initial apparent activity. Antimicrobial peptides are ancient components of the innate immune system and typically act by disruption of microbial membranes leading to cell death. Amyloid peptides contribute to the pathology of diverse diseases from Alzheimer's to type II diabetes. Preamyloid states of these peptides can act as toxins by binding to and permeabilizing cellular membranes. Cell-penetrating peptides are natural or engineered short sequences that can spontaneously translocate across a membrane. Despite these differences in classification, many similarities in sequence, structure, and activity suggest that peptides from all three classes act through a small, common set of physical principles. Namely, these peptides alter the Brownian properties of phospholipid bilayers, enhancing the sampling of intrinsic fluctuations that include membrane defects. A complete energy landscape for such systems can be described by the innate membrane properties, differential partition, and the associated kinetics of peptides dividing between surface and defect regions of the bilayer. The goal of this review is to argue that the activities of these membrane-active families of peptides simply represent different facets of what is a shared energy landscape. PMID:23649542

  5. An Extended Membrane System with Active Membranes to Solve Automatic Fuzzy Clustering Problems.

    PubMed

    Peng, Hong; Wang, Jun; Shi, Peng; Pérez-Jiménez, Mario J; Riscos-Núñez, Agustín

    2016-05-01

    This paper focuses on automatic fuzzy clustering problem and proposes a novel automatic fuzzy clustering method that employs an extended membrane system with active membranes that has been designed as its computing framework. The extended membrane system has a dynamic membrane structure; since membranes can evolve, it is particularly suitable for processing the automatic fuzzy clustering problem. A modification of a differential evolution (DE) mechanism was developed as evolution rules for objects according to membrane structure and object communication mechanisms. Under the control of both the object's evolution-communication mechanism and the membrane evolution mechanism, the extended membrane system can effectively determine the most appropriate number of clusters as well as the corresponding optimal cluster centers. The proposed method was evaluated over 13 benchmark problems and was compared with four state-of-the-art automatic clustering methods, two recently developed clustering methods and six classification techniques. The comparison results demonstrate the superiority of the proposed method in terms of effectiveness and robustness.

  6. Structural Model of Active Bax at the Membrane

    PubMed Central

    Bleicken, Stephanie; Jeschke, Gunnar; Stegmueller, Carolin; Salvador-Gallego, Raquel; García-Sáez, Ana J.; Bordignon, Enrica

    2016-01-01

    Bax plays a central role in the mitochondrial pathway of apoptosis. Upon activation, cytosolic Bax monomers oligomerize on the surface of mitochondria and change conformation concertedly to punch holes into the outer membrane. The subsequent release of cytochrome c initiates cell death. However, the structure of membrane-inserted Bax and its mechanism of action remain largely unknown. Here, we propose a 3D model of active Bax at the membrane based on double electron-electron resonance (DEER) spectroscopy in liposomes and isolated mitochondria. We show that active Bax is organized at the membrane as assemblies of dimers. In addition to a stable dimerization domain, each monomer contains a more flexible piercing domain involved in interdimer interactions and pore formation. The most important structural change during Bax activation is the opening of the hairpin formed by helices 5 and 6, which adopts a clamp-like conformation central to the mechanism of mitochondrial permeabilization. PMID:25458844

  7. Active rehabilitation in a pediatric extracorporeal membrane oxygenation patient.

    PubMed

    Zebuhr, Carleen; Sinha, Amit; Skillman, Heather; Buckvold, Shannon

    2014-05-01

    Decreased intensive care unit (ICU) mortality has led to an increase in ICU morbidity. ICU-induced immobilization plays a major role in this morbidity. Recently, ICU mobility has been shown to be safe and effective in adolescent and adult patients. We report the successful rehabilitation of an 8-year-old boy with severe acute respiratory distress syndrome on extracorporeal membrane oxygenation. A child who is critically ill may safely perform active rehabilitation while on venovenous extracorporeal membrane oxygenation. The gains achieved through active rehabilitation and optimal nutrition can facilitate recovery from severe acute respiratory distress syndrome in select pediatric patients on extracorporeal membrane oxygenation.

  8. The ExaVolt Antenna: A large-aperture, balloon-embedded antenna for ultra-high energy particle detection

    NASA Astrophysics Data System (ADS)

    Gorham, P. W.; Baginski, F. E.; Allison, P.; Liewer, K. M.; Miki, C.; Hill, B.; Varner, G. S.

    2011-12-01

    We describe the scientific motivation, experimental basis, design methodology, and simulated performance of the ExaVolt Antenna (EVA) mission, and planned ultra-high energy (UHE) particle observatory under development for NASA's suborbital super-pressure balloon program in Antarctica. EVA will improve over ANITA's integrated totals - the current state-of-the-art in UHE suborbital payloads - by 1-2 orders of magnitude in a single flight. The design is based on a novel application of toroidal reflector optics which utilizes a super-pressure balloon surface, along with a feed-array mounted on an inner membrane, to create an ultra-large radio antenna system with a synoptic view of the Antarctic ice sheet below it. Radio impulses arise via the Askaryan effect when UHE neutrinos interact within the ice, or via geosynchrotron emission when UHE cosmic rays interact in the atmosphere above the continent. EVA's instantaneous antenna aperture is estimated to be several hundred m 2 for detection of these events within a 150-600 MHz band. For standard cosmogenic UHE neutrino models, EVA should detect of order 30 events per flight in the EeV energy regime. For UHE cosmic rays, of order 15,000 geosynchrotron events would be detected in total, several hundred above 10 EeV, and of order 60 above the GZK cutoff energy.

  9. Characterization of the activation of small GTPases by their GEFs on membranes using artificial membrane tethering.

    PubMed

    Peurois, François; Veyron, Simon; Ferrandez, Yann; Ladid, Ilham; Benabdi, Sarah; Zeghouf, Mahel; Peyroche, Gérald; Cherfils, Jacqueline

    2017-02-14

    Attachment of active, GTP-bound small GTPases to membranes by post-translational lipid modifications is pivotal for their ability to process and propagate information in cells. However, generating and manipulating lipidated GTPases has remained difficult, which has limited our quantitative understanding of their activation by GEFs and their termination by GAPs. Here we replaced the lipid modification by a histidine tag in eleven full-length, human small GTPases belonging to the Arf, Rho and Rab families, which allowed to tether them to nickel-lipid containing membranes and characterize the kinetics of their activation by GEFs. Remarkably this strategy uncovered large effects of membranes on the efficiency and/or specificity in all systems studied. Notably, it recapitulated the release of autoinhibition of Arf1, Arf3, Arf4, Arf5 and Arf6 GTPases by membranes and revealed that all isoforms are efficiently activated by two GEFs with different regulatory regimes, ARNO and Brag2. It demonstrated that membranes stimulate the GEF activity of Trio towards RhoG by ≈30 fold and Rac1 by ≈10 fold, and uncovered a previously unknown broader specificity towards RhoA and Cdc42 that was undetectable in solution. Finally, it demonstrated that the exceptional affinity of the bacterial RabGEF DrrA for the phosphoinositide PI(4)P delimits the activation of Rab1 to the immediate vicinity of the membrane-bound GEF. Our study thus validates the histidine tag strategy as a potent and simple means to mimic small GTPases lipidation, which opens broad perspectives of applications to uncover regulations brought about by membranes.

  10. Research on sub-surface damage and its stress deformation in the process of large aperture and high diameter-to-thickness ratio TMT M3MP

    NASA Astrophysics Data System (ADS)

    Hu, Hai-xiang; Qi, Erhui; Cole, Glen; Hu, Hai-fei; Luo, Xiao; Zhang, Xue-jun

    2016-10-01

    Large flat mirrors play important roles in large aperture telescopes. However, they also introduce unpredictable problems. The surface errors created during manufacturing, testing, and supporting are all combined during measurement, thus making understanding difficult for diagnosis and treatment. Examining a high diameter-to-thickness ratio flat mirror, TMT M3MP, and its unexpected deformation during processing, we proposed a strain model of subsurface damage to explain the observed phenomenon. We designed a set of experiment, and checked the validity of our diagnosis. On that basis, we theoretical predicted the trend of this strain and its scale effect on Zerodur®, and checked the validity on another piece experimentally. This work guided the grinding-polishing process of M3MP, and will be used as reference for M3M processing as well.

  11. Development and Testing of a Power Trough System Using a Structurally-Efficient, High-Performance, Large-Aperture Concentrator with Thin Glass Reflector and Focal Point Rotation

    SciTech Connect

    May, E. K.; Forristall, R.

    2005-11-01

    Industrial Solar Technology has assembled a team of experts to develop a large-aperture parabolic trough for the electric power market that moves beyond cost and operating limitations of 1980's designs based on sagged glass reflectors. IST's structurally efficient space frame design will require nearly 50% less material per square meter than a Solel LS-2 concentrator and the new trough will rotate around the focal point. This feature eliminates flexhoses that increase pump power, installation and maintenance costs. IST aims to deliver a concentrator module costing less than $100 per square meter that can produce temperatures up to 400 C. The IST concentrator is ideally suited for application of front surface film reflectors and ensures that US corporations will manufacture major components, except for the high temperature receivers.

  12. Nervous factors influencing the membrane activity of intestinal smooth muscle

    PubMed Central

    Kuriyama, H.; Osa, T.; Toida, N.

    1967-01-01

    The effects of various chemical agents on the spontaneous membrane activities and those electrically elicited in the smooth muscles of small intestine were investigated. 1. The effects of various chemicals on the spontaneously active membrane might be summarized as follows. (a) Cholinergic agents; atropine slightly hyperpolarized the membrane and reduced the amplitude of slow potential changes even in aged preparations. Prostigmine depolarized the membrane, and enhanced the amplitude and prolonged the duration of the slow potential changes. Atropine prevented the actions of prostigmine on the membrane. (b) Ba2+ depolarized the membrane, and enhanced the amplitude and prolonged the duration of the slow potential changes. The spike frequency was initially increased, then reduced. Atropine and tetrodotoxin partially prevented the action of Ba2+ on the membrane activities. 2. Effects of chemical agents on the membrane activity elicited by electrical stimulation might be summarized as follows. (a) Short pulse stimulation (0·5-1 msec) generated the spike as a direct response of the muscle cell membrane, then it was followed by slow depolarization, delayed hyperpolarization, i.e. the `inhibitory potential', and post-inhibitory rebound successively. (b) The slow depolarization and the post-inhibitory rebound were reduced in amplitude by treatment with atropine, and enhanced by treatments with prostigmine and Ba2+. Tetrodotoxin blocked all activities except the spike. 3. When repetitive stimulation (20 c/s) was applied to the membrane, the membrane hyperpolarized; then, after 3-5 sec, it gradually depolarized even if the stimulation was continued, and triggered spikes. The hyperpolarization always preceded depolarization. The duration and the amplitude of the delayed depolarization was proportionally increased by the increased intensity and duration of stimulation. Atropine and tetrodotoxin blocked the generation of the post-inhibitory rebound. 4. Effects of repetitive

  13. Redistribution of Cholesterol in Model Lipid Membranes in Response to the Membrane-Active Peptide Alamethicin

    NASA Astrophysics Data System (ADS)

    Heller, William; Qian, Shuo

    2013-03-01

    The cellular membrane is a heterogeneous, dynamic mixture of molecules and macromolecules that self-assemble into a tightly-regulated functional unit that provides a semipermeable barrier between the cell and its environment. Among the many compositional differences between mammalian and bacterial cell membranes that impact its physical properties, one key difference is cholesterol content, which is more prevalent in mammals. Cholesterol is an amphiphile that associates with membranes and serves to maintain its fluidity and permeability. Membrane-active peptides, such as the alpha-helical peptide alamethicin, interact with membranes in a concentration- and composition-dependent manner to form transmembrane pores that are responsible for the lytic action of the peptide. Through the use of small-angle neutron scattering and deuterium labeling, it was possible to observe a redistribution of the lipid and cholesterol in unilamellar vesicles in response to the presence of alamethicin at a peptide-to-lipid ratio of 1/200. The results demonstrate that the membrane remodeling powers of alamethicin reach beyond the membrane thinning effect to altering the localization of specific components in the bilayer, complementing the accepted two-state mechanism of pore formation. Research was supported by U. S. DOE-OBER (CSMB; FWP ERKP291) and the U. S. DOE-BES Scientific User Facilities Division (ORNL's SNS and HFIR).

  14. Modulation of hyaluronan synthase activity in cellular membrane fractions.

    PubMed

    Vigetti, Davide; Genasetti, Anna; Karousou, Evgenia; Viola, Manuela; Clerici, Moira; Bartolini, Barbara; Moretto, Paola; De Luca, Giancarlo; Hascall, Vincent C; Passi, Alberto

    2009-10-30

    Hyaluronan (HA), the only non-sulfated glycosaminoglycan, is involved in morphogenesis, wound healing, inflammation, angiogenesis, and cancer. In mammals, HA is synthesized by three homologous HA synthases, HAS1, HAS2, and HAS3, that polymerize the HA chain using UDP-glucuronic acid and UDP-N-acetylglucosamine as precursors. Since the amount of HA is critical in several pathophysiological conditions, we developed a non-radioactive assay for measuring the activity of HA synthases (HASs) in eukaryotic cells and addressed the question of HAS activity during intracellular protein trafficking. We prepared three cellular fractions: plasma membrane, cytosol (containing membrane proteins mainly from the endoplasmic reticulum and Golgi), and nuclei. After incubation with UDP-sugar precursors, newly synthesized HA was quantified by polyacrylamide gel electrophoresis of fluorophore-labeled saccharides and high performance liquid chromatography. This new method measured HAS activity not only in the plasma membrane fraction but also in the cytosolic membranes. This new technique was used to evaluate the effects of 4-methylumbeliferone, phorbol 12-myristate 13-acetate, interleukin 1beta, platelet-derived growth factor BB, and tunicamycin on HAS activities. We found that HAS activity can be modulated by post-translational modification, such as phosphorylation and N-glycosylation. Interestingly, we detected a significant increase in HAS activity in the cytosolic membrane fraction after tunicamycin treatment. Since this compound is known to induce HA cable structures, this result links HAS activity alteration with the capability of the cell to promote HA cable formation.

  15. Bilayer Membrane Modulation of Membrane Type 1 Matrix Metalloproteinase (MT1-MMP) Structure and Proteolytic Activity

    PubMed Central

    Cerofolini, Linda; Amar, Sabrina; Lauer, Janelle L.; Martelli, Tommaso; Fragai, Marco; Luchinat, Claudio; Fields, Gregg B.

    2016-01-01

    Cell surface proteolysis is an integral yet poorly understood physiological process. The present study has examined how the pericellular collagenase membrane-type 1 matrix metalloproteinase (MT1-MMP) and membrane-mimicking environments interplay in substrate binding and processing. NMR derived structural models indicate that MT1-MMP transiently associates with bicelles and cells through distinct residues in blades III and IV of its hemopexin-like domain, while binding of collagen-like triple-helices occurs within blades I and II of this domain. Examination of simultaneous membrane interaction and triple-helix binding revealed a possible regulation of proteolysis due to steric effects of the membrane. At bicelle concentrations of 1%, enzymatic activity towards triple-helices was increased 1.5-fold. A single mutation in the putative membrane interaction region of MT1-MMP (Ser466Pro) resulted in lower enzyme activation by bicelles. An initial structural framework has thus been developed to define the role(s) of cell membranes in modulating proteolysis. PMID:27405411

  16. The influence of membrane lipid structure on plasma membrane Ca2+ -ATPase activity.

    PubMed

    Tang, Daxin; Dean, William L; Borchman, Douglas; Paterson, Christopher A

    2006-03-01

    Lipid composition and Ca(2+)-ATPase activity both change with age and disease in many tissues. We explored relationships between lipid composition/structure and plasma membrane Ca(2+)-ATPase (PMCA) activity. PMCA was purified from human erythrocytes and was reconstituted into liposomes prepared from human ocular lens membrane lipids and synthetic lipids. Lens lipids were used in this study as a model for naturally ordered lipids, but the influence of lens lipids on PMCA function is especially relevant to the lens since calcium homeostasis is vital to lens clarity. Compared to fiber cell lipids, epithelial lipids exhibited an ordered to disordered phase transition temperature that was 12 degrees C lower. Reconstitution of PMCA into lipids was essential for maximal activity. PMCA activity was two to three times higher when the surrounding phosphatidylcholine molecules contained acyl chains that were ordered (stiff) compared to disordered (fluid) acyl chains. In a completely ordered lipid hydrocarbon chain environment, PMCA associates more strongly with the acidic lipid phosphatidylserine in comparison to phosphatidylcholine. PMCA associates much more strongly with phosphatidylcholine containing disordered hydrocarbon chains than ordered hydrocarbon chains. PMCA activity is influenced by membrane lipid composition and structure. The naturally high degree of lipid order in plasma membranes such as those found in the human lens may serve to support PMCA activity. The absence of PMCA activity in the cortical region of human lenses is apparently not due to a different lipid environment. Changes in lipid composition such as those observed with age or disease could potentially influence PMCA function.

  17. Ovalbumin with Glycated Carboxyl Groups Shows Membrane-Damaging Activity

    PubMed Central

    Tang, Ching-Chia; Shi, Yi-Jun; Chen, Ying-Jung; Chang, Long-Sen

    2017-01-01

    The aim of the present study was to investigate whether glycated ovalbumin (OVA) showed novel activity at the lipid-water interface. Mannosylated OVA (Man-OVA) was prepared by modification of the carboxyl groups with p-aminophenyl α-dextro (d)-mannopyranoside. An increase in the number of modified carboxyl groups increased the membrane-damaging activity of Man-OVA on cell membrane-mimicking vesicles, whereas OVA did not induce membrane permeability in the tested phospholipid vesicles. The glycation of carboxyl groups caused a notable change in the gross conformation of OVA. Moreover, owing to their spatial positions, the Trp residues in Man-OVA were more exposed, unlike those in OVA. Fluorescence quenching studies suggested that the Trp residues in Man-OVA were located on the interface binds with the lipid vesicles, and their microenvironment was abundant in positively charged residues. Although OVA and Man-OVA showed a similar binding affinity for lipid vesicles, the lipid-interacting feature of Man-OVA was distinct from that of OVA. Chemical modification studies revealed that Lys and Arg residues, but not Trp residues, played a crucial role in the membrane-damaging activity of Man-OVA. Taken together, our data suggest that glycation of carboxyl groups causes changes in the structural properties and membrane-interacting features of OVA, generating OVA with membrane-perturbing activities at the lipid-water interface. PMID:28264493

  18. Research on the Problem of High-Precision Deployment for Large-Aperture Space-Based Science Instruments

    NASA Technical Reports Server (NTRS)

    Lake, Mark S.; Peterson, Lee D.; Hachkowski, M. Roman; Hinkle, Jason D.; Hardaway, Lisa R.

    1998-01-01

    The present paper summarizes results from an ongoing research program conducted jointly by the University of Colorado and NASA Langley Research Center since 1994. This program has resulted in general guidelines for the design of high-precision deployment mechanisms, and tests of prototype deployable structures incorporating these mechanisms have shown microdynamically stable behavior (i.e., dimensional stability to parts per million). These advancements have resulted from the identification of numerous heretofore unknown microdynamic and micromechanical response phenomena, and the development of new test techniques and instrumentation systems to interrogate these phenomena. In addition, recent tests have begun to interrogate nanomechanical response of materials and joints and have been used to develop an understanding of nonlinear nanodynamic behavior in microdynamically stable structures. The ultimate goal of these efforts is to enable nano-precision active control of micro-precision deployable structures (i.e., active control to a resolution of parts per billion).

  19. Membrane Thinning and Thickening Induced by Membrane-Active Amphipathic Peptides

    PubMed Central

    Grage, Stephan L.; Afonin, Sergii; Kara, Sezgin; Buth, Gernot; Ulrich, Anne S.

    2016-01-01

    Membrane thinning has been discussed as a fundamental mechanism by which antimicrobial peptides can perturb cellular membranes. To understand which factors play a role in this process, we compared several amphipathic peptides with different structures, sizes and functions in their influence on the lipid bilayer thickness. PGLa and magainin 2 from X. laevis were studied as typical representatives of antimicrobial cationic amphipathic α-helices. A 1:1 mixture of these peptides, which is known to possess synergistically enhanced activity, allowed us to evaluate whether and how this synergistic interaction correlates with changes in membrane thickness. Other systems investigated here include the α-helical stress-response peptide TisB from E. coli (which forms membrane-spanning dimers), as well as gramicidin S from A. migulanus (a natural antibiotic), and BP100 (designer-made antimicrobial and cell penetrating peptide). The latter two are very short, with a circular β-pleated and a compact α-helical structure, respectively. Solid-state 2H-NMR and grazing incidence small angle X-ray scattering (GISAXS) on oriented phospholipid bilayers were used as complementary techniques to access the hydrophobic thickness as well as the bilayer-bilayer repeat distance including the water layer in between. This way, we found that magainin 2, gramicidin S, and BP100 induced membrane thinning, as expected for amphiphilic peptides residing in the polar/apolar interface of the bilayer. PGLa, on the other hand, decreased the hydrophobic thickness only at very high peptide:lipid ratios, and did not change the bilayer-bilayer repeat distance. TisB even caused an increase in the hydrophobic thickness and repeat distance. When reconstituted as a mixture, PGLa and magainin 2 showed a moderate thinning effect which was less than that of magainin 2 alone, hence their synergistically enhanced activity does not seem to correlate with a modulation of membrane thickness. Overall, the absence of a

  20. Membrane solubilization by a hydrophobic polyelectrolyte: surface activity and membrane binding.

    PubMed Central

    Thomas, J L; Barton, S W; Tirrell, D A

    1994-01-01

    We have previously observed that the hydrophobic polyelectrolyte poly(2-ethylacrylic acid) solubilizes lipid membranes in a pH-dependent manner, and we have exploited this phenomenon to prepare lipid vesicles that release their contents in response to pH, light, or glucose (Thomas, J. L., and D. A. Tirrell. Acc. Chem. Res. 25:336-342, 1992). The physical basis for the interaction between poly(2-ethylacrylic acid) and lipid membranes has been explored using surface tensiometry and fluorimetry. Varying the polymer concentration results in changes in surface activity and membrane binding that correlate with shifts in the critical pH for membrane solubilization. Furthermore, the binding affinity is reduced as the amount of bound polymer increases. These results are consistent with a hydrophobically driven micellization process, similar to those observed with apolipoproteins, melittin, and other amphiphilic alpha-helix-based polypeptides. The absence of specific secondary structure in the synthetic polymer suggests that amphiphilicity, rather than structure, is the most important factor in membrane micellization by macromolecules. PMID:7811920

  1. Montana Large Aperture Seismic Array

    DTIC Science & Technology

    1977-10-28

    described by Matk ins (1976) provide an efficient means of data playout for event anal- ysis and for event data retention at the LDC. For the one—year...Controls (C2) 0 Controls (C3) 0 Operation Decode 2 Interrupts 0 Gen . Purpose Register Stack 2 Console (El) 0 Console (E2) 2 High Speed Multiplexer I...Since our signal gen - erator ’s (203A) maximum output of 3OVp-p will not check the LP seismometers at the high end of their amplitude range, a driver

  2. Improved Large Aperture Collector Manufacturing

    SciTech Connect

    O'Rourke, Deven; Farr, Adrian

    2015-12-01

    The parabolic trough is the most established CSP technology and carries a long history of design experimentation dating back to the 1970’s. This has led to relatively standardized collector architectures, a maturing global supply chain, and a fairly uniform cost reduction strategy. Abengoa has deployed more than 1,500MWe of CSP troughs across several countries and has built and tested full-scale prototypes of many R&D concepts. The latest trough R&D efforts involved efforts to internalize non-CSP industry experience including a preliminary DFMA principles review done with Boothroyd Dewhurst, a construction literature review by the Arizona State University School of Construction Management, and two more focused manufacturing engineering subcontracts done by Ricardo Inc. and the nonprofit Edison Welding Institute. The first two studies highlighted strong opportunities in lowering part count, standardizing components and fasteners, developing modular designs to support prefabrication and automation, and devising simple, error-proof manual assembly methods. These principles have delivered major new cost savings in otherwise “mature” products in analogous industries like automotive, truck trailer manufacture, metal building fabrication, and shipbuilding. For this reason, they were core in the design development of the SpaceTube® collector, and arguably key to its early successes. The latter two studies were applied specifically to the first-generation SpaceTube® design and were important in setting the direction of the present SolarMat project. These studies developed a methodology to analyze the costs of manufacture and assembly, and identify new tooling concepts for more efficient manufacture. Among the main opportunities identified in these studies were the automated mirror arm manufacturing concept and the need for a less infrastructure-intensive assembly line, both of which now form central pillars of the SolarMat project strategy. These new designs will be supported by new technology in the area of quality control inspection, in which state of the art photogrammetry and laser CMM inspection methods will be used to qualify parts and assemblies, and in which the recently-developed Absorber Reflection Method will enable in-line quality control inspection of modules produced by the new high-rate production line.

  3. Large Aperture Electrostatic Dust Detector

    SciTech Connect

    C.H. Skinner, R. Hensley, and A.L Roquemore

    2007-10-09

    Diagnosis and management of dust inventories generated in next-step magnetic fusion devices is necessary for their safe operation. A novel electrostatic dust detector, based on a fine grid of interlocking circuit traces biased to 30 or 50 ν has been developed for the detection of dust particles on remote surfaces in air and vacuum environments. Impinging dust particles create a temporary short circuit and the resulting current pulse is recorded by counting electronics. Up to 90% of the particles are ejected from the grid or vaporized suggesting the device may be useful for controlling dust inventories. We report measurements of the sensitivity of a large area (5x5 cm) detector to microgram quantities of dust particles and review its applications to contemporary tokamaks and ITER.

  4. Large aperture at low cost three-dimensional time-of-flight range sensor using scanning micromirrors and synchronous detector switching.

    PubMed

    Bogatscher, Siegwart; Streck, Andreas; Fox, Maik; Meinzer, Sebastian; Heussner, Nico; Stork, Wilhelm

    2014-03-10

    In this article the problem of achieving fast scanning of a time-of-flight range sensor with a large optical receiver aperture at low system cost is targeted. The presented approach to solve this problem consists of a micromirror-based transmitter unit and a receiver unit consisting of a large aperture lens system with a small field of view and a detector array. A concept, which is called synchronous detector switching, is applied to the detector array. Thereby electronic steering of the small receiver field of view is possible. The overall approach is compared to alternative approaches, and the underlying concept of synchronous detector switching is demonstrated experimentally in an implementation of a three-dimensional time-of-flight range sensor. It is theoretically shown that the presented concept is potentially cheaper than the alternative approaches for applications with a field of view of less than 60×60°. After a discussion of the strengths and limitations of the approach, its effect on broader scientific issues is outlined.

  5. Simulation of P systems with active membranes on CUDA.

    PubMed

    Cecilia, José M; García, José M; Guerrero, Ginés D; Martínez-del-Amor, Miguel A; Pérez-Hurtado, Ignacio; Pérez-Jiménez, Mario J

    2010-05-01

    P systems or Membrane Systems provide a high-level computational modelling framework that combines the structure and dynamic aspects of biological systems in a relevant and understandable way. They are inherently parallel and non-deterministic computing devices. In this article, we discuss the motivation, design principles and key of the implementation of a simulator for the class of recognizer P systems with active membranes running on a (GPU). We compare our parallel simulator for GPUs to the simulator developed for a single central processing unit (CPU), showing that GPUs are better suited than CPUs to simulate P systems due to their highly parallel nature.

  6. Steady-state compartmentalization of lipid membranes by active proteins.

    PubMed Central

    Sabra, M C; Mouritsen, O G

    1998-01-01

    Using a simple microscopic model of lipid-protein interactions, based on the hydrophobic matching principle, we study some generic aspects of lipid-membrane compartmentalization controlled by a dispersion of active integral membrane proteins. The activity of the proteins is simulated by conformational excitations governed by an external drive, and the deexcitation is controlled by interaction of the protein with its lipid surroundings. In response to the flux of energy into the proteins from the environment and the subsequent dissipation of energy into the lipid bilayer, the lipid-protein assembly reorganizes into a steady-state structure with a typical length scale determined by the strength of the external drive. In the specific case of a mixed dimyristoylphosphatidylcholine-distearoylphosphatidylcholine bilayer in the gel-fluid coexistence region, it is shown explicitly by computer simulation that the activity of an integral membrane protein can lead to a compartmentalization of the lipid-bilayer membrane. The compartmentalization is related to the dynamical process of phase separation and lipid domain formation. PMID:9533687

  7. Alkaline ribonuclease and phosphodiesterase activity in rat liver plasma membranes

    PubMed Central

    Prospero, Terence D.; Burge, Malcolm L. E.; Norris, Kenneth A.; Hinton, Richard H.; Reid, Eric

    1973-01-01

    The ribonuclease and phosphodiesterase activities of rat liver plasma membranes, purified from the crude nuclear fraction by centrifugation in an A-XII zonal rotor and flotation, were examined and compared. The plasma membrane is responsible for between 65 and 90% of the phosphodiesterase activity of the cell and between 25 and 30% of the particulate ribonuclease activity measured at pH8.7 in the presence of 7.5mm-MgCl2. Both enzymes were most active between pH8.5 and 8.9. Close to the pH optimum, both enzymes were more active in Tris buffer than in Bicine or glycine buffer. Both plasma-membrane phosphodiesterase and ribonuclease were strongly activated by Mg2+, there being at least a 12-fold difference between the activity in the presence of Mg2+ and of EDTA. There is, however, a difference in the response of the enzymes to Mg2+ and EDTA in that the phosphodiesterase is fully activated by 1.0mm-MgCl2 and fully inhibited by 1.0mm-EDTA, whereas the ribonuclease requires 7.5mm-MgCl2 for full activation and 5mm-EDTA for full inhibition. Density-gradient centrifugation has indicated that on solubilization in Triton X-100 most of the ribonuclease activity is released into a small fragment of the same size as that containing the phosphodiesterase activity. The relationship between the two activities is discussed in view of these results. PMID:4353377

  8. Ion channel activity in lobster skeletal muscle membrane.

    PubMed

    Worden, M K; Rahamimoff, R; Kravitz, E A

    1993-09-01

    Ion channel activity in the sarcolemmal membrane of muscle fibers is critical for regulating the excitability, and therefore the contractility, of muscle. To begin the characterization of the biophysical properties of the sarcolemmal membrane of lobster exoskeletal muscle fibers, recordings were made from excised patches of membrane from enzymatically induced muscle fiber blebs. Blebs formed as evaginations of the muscle sarcolemmal membrane and were sufficiently free of extracellular debris to allow the formation of gigaohm seals. Under simple experimental conditions using bi-ionic symmetrical recording solutions and maintained holding potentials, a variety of single channel types with conductances in the range 32-380 pS were detected. Two of these ion channel species are described in detail, both are cation channels selective for potassium. They can be distinguished from each other on the basis of their single-channel conductance and gating properties. The results suggest that current flows through a large number of ion channels that open spontaneously in bleb membranes in the absence of exogenous metabolites or hormones.

  9. Source locations of teleseismic P, SV, and SH waves observed in microseisms recorded by a large aperture seismic array in China

    NASA Astrophysics Data System (ADS)

    Liu, Qiaoxia; Koper, Keith D.; Burlacu, Relu; Ni, Sidao; Wang, Fuyun; Zou, Changqiao; Wei, Yunhao; Gal, Martin; Reading, Anya M.

    2016-09-01

    Transversely polarized seismic waves are routinely observed in ambient seismic energy across a wide range of periods, however their origin is poorly understood because the corresponding source regions are either undefined or weakly constrained, and nearly all models of microseism generation incorporate a vertically oriented single force as the excitation mechanism. To better understand the origin of transversely polarized energy in the ambient seismic wavefield we make the first systematic attempt to locate the source regions of teleseismic SH waves observed in microseismic (2.5-20 s) noise. We focus on body waves instead of surface waves because the source regions can be constrained in both azimuth and distance using conventional array techniques. To locate microseismic sources of SH waves (as well as SV and P waves) we continuously backproject the vertical, radial, and transverse components of the ambient seismic wavefield recorded by a large-aperture array deployed in China during 2013-2014. As expected, persistent P wave sources are observed in the North Atlantic, North Pacific, and Indian Oceans, mainly at periods of 2.5-10 s, in regions with the strong ocean wave interactions needed to produce secondary microseisms. SV waves are commonly observed to originate from locations indistinguishable from the P wave sources, but with smaller signal-to-noise ratios. We also observe SH waves with about half or less the signal-to-noise ratio of SV waves. SH source regions are definitively located in deep water portions of the Pacific, away from the sloping continental shelves that are thought to be important for the generation of microseismic Love waves, but nearby regions that routinely generate teleseismic P waves. The excitation mechanism for the observed SH waves may therefore be related to the interaction of P waves with small-wavelength bathymetric features, such as seamounts and basins, through some sort of scattering process.

  10. OpTIIX: An ISS-Based Testbed Paving the Roadmap Toward a Next Generation Large Aperture UV/Optical Space Telescope

    NASA Technical Reports Server (NTRS)

    Carpenter, Kenneth G.; Etemad, Shar; Seery, Bernard D.; Thronson, Harley; Burdick, Gary M.; Coulter, Dan; Goullioud, Renaud; Green, Joseph J.; Liu, Fengchuan; Ess, Kim; Postman, Marc; Sparks, Williams

    2012-01-01

    The next generation large aperture UV/Optical space telescope will need a diameter substantially larger than even that of JWST in order to address some of the most compelling unanswered scientific quests. These quests include understanding the earliest phases of the Universe and detecting life on exo-planets by studying spectra of their atmospheres. Such 8-16 meter telescopes face severe challenges in terms of cost and complexity and are unlikely to be affordable unless a new paradigm is adopted for their design and construction. The conventional approach is to use monolithic or preassembled segmented mirrors requiring complicated and risky deployments and relying on future heavy-lift vehicles, large fairings and complex geometry. The new paradigm is to launch component modules on relatively small vehicles and then perform in-orbit robotic assembly of those modules. The Optical Testbed and Integration on ISS eXperiment (OpTIIX) is designed to demonstrate, at low cost by leveraging the infrastructure provided by ISS, telescope assembly technologies and end-to-end optical system technologies. The use of ISS as a testbed permits the concentration of resources on reducing the technical risks associated with robotically integrating the components. These include laser metrology and wavefront sensing and control (WFS&C) systems, an imaging instrument, lightweight, low-cost deformable primary mirror segments and the secondary mirror. These elements are then aligned to a diffraction-limited optical system in space. The capability to assemble the optical system and remove and replace components via the existing ISS robotic systems like the Special Purpose Dexterous Manipulator (SPDM), or by the ISS flight crew, allows for future experimentation, as well as repair.

  11. Continuous series of catchment-averaged sensible heat flux from a Large Aperture Scintillometer: efficient estimation of stability conditions and importance of fluxes under stable conditions

    NASA Astrophysics Data System (ADS)

    De Lathauwer, E.; Samain, B.; Defloor, W.; Pauwels, V. R.

    2011-12-01

    A Large Aperture Scintillometer (LAS) observes the intensity of the atmospheric turbulence across large distances, which is related to the path averaged sensible heat flux, H. This sensible heat flux can then easily be inverted into evapotranspiration rates using the surface energy balance. In this prestentation, two problems in the derivation of continuous series of H from LAS-data are investigated and the importance of nighttime H -fluxes is assessed. Firstly, as a LAS is unable to determine the sign of H, the transition from unstable to stable conditions is evaluated in order to make continuous H-series. Therefore, different algorithms to judge the atmospheric stability for a LAS installed over a distance of 9.5km have been tested. The algorithm based on the diurnal cycle of the refractive index structure parameter, CN2, has been found to be very suitable and operationally the most appropriate. A second issue is the humidity correction for LAS-data, which is performed by using the Bowen ratio (β). As β is taken from ground-based measurements with data gaps, the number of resulting H -values is reduced. Not including this humidity correction results in a marginal error in H, but increases the completeness of the resulting H -series. Applying these conclusions to the two-year time series of the LAS, results in an almost continuous H -time series. As the majority of the time steps has been found to be under stable conditions, there is a clear impact of Hstable on H24h, the 24h average of H. For stable conditions, Hstable -values are mostly negative, and hence lower than the H = 0 assumption as is mostly adopted. For months where stable conditions prevail (Winter), H24h is overestimated using this assumption, and calculation of Hstable is recommended.

  12. Continuous series of catchment-averaged sensible heat flux from a Large Aperture Scintillometer: efficient estimation of stability conditions and importance of fluxes under stable conditions.

    NASA Astrophysics Data System (ADS)

    Samain, B.; Defloor, W.; Pauwels, V. R. N.

    2012-04-01

    A Large Aperture Scintillometer (LAS) observes the intensity of the atmospheric turbulence across large distances, which is related to the path averaged sensible heat flux, H. Two problems in the derivation of continuous series of H from LAS-data are investigated and the importance of nighttime H -fluxes is assessed. Firstly, as a LAS is unable to determine the sign of H, the transition from unstable to stable conditions is evaluated in order to make continuous H -series. Therefore, different algorithms to judge the atmospheric stability for a LAS installed over a distance of 9.5 km have been tested. The diurnal cycle of the refractive index structure parameter, CN2, results in the best suitable, operational algorithm. A second issue is the humidity correction for LAS-data, which is performed by using the Bowen ratio (β). As β is taken from ground-based measurements with data gaps, the number of resulting H -values is reduced. Not including this humidity correction results in a marginal error in H, but increases the completeness of the resulting H -series. Applying these conclusions to the two-year time series of the LAS, results in an almost continuous H -time series. As the majority of the time steps has been found to be under stable conditions, there is a clear impact of Hstable on H24h ,the 24h average of H. For stable conditions, Hstable -values are mostly negative, and hence lower than the H = 0 W/m2 assumption as is mostly adopted. For months where stable conditions prevail (Winter), H24h is overestimated using this assumption, and calculation of Hstable is recommended.

  13. Endocrine Activity of Extraembryonic Membranes Extends beyond Placental Amniotes

    PubMed Central

    Albergotti, Lori C.; Hamlin, Heather J.; McCoy, Michael W.; Guillette,, Louis J.

    2009-01-01

    Background During development, all amniotes (mammals, reptiles, and birds) form extraembryonic membranes, which regulate gas and water exchange, remove metabolic wastes, provide shock absorption, and transfer maternally derived nutrients. In viviparous (live-bearing) amniotes, both extraembryonic membranes and maternal uterine tissues contribute to the placenta, an endocrine organ that synthesizes, transports, and metabolizes hormones essential for development. Historically, endocrine properties of the placenta have been viewed as an innovation of placental amniotes. However, an endocrine role of extraembryonic membranes has not been investigated in oviparous (egg-laying) amniotes despite similarities in their basic structure, function, and shared evolutionary ancestry. In this study, we ask whether the oviparous chorioallantoic membrane (CAM) of chicken (Gallus gallus) has the capability to synthesize and receive signaling of progesterone, a major placental steroid hormone. Methodology/Principal Findings We quantified mRNA expression of key steroidogenic enzymes involved in progesterone synthesis and found that 3β-hydroxysteroid dehydrogenase, which converts pregnenolone to progesterone exhibited a 464 fold increase in the CAM from day 8 to day 18 of embryonic development (F5, 68 = 89.282, p<0.0001). To further investigate progesterone synthesis, we performed explant culture and found that the CAM synthesizes progesterone in vitro in the presence of a steroid precursor. Finally, we quantified mRNA expression and performed protein immunolocalization of the progesterone receptor in the CAM. Conclusions/Significance Collectively, our data indicate that the chick CAM is steroidogenic and has the capability to both synthesize progesterone and receive progesterone signaling. These findings represent a paradigm shift in evolutionary reproductive biology by suggesting that endocrine activity of extraembryonic membranes is not a novel characteristic of placental

  14. Solubilized placental membrane protein inhibits insulin receptor tyrosine kinase activity

    SciTech Connect

    Strout, H.V. Jr.; Slater, E.E.

    1987-05-01

    Regulation of insulin receptor (IR) tyrosine kinase (TK) activity may be important in modulating insulin action. Utilizing an assay which measures IR phosphorylation of angiotensin II (AII), the authors investigated whether fractions of TX-100 solubilized human placental membranes inhibited IR dependent AII phosphorylation. Autophosphorylated IR was incubated with membrane fractions before the addition of AII, and kinase inhibition measured by the loss of TSP incorporated in AII. An inhibitory activity was detected which was dose, time, and temperature dependent. The inhibitor was purified 200-fold by sequential chromatography on wheat germ agglutinin, DEAE, and hydroxyapatite. This inhibitory activity was found to correlate with an 80 KD protein which was electroeluted from preparative slab gels and rabbit antiserum raised. Incubation of membrane fractions with antiserum before the IRTK assay immunoprecipitated the inhibitor. Protein immunoblots of crude or purified fractions revealed only the 80 KD protein. Since IR autophosphorylation is crucial to IRTK activity, the authors investigated the state of IR autophosphorylation after treatment with inhibitor; no change was detected by phosphoamino acid analysis.

  15. Mechanism for Active Membrane Fusion Triggering by Morbillivirus Attachment Protein

    PubMed Central

    Ader, Nadine; Brindley, Melinda; Avila, Mislay; Örvell, Claes; Horvat, Branka; Hiltensperger, Georg; Schneider-Schaulies, Jürgen; Vandevelde, Marc; Zurbriggen, Andreas; Plemper, Richard K.

    2013-01-01

    The paramyxovirus entry machinery consists of two glycoproteins that tightly cooperate to achieve membrane fusion for cell entry: the tetrameric attachment protein (HN, H, or G, depending on the paramyxovirus genus) and the trimeric fusion protein (F). Here, we explore whether receptor-induced conformational changes within morbillivirus H proteins promote membrane fusion by a mechanism requiring the active destabilization of prefusion F or by the dissociation of prefusion F from intracellularly preformed glycoprotein complexes. To properly probe F conformations, we identified anti-F monoclonal antibodies (MAbs) that recognize conformation-dependent epitopes. Through heat treatment as a surrogate for H-mediated F triggering, we demonstrate with these MAbs that the morbillivirus F trimer contains a sufficiently high inherent activation energy barrier to maintain the metastable prefusion state even in the absence of H. This notion was further validated by exploring the conformational states of destabilized F mutants and stabilized soluble F variants combined with the use of a membrane fusion inhibitor (3g). Taken together, our findings reveal that the morbillivirus H protein must lower the activation energy barrier of metastable prefusion F for fusion triggering. PMID:23077316

  16. Solubilization of active (H+ + K+)-ATPase from gastric membrane.

    PubMed

    Soumarmon, A; Grelac, F; Lewin, M J

    1983-08-10

    (H+ + K+)-ATPase-enriched membranes were prepared from hog gastric mucosa by sucrose gradient centrifugation. These membranes contained Mg2+-ATPase and p-nitrophenylphosphatase activities (68 +/- 9 mumol Pi and 2.9 +/- 0.6 mumol p-nitrophenol/mg protein per h) which were insensitive to ouabain and markedly stimulated by 20 mM KCl (respectively, 2.2- and 14.8-fold). Furthermore, the membranes autophosphorylated in the absence of K+ (up to 0.69 +/- 0.09 nmol Pi incorporated/mg protein) and dephosphorylated by 85% in the presence of this ion. Membrane proteins were extracted by 1-2% (w/v) n-octylglucoside into a soluble form, i.e., which did not sediment in a 100 000 X g X 1 h centrifugation. This soluble form precipitated upon further dilution in detergent-free buffer. Extracted ATPase represented 32% (soluble form) and 68% (precipitated) of native enzyme and it displayed the same characteristic properties in terms of K+-stimulated ATPase and p-nitrophenylphosphatase activities and K+-sensitive phosphorylation: Mg2+-ATPase (mumol Pi/mg protein per h) 32 +/- 9 (basal) and 86 +/- 20 (K+-stimulated); Mg2+-p-nitrophenylphosphatase (mumol p-nitrophenol/mg protein per h) 2.6 +/- 0.5 (basal) and 22.2 +/- 3.2 (K+-stimulated); Mg2+-phosphorylation (nmol Pi/mg protein) 0.214 +/- 0.041 (basal) and 0.057 +/- 0.004 (in the presence of K+). In glycerol gradient centrifugation, extracted enzyme equilibrated as a single peak corresponding to an apparent 390 000 molecular weight. These findings provide the first evidence for the solubilization of (H+ + K+)-ATPase in a still active structure.

  17. Calcium Modulation of Plant Plasma Membrane-Bound Atpase Activities

    NASA Technical Reports Server (NTRS)

    Caldwell, C.

    1983-01-01

    The kinetic properties of barley enzyme are discussed and compared with those of other plants. Possibilities for calcium transport in the plasma membrane by proton pump and ATPase-dependent calcium pumps are explored. Topics covered include the ph phase of the enzyme; high affinity of barley for calcium; temperature dependence, activation enthalpy, and the types of ATPase catalytic sites. Attention is given to lipids which are both screened and bound by calcium. Studies show that barley has a calmodulin activated ATPase that is found in the presence of magnesium and calcium.

  18. Rapid test for distinguishing membrane-active antibacterial agents.

    PubMed

    Prakash Singh, Maya

    2006-10-01

    In the search for antibacterial agents with a novel mode-of-action (MOA) many targeted cellular and cell-free assays are developed and used to screen chemical and natural product libraries. Frequently, hits identified by the primary screens include compounds with nonspecific activities that can affect the integrity and function of bacterial membrane. For a rapid dereplication of membrane-active compounds, a simple method was established using a commercially available Live/Dead(R) Bacterial Viability Kit. This method utilized two fluorescent nucleic acid stains, SYTO9 (stains all cells green) and propidium iodide (stains cells with damaged membrane red) for the drug-treated bacterial cells. The cells were then either examined visually by fluorescence microscopy or their fluorescence emissions were recorded using a multi-label plate reader set to measure emissions at two different wavelengths. The ratio of green versus red was compared to a standard curve indicating the percentage of live versus dead bacteria. Nine known antibiotics and 14 lead compounds from various antibacterial screens were tested with results consistent with their MOA.

  19. Antiviral activity of squalamine: Role of electrostatic membrane binding

    NASA Astrophysics Data System (ADS)

    Beckerman, Bernard; Qu, Wei; Mishra, Abhijit; Zasloff, Michael; Wong, Gerard; Luijten, Erik

    2012-02-01

    Recent workootnotetextM. Zasloff et al., Proc. Nat. Acad. Sci. (USA) 108, 15978 (2011). has demonstrated that squalamine, a molecule found in the liver of sharks, exhibits broad-spectrum antiviral properties. It has been proposed that this activity results from the charge-density matching of squalamine and phospholipid membranes, causing squalamine to bind to membranes and displace proteins such as Rac1 that are crucial for the viral replication cycle. Here we investigate this hypothesis by numerical simulation of a coarse-grained model for the competition between Rac1 and squalamine in binding affinity to a flat lipid bilayer. We perform free-energy calculations to test the ability of squalamine to condense stacked bilayer systems and thereby displace bulkier Rac1 molecules. We directly compare our findings to small-angle x-ray scattering results for the same setup.

  20. Flagellar tip activation stimulated by membrane adhesions in Chlamydomonas gametes

    PubMed Central

    1980-01-01

    Membrane adhesions between the flagella of mating-type "plus" and "minus" gametes of Chlamydomonas reinhardi are shown to stimulate a rapid change in the ultrastructure of the flagellar tips, designated as flagellar tip activation (FTA). A dense substance, termed fibrous tip material (FTM), accumulates between the flagellar membrane and the nine single A microtubules of the tip. The A microtubules then elongate, growing into the distal region of the tip, increasing tip length by 30%. This study describes FTA kinetics during normal and mutant matings, presents experiments designed to probe its role in the mating reaction, and offers the following conclusions: (a) FTA is elicited by agents that cross-link flagellar membrane components (including natural sexual agglutinins, antiflagellar antisera, and concanavalin A) but not by flagellar adherence to polylysine-coated films. (b) FTA is reversed by flagellar disadhesion. (c) Gametes can undergo repeated cycles of FTA during successive rounds of adhesion/disadhesion. (d) FTA, flagellar tipping, and sexual signaling are simultaneously blocked by colchicine and by vinblastine, suggesting that tubulinlike molecules, perhaps exposed at the membrane surface, are involved in all three responses. (e) FTA is not blocked by short exposure to chymotrypsin, by cytochalasins B and D, nor by concanavalin A, even though all block cell fusion; the response is therefore autonomous and experimentally dissociable from later stages in the mating reaction. (f) Under no experimental conditions is mating-structure activation observed to occur unless FTA also occurs. This study concludes that FTA is a necessary event in the sexual signaling sequence, and presents a testable working model for its mechanism. PMID:7358792

  1. Modulation of Erythrocyte Plasma Membrane Redox System Activity by Curcumin

    PubMed Central

    Singh, Prabhakar; Kesharwani, Rajesh Kumar; Misra, Krishna; Rizvi, Syed Ibrahim

    2016-01-01

    Plasma membrane redox system (PMRS) is an electron transport chain system ubiquitously present throughout all cell types. It transfers electron from intracellular substrates to extracellular acceptors for regulation of redox status. Curcumin, isolated from Curcuma longa, has modulatory effects on cellular physiology due to its membrane interaction ability and antioxidant potential. The present study investigates the effect of curcumin on PMRS activity of erythrocytes isolated from Wistar rats in vitro and in vivo and validated through an in silico docking simulation study using Molegro Virtual Docker (MVD). Effects of curcumin were also evaluated on level of glutathione (GSH) and the oxidant potential of plasma measured in terms of plasma ferric equivalent oxidative potentials (PFEOP). Results show that curcumin significantly (p < 0.01) downregulated the PMRS activity in a dose-dependent manner. Molecular docking results suggest that curcumin interacts with amino acids at the active site cavity of cytochrome b5 reductase, a key constituent of PMRS. Curcumin also increased the GSH level in erythrocytes and plasma while simultaneously decreasing the oxidant potential (PFEOP) of plasma. Altered PMRS activity and redox status are associated with the pathophysiology of several health complications including aging and diabetes; hence, the above finding may explain part of the role of curcumin in health beneficial effects. PMID:26904287

  2. Membrane lipids regulate ganglioside GM2 catabolism and GM2 activator protein activity[S

    PubMed Central

    Anheuser, Susi; Breiden, Bernadette; Schwarzmann, Günter; Sandhoff, Konrad

    2015-01-01

    Ganglioside GM2 is the major lysosomal storage compound of Tay-Sachs disease. It also accumulates in Niemann-Pick disease types A and B with primary storage of SM and with cholesterol in type C. Reconstitution of GM2 catabolism with β-hexosaminidase A and GM2 activator protein (GM2AP) at uncharged liposomal surfaces carrying GM2 as substrate generated only a physiologically irrelevant catabolic rate, even at pH 4.2. However, incorporation of anionic phospholipids into the GM2 carrying liposomes stimulated GM2 hydrolysis more than 10-fold, while the incorporation of plasma membrane stabilizing lipids (SM and cholesterol) generated a strong inhibition of GM2 hydrolysis, even in the presence of anionic phospholipids. Mobilization of membrane lipids by GM2AP was also inhibited in the presence of cholesterol or SM, as revealed by surface plasmon resonance studies. These lipids also reduced the interliposomal transfer rate of 2-NBD-GM1 by GM2AP, as observed in assays using Förster resonance energy transfer. Our data raise major concerns about the usage of recombinant His-tagged GM2AP compared with untagged protein. The former binds more strongly to anionic GM2-carrying liposomal surfaces, increases GM2 hydrolysis, and accelerates intermembrane transfer of 2-NBD-GM1, but does not mobilize membrane lipids. PMID:26175473

  3. An activation-collision mechanism for cholesterol transfer between membranes.

    PubMed

    Steck, T L; Kezdy, F J; Lange, Y

    1988-09-15

    We report the results of experiments which show that cholesterol transfer between membranes cannot proceed by aqueous diffusion, as widely held, but must involve a more complex mechanism. (a) The rate of transfer of [3H]cholesterol from red blood cells was found to vary inversely with the size of the acceptor particle (ghosts, vesicles of ghosts, liposomes, and plasma lipoproteins). (b) The transfer of [3H]cholesterol from red blood cells to ghosts was accelerated by the presence of plasma, even though the plasma competed with the ghosts as an acceptor. (c) The rate of transfer of [3H]cholesterol from red blood cells to ghosts decreased to zero with increasing dilution but was not simply second-order. (d) The cholesterol in retinal rod disc membranes is not at equilibrium with plasma lipoproteins in that disc cholesterol increased when the homogenates were incubated in vitro with plasma. (e) The kinetics of cholesterol transfer cannot be limited by unstirred layer effects since the transfer of lysolecithin in the same system was faster than that of cholesterol by 3 orders of magnitude. The simplest model compatible with all the data suggests a two-step pathway involving a first-order followed by a second-order process. The first step could be a unimolecular activation event, perhaps the movement of the sterol in the donor particle to a more exposed (hydrated) position. In the second step, the activated sterol would be transferred during transient collisions between donor and acceptor particles. When collision is not rate-limiting, the overall process would appear to be simply first-order, hence kinetically indistinguishable from the aqueous diffusion mechanism. The activation-collision model thus not only rationalizes our data but is also consistent with the simpler kinetics previously reported for the transfer of both membrane phospholipids and sterols.

  4. Optically active polyelectrolyte multilayers as membranes for chiral separations.

    PubMed

    Rmaile, Hassan H; Schlenoff, Joseph B

    2003-06-04

    Ultrathin films of chiral polyelectrolyte complex, prepared by the multilayering process, exhibit selectivity in the membrane separations of optically active compounds, such as l- and d-ascorbic acid. The flux through these polyelectrolyte multilayers, PEMUs, is exceptionally high and may be controlled by the concentration of salt present in the permeating solutions. Both in-situ ATR-FTIR and chiral capillary electrochromatography indicate that flux selectivity is mainly kinetically controlled, stemming from a difference in diffusion rates of various enantiomers through PEMUs, rather than a difference in partitioning.

  5. Hydrodynamic collective effects of active proteins in biological membranes

    NASA Astrophysics Data System (ADS)

    Koyano, Yuki; Kitahata, Hiroyuki; Mikhailov, Alexander S.

    2016-08-01

    Lipid bilayers forming biological membranes are known to behave as viscous two-dimensional fluids on submicrometer scales; usually they contain a large number of active protein inclusions. Recently, it was shown [A. S. Mikhailov and R. Kapral, Proc. Natl. Acad. Sci. USA 112, E3639 (2015), 10.1073/pnas.1506825112] that such active proteins should induce nonthermal fluctuating lipid flows leading to diffusion enhancement and chemotaxislike drift for passive inclusions in biomembranes. Here, a detailed analytical and numerical investigation of such effects is performed. The attention is focused on the situations when proteins are concentrated within lipid rafts. We demonstrate that passive particles tend to become attracted by active rafts and are accumulated inside them.

  6. Neuronal activity-dependent membrane traffic at the neuromuscular junction

    PubMed Central

    Miana-Mena, Francisco Javier; Roux, Sylvie; Benichou, Jean-Claude; Osta, Rosario; Brûlet, Philippe

    2002-01-01

    During development and also in adulthood, synaptic connections are modulated by neuronal activity. To follow such modifications in vivo, new genetic tools are designed. The nontoxic C-terminal fragment of tetanus toxin (TTC) fused to a reporter gene such as LacZ retains the retrograde and transsynaptic transport abilities of the holotoxin itself. In this work, the hybrid protein is injected intramuscularly to analyze in vivo the mechanisms of intracellular and transneuronal traffics at the neuromuscular junction (NMJ). Traffic on both sides of the synapse are strongly dependent on presynaptic neural cell activity. In muscle, a directional membrane traffic concentrates β-galactosidase-TTC hybrid protein into the NMJ postsynaptic side. In neurons, the probe is sorted across the cell to dendrites and subsequently to an interconnected neuron. Such fusion protein, sensitive to presynaptic neuronal activity, would be extremely useful to analyze morphological changes and plasticity at the NMJ. PMID:11880654

  7. Membrane perturbation activity of cationic phenylene ethynylene oligomers and polymers: selectivity against model bacterial and mammalian membranes.

    PubMed

    Wang, Ying; Tang, Yanli; Zhou, Zhijun; Ji, Eunkyung; Lopez, Gabriel P; Chi, Eva Y; Schanze, Kirk S; Whitten, David G

    2010-08-03

    Poly(phenylene ethyneylene) (PPE)-based cationic conjugated polyelectrolytes (CPEs) and cationic phenylene ethynylene oligomers (OPEs) exhibit broad-spectrum antimicrobial activity, and their main target is believed to be the cell membrane. To understand better how these antimicrobial molecules interact with membranes, a series of PPE-based CPEs and OPEs with different side chains were studied. Large unilamellar vesicles with lipid compositions mimicking those of mammalian or bacterial membranes were used as model membranes. Among the CPEs and OPEs tested, the anionic CPE, PPE-SO(3)(2-) and the smallest cationic OPE-1 are inactive against all vesicles. Other cationic CPEs and OPEs show significant membrane perturbation ability against bacterial membrane mimics but are inactive against a mammalian cell membrane mimic with the exception of PPE-DABCO and two end-only-functionalized OPEs, which also disrupted a mammalian cell membrane mimic. The results suggest that the phospholipid composition of vesicles dominates the interaction of CPE and OPE with lipid membranes.

  8. Influence of decavanadate on rat synaptic plasma membrane ATPases activity.

    PubMed

    Krstić, Danijela; Colović, Mirjana; Bosnjaković-Pavlović, Nada; Spasojević-De Bire, Anne; Vasić, Vesna

    2009-09-01

    The in vitro influence of decameric vanadate species on Na+/K+-ATPase, plasma membrane Ca2+-ATPase (PMCA)-calcium pump and ecto-ATPase activity, using rat synaptic plasma membrane (SPM) as model system was investigated, whereas the commercial porcine cerebral cortex Na+/K+-ATPase served as a reference. The thermal behaviour of the synthesized decavanadate (V10) has been studied by differential scanning calorimetry and thermogravimetric analysis, while the type of polyvanadate anion was identified using the IR spectroscopy. The concentration-dependent responses to V10 of all enzymes were obtained. The half-maximum inhibitory concentration (IC50) of the enzyme activity was achieved at (4.74 +/- 1.15) x 10(-7) mol/l for SPM Na+/K+-ATPase, (1.30 +/- 0.10) x 10(-6) mol/l for commercial Na+/K+-ATPase and (3.13 +/- 1.70) x 10(-8) mol/l for Ca2+-ATPase, while ecto-ATPase is significantly less sensitive toward V10 (IC50 = (1.05 +/- 0.10) x 10(-4) mol/l) than investigated P-type ATPases. Kinetic analysis showed that V10 inhibited Na+/K+-ATPase by reducing the maximum enzymatic velocity and apparent affinity for ATP (increasing K(m) value), implying a mixed mode of interaction between V10 and P-type ATPases.

  9. Effects of hydrostatic pressure on lipid bilayer membranes. I. Influence on membrane thickness and activation volumes of lipophilic ion transport.

    PubMed Central

    Benz, R; Conti, F

    1986-01-01

    Measurements of membrane capacitance, Cm, were performed on lipid bilayers of different lipidic composition (diphytanoyl phosphatidylcholine PPhPC, dioleoyl phosphatidylcholine DOPE, glycerylmonooleate GMO) and containing n-decane as solvent. In the same membranes, the absorption of the lipophilic ions dipicrylamine (DPA-) and tetraphenylborate (TPhB-), and the kinetics of their translocation between the two membrane faces have been studied. The data were obtained from charge pulse relaxation measurements. Upon increasing pressure the specific capacity Cm increased in a fully reversible and reproducible way reflecting a thinning of the membrane that is attributed to extrusion of n-decane from the black membrane area. High pressure decreased the rate constant, ki, for lipophilic ion translocation. After correcting for changes in the height of the energy barrier for translocation due to membrane thinning the pressure dependence of ki yields an apparent activation volume for translocation of approximately 14 cm3/mol both for DPA- and TPhB-. Changes in lipophilic ion absorption following a step of pressure developed with a rather slow time course due to diffusion limitations in solution. The stationary concentration of membrane absorbed lipophilic ions increased with pressure according to an apparent volume of absorption of about -10 cm3/mol. The relevance of the results for the interpretation of the effects of pressure on nerve membrane physiology is discussed. Images FIGURE 1 PMID:3730509

  10. Effect of lipid peroxidation on membrane-bound Ca2+-ATPase activity of the intestinal brush-border membranes.

    PubMed

    Ohta, A; Mohri, T; Ohyashiki, T

    1989-09-04

    We have studied lipid peroxidation and Ca2+-ATPase activity of the porcine intestinal brush-border membranes using a oxygen-radical-generating system consisting of dithiothreitol (DTT)/Fe2+ and tert-butyl hydroperoxide (t-BuOOH). The rates of lipid peroxidation were measured by formation of thiobarbituric acid-reactive substances (TBAR) and conjugated diene. Incubation of the membranes with DTT/Fe2+ in the absence and presence of t-BuOOH resulted in a slight (about 20%) and a marked (about 50%) inhibition of Ca2+-ATPase activity, respectively. The degree of inhibition was dependent on the hydroperoxide concentration. Addition of thiourea effectively protected Ca2+-ATPase activity but catalase and superoxide dismutase showed a slight and no effect on protection of the ATPase activity, respectively. Results of kinetic studies on the ATPase activity with varying ATP and Ca2+ concentrations revealed that the decrease in the enzyme activity by treatment with these oxidizing agents is mainly due to decrease of the Vmax value. Modification of SH groups in the membrane proteins by thiol group reagents such as N-ethylmaleimide, monoiodoacetate and monoiodacetamide did not induce the inhibition of Ca2+-ATPase activity. From these results, it is suggested that inhibition of the ATPase activity of the membranes by treatment with DTT/Fe2+ in the presence and absence of t-BuOOH is dependent on lipid peroxidation and that oxidative modification of SH groups may not be directly involved to the loss of the ATPase activity. In addition, results of the fluorescence anisotropy measurements of pyrene-labeled membranes suggested that change in the Ca2+-ATPase activity is partly related to a decrease in the membrane lipid fluidity.

  11. Cassava root membrane proteome reveals activities during storage root maturation.

    PubMed

    Naconsie, Maliwan; Lertpanyasampatha, Manassawe; Viboonjun, Unchera; Netrphan, Supatcharee; Kuwano, Masayoshi; Ogasawara, Naotake; Narangajavana, Jarunya

    2016-01-01

    Cassava (Manihot esculenta Crantz) is one of the most important crops of Thailand. Its storage roots are used as food, feed, starch production, and be the important source for biofuel and biodegradable plastic production. Despite the importance of cassava storage roots, little is known about the mechanisms involved in their formation. This present study has focused on comparison of the expression profiles of cassava root proteome at various developmental stages using two-dimensional gel electrophoresis and LC-MS/MS. Based on an anatomical study using Toluidine Blue, the secondary growth was confirmed to be essential during the development of cassava storage root. To investigate biochemical processes occurring during storage root maturation, soluble and membrane proteins were isolated from storage roots harvested from 3-, 6-, 9-, and 12-month-old cassava plants. The proteins with differential expression pattern were analysed and identified to be associated with 8 functional groups: protein folding and degradation, energy, metabolism, secondary metabolism, stress response, transport facilitation, cytoskeleton, and unclassified function. The expression profiling of membrane proteins revealed the proteins involved in protein folding and degradation, energy, and cell structure were highly expressed during early stages of development. Integration of these data along with the information available in genome and transcriptome databases is critical to expand knowledge obtained solely from the field of proteomics. Possible role of identified proteins were discussed in relation with the activities during storage root maturation in cassava.

  12. Red wine activates plasma membrane redox system in human erythrocytes.

    PubMed

    Tedesco, Idolo; Moccia, Stefania; Volpe, Silvestro; Alfieri, Giovanna; Strollo, Daniela; Bilotto, Stefania; Spagnuolo, Carmela; Di Renzo, Massimo; Aquino, Rita P; Russo, Gian Luigi

    2016-01-01

    In the present study, we report that polyphenols present in red wine obtained by a controlled microvinification process are able to protect human erythrocytes from oxidative stress and to activate Plasma Membrane Redox System (PMRS). Human plasma obtained from healthy subjects was incubated in the presence of whole red wine at a concentration corresponding to 9.13-73 μg/ml gallic acid equivalents to verify the capacity to protect against hypochlorous acid (HOCl)-induced plasma oxidation and to minimize chloramine formation. Red wine reduced hemolysis and chloramine formation induced by HOCl of 40 and 35%, respectively. PMRS present on human erythrocytes transfers electrons from intracellular molecules to extracellular electron acceptors. We demonstrated that whole red wine activated PMRS activity in human erythrocytes isolated from donors in a dose-dependent manner with a maximum at about 70-100 μg/ml gallic acid equivalents. We also showed that red wine increased glutathione (GSH) levels and erythrocytic antioxidant capacity, measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH) quenching assay. Furthermore, we reported that GSH played a crucial role in regulating PMRS activity in erythrocytes. In fact, the effect of iodoacetamide, an alkylating agent that induces depletion of intracellular GSH, was completely counteracted by red wine. Bioactive compounds present in red wine, such as gallic acid, resveratrol, catechin, and quercetin were unable to activate PMRS when tested at the concentrations normally present in aged red wines. On the contrary, the increase of PMRS activity was associated with the anthocyanin fraction, suggesting the capacity of this class of compounds to positively modulate PMRS enzymatic activity.

  13. Fusicoccin Binding to Its Plasma Membrane Receptor and the Activation of the Plasma Membrane H+-ATPase

    PubMed Central

    De Michelis, Maria Ida; Pugliarello, Maria Chiara; Rasi-Caldogno, Franca

    1989-01-01

    The characteristics of fusicoccin binding were investigated in microsomes from 24-h-old radish (Raphanus sativus L.) seedlings. The time course of fusicoccin binding depended on fusicoccin concentration: equilibrium was reached much faster at 10 nanomolar fusicoccin than at 0.3 nanomolar fusicoccin. Scatchard analysis of equilibrium binding as a function of fusicoccin concentration indicated a single class of receptor sites with a Kd of 1.8 nanomolar and a site density of 6.3 picomoles per milligram protein. Similar values (Kd 1.7 nanomolar and site density 7 picomoles per milligram protein) were obtained from the analysis of the dependence of equilibrium binding on membrane concentration at fixed fusicoccin concentrations. Fusicoccin binding comigrated with the plasma membrane H+-ATPase in an equilibrium sucrose density gradient: both activities formed a sharp peak (1.18 grams per milliliter) clearly distinct from that of markers of other membranes which all peaked at lower densities. The saturation profiles of fusicoccin binding and of fusicoccin-induced activation of the plasma membrane H+-ATPase, measured under identical conditions, were similar, supporting the view that fusicoccin-induced activation of the plasma membrane H+-ATPase is mediated by fusicoccin binding to its plasma membrane receptor. PMID:16666723

  14. Functional, photochemically active, and chemically asymmetric membranes by interfacial polymerization of derivatized multifunctional prepolymers

    DOEpatents

    Lonsdale, Harold K.; Wamser, Carl C.

    1990-01-01

    The preparation of a novel class of thin film membranes by interfacial polymerization is disclosed, said membranes incorporating as part of their polymeric structure the functionality of monomeric or oligomeric precursors. Specific embodiments include porphyrin and phthalocyanine derivatives that are photochemically or electrochemically active, as well as chemically asymmetric membranes.

  15. Functional, photochemically active, and chemically asymmetric membranes by interfacial polymerization of derivatized multifunctional prepolymers

    DOEpatents

    Lonsdale, H.K.; Wamser, C.C.

    1990-04-17

    The preparation of a novel class of thin film membranes by interfacial polymerization is disclosed, said membranes incorporating as part of their polymeric structure the functionality of monomeric or oligomeric precursors. Specific embodiments include porphyrin and phthalocyanine derivatives that are photochemically or electrochemically active, as well as chemically asymmetric membranes.

  16. Phosphatidic acid phosphatase and phospholipdase A activities in plasma membranes from fusing muscle cells.

    PubMed

    Kent, C; Vagelos, P R

    1976-06-17

    Plasma membrane from fusing embryonic muscle cells were assayed for phospholipase A activity to determine if this enzyme plays a role in cell fusion. The membranes were assayed under a variety of conditions with phosphatidylcholine as the substrate and no phospholipase A activity was found. The plasma membranes did contain a phosphatidic acid phosphatase which was optimally active in the presence of Triton X-100 and glycerol. The enzyme activity was constant from pH 5.2 to 7.0, and did not require divalent cations. Over 97% of the phosphatidic acid phosphatase activity was in the particulate fraction. The subcellular distribution of the phosphatidic acid phosphatase was the same as the distributions of the plasma membrane markers, (Na+ + k+)-ATPase and the acetylcholine receptor, which indicates that this phosphatase is located exclusively in the plasma membranes. There was no detectable difference in the phosphatidic acid phosphatase activities of plasma membranes from fusing and non-fusing cells.

  17. Activation of TRPV1 channels inhibits mechanosensitive Piezo channel activity by depleting membrane phosphoinositides.

    PubMed

    Borbiro, Istvan; Badheka, Doreen; Rohacs, Tibor

    2015-02-10

    Capsaicin is an activator of the heat-sensitive TRPV1 (transient receptor potential vanilloid 1) ion channels and has been used as a local analgesic. We found that activation of TRPV1 channels with capsaicin either in dorsal root ganglion neurons or in a heterologous expression system inhibited the mechanosensitive Piezo1 and Piezo2 channels by depleting phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and its precursor phosphatidylinositol 4-phosphate [PI(4)P] from the plasma membrane through Ca(2+)-induced phospholipase Cδ (PLCδ) activation. Experiments with chemically inducible phosphoinositide phosphatases and receptor-induced activation of PLCβ indicated that inhibition of Piezo channels required depletion of both PI(4)P and PI(4,5)P2. The mechanically activated current amplitudes decreased substantially in the excised inside-out configuration, where the membrane patch containing Piezo1 channels is removed from the cell. PI(4,5)P2 and PI(4)P applied to these excised patches inhibited this decrease. Thus, we concluded that Piezo channel activity requires the presence of phosphoinositides, and the combined depletion of PI(4,5)P2 and PI(4)P reduces channel activity. In addition to revealing a role for distinct membrane lipids in mechanosensitive ion channel regulation, these data suggest that inhibition of Piezo2 channels may contribute to the analgesic effect of capsaicin.

  18. LPS-Induced Macrophage Activation and Plasma Membrane Fluidity Changes are Inhibited Under Oxidative Stress.

    PubMed

    de la Haba, Carlos; Morros, Antoni; Martínez, Paz; Palacio, José R

    2016-12-01

    Macrophage activation is essential for a correct and efficient response of innate immunity. During oxidative stress membrane receptors and/or membrane lipid dynamics can be altered, leading to dysfunctional cell responses. Our aim is to analyze membrane fluidity modifications and cell function under oxidative stress in LPS-activated macrophages. Membrane fluidity of individual living THP-1 macrophages was evaluated by the technique two-photon microscopy. LPS-activated macrophage function was determined by TNFα secretion. It was shown that LPS activation causes fluidification of macrophage plasma membrane and production of TNFα. However, oxidative stress induces rigidification of macrophage plasma membrane and inhibition of cell activation, which is evidenced by a decrease of TNFα secretion. Thus, under oxidative conditions macrophage proinflammatory response might develop in an inefficient manner.

  19. Pneumolysin activates macrophage lysosomal membrane permeabilization and executes apoptosis by distinct mechanisms without membrane pore formation.

    PubMed

    Bewley, Martin A; Naughton, Michael; Preston, Julie; Mitchell, Andrea; Holmes, Ashleigh; Marriott, Helen M; Read, Robert C; Mitchell, Timothy J; Whyte, Moira K B; Dockrell, David H

    2014-10-07

    Intracellular killing of Streptococcus pneumoniae is complemented by induction of macrophage apoptosis. Here, we show that the toxin pneumolysin (PLY) contributes both to lysosomal/phagolysosomal membrane permeabilization (LMP), an upstream event programing susceptibility to apoptosis, and to apoptosis execution via a mitochondrial pathway, through distinct mechanisms. PLY is necessary but not sufficient for the maximal induction of LMP and apoptosis. PLY's ability to induce both LMP and apoptosis is independent of its ability to form cytolytic pores and requires only the first three domains of PLY. LMP involves TLR (Toll-like receptor) but not NLRP3/ASC (nucleotide-binding oligomerization domain [Nod]-like receptor family, pyrin domain-containing protein 3/apoptosis-associated speck-like protein containing a caspase recruitment domain) signaling and is part of a PLY-dependent but phagocytosis-independent host response that includes the production of cytokines, including interleukin-1 beta (IL-1β). LMP involves progressive and selective permeability to 40-kDa but not to 250-kDa fluorescein isothiocyanate (FITC)-labeled dextran, as PLY accumulates in the cytoplasm. In contrast, the PLY-dependent execution of apoptosis requires phagocytosis and is part of a host response to intracellular bacteria that also includes NO generation. In cells challenged with PLY-deficient bacteria, reconstitution of LMP using the lysomotrophic detergent LeuLeuOMe favored cell necrosis whereas PLY reconstituted apoptosis. The results suggest that PLY contributes to macrophage activation and cytokine production but also engages LMP. Following bacterial phagocytosis, PLY triggers apoptosis and prevents macrophage necrosis as a component of a broad-based antimicrobial strategy. This illustrates how a key virulence factor can become the focus of a multilayered and coordinated innate response by macrophages, optimizing pathogen clearance and limiting inflammation. Importance: Streptococcus

  20. Carbonic anhydrase activity in Arabidopsis thaliana thylakoid membrane and fragments enriched with PSI or PSII.

    PubMed

    Ignatova, Lyudmila K; Rudenko, Natalia N; Mudrik, Vilen A; Fedorchuk, Tat'yana P; Ivanov, Boris N

    2011-12-01

    The procedure of isolating the thylakoids and the thylakoid membrane fragments enriched with either photosystem I or photosystem II (PSI- and PSII-membranes) from Arabidopsis thaliana leaves was developed. It differed from the one used with pea and spinach in durations of detergent treatment and centrifugation, and in concentrations of detergent and Mg(2+) in the media. Both the thylakoid and the fragments preserved carbonic anhydrase (CA) activities. Using nondenaturing electrophoresis followed by detection of CA activity in the gel stained with bromo thymol blue, one low molecular mass carrier of CA activity was found in the PSI-membranes, and two carriers, a low molecular mass one and a high molecular mass one, were found in the PSII-membranes. The proteins in the PSII-membranes differed in their sensitivity to acetazolamide (AA), a specific CA inhibitor. AA at 5 × 10(-7) M inhibited the CA activity of the high molecular mass protein but stimulated the activity of the low molecular mass carrier in the PSII-membranes. At the same concentration, AA moderately inhibited, by 30%, the CA activity of PSI-membranes. CA activity of the PSII-membranes was almost completely suppressed by the lipophilic CA inhibitor, ethoxyzolamide at 10(-9) M, whereas CA activity of the PSI-membranes was inhibited by this inhibitor even at 5 × 10(-7) M just the same as for AA. The observed distribution of CA activity in the thylakoid membranes from A. thaliana was close to the one found in the membranes of pea, evidencing the general pattern of CA activity in the thylakoid membranes of C3-plants.

  1. The DART Cylindrical, Infrared, 1 Meter Membrane Reflector

    NASA Technical Reports Server (NTRS)

    Morgan, Rhonda M.; Agnes, Greg S.; Barber, Dan; Dooley, Jennifer; Dragovan, Mark; Hatheway, Al E.; Marcin, Marty

    2004-01-01

    The Dual Anamorphic Reflector Telescopes (DART) is an architecture for large aperture space telescopes that enables the use of membranes. A membrane can be readily shaped in one direction of curvature using a combination of boundary control and tensioning, yielding a cylindrical reflector. Two cylindrical reflectors (orthogonal and confocal) comprise the 'primary mirror' of the telescope system. The aperture is completely unobstructed and ideal for infrared and high contrast observations.

  2. How Lipid Membranes Affect Pore Forming Toxin Activity.

    PubMed

    Rojko, Nejc; Anderluh, Gregor

    2015-12-15

    Pore forming toxins (PFTs) evolved to permeate the plasma membrane of target cells. This is achieved in a multistep mechanism that usually involves binding of soluble protein monomer to the lipid membrane, oligomerization at the plane of the membrane, and insertion of part of the polypeptide chain across the lipid membrane to form a conductive channel. Introduced pores allow uncontrolled transport of solutes across the membrane, inflicting damage to the target cell. PFTs are usually studied from the perspective of structure-function relationships, often neglecting the important role of the bulk membrane properties on the PFT mechanism of action. In this Account, we discuss how membrane lateral heterogeneity, thickness, and fluidity influence the pore forming process of PFTs. In general, lipid molecules are more accessible for binding in fluid membranes due to steric reasons. When PFT specifically binds ordered domains, it usually recognizes a specific lipid distribution pattern, like sphingomyelin (SM) clusters or SM/cholesterol complexes, and not individual lipid species. Lipid domains were also suggested to act as an additional concentration platform facilitating PFT oligomerization, but this is yet to be shown. The last stage in PFT action is the insertion of the transmembrane segment across the membranes to build the transmembrane pore walls. Conformational changes are a spontaneous process, and sufficient free energy has to be available for efficient membrane penetration. Therefore, fluid bilayers are permeabilized more readily in comparison to highly ordered and thicker liquid ordered lipid phase (Lo). Energetically more costly insertion into the Lo phase can be driven by the hydrophobic mismatch between the thinner liquid disordered phase (Ld) and large protein complexes, which are unable to tilt like single transmembrane segments. In the case of proteolipid pores, membrane properties can directly modulate pore size, stability, and even selectivity. Finally

  3. Enzymatically active high-flux selectively gas-permeable membranes

    SciTech Connect

    Jiang, Ying-Bing; Cecchi, Joseph L.; Rempe, Susan; FU, Yaqin; Brinker, C. Jeffrey

    2016-01-26

    An ultra-thin, catalyzed liquid transport medium-based membrane structure fabricated with a porous supporting substrate may be used for separating an object species such as a carbon dioxide object species. Carbon dioxide flux through this membrane structures may be several orders of magnitude higher than traditional polymer membranes with a high selectivity to carbon dioxide. Other gases such as molecular oxygen, molecular hydrogen, and other species including non-gaseous species, for example ionic materials, may be separated using variations to the membrane discussed.

  4. Activation of a heat-stable cytolytic protein associated with the surface membrane of Naegleria fowleri.

    PubMed Central

    Lowrey, D M; McLaughlin, J

    1985-01-01

    Surface membrane-enriched fractions of Naegleria fowleri obtained after isopycnic centrifugation experiments contain a potent cytolytic activity as determined by hemolysis and 51Cr release assays. This surface membrane cytolysin was unaffected by a treatment at 75 degrees C for 30 min and accounted for 70 to 90% of cytolysis by whole-cell lysates of amoebae. This heat resistance as well as intimate membrane association distinguished the surface membrane cytolytic activity from a second heat-labile cytolytic activity which appears to be latent within lysosomes. The surface membrane cytolysin was found to be specifically activated by diluted samples of lysosomal fractions. The possible role of this surface membrane cytotoxin in the pathogenicity of N. fowleri is discussed. PMID:4055029

  5. Membrane-associated forms of peptidylglycine alpha-amidating monooxygenase activity in rat pituitary. Tissue specificity.

    PubMed

    May, V; Cullen, E I; Braas, K M; Eipper, B A

    1988-06-05

    Membrane-associated peptidylglycine alpha-amidating monooxygenase (PAM) activity was investigated in rat anterior and neurointermediate pituitary tissues and in pituitary AtT-20/D-16v and GH3 cell lines. A substantial fraction of total pituitary PAM activity was found to be membrane-associated. Triton X-100, N-octyl-beta-D-glucopyranoside, and Zwittergent were effective in solubilizing PAM activity from crude pituitary membranes. The distribution of enzyme activity between soluble and membrane-associated forms was tissue-specific. In the anterior pituitary lobe and pituitary cell lines, 40-60% of total PAM activity was membrane-associated while only 10% of the alpha-amidating activity in the neurointermediate lobe was membrane-associated. Soluble and membrane-associated forms of PAM shared nearly identical characteristics with respect to copper and ascorbate requirements, pH optima, and Km values. Upon subcellular fractionation of anterior and neurointermediate pituitary lobe homogenates on Percoll gradients, 12-18% of total PAM activity was found in the rough endoplasmic reticulum/Golgi fractions and 42-60% was localized to secretory granule fractions. For both tissues, membrane-associated PAM activity was enriched in the rough endoplasmic reticulum/Golgi pool, whereas most of the secretory granule-associated enzyme activity was soluble.

  6. Detergent disruption of bacterial inner membranes and recovery of protein translocation activity

    SciTech Connect

    Cunningham, K.; Wickner, W.T. )

    1989-11-01

    Isolation of the integral membrane components of protein translocation requires methods for fractionation and functional reconstitution. The authors treated inner-membrane vesicles of Escherichia coli with mixtures of octyl {beta}-D-glucoside, phospholipids, and an integral membrane carrier protein under conditions that extract most of the membrane proteins into micellar solution. Upon dialysis, proteoliposomes were reconstituted that supported translocation of radiochemically pure ({sup 35}S)pro-OmpA (the precursor of outer membrane protein A). Translocation into these proteoliposomes required ATP hydrolysis and membrane proteins, indicating that the reaction is that of the inner membrane. The suspension of membranes in detergent was separated into supernatant and pellet fractions by ultracentrifugation. After reconstitution, translocation activity was observed in both fractions, but processing by leader peptidase of translocated pro-OmpA to OmpA was not detectable in the reconstituted pellet fraction. Processing activity was restored by addition of pure leader peptidase as long as this enzyme was added before detergent removal, indicating that the translocation activity is not associated with detergent-resistant membrane vesicles. These results show that protein translocation activity can be recovered from detergent-disrupted membrane vesicles, providing a first step towards the goal of isolating the solubilized components.

  7. Salt stress in a membrane bioreactor: dynamics of sludge properties, membrane fouling and remediation through powdered activated carbon dosing.

    PubMed

    De Temmerman, L; Maere, T; Temmink, H; Zwijnenburg, A; Nopens, I

    2014-10-15

    Membrane bioreactors are a well-established technology for wastewater treatment. However, their efficiency is adversely impacted by membrane fouling, primarily inciting very conservative operations of installations that makes them less appealing from an economic perspective. This fouling propensity of the activated sludge is closely related to system disturbances. Therefore, improved insight into the impact of fouling is crucial towards increased membrane performance. In this work, the disturbance of a salt shock was investigated with respect to sludge composition and filterability in two parallel lab-scale membrane bioreactors. Several key sludge parameters (soluble microbial products, sludge-bound extracellular polymeric substances, supramicron particle size distributions (PSD), submicron particle concentrations) were intensively monitored prior to, during, and after a disturbance to investigate its impact as well as the potential governing mechanism. Upon salt addition, the supramicron PSD immediately shifted to smaller floc sizes, and the total fouling rate increased. Following a certain delay, an increase in submicron particles, supernatant proteins, and polysaccharides was observed as well as an increase in the irreversible membrane fouling rate. Recovery from the disturbance was evidenced with a simultaneous decrease in the above mentioned quantities. A similar experiment introducing powdered activated carbon (PAC) addition used for remediation resulted in either no or less significant changes in the above mentioned quantities, signifying its potential as a mitigation strategy.

  8. Myomaker: A membrane activator of myoblast fusion and muscle formation

    PubMed Central

    Millay, Douglas P.; O’Rourke, Jason R.; Sutherland, Lillian B.; Bezprozvannaya, Svetlana; Shelton, John M.; Bassel-Duby, Rhonda; Olson, Eric N.

    2013-01-01

    Summary Fusion of myoblasts is essential for the formation of multi-nucleated muscle fibers. However, the identity of myogenic proteins that directly govern this fusion process has remained elusive. Here, we discovered a muscle-specific membrane protein, named Myomaker, that controls myoblast fusion. Myomaker is expressed on the cell surface of myoblasts during fusion and is down-regulated thereafter. Over-expression of Myomaker in myoblasts dramatically enhances fusion and genetic disruption of Myomaker in mice causes perinatal death due to an absence of multi-nucleated muscle fibers. Remarkably, forced expression of Myomaker in fibroblasts promotes fusion with myoblasts, demonstrating the direct participation of this protein in the fusion process. Pharmacologic perturbation of the actin cytoskeleton abolishes the activity of Myomaker, consistent with prior studies implicating actin dynamics in myoblast fusion. These findings reveal a long-sought myogenic fusion protein both necessary and sufficient for mammalian myoblast fusion and provide new insights into the molecular underpinnings of muscle formation. PMID:23868259

  9. Circulating polymerase chain reaction chips utilizing multiple-membrane activation

    NASA Astrophysics Data System (ADS)

    Wang, Chih-Hao; Chen, Yi-Yu; Liao, Chia-Sheng; Hsieh, Tsung-Min; Luo, Ching-Hsing; Wu, Jiunn-Jong; Lee, Huei-Huang; Lee, Gwo-Bin

    2007-02-01

    This paper reports a new micromachined, circulating, polymerase chain reaction (PCR) chip for nucleic acid amplification. The PCR chip is comprised of a microthermal control module and a polydimethylsiloxane (PDMS)-based microfluidic control module. The microthermal control modules are formed with three individual heating and temperature-sensing sections, each modulating a specific set temperature for denaturation, annealing and extension processes, respectively. Micro-pneumatic valves and multiple-membrane activations are used to form the microfluidic control module to transport sample fluids through three reaction regions. Compared with other PCR chips, the new chip is more compact in size, requires less time for heating and cooling processes, and has the capability to randomly adjust time ratios and cycle numbers depending on the PCR process. Experimental results showed that detection genes for two pathogens, Streptococcus pyogenes (S. pyogenes, 777 bps) and Streptococcus pneumoniae (S. pneumoniae, 273 bps), can be successfully amplified using the new circulating PCR chip. The minimum number of thermal cycles to amplify the DNA-based S. pyogenes for slab gel electrophoresis is 20 cycles with an initial concentration of 42.5 pg µl-1. Experimental data also revealed that a high reproducibility up to 98% could be achieved if the initial template concentration of the S. pyogenes was higher than 4 pg µl-1. The preliminary results of the current paper were presented at the 19th IEEE International Conference on Micro Electro Mechanical Systems (IEEE MEMS 2006), Istanbul, Turkey, 22-26 January, 2006.

  10. [The effect of limiting neuronal energy metabolism on the level of impulse activity and membrane potentials].

    PubMed

    Voronova, N V; Chumachenko, A A

    1989-01-01

    The changes of the membrane potential and the frequency of impulse activity of the crayfish stretch receptor neuron have been studied under condition of energy supply deficiency. The energetic metabolism inhibitors have been found not to exert a significant effect on the membrane potential. The activity of the glycolysis process and the Krebs cycle have different effect on the sensitivity of the generating mechanism.

  11. Oxygen activation at the plasma membrane: relation between superoxide and hydroxyl radical production by isolated membranes.

    PubMed

    Heyno, Eiri; Mary, Véronique; Schopfer, Peter; Krieger-Liszkay, Anja

    2011-07-01

    Production of reactive oxygen species (hydroxyl radicals, superoxide radicals and hydrogen peroxide) was studied using EPR spin-trapping techniques and specific dyes in isolated plasma membranes from the growing and the non-growing zones of hypocotyls and roots of etiolated soybean seedlings as well as coleoptiles and roots of etiolated maize seedlings. NAD(P)H mediated the production of superoxide in all plasma membrane samples. Hydroxyl radicals were only produced by the membranes of the hypocotyl growing zone when a Fenton catalyst (FeEDTA) was present. By contrast, in membranes from other parts of the seedlings a low rate of spontaneous hydroxyl radical formation was observed due to the presence of small amounts of tightly bound peroxidase. It is concluded that apoplastic hydroxyl radical generation depends fully, or for the most part, on peroxidase localized in the cell wall. In soybean plasma membranes from the growing zone of the hypocotyl pharmacological tests showed that the superoxide production could potentially be attributed to the action of at least two enzymes, an NADPH oxidase and, in the presence of menadione, a quinone reductase.

  12. Effect of membranes with various hydrophobic/hydrophilic properties on lipase immobilized activity and stability.

    PubMed

    Chen, Guan-Jie; Kuo, Chia-Hung; Chen, Chih-I; Yu, Chung-Cheng; Shieh, Chwen-Jen; Liu, Yung-Chuan

    2012-02-01

    In this study, three membranes: regenerated cellulose (RC), glass fiber (GF) and polyvinylidene fluoride (PVDF), were grafted with 1,4-diaminobutane (DA) and activated with glutaraldehyde (GA) for lipase covalent immobilization. The efficiencies of lipases immobilized on these membranes with different hydrophobic/hydrophilic properties were compared. The lipase immobilized on hydrophobic PVDF-DA-GA membrane exhibited more than an 11-fold increase in activity compared to its immobilization on a hydrophilic RC-DA-GA membrane. The relationship between surface hydrophobicity and immobilized efficiencies was investigated using hydrophobic/hydrophilic GF membranes which were prepared by grafting a different ratio of n-butylamine/1,4-diaminobutane (BA/DA). The immobilized lipase activity on the GF membrane increased with the increased BA/DA ratio. This means that lipase activity was exhibited more on the hydrophobic surface. Moreover, the modified PVDF-DA membrane was grafted with GA, epichlorohydrin (EPI) and cyanuric chloride (CC), respectively. The lipase immobilized on the PVDF-DA-EPI membrane displayed the highest specific activity compared to other membranes. This immobilized lipase exhibited more significant stability on pH, thermal, reuse, and storage than did the free enzyme. The results exhibited that the EPI modified PVDF is a promising support for lipase immobilization.

  13. Large-aperture fast multilevel Fresnel zone lenses in glass and ultrathin polymer films for visible and near-infrared imaging applications.

    PubMed

    Britten, Jerald A; Dixit, Shamusundar N; DeBruyckere, Michael; Steadfast, Daniel; Hackett, James; Farmer, Brandon; Poe, Garrett; Patrick, Brian; Atcheson, Paul D; Domber, Jeanette L; Seltzer, Aaron

    2014-04-10

    The ability to fabricate 4-level diffractive structures with 1 µm critical dimensions has been demonstrated for the creation of fast (∼f/3.1 at 633 nm) Fresnel zone lenses (FZLs) with >60% diffraction efficiency into the -1 focusing order and nearly complete suppression of 0 and +1 orders. This is done using tooling capable of producing optics with 800 mm apertures. A 4-level grating fabricated in glass at 300 mm aperture is shown to have <15  nm rms holographic phase error. Glass FZLs have also been used as mandrels for casting zero-thermal-expansion, 20 µm thick polymer films created with the 4-level structure as a route to mass replication of efficient diffractive membranes for ultralight segmented space-based telescope applications.

  14. Electrospun nanofiber membranes for electrically activated shape memory nanocomposites

    NASA Astrophysics Data System (ADS)

    Zhang, Fenghua; Zhang, Zhichun; Liu, Yanju; Leng, Jinsong

    2014-06-01

    A novel shape memory nanocomposite system, consisting of a thermoplastic Nafion polymer and ultrathin electrospun polyacrylonitrile (PAN)-based carbonization nanofiber membranes, is successfully synthesized. PAN-based carbonization nanofiber networks that offer responses to deformations are considered to be an excellent actuation source. Significant improvement in the electrical conductivity of carbon nanofiber membranes is found by adjusting the applied voltage power in the electrospinning PAN process varying from 7.85 to 12.30 S cm-1. The porous structure of the carbon nanofiber membranes provides a large specific surface area and interfacial contact area when combined with the polymer matrix. Shape memory Nafion nanocomposites filled with interpenetrating non-woven electrospun PAN carbonization membranes can be actuated by applying 14 V electrical voltage within 5 s. The results, as demonstrated through morphology, electrical and thermal measurements and a shape recovery test, suggest a valuable route to producing soft nanocomposites.

  15. Quantification of Lysosomal Membrane Permeabilization by Cytosolic Cathepsin and β-N-Acetyl-Glucosaminidase Activity Measurements.

    PubMed

    Jäättelä, Marja; Nylandsted, Jesper

    2015-11-02

    Programmed cell death involving lysosomal membrane permeabilization (LMP) is an alternative cell death pathway induced under various cellular conditions and by numerous cytotoxic stimuli. The method presented here to quantify LMP takes advantage of the detergent digitonin, which creates pores in cellular membranes by replacing cholesterol. The difference in cholesterol content between the plasma membrane (high) and lysosomal membrane (low) allows titration of digitonin to a concentration that permeabilizes the plasma membrane but leaves lysosomal membranes intact. The extent of LMP is determined by measuring the cytosolic activity of lysosomal hydrolases (e.g., cysteine cathepsins) and/or β-N-acetyl-glucosaminidase in the digitonin-extracted cytoplasm and comparing it to the total cellular enzyme activity. Digitonin extraction of the cytosol can be combined with precipitation of protein and/or western blot analysis for detection of lysosomal proteins (e.g., cathepsins).

  16. Alteration of membrane phospholipid methylation by adenosine analogs does not affect T lymphocyte activation

    SciTech Connect

    Gormand, F.; Pacheco, Y. ); Fonlupt, P. ); Revillard, J.P. )

    1990-01-01

    Membrane phospholipid methylation has been described during activation of various immune cells. Moreover recent data indicated modulation of immune cells functions by adenosine. As S-adenosyl-methionine and S-adenosyl-homocysteine are adenosine analogs and modulators of transmethylation reactions, the effects of SAH and SAM were investigated on membrane phospholipid methylation and lymphocyte activation. SAM was shown to induce the membrane phospholipid methylation as assessed by the {sup 3}Hmethyl-incorporation in membrane extract. This effect was inhibited by SAH. In contrast SAM and SAH did not affect the phytohemagglutinin-induced proliferative response of peripheral blood mononuclear cells. SAH neither modified the early internalization of membrane CD3 antigens nor did it prevent the late expression of HLA-DR antigens on lymphocytes activated by phytohemagglutinin. These results indicate that in vitro alteration of phospholipid methylation does not affect subsequent steps of human T lymphocyte activation and proliferation.

  17. Visualization of Src activity at different compartments of the plasma membrane by FRET imaging

    PubMed Central

    Seong, Jihye; Lu, Shaoying; Ouyang, Mingxing; Huang, He; Zhang, Jin; Frame, Margaret C.; Wang, Yingxiao

    2009-01-01

    Summary Membrane compartments function as segregated signaling platforms for different cellular functions. It is not clear how Src is regulated at different membrane compartments. To visualize local Src activity in live cells, a FRET-based Src biosensor was targeted in or outside of lipid rafts at the plasma membrane, via acylation or prenylation modifications on targeting tags either directly fused to the biosensor or coupled to the biosensor through an inducible heterodimerization system. In response to growth factors and pervanadate, the induction of Src activity in rafts was slower and weaker, dependent on actin and possibly its mediated transportation of Src from perinuclear regions to the plasma membrane. In contrast, the induction of Src activity in non-rafts was faster and stronger, dependent on microtubules. Hence, the Src activity is differentially regulated via cytoskeleton at different membrane compartments. PMID:19171305

  18. Influence of the lipid membrane environment on structure and activity of the outer membrane protein Ail from Yersinia pestis

    PubMed Central

    Ding, Yi; Fujimoto, L. Miya; Yao, Yong; Plano, Gregory V.; Marassi, Francesca M.

    2014-01-01

    The surrounding environment has significant consequences for the structural and functional properties of membrane proteins. While native structure and function can be reconstituted in lipid bilayer membranes, the detergents used for protein solubilization are not always compatible with biological activity and, hence, not always appropriate for direct detection of ligand binding by NMR spectroscopy. Here we describe how the sample environment affects the activity of the outer membrane protein Ail (attachment invasion locus) from Yersinia pestis. Although Ail adopts the correct β-barrel fold in micelles, the high detergent concentrations required for NMR structural studies are not compatible with the ligand binding functionality of the protein. We also describe preparations of Ail embedded in phospholipid bilayer nanodiscs, optimized for NMR studies and ligand binding activity assays. Ail in nanodiscs is capable of binding its human ligand fibronectin and also yields high quality NMR spectra that reflect the proper fold. Binding activity assays, developed to be performed directly with the NMR samples, show that ligand binding involves the extracellular loops of Ail. The data show that even when detergent micelles support the protein fold, detergents can interfere with activity in subtle ways. PMID:25433311

  19. Actomyosin dynamics drive local membrane component organization in an in vitro active composite layer

    PubMed Central

    Husain, Kabir; Iljazi, Elda; Bhat, Abrar; Bieling, Peter; Mullins, R. Dyche; Rao, Madan; Mayor, Satyajit

    2016-01-01

    The surface of a living cell provides a platform for receptor signaling, protein sorting, transport, and endocytosis, whose regulation requires the local control of membrane organization. Previous work has revealed a role for dynamic actomyosin in membrane protein and lipid organization, suggesting that the cell surface behaves as an active composite composed of a fluid bilayer and a thin film of active actomyosin. We reconstitute an analogous system in vitro that consists of a fluid lipid bilayer coupled via membrane-associated actin-binding proteins to dynamic actin filaments and myosin motors. Upon complete consumption of ATP, this system settles into distinct phases of actin organization, namely bundled filaments, linked apolar asters, and a lattice of polar asters. These depend on actin concentration, filament length, and actin/myosin ratio. During formation of the polar aster phase, advection of the self-organizing actomyosin network drives transient clustering of actin-associated membrane components. Regeneration of ATP supports a constitutively remodeling actomyosin state, which in turn drives active fluctuations of coupled membrane components, resembling those observed at the cell surface. In a multicomponent membrane bilayer, this remodeling actomyosin layer contributes to changes in the extent and dynamics of phase-segregating domains. These results show how local membrane composition can be driven by active processes arising from actomyosin, highlighting the fundamental basis of the active composite model of the cell surface, and indicate its relevance to the study of membrane organization. PMID:26929326

  20. Membrane ruffles capture C3bi-opsonized particles in activated macrophages.

    PubMed

    Patel, Prerna C; Harrison, Rene E

    2008-11-01

    A widespread belief in phagocyte biology is that FcgammaR-mediated phagocytosis utilizes membrane pseudopods, whereas Mac-1-mediated phagocytosis does not involve elaborate plasma membrane extensions. Here we report that dynamic membrane ruffles in activated macrophages promote binding of C3bi-opsonized particles. We identify these ruffles as components of the macropinocytosis machinery in both PMA- and LPS-stimulated macrophages. C3bi-particle capture is facilitated by enrichment of high-affinity Mac-1 and the integrin-regulating protein talin in membrane ruffles. Membrane ruffle formation and C3bi-particle binding are cytoskeleton dependent events, having a strong requirement for F-actin and microtubules (MTs). MT disruption blunts ruffle formation and PMA- and LPS-induced up-regulation of surface Mac-1 expression. Furthermore, the MT motor, kinesin participates in ruffle formation implicating a requirement for intracellular membrane delivery to active membrane regions during Mac-1-mediated phagocytosis. We observed colocalization of Rab11-positive vesicles with CLIP-170, a MT plus-end binding protein, at sites of particle adherence using TIRF imaging. Rab11 has been implicated in recycling endosome dynamics and mutant Rab11 expression inhibits both membrane ruffle formation and C3bi-sRBC adherence to macrophages. Collectively these findings represent a novel membrane ruffle "capture" mechanism for C3bi-particle binding during Mac-1-mediated phagocytosis. Importantly, this work also demonstrates a strong functional link between integrin activation, macropinocytosis and phagocytosis in macrophages.

  1. Saturated fatty acids induce c-Src clustering within membrane subdomains leading to JNK activation

    PubMed Central

    Holzer, Ryan G.; Park, Eek-Joong; Li, Ning; Tran, Helen; Chen, Monica; Choi, Crystal; Solinas, Giovanni; Karin, Michael

    2011-01-01

    Saturated fatty acids (FA) exert adverse health effects and are more likely to cause insulin resistance and type 2 diabetes than unsaturated FA, some of which exert protective and beneficial effects. Saturated FA, but not unsaturated FA, activate Jun N terminal kinase (JNK), which has been linked to obesity and insulin resistance in mice and men. However, it is unknown how saturated and unsaturated FA are discriminated. We now demonstrate that saturated FA activate JNK and induce insulin resistance by altering the membrane distribution of c-Src, causing it to partition into intracellular membrane subdomains where it may become activated. Conversely, unsaturated FA with known beneficial effects on glucose metabolism prevent c-Src membrane partitioning and activation, which are dependent on its myristoylation, and block JNK activation. Consumption of a diabetogenic high fat diet causes the partitioning and activation of c-Src within detergent insoluble membrane subdomains of adipocytes. PMID:21962514

  2. Influence of activating hormones on human platelet membrane Ca/sup 2 +/-ATPase activity

    SciTech Connect

    Resink, T.J.; Dimitrov, D.; Stucki, S.; Buehler, F.R.

    1986-07-16

    Intact platelets were pretreated with hormones and thereafter membranes were prepared and Ca/sup 2 +/-ATPase activity determined. Thrombin decreased the V/sub max/ of Ca/sup 2 +/-ATPase after pretreatment of intact platelets. Platelet activating factor, vasopressin and ADP also decreased Ca/sup 2 +/-ATPase activity. 12-O-tetradecanoylphorbol-13-acetate (TPA) or A23187 or ionomycin alone had no effect, while the simultaneous pretreatment with TPA and Ca/sup 2 +/-ionophore decreased Ca/sup 2 +/-ATPase activity. cAMP elevating agents prostaglandin E/sub 1/ (PGE/sub 1/) and forskolin had no influence per se on Ca/sup 2 +/-ATPase, but antagonized the inhibitory effect of thrombin. The data suggest a close connection between phosphoinositide metabolism and the Ca/sup 2 +/-ATPase system.

  3. Functional, photochemically active, and chemically asymmetric membranes by interfacial polymerization of derivatized multifunctional prepolymers

    DOEpatents

    Lonsdale, Harold K.; Wamser, Carl C.

    1988-01-01

    The preparation of a novel class of thin film membranes by interfacial polymerization is disclosed, said membanes incorporating as part of their polymeric structure the functionality of monomeric or oligomeric precursors. Specific embodiments include porphyrin and phthalocyanime derivatives that are photochemically or electrochemically active, as well as chemically asymmetric membranes.

  4. One-way membrane trafficking of SOS in receptor-triggered Ras activation

    PubMed Central

    Christensen, Sune M.; Tu, Hsiung-Lin; Jun, Jesse E.; Alvarez, Steven; Triplet, Meredith G.; Iwig, Jeffrey S.; Yadav, Kamlesh K.; Bar-Sagi, Dafna; Roose, Jeroen P.; Groves, Jay T.

    2016-01-01

    SOS is a key activator of the small GTPase Ras. In cells, SOS-Ras signaling is thought to be initiated predominantly by membrane-recruitment of SOS via the adaptor Grb2 and balanced by rapidly reversible Grb2:SOS binding kinetics. However, SOS has multiple protein and lipid interactions that provide linkage to the membrane. In reconstituted membrane experiments, these Grb2-independent interactions are sufficient to retain SOS on the membrane for many minutes, during which a single SOS molecule can processively activate thousands of Ras molecules. These observations raise questions concerning how receptors maintain control of SOS in cells and how membrane-recruited SOS is ultimately released. We addressed these questions in quantitative reconstituted SOS-deficient chicken B cell signaling systems combined with single molecule measurements in supported membranes. These studies reveal an essentially one-way trafficking process in which membrane-recruited SOS remains trapped on the membrane and continuously activates Ras until it is actively removed via endocytosis. PMID:27501536

  5. Improved PVDF membrane performance by doping extracellular polymeric substances of activated sludge.

    PubMed

    Guan, Yan-Fang; Huang, Bao-Cheng; Qian, Chen; Wang, Long-Fei; Yu, Han-Qing

    2017-04-15

    Polyvinylidene fluoride (PVDF) membrane has been widely applied in water and wastewater treatment because of its high mechanical strength, thermal stability and chemical resistance. However, the hydrophobic nature of PVDF membrane makes it readily fouled, substantially reducing water flux and overall membrane rejection ability. In this work, an in-situ blending modifier, i.e., extracellular polymeric substances (EPS) from activated sludge, was used to enhance the anti-fouling ability of PVDF membrane. Results indicate that the pure water flux of the membrane and its anti-fouling performance were substantially improved by blending 8% EPS into the membrane. By introducing EPS, the membrane hydrophilicity was increased and the cross section morphology was changed when it interacted with polyvinl pyrrolidone, resulting in the formation of large cavities below the finger-like pores. In addition, the fraction of pores with a size of 100-500 nm increased, which was also beneficial to improving membrane performance. Surface thermodynamic calculations indicate the EPS-functionalized membrane had a higher cohesion free energy, implying its good pollutant rejection and anti-fouling ability. This work provides a simple, efficient and cost-effective method to improve membrane performance and also extends the applications of EPS.

  6. Enhancement of RNA Polymerase Activity by a Factor Released by Auxin from Plasma Membrane*

    PubMed Central

    Hardin, James W.; Cherry, Joe H.; Morré, D. James; Lembi, Carole A.

    1972-01-01

    Using recently developed techniques for solubilization of RNA polymerase from soybean chromatin and isolation of plasma membrane fractions from plants we can show the presence of a transcriptional factor specifically released from the membranes by auxin, 2,4-dichlorophenoxyacetic acid. The nonauxin, 3,5-dichlorophenoxyacetic acid, does not release the factor, but subsequent exposure of the membranes to auxin results in its release. Factor activity could not be demonstrated in fractions devoid of plasma membranes. The presence of a regulatory factor for RNA polymerase associated with plant plasma membrane and specifically released by auxin provides a mechanism whereby both rapid growth responses and delayed nuclear changes could be derived from a common auxin receptor site associated with plasma membrane. Images PMID:4508307

  7. Fc gamma-receptor activity of isolated human placental syncytiotrophoblast plasma membrane.

    PubMed Central

    Brown, P J; Johnson, P M

    1981-01-01

    Fc gamma-receptor activity of isolated human placental syncytiotrophoblast microvillous plasma membrane (StMPM) vesicle preparations has been determined in an immunoradiometric assay using Sepharose-immobilized protein A to separate free 125I-labelled human IgG from membrane-bound 125I-IgG. This receptor assay has been optimalized in terms of buffer pH and molarity, and used to demonstrate that prior 60 min washing of isolated membranes in 3 M KCl to remove extrinsic membrane-bound protein substantially increases the membrane-binding capacity for IgG. Inhibition studies have determined the syncytiotrophoblast Fc gamma-receptor equilibrium constant for association (Ka) as 4.0 x 10(7) M-1 at 37 degrees and the number of available Fc gamma-receptor sites as 1.5 x 10(14) per mg membrane protein. PMID:7461733

  8. Lgl1 activation of rab10 promotes axonal membrane trafficking underlying neuronal polarization.

    PubMed

    Wang, Tong; Liu, Yang; Xu, Xiao-Hui; Deng, Cai-Yun; Wu, Kong-Yan; Zhu, Ji; Fu, Xiu-Qing; He, Miao; Luo, Zhen-Ge

    2011-09-13

    Directed membrane trafficking is believed to be crucial for axon development during neuronal morphogenesis. However, the underlying mechanisms are poorly understood. Here, we report a role of Lgl1, the mammalian homolog of Drosophila tumor suppressor Lethal giant larvae, in controlling membrane trafficking underlying axonal growth. We find that Lgl1 is associated with plasmalemmal precursor vesicles and enriched in developing axons. Lgl1 upregulation promoted axonal growth, whereas downregulation attenuated it as well as directional membrane insertion. Interestingly, Lgl1 interacted with and activated Rab10, a small GTPase that mediates membrane protein trafficking, by releasing GDP dissociation inhibitor (GDI) from Rab10. Furthermore, Rab10 lies downstream of Lgl1 in axon development and directional membrane insertion. Finally, both Lgl1 and Rab10 are required for neocortical neuronal polarization in vivo. Thus, the Lgl1 regulation of Rab10 stimulates the trafficking of membrane precursor vesicles, whose fusion with the plasmalemma is crucial for axonal growth.

  9. Membrane lipids regulate ganglioside GM2 catabolism and GM2 activator protein activity.

    PubMed

    Anheuser, Susi; Breiden, Bernadette; Schwarzmann, Günter; Sandhoff, Konrad

    2015-09-01

    Ganglioside GM2 is the major lysosomal storage compound of Tay-Sachs disease. It also accumulates in Niemann-Pick disease types A and B with primary storage of SM and with cholesterol in type C. Reconstitution of GM2 catabolism with β-hexosaminidase A and GM2 activator protein (GM2AP) at uncharged liposomal surfaces carrying GM2 as substrate generated only a physiologically irrelevant catabolic rate, even at pH 4.2. However, incorporation of anionic phospholipids into the GM2 carrying liposomes stimulated GM2 hydrolysis more than 10-fold, while the incorporation of plasma membrane stabilizing lipids (SM and cholesterol) generated a strong inhibition of GM2 hydrolysis, even in the presence of anionic phospholipids. Mobilization of membrane lipids by GM2AP was also inhibited in the presence of cholesterol or SM, as revealed by surface plasmon resonance studies. These lipids also reduced the interliposomal transfer rate of 2-NBD-GM1 by GM2AP, as observed in assays using Förster resonance energy transfer. Our data raise major concerns about the usage of recombinant His-tagged GM2AP compared with untagged protein. The former binds more strongly to anionic GM2-carrying liposomal surfaces, increases GM2 hydrolysis, and accelerates intermembrane transfer of 2-NBD-GM1, but does not mobilize membrane lipids.

  10. Photodynamic activity of substituted zinc trisulfophthalocyanines: role of plasma membrane damage.

    PubMed

    Cauchon, Nicole; Nader, Moni; Bkaily, Ghassan; van Lier, Johan E; Hunting, Darel

    2006-01-01

    We recently reported that variations in cellular phototoxicity among a series of alkynyl-substituted zinc trisulfophthalocyanines (ZnPcS3Cn) correlates with their hydrophobicity, with the most amphiphilic derivatives showing the highest cell uptake and phototoxicity. In this study we address the role of the plasma membrane in the photodynamic response as it relates to the overall hydrophobicity of the photosensitizer. The membrane tracker dye 1-[4(trimethylamino)phenyl]-6-phenylhexa-1,3,5-triene (TMA-DPH), which is incorporated into plasma membranes by endocytosis, was used to establish plasma membrane uptake by EMT-6 cells of the ZnPcS3C, by colocalization, and TMA-DPH membrane uptake rates after photodynamic therapy were used to quantify membrane damage. TMA-DPH colocalization patterns show plasma membrane uptake of the photosensitizers after short 1 h incubation periods. TMA-DPH plasma membrane uptake rates after illumination of the photosensitizer-treated cells show a parabolic relationship with photosensitizer hydrophobicity that correlates well with the phototoxicity of the ZnPcS3C,. After a 1 h incubation period, overall phototoxicity correlates closely with the postillumination rate of TMA-DPH incorporation into the cell membrane, suggesting a major role of plasma membrane damage in the overall PDT effect. In contrast, after a 24 h incubation, phototoxicity shows a stronger but imperfect correlation with total cellular photosensitizer uptake rather than TMA-DPH membrane uptake, suggesting a partial shift in the cellular damage responsible for photosensitization from the plasma membrane to intracellular targets. We conclude that plasma membrane localization of the amphiphilic ZnPcS3C6-C9 is a major factor in their overall photodynamic activity.

  11. Modification of trout sperm membranes associated with activation and cryopreservation. Implications for fertilizing potential

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Abstract We investigated the effects of two trout sperm activation solutions on sperm physiology and membrane organization prior to and following cryopreservation using flow cytometry and investigated their impact on in vitro fertility. Cryopreservation caused greater phospholipid disorder (high pl...

  12. The Effects of Altered Membrane Cholesterol Levels on Sodium Pump Activity in Subclinical Hypothyroidism

    PubMed Central

    2017-01-01

    Background Metabolic dysfunctions characteristic of overt hypothyroidism (OH) start at the early stage of subclinical hypothyroidism (SCH). Na+/K+-ATPase (the sodium pump) is a transmembrane enzyme that plays a vital role in cellular activities in combination with membrane lipids. We evaluated the effects of early changes in thyroid hormone and membrane cholesterol on sodium pump activity in SCH and OH patients. Methods In 32 SCH patients, 35 OH patients, and 34 euthyroid patients, sodium pump activity and cholesterol levels in red blood cell membranes were measured. Serum thyroxine (T4) and thyroid stimulating hormone (TSH) levels were measured using enzyme-linked immunosorbent assays. Differences in their mean values were analysed using post hoc analysis of variance. We assessed the dependence of the sodium pump on other metabolites by multiple regression analysis. Results Sodium pump activity and membrane cholesterol were lower in both hypothyroid groups than in control group, OH group exhibiting lower values than SCH group. In SCH group, sodium pump activity showed a significant direct dependence on membrane cholesterol with an inverse relationship with serum TSH levels. In OH group, sodium pump activity depended directly on membrane cholesterol and serum T4 levels. No dependence on serum cholesterol was observed in either case. Conclusion Despite the presence of elevated serum cholesterol in hypothyroidism, membrane cholesterol contributed significantly to maintain sodium pump activity in the cells. A critical reduction in membrane cholesterol levels heralds compromised enzyme activity, even in the early stage of hypothyroidism, and this can be predicted by elevated TSH levels alone, without any evident clinical manifestations. PMID:28256112

  13. A membrane cytoskeleton from Dictyostelium discoideum. I. Identification and partial characterization of an actin-binding activity

    PubMed Central

    1981-01-01

    Dictyostelium discoideum plasma membranes isolated by each of three procedures bind F-actin. The interactions between these membranes and actin are examined by a novel application of falling ball viscometry. Treating the membranes as multivalent actin-binding particles analogous to divalent actin-gelation factors, we observe large increases in viscosity (actin cross-linking) when membranes of depleted actin and myosin are incubated with rabbit skeletal muscle F-actin. Pre- extraction of peripheral membrane proteins with chaotropes or the inclusion of Triton X-100 during the assay does not appreciably diminish this actin cross-linking activity. Lipid vesicles, heat- denatured membranes, proteolyzed membranes, or membranes containing endogenous actin show minimal actin cross-linking activity. Heat- denatured, but not proteolyzed, membranes regain activity when assayed in the presence of Triton X-100. Thus, integral membrane proteins appear to be responsible for some or all of the actin cross-linking activity of D. discoideum membranes. In the absence of MgATP, Triton X- 100 extraction of isolated D. discoideum membranes results in a Triton- insoluble residue composed of actin, myosin, and associated membrane proteins. The inclusion of MgATP before and during Triton extraction greatly diminishes the amount of protein in the Triton-insoluble residue without appreciably altering its composition. Our results suggest the existence of a protein complex stabilized by actin and/or myosin (membrane cytoskeleton) associated with the D. discoideum plasma membrane. PMID:6894148

  14. Effect of polymer chain length on membrane perturbation activity of cationic phenylene ethynylene oligomers and polymers.

    PubMed

    Wang, Ying; Jones, Emmalee M; Tang, Yanli; Ji, Eunkyung; Lopez, Gabriel P; Chi, Eva Y; Schanze, Kirk S; Whitten, David G

    2011-09-06

    The interactions of poly(phenylene ethynylene)- (PPE-) based cationic conjugated polyelectrolytes (CPEs) and oligo(phenylene ethynylene)s (OPEs) with different model lipid membrane systems were investigated to gain insight into the relationship between molecular structure and membrane perturbation ability. The CPE and OPE compounds exhibit broad-spectrum antimicrobial activity, and cell walls and membranes are believed to be their main targets. To better understand how the size, in terms of the number of repeat units, of the CPEs and OPEs affects their membrane disruption activities, a series of PPE-based CPEs and OPEs were synthesized and studied. A number of photophysical techniques were used to investigate the interactions of CPEs and OPEs with model membranes, including unilamellar vesicles and lipid monolayers at the air/water interface. CPE- or OPE-induced dye leakage from vesicles reveals that the CPEs and OPEs selectively perturb model bacterial membranes and that their membrane perturbation abilities are highly dependent on molecular size. Consistent with dye-leakage assay results, the CPEs and OPEs also exhibit chain-length-dependent ability to insert into 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DPPG) monolayers. Our results suggest that, for PPE-based CPE and OPE antimicrobials, chain length can be tuned to optimize their membrane perturbation ability.

  15. Finding Large Aperture Fractures in Geothermal Resource Areas Using a Three-Component Long-Offset Surface Seismic Survey, PSInSAR and Kinematic Structural Analysis

    SciTech Connect

    Teplow, William J.; Warren, Ian

    2015-08-12

    The DOE cost-share program applied innovative and cutting edge seismic surveying and processing, permanent scatter interferometry-synthetic aperture radar (PSInSAR) and structural kinematics to the exploration problem of locating and mapping largeaperture fractures (LAFs) for the purpose of targeting geothermal production wells. The San Emidio geothermal resource area, which is under lease to USG, contains production wells that have encountered and currently produce from LAFs in the southern half of the resource area (Figure 2). The USG lease block, incorporating the northern extension of the San Emidio geothermal resource, extends 3 miles north of the operating wellfield. The northern lease block was known to contain shallow thermal waters but was previously unexplored by deep drilling. Results of the Phase 1 exploration program are described in detail in the Phase 1 Final Report (Teplow et al., 2011). The DOE cost shared program was completed as planned on September 30, 2014. This report summarizes results from all of Phase 1 and 2 activities.

  16. Line active molecules promote inhomogeneous structures in membranes: theory, simulations and experiments.

    PubMed

    Palmieri, Benoit; Yamamoto, Tetsuya; Brewster, Robert C; Safran, Samuel A

    2014-06-01

    We review recent theoretical efforts that predict how line-active molecules can promote lateral heterogeneities (or domains) in model membranes. This fundamental understanding may be relevant to membrane composition in living cells, where it is thought that small domains, called lipid rafts, are necessary for the cells to be functional. The theoretical work reviewed here ranges in scale from coarse grained continuum models to nearly atomistic models. The effect of line active molecules on domain sizes and shapes in the phase separated regime or on fluctuation length scales and lifetimes in the single phase, mixed regime, of the membrane is discussed. Recent experimental studies on model membranes that include line active molecules are also presented together with some comparisons with the theoretical predictions.

  17. Separation of a toluene/ethanol mixture by pervaporation using active carbon-filled polymeric membranes

    SciTech Connect

    Duval, J.M. ); Folkers, B.; Mulder, M.H.V.; Smolders, C.A. ); Desgrandchamps, G. )

    1994-02-01

    In order to improve the separation properties of dense polymeric membranes toward a toluene/ethanol mixture, various active carbons and two types of zeolites were introduced into a thin polymeric film in order to form a heterogeneous membrane composed of solid particles surrounded by a polymer phase. Active carbons show a high adsorption selectivity for an aromatic compound over ethanol in the low concentration range of the aromatic component. Sorption and pervaporation experiments were carried out with a toluene/ethanol mixture, and they showed no improvement in selectivity and a decrease in flux for membranes filled with active carbons. For zeolite-filled membranes, both selectivity and flux decreased. A permeability model derived for heterogeneous systems was used. It confirmed that the carbon particles have a closed porous structure, allowing no transport from one side to the other, and that the zeolites have an ethanol selective permeation behavior. 21 refs., 7 figs., 6 tabs.

  18. Membrane-related effects underlying the biological activity of the anthraquinones emodin and barbaloin.

    PubMed

    Alves, Daiane S; Pérez-Fons, Laura; Estepa, Amparo; Micol, Vicente

    2004-08-01

    Commercial plant extracts containing anthraquinones are being increasingly used for cosmetics, food and pharmaceuticals due to their wide therapeutic and pharmacological properties. In this work, the interaction with model membranes of two representative 1,8-dihydroxyanthraquinones, barbaloin (Aloe) and emodin (Rheum, Polygonum), has been studied in order to explain their effects in biological membranes. Emodin showed a higher affinity for phospholipid membranes than barbaloin did, and was more effective in weakening hydrophobic interactions between hydrocarbon chains in phospholipid bilayers. Whereas emodin induced the formation of hexagonal-H(II) phase, barbaloin stabilized lamellar structures. Barbaloin promoted the formation of gel-fluid intermediate structures in phosphatidylglycerol membranes at physiological pH and ionic strength values. It is proposed that emodin's chromophore group is located at the upper half of the membrane, whereas barbaloin's one is in a deeper position but having its glucopyranosyl moiety near the phospholipid/water interface. Moreover, membrane disruption by emodin or barbaloin showed specificity for the two major phospholipids present in bacterial membranes, phosphatidylethanolamine and phosphatidylglycerol. In order to relate their strong effects on membranes to their biological activity, the capacity of these compounds to inhibit the infectivity of the viral haemorrhagic septicaemia rhabdovirus (VHSV), a negative RNA enveloped virus, or the growth of Escherichia coli was tested. Anthraquinone-loaded liposomes showed a strong antimicrobial activity whereas these compounds in their free form did not. Both anthraquinones showed antiviral activity but only emodin was a virucidal agent. In conclusion, a molecular mechanism based on the effect of these compounds on the structure of biological membranes is proposed to account for their multiple biological activities. Anthraquinone-loaded liposomes may suppose an alternative for

  19. Ral mediates activity-dependent growth of postsynaptic membranes via recruitment of the exocyst

    PubMed Central

    Teodoro, Rita O; Pekkurnaz, Gulçin; Nasser, Abdullah; Higashi-Kovtun, Misao E; Balakireva, Maria; McLachlan, Ian G; Camonis, Jacques; Schwarz, Thomas L

    2013-01-01

    Remodelling neuronal connections by synaptic activity requires membrane trafficking. We present evidence for a signalling pathway by which synaptic activity and its consequent Ca2+ influx activate the small GTPase Ral and thereby recruit exocyst proteins to postsynaptic zones. In accord with the ability of the exocyst to direct delivery of post-Golgi vesicles, constitutively active Ral expressed in Drosophila muscle causes the exocyst to be concentrated in the region surrounding synaptic boutons and consequently enlarges the membrane folds of the postsynaptic plasma membrane (the subsynaptic reticulum, SSR). SSR growth requires Ral and the exocyst component Sec5 and Ral-induced enlargement of these membrane folds does not occur in sec5−/− muscles. Chronic changes in synaptic activity influence the plastic growth of this membrane in a manner consistent with activity-dependent activation of Ral. Thus, Ral regulation of the exocyst represents a control point for postsynaptic plasticity. This pathway may also function in mammals as expression of activated RalA in hippocampal neurons increases dendritic spine density in an exocyst-dependent manner and increases Sec5 in spines. PMID:23812009

  20. The bile acid-sensitive ion channel (BASIC) is activated by alterations of its membrane environment.

    PubMed

    Schmidt, Axel; Lenzig, Pia; Oslender-Bujotzek, Adrienne; Kusch, Jana; Lucas, Susana Dias; Gründer, Stefan; Wiemuth, Dominik

    2014-01-01

    The bile acid-sensitive ion channel (BASIC) is a member of the DEG/ENaC family of ion channels. Channels of this family are characterized by a common structure, their physiological functions and modes of activation, however, are diverse. Rat BASIC is expressed in brain, liver and intestinal tract and activated by bile acids. The physiological function of BASIC and its mechanism of bile acid activation remain a puzzle. Here we addressed the question whether amphiphilic bile acids activate BASIC by directly binding to the channel or indirectly by altering the properties of the surrounding membrane. We show that membrane-active substances other than bile acids also affect the activity of BASIC and that activation by bile acids and other membrane-active substances is non-additive, suggesting that BASIC is sensitive for changes in its membrane environment. Furthermore based on results from chimeras between BASIC and ASIC1a, we show that the extracellular and the transmembrane domains are important for membrane sensitivity.

  1. Propagating cell-membrane waves driven by curved activators of actin polymerization.

    PubMed

    Peleg, Barak; Disanza, Andrea; Scita, Giorgio; Gov, Nir

    2011-04-21

    Cells exhibit propagating membrane waves which involve the actin cytoskeleton. One type of such membranal waves are Circular Dorsal Ruffles (CDR) which are related to endocytosis and receptor internalization. Experimentally, CDRs have been associated with membrane bound activators of actin polymerization of concave shape. We present experimental evidence for the localization of convex membrane proteins in these structures, and their insensitivity to inhibition of myosin II contractility in immortalized mouse embryo fibroblasts cell cultures. These observations lead us to propose a theoretical model which explains the formation of these waves due to the interplay between complexes that contain activators of actin polymerization and membrane-bound curved proteins of both types of curvature (concave and convex). Our model predicts that the activity of both types of curved proteins is essential for sustaining propagating waves, which are abolished when one type of curved activator is removed. Within this model waves are initiated when the level of actin polymerization induced by the curved activators is higher than some threshold value, which allows the cell to control CDR formation. We demonstrate that the model can explain many features of CDRs, and give several testable predictions. This work demonstrates the importance of curved membrane proteins in organizing the actin cytoskeleton and cell shape.

  2. Sodium pump molecular activity and membrane lipid composition in two disparate ectotherms, and comparison with endotherms.

    PubMed

    Turner, Nigel; Hulbert, A J; Else, Paul L

    2005-02-01

    Previous research has shown that the lower sodium pump molecular activity observed in tissues of ectotherms compared to endotherms, is largely related to the lower levels of polyunsaturates and higher levels of monounsaturates found in the cell membranes of ectotherms. Marine-based ectotherms, however, have very polyunsaturated membranes, and in the current study, we measured molecular activity and membrane lipid composition in tissues of two disparate ectothermic species, the octopus (Octopus vulgaris) and the bearded dragon lizard (Pogona vitticeps), to determine whether the high level of membrane polyunsaturation generally observed in marine-based ectotherms is associated with an increased sodium pump molecular activity relative to other ectotherms. Phospholipids from all tissues of the octopus were highly polyunsaturated and contained high concentrations of the omega-3 polyunsaturate, docosahexaenoic acid (22:6 (n-3)). In contrast, phospholipids from bearded dragon tissues contained higher proportions of monounsaturates and lower proportions of polyunsaturates. Sodium pump molecular activity was only moderately elevated in tissues of the octopus compared to the bearded dragon, despite the much greater level of polyunsaturation in octopus membranes. When the current data were combined with data for the ectothermic cane toad, a significant (P = 0.003) correlation was observed between sodium pump molecular activity and the content of 22:6 (n-3) in the surrounding membrane. These results are discussed in relation to recent work which shows a similar relationship in endotherms.

  3. Investigation of the pore structure and morphology of cellulose acetate membranes using small-angle neutron scattering. 1: Cellulose acetate active layer membranes

    SciTech Connect

    Kulkarni, S.; Krause, S. ); Wignall, G.D. . Solid State Div.); Hammouda, B. . Center for High Resolution Neutron Scattering)

    1994-11-07

    The structure of ultrathin cellulose acetate membranes, known as active layer membranes, has been investigated using small-angle neutron scattering. These membranes are known to have structural and functional similarity to the surface or skin layer in commercial reverse-osmosis (RO) membranes and hence are useful model systems for understanding the structure of the RO membrane skin layer. Active layer membranes were studied after swelling them with either D[sub 2]O or CD[sub 3]OD. The results in both cases clearly indicated the presence of very small (10--20 [angstrom]) porous structures in the membrane. The presence of such pores has been a subject of long-standing controversy in this area. The data were analyzed using a modified Debye-Bueche analysis and the resultant membrane structure was seen to agree well with structural information from electron microscopic studies. Finally, a possible explanation for the differences in scattering observed between the D[sub 2]O swollen membranes and the CD[sub 3]OD swollen membranes has been presented.

  4. The effect of aspartame metabolites on human erythrocyte membrane acetylcholinesterase activity.

    PubMed

    Tsakiris, Stylianos; Giannoulia-Karantana, Aglaia; Simintzi, Irene; Schulpis, Kleopatra H

    2006-01-01

    Studies have implicated aspartame (ASP) with neurological problems. The aim of this study was to evaluate acetylcholinesterase (AChE) activity in human erythrocyte membranes after incubation with the sum of ASP metabolites, phenylalanine (Phe), methanol (met) and aspartic acid (aspt), or with each one separately. Erythrocyte membranes were obtained from 12 healthy individuals and were incubated with ASP hydrolysis products for 1 h at 37 degrees C. AChE was measured spectrophotometrically. Incubation of membranes with ASP metabolites corresponding with 34 mg/kg, 150 mg/kg or 200 mg/kg of ASP consumption resulted in an enzyme activity reduction by -33%, -41%, and -57%, respectively. Met concentrations 0.14 mM, 0.60 mM, and 0.80 mM decreased the enzyme activity by -20%, -32% or -40%, respectively. Aspt concentrations 2.80 mM, 7.60 mM or 10.0 mM inhibited membrane AChE activity by -20%, -35%, and -47%, respectively. Phe concentrations 0.14 mM, 0.35 mM or 0.50mM reduced the enzyme activity by -11%, -33%, and -35%, respectively. Aspt or Phe concentrations 0.82 mM or 0.07 mM, respectively, did not alter the membrane AChE activity. It is concluded that low concentrations of ASP metabolites had no effect on the membrane enzyme activity, whereas high or toxic concentrations partially or remarkably decreased the membrane AChE activity, respectively. Additionally, neurological symptoms, including learning and memory processes, may be related to the high or toxic concentrations of the sweetener metabolites.

  5. The higher level of complexity of K-Ras4B activation at the membrane

    PubMed Central

    Jang, Hyunbum; Banerjee, Avik; Chavan, Tanmay S.; Lu, Shaoyong; Zhang, Jian; Gaponenko, Vadim; Nussinov, Ruth

    2016-01-01

    Is nucleotide exchange sufficient to activate K-Ras4B? To signal, oncogenic rat sarcoma (Ras) anchors in the membrane and recruits effectors by exposing its effector lobe. With the use of NMR and molecular dynamics (MD) simulations, we observed that in solution, farnesylated guanosine 5′-diphosphate (GDP)-bound K-Ras4B is predominantly autoinhibited by its hypervariable region (HVR), whereas the GTP-bound state favors an activated, HVR-released state. On the anionic membrane, the catalytic domain adopts multiple orientations, including parallel (∼180°) and perpendicular (∼90°) alignments of the allosteric helices, with respect to the membrane surface direction. In the autoinhibited state, the HVR is sandwiched between the effector lobe and the membrane; in the active state, with membrane-anchored farnesyl and unrestrained HVR, the catalytic domain fluctuates reinlessly, exposing its effector-binding site. Dimerization and clustering can reduce the fluctuations. This achieves preorganized, productive conformations. Notably, we also observe HVR-autoinhibited K-Ras4B-GTP states, with GDP-bound-like orientations of the helices. Thus, we propose that the GDP/GTP exchange may not be sufficient for activation; instead, our results suggest that the GDP/GTP exchange, HVR sequestration, farnesyl insertion, and orientation/localization of the catalytic domain at the membrane conjointly determine the active or inactive state of K-Ras4B. Importantly, K-Ras4B-GTP can exist in active and inactive states; on its own, GTP binding may not compel K-Ras4B activation.—Jang, H., Banerjee, A., Chavan, T. S, Lu, S., Zhang, J., Gaponenko, V., Nussinov, R. The higher level of complexity of K-Ras4B activation at the membrane. PMID:26718888

  6. Membrane permeability and the loss of germination factor from Neurospora crassa at low water activities

    NASA Technical Reports Server (NTRS)

    Charlang, G.; Horowitz, N. H.

    1974-01-01

    Neurospora crassa conidia incubating in buffer at low water activities release a germination-essential component as well as 260-nm absorbing and ninhydrin-positive materials, regardless of whether an electrolyte or nonelectrolyte is used to reduce water activity. Chloroform and antibiotics known to increase cell-membrane permeability have a similar effect. This suggests that membrane damage occurs in media of low water activity and that an increase in permeability is responsible for the release of cellular components. The damage caused in media of low water activity is nonlethal in most cases, and the conidia recover when transferred to nutrient medium.

  7. Membrane Active Antimicrobial Peptides: Translating Mechanistic Insights to Design

    PubMed Central

    Li, Jianguo; Koh, Jun-Jie; Liu, Shouping; Lakshminarayanan, Rajamani; Verma, Chandra S.; Beuerman, Roger W.

    2017-01-01

    Antimicrobial peptides (AMPs) are promising next generation antibiotics that hold great potential for combating bacterial resistance. AMPs can be both bacteriostatic and bactericidal, induce rapid killing and display a lower propensity to develop resistance than do conventional antibiotics. Despite significant progress in the past 30 years, no peptide antibiotic has reached the clinic yet. Poor understanding of the action mechanisms and lack of rational design principles have been the two major obstacles that have slowed progress. Technological developments are now enabling multidisciplinary approaches including molecular dynamics simulations combined with biophysics and microbiology toward providing valuable insights into the interactions of AMPs with membranes at atomic level. This has led to increasingly robust models of the mechanisms of action of AMPs and has begun to contribute meaningfully toward the discovery of new AMPs. This review discusses the detailed action mechanisms that have been put forward, with detailed atomistic insights into how the AMPs interact with bacterial membranes. The review further discusses how this knowledge is exploited toward developing design principles for novel AMPs. Finally, the current status, associated challenges, and future directions for the development of AMP therapeutics are discussed. PMID:28261050

  8. Membrane Active Antimicrobial Peptides: Translating Mechanistic Insights to Design.

    PubMed

    Li, Jianguo; Koh, Jun-Jie; Liu, Shouping; Lakshminarayanan, Rajamani; Verma, Chandra S; Beuerman, Roger W

    2017-01-01

    Antimicrobial peptides (AMPs) are promising next generation antibiotics that hold great potential for combating bacterial resistance. AMPs can be both bacteriostatic and bactericidal, induce rapid killing and display a lower propensity to develop resistance than do conventional antibiotics. Despite significant progress in the past 30 years, no peptide antibiotic has reached the clinic yet. Poor understanding of the action mechanisms and lack of rational design principles have been the two major obstacles that have slowed progress. Technological developments are now enabling multidisciplinary approaches including molecular dynamics simulations combined with biophysics and microbiology toward providing valuable insights into the interactions of AMPs with membranes at atomic level. This has led to increasingly robust models of the mechanisms of action of AMPs and has begun to contribute meaningfully toward the discovery of new AMPs. This review discusses the detailed action mechanisms that have been put forward, with detailed atomistic insights into how the AMPs interact with bacterial membranes. The review further discusses how this knowledge is exploited toward developing design principles for novel AMPs. Finally, the current status, associated challenges, and future directions for the development of AMP therapeutics are discussed.

  9. Powder Activated Carbon Pretreatment of a Microfiltration Membrane for the Treatment of Surface Water.

    PubMed

    Song, Yali; Dong, Bingzhi; Gao, Naiyun; Ma, Xiaoyan

    2015-09-10

    This study focused on the effect of powder activated carbon (PAC) adsorption on microfiltration (MF) membrane performance. The results showed that PAC pretreatment offered high organic matter removal rates for both dissolved organic carbon (DOC) and ultraviolet absorbance at 254 nm (UV254) during 10-200 mg/L PAC dosage. The removal efficiencies of organic matter by MF membrane filtration decreased with the increase of organic matter removal rate by PAC adsorption. PAC mainly removed organic matter of about 3 kDa molecular weight (MW). MF membrane maintained more than 5 kDa MW organic matter on the membrane after PAC adsorption. The results of membrane filtration indicated that PAC pretreatment slightly promoted membrane flux, regardless of PAC dosage. It seems that the organic matter fouling membrane was concentrated in more than 3 kDa MW. PAC removed markedly less than 3 kDa MW organic matter and had less effect on more than 3 kDa organic matter. Thus, PAC cannot reduce membrane fouling.

  10. ESR study on the antioxidant activity of TAK-218 in biological model membranes.

    PubMed

    Murakami, M; Fukatsu, K; Ohkawa, S; Kasahara, F; Sugawara, T

    2000-06-01

    TAK-218 has a 2,3-dihydrobenzofuran-5-amine (coumaran) structure which resembles alpha-tocopherol, and is a promising candidate as an agent for central nervous system (CNS) trauma and ischemia. The radical scavenging activity of TAK-218 was studied using electron spin resonance (ESR) spectroscopy. TAK-218 exhibited a more potent scavenging activity towards the hydroxyl radical than did the well-known hydroxyl radical scavengers, mannitol and dimethylsulfoxide. Towards the superoxide radical, TAK-218 showed equal potency to glutathione. TAK-218 reacted rapidly with stable radicals, such as galvinoxyl and 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH), and gave the quinone as a two-electron oxidized product in analogy with alpha-tocopherol. To exhibit an excellent antioxidative activity in living systems, the compounds should not only have the intrinsic radical scavenging activity but also good distribution in the biological lipid-bilayer membrane. To examine the antioxidant activity of TAK-218, the inhibition of lipid peroxidation by alpha-tocopherol and TAK-218 in liposomal membranes was studied using an ESR spin-label technique. Both alpha-tocopherol and TAK-218 completely inhibited lipid peroxidation by radicals generated in an aqueous layer using a water-soluble radical initiator, 2,2'-azobis-(2-amidinopropane) hydrochloride (AAPH). At a high incubation temperature (45 degrees C), alpha-tocopherol scavenged radicals more effectively than TAK-218 on the surface of the membrane, while TAK-218 scavenged radicals more effectively in the interior of the membrane. The difference between TAK-218 and alpha-tocopherol for radical scavenging in the membrane system derives from the different distribution pattern of these compounds. TAK-218 can penetrate the membrane freely and can scavenge the radical in the membrane interior. Furthermore, TAK-218 was shown to inhibit lipid peroxidation initiated by a lipid soluble radical initiator, 2,2'-azobis-(2,4-dimethylvaleronitrile

  11. Regulation of membrane associated protein kinase C activity by guanine nucleotide in rabbit peritoneal neutrophils

    SciTech Connect

    Huang, C.K.; Devanney, J.F.

    1986-03-05

    Addition of phorbol myristate acetate (PMA) (0.1 ..mu..g/ml) or guanosine-5'-0-(3-thiotriphosphate) (GTP..gamma..S) (10..mu..M) to the membrane fraction from rabbit peritoneal neutrophils results in an increase of phosphorylation of several membrane proteins. To test whether membrane associated protein kinase C is involved in the activation, histone is added to the membrane as a substrate for protein kinase C. Phosphorylation of histone is determined by counting the gel pieces containing histone IIIS after separation from other membrane components by SDS-gel electrophoresis. In the presence of CaC12 (20 ..mu..M), GTP..gamma..S (10 ..mu..M) or PMA (0.1 ..mu..g/ml) stimulates the phosphorylation of histone IIIS (40% to 70% increase). To achieve this effect calcium is required for GTP..gamma..S but not for PMA. The effect of GTP..gamma..S but not PMA is inhibited in membranes obtained from cells pretreated with pertussis toxin. Membrane protein kinase C is solubilized with Triton X-100 (1%) and then applied to a DEAE-52 cellulose column chromatography. Two peaks of protein kinase C activity are observed. Peak one is eluted at 40 mM NaCl, peak two is eluted at 140 mM NaCl. The activity of peak one is stimulated with phosphatidylserine (PS) and PMA but not with PS and calcium. The activity of peak two is stimulated with either PS and PMA or PS and calcium. The results suggest that GTP binding protein is involved in the activation of membrane associated protein kinase C and the kinase may exist in two forms, calcium sensitive and calcium insensitive.

  12. Controlled Proteolysis Activates the Plasma Membrane Ca2+ Pump of Higher Plants (A Comparison with the Effect of Calmodulin in Plasma Membrane from Radish Seedlings).

    PubMed Central

    Rasi-Caldogno, F.; Carnelli, A.; De Michelis, M. I.

    1993-01-01

    The effects of calmodulin and of controlled trypsin treatments on the activity of the Ca2+ pump were investigated in plasma membrane purified from radish (Raphanus sativus L.) seedlings. Treatment of the plasma membrane with ethylenediaminetetra-acetate (EDTA), which removed about two-thirds of the plasma membrane-associated calmodulin, markedly increased the stimulation of the Ca2+ pump by calmodulin. In EDTA-treated plasma membrane, stimulation by calmodulin of the Ca2+ pump activity was maximal at low free Ca2+ (2-5 [mu]M) and decreased with the increase of free Ca2+ concentration. The Ca2+ pump activity was stimulated also by a controlled treatment of the plasma membrane with trypsin: the effect of trypsin treatment depended on the concentration of both trypsin and plasma membrane proteins and on the duration of incubation. Stimulation of the Ca2+ pump activity by trypsin treatment of the plasma membrane was similar to that induced by calmodulin both in extent and in dependence on the free Ca2+ concentration in the assay medium. Moreover, the Ca2+ pump of trypsin-treated plasma membrane was insensitive to further stimulation by calmodulin, suggesting that limited proteolysis preferentially cleaves a regulatory domain of the enzyme that is involved in its activation by calmodulin. PMID:12231945

  13. Membrane-Targeting DCAP Analogues with Broad-Spectrum Antibiotic Activity against Pathogenic Bacteria.

    PubMed

    Hurley, Katherine A; Heinrich, Victoria A; Hershfield, Jeremy R; Demons, Samandra T; Weibel, Douglas B

    2015-04-09

    We performed a structure-activity relationship study of 2-((3-(3,6-dichloro-9H-carbazol-9-yl)-2-hydroxypropyl)amino)-2-(hydroxymethyl)propane-1,3-diol (DCAP), which is an antibacterial agent that disrupts the membrane potential and permeability of bacteria. The stereochemistry of DCAP had no effect on the biological activity of DCAP. The aromaticity and electronegativity of the chlorine-substituted carbazole was required for activity, suggesting that its planar and dipolar characteristics orient DCAP in membranes. Increasing the hydrophobicity of the tail region of DCAP enhanced its antibiotic activity. Two DCAP analogues displayed promising antibacterial activity against the BSL-3 pathogens Bacillus anthracis and Francisella tularensis. Codosing DCAP analogues with ampicillin or kanamycin increased their potency. These studies demonstrate that DCAP and its analogues may be a promising scaffold for developing chemotherapeutic agents that bind to bacterial membranes and kill strains of slow-growing or dormant bacteria that cause persistent infections.

  14. Activation of Endothelial Nitric Oxide (eNOS) Occurs through Different Membrane Domains in Endothelial Cells

    PubMed Central

    Tran, Jason; Magenau, Astrid; Rodriguez, Macarena; Rentero, Carles; Royo, Teresa; Enrich, Carlos; Thomas, Shane R.; Grewal, Thomas; Gaus, Katharina

    2016-01-01

    Endothelial cells respond to a large range of stimuli including circulating lipoproteins, growth factors and changes in haemodynamic mechanical forces to regulate the activity of endothelial nitric oxide synthase (eNOS) and maintain blood pressure. While many signalling pathways have been mapped, the identities of membrane domains through which these signals are transmitted are less well characterized. Here, we manipulated bovine aortic endothelial cells (BAEC) with cholesterol and the oxysterol 7-ketocholesterol (7KC). Using a range of microscopy techniques including confocal, 2-photon, super-resolution and electron microscopy, we found that sterol enrichment had differential effects on eNOS and caveolin-1 (Cav1) colocalisation, membrane order of the plasma membrane, caveolae numbers and Cav1 clustering. We found a correlation between cholesterol-induced condensation of the plasma membrane and enhanced high density lipoprotein (HDL)-induced eNOS activity and phosphorylation suggesting that cholesterol domains, but not individual caveolae, mediate HDL stimulation of eNOS. Vascular endothelial growth factor (VEGF)-induced and shear stress-induced eNOS activity was relatively independent of membrane order and may be predominantly controlled by the number of caveolae on the cell surface. Taken together, our data suggest that signals that activate and phosphorylate eNOS are transmitted through distinct membrane domains in endothelial cells. PMID:26977592

  15. Activation of Endothelial Nitric Oxide (eNOS) Occurs through Different Membrane Domains in Endothelial Cells.

    PubMed

    Tran, Jason; Magenau, Astrid; Rodriguez, Macarena; Rentero, Carles; Royo, Teresa; Enrich, Carlos; Thomas, Shane R; Grewal, Thomas; Gaus, Katharina

    2016-01-01

    Endothelial cells respond to a large range of stimuli including circulating lipoproteins, growth factors and changes in haemodynamic mechanical forces to regulate the activity of endothelial nitric oxide synthase (eNOS) and maintain blood pressure. While many signalling pathways have been mapped, the identities of membrane domains through which these signals are transmitted are less well characterized. Here, we manipulated bovine aortic endothelial cells (BAEC) with cholesterol and the oxysterol 7-ketocholesterol (7KC). Using a range of microscopy techniques including confocal, 2-photon, super-resolution and electron microscopy, we found that sterol enrichment had differential effects on eNOS and caveolin-1 (Cav1) colocalisation, membrane order of the plasma membrane, caveolae numbers and Cav1 clustering. We found a correlation between cholesterol-induced condensation of the plasma membrane and enhanced high density lipoprotein (HDL)-induced eNOS activity and phosphorylation suggesting that cholesterol domains, but not individual caveolae, mediate HDL stimulation of eNOS. Vascular endothelial growth factor (VEGF)-induced and shear stress-induced eNOS activity was relatively independent of membrane order and may be predominantly controlled by the number of caveolae on the cell surface. Taken together, our data suggest that signals that activate and phosphorylate eNOS are transmitted through distinct membrane domains in endothelial cells.

  16. Structural basis for activation, assembly and membrane binding of ESCRT-III Snf7 filaments.

    PubMed

    Tang, Shaogeng; Henne, W Mike; Borbat, Peter P; Buchkovich, Nicholas J; Freed, Jack H; Mao, Yuxin; Fromme, J Christopher; Emr, Scott D

    2015-12-15

    The endosomal sorting complexes required for transport (ESCRTs) constitute hetero-oligomeric machines that catalyze multiple topologically similar membrane-remodeling processes. Although ESCRT-III subunits polymerize into spirals, how individual ESCRT-III subunits are activated and assembled together into a membrane-deforming filament remains unknown. Here, we determine X-ray crystal structures of the most abundant ESCRT-III subunit Snf7 in its active conformation. Using pulsed dipolar electron spin resonance spectroscopy (PDS), we show that Snf7 activation requires a prominent conformational rearrangement to expose protein-membrane and protein-protein interfaces. This promotes the assembly of Snf7 arrays with ~30 Å periodicity into a membrane-sculpting filament. Using a combination of biochemical and genetic approaches, both in vitro and in vivo, we demonstrate that mutations on these protein interfaces halt Snf7 assembly and block ESCRT function. The architecture of the activated and membrane-bound Snf7 polymer provides crucial insights into the spatially unique ESCRT-III-mediated membrane remodeling.

  17. Membrane-active Antimicrobial Peptides as Template Structures for Novel Antibiotic Agents.

    PubMed

    Lohner, Karl

    2017-01-01

    The increase of pathogens being resistant to antibiotics represents a global health problem and therefore it is a pressing need to develop antibiotics with novel mechanisms of action. Host defense peptides, which have direct antimicrobial activity (also termed antimicrobial peptides) or immune modulating activity, are valuable template structures for the development of such compounds. Antimicrobial peptides exhibit remarkably different structures as well as biological activity profiles with multiple targets. A large fraction of these peptides interfere physically with the cell membrane of bacteria (focus of this review), but can also translocate into the cytosol, where they interact with nucleic acids, ribosomes and proteins. Several potential interaction sites have to be considered on the route of the peptides from the environment to the cytoplasmic membrane. Translocation of peptides through the cell wall may not be impaired by the thick but relatively porous peptidoglycan layer. However, interaction with lipopolysaccharides of the outer membrane of Gram-negative bacteria and (lipo)teichoic acids of Gram-positive bacteria may reduce the effective concentration at the cytoplasmic membrane, where supposedly the killing event takes place. On a molecular level several mechanisms are discussed, which are important for the rational design of improved antimicrobial compounds: toroidal pore formation, carpet model (coverage of membrane surface by peptides), interfacial activity, void formation, clustering of lipids and effects of membrane curvature. In summary, many of these models just represent special cases that can be interrelated to each other and depend on both the nature of lipids and peptides.

  18. Structural basis for activation, assembly and membrane binding of ESCRT-III Snf7 filaments

    PubMed Central

    Tang, Shaogeng; Henne, W Mike; Borbat, Peter P; Buchkovich, Nicholas J; Freed, Jack H; Mao, Yuxin; Fromme, J Christopher; Emr, Scott D

    2015-01-01

    The endosomal sorting complexes required for transport (ESCRTs) constitute hetero-oligomeric machines that catalyze multiple topologically similar membrane-remodeling processes. Although ESCRT-III subunits polymerize into spirals, how individual ESCRT-III subunits are activated and assembled together into a membrane-deforming filament remains unknown. Here, we determine X-ray crystal structures of the most abundant ESCRT-III subunit Snf7 in its active conformation. Using pulsed dipolar electron spin resonance spectroscopy (PDS), we show that Snf7 activation requires a prominent conformational rearrangement to expose protein-membrane and protein-protein interfaces. This promotes the assembly of Snf7 arrays with ~30 Å periodicity into a membrane-sculpting filament. Using a combination of biochemical and genetic approaches, both in vitro and in vivo, we demonstrate that mutations on these protein interfaces halt Snf7 assembly and block ESCRT function. The architecture of the activated and membrane-bound Snf7 polymer provides crucial insights into the spatially unique ESCRT-III-mediated membrane remodeling. DOI: http://dx.doi.org/10.7554/eLife.12548.001 PMID:26670543

  19. Enhancing the performance of nanofiltration membranes by modifying the active layer with aramide dendrimers.

    PubMed

    de Jubera, Ana M Saenz; Gao, Yuan; Moore, Jeffrey S; Cahill, David G; Mariñas, Benito J

    2012-09-04

    The fully aromatic polyamide active layer of a commercial nanofiltration membrane was modified with three generations (G1, G2, and G3) of aramide dendrimers, all with oligoethylene glycol chains on their peripheries. Permeation experiments revealed that the rejection of Rhodamine WT, used as a surrogate for organic contaminants, improved 1-2 orders of magnitude for membranes modified with G2 and G3 dendrimers at loadings of 0.7-3.5 μg/cm(2) (dendrimer layer thicknesses of ~1-6 nm) compared to the performance of unmodified membranes. In contrast, the corresponding water permeability of dendrimer-modified membranes decreased by only ~30%. Although an enhancement in the rejection of H(3)AsO(3), NaCl, and BaCl(2) was also observed for dendritic membranes, the effect was less pronounced than that for rhodamine WT. Characterization of membranes modified with 3.5 μg/cm(2) dendrimers G2 and G3 by Rutherford backscattering spectrometry with the aid of heavy ion probes (Ag(+) and Ba(2+)) revealed that accessibility of the larger Ba(2+) probe to carboxylate groups on the active layer decreased for the membranes modified with dendrimers.

  20. Membrane anchoring of diacylglycerol lactones substituted with rigid hydrophobic acyl domains correlates with biological activities.

    PubMed

    Raifman, Or; Kolusheva, Sofiya; Comin, Maria J; Kedei, Noemi; Lewin, Nancy E; Blumberg, Peter M; Marquez, Victor E; Jelinek, Raz

    2010-01-01

    Synthetic diacylglycerol lactones (DAG lactones) are effective modulators of critical cellular signaling pathways downstream of the lipophilic second messenger diacylglycerol that activate a host of protein kinase C (PKC) isozymes as well as other non-kinase proteins that share with PKC similar C1 membrane-targeting domains. A fundamental determinant of the biological activity of these amphiphilic molecules is the nature of their interactions with cellular membranes. This study characterizes the membrane interactions and bilayer anchoring of a series of DAG lactones in which the hydrophobic moiety is a 'molecular rod', namely a rigid 4-[2-(R-phenyl)ethynyl]benzoate moiety in the acyl position. Use of assays employing chromatic biomimetic vesicles and biophysical techniques revealed that the mode of membrane anchoring of the DAG lactone derivatives was markedly affected by the presence of the hydrophobic diphenyl rod and by the size of the functional unit at the terminus of the rod. Two primary mechanisms of interaction were observed: surface binding of the DAG lactones at the lipid/water interface and deep insertion of the ligands into the alkyl core of the lipid bilayer. These membrane-insertion properties could explain the different patterns of the PKC translocation from the cytosol to membranes that is induced by the molecular-rod DAG lactones. This investigation emphasizes that the side residues of DAG lactones, rather than simply conferring hydrophobicity, profoundly influence membrane interactions, and thus may further contribute to the diversity of biological actions of these synthetic biomimetic ligands.

  1. Progression of NMR studies of membrane-active peptides from lipid bilayers to live cells

    NASA Astrophysics Data System (ADS)

    Sani, M.-A.; Separovic, F.

    2015-04-01

    Understanding the structure of membrane-active peptides faces many challenges associated with the development of appropriate model membrane systems as the peptide structure depends strongly on the lipid environment. This perspective provides a brief overview of the approach taken to study antimicrobial and amyloid peptides in phospholipid bilayers using oriented bilayers and magic angle spinning techniques. In particular, Boltzmann statistics REDOR and maximum entropy analysis of spinning side bands are used to analyse systems where multiple states of peptide or lipid molecules may co-exist. We propose that in future, rather than model membranes, structural studies in whole cells are feasible.

  2. Non-selective voltage-activated cation channel in the human red blood cell membrane.

    PubMed

    Kaestner, L; Bollensdorff, C; Bernhardt, I

    1999-02-04

    Using the patch-clamp technique, a non-selective voltage-activated Na+ and K+ channel in the human red blood cell membrane was found. The channel operates only at positive membrane potentials from about +30 mV (inside positive) onwards. For sodium and potassium ions, similar conductances of about 21 pS were determined. Together with the recently described K+(Na+)/H+ exchanger, this channel is responsible for the increase of residual K+ and Na+ fluxes across the human red blood cell membrane when the cells are suspended in low ionic strength medium.

  3. Controlled release and antibacterial activity of tetracycline hydrochloride-loaded bacterial cellulose composite membranes.

    PubMed

    Shao, Wei; Liu, Hui; Wang, Shuxia; Wu, Jimin; Huang, Min; Min, Huihua; Liu, Xiufeng

    2016-07-10

    Bacterial cellulose (BC) is widely used in biomedical applications. In this study, we prepared an antibiotic drug tetracycline hydrochloride (TCH)-loaded bacterial cellulose (BC) composite membranes, and evaluated the drug release, antibacterial activity and biocompatibility. The structure and morphology of the fabricated BC-TCH composite membranes were characterized using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The TCH release results show that the incorporation of BC matrix to load TCH is able to control the release. In vitro antibacterial assay demonstrate that the developed BC-TCH composites displayed excellent antibacterial activity solely associated with the loaded TCH drug. More importantly, the BC-TCH composite membranes display good biocompatibility. These characteristics of BC-TCH composite membranes indicate that they may successfully serve as wound dressings and other medical biomaterials.

  4. Large aperture compound lenses made of lithium

    NASA Astrophysics Data System (ADS)

    Cremer, J. T.; Piestrup, M. A.; Beguiristain, H. R.; Gary, C. K.; Pantell, R. H.

    2003-04-01

    We have measured the intensity profile and transmission of x rays focused by a series of biconcave parabolic unit lenses fabricated in lithium. For specified focal length and photon energy lithium compound refractive lenses (CRL) have a larger transmission, aperture size, and gain compared to aluminum, kapton, and beryllium CRLs. The lithium compound refractive lens was composed of 335 biconcave, parabolic unit lenses each with an on-axis radius of curvature of 0.95 mm. Two-dimensional focusing was obtained at 8.0 keV with a focal length of 95 cm. The effective aperture of the CRL was measured to be 1030 μm with on-axis (peak) transmissions of 27% and an on-axis intensity gain of 18.9.

  5. Large Aperture Multiplexed Diffractive Lidar Optics

    NASA Technical Reports Server (NTRS)

    Rallison, Richard D.; Schwemmer, Geary K. (Technical Monitor)

    1999-01-01

    We have delivered only 2 or 3 UV Holographic Optical Elements (HOEs) thus far and have fallen short of the intended goal in size and in dual wavelength function. Looking back, it has been fortuitous that we even made anything work in the UV region. It was our good fortune to discover that the material we work with daily was adequate for use at 355 nm, if well rinsed during processing. If we had stuck to our original plan of etching in small pieces of fused silica, we would still be trying to make the first small section in our ion mill, which is not yet operational. The original plan was far too ambitious and would take another 2 years to complete beginning where we left off this time. In order to make a HOE for the IR as well as the UV we will likely have to learn to sensitize some film to the 1064 line and we have obtained sensitizer that is reported to work in that region already. That work would also take an additional year to complete.

  6. Large Aperture Systems: 2000-2004

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This custom bibliography from the NASA Scientific and Technical Information Program lists a sampling of records found in the NASA Aeronautics and Space Database. The scope of this topic includes technologies for next generation astronomical telescopes and detectors. This area of focus is one of the enabling technologies as defined by NASA s Report of the President s Commission on Implementation of United States Space Exploration Policy, published in June 2004.

  7. Large aperture ac interferometer for optical testing.

    PubMed

    Moore, D T; Murray, R; Neves, F B

    1978-12-15

    A 20-cm clear aperture modified Twyman-Green interferometer is described. The system measures phase with an AC technique called phase-lock interferometry while scanning the aperture with a dual galvanometer scanning system. Position information and phase are stored in a minicomputer with disk storage. This information is manipulated with associated software, and the wavefront deformation due to a test component is graphically displayed in perspective and contour on a CRT terminal.

  8. Millimeter Wave Applications of Large Aperture Systems

    DTIC Science & Technology

    1980-02-01

    unit step impulse ................. 89 5-8 Truss/tower model. Joints identification numbers ............... 91 5-9 z-displacement (m) histories for the...tip joint 801 displacements for 1 cycle steady-state response to harmonic excitation (15 N at 10 Hz) ................ 101 6-1 Elliptic torus 30 x 60 m...freedom (DOF) -o a reasonable level, the large platform was modelled with axial members whereby only three DOF’s are present nat each joint . Although

  9. Luminol electrochemiluminescence for the analysis of active cholesterol at the plasma membrane in single mammalian cells.

    PubMed

    Ma, Guangzhong; Zhou, Junyu; Tian, Chunxiu; Jiang, Dechen; Fang, Danjun; Chen, Hongyuan

    2013-04-16

    A luminol electrochemiluminescence assay was reported to analyze active cholesterol at the plasma membrane in single mammalian cells. The cellular membrane cholesterol was activated by the exposure of the cells to low ionic strength buffer or the inhibition of intracellular acyl-coA/cholesterol acyltransferase (ACAT). The active membrane cholesterol was reacted with cholesterol oxidase in the solution to generate a peak concentration of hydrogen peroxide on the electrode surface, which induced a measurable luminol electrochemiluminescence. Further treatment of the active cells with mevastatin decreased the active membrane cholesterol resulting in a drop in luminance. No change in the intracellular calcium was observed in the presence of luminol and voltage, which indicated that our analysis process might not interrupt the intracellular cholesterol trafficking. Single cell analysis was performed by placing a pinhole below the electrode so that only one cell was exposed to the photomultiplier tube (PMT). Twelve single cells were analyzed individually, and a large deviation on luminance ratio observed exhibited the cell heterogeneity on the active membrane cholesterol. The smaller deviation on ACAT/HMGCoA inhibited cells than ACAT inhibited cells suggested different inhibition efficiency for sandoz 58035 and mevastatin. The new information obtained from single cell analysis might provide a new insight on the study of intracellular cholesterol trafficking.

  10. Trichoplaxin - a new membrane-active antimicrobial peptide from placozoan cDNA.

    PubMed

    Simunić, Juraj; Petrov, Dražen; Bouceba, Tahar; Kamech, Nédia; Benincasa, Monica; Juretić, Davor

    2014-05-01

    A method based on the use of signal peptide sequences from antimicrobial peptide (AMP) precursors was used to mine a placozoa expressed sequence tag database and identified a potential antimicrobial peptide from Trichoplax adhaerens. This peptide, with predicted sequence FFGRLKSVWSAVKHGWKAAKSR is the first AMP from a placozoan species, and was named trichoplaxin. It was chemically synthesized and its structural properties, biological activities and membrane selectivity were investigated. It adopts an α-helical structure in contact with membrane-like environments and is active against both Gram-negative and Gram-positive bacterial species (including MRSA), as well as yeasts from the Candida genus. The cytotoxic activity, as assessed by the haemolytic activity against rat erythrocytes, U937 cell permeabilization to propidium iodide and MCF7 cell mitochondrial activity, is significantly lower than the antimicrobial activity. In tests with membrane models, trichoplaxin shows high affinity for anionic prokaryote-like membranes with good fit in kinetic studies. Conversely, there is a low affinity for neutral eukaryote-like membranes and absence of a dose dependent response. With high selectivity for bacterial cells and no homologous sequence in the UniProt, trichoplaxin is a new potential lead compound for development of broad-spectrum antibacterial drugs.

  11. Biologically Inspired Photocatalytically Active Membranes for Water Treatment

    NASA Astrophysics Data System (ADS)

    Kinsinger, Nichola M.

    There is an alarming increase of a variety of new chemicals that are now being discharged into the wastewater system causing increased concern for public health and safety because many are not removed by typical wastewater treatment practices. Titanium Dioxide (TiO2) is a heterogeneous photocatalytic material that rapidly and completely mineralizing organics without harmful byproducts. TiO2 is synthesized by various methods, which lack the necessary control of crystal size, phase, and morphological features that yield optimized semiconductor materials. Mineralizing organisms demonstrate how nature can produce elegant structures at room temperature through controlled organic-mineral interactions. Here, we utilize biologically-inspired scaffolds to template the nucleation and growth of inorganic materials such as TiO2, which aid in controlling the size and phase of these particles and ultimately, their properties. Nanosized rutile and anatase particles were synthesized under solution conditions at relatively low temperatures and mild pH conditions. The effects of reaction conditions on phase and grain size were investigated and discussed from coordination chemistry and coarsening mechanisms. Photocatalytic characterization of TiO2 phase mixtures was performed to investigate their synergistic effect. The suspension conditions of these catalytic nanomaterials were modulated to optimize the degradation rate of organic analytes. Through the addition of an organic scaffold during the synthesis reaction, a mechanically robust (elastic) composite material containing TiO2 nanoparticles was produced. This composite was subsequently heat-treated to produce a porous, high surface area TiO2 nanoparticulate membrane. Processing conditions were investigated to characterize the growth and phase transformation of TiO2, which ultimately impacts photocatalytic performance. These bulk porous TiO2 structures can be fabricated and tailored to act as stand-alone photocatalytic membranes

  12. Specificity and mechanism of action of alpha-helical membrane-active peptides interacting with model and biological membranes by single-molecule force spectroscopy.

    PubMed

    Sun, Shiyu; Zhao, Guangxu; Huang, Yibing; Cai, Mingjun; Shan, Yuping; Wang, Hongda; Chen, Yuxin

    2016-07-01

    In this study, to systematically investigate the targeting specificity of membrane-active peptides on different types of cell membranes, we evaluated the effects of peptides on different large unilamellar vesicles mimicking prokaryotic, normal eukaryotic, and cancer cell membranes by single-molecule force spectroscopy and spectrum technology. We revealed that cationic membrane-active peptides can exclusively target negatively charged prokaryotic and cancer cell model membranes rather than normal eukaryotic cell model membranes. Using Acholeplasma laidlawii, 3T3-L1, and HeLa cells to represent prokaryotic cells, normal eukaryotic cells, and cancer cells in atomic force microscopy experiments, respectively, we further studied that the single-molecule targeting interaction between peptides and biological membranes. Antimicrobial and anticancer activities of peptides exhibited strong correlations with the interaction probability determined by single-molecule force spectroscopy, which illustrates strong correlations of peptide biological activities and peptide hydrophobicity and charge. Peptide specificity significantly depends on the lipid compositions of different cell membranes, which validates the de novo design of peptide therapeutics against bacteria and cancers.

  13. Specificity and mechanism of action of alpha-helical membrane-active peptides interacting with model and biological membranes by single-molecule force spectroscopy

    PubMed Central

    Sun, Shiyu; Zhao, Guangxu; Huang, Yibing; Cai, Mingjun; Shan, Yuping; Wang, Hongda; Chen, Yuxin

    2016-01-01

    In this study, to systematically investigate the targeting specificity of membrane-active peptides on different types of cell membranes, we evaluated the effects of peptides on different large unilamellar vesicles mimicking prokaryotic, normal eukaryotic, and cancer cell membranes by single-molecule force spectroscopy and spectrum technology. We revealed that cationic membrane-active peptides can exclusively target negatively charged prokaryotic and cancer cell model membranes rather than normal eukaryotic cell model membranes. Using Acholeplasma laidlawii, 3T3-L1, and HeLa cells to represent prokaryotic cells, normal eukaryotic cells, and cancer cells in atomic force microscopy experiments, respectively, we further studied that the single-molecule targeting interaction between peptides and biological membranes. Antimicrobial and anticancer activities of peptides exhibited strong correlations with the interaction probability determined by single-molecule force spectroscopy, which illustrates strong correlations of peptide biological activities and peptide hydrophobicity and charge. Peptide specificity significantly depends on the lipid compositions of different cell membranes, which validates the de novo design of peptide therapeutics against bacteria and cancers. PMID:27363513

  14. Improved antibacterial activity of nanofiltration polysulfone membranes modified with silver nanoparticles.

    PubMed

    Andrade, Patricia Fernanda; de Faria, Andreia Fonseca; Oliveira, Silvana Ruella; Arruda, Marco Aurélio Zezzi; Gonçalves, Maria do Carmo

    2015-09-15

    Polysulfone membranes (PSf) containing silver nanoparticles were prepared by the wet phase-inversion process. Silver nanoparticles (AgNP) were dispersed into the polymer matrix using two different methodologies. In the first one, the AgNP were synthesized and further dispersed into the polymer solution (ex situ process). In the second method, the formation of the AgNP was performed in situ. The AgNP crystalline structure in the PSf membranes was confirmed by X-ray diffraction. Field emission scanning electron microscopy images showed that the addition of AgNP in PSf membranes caused no significant changes to the finger-like morphology. When the ex situ methodology was applied, 45 nm average size AgNP were uniformly distributed in the internal pores of the membranes. However, when the AgNP were formed through the in situ process, the AgNP were uniformly and preferentially distributed on the top and bottom surfaces of the membrane. In the last case, the AgNP showed cubic morphology when present in the bottom and top surfaces, however, when inside the membrane their morphology was spherical. The cubic-like nanoparticles displayed a 38 nm average edge length. The silver ion released from the membrane during water filtration was measured using inductively coupled plasma mass spectrometry, which showed a silver leaching of approximately 2 μg L(-1). The nanocomposite membranes prepared by the in situ method exhibited a better antibacterial activity, in comparison to those prepared by ex situ, and also a decrease in 90% Escherichia coli adhered cells compared to the pristine PSf membranes. In conclusion, the in situ procedure can be considered a feasible, simple, and reproducible methodology to prepare anti-biofouling polysulfone membranes containing AgNP.

  15. One-dimensional potential of mean force underestimates activation barrier for transport across flexible lipid membranes

    NASA Astrophysics Data System (ADS)

    Kopelevich, Dmitry I.

    2013-10-01

    Transport of a fullerene-like nanoparticle across a lipid bilayer is investigated by coarse-grained molecular dynamics (MD) simulations. Potentials of mean force (PMF) acting on the nanoparticle in a flexible bilayer suspended in water and a bilayer restrained to a flat surface are computed by constrained MD simulations. The rate of the nanoparticle transport into the bilayer interior is predicted using one-dimensional Langevin models based on these PMFs. The predictions are compared with the transport rates obtained from a series of direct (unconstrained) MD simulations of the solute transport into the flexible bilayer. It is observed that the PMF acting on the solute in the flexible membrane underestimates the transport rate by more than an order of magnitude while the PMF acting on the solute in the restrained membrane yields an accurate estimate of the activation energy for transport into the flexible membrane. This paradox is explained by a coexistence of metastable membrane configurations for a range of the solute positions inside and near the flexible membrane. This leads to a significant reduction of the contribution of the transition state to the mean force acting on the solute. Restraining the membrane shape ensures that there is only one stable membrane configuration corresponding to each solute position and thus the transition state is adequately represented in the PMF. This mechanism is quite general and thus this phenomenon is expected to occur in a wide range of interfacial systems. A simple model for the free energy landscape of the coupled solute-membrane system is proposed and validated. This model explicitly accounts for effects of the membrane deformations on the solute transport and yields an accurate prediction of the activation energy for the solute transport.

  16. One-dimensional potential of mean force underestimates activation barrier for transport across flexible lipid membranes.

    PubMed

    Kopelevich, Dmitry I

    2013-10-07

    Transport of a fullerene-like nanoparticle across a lipid bilayer is investigated by coarse-grained molecular dynamics (MD) simulations. Potentials of mean force (PMF) acting on the nanoparticle in a flexible bilayer suspended in water and a bilayer restrained to a flat surface are computed by constrained MD simulations. The rate of the nanoparticle transport into the bilayer interior is predicted using one-dimensional Langevin models based on these PMFs. The predictions are compared with the transport rates obtained from a series of direct (unconstrained) MD simulations of the solute transport into the flexible bilayer. It is observed that the PMF acting on the solute in the flexible membrane underestimates the transport rate by more than an order of magnitude while the PMF acting on the solute in the restrained membrane yields an accurate estimate of the activation energy for transport into the flexible membrane. This paradox is explained by a coexistence of metastable membrane configurations for a range of the solute positions inside and near the flexible membrane. This leads to a significant reduction of the contribution of the transition state to the mean force acting on the solute. Restraining the membrane shape ensures that there is only one stable membrane configuration corresponding to each solute position and thus the transition state is adequately represented in the PMF. This mechanism is quite general and thus this phenomenon is expected to occur in a wide range of interfacial systems. A simple model for the free energy landscape of the coupled solute-membrane system is proposed and validated. This model explicitly accounts for effects of the membrane deformations on the solute transport and yields an accurate prediction of the activation energy for the solute transport.

  17. Tuning Liposome Membrane Permeability by Competitive Peptide Dimerization and Partitioning-Folding Interactions Regulated by Proteolytic Activity

    NASA Astrophysics Data System (ADS)

    Lim, Seng Koon; Sandén, Camilla; Selegård, Robert; Liedberg, Bo; Aili, Daniel

    2016-02-01

    Membrane active peptides are of large interest for development of drug delivery vehicles and therapeutics for treatment of multiple drug resistant infections. Lack of specificity can be detrimental and finding routes to tune specificity and activity of membrane active peptides is vital for improving their therapeutic efficacy and minimize harmful side effects. We describe a de novo designed membrane active peptide that partition into lipid membranes only when specifically and covalently anchored to the membrane, resulting in pore-formation. Dimerization with a complementary peptide efficiently inhibits formation of pores. The effect can be regulated by proteolytic digestion of the inhibitory peptide by the matrix metalloproteinase MMP-7, an enzyme upregulated in many malignant tumors. This system thus provides a precise and specific route for tuning the permeability of lipid membranes and a novel strategy for development of recognition based membrane active peptides and indirect enzymatically controlled release of liposomal cargo.

  18. Single-Molecule Imaging Reveals the Activation Dynamics of Intracellular Protein Smad3 on Cell Membrane

    NASA Astrophysics Data System (ADS)

    Li, Nan; Yang, Yong; He, Kangmin; Zhang, Fayun; Zhao, Libo; Zhou, Wei; Yuan, Jinghe; Liang, Wei; Fang, Xiaohong

    2016-09-01

    Smad3 is an intracellular protein that plays a key role in propagating transforming growth factor β (TGF-β) signals from cell membrane to nucleus. However whether the transient process of Smad3 activation occurs on cell membrane and how it is regulated remains elusive. Using advanced live-cell single-molecule fluorescence microscopy to image and track fluorescent protein-labeled Smad3, we observed and quantified, for the first time, the dynamics of individual Smad3 molecules docking to and activation on the cell membrane. It was found that Smad3 docked to cell membrane in both unstimulated and stimulated cells, but with different diffusion rates and dissociation kinetics. The change in its membrane docking dynamics can be used to study the activation of Smad3. Our results reveal that Smad3 binds with type I TGF-β receptor (TRI) even in unstimulated cells. Its activation is regulated by TRI phosphorylation but independent of receptor endocytosis. This study offers new information on TGF-β/Smad signaling, as well as a new approach to investigate the activation of intracellular signaling proteins for a better understanding of their functions in signal transduction.

  19. Membrane-active metabolites produced by soil actinomycetes using chromatic phospholipid/polydiacetylene vesicles.

    PubMed

    Mehravar, Maryam; Sardari, Soroush; Owlia, Parviz

    2011-12-01

    Increased resistance of pathogens toward existing antibiotics has compelled the research efforts to introduce new antimicrobial substances. Drugs with new and less resistant-prone targets to antimicrobial activity have a high priority for drug development activities. Cell membrane seems to be a potential target for new antibiotic agent development to overcome resistance. In this study, A total number of 67 actinomycetes were isolated from the soil samples collected from desert, farming and mineral parts of Iran. We used a chromatic sensor as a membrane model that was set up for the target of antimicrobial metabolites of actinomycetes isolated from the soil. The sensors particles were composed of phospholipid and polymerized polydiacetylene (PDA) lipids. These polymers exhibited color change following interaction with membrane-active metabolites. The color change was due to structural disorder in the lipids following their interaction with membrane-active metabolites. The resultant color change was recorded by fluorescent microscope and easily recognizable by naked eye as well. Sixteen strains were isolated which produced antimicrobial metabolites and were effective against test microorganisms (Escherichia coli, Candida albicans and Saccharomyces cerevisiae ). A total number of 3 out of 16 strains produced membrane-active metabolites. These 3 strains were identified using 16s rRNA as Streptomyces sp and submitted to GenBank (accession no. JN180853; JN180854; JN180855).

  20. Single-Molecule Imaging Reveals the Activation Dynamics of Intracellular Protein Smad3 on Cell Membrane

    PubMed Central

    Li, Nan; Yang, Yong; He, Kangmin; Zhang, Fayun; Zhao, Libo; Zhou, Wei; Yuan, Jinghe; Liang, Wei; Fang, Xiaohong

    2016-01-01

    Smad3 is an intracellular protein that plays a key role in propagating transforming growth factor β (TGF-β) signals from cell membrane to nucleus. However whether the transient process of Smad3 activation occurs on cell membrane and how it is regulated remains elusive. Using advanced live-cell single-molecule fluorescence microscopy to image and track fluorescent protein-labeled Smad3, we observed and quantified, for the first time, the dynamics of individual Smad3 molecules docking to and activation on the cell membrane. It was found that Smad3 docked to cell membrane in both unstimulated and stimulated cells, but with different diffusion rates and dissociation kinetics. The change in its membrane docking dynamics can be used to study the activation of Smad3. Our results reveal that Smad3 binds with type I TGF-β receptor (TRI) even in unstimulated cells. Its activation is regulated by TRI phosphorylation but independent of receptor endocytosis. This study offers new information on TGF-β/Smad signaling, as well as a new approach to investigate the activation of intracellular signaling proteins for a better understanding of their functions in signal transduction. PMID:27641076

  1. Electrochemiluminescence imaging for parallel single-cell analysis of active membrane cholesterol.

    PubMed

    Zhou, Junyu; Ma, Guangzhong; Chen, Yun; Fang, Danjun; Jiang, Dechen; Chen, Hong-Yuan

    2015-08-18

    Luminol electrochemiluminescence (ECL) imaging was developed for the parallel measurement of active membrane cholesterol at single living cells, thus establishing a novel electrochemical detection technique for single cells with high analysis throughput and low detection limit. In our strategy, the luminescence generated from luminol and hydrogen peroxide upon the potential was recorded in one image so that hydrogen peroxide at the surface of multiple cells could be simultaneously analyzed. Compared with the classic microelectrode array for the parallel single-cell analysis, the plat electrode only was needed in our ECL imaging, avoiding the complexity of electrode fabrication. The optimized ECL imaging system showed that hydrogen peroxide as low as 10 μM was visible and the efflux of hydrogen peroxide from cells could be determined. Coupled with the reaction between active membrane cholesterol and cholesterol oxidase to generate hydrogen peroxide, active membrane cholesterol at cells on the electrode was analyzed at single-cell level. The luminescence intensity was correlated with the amount of active membrane cholesterol, validating our system for single-cell cholesterol analysis. The relative high standard deviation on the luminescence suggested high cellular heterogeneities on hydrogen peroxide efflux and active membrane cholesterol, which exhibited the significance of single-cell analysis. This success in ECL imaging for single-cell analysis opens a new field in the parallel measurement of surface molecules at single cells.

  2. Sphingomyelinase D activity in model membranes: structural effects of in situ generation of ceramide-1-phosphate.

    PubMed

    Stock, Roberto P; Brewer, Jonathan; Wagner, Kerstin; Ramos-Cerrillo, Blanca; Duelund, Lars; Jernshøj, Kit Drescher; Olsen, Lars Folke; Bagatolli, Luis A

    2012-01-01

    The toxicity of Loxosceles spider venom has been attributed to a rare enzyme, sphingomyelinase D, which transforms sphingomyelin to ceramide-1-phosphate. The bases of its inflammatory and dermonecrotic activity, however, remain unclear. In this work the effects of ceramide-1-phosphate on model membranes were studied both by in situ generation of this lipid using a recombinant sphingomyelinase D from the spider Loxosceles laeta and by pre-mixing it with sphingomyelin and cholesterol. The systems of choice were large unilamellar vesicles for bulk studies (enzyme kinetics, fluorescence spectroscopy and dynamic light scattering) and giant unilamellar vesicles for fluorescence microscopy examination using a variety of fluorescent probes. The influence of membrane lateral structure on the kinetics of enzyme activity and the consequences of enzyme activity on the structure of target membranes containing sphingomyelin were examined. The findings indicate that: 1) ceramide-1-phosphate (particularly lauroyl ceramide-1-phosphate) can be incorporated into sphingomyelin bilayers in a concentration-dependent manner and generates coexistence of liquid disordered/solid ordered domains, 2) the activity of sphingomyelinase D is clearly influenced by the supramolecular organization of its substrate in membranes and, 3) in situ ceramide-1-phosphate generation by enzymatic activity profoundly alters the lateral structure and morphology of the target membranes.

  3. Intracellular Na+ and K+ activities and membrane conductances in the collecting tubule of Amphiuma

    PubMed Central

    1988-01-01

    Membrane potentials and conductances, and intracellular ionic activities were studied in isolated perfused collecting tubules of K+- adapted Amphiuma. Intracellular Na+ (aNai) and K+ (aKi) activities were measured, using liquid ion-exchanger double-barreled microelectrodes. Apical and basolateral membrane conductances were estimated by cable analysis. The effects of inhibition of the apical conductance by amiloride (10(-5) M) and of inhibition of the basolateral Na-K pump by either a low K+ (0.1 mM) bath or by ouabain (10(-4) M) were studied. Under control conditions, aNai was 8.4 +/- 1.9 mM and aKi 56 +/- 3 mM. With luminal amiloride, aNai decreased to 2.2 +/- 0.4 mM and aKi increased to 66 +/- 3 mM. Ouabain produced an increase of aNai to 44 +/- 4 mM, and a decrease of aKi to 22 +/- 6, and similar changes were observed when the tubule was exposed to a low K+ bath solution. During pump inhibition, there was a progressive decrease of the K+-selective basolateral membrane conductance and of the Na+ permeability of the apical membrane. A similar inhibition of both membrane conductances was observed after pump inhibition by low K+ solution. Upon reintroduction of K+, a basolateral membrane hyperpolarization of -23 +/- 4 mV was observed, indicating an immediate reactivation of the electrogenic Na-K pump. However, the recovery of the membrane conductances occurred over a slower time course. These data imply that both membrane conductances are regulated according to the intracellular ionic composition, but that the basolateral K+ conductance is not directly linked to the pump activity. PMID:3235975

  4. Cognition Is Cool: Can Hemispheric Activation Be Assessed by Tympanic Membrane Thermometry?

    ERIC Educational Resources Information Center

    Cherbuin, Nicolas; Brinkman, Cobie

    2004-01-01

    Hemispheric activation during cognitive tasks using functional magnetic resonance imaging (fMRI) can be difficult to interpret, uncomfortable, and is not widely available. This study investigated whether tympanic membrane thermometry could be used as a broad measure of hemispheric activation. Infrared probes measured ear temperature continuously…

  5. Comparing graphene, carbon nanotubes, and superfine powdered activated carbon as adsorptive coating materials for microfiltration membranes.

    PubMed

    Ellerie, Jaclyn R; Apul, Onur G; Karanfil, Tanju; Ladner, David A

    2013-10-15

    Multi-walled carbon nanotubes (MWCNTs), nano-graphene platelets (NGPs), and superfine powdered activated carbon (S-PAC) were comparatively evaluated for their applicability as adsorptive coatings on microfiltration membranes. The objective was to determine which materials were capable of contaminant removal while causing minimal flux reduction. Methylene blue and atrazine were the model contaminants. When applied as membrane coatings, MWCNTs had minimal retention capabilities for the model contaminants, and S-PAC had the fastest removal. The membrane coating approach was also compared with a stirred vessel configuration, in which the adsorbent was added to a stirred flask preceding the membrane cell. Direct application of the adsorbent to the membrane constituted a greater initial reduction in permeate concentrations of the model contaminants than with the stirred flask setup. All adsorbents except S-PAC showed flux reductions less than 5% after application as thin-layer membrane coatings, and flux recovery after membrane backwashing was greater than 90% for all materials and masses tested.

  6. Protein kinase and phosphatase activities of thylakoid membranes

    SciTech Connect

    Michel, H.; Shaw, E.K.; Bennett, J.

    1987-01-01

    Dephosphorylation of the 25 and 27 kDa light-harvesting Chl a/b proteins (LHCII) of the thylakoid membranes is catalyzed by a phosphatase which differs from previously reported thylakoid-bound phosphatases in having an alkaline pH optimum (9.0) and a requirement for Mg/sup 2 +/ ions. Dephosphorylation of the 8.3 kDa psb H gene product requires a Mg/sup 2 +/ ion concentration more than 200 fold higher than that for dephosphorylation of LHC II. The 8.3 kDa and 27 kDa proteins appear to be phosphorylated by two distinct kinases, which differ in substrate specificity and sensitivity to inhibitors. The plastoquinone antagonist 2,5-dibromo-3-methyl-6-isopropyl-benzoquinone (DBMIB) inhibits phosphorylation of the 27 kDa LHC II much more readily than phosphorylation of the 8.3 kDa protein. A similar pattern of inhibition is seen for two synthetic oligopeptides (MRKSATTKKAVC and ATQTLESSSRC) which are analogs of the phosphorylation sites of the two proteins. Possible modes of action of DBMIB are discussed. 45 refs., 7 figs., 3 tabs.

  7. Nonbonded interactions in membrane active cyclic biopolymers. IV - Cation dependence

    NASA Technical Reports Server (NTRS)

    Radhakrishnan, R.; Srinivasan, S.; Prasad, C. V.; Brinda, S. R.; Macelroy, R. D.; Sundaram, K.

    1980-01-01

    Interactions of valinomycin and form of its analogs in several conformations with the central ions Li(+), Na(+), K(+), Rb(+) and Cs(+) are investigated as part of a study of the specific preference of valinomycin for potassium and the mechanisms of carrier-mediated ion transport across membranes. Ion binding energies and conformational potential energies are calculated taking into account polarization energy formulas and repulsive energy between the central ion and the ligand atoms for conformations representing various stages in ion capture and release for each of the two ring chiralities of valinomycin and its analogs. Results allow the prediction of the chirality and conformation most likely to be observed for a given analog, and may be used to synthesize analogs with a desired rigidity or flexibility. The binding energies with the alkali metal cations are found to decrease with increasing ion size, and to be smaller than the corresponding ion hydration energies. It is pointed out that the observed potassium preference may be explainable in terms of differences between binding and hydration energies. Binding energies are also noted to depend on ligand conformation.

  8. Phosphatidylserine lipids and membrane order precisely regulate the activity of Polybia-MP1 peptide.

    PubMed

    Alvares, Dayane S; Neto, João Ruggiero; Ambroggio, Ernesto E

    2017-03-05

    Polybia-MP1 (IDWKKLLDAAKQIL-NH2) is a lytic peptide from the Brazilian wasp venom with known anti-cancer properties. Previous evidence indicates that phosphatidylserine (PS) lipids are relevant for the lytic activity of MP1. In agreement with this requirement, phosphatidylserine lipids are translocated to the outer leaflet of cells, and are available for MP1 binding, depending on the presence of liquid-ordered domains. Here, we investigated the effect of PS on MP1 activity when this lipid is reconstituted in membranes of giant or large liposomes with different lipid-phase states. By monitoring the membrane and soluble luminal content of giant unilamellar vesicles (GUVs), using fluorescence confocal microscopy, we were able to determine that MP1 has a pore-forming activity at the membrane level. Liquid-ordered domains, which were phase-separated within the membrane of GUVs, influenced the pore-forming activity of MP1. Experiments evaluating the membrane-binding and lytic activity of MP1 on large unilamellar vesicles (LUVs), with the same lipid composition as GUVs, demonstrated that there was synergy between liquid-ordered domains and PS, which enhanced both activities. Based on our findings, we propose that the physicochemical properties of cancer cell membranes, which possess a much higher concentration of PS than normal cells, renders them susceptible to MP1 binding and lytic pore formation. These results can be correlated with MP1's potent and selective anti-cancer activity and pave the way for future research to develop cancer therapies that harness and exploit the properties of MP1.

  9. Pervaporation dehydration of ethanol by hyaluronic acid/sodium alginate two-active-layer composite membranes.

    PubMed

    Gao, Chengyun; Zhang, Minhua; Ding, Jianwu; Pan, Fusheng; Jiang, Zhongyi; Li, Yifan; Zhao, Jing

    2014-01-01

    The composite membranes with two-active-layer (a capping layer and an inner layer) were prepared by sequential spin-coatings of hyaluronic acid (HA) and sodium alginate (NaAlg) on the polyacrylonitrile (PAN) support layer. The SEM showed a mutilayer structure and a distinct interface between the HA layer and the NaAlg layer. The coating sequence of two-active-layer had an obvious influence on the pervaporation dehydration performance of membranes. When the operation temperature was 80 °C and water concentration in feed was 10 wt.%, the permeate fluxes of HA/Alg/PAN membrane and Alg/HA/PAN membrane were similar, whereas the separation factor were 1130 and 527, respectively. It was found that the capping layer with higher hydrophilicity and water retention capacity, and the inner layer with higher permselectivity could increase the separation performance of the composite membranes. Meanwhile, effects of operation temperature and water concentration in feed on pervaporation performance as well as membrane properties were studied.

  10. Antimicrobial peptides activate the Rcs regulon through the outer membrane lipoprotein RcsF.

    PubMed

    Farris, Carol; Sanowar, Sarah; Bader, Martin W; Pfuetzner, Richard; Miller, Samuel I

    2010-10-01

    Salmonella enterica species are exposed to envelope stresses due to their environmental and infectious lifestyles. Such stresses include amphipathic cationic antimicrobial peptides (CAMPs), and resistance to these peptides is an important property for microbial virulence for animals. Bacterial mechanisms used to sense and respond to CAMP-induced envelope stress include the RcsFCDB phosphorelay, which contributes to survival from polymyxin B exposure. The Rcs phosphorelay includes two inner membrane (IM) proteins, RcsC and RcsD; the response regulator RcsB; the accessory coregulator RcsA; and an outer membrane bound lipoprotein, RcsF. Transcriptional activation of the Rcs regulon occurred within minutes of exposure to CAMP and during the first detectable signs of CAMP-induced membrane disorder. Rcs transcriptional activation by CAMPs required RcsF and preservation of its two internal disulfide linkages. The rerouting of RcsF to the inner membrane or its synthesis as an unanchored periplasmic protein resulted in constitutive activation of the Rcs regulon and RcsCD-dependent phosphorylation. These findings suggest that RcsFCDB activation in response to CAMP-induced membrane disorder is a result of a change in structure or availability of RcsF to the IM signaling constituents of the Rcs phosphorelay.

  11. Instant membrane resealing in nlrp3 inflammmasome activation of endothelial cells.

    PubMed

    Chen, Yang; Yuan, Ming; Xia, Min; Wang, Lei; Zhang, Yang; Li, Pin-Lan

    2016-01-01

    The present study explored the molecular mechanisms by which instant cell membrane resealing (CMR) controls the activation of NOD-like receptor pyrin domain containing 3 (Nlrp3) inflammasomes. Using wavelength-switching fluorescent microscopy with PI and fura-2 as indicators, we monitored instant CMR simultaneously with (Ca(2+))i in mouse microvascular endothelial cell (MVECs). LCWE or saponin wad found to produce membrane injury, which was resealed in a Ca(2+)-dependent manner, but abolished by FasL, a membrane raft (MR) clustering stimulator. Even in the presence of Ca(2+), FasL prolonged the CMR time as shown by an earlier onset of PI influx (48±12 sec vs. 17±3 min. of control). These effects of FasL were substantially blocked by an MR disruptor, methyl-beta-cyclodextrin (MCD). The failure of CMR upon FasL activated Nlrp3 inflammasomes, which was blocked by MCD, a membrane resealing compound, VA64 or siRNA of an MR-facilitating enzyme, acid sphingomyelinase. This inflammasome activation was due to increased lysosomal permeability and cathepsin B release. It is concluded that an MR-associated CMR protects ECs from Nlrp3 inflammasome activation induced by membrane injury.

  12. Antifungal property of hibicuslide C and its membrane-active mechanism in Candida albicans.

    PubMed

    Hwang, Ji Hong; Jin, Qinglong; Woo, Eun-Rhan; Lee, Dong Gun

    2013-10-01

    In this study, the antifungal activity and mode of action(s) of hibicuslide C derived from Abutilon theophrasti were investigated. Antifungal susceptibility testing showed that hibicuslide C possessed potent activities toward various fungal strains and less hemolytic activity than amphotericin B. To understand the antifungal mechanism(s) of hibicuslide C in Candida albicans, flow cytometric analysis with propidium iodide was done. The results showed that hibicuslide C perturbed the plasma membrane of the C. albicans. The analysis of the transmembrane electrical potential with 3,3'-dipropylthiacarbocyanine iodide [DiSC3(5)] indicated that hibicuslide C induced membrane depolarization. Furthermore, model membrane studies were performed with calcein encapsulating large unilamellar vesicles (LUVs) and FITC-dextran (FD) loaded LUVs. These results demonstrated that the antifungal effects of hibicuslide C on the fungal plasma membrane were through the formation of pores with radii between 2.3 nm and 3.3 nm. Finally, in three dimensional flow cytometric contour plots, a reduced cell sizes by the pore-forming action of hibicuslide C were observed. Therefore, the present study suggests that hibicuslide C exerts its antifungal effect by membrane-active mechanism.

  13. A Two-Stage Model for Lipid Modulation of the Activity of Integral Membrane Proteins

    PubMed Central

    Dodes Traian, Martín M.; Cattoni, Diego I.; Levi, Valeria; González Flecha, F. Luis

    2012-01-01

    Lipid-protein interactions play an essential role in the regulation of biological function of integral membrane proteins; however, the underlying molecular mechanisms are not fully understood. Here we explore the modulation by phospholipids of the enzymatic activity of the plasma membrane calcium pump reconstituted in detergent-phospholipid mixed micelles of variable composition. The presence of increasing quantities of phospholipids in the micelles produced a cooperative increase in the ATPase activity of the enzyme. This activation effect was reversible and depended on the phospholipid/detergent ratio and not on the total lipid concentration. Enzyme activation was accompanied by a small structural change at the transmembrane domain reported by 1-aniline-8-naphtalenesulfonate fluorescence. In addition, the composition of the amphipilic environment sensed by the protein was evaluated by measuring the relative affinity of the assayed phospholipid for the transmembrane surface of the protein. The obtained results allow us to postulate a two-stage mechanistic model explaining the modulation of protein activity based on the exchange among non-structural amphiphiles at the hydrophobic transmembrane surface, and a lipid-induced conformational change. The model allowed to obtain a cooperativity coefficient reporting on the efficiency of the transduction step between lipid adsorption and catalytic site activation. This model can be easily applied to other phospholipid/detergent mixtures as well to other membrane proteins. The systematic quantitative evaluation of these systems could contribute to gain insight into the structure-activity relationships between proteins and lipids in biological membranes. PMID:22723977

  14. Embryonal cell surface recognition. Extraction of an active plasma membrane component.

    PubMed

    Merrell, R; Gottlieb, D I; Glaser, L

    1975-07-25

    Plasma membranes obtained from different neural regions of the chicken embryo have previously been shown to specifically bind to homotypic cells and prevent cell aggregation (Merrell, R., and Glaser, L. (1973) Proc. Natl. Acad. Sci. U. S. A. 70, 2794-2798). Proteins responsible for the specific inhibition of cell aggregation have been solubilized from the plasma membrane of neural retina and optic tectum by delipidation with acetone followed by extraction with lithium diiodosalicylate. The extracts show the same regional and temporal specificity as previously shown for plasma membrane recognition by the same cells (Gottlieb, D. I., Merrell, R., and Glaser, L. (1974) Proc. Natl. Acad. Sci. U. S. A. 71, 1800-1802). Two micrograms of the most purified protein fraction inhibits the aggregation of 2.5 times 10(-4) cells under standard assay conditions. This represents a 20-fold increase in specific activity compared to whole membranes.

  15. Importance of Membrane Structural Integrity for RPE65 Retinoid Isomerization Activity

    SciTech Connect

    Golczak, Marcin; Kiser, Philip D.; Lodowski, David T.; Maeda, Akiko; Palczewski, Krzysztof

    2010-04-05

    Regeneration of visual chromophore in the vertebrate visual cycle involves the retinal pigment epithelium-specific protein RPE65, the key enzyme catalyzing the cleavage and isomerization of all-trans-retinyl fatty acid esters to 11-cis-retinol. Although RPE65 has no predicted membrane spanning domains, this protein predominantly associates with microsomal fractions isolated from bovine retinal pigment epithelium (RPE). We have re-examined the nature of RPE65 interactions with native microsomal membranes by using extraction and phase separation experiments. We observe that hydrophobic interactions are the dominant forces that promote RPE65 association with these membranes. These results are consistent with the crystallographic model of RPE65, which features a large lipophilic surface that surrounds the entrance to the catalytic site of this enzyme and likely interacts with the hydrophobic core of the endoplasmic reticulum membrane. Moreover, we report a critical role for phospholipid membranes in preserving the retinoid isomerization activity and physical properties of RPE65. Isomerase activity measured in bovine RPE was highly sensitive to phospholipase A{sup 2} treatment, but the observed decline in 11-cis-retinol production did not directly reflect inhibition by products of lipid hydrolysis. Instead, a direct correlation between the kinetics of phospholipid hydrolysis and retinoid isomerization suggests that the lipid membrane structure is critical for RPE65 enzymatic activity. We also provide evidence that RPE65 operates in a multiprotein complex with retinol dehydrogenase 5 and retinal G protein-coupled receptor in RPE microsomes. Modifications in the phospholipid environment affecting interactions with these protein components may be responsible for the alterations in retinoid metabolism observed in phospholipid-depleted RPE microsomes. Thus, our results indicate that the enzymatic activity of native RPE65 strongly depends on its membrane binding and

  16. Effect of membrane filtration of antimalarial drug solutions on in vitro activity against Plasmodium falciparum*

    PubMed Central

    Baird, J. K.; Lambros, C.

    1984-01-01

    Antimalarial activities of chloroquine, mefloquine, amodiaquine, and quinine in vitro against Plasmodium falciparum were diminished as a consequence of membrane filtration. Filtered drug solutions gave ID50 values up to 25-fold greater than those of non-filtered (ethanol-sterilized) drug solutions. Loss of activity by filtration was overcome by increasing the drug concentration prior to filtration. Water solutions filtered through Millex-GS filter units consistently showed an absorbance maximum at 277 nm, accompanied by a lesser peak at 225 nm. Water filtrates from Nucleopore and Millex-GV filters showed no absorbance at 277 nm and only slight absorbance was evident for the Gelman filter unit. Activity losses were attributed to extractable contaminating moieties in the membrane filters and/or drug binding to the membrane filters. PMID:6380786

  17. Cell attachment and spreading activity of mixed laminin peptide-chitosan membranes.

    PubMed

    Otagiri, Dai; Yamada, Yuji; Hozumi, Kentaro; Katagiri, Fumihiko; Kikkawa, Yamato; Nomizu, Motoyoshi

    2013-11-01

    Laminins are a multifunctional molecule with numerous active sites that have been identified in short peptide sequences. Mixed peptide-conjugated chitosan membranes using laminin-derived active peptides have been previously demonstrated to be useful as a biomaterial for tissue engineering. In this study, two syndecan-binding peptides, AG73 (RKRLQVQLSIRT) and C16 (KAFDITYVRLKF), and three integrin-binding peptides, EF1zz (ATLQLQEGRLHFXFDLGKGR, X: Nle, binding to integrin α2β1), A99a (ALRGDN, binding to integrin αvβ3), and A2G10 (SYWYRIEASRTG, binding to integrin α6β1), were mixed in various combinations, conjugated to chitosan membranes, and evaluated for their cell attachment and spreading activities. The cell attachment and spreading activity of EF1zz, A99a, and A2G10 were enhanced by AG73. In contrast, C16 enhanced only the cell attachment and spreading activity of A99a and did not influence the activity of EF1zz and A2G10. As well as previous study, the AG73-chitosan membrane bound to only syndecan. On the other hand, the C16-chitosan membrane interacted with both syndecan and β1 integrin. These data suggest that interaction of different receptors can cause synergistic effects. Therefore, AG73 is widely applicable as a synergistic agent for mixed peptide-matrices using several types of integrin-binding peptides. Additionally, the A2G10/AG73-chitosan membrane may be useful to investigate detailed biological functions of α6β1 integrin, which is a major laminin-binding receptor. Using a combination of tissue-appropriate laminin-derived peptides, the mixed peptide-chitosan membranes may serve as functional biomaterials for tissue engineering.

  18. ATPase activity of erythrocyte membrane in patients with trisomy 21 (Down's syndrome).

    PubMed

    Xue, Q M; Shen, D G; Dong, W

    1984-11-01

    ATPase activity of crythroyte membranes was determined in 25 cases of Down's syndrome verified by cytological and psychological examinations. The age range of the patients was 8-25 years; 16 males and 9 females. Thirty health male volunteers were selected as the control group. There was a marked reduction of total ATPase, Na+, K+-ATPase, Mg++ATPase activities and rate of ouabain inhibition in the patients with Down's syndrome. The authors suggest that there might exist transport defects in the red cell membranes in such patients.

  19. Differential Effects of G- and F-Actin on the Plasma Membrane Calcium Pump Activity

    PubMed Central

    Vanagas, Laura; de La Fuente, María Candelaria; Dalghi, Marianela; Ferreira-Gomes, Mariela; Rossi, Rolando C.; Strehler, Emanuel E.; Rossi, Juan P. F. C.

    2014-01-01

    We have previously shown that plasma membrane calcium ATPase (PMCA) pump activity is affected by the membrane protein concentration (Vanagas et al., Biochim Biophys Acta 1768:1641–1644, 2007). Results show evidences for the involvement of the actin cytoskeleton. In this study, we explored the relationship between the polymerization state of actin and its effects on purified PMCA activity. Our results show that PMCA associates with the actin cytoskeleton and this interaction causes a modulation of the catalytic activity involving the phosphorylated intermediate of the pump. The state of actin polymerization determines whether it acts as an activator or an inhibitor of the pump: G-actin and/or short oligomers activate the pump, while F-actin inhibits it. The effects of actin on PMCA are the consequence of direct interaction as demonstrated by immunoblotting and cosedimentation experiments. Taken together, these findings suggest that interactions with actin play a dynamic role in the regulation of PMCA-mediated Ca2+ extrusion through the membrane. Our results provide further evidence of the activation–inhibition phenomenon as a property of many cytoskeleton-associated membrane proteins where the cytoskeleton is no longer restricted to a mechanical function but is dynamically involved in modulating the activity of integral proteins with which it interacts. PMID:23152090

  20. delta-Opioid receptors exhibit high efficiency when activating trimeric G proteins in membrane domains.

    PubMed

    Bourova, Lenka; Kostrnova, Alexandra; Hejnova, Lucie; Moravcova, Zuzana; Moon, Hyo-Eun; Novotny, Jiri; Milligan, Graeme; Svoboda, Petr

    2003-04-01

    Low-density membrane fragments (domains) were separated from the bulk of plasma membranes of human embryonic kidney (HEK)293 cells expressing a delta-opioid (DOP) receptor-Gi1alpha fusion protein by drastic homogenization and flotation on equilibrium sucrose density gradients. The functional activity of trimeric G proteins and capacity of the DOP receptor to stimulate both the fusion protein-linked Gi1alpha and endogenous pertussis-toxin sensitive G proteins was measured as d-Ala2, d-Leu5-enkephalin stimulated high-affinity GTPase or guanosine-5'-[gamma-35S]triphosphate ([35S]GTPgammaS) binding. The maximum d-Ala2-d-Leu5 enkephalin (DADLE)-stimulated GTPase was two times higher in low-density membrane fragments than in bulk of plasma membranes; 58 and 27 pmol/mg/min, respectively. The same difference was obtained for [35S]GTPgammaS binding. Contrarily, the low-density domains contained no more than half the DOP receptor binding sites (Bmax = 6.6 pmol/mg versus 13.6 pmol/mg). Thus, when corrected for expression levels of the receptor, low-density domains exhibited four times higher agonist-stimulated GTPase and [35S]GTPgammaS binding than the bulk plasma membranes. The regulator of G protein signaling RGS1, enhanced further the G protein functional activity but did not remove the difference between domain-bound and plasma membrane pools of G protein. The potency of the agonist in functional studies and the affinity of specific [3H]DADLE binding to the receptor were, however, the same in both types of membranes - EC50 = 4.5 +/- 0.1 x 10(-8) and 3.2 +/- 1.4 x 10(-8) m for GTPase; Kd = 1.2 +/- 0.1 and 1.3 +/- 0.1 nm for [3H]DADLE radioligand binding assay. Similar results were obtained when sodium bicarbonate was used for alkaline isolation of membrane domains. By contrast, detergent-insensitive membrane domains isolated following treatment of cells with Triton X100 exhibited no DADLE-stimulated GTPase or GTPgammaS binding. Functional coupling between the DOP receptor

  1. Membrane Heterogeneity in Akt Activation in Prostate Cancer

    DTIC Science & Technology

    2009-11-01

    construct from the top, Fig. 1), proved to be incompatible with Akt1 activity. The prenylation signal derived from K- Ras rendered Akt1 catalytically...with either cyclo- dextrin (CD) or water-soluble cholesterol ( Chol ) or with CD followed by cholesterol treatment (CD Chol ). Cells incubated in serum

  2. Membrane Heterogeneity in Akt Activation in Prostate Cancer

    DTIC Science & Technology

    2009-07-01

    variant (third construct from the top, Fig. 1), proved to be incompatible with Akt1 activity. The prenylation signal derived from K- Ras rendered Akt1...water-soluble cholesterol ( Chol ) or with CD followed by cholesterol treatment (CD Chol ). Cells incubated in serum-free medium served as controls

  3. Activation by divalent cations of a Ca2+-activated K+ channel from skeletal muscle membrane

    PubMed Central

    1988-01-01

    Several divalent cations were studied as agonists of a Ca2+-activated K+ channel obtained from rat muscle membranes and incorporated into planar lipid bilayers. The effect of these agonists on single-channel currents was tested in the absence and in the presence of Ca2+. Among the divalent cations that activate the channel, Ca2+ is the most effective, followed by Cd2+, Sr2+, Mn2+, Fe2+, and Co2+. Mg2+, Ni2+, Ba2+, Cu2+, Zn2+, Hg2+, and Sn2+ are ineffective. The voltage dependence of channel activation is the same for all the divalent cations. The time-averaged probability of the open state is a sigmoidal function of the divalent cation concentration. The sigmoidal curves are described by a dissociation constant K and a Hill coefficient N. The values of these parameters, measured at 80 mV are: N = 2.1, K = 4 X 10(- 7) mMN for Ca2+; N = 3.0, K = 0.02 mMN for Cd2+; N = 1.45, K = 0.63 mMN for Sr2+; N = 1.7, K = 0.94 mMN for Mn2+; N = 1.1, K = 3.0 mMN for Fe2+; and N = 1.1 K = 4.35 mMN for Co2+. In the presence of Ca2+, the divalent cations Cd2+, Co2+, Mn2+, Ni2+, and Mg2+ are able to increase the apparent affinity of the channel for Ca2+ and they increase the Hill coefficient in a concentration-dependent fashion. These divalent cations are only effective when added to the cytoplasmic side of the channel. We suggest that these divalent cations can bind to the channel, unmasking new Ca2+ sites. PMID:3171535

  4. Antibiofilm activity of Bacillus pumilus SW9 against initial biofouling on microfiltration membranes.

    PubMed

    Zhang, Ying; Yu, Xin; Gong, Song; Ye, Chengsong; Fan, Zihong; Lin, Huirong

    2014-02-01

    Membrane biofouling, resulting from biofilm formation on the membrane, has become the main obstacle hindering wider application of membrane technology. Initial biofouling proves to be crucial which involves early stages of microbial adhesion and biofilm formation. Biological control of microbial attachment seems to be a promising strategy due to its high efficiency and eco-friendliness. The present study investigated the effects of a bacterium Bacillus pumilus SW9 on controlling the initial fouling formed by four target bacterial strains which were pioneer species responsible for biofouling in membrane bioreactors, using microfiltration membranes as the abiotic surfaces. The results suggested that strain SW9 exhibited excellent antibiofilm activity by decreasing the attached biomass of target strains. The production of extracellular polysaccharides and proteins by four target strains was also reduced. A distinct improvement of permeate flux in dead-end filtration systems was achieved when introducing strain SW9 to microfiltration experiments. Scanning electron microscopy and confocal laser scanning microscopy were performed to further ascertain significant changes of the biofouling layers. A link between biofilm inhibition and initial biofouling mitigation was thus provided, suggesting an alternatively potential way to control membrane biofouling through bacterial interactions.

  5. Cell membrane stretch activates intermediate-conductance Ca2+-activated K+ channels in arterial smooth muscle cells.

    PubMed

    Hayabuchi, Yasunobu; Nakaya, Yutaka; Mawatari, Kazuaki; Inoue, Miki; Sakata, Miho; Kagami, Shoji

    2011-01-01

    The aim of this study is to determine the signal transduction of membrane stretch on intermediate-conductance Ca(2+)-activated K(+) (IKca) channels in rat aorta smooth muscle cells using the patch-clamp technique. To stretch the cell membrane, both suction to the rear end of patch pipette and hypotonic shock were used. In cell-attached and inside-out patch configurations, the open probability of IKca channels increased when 20- to 45-mmHg suction was applied. Hyposmotic swelling efficiently increased IKca channel current. When the Ca(2+)-free solution was superfused, the activation of IKca current by the hyposmotic swelling was reduced. Furthermore, gadolinium (Gd(3+)) attenuated the activation of IKca channels induced by hyposmotic swelling, whereas nicardipine did not. In the experiments with Ca(2+)-free bath solution, pretreatment with GF109203X, a protein kinase C (PKC) inhibitor, completely abolished the stretch-induced activation of IKca currents. The stretch-induced activation of IKca channels was strongly inhibited by cytochalasin D, indicating a role for the F-actin in modulation of IKca channels by changes in cell stretching. These data suggest that cell membrane stretch activates IKca channels. In addition, the activation is associated with extracellular Ca(2+) influx through stretch-activated nonselective cation channels, and is also modulated by the F-actin cytoskeleton and the activation of PKC.

  6. Influence of microcystin-LR on the activity of membrane enzymes in rat intestinal mucosa.

    PubMed

    Moreno, I M; Mate, A; Repetto, G; Vázquez, C M; Cameán, A M

    2003-12-01

    The objective of the present study was to evaluate the effects of microcystin-LR (MCLR) on the activity of membrane enzymes from intestinal mucosa. In addition, serum chemistry and peroxidative status of both serum and intestinal homogenate were evaluated after treatment with MCLR. Wistar rats were treated with intraperitoneal injection of either 100 microg pure MCLR/Kg body weight or saline solution. A significant increase in liver weight and altered serum enzyme activities were found in MCLR-treated rats, indicating damage to the liver in these rats, as previously suggested. A higher specific activity of sucrase (1.5-fold) was observed after the administration of MCLR, whereas other intestinal apical membrane enzymes, such as lactase, maltase and alkaline phosphatase were not modified by the treatment. The specific activities of acid phosphatase and succinate dehydrogenase, markers for lysosomal and mitochondrial membranes, respectively, were also increased (32% and 60%, respectively) in treated rats. The analysis of lipid peroxidation showed that the peroxidative status was increased in both serum and intestinal mucosa from MCLR-treated rats, reflecting an excess production of oxygen free radicals induced by this cyanobacterial toxin. In conclusion, this study shows that acute exposure to MCLR affects the intestinal physiology by modifying the intestinal peroxidation status as well as the activity of membrane enzymes.

  7. Antioxidant activities of bambara groundnut (Vigna subterranea) protein hydrolysates and their membrane ultrafiltration fractions.

    PubMed

    Arise, Abimbola K; Alashi, Adeola M; Nwachukwu, Ifeanyi D; Ijabadeniyi, Oluwatosin A; Aluko, Rotimi E; Amonsou, Eric O

    2016-05-18

    In this study, the bambara protein isolate (BPI) was digested with three proteases (alcalase, trypsin and pepsin), to produce bambara protein hydrolysates (BPHs). These hydrolysates were passed through ultrafiltration membranes to obtain peptide fractions of different sizes (<1, 1-3, 3-5 and 5-10 kDa). The hydrolysates and their peptide fractions were investigated for antioxidant activities. The membrane fractions showed that peptides with sizes <3 kDa had significantly (p < 0.05) reduced surface hydrophobicity when compared with peptides >3 kDa. This is in agreement with the result obtained for the ferric reducing power, metal chelating and hydroxyl radical scavenging activities where higher molecular weight peptides exhibited better activity (p < 0.05) when compared to low molecular weight peptide fractions. However, for all the hydrolysates, the low molecular weight peptides were more effective diphenyl-1-picrylhydrazyl (DPPH) radical scavengers but not superoxide radicals when compared to the bigger peptides. In comparison with glutathione (GSH), BPHs and their membrane fractions had better (p < 0.05) reducing power and ability to chelate metal ions except for the pepsin hydrolysate and its membrane fractions that did not show any metal chelating activity. However, the 5-10 kDa pepsin hydrolysate peptide fractions had greater (88%) hydroxyl scavenging activity than GSH, alcalase and trypsin hydrolysates (82%). These findings show the potential use of BPHs and their peptide fraction as antioxidants in reducing food spoilage or management of oxidative stress-related metabolic disorders.

  8. Latent membrane protein 1 of Epstein-Barr virus mimics a constitutively active receptor molecule.

    PubMed Central

    Gires, O; Zimber-Strobl, U; Gonnella, R; Ueffing, M; Marschall, G; Zeidler, R; Pich, D; Hammerschmidt, W

    1997-01-01

    Latent membrane protein 1 (LMP1) of Epstein-Barr virus (EBV) is an integral membrane protein which has transforming potential and is necessary but not sufficient for B-cell immortalization by EBV. LMP1 molecules aggregate in the plasma membrane and recruit tumour necrosis factor receptor (TNF-R) -associated factors (TRAFs) which are presumably involved in the signalling cascade leading to NF-kappaB activation by LMP1. Comparable activities are mediated by CD40 and other members of the TNF-R family, which implies that LMP1 could function as a receptor. LMP1 lacks extended extracellular domains similar to beta-adrenergic receptors but, in contrast, it also lacks any motifs involved in ligand binding. By using LMP1 mutants which can be oligomerized at will, we show that the function of LMP1 in 293 cells and B cells is solely dependent on oligomerization of its carboxy-terminus. Biochemically, oligomerization is an intrinsic property of the transmembrane domain of wild-type LMP1 and causes a constitutive phenotype which can be conferred to the signalling domains of CD40 or the TNF-2 receptor. In EBV, immortalized B cells cross-linking in conjunction with membrane targeting of the carboxy-terminal signalling domain of LMP1 is sufficient for its biological activities. Thus, LMP1 acts like a constitutively activated receptor whose biological activities are ligand-independent. PMID:9359753

  9. Differential membrane fluidization by active and inactive cannabinoid analogues.

    PubMed

    Mavromoustakos, T; Papahatjis, D; Laggner, P

    2001-06-06

    The effects of the two cannabinomimetic drugs (-)-2-(6a,7,10,10a-tetrahydro-6,6,9-trimethyl-1-hydroxy-6H-dibenzo[b,d]pyranyl-2-(hexyl)-1,3-dithiolane (AMG-3) and its pharmacologically less active 1-methoxy analogue (AMG-18) on the thermotropic and structural properties of dipalmitoyl-sn-glycero-3-phosphorylcholine (DPPC) liposomes have been studied by X-ray diffraction and differential scanning calorimetry (DSC). DSC data revealed that the incorporation of the drugs affect differently the thermotropic properties of DPPC. The presence of the more active drug distinctly broadened and attenuated both the pretransition and main phase transition of DPPC bilayers, while the inactive analogue had only minor effects. Small and wide angle X-ray diffraction data showed that the two cannabinoids have different effects on the lipid phase structures and on the hydrocarbon chain packing. The pharmacologically active analogue, AMG-3, was found to efficiently fluidize domains of the lipids in the L(beta)' gel phase, and to perturb the regular multibilayer lattice. In the liquid crystalline L(alpha) phase, AMG-3 was also found to cause irregularities in packing, suggesting that the drug induces local curvature. At the same concentration, the inactive AMG-18 had only minor structural effects on the lipids. At about 10-fold or higher concentrations, AMG-18 was found to produce similar but still less pronounced effects in comparison to those observed by AMG-3. The dose-dependent, different thermotropic and structural effects by the two cannabinoid analogues suggest that these may be related to their biological activity.

  10. A platelet alpha granule membrane protein that is associated with the plasma membrane after activation. Characterization and subcellular localization of platelet activation-dependent granule-external membrane protein.

    PubMed Central

    Berman, C L; Yeo, E L; Wencel-Drake, J D; Furie, B C; Ginsberg, M H; Furie, B

    1986-01-01

    We have identified and purified a platelet integral membrane protein (140,000 mol wt), using the KC4 monoclonal antibody specific for activated platelets, that is internal in resting platelets but exposed on activated platelets (Hsu-Lin S.-C., C.L. Berman, B.C. Furie, D. August, and B. Furie, 1984, J. Biol. Chem. 259: 9121-9126.). The expression of the protein on the platelet surface is secretion-dependent. This protein has been named platelet activation-dependent granule-external membrane (PADGEM) protein. PADGEM protein is distinct from the surface glycoproteins of resting platelets, but identical to the S12 antigen, GMP-140. Using immunofluorescent staining, resting platelets failed to stain for PADGEM protein with the KC4 antibody, but after permeabilization showed a punctate staining of the cell interior. Thrombin-stimulated intact platelets stained with a peripheral rim pattern thus demonstrating the translocation of PADGEM protein from an internal location to the cell surface. PADGEM protein expression on the platelet surface at varying thrombin concentrations correlated with alpha granule release, as measured by the secretion of platelet factor 4. Further evidence for an alpha granule localization of PADGEM protein was provided by nitrogen cavitation of resting platelets followed by metrizamide density gradient centrifugation; PADGEM protein codistributed with platelet factor 4. Using immunoelectron microscopy, the protein was localized to the alpha granule in frozen ultrathin sections of resting platelets labeled using rabbit anti-PADGEM protein antibodies, whereas in thrombin-activated platelets, the plasma membrane was labeled. These studies indicate that PADGEM protein is a component of the alpha granule membrane of resting platelets and is incorporated into the plasma membrane upon activation and secretion. Images PMID:2941452

  11. Glass-supported lipid/polydiacetylene films for colour sensing of membrane-active compounds.

    PubMed

    Volinsky, Roman; Kliger, Mark; Sheynis, Tania; Kolusheva, Sofiya; Jelinek, Raz

    2007-06-15

    Glass-supported biomimetic lipid/polydiacetylene films were employed for colourimetric detection and analysis of amphiphilic and membrane-active molecules. The sensor films comprise lipid monolayers that constitute a biomimetic membrane platform, interspersed within polydiacetylene domains that function as the colour reporter. The optical detection scheme is based on visible blue-red transitions of polydiacetylene, induced by amphiphilic analytes interacting with the film. The colour transitions of the lipid/polydiacetylene films can be either detected by the naked eye, recorded spectroscopically, or registered through digital image analysis using conventional scanning devices. Digital image analysis, in particular, allows quantification of the colourimetric transformations. Detection threshold of micromolar concentration of a membrane-active cytolytic peptide is demonstrated.

  12. Membrane properties induced by anionic phospholipids and phosphatidylethanolamine are critical for the membrane binding and catalytic activity of human cytochrome P450 3A4.

    PubMed

    Kim, Keon-Hee; Ahn, Taeho; Yun, Chul-Ho

    2003-12-30

    Human cytochrome P450 (CYP) 3A4, a membrane anchoring protein, is the major CYP enzyme present in both liver and small intestine. The enzyme plays a major role in the metabolism of many drugs and procarcinogens. The roles of individual phospholipids and membrane properties in the catalytic activity, membrane binding, and insertion into the membrane of CYP3A4 are poorly understood. Here we report that the catalytic activity of testosterone 6beta-hydroxylation, membrane binding, and membrane insertion of CYP3A4 increase as a function of anionic phospholipid concentration in the order phosphatidic acid (PA) > phosphatidylserine (PS) in a binary system of phosphatidylcholine (PC)/anionic phospholipid and as a function of phosphatidylethanolamine (PE) content in ternary systems of PC/PE/PA or PC/PE/PS having a fixed concentration of anionic phospholipids. These results suggest that PA and PE might help the binding of CYP3A4 to the membrane and the interaction with NPR. Cytochrome b(5) (b(5)) and apolipoprotein b(5) further enhanced the testosterone 6beta-hydroxylation activities of CYP3A4 in all tested phospholipids vesicles with various compositions. Phospholipid-dependent changes of the CYP3A4 conformation were also revealed by altered Trp fluorescence and CD spectra. We also found that PE induced the formation of anionic phospholipid-enriched domains in ternary systems using extrinsic fluorescent probes incorporated into lipid bilayers. Taken together, it can be suggested that the chemical and physical properties of membranes induced by anionic phospholipids and PE are critical for the membrane binding and catalytic activity of CYP3A4.

  13. Allosteric activation of membrane-bound glutamate receptors using coordination chemistry within living cells

    NASA Astrophysics Data System (ADS)

    Kiyonaka, Shigeki; Kubota, Ryou; Michibata, Yukiko; Sakakura, Masayoshi; Takahashi, Hideo; Numata, Tomohiro; Inoue, Ryuji; Yuzaki, Michisuke; Hamachi, Itaru

    2016-10-01

    The controlled activation of proteins in living cells is an important goal in protein-design research, but to introduce an artificial activation switch into membrane proteins through rational design is a significant challenge because of the structural and functional complexity of such proteins. Here we report the allosteric activation of two types of membrane-bound neurotransmitter receptors, the ion-channel type and the G-protein-coupled glutamate receptors, using coordination chemistry in living cells. The high programmability of coordination chemistry enabled two His mutations, which act as an artificial allosteric site, to be semirationally incorporated in the vicinity of the ligand-binding pockets. Binding of Pd(2,2‧-bipyridine) at the allosteric site enabled the active conformations of the glutamate receptors to be stabilized. Using this approach, we were able to activate selectively a mutant glutamate receptor in live neurons, which initiated a subsequent signal-transduction pathway.

  14. Rotenone Activates Phagocyte NADPH Oxidase through Binding to Its Membrane Subunit gp91phox

    PubMed Central

    Zhou, Hui; Zhang, Feng; Chen, Shih-heng; Zhang, Dan; Wilson, Belinda; Hong, Jau-shyong; Gao, Hui-Ming

    2011-01-01

    Rotenone, a widely used pesticide, reproduces Parkinsonism in rodents and associates with increased risk for Parkinson’s disease. We previously reported rotenone increased superoxide production through stimulating microglial phagocyte NADPH oxidase (PHOX). The present study identified a novel mechanism by which rotenone activates PHOX. Ligand-binding assay revealed that rotenone directly bound to membrane gp91phox, the catalytic subunit of PHOX; such binding was inhibited by diphenyleneiodonium, a PHOX inhibitor with a binding site on gp91phox. Functional studies showed both membrane and cytosolic subunits were required for rotenone-induced superoxide production in cell-free systems, intact phagocytes, and COS7 cells transfected with membrane subunits (gp91phox/p22phox) and cytosolic subunits (p67phox and p47phox). Rotenone-elicited extracellular superoxide release in p47phox-deficient macrophages suggested rotenone enabled to activate PHOX through a p47phox-independent mechanism. Increased membrane translocation of p67phox, elevated binding of p67phox to rotenone-treated membrane fractions, and co-immunoprecipitation of p67phox and gp91phox in rotenone-treated wild-type and p47phox-deficient macrophages indicated p67phox played a critical role in rotenone-induced PHOX activation via its direct interaction with gp91phox. Rac1, a Rho-like small GTPase, enhanced p67phox-gp91phox interaction; Rac1 inhibition decreased rotenone-elicited superoxide release. In conclusion, rotenone directly interacted with gp91phox; such an interaction triggered membrane translocation of p67phox, leading to PHOX activation and superoxide production. PMID:22094225

  15. Dietary fat effects on brush border membrane composition and enzyme activities in rat intestine.

    PubMed

    Kaur, M; Kaur, J; Ojha, S; Mahmood, A

    1996-01-01

    The effect of dietary fats on the chemical composition and enzyme activities has been studied in intestinal brush border membranes (BBM) or rats. Animals were given commercial rat pellet diet (RP) or semisynthetic diet rich in either saturated [coconut oil (CCO))] or polyunsaturated [n-6, corn oil (CO) or n-3, fish oil (FO)] fat at the 10% level for 5 weeks. The membrane cholesterol/phospholipid ratio was augmented in CO- or RP-fed rats. There was an increase in level of saturated fatty acids in BBM from CCO- or FO-fed animals. n-3 polyunsaturated fatty acid content was raised in FO-fed rats, while the proportion of linoleic acid and arachidonic acid was enhanced in animals given a CO diet. Membrane fluidity was in the order of CCO < RP = CO < FO. The membrane hexose content was high (p < 0.05) in the CCO group. Hexosamines were elevated (p < 0.05) in CCO- or FO-fed rat brush borders. Membrane fucose was unaltered, while sialic acid content was elevated in CO- (p < 0.05) and FO- (p < 0.01) fed vs. CCO-fed rats. Lectin binding to brush borders corroborated these findings. The activities of alkaline phosphatase, sucrase and lactase were augmented (p < 0.001) in CCO-fed animals. Leucine-aminopeptidase and sucrase activities were depressed by FO feeding. The activities of PNP-beta-glycosidases were the highest in FO-fed rats. These results indicate that dietary fat quality markedly affects microvillus membrane lipid composition, glycosylation and enzyme functions in rat intestine.

  16. Active Trans-Plasma Membrane Water Cycling in Yeast Is Revealed by NMR

    PubMed Central

    Zhang, Yajie; Poirier-Quinot, Marie; Springer, Charles S.; Balschi, James A.

    2011-01-01

    Plasma membrane water transport is a crucial cellular phenomenon. Net water movement in response to an osmotic gradient changes cell volume. Steady-state exchange of water molecules, with no net flux or volume change, occurs by passive diffusion through the phospholipid bilayer and passage through membrane proteins. The hypothesis is tested that plasma membrane water exchange also correlates with ATP-driven membrane transport activity in yeast (Saccharomyces cerevisiae). Longitudinal 1H2O NMR relaxation time constant (T1) values were measured in yeast suspensions containing extracellular relaxation reagent. Two-site-exchange analysis quantified the reversible exchange kinetics as the mean intracellular water lifetime (τi), where τi−1 is the pseudo-first-order rate constant for water efflux. To modulate cellular ATP, yeast suspensions were bubbled with 95%O2/5%CO2 (O2) or 95%N2/5%CO2 (N2). ATP was high during O2, and τi−1 was 3.1 s−1 at 25°C. After changing to N2, ATP decreased and τi−1 was 1.8 s−1. The principal active yeast ion transport protein is the plasma membrane H+-ATPase. Studies using the H+-ATPase inhibitor ebselen or a yeast genetic strain with reduced H+-ATPase found reduced τi−1, notwithstanding high ATP. Steady-state water exchange correlates with H+-ATPase activity. At volume steady state, water is cycling across the plasma membrane in response to metabolic transport activity. PMID:22261073

  17. tBid Undergoes Multiple Conformational Changes at the Membrane Required for Bax Activation*

    PubMed Central

    Shamas-Din, Aisha; Bindner, Scott; Zhu, Weijia; Zaltsman, Yehudit; Campbell, Clinton; Gross, Atan; Leber, Brian; Andrews, David W.; Fradin, Cécile

    2013-01-01

    Bid is a Bcl-2 family protein that promotes apoptosis by activating Bax and eliciting mitochondrial outer membrane permeabilization (MOMP). Full-length Bid is cleaved in response to apoptotic stimuli into two fragments, p7 and tBid (p15), that are held together by strong hydrophobic interactions until the complex binds to membranes. The detailed mechanism(s) of fragment separation including tBid binding to membranes and release of the p7 fragment to the cytoplasm remain unclear. Using liposomes or isolated mitochondria with fluorescently labeled proteins at physiological concentrations as in vitro models, we report that the two components of the complex quickly separate upon interaction with a membrane. Once tBid binds to the membrane, it undergoes slow structural rearrangements that result in an equilibrium between two major tBid conformations on the membrane. The conformational change of tBid is a prerequisite for interaction with Bax and is, therefore, a novel step that can be modulated to promote or inhibit MOMP. Using automated high-throughput image analysis in cells, we show that down-regulation of Mtch2 causes a significant delay between tBid and Bax relocalization in cells. We propose that by promoting insertion of tBid via a conformational change at the mitochondrial outer membrane, Mtch2 accelerates tBid-mediated Bax activation and MOMP. Thus the interaction of Mtch2 and tBid is a potential target for therapeutic control of Bid initiated cell death. PMID:23744079

  18. Active Curved Polymers Form Vortex Patterns on Membranes

    NASA Astrophysics Data System (ADS)

    Denk, Jonas; Huber, Lorenz; Reithmann, Emanuel; Frey, Erwin

    2016-04-01

    Recent in vitro experiments with FtsZ polymers show self-organization into different dynamic patterns, including structures reminiscent of the bacterial Z ring. We model FtsZ polymers as active particles moving along chiral, circular paths by Brownian dynamics simulations and a Boltzmann approach. Our two conceptually different methods point to a generic phase behavior. At intermediate particle densities, we find self-organization into vortex structures including closed rings. Moreover, we show that the dynamics at the onset of pattern formation is described by a generalized complex Ginzburg-Landau equation.

  19. Plasma membrane restricted RhoGEF activity is sufficient for RhoA-mediated actin polymerization

    PubMed Central

    van Unen, Jakobus; Reinhard, Nathalie R.; Yin, Taofei; Wu, Yi I.; Postma, Marten; Gadella, Theodorus W.J.; Goedhart, Joachim

    2015-01-01

    The small GTPase RhoA is involved in cell morphology and migration. RhoA activity is tightly regulated in time and space and depends on guanine exchange factors (GEFs). However, the kinetics and subcellular localization of GEF activity towards RhoA are poorly defined. To study the mechanism underlying the spatiotemporal control of RhoA activity by GEFs, we performed single cell imaging with an improved FRET sensor reporting on the nucleotide loading state of RhoA. By employing the FRET sensor we show that a plasma membrane located RhoGEF, p63RhoGEF, can rapidly activate RhoA through endogenous GPCRs and that localized RhoA activity at the cell periphery correlates with actin polymerization. Moreover, synthetic recruitment of the catalytic domain derived from p63RhoGEF to the plasma membrane, but not to the Golgi apparatus, is sufficient to activate RhoA. The synthetic system enables local activation of endogenous RhoA and effectively induces actin polymerization and changes in cellular morphology. Together, our data demonstrate that GEF activity at the plasma membrane is sufficient for actin polymerization via local RhoA signaling. PMID:26435194

  20. Involvement of Hevea latex organelle membrane proteins in the rubber biosynthesis activity and regulatory function.

    PubMed

    Wititsuwaannakul, Dhirayos; Rattanapittayaporn, Atiya; Koyama, Tanetoshi; Wititsuwaannakul, Rapepun

    2004-03-15

    Centrifugation of fresh Hevea rubber latex yields three distinct fractions. The sediment bottom fraction (BF) content of membrane-bound organelles is ca. 20 vol.-% of latex. Prolonged storage or delayed use of fresh latex will result in disintegration and loss of the bottom fraction. This is due to the osmotically sensitive BF rupture and its membrane debris being tightly bound to the top rubber particles (RP) phase. The BF membrane was found to be highly active for rubber biosynthesis (RB), in contrast to previous reports that describe RB only occurring on the RP surface. It was clearly shown that washed BF membrane (WBM) was much more active than fresh RP for RB activity. WBM was highly activated by SDS for RB in a biphasic manner, but SDS strongly inhibited the RP. Probably WBM micelle formation resulted in a highly increased active surface area for RB. C55-PP (UPP) was a very active allylic for WBM in RB function, but inactive for RP. Serial acetone extraction of WBM proteins showed a distinct profile of the fractions with different RB activity. WBM isolated proteins suspended in 2% sodium dodecyl sulfate (SDS) with an RB activity equal to that of intact WBM was with the 20% acetone protein fraction. The 60 and 80% fractions were inactive. Combining the 20 with 80% fractions showed a complete inhibition of RB activity. Complete RB loss was also found when WBM was mixed with the 80% fraction, indicating that WBM has both an enzyme system and a factor for regulation of the RB activity in a well controlled metabolic function for the latex RB process.

  1. Cholesterol-Enriched Domain Formation Induced by Viral-Encoded, Membrane-Active Amphipathic Peptide

    PubMed Central

    Hanson, Joshua M.; Gettel, Douglas L.; Tabaei, Seyed R.; Jackman, Joshua; Kim, Min Chul; Sasaki, Darryl Y.; Groves, Jay T.; Liedberg, Bo; Cho, Nam-Joon; Parikh, Atul N.

    2016-01-01

    The α-helical (AH) domain of the hepatitis C virus nonstructural protein NS5A, anchored at the cytoplasmic leaflet of the endoplasmic reticulum, plays a role in viral replication. However, the peptides derived from this domain also exhibit remarkably broad-spectrum virocidal activity, raising questions about their modes of membrane association. Here, using giant lipid vesicles, we show that the AH peptide discriminates between membrane compositions. In cholesterol-containing membranes, peptide binding induces microdomain formation. By contrast, cholesterol-depleted membranes undergo global softening at elevated peptide concentrations. Furthermore, in mixed populations, the presence of ∼100 nm vesicles of viral dimensions suppresses these peptide-induced perturbations in giant unilamellar vesicles, suggesting size-dependent membrane association. These synergistic composition- and size-dependent interactions explain, in part, how the AH domain might on the one hand segregate molecules needed for viral assembly and on the other hand furnish peptides that exhibit broad-spectrum virocidal activity. PMID:26745420

  2. Atmospheric-pressure plasma activation and surface characterization on polyethylene membrane separator

    NASA Astrophysics Data System (ADS)

    Tseng, Yu-Chien; Li, Hsiao-Ling; Huang, Chun

    2017-01-01

    The surface hydrophilic activation of a polyethylene membrane separator was achieved using an atmospheric-pressure plasma jet. The surface of the atmospheric-pressure-plasma-treated membrane separator was found to be highly hydrophilic realized by adjusting the plasma power input. The variations in membrane separator chemical structure were confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Chemical analysis showed newly formed carbonyl-containing groups and high surface concentrations of oxygen-containing species on the atmospheric-pressure-plasma-treated polymeric separator surface. It also showed that surface hydrophilicity primarily increased from the polar component after atmospheric-pressure plasma treatment. The surface and pore structures of the polyethylene membrane separator were examined by scanning electron microscopy, revealing a slight alteration in the pore structure. As a result of the incorporation of polar functionalities by atmospheric-pressure plasma activation, the electrolyte uptake and electrochemical impedance of the atmospheric-pressure-plasma-treated membrane separator improved. The investigational results show that the separator surface can be controlled by atmospheric-pressure plasma surface treatment to tailor the hydrophilicity and enhance the electrochemical performance of lithium ion batteries.

  3. Both phototropin 1 and 2 localize on the chloroplast outer membrane with distinct localization activity.

    PubMed

    Kong, Sam-Geun; Suetsugu, Noriyuki; Kikuchi, Shingo; Nakai, Masato; Nagatani, Akira; Wada, Masamitsu

    2013-01-01

    Chloroplasts change their position to adapt cellular activities to fluctuating environmental light conditions. Phototropins (phot1 and phot2 in Arabidopsis) are plant-specific blue light photoreceptors that perceive changes in light intensity and direction, and mediate actin-based chloroplast photorelocation movements. Both phot1 and phot2 regulate the chloroplast accumulation response, while phot2 is mostly responsible for the regulation of the avoidance response. Although it has been widely accepted that distinct intracellular localizations of phototropins are implicated in the specificity, the mechanism underlying the phot2-specific avoidance response has remained elusive. In this study, we examined the relationship of the phot2 localization pattern to the chloroplast photorelocation movement. First, the fusion of a nuclear localization signal with phot2, which effectively reduced the amount of phot2 in the cytoplasm, retained the activity for both the accumulation and avoidance responses, indicating that membrane-localized phot2 but not cytoplasmic phot2 is functional to mediate the responses. Importantly, some fractions of phot2, and of phot1 to a lesser extent, were localized on the chloroplast outer membrane. Moreover, the deletion of the C-terminal region of phot2, which was previously shown to be defective in blue light-induced Golgi localization and avoidance response, affected the localization pattern on the chloroplast outer membrane. Taken together, these results suggest that dynamic phot2 trafficking from the plasma membrane to the Golgi apparatus and the chloroplast outer membrane might be involved in the avoidance response.

  4. Mitochondrial metabolic states and membrane potential modulate mtNOS activity.

    PubMed

    Valdez, Laura B; Zaobornyj, Tamara; Boveris, Alberto

    2006-03-01

    The mitochondrial metabolic state regulates the rate of NO release from coupled mitochondria: NO release by heart, liver and kidney mitochondria was about 40-45% lower in state 3 (1.2, 0.7 and 0.4 nmol/min mg protein) than in state 4 (2.2, 1.3 and 0.7 nmol/min mg protein). The activity of mtNOS, responsible for NO release, appears driven by the membrane potential component and not by intramitochondrial pH of the proton motive force. The intramitochondrial concentrations of the NOS substrates, L-arginine (about 310 microM) and NADPH (1.04-1.78 mM) are 60-1000 times higher than their KM values. Moreover, the changes in their concentrations in the state 4-state 3 transition are not enough to explain the changes in NO release. Nitric oxide release was exponentially dependent on membrane potential as reported for mitochondrial H2O2 production [S.S. Korshunov, V.P. Skulachev, A.A. Satarkov, High protonic potential actuates a mechanism of production of reactive oxygen species in mitochondria. FEBS Lett. 416 (1997) 15-18.]. Agents that decrease or abolish membrane potential minimize NO release while the addition of oligomycin that produces mitochondrial hyperpolarization generates the maximal NO release. The regulation of mtNOS activity, an apparently voltage-dependent enzyme, by membrane potential is marked at the physiological range of membrane potentials.

  5. Coordinated autoinhibition of F-BAR domain membrane binding and WASp activation by Nervous Wreck

    PubMed Central

    Stanishneva-Konovalova, Tatiana B.; Kelley, Charlotte F.; Eskin, Tania L.; Messelaar, Emily M.; Wasserman, Steven A.; Sokolova, Olga S.

    2016-01-01

    Membrane remodeling by Fes/Cip4 homology-Bin/Amphiphysin/Rvs167 (F-BAR) proteins is regulated by autoinhibitory interactions between their SRC homology 3 (SH3) and F-BAR domains. The structural basis of autoregulation, and whether it affects interactions of SH3 domains with other cellular ligands, remain unclear. Here we used single-particle electron microscopy to determine the structure of the F-BAR protein Nervous Wreck (Nwk) in both soluble and membrane-bound states. On membrane binding, Nwk SH3 domains do not completely dissociate from the F-BAR dimer, but instead shift from its concave surface to positions on either side of the dimer. Unexpectedly, along with controlling membrane binding, these autoregulatory interactions inhibit the ability of Nwk-SH3a to activate Wiskott–Aldrich syndrome protein (WASp)/actin related protein (Arp) 2/3-dependent actin filament assembly. In Drosophila neurons, Nwk autoregulation restricts SH3a domain-dependent synaptopod formation, synaptic growth, and actin organization. Our results define structural rearrangements in Nwk that control F-BAR–membrane interactions as well as SH3 domain activities, and suggest that these two functions are tightly coordinated in vitro and in vivo. PMID:27601635

  6. Interface design and reinforced features of arrowroot (Maranta arundinacea) starch/polyester-based membranes: Preparation, antioxidant activity, and cytocompatibility.

    PubMed

    Wu, Chin-San; Liao, Hsin-Tzu

    2017-01-01

    The structural, mechanical, antioxidant, and cytocompatibility properties of membranes prepared from the polyhydroxyalkanoate (PHA) and arrowroot (Maranta arundinacea) starch powder (ASP) blend (PHA/ASP) were studied. The acrylic acid-grafted PHA (PHA-g-AA) and the coupling agent treated ASP (TASP) were used to enhance the desired characteristics of these membranes. The PHA-g-AA/TASP membranes had better mechanical properties than the PHA/ASP membrane. This effect was attributed to greater compatibility between the grafted PHA and TASP. The water resistance of the PHA-g-AA/TASP membranes was greater than that of the PHA/ASP membranes, and a cytocompatibility evaluation with human foreskin fibroblasts (FBs) indicated that both materials were nontoxic. Moreover, both ASP and TASP enhanced the polyphenol content and antioxidant properties of the membranes. PHA-g-AA/TASP and PHA/ASP membranes had better antioxidant activity than the control group.

  7. Membrane interactions and biological activity of antimicrobial peptides from Australian scorpion.

    PubMed

    Luna-Ramírez, Karen; Sani, Marc-Antoine; Silva-Sanchez, Jesus; Jiménez-Vargas, Juana María; Reyna-Flores, Fernando; Winkel, Kenneth D; Wright, Christine E; Possani, Lourival D; Separovic, Frances

    2014-09-01

    UyCT peptides are antimicrobial peptides isolated from the venom of the Australian scorpion. The activity of the UyCT peptides against Gram positive and Gram negative bacteria and red blood cells was determined. The membrane interactions of these peptides were evaluated by dye release (DR) of the fluorophore calcein from liposomes and isothermal titration calorimetry (ITC); and their secondary structure was determined by circular dichroism (CD). Three different lipid systems were used to mimic red blood cells, Escherichia coli and Staphylococcus aureus membranes. UyCT peptides exhibited broad spectrum antimicrobial activity with low MIC for S. aureus and multi-drug resistant Gram negative strains. Peptide combinations showed some synergy enhancing their potency but not hemolytic activity. The UyCT peptides adopted a helical structure in lipid environments and DR results confirmed that the mechanism of action is by disrupting the membrane. ITC data indicated that UyCT peptides preferred prokaryotic rather than eukaryotic membranes. The overall results suggest that UyCT peptides could be pharmaceutical leads for the treatment of Gram negative multiresistant bacterial infections, especially against Acinetobacter baumanni, and candidates for peptidomimetics to enhance their potency and minimize hemolysis. This article is part of a Special Issue entitled: Interfacially Active Peptides and Proteins. Guest Editors: William C. Wimley and Kalina Hristova.

  8. Combining phosphate and bacteria removal on chemically active filter membranes allows prolonged storage of drinking water.

    PubMed

    Rotzetter, A C C; Kellenberger, C R; Schumacher, C M; Mora, C; Grass, R N; Loepfe, M; Luechinger, N A; Stark, W J

    2013-11-13

    A chemically active filtration membrane with incorporated lanthanum oxide nanoparticles enables the removal of bacteria and phosphate at the same time and thus provides a simple device for preparation of drinking water and subsequent safe storage without using any kind of disinfectants.

  9. T Lymphocyte Activation Threshold and Membrane Reorganization Perturbations in Unique Culture Model

    NASA Technical Reports Server (NTRS)

    Adams, C. L.; Sams, C. F.

    2000-01-01

    Quantitative activation thresholds and cellular membrane reorganization are mechanisms by which resting T cells modulate their response to activating stimuli. Here we demonstrate perturbations of these cellular processes in a unique culture system that non-invasively inhibits T lymphocyte activation. During clinorotation, the T cell activation threshold is increased 5-fold. This increased threshold involves a mechanism independent of TCR triggering. Recruitment of lipid rafts to the activation site is impaired during clinorotation but does occur with increased stimulation. This study describes a situation in which an individual cell senses a change in its physical environment and alters its cell biological behavior.

  10. Antibacterial Activity of Shikimic Acid from Pine Needles of Cedrus deodara against Staphylococcus aureus through Damage to Cell Membrane

    PubMed Central

    Bai, Jinrong; Wu, Yanping; Liu, Xiaoyan; Zhong, Kai; Huang, Yina; Gao, Hong

    2015-01-01

    Shikimic acid (SA) has been reported to possess antibacterial activity against Staphylococcus aureus, whereas the mode of action of SA is still elusive. In this study, the antibacterial activity and mechanism of SA toward S. aureus by cell membrane damage was investigated. After SA treatment, massive K+ and nucleotide leakage from S. aureus, and a significant change in the membrane potential was observed, suggesting SA may act on the membrane by destroying the cell membrane permeability. Through transmission electron microscopic observations we further confirmed that SA can disrupt the cell membrane and membrane integrity. Meanwhile, SA was found to be capable of reducing the membrane fluidity of the S. aureus cell. Moreover, the fluorescence experiments indicated that SA could quench fluorescence of Phe residues of the membrane proteins, thus demonstrating that SA can bind to S. aureus membrane proteins. Therefore, these results showed the antibacterial activity of SA against S. aureus could be caused by the interactions of SA with S. aureus membrane proteins and lipids, resulting in causing cell membrane dysfunction and bacterial damage or even death. This study reveals the potential use of SA as an antibacterial agent. PMID:26580596

  11. Mapping membrane activity in undiscovered peptide sequence space using machine learning.

    PubMed

    Lee, Ernest Y; Fulan, Benjamin M; Wong, Gerard C L; Ferguson, Andrew L

    2016-11-29

    There are some ∼1,100 known antimicrobial peptides (AMPs), which permeabilize microbial membranes but have diverse sequences. Here, we develop a support vector machine (SVM)-based classifier to investigate ⍺-helical AMPs and the interrelated nature of their functional commonality and sequence homology. SVM is used to search the undiscovered peptide sequence space and identify Pareto-optimal candidates that simultaneously maximize the distance σ from the SVM hyperplane (thus maximize its "antimicrobialness") and its ⍺-helicity, but minimize mutational distance to known AMPs. By calibrating SVM machine learning results with killing assays and small-angle X-ray scattering (SAXS), we find that the SVM metric σ correlates not with a peptide's minimum inhibitory concentration (MIC), but rather its ability to generate negative Gaussian membrane curvature. This surprising result provides a topological basis for membrane activity common to AMPs. Moreover, we highlight an important distinction between the maximal recognizability of a sequence to a trained AMP classifier (its ability to generate membrane curvature) and its maximal antimicrobial efficacy. As mutational distances are increased from known AMPs, we find AMP-like sequences that are increasingly difficult for nature to discover via simple mutation. Using the sequence map as a discovery tool, we find a unexpectedly diverse taxonomy of sequences that are just as membrane-active as known AMPs, but with a broad range of primary functions distinct from AMP functions, including endogenous neuropeptides, viral fusion proteins, topogenic peptides, and amyloids. The SVM classifier is useful as a general detector of membrane activity in peptide sequences.

  12. Synthetic activity enhancement of membrane-bound lipase from Rhizopus chinensis by pretreatment with isooctane.

    PubMed

    Wang, Dong; Xu, Yan; Teng, Yun

    2007-05-01

    The cell-bound lipase from Rhizopus chinensis CCTCC M201021 with high catalysis ability for ester synthesis was located as a membrane-bound lipase by the treatments of Yatalase firstly. In order to improve its synthetic activity in non-aqueous phase, the pretreatments of this enzyme with various organic solvents were investigated. The pretreatment with isooctane improved evidently the lipase synthetic activity, resulting in about 139% in relative synthetic activity and 115% in activity recovery. The morphological changes of mycelia caused by organic solvent pretreatments could influence the exposure of the membrane-bound enzyme from mycelia and the exhibition of the lipase activity. The pretreatment conditions with isooctane and acetone were further investigated, and the optimum effect was obtained by the isooctane pretreatment at 4 degrees C for 1 h, resulting in 156% in relative synthetic activity and 126% in activity recovery. When the pretreated lipases were employed as catalysts for the esterification production of ethyl hexanoate in heptane, higher initial reaction rate and higher final molar conversion were obtained using the lipase pretreated with isooctane, compared with the untreated lyophilized one. This result suggested that the pretreatment of the membrane-bound lipase with isooctane could be an effective method to substitute the lyophilization for preparing biocatalysts used in non-aqueous phase reactions.

  13. Growth-inhibitory activity of lymphoid cell plasma membranes. II. Partial characterization of the inhibitor

    PubMed Central

    1984-01-01

    We have shown that plasma membranes from lymphoid cells have inhibitory activity for the growth of normal lymphocytes and lymphoid tumor cells (Stallcup, K. C., A. Dawson, and M. F. Mescher, J. Cell Biol. 99:1221- 1226). This growth-inhibitory activity has been found to co-purify with major histocompatibility complex class I antigens (H-2K and D) when these cell surface glycoproteins are isolated from detergent lysates of cells by affinity chromatography on monoclonal antibody columns. When incorporated into liposomes, the affinity-purified H-2 antigens inhibited the growth of both normal lymphocytes and tumor cells at concentrations of 1-3 micrograms/ml. Inhibition was readily reversed upon removal of the liposomes from the cell cultures, even after several days of exposure of cells to the inhibitor. Inhibitory activity was insensitive to protease digestion or heat treatment, indicating that it was not due to the H-2 glycoproteins. This was confirmed by the demonstration that inhibitory activity could be separated from the H-2 protein by gel filtration in the presence of deoxycholate and could be extracted from membranes or H-2 antigen preparations with organic solvents. The results demonstrate that the growth-inhibitory component(s) of the plasma membrane is a minor lipid or lipid-like molecule which retains activity in the absence of other membrane components. The findings reported here and in the preceding article suggest that this novel membrane component may have a role in control of lymphoid cell growth, possibly mediated by cell contacts. PMID:6332814

  14. Fusicoccin Binding to Its Plasma Membrane Receptor and the Activation of the Plasma Membrane H+-ATPase1

    PubMed Central

    Olivari, Claudio; Meanti, Cristina; De Michelis, Maria Ida; Rasi-Caldogno, Franca

    1998-01-01

    Different approaches were utilized to investigate the mechanism by which fusicoccin (FC) induces the activation of the H+-ATPase in plasma membrane (PM) isolated from radish (Raphanus sativus L.) seedlings treated in vivo with (FC-PM) or without (C-PM) FC. Treatment of FC-PM with different detergents indicated that PM H+-ATPase and the FC-FC-binding-protein (FCBP) complex were solubilized to a similar extent. Fractionation of solubilized FC-PM proteins by a linear sucrose-density gradient showed that the two proteins comigrated and that PM H+-ATPase retained the activated state induced by FC. Solubilized PM proteins were also fractionated by a fast-protein liquid chromatography anion-exchange column. Comparison between C-PM and FC-PM indicated that in vivo treatment of the seedlings with FC caused different elution profiles; PM H+-ATPase from FC-PM was only partially separated from the FC-FCBP complex and eluted at a higher NaCl concentration than did PM H+-ATPase from C-PM. Western analysis of fast-protein liquid chromatography fractions probed with an anti-N terminus PM H+-ATPase antiserum and with an anti-14–3-3 antiserum indicated an FC-induced association of FCBP with the PM H+-ATPase. Analysis of the activation state of PM H+-ATPase in fractions in which the enzyme was partially separated from FCBP suggested that the establishment of an association between the two proteins was necessary to maintain the FC-induced activation of the enzyme. PMID:9489010

  15. Amphiphilic Indole Derivatives as Antimycobacterial Agents: Structure-Activity Relationships and Membrane Targeting Properties.

    PubMed

    Yang, Tianming; Moreira, Wilfried; Nyantakyi, Samuel Agyei; Chen, Huan; Aziz, Dinah Binte; Go, Mei-Lin; Dick, Thomas

    2017-03-28

    Antibacterials that disrupt cell membrane function have the potential to eradicate "persister" organisms and delay the emergence of resistance. Here we report the antimycobacterial activities of 4-fluoro and 6-methoxyindoles bearing a cationic amphiphilic motif represented by a lipophilic n-octyl side chain at position 1 and a positively charged azepanyl or 1,4-dioxa-8-azaspiro[4.5]decane moiety at position 3. These analogues exhibited balanced profiles of potency (Mycobacterium bovis BCG, M tuberculosis H37Rv), selective activity, solubility, and metabolic stability. Bacteriological mechanism of action investigations on a representative analogue revealed cell membrane permeabilization and depolarization in M bovis BCG. These membrane-related changes preceded cell death indicating that the loss in membrane integrity was not an epiphenomenon. Bactericidal activity was observed against both growing and nongrowing mycobacterial cultures. The analogue also upregulated cell envelope stress-inducible promoters piniBAC and pclgR, implicating the involvement of envelope-related targets in its mode of action.

  16. A packed bed membrane reactor for production of biodiesel using activated carbon supported catalyst.

    PubMed

    Baroutian, Saeid; Aroua, Mohamed K; Raman, Abdul Aziz A; Sulaiman, Nik M N

    2011-01-01

    In this study, a novel continuous reactor has been developed to produce high quality methyl esters (biodiesel) from palm oil. A microporous TiO2/Al2O3 membrane was packed with potassium hydroxide catalyst supported on palm shell activated carbon. The central composite design (CCD) of response surface methodology (RSM) was employed to investigate the effects of reaction temperature, catalyst amount and cross flow circulation velocity on the production of biodiesel in the packed bed membrane reactor. The highest conversion of palm oil to biodiesel in the reactor was obtained at 70 °C employing 157.04 g catalyst per unit volume of the reactor and 0.21 cm/s cross flow circulation velocity. The physical and chemical properties of the produced biodiesel were determined and compared with the standard specifications. High quality palm oil biodiesel was produced by combination of heterogeneous alkali transesterification and separation processes in the packed bed membrane reactor.

  17. Block copolymer hollow fiber membranes with catalytic activity and pH-response.

    PubMed

    Hilke, Roland; Pradeep, Neelakanda; Madhavan, Poornima; Vainio, Ulla; Behzad, Ali Reza; Sougrat, Rachid; Nunes, Suzana P; Peinemann, Klaus-Viktor

    2013-08-14

    We fabricated block copolymer hollow fiber membranes with self-assembled, shell-side, uniform pore structures. The fibers in these membranes combined pores able to respond to pH and acting as chemical gates that opened above pH 4, and catalytic activity, achieved by the incorporation of gold nanoparticles. We used a dry/wet spinning process to produce the asymmetric hollow fibers and determined the conditions under which the hollow fibers were optimized to create the desired pore morphology and the necessary mechanical stability. To induce ordered micelle assembly in the doped solution, we identified an ideal solvent mixture as confirmed by small-angle X-ray scattering. We then reduced p-nitrophenol with a gold-loaded fiber to confirm the catalytic performance of the membranes.

  18. Treatment of coal gasification wastewater by membrane bioreactor hybrid powdered activated carbon (MBR–PAC) system.

    PubMed

    Jia, Shengyong; Han, Hongjun; Hou, Baolin; Zhuang, Haifeng; Fang, Fang; Zhao, Qian

    2014-12-01

    A laboratory-scale membrane bioreactor hybrid powdered activated carbon (MBR–PAC) system was developed to treat coal gasification wastewater to enhance the COD, total phenols (TPh), NH4+ removals and migrate the membrane fouling. Since the MBR–PAC system operated with PAC dosage of 4 g L−1, the maximum removal efficiencies of COD, TPh and NH4+ reached 93%, 99% and 63%, respectively with the corresponding influent concentrations of 2.27 g L−1, 497 mg L−1 and 164 mg N L−1; the PAC extraction efficiencies of COD, TPh and NH4+ were 6%, 3% and 13%, respectively; the transmembrane pressure decreased 34% with PAC after 50 d operation. The results demonstrate that PAC played a key role in the enhancement of biodegradability and mitigation of membrane fouling.

  19. Optical activity of membrane suspensions: calculation of artifacts by Mie scattering theory.

    PubMed

    Gordon, D J; Holzwarth, G

    1971-10-01

    The circular dichroism, optical rotatory dispersion, and optical density of a suspension of erythrocyte ghosts are calculated from the measured optical properties of solubilized ghosts by classical general scattering theory (Mie theory). The ghost is represented by a solvent-filled spherical shell 7 nm (70 A) thick and 3.5 mum in radius. The 3- to 5-nm red shifts and unusual band shapes observed in the circular dichroism and optical rotary dispersion of suspensions of the intact ghosts, but not in the solubilized membranes, are reproduced by these calculations. Both differential absorption and differential scattering of left-and right-circularly polarized light contribute significantly to the calculated circular dichroism spectra. The artifacts of small membrane vesicles are shown to be less than those of intact ghosts. It is concluded that the characteristic anomalies in the optical activity of membrane suspensions are artifactual.

  20. The effect of charged lipids on bacteriorhodopsin membrane reconstitution and its photochemical activities

    SciTech Connect

    Wang Zhen; Bai Jing; Xu Yuhong

    2008-07-11

    Bacteriorhodopsin (BR) was reconstituted into artificial lipid membrane containing various charged lipid compositions. The proton pumping activity of BR under flash and continuous illumination, proton permeability across membrane, as well as the decay kinetics of the photocycle intermediate M{sub 412} were studied. The results showed that lipid charges would significantly affect the orientation of BR inserted into lipid membranes. In liposomes containing anionic lipids, BRs were more likely to take natural orientation as in living cells. In neutral or positively charged liposomes, most BRs were reversely assembled, assuming an inside out orientation. Moreover, the lipids charges also affect BR's M intermediate kinetics, especially the slow component in M intermediate decay. The half-life M{sub 412s} increased significantly in BRs in liposomes containing cationic lipids, while decreased in those in anionic liposomes.

  1. Effect of powdered activated carbon on integrated submerged membrane bioreactor-nanofiltration process for wastewater reclamation.

    PubMed

    Woo, Yun Chul; Lee, Jeong Jun; Shim, Wang-Geun; Shon, Ho Kyong; Tijing, Leonard D; Yao, Minwei; Kim, Han-Seung

    2016-06-01

    The aim of this study was to determine the effect of powdered activated carbon (PAC) on the overall performance of a submerged membrane bioreactor (SMBR) system integrated with nanofiltration (NF) for wastewater reclamation. It was found that the trans-membrane pressure of SMBR increased continuously while that of the SMBR with PAC was more stable, mainly because water could still pass through the PACs and membrane even though foulants adhered on the PAC surface. The presence of PAC was able to mitigate fouling in SMBR as well as in NF. SMBR-NF with PAC obtained a higher flux of 8.1 LMH compared to that without PAC (6.6 LMH). In addition, better permeate quality was obtained with SMBR-NF integrated process added with PAC. The present results suggest that the addition of PAC in integrated SMBR-NF process could possibly lead to satisfying water quality and can be operated for a long-term duration.

  2. PMCA activity and membrane tubulin affect deformability of erythrocytes from normal and hypertensive human subjects.

    PubMed

    Monesterolo, Noelia E; Nigra, Ayelen D; Campetelli, Alexis N; Santander, Verónica S; Rivelli, Juan F; Arce, Carlos A; Casale, Cesar H

    2015-11-01

    Our previous studies demonstrated formation of a complex between acetylated tubulin and brain plasma membrane Ca(2+)-ATPase (PMCA), and the effect of the lipid environment on structure of this complex and on PMCA activity. Deformability of erythrocytes from hypertensive human subjects was reduced by an increase in membrane tubulin content. In the present study, we examined the regulation of PMCA activity by tubulin in normotensive and hypertensive erythrocytes, and the effect of exogenously added diacylglycerol (DAG) and phosphatidic acid (PA) on erythrocyte deformability. Some of the key findings were that: (i) PMCA was associated with tubulin in normotensive and hypertensive erythrocytes, (ii) PMCA enzyme activity was directly correlated with erythrocyte deformability, and (iii) when tubulin was present in the erythrocyte membrane, treatment with DAG or PA led to increased deformability and associated PMCA activity. Taken together, our findings indicate that PMCA activity is involved in deformability of both normotensive and hypertensive erythrocytes. This rheological property of erythrocytes is affected by acetylated tubulin and its lipid environment because both regulate PMCA activity.

  3. Depth heterogeneity of fully aromatic polyamide active layers in reverse osmosis and nanofiltration membranes.

    PubMed

    Coronell, Orlando; Mariñas, Benito J; Cahill, David G

    2011-05-15

    We studied the depth heterogeneity of fully aromatic polyamide (PA) active layers in commercial reverse osmosis (RO) and nanofiltration (NF) membranes by quantifying near-surface (i.e., top 6 nm) and volume-averaged properties of the active layers using X-ray photoelectron spectrometry (XPS) and Rutherford backscattering spectrometry (RBS), respectively. Some membranes (e.g., ESPA3 RO) had active layers that were depth homogeneous with respect to the concentration and pK(a) distribution of carboxylic groups, degree of polymer cross-linking, concentration of barium ion probe that associated with ionized carboxylic groups, and steric effects experienced by barium ion. Other membranes (e.g., NF90 NF) had active layers that were depth heterogeneous with respect to the same properties. Our results therefore support the existence of both depth-homogeneous and depth-heterogeneous active layers. It remains to be assessed whether the depth heterogeneity consists of gradually changing properties throughout the active layer depth or of distinct sublayers with different properties.

  4. "Active surfaces" formed by immobilization of enzymes on solid-supported polymer membranes.

    PubMed

    Draghici, Camelia; Kowal, Justyna; Darjan, Alina; Meier, Wolfgang; Palivan, Cornelia G

    2014-10-07

    In various domains ranging from catalysis to medical and environmental sciences, there is currently much focus on the design of surfaces that present active compounds at the interface with their environments. Here, we describe the design of "active surfaces" based on solid-supported monolayers of asymmetric triblock copolymers, which serve as templates for the attachment of enzymes. A group of poly(ethylene glycol)-block-poly(γ-methyl-ε-caprolactone)-block-poly[(2-dimethylamino) ethyl methacrylate] amphiphilic copolymers, with different hydrophilic and hydrophobic domains (PEG45-b-PMCLx-b-PDMAEMAy) was selected to generate solid-supported polymer membranes. The behavior of the copolymers in terms of their molecular arrangements at the air-water interface was established by a combination of Langmuir isotherms and Brewster angle microscopy. Uniform thin layers of copolymers were obtained by transferring films onto silica solid supports at optimal surface pressure. These solid-supported polymer membranes were characterized by assessing various properties, such as monolayer thickness, hydrophilic/hydrophobic balance, topography, and roughness. Laccase, used as an enzyme model, was successfully attached to copolymer membranes by stable interactions as followed by quartz crystal microbalance with dissipation measurements, and its activity was preserved, as indicated by activity assays. The interaction between the amphiphilic triblock copolymer films and immobilized enzymes represents a straightforward approach to engineer "active surfaces", with biomolecules playing the active role by their intrinsic bioactivity.

  5. Glucose-induced activation of the plasma membrane H(+)-ATPase in Fusarium oxysporum.

    PubMed

    Brandão, R L; Castro, I M; Passos, J B; Nicoli, J R; Thevelein, J M

    1992-08-01

    Addition of glucose and other sugars to derepressed cells of the fungus Fusarium oxysporum var. lini triggered activation of the plasma membrane H(+)-ATPase within 5 min. Glucose was the best activator while galactose and lactose had a lesser effect. The activation was not prevented by previous addition of cycloheximide and it was fully reversible when the glucose was removed. The activation process in vivo also caused changes in the kinetic properties of the enzyme. The non-activated enzyme had an apparent Km of about 3.2 mM for ATP whereas the activated enzyme showed an apparent Km of 0.26 mM. In addition, the pH optimum of the H(+)-ATPase changed from 6.0 to 7.5 upon activation. The activated enzyme was more sensitive to inhibition by vanadate. When F. oxysporum was cultivated in media containing glucose as the major carbon source, enhanced H(+)-ATPase activity was largely confined to the period corresponding to the lag phase, i.e. just before the start of acidification of the medium. This suggests that the activation process might play a role in the onset of extracellular acidification. Addition of glucose to F. oxysporum var. lini cells also caused an increase in the cAMP level. No reliable increase could be demonstrated for the other sugars. Addition of proton ionophores such as DNP and CCCP at pH 5.0 caused both a large increase in the intracellular level of cAMP and in the activity of the plasma membrane H(+)-ATPase. Inhibition of the DNP-induced increase in the cAMP level by acridine orange also resulted in inhibition of the activation of plasma membrane H(+)-ATPase.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. PVDF-HFP/ether-modified polysiloxane membranes obtained via airbrush spraying as active separators for application in lithium ion batteries.

    PubMed

    Seidel, S M; Jeschke, S; Vettikuzha, P; Wiemhöfer, H-D

    2015-08-04

    Improved hybrid polymer electrolyte membranes are introduced based on ether-modified polysiloxanes and poly(vinylidene fluoride-co-hexafluoropropylene) yielding a safe separator membrane, which is able to be sprayed directly onto lithium ion battery active materials, with an active role for enhanced ion transport.

  7. Correlating antimicrobial activity and model membrane leakage induced by nylon-3 polymers and detergents.

    PubMed

    Hovakeemian, Sara G; Liu, Runhui; Gellman, Samuel H; Heerklotz, Heiko

    2015-09-14

    Most antimicrobial peptides act upon target microorganisms by permeabilizing their membranes. The mode of action is often assessed by vesicle leakage experiments that use model membranes, with the assumption that biological activity correlates with the permeabilization of the lipid bilayer. The current work aims to extend the interpretation of vesicle leakage results and examine the correlation between vesicle leakage and antimicrobial activity. To this end, we used a lifetime-based leakage assay with calcein-loaded vesicles to study the membrane permeabilizing properties of a novel antifungal polymer poly-NM, two of its analogs, and a series of detergents. In conjunction, the biological activities of these compounds against Candida albicans were assessed and correlated with data from vesicle leakage. Poly-NM induces all-or-none leakage in polar yeast lipid vesicles at the polymer's MIC, 3 μg mL(-1). At this and higher concentrations, complete leakage after an initial lag time was observed. Concerted activity tests imply that this polymer acts independently of the detergent octyl glucoside (OG) for both vesicle leakage and activity against C. albicans spheroplasts. In addition, poly-NM was found to have negligible activity against zwitterionic vesicles and red blood cells. Our results provide a consistent, detailed picture of the mode of action of poly-NM: this polymer induces membrane leakage by electrostatic lipid clustering. In contrast, poly-MM:CO, a nylon-3 polymer comprised of both cationic and hydrophobic segments, seems to act by a different mechanism that involves membrane asymmetry stress. Vesicle leakage for this polymer is transient (limited to <100%) and graded, non-specific among zwitterionic and polar yeast lipid vesicles, additive with detergent action, and correlates poorly with biological activity. Based on these results, we conclude that comprehensive leakage experiments can provide a detailed description of the mode of action of membrane

  8. Correlating antimicrobial activity and model membrane leakage induced by nylon-3 polymers and detergents

    PubMed Central

    Hovakeemian, Sara G.; Liu, Runhui; Gellman, Samuel H.; Heerklotz, Heiko

    2015-01-01

    Most antimicrobial peptides act upon target microorganisms by permeabilizing their membranes. The mode of action is often assessed by vesicle leakage experiments that use model membranes, with the assumption that biological activity arises from permeabilization of the lipid bilayer. The current work aims to extend the interpretation of vesicle leakage results and examine the correlation between vesicle leakage and antimicrobial activity. To this end, we used a lifetime-based leakage assay with calcein-loaded vesicles to study the membrane permeabilizing properties of a novel antifungal polymer poly-NM, two of its analogs, and a series of detergents. In conjunction, the biological activities of these compounds against Candida albicans were assessed and correlated with data from vesicle leakage. Poly-NM induces all-or-none leakage in polar yeast lipid vesicles at the polymer’s MIC, 3 μg/mL. At this and higher concentrations, complete leakage after an initial lag time was observed. Concerted activity tests imply that this polymer acts independently of the detergent octyl glucoside (OG) for both vesicle leakage and activity against C. albicans spheroplasts. In addition, Poly-NM was found to have negligible activity against zwitterionic vesicles and red blood cells. Our results provide a consistent, detailed picture of the mode of action of Poly-NM: this polymer induces membrane leakage by electrostatic lipid clustering. In contrast, Poly-MM:CO, a nylon-3 polymer comprised of both cationic and hydrophobic segments, seems to act by a different mechanism that involves membrane asymmetry stress. Vesicle leakage for this polymer is transient (limited to <100%) and graded, non-specific among zwitterionic and polar yeast lipid vesicles, additive with detergent action, and correlates poorly with biological activity. Based on these results, we conclude that comprehensive leakage experiments can provide a detailed description of the mode of action of membrane permeabilizing

  9. Membrane foulants and fouling mechanisms in microfiltration and ultrafiltration of an activated sludge effluent.

    PubMed

    Nguyen, S T; Roddick, F A; Harris, J L

    2010-01-01

    Membrane fouling in microfiltration (MF) and ultrafiltration (UF) of an activated sludge (AS) effluent was investigated. It was found that the major membrane foulants were polysaccharides, proteins, polysaccharide-like and protein-like materials and humic substances. MF fouling by the raw effluent was governed by pore adsorption of particles smaller than the pores during the first 30 minutes of filtration and then followed the cake filtration model. UF fouling could be described by the cake filtration model throughout the course of filtration. Coagulation with alum and (poly)aluminium chlorohydrate (ACH) altered the MF fouling mechanism to follow the cake filtration model from the beginning of filtration. The MF and UF flux improvement by coagulation was due to the removal of some of the foulants in the raw AS effluent by the coagulants. The MF flux improvement was greater for alum than for ACH whereas the two coagulants performed equally well in UF. Coagulation also reduced hydraulically irreversible fouling on the membranes and this effect was more prominent in MF than in UF. The unified membrane fouling index (UMFI) was used to quantitatively evaluate the effectiveness of coagulation on membrane flux enhancement.

  10. Electrical activation of Na/K pumps can increase ionic concentration gradient and membrane resting potential.

    PubMed

    Chen, Wei; Dando, Robin

    2006-01-01

    It has been previously demonstrated by our group that our specifically designed synchronization modulation electric field can dynamically entrain the Na/K ATPase molecules, effectively accelerating the pumping action of these molecules. The ATPase molecules are first synchronized by the field, and subsequently their pumping rates are gradually modulated in a stepwise pattern to progressively higher and higher levels. Here, we present results obtained on application of the field to intact twitch skeletal muscle fibers. The ionic concentration gradient across the cell membrane was monitored, with the membrane potential extrapolated using a slow fluorescent probe with a confocal microimaging technique. The applied synchronization-modulation electric field is able to slowly but consistently increase the ionic concentration gradient across the membrane and, hence, hyperpolarize the membrane potential. All of these results were fully eliminated if ouabain was applied to the bathing solution, indicating a correlation with the action of the Na/K pump molecules. These results in combination with our previous results into the entrainment of the pump molecules show that the synchronization-modulation electric field-induced activation of the Na/K pump functions can effectively increase the ionic concentration gradient and the membrane potential.

  11. Scolopendin 2, a cationic antimicrobial peptide from centipede, and its membrane-active mechanism.

    PubMed

    Lee, Heejeong; Hwang, Jae-Sam; Lee, Jaeho; Kim, Jae Il; Lee, Dong Gun

    2015-02-01

    Scolopendin 2 is a 16-mer peptide (AGLQFPVGRIGRLLRK) derived from the centipede Scolopendra subspinipes mutilans. We observed that this peptide exhibited antimicrobial activity in a salt-dependent manner against various fungal and bacterial pathogens and showed no hemolytic effect in the range of 1.6 μM to 100 μM. Circular dichroism analysis showed that the peptide has an α-helical properties. Furthermore, we determined the mechanism(s) of action using flow cytometry and by investigating the release of intracellular potassium. The results showed that the peptide permeabilized the membranes of Escherichia coli O157 and Candida albicans, resulting in loss of intracellular potassium ions. Additionally, bis-(1,3-dibutylbarbituric acid) trimethine oxonol and 3,3'-dipropylthiacarbocyanine iodide assays showed that the peptide caused membrane depolarization. Using giant unilamellar vesicles encapsulating calcein and large unilamellar vesicles containing fluorescein isothiocyanate-dextran, which were similar in composition to typical E. coli O157 and C. albicans membranes, we demonstrated that scolopendin 2 disrupts membranes, resulting in a pore size between 4.8 nm and 5.0 nm. Thus, we have demonstrated that a cationic antimicrobial peptide, scolopendin 2, exerts its broad-spectrum antimicrobial effects by forming pores in the cell membrane.

  12. Correlation of EPS content in activated sludge at different sludge retention times with membrane fouling phenomena.

    PubMed

    Al-Halbouni, Djamila; Traber, Jacqueline; Lyko, Sven; Wintgens, Thomas; Melin, Thomas; Tacke, Daniela; Janot, Andreas; Dott, Wolfgang; Hollender, Juliane

    2008-03-01

    In this study, activated sludge characteristics were studied with regard to membrane fouling in membrane bioreactors (MBRs) for two pilot plants and one full-scale plant treating municipal wastewater. For the full-scale MBR, concentrations of extracellular polymeric substances (EPS) bound to sludge flocs were shown to have seasonal variations from as low as 17mgg(-1) dry matter (DM) in summer up to 51mg(gDM)(-1) in winter, which correlated with an increased occurrence of filamentous bacteria in the colder season. Therefore, it was investigated at pilot-scale MBRs with different sludge retention times (SRTs) whether different EPS contents and corresponding sludge properties influence membrane fouling. Activated sludge from the pilot MBR with low SRT (23d) was found to have worse filterability, settleability and dewaterability. Photometric analysis of EPS extracts as well as LC-OCD measurements showed that it contained significantly higher concentrations of floc-bound EPS than sludge at higher SRT (40d) The formation of fouling layers on the membranes, characterised by SEM-EDX as well as photometric analysis of EPS extracts, was more distinct at lower SRT where concentrations of deposited EPS were 40-fold higher for proteins and 5-fold higher for carbohydrates compared with the membrane at higher SRT. Floc-bound EPS and metals were suggested to play a role in the fouling process at the full-scale MBR and this was confirmed by the pilot-scale study. However, despite the different sludge properties, the permeability of membranes was found to be similar.

  13. Age characteristics of changes in invertase activity of the mucous membrane of the small intestine

    NASA Technical Reports Server (NTRS)

    Rakhimov, K. R.; Aleksandrova, N. V.

    1980-01-01

    Rats of varying ages were subjected to stress from heat, cold, and hydrocortisone injection. Invertase activity in homogenates of small intestine mucous membranes was studied following sacrifice. Invertase activity was low in young animals, but increased sharply in 30 day old ones, remaining at a relatively constant level until old age. The study concludes that the stress hormone (corticosteroids, etc.) levels in the blood, which affects the formation of enteric enzyme levels and activities, and that age related peculiarities in invertase activity are a consequence of altered hormone status and epitheliocyte sensitivity.

  14. Measuring the activity of heterotrophic microorganism in membrane bioreactor for drinking water treatment.

    PubMed

    Han, Zheng-Shuang; Tian, Jia-Yu; Liang, Heng; Ma, Jun; Yu, Hua-Rong; Li, Kai; Ding, An; Li, Gui-Bai

    2013-02-01

    In order to quantify the activity of heterotrophic microorganism in membrane bioreactor (MBR) for drinking water treatment, biomass respiration potential (BRP) test and 2,3,5-triphenyl tetrazolium chloride-dehydrogenase activity (TTC-DHA) test were introduced and modified. A sludge concentration ratio of 5:1, incubation time of 2h, an incubation temperature that was close to the real operational temperature, and using a mixture of main AOC components as the substrate were adopted as the optimum parameters for determination of DHA in drinking water MBR. A remarkable consistency among BDOC removal, BRP and DHA for assessing biological performance in different MBRs was achieved. Moreover, a significant correlation between the BRP and DHA results of different MBRs was obtained. However, the TTC-DHA test was expected to be inaccurate for quantifying the biomass activity in membrane adsorption bioreactor (MABR), while the BRP test turned out to be still feasible in that case.

  15. The maltose ABC transporter: action of membrane lipids on the transporter stability, coupling and ATPase activity.

    PubMed

    Bao, Huan; Dalal, Kush; Wang, Victor; Rouiller, Isabelle; Duong, Franck

    2013-08-01

    The coupling between ATP hydrolysis and substrate transport remains a key question in the understanding of ABC-mediated transport. We show using the MalFGK2 complex reconstituted into nanodiscs, that membrane lipids participate directly to the coupling reaction by stabilizing the transporter in a low energy conformation. When surrounded by short acyl chain phospholipids, the transporter is unstable and hydrolyzes large amounts of ATP without inducing maltose. The presence of long acyl chain phospholipids stabilizes the conformational dynamics of the transporter, reduces its ATPase activity and restores dependence on maltose. Membrane lipids therefore play an essential allosteric function, they restrict the transporter ATPase activity to increase coupling to the substrate. In support to the notion, we show that increasing the conformational dynamics of MalFGK2 with mutations in MalF increases the transporter ATPase activity but decreases the maltose transport efficiency.

  16. Cytotoxic bile acids, but not cytoprotective species, inhibit the ordering effect of cholesterol in model membranes at physiologically active concentrations.

    PubMed

    Mello-Vieira, João; Sousa, Tânia; Coutinho, Ana; Fedorov, Aleksander; Lucas, Susana D; Moreira, Rui; Castro, Rui E; Rodrigues, Cecília M P; Prieto, Manuel; Fernandes, Fábio

    2013-09-01

    Submillimolar concentrations of cytotoxic bile acids (BAs) induce cell death via apoptosis. On the other hand, several cytoprotective BAs were shown to prevent apoptosis in the same concentration range. Still, the mechanisms by which BAs trigger these opposite signaling effects remain unclear. This study was aimed to determine if cytotoxic and cytoprotective BAs, at physiologically active concentrations, are able to modulate the biophysical properties of lipid membranes, potentially translating into changes in the apoptotic threshold of cells. Binding of BAs to membranes was assessed through the variation of fluorescence parameters of suitable derivatized BAs. These derivatives partitioned with higher affinity to liquid disordered than to the cholesterol-enriched liquid ordered domains. Unlabeled BAs were also shown to have a superficial location upon interaction with the lipid membrane. Additionally, the interaction of cytotoxic BAs with membranes resulted in membrane expansion, as concluded from FRET data. Moreover, it was shown that cytotoxic BAs were able to significantly disrupt the ordering of the membrane by cholesterol at physiologically active concentrations of the BA, an effect not associated with cholesterol removal. On the other hand, cytoprotective bile acids had no effect on membrane properties. It was concluded that, given the observed effects on membrane rigidity, the apoptotic activity of cytotoxic BAs could be potentially associated with changes in plasma membrane organization (e.g. modulation of lipid domains) or with an increase in mitochondrial membrane affinity for apoptotic proteins.

  17. Membrane-Targeting DCAP Analogues with Broad-Spectrum Antibiotic Activity against Pathogenic Bacteria

    PubMed Central

    2015-01-01

    We performed a structure–activity relationship study of 2-((3-(3,6-dichloro-9H-carbazol-9-yl)-2-hydroxypropyl)amino)-2-(hydroxymethyl)propane-1,3-diol (DCAP), which is an antibacterial agent that disrupts the membrane potential and permeability of bacteria. The stereochemistry of DCAP had no effect on the biological activity of DCAP. The aromaticity and electronegativity of the chlorine-substituted carbazole was required for activity, suggesting that its planar and dipolar characteristics orient DCAP in membranes. Increasing the hydrophobicity of the tail region of DCAP enhanced its antibiotic activity. Two DCAP analogues displayed promising antibacterial activity against the BSL-3 pathogens Bacillus anthracis and Francisella tularensis. Codosing DCAP analogues with ampicillin or kanamycin increased their potency. These studies demonstrate that DCAP and its analogues may be a promising scaffold for developing chemotherapeutic agents that bind to bacterial membranes and kill strains of slow-growing or dormant bacteria that cause persistent infections. PMID:25941556

  18. Shape-dependent bactericidal activity of copper oxide nanoparticle mediated by DNA and membrane damage

    SciTech Connect

    Laha, Dipranjan; Pramanik, Arindam; Laskar, Aparna; Jana, Madhurya; Pramanik, Panchanan; Karmakar, Parimal

    2014-11-15

    Highlights: • Spherical and sheet shaped copper oxide nanoparticles were synthesized. • Physical characterizations of these nanoparticles were done by TEM, DLS, XRD, FTIR. • They showed shape dependent antibacterial activity on different bacterial strain. • They induced both membrane damage and ROS mediated DNA damage in bacteria. - Abstract: In this work, we synthesized spherical and sheet shaped copper oxide nanoparticles and their physical characterizations were done by the X-ray diffraction, fourier transform infrared spectroscopy, transmission electron microscopy and dynamic light scattering. The antibacterial activity of these nanoparticles was determined on both gram positive and gram negative bacterial. Spherical shaped copper oxide nanoparticles showed more antibacterial property on gram positive bacteria where as sheet shaped copper oxide nanoparticles are more active on gram negative bacteria. We also demonstrated that copper oxide nanoparticles produced reactive oxygen species in both gram negative and gram positive bacteria. Furthermore, they induced membrane damage as determined by atomic force microscopy and scanning electron microscopy. Thus production of and membrane damage are major mechanisms of the bactericidal activity of these copper oxide nanoparticles. Finally it was concluded that antibacterial activity of nanoparticles depend on physicochemical properties of copper oxide nanoparticles and bacterial strain.

  19. Phospholipase D activity couples plasma membrane endocytosis with retromer dependent recycling

    PubMed Central

    Thakur, Rajan; Panda, Aniruddha; Coessens, Elise; Raj, Nikita; Yadav, Shweta; Balakrishnan, Sruthi; Zhang, Qifeng; Georgiev, Plamen; Basak, Bishal; Pasricha, Renu; Wakelam, Michael JO; Ktistakis, Nicholas T; Raghu, Padinjat

    2016-01-01

    During illumination, the light-sensitive plasma membrane (rhabdomere) of Drosophila photoreceptors undergoes turnover with consequent changes in size and composition. However, the mechanism by which illumination is coupled to rhabdomere turnover remains unclear. We find that photoreceptors contain a light-dependent phospholipase D (PLD) activity. During illumination, loss of PLD resulted in an enhanced reduction in rhabdomere size, accumulation of Rab7 positive, rhodopsin1-containing vesicles (RLVs) in the cell body and reduced rhodopsin protein. These phenotypes were associated with reduced levels of phosphatidic acid, the product of PLD activity and were rescued by reconstitution with catalytically active PLD. In wild-type photoreceptors, during illumination, enhanced PLD activity was sufficient to clear RLVs from the cell body by a process dependent on Arf1-GTP levels and retromer complex function. Thus, during illumination, PLD activity couples endocytosis of RLVs with their recycling to the plasma membrane thus maintaining plasma membrane size and composition. DOI: http://dx.doi.org/10.7554/eLife.18515.001 PMID:27848911

  20. Photodynamic activity of the boronated chlorin e6 amide in artificial and cellular membranes.

    PubMed

    Antonenko, Yuri N; Kotova, Elena A; Omarova, Elena O; Rokitskaya, Tatyana I; Ol'shevskaya, Valentina A; Kalinin, Valery N; Nikitina, Roza G; Osipchuk, Julia S; Kaplan, Mikhail A; Ramonova, Alla A; Moisenovich, Mikhail M; Agapov, Igor I; Kirpichnikov, Mikhail P

    2014-03-01

    Photodynamic tumor-destroying activity of the boronated chlorin e6 derivative BACE (chlorin e6 13(1)-N-{2-[N-(1-carba-closo-dodecaboran-1-yl)methyl]aminoethyl}amide-15(2), 17(3)-dimethyl ester), previously described in Moisenovich et al. (2010) PLoS ONE 5(9) e12717, was shown here to be enormously higher than that of unsubstituted chlorin e6, being supported by the data on much higher photocytotoxicity of BACE in M-1 sarcoma cell culture. To validate membrane damaging effect as the basis of the enhanced tumoricidal activity, BACE was compared with unsubstituted chlorin e6 in the potency to photosensitize dye leakage from liposomes, transbilayer lipid flip-flop, inactivation of gramicidin A ionic channels in planar lipid membranes and erythrocyte hemolysis. In all the models comprising artificial and cellular membranes, the photodynamic effect of BACE exceeded that of chlorin e6. BACE substantially differed from chlorin e6 in the affinity to liposomes and erythrocytes, as monitored by fluorescence spectroscopy, flow cytometry and centrifugation. The results support the key role of membrane binding in the photodynamic effect of the boronated chlorin e6 amide.

  1. Removal of diatrizoate with catalytically active membranes incorporating microbially produced palladium nanoparticles.

    PubMed

    Hennebel, Tom; De Corte, Simon; Vanhaecke, Lynn; Vanherck, Katrien; Forrez, Ilse; De Gusseme, Bart; Verhagen, Pieter; Verbeken, Kim; Van der Bruggen, Bart; Vankelecom, Ivo; Boon, Nico; Verstraete, Willy

    2010-03-01

    There is an increasing concern about the fate of iodinated contrast media (ICM) in the environment. Limited removal efficiencies of currently applied techniques such as advanced oxidation processes require more performant strategies. The aim of this study was to establish an innovative degradation process for diatrizoate, a highly recalcitrant ICM, by using biogenic Pd nanoparticles as free suspension or immobilized in polyvinylidene fluoride (PVDF) and polysulfone (PSf) membranes. As measured by HPLC-UV, the removal of 20mg L(-1) diatrizoate by a 10mg L(-1) Pd suspension was completed after 4h at a pH of 10. LC-MS analysis provided evidence for the sequential hydrodeiodination of diatrizoate. Pd did not lose its activity after incorporation in the PVDF and PSf matrix and the highest activity (k(cat)=30.0+/-0.4h(-1) L g(-1) Pd) was obtained with a casting solution of 10% PSf and 500mg L(-1) Pd. Subsequently, water containing 20mg L(-1) diatrizoate was treated in a membrane contactor, in which the water was supplied at one side of the membrane while hydrogen was provided at the other side. In a fed batch configuration, a removal efficiency of 77% after a time period of 48h was obtained. This work showed that membrane contactors with encapsulated biogenic nanoparticles can be instrumental for treatment of water contaminated with diatrizoate.

  2. Thyroid hormones increase Na -H exchange activity in renal brush border membranes

    SciTech Connect

    Kinsella, J.; Sacktor, B.

    1985-06-01

    Na -H exchange activity, i.e., amiloride-sensitive Na and H flux, in renal proximal tubule brush border (luminal) membrane vesicles was increased in the hyperthyroid rat and decreased in the hypothyroid rat, relative to the euthyroid animal. A positive correlation was found between Na -H exchange activity and serum concentrations of thyroxine (T4) and triiodothyronine (T3). The thyroid status of the animal did not alter amiloride-insensitive Na uptake. The rate of passive pH gradient dissipation was higher in membrane vesicles from hyperthyroid rats compared to the rate in vesicles from hypothyroid animals, a result which would tend to limit the increase in Na uptake in vesicles from hyperthyroid animals. Na -dependent phosphate uptake was increased in membrane vesicles from hyperthyroid rats; Na -dependent D-glucose and L-proline uptakes were not changed by the thyroid status of the animal. The effect of thyroid hormones in increasing the uptake of Na in the brush border membrane vesicle is consistent with the action of the hormones in enhancing renal Na reabsorption.

  3. Respiratory Membrane endo-Hydrogenase Activity in the Microaerophile Azorhizobium caulinodans Is Bidirectional

    PubMed Central

    Sprecher, Brittany N.; Gittings, Margo E.; Ludwig, Robert A.

    2012-01-01

    Background The microaerophilic bacterium Azorhizobium caulinodans, when fixing N2 both in pure cultures held at 20 µM dissolved O2 tension and as endosymbiont of Sesbania rostrata legume nodules, employs a novel, respiratory-membrane endo-hydrogenase to oxidize and recycle endogenous H2 produced by soluble Mo-dinitrogenase activity at the expense of O2. Methods and Findings From a bioinformatic analysis, this endo-hydrogenase is a core (6 subunit) version of (14 subunit) NADH:ubiquinone oxidoreductase (respiratory complex I). In pure A. caulinodans liquid cultures, when O2 levels are lowered to <1 µM dissolved O2 tension (true microaerobic physiology), in vivo endo-hydrogenase activity reverses and continuously evolves H2 at high rates. In essence, H+ ions then supplement scarce O2 as respiratory-membrane electron acceptor. Paradoxically, from thermodynamic considerations, such hydrogenic respiratory-membrane electron transfer need largely uncouple oxidative phosphorylation, required for growth of non-phototrophic aerobic bacteria, A. caulinodans included. Conclusions A. caulinodans in vivo endo-hydrogenase catalytic activity is bidirectional. To our knowledge, this study is the first demonstration of hydrogenic respiratory-membrane electron transfer among aerobic (non-fermentative) bacteria. When compared with O2 tolerant hydrogenases in other organisms, A. caulinodans in vivo endo-hydrogenase mediated H2 production rates (50,000 pmol 109·cells−1 min−1) are at least one-thousandfold higher. Conceivably, A. caulinodans respiratory-membrane hydrogenesis might initiate H2 crossfeeding among spatially organized bacterial populations whose individual cells adopt distinct metabolic states in response to variant O2 availability. Such organized, physiologically heterogeneous cell populations might benefit from augmented energy transduction and growth rates of the populations, considered as a whole. PMID:22662125

  4. Comparative Transport Activity of Intact Cells, Membrane Vesicles, and Mesosomes of Bacillus licheniformis

    PubMed Central

    MacLeod, Robert A.; Thurman, Paul; Rogers, H. J.

    1973-01-01

    Sodium ion was shown to stimulate strongly the transport of l-glutamic acid into cells of Bacillus licheniformis 6346 His−. Lithium ion had a slight capacity to replace Na+ in this capacity, but K+ was without effect. Three of five amino acids tested. l-glutamic acid, l-aspartic acid, and l-alanine, were concentrated against a gradient in the cells. Intracellular pools of these amino acids were extractable with 5% trichloroacetic acid. Pools of l-histidine and l-lysine could not be detected. No evidence of active transport of lysine into cells could be detected, and histidine was taken up in the absence of chloramphenicol but not in its presence. The uptake of glutamic acid by membrane vesicle preparations was strongly stimulated by reduced nicotinamide adenine dinucleotide (NADH) and to a lesser extent by succinate. The presence of phenazine methosulfate increased uptake in the presence of succinate. Either l- or d-lactate and adenosine triphosphate were without effect. None of these compounds stimulated the uptake of glutamic acid by mesosomes, although some mesosome preparations contained separable membrane which was very active. NADH strongly stimulated the uptake of aspartic acid and alanine by membrane vesicles but had only a slight effect on the uptake of histidine and lysine. No evidence of active transport of any of the amino acids into mesosomes could be detected either in the presence or absence of NADH. NADH stimulation of the uptake of glutamic acid by membrane vesicles was destroyed by exposure to light of 360 nm; this inactivation was reversible by vitamin K2(5) or K2(10). Sodium ion stimulated transport of glutamic acid by membrane vesicles. PMID:4347247

  5. Transferred nuclear Overhauser effect analyses of membrane-bound enkephalin analogues by sup 1 H nuclear magnetic resonance: Correlation between activities and membrane-bound conformations

    SciTech Connect

    Milon, Alain; Miyazawa, Tatsuo; Higashijima, Tsutomu )

    1990-01-09

    Leu-enkephalin, (D-Ala{sup 2})Leu-enkephalin, and (D-Ala{sup 2})Leu-enkephalinamide (agonists) and (L-Ala{sup 2})Leu-enkephalin (inactive analogue) bind to lipid bilayer consisting of phosphatidylcholine and phosphatidylserine. The conformations that these compounds assume, once bound to perdeuterated phospholipid bilayer, have been shown to be unique, as shown by the transferred nuclear Overhauser effect (TRNOE) of {sup 1}H NMR spectroscopy. In addition, their location in the bilayer was analyzed by TRNOE in the presence of spin-labeled phospholipids. These analyses showed a clear relationship between the activity and the peptide-membrane interaction. The three active peptides, when bound to membranes, adopt the same conformation, characterized by a type II{prime} {beta}-turn around Gly{sup 3}-Phe and a {gamma}-turn around Gly{sup 2} (or D-Ala{sup 2}). The inactive analogue, (L-Ala{sup 2})Leu-enkephalin, displayed a completely different TRNOE pattern corresponding to a different conformation in the membrane-bound state. The tyrosine residue of the active compounds is not inserted into the interior of membrane, but it is inserted into the bilayer for the L-Ala{sup 2} analogue. According to these results, (L-Ala{sup 2})Leu-enkephalin may be explained to be inactive because the mode of binding to the membranes is different from that of active compounds.

  6. pH-dependent association of carbonic anhydrase (CA) with gastric light microsomal membranes isolated from bovine abomasum. Partial characterization of membrane-associated activity.

    PubMed

    López Mañanes, A A; Daleo, G R; Vega, F V

    1993-05-01

    1. The effect of pH on the association of carbonic anhydrase (CA) with bovine gastric light microsomal membranes (LMMs) was investigated (a) by washing LMMs containing CA activity with solutions of different pHs; (b) by studying the adsorption at various pHs of soluble bovine erythrocyte CA to washed gastric LMMs. In both cases, the association of CA with gastric LMMs was dependent on pH, being lower at neutral or alkaline pH. 2. The amount of soluble CA associated with gastric LMMs at pHs 8.0 and 9.0 was reduced when 140 mM K+/10 mM Na+ was added to the incubation medium. 3. Two sources of CA activity in bovine gastric LMMs were assumed: a loosely- and a firmly-membrane-associated activity. Both CA activities were dose-dependently inhibited by acetazolamide (I50: 3.6 x 10(-9) and 8.4 x 10(-9) M, respectively) and by chloride, acetate, iodide, bromide and nitrate at 100 mM. Firmly-membrane-associated activity appeared to be less sensitive to inhibition by acetazolamide, chloride and iodide. 4. Both activities exhibited different behavior and stability following treatment with alkaline Triton X-100. 5. The possible importance of a membrane-associated CA activity in gastric LMMs related to gastric acid secretion is discussed.

  7. Reversed-phase liquid chromatographic retention and membrane activity relationships of local anesthetics.

    PubMed

    Tsuchiya, Hironori; Mizogami, Maki; Takakura, Ko

    2005-05-06

    The chromatographic retention and membrane activity relationships of local anesthetics were studied to address the possible mechanisms for structure specificity and inflammation-associated decrease of their effects. Five representative drugs (3 mM for each) were reacted with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine liposomes in 25 mM potassium phosphate buffer (pH 5.9-7.9, containing 100 mM NaCl and 0.1 mM EDTA) for 10 min at 37 degrees C and the membrane fluidity changes were analyzed by measuring fluorescence polarization with 1,6-diphenyl-1,3,5-hexatriene. Their capacity factors were determined on octadecyl-, octyl- and phenyl-bonded silica columns with a mobile phase consisting of 25 mM potassium phosphate buffer (pH 5.9-7.9, containing 100 mM NaCl and 0.1 mM EDTA)-methanol (30:70, v/v) at a flow rate of 1.0 ml/min and at a column temperature of 37 degrees C and diode-array detection. Mepivacaine, prilocaine, lidocaine, ropivacaine and bupivacaine fluidized membranes in increasing order of intensity, which agreed with their clinical potency. The relative degree of membrane fluidization correlated with that of retention on an octadecyl stationary phase more significantly than the other phases. Both membrane-fluidizing effects and capacity factors decreased by lowering the reaction and mobile phase pH, being consistent with the hypothesis that anesthetic potency is reduced in inflammation because of tissue acidity. Reversed-phase liquid chromatography appears to be useful for estimating the structure-specific and pH-dependent membrane-fluidizing effects of local anesthetics.

  8. Cationic Membrane Peptides: Atomic-Level Insight of Structure-Activity Relationships from Solid-State NMR

    PubMed Central

    Su, Yongchao; Li, Shenhui; Hong, Mei

    2012-01-01

    Many membrane-active peptides, such as cationic cell-penetrating peptides (CPPs) and antimicrobial peptides (AMPs), conduct their biological functions by interacting with the cell membrane. The interactions of charged residues with lipids and water facilitate membrane insertion, translocation or disruption of these highly hydrophobic species. In this mini-review we will summarize high-resolution structural and dynamic findings towards the understanding of the structure-activity relationship of lipid membrane-bound CPPs and AMPs, as examples of the current development of solid-state NMR (SSNMR) techniques for studying membrane peptides. We will present the most recent atomic-resolution structure of the guanidinium-phosphate complex, as constrained from experimentally measured site-specific distances. These SSNMR results will be valuable specifically for understanding the intracellular translocation pathway of CPPs and antimicrobial mechanism of AMPs, and more generally broaden our insight into how cationic macromolecules interact with and cross the lipid membrane. PMID:23108593

  9. Preparation of the superhydrophobic nano-hybrid membrane containing carbon nanotube based on chitosan and its antibacterial activity.

    PubMed

    Song, Kaili; Gao, Aiqin; Cheng, Xi; Xie, Kongliang

    2015-10-05

    The functional nano-hybrid surface containing multi-walled carbon nanotubes (MWCNT) on chitosan incorporated with the cationic chitosan (C-CS), MWCNTs and silicon couple agent (KH-560) was designed and prepared. The nano-hybrid membranes (NHM) containing MWCNTs were modified by perfluorooctanesulfonyl fluoride (PFOSF). The superhydrophobic multi-functional membranes with biological activity and superhydrophobic surface were obtained. The incorporated MWCNTs improved the roughness of the nano-hybrid membranes. The perfluorinated end groups of the nano-hybrid membrane surface provided low energy surface. The antibacterial activity, surface superhydrophobicity and mechanical property of the perfluorinated nano-hybrid membranes (PFNM) were discussed. Their morphological structures and surface ingredients were characterized by energy dispersive X-ray spectrometer (SEM-EDX). The PFNMs had excellent antibacterial property and superhydrophobicity. The novel nano-hybrid membranes with excellent antibacterial, superhydrophbic, and mechanical properties have potential applications in the food engineering, bioengineering fields and medical materials.

  10. The plasma membrane shuttling of CAPRI is related to regulation of mast cell activation

    SciTech Connect

    Nakamura, Rika; Furuno, Tadahide; Nakanishi, Mamoru . E-mail: mamoru@dpc.agu.ac.jp

    2006-08-18

    The Ca{sup 2+}-promoted Ras inactivator (CAPRI), a Ras GTPase-activating protein, is involved in the inactivation of mitogen-activated protein kinase pathway. However, a precise role of CAPRI in immune responses is still unknown. Here we showed that overexpression of CAPRI suppresses antigen-induced degranulation and cytokine production in mast cells (RBL cells). Antigen elicited the translocation of CAPRI to the plasma membrane from the cytoplasm, which was concomitant with the increase in the intracellular Ca{sup 2+} concentration. The nuclear import of extracellular signal-regulated kinase 2 (ERK2) occurred after the re-localization of CAPRI to the cytoplasm in the mast cells, suggesting that the early phase of ERK2 activation is eliminated. A mutant of GAP-related domain, CAPRI(R472S), showed a feeble translocation to the plasma membrane but did not affect the degranulation, ERK2 activation, and cytokine production. The results suggested that the translocation of CAPRI to the plasma membranes regulates crucially cellular responses in mast cells.

  11. Flow-induced activation of TRPV5 and TRPV6 channels stimulates Ca(2+)-activated K(+) channel causing membrane hyperpolarization.

    PubMed

    Cha, Seung-Kuy; Kim, Ji-Hee; Huang, Chou-Long

    2013-12-01

    TRPV5 and TRPV6 channels are expressed in distal renal tubules and play important roles in the transcellular Ca(2+) reabsorption in kidney. They are regulated by multiple intracellular factors including protein kinases A and C, membrane phospholipid PIP2, protons, and divalent ions Ca(2+) and Mg(2+). Here, we report that fluid flow that generates shear force within the physiological range of distal tubular fluid flow activated TRPV5 and TRPV6 channels expressed in HEK cells. Flow-induced activation of channel activity was reversible and did not desensitize over 2min. Fluid flow stimulated TRPV5 and 6-mediated Ca(2+) entry and increased intracellular Ca(2+) concentration. N-glycosylation-deficient TRPV5 channel was relatively insensitive to fluid flow. In cells coexpressing TRPV5 (or TRPV6) and Slo1-encoded maxi-K channels, fluid flow induced membrane hyperpolarization, which could be prevented by the maxi-K blocker iberiotoxin or TRPV5 and 6 blocker La(3+). In contrast, fluid flow did not cause membrane hyperpolarization in cells coexpressing ROMK1 and TRPV5 or 6 channel. These results reveal a new mechanism for the regulation of TRPV5 and TRPV6 channels. Activation of TRPV5 and TRPV6 by fluid flow may play a role in the regulation of flow-stimulated K(+) secretion via maxi-K channels in distal renal tubules and in the mechanism of pathogenesis of thiazide-induced hypocalciuria.

  12. Flow-Induced Activation of TRPV5 and TRPV6 Channel Stimulates Ca2+-Activated K+ Channel Causing Membrane Hyperpolarization

    PubMed Central

    Cha, Seung-Kuy; Kim, Ji-Hee; Huang, Chou-Long

    2014-01-01

    TRPV5 and TRPV6 channels are expressed in distal renal tubules and play important roles in the transcellular Ca2+ reabsorption in kidney. They are regulated by multiple intracellular factors including protein kinase A and C, membrane phospholipid PIP2, protons, and divalent ions Ca2+ and Mg2+. Here, we report that fluid flow that generates shear force within the physiological range of distal tubular fluid flow activated TRPV5 and TRPV6 channels expressed in HEK cells. Flow-induced activation of channel activity was reversible and did not desensitize over 2 minutes. Fluid flow stimulated TRPV5 and 6-mediated Ca2+ entry and increased intracellular Ca2+ concentration. N-glycosylation-deficient TRPV5 channel was relatively insensitive to fluid flow. In cells coexpressing TRPV5 (or TRPV6) and Slo1-encoded maxi-K channels, fluid flow induced membrane hyperpolarization, which could be prevented by the maxi-K blocker iberiotoxin or TRPV5 and 6 blocker La3+. In contrast, fluid flow did not cause membrane hyperpolarization in cells coexpressing ROMK1 and TRPV5 or 6 channels. These results reveal a new mechanism for regulation of TRPV5 and TRPV6 channels. Activation of TRPV5 and TRPV6 by fluid flow may play a role in the regulation of flow-stimulated K+ secretion via maxi-K channels in distal renal tubules and in the mechanism of pathogenesis of thiazide-induced hypocalciuria. PMID:24001793

  13. Activation of the basolateral membrane Cl− conductance essential for electrogenic K+ secretion suppresses electrogenic Cl− secretion

    PubMed Central

    He, Quanhua; Halm, Susan T.; Zhang, Jin; Halm, Dan R.

    2010-01-01

    Adrenaline activates transient Cl−-secretion and sustained K+-secretion across isolated distal colonic mucosa of guinea pig. The Ca++-activated Cl− channel inhibitor CaCCinh-A01 [30μM] significantly reduced electrogenic K+-secretion, detected as short-circuit current (Isc). This inhibition supported the cell model for K+-secretion in which basolateral membrane Cl− channels provide an exit pathway for Cl− entering the cell via Na+/K+/2Cl−-cotransporters. CaCCinh-A01 inhibited both Isc and transepithelial conductance in a concentration dependent manner, IC50 = 6.3μM. GlyH-101, another Cl− channel inhibitor, also reduced sustained adrenaline-activated Isc (IC50 = 9.4μM). Adrenaline activated whole-cell Cl− current in isolated intact colonic crypts, confirmed by ion substitution. This adrenaline-activated whole-cell Cl− current also was inhibited by CaCCinh-A01 or GlyH-101. In contrast to K+-secretion, CaCCinh-A01 augmented the electrogenic Cl−-secretion activated by adrenaline as well as that activated by PGE2. Synergistic Cl−-secretion activated by cholinergic/PGE2 stimulation was insensitive to CaCCinh-A01. Colonic expression of the Ca++-activated Cl− channel protein Tmem16A was supported by RT-PCR detection of Tmem16A-mRNA, by immuno-blot with a Tmem16A-antibody, and by immuno-fluorescence detection in lateral membranes of epithelial cells. Alternative splices of Tmem16A were detected for exons that are involved in channel activation. Inhibition of K+-secretion and augmentation of Cl−-secretion by CaCCinh-A01 supports a common colonic cell model for these two ion secretory processes, such that activation of basolateral membrane Cl− channels contributes to the production of electrogenic K+-secretion and limits the rate of Cl−-secretion. Maximal physiological Cl−-secretion occurs only for synergistic activation mechanisms that close these basolateral membrane Cl− channels. PMID:21169331

  14. Impact of humic acid fouling on membrane performance and transport of pharmaceutically active compounds in forward osmosis.

    PubMed

    Xie, Ming; Nghiem, Long D; Price, William E; Elimelech, Menachem

    2013-09-01

    The impact of humic acid fouling on the membrane transport of two pharmaceutically active compounds (PhACs) - namely carbamazepine and sulfamethoxazole - in forward osmosis (FO) was investigated. Deposition of humic acid onto the membrane surface was promoted by the complexation with calcium ions in the feed solution and the increase in ionic strength at the membrane surface due to the reverse transport of NaCl draw solute. The increase in the humic acid deposition on the membrane surface led to a substantial decrease in the membrane salt (NaCl) permeability coefficient but did not result in a significant decrease in the membrane pure water permeability coefficient. As the deposition of humic acid increased, the permeation of carbamazepine and sulfamethoxazole decreased, which correlated well with the decrease in the membrane salt (NaCl) permeability coefficient. It is hypothesized that the hydrated humic acid fouling layer hindered solute diffusion through the membrane pore and enhanced solute rejection by steric hindrance, but not the permeation of water molecules. The membrane water and salt (NaCl) permeability coefficients were fully restored by physical cleaning of the membrane, suggesting that humic acid did not penetrate into the membrane pores.

  15. The MICOS component Mic60 displays a conserved membrane-bending activity that is necessary for normal cristae morphology.

    PubMed

    Tarasenko, Daryna; Barbot, Mariam; Jans, Daniel C; Kroppen, Benjamin; Sadowski, Boguslawa; Heim, Gudrun; Möbius, Wiebke; Jakobs, Stefan; Meinecke, Michael

    2017-04-03

    The inner membrane (IM) of mitochondria displays an intricate, highly folded architecture and can be divided into two domains: the inner boundary membrane adjacent to the outer membrane and invaginations toward the matrix, called cristae. Both domains are connected by narrow, tubular membrane segments called cristae junctions (CJs). The formation and maintenance of CJs is of vital importance for the organization of the mitochondrial IM and for mitochondrial and cellular physiology. The multisubunit mitochondrial contact site and cristae organizing system (MICOS) was found to be a major factor in CJ formation. In this study, we show that the MICOS core component Mic60 actively bends membranes and, when inserted into prokaryotic membranes, induces the formation of cristae-like plasma membrane invaginations. The intermembrane space domain of Mic60 has a lipid-binding capacity and induces membrane curvature even in the absence of the transmembrane helix. Mic60 homologues from α-proteobacteria display the same membrane deforming activity and are able to partially overcome the deletion of Mic60 in eukaryotic cells. Our results show that membrane bending by Mic60 is an ancient mechanism, important for cristae formation, and had already evolved before α-proteobacteria developed into mitochondria.

  16. Role of membrane cholesterol and lipid peroxidation in regulating the Na+/K+-ATPase activity in schizophrenia

    PubMed Central

    Roy, Suparna; Dasgupta, Anindya; Banerjee, Ushasi; Chowdhury, Piali; Mukhopadhyay, Ashis; Saha, Gautam; Singh, Omprakash

    2016-01-01

    Background: Na+/K+-ATPase (NKA) activity is compromised in several neuropsychiatric disorders. Oxidative stress and membrane lipid composition play important roles in regulating NKA activity. Aims: The present study was undertaken to evaluate the effects of oxidative stress-induced membrane lipid damage and membrane cholesterol composition on NKA pump activity in schizophrenia. Settings and Design: It was a hospital-based, cross-sectional, observational study in 49 cases and 51 controls for 1 year. Materials and Methods: NKA pump activity in red blood cell membrane, serum levels of thiobarbituric acid reactive substances (TBARS), protein carbonyl (PC) adducts, and cholesterol were measured by standard spectrophotometric techniques in newly diagnosed schizophrenia patients by Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision criteria. Membrane cholesterol was analyzed by chloroform and isopropanol extraction followed by measuring the cholesterol concentration by spectrophotometric technique. Statistical Analysis and Results: Mean values for NKA pump activity, membrane cholesterol level, and serum cholesterol levels were significantly lower in the case group (P < 0.001). The activity of NKA pump was found to be directly correlated to membrane cholesterol level rather than with the serum cholesterol values. Although the NKA pump activity showed inverse relationship with the serum values of TBARS and PC products both, on multiple linear regression analysis, it was found to be significantly positively dependent on the membrane cholesterol (β = 0.268, P = 0.01) and negatively dependent on the serum TBARS (β = −0.63, P < 0.001) levels only. Conclusion: Reduced membrane cholesterol and oxidative stress-induced damage to membrane lipids play crucial roles in decreasing the NKA activity in schizophrenia. Hence, for a better prognosis and treatment, measures are required to maintain optimum levels of cholesterol in neuronal tissues along

  17. Auxin-activated NADH oxidase activity of soybean plasma membranes is distinct from the constitutive plasma membrane NADH oxidase and exhibits prion-like properties

    NASA Technical Reports Server (NTRS)

    Morre, D. James; Morre, Dorothy M.; Ternes, Philipp

    2003-01-01

    The hormone-stimulated and growth-related cell surface hydroquinone (NADH) oxidase activity of etiolated hypocotyls of soybeans oscillates with a period of about 24 min or 60 times per 24-h day. Plasma membranes of soybean hypocotyls contain two such NADH oxidase activities that have been resolved by purification on concanavalin A columns. One in the apparent molecular weight range of 14-17 kDa is stimulated by the auxin herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). The other is larger and unaffected by 2,4-D. The 2,4-D-stimulated activity absolutely requires 2,4-D for activity and exhibits a period length of about 24 min. Also exhibiting 24-min oscillations is the rate of cell enlargement induced by the addition of 2,4-D or the natural auxin indole-3-acetic acid (IAA). Immediately following 2,4-D or IAA addition, a very complex pattern of oscillations is frequently observed. However, after several hours a dominant 24-min period emerges at the expense of the constitutive activity. A recruitment process analogous to that exhibited by prions is postulated to explain this behavior.

  18. Neural conversion of ES cells by an inductive activity on human amniotic membrane matrix

    PubMed Central

    Ueno, Morio; Matsumura, Michiru; Watanabe, Kiichi; Nakamura, Takahiro; Osakada, Fumitaka; Takahashi, Masayo; Kawasaki, Hiroshi; Kinoshita, Shigeru; Sasai, Yoshiki

    2006-01-01

    Here we report a human-derived material with potent inductive activity that selectively converts ES cells into neural tissues. Both mouse and human ES cells efficiently differentiate into neural precursors when cultured on the matrix components of the human amniotic membrane in serum-free medium [amniotic membrane matrix-based ES cell differentiation (AMED)]. AMED-induced neural tissues have regional characteristics (brainstem) similar to those induced by coculture with mouse PA6 stromal cells [a common method called stromal cell-derived inducing activity (SDIA) culture]. Like the SDIA culture, the AMED system is applicable to the in vitro generation of various CNS tissues, including dopaminergic neurons, motor neurons, and retinal pigment epithelium. In contrast to the SDIA method, which uses animal cells, the AMED culture uses a noncellular inductive material derived from an easily available human tissue; therefore, AMED should provide a more suitable and versatile system for generating a variety of neural tissues for clinical applications. PMID:16766664

  19. A Rapid and Quantitative Flow Cytometry Method for the Analysis of Membrane Disruptive Antimicrobial Activity

    PubMed Central

    O’Brien-Simpson, Neil M.; Pantarat, Namfon; Attard, Troy J.; Walsh, Katrina A.; Reynolds, Eric C.

    2016-01-01

    We describe a microbial flow cytometry method that quantifies within 3 hours antimicrobial peptide (AMP) activity, termed Minimum Membrane Disruptive Concentration (MDC). Increasing peptide concentration positively correlates with the extent of bacterial membrane disruption and the calculated MDC is equivalent to its MBC. The activity of AMPs representing three different membranolytic modes of action could be determined for a range of Gram positive and negative bacteria, including the ESKAPE pathogens, E. coli and MRSA. By using the MDC50 concentration of the parent AMP, the method provides high-throughput, quantitative screening of AMP analogues. A unique feature of the MDC assay is that it directly measures peptide/bacteria interactions and lysed cell numbers rather than bacteria survival as with MIC and MBC assays. With the threat of multi-drug resistant bacteria, this high-throughput MDC assay has the potential to aid in the development of novel antimicrobials that target bacteria with improved efficacy. PMID:26986223

  20. Beyond apoptosis: the mechanism and function of phosphatidylserine asymmetry in the membrane of activating mast cells.

    PubMed

    Rysavy, Noel M; Shimoda, Lori M N; Dixon, Alyssa M; Speck, Mark; Stokes, Alexander J; Turner, Helen; Umemoto, Eric Y

    2014-01-01

    Loss of plasma membrane asymmetry is a hallmark of apoptosis, but lipid bilayer asymmetry and loss of asymmetry can contribute to numerous cellular functions and responses that are independent of programmed cell death. Exofacial exposure of phosphatidylserine occurs in lymphocytes and mast cells after antigenic stimulation and in the absence of apoptosis, suggesting that there is a functional requirement for phosphatidylserine exposure in immunocytes. In this review we examine current ideas as to the nature of this functional role in mast cell activation. Mechanistically, there is controversy as to the candidate proteins responsible for phosphatidylserine translocation from the internal to external leaflet, and here we review the candidacies of mast cell PLSCR1 and TMEM16F. Finally we examine the potential relationship between functionally important mast cell membrane perturbations and phosphatidylserine exposure during activation.

  1. Beyond apoptosis: The mechanism and function of phosphatidylserine asymmetry in the membrane of activating mast cells

    PubMed Central

    Rysavy, Noel M.; Shimoda, Lori M. N.; Dixon, Alyssa M.; Speck, Mark; Stokes, Alexander J.; Turner, Helen; Umemoto, Eric Y.

    2014-01-01

    Loss of plasma membrane asymmetry is a hallmark of apoptosis, but lipid bilayer asymmetry and loss of asymmetry can contribute to numerous cellular functions and responses that are independent of programmed cell death. Exofacial exposure of phosphatidylserine occurs in lymphocytes and mast cells after antigenic stimulation and in the absence of apoptosis, suggesting that there is a functional requirement for phosphatidylserine exposure in immunocytes. In this review we examine current ideas as to the nature of this functional role in mast cell activation. Mechanistically, there is controversy as to the candidate proteins responsible for phosphatidylserine translocation from the internal to external leaflet, and here we review the candidacies of mast cell PLSCR1 and TMEM16F. Finally we examine the potential relationship between functionally important mast cell membrane perturbations and phosphatidylserine exposure during activation. PMID:25759911

  2. Low temperature alters plasma membrane lipid composition and ATPase activity of pineapple fruit during blackheart development.

    PubMed

    Zhou, Yuchan; Pan, Xiaoping; Qu, Hongxia; Underhill, Steven J R

    2014-02-01

    Plasma membrane (PM) plays central role in triggering primary responses to chilling injury and sustaining cellular homeostasis. Characterising response of membrane lipids to low temperature can provide important information for identifying early causal factors contributing to chilling injury. To this end, PM lipid composition and ATPase activity were assessed in pineapple fruit (Ananas comosus) in relation to the effect of low temperature on the development of blackheart, a form of chilling injury. Chilling temperature at 10 °C induced blackheart development in concurrence with increase in electrolyte leakage. PM ATPase activity was decreased after 1 week at low temperature, followed by a further decrease after 2 weeks. The enzyme activity was not changed during 25 °C storage. Loss of total PM phospholipids was found during postharvest senescence, but more reduction was shown from storage at 10 °C. Phosphatidylcholine and phosphatidylethanolamine were the predominant PM phospholipid species. Low temperature increased the level of phosphatidic acid but decreased the level of phosphatidylinositol. Both phospholipid species were not changed during storage at 25 °C. Postharvest storage at both temperatures decreased the levels of C18:3 and C16:1, and increased level of C18:1. Low temperature decreased the level of C18:2 and increased the level of C14:0. Exogenous application of phosphatidic acid was found to inhibit the PM ATPase activity of pineapple fruit in vitro. Modification of membrane lipid composition and its effect on the functional property of plasma membrane at low temperature were discussed in correlation with their roles in blackheart development of pineapple fruit.

  3. Sensor-actuator coupled device for active tracheal tube using solid polymer electrolyte membrane

    NASA Astrophysics Data System (ADS)

    Ihara, Tadashi; Nakamura, Taro; Mukai, Toshiharu; Asaka, Kinji

    2007-04-01

    A sensor-actuator coupled device was developed using solid polymer electrolyte membrane (SPM) as an active tracheal tube for ventilator. Active tracheal tube is a novel type of tube for ventilator that removes patient's phlegm automatically upon sensing the narrowing of trachea by phlegm. This type of active tube is extremely useful in clinical settings as currently the sole measure to remove phlegm from patient's tube is to do it manually by a nurse every few hours. As SPM works both as a sensor and an actuator, an effective compact device was developed. SPM based sensor-actuator coupled device was fabricated with modified gold plating method. Prepared SPM was fixed as an array on a plastic pipe of diameter 22 mm and was connected to a ventilator circuit and driven by a ventilator with a volume control ventilation (VCV) mode. SPM was connected both to a sensing unit and an actuation unit. Generated voltage developed by the membrane with the setting of the maximum pressure from 5 cmH IIO to 20 cmH IIO was in order of several hundred μV. SPM sensor demonstrated a biphasic response to the ventilator flow. The sensor data showed nearly linearly proportional voltage development to the intra-tracheal pressure. The sensed signal was filtered and digitized with an A/D converting unit on a PC board. A real time operating program was used to detect the sensed signal that indicates the narrowing of trachea. The program then activated a driving signal to control the actuation of the membrane. The signal was sent to a D/A converting unit. The output of the D/A unit was sent to an amplifier and the galvanostat unit which drives the membrane with constant current regardless of the change in the load. It was demonstrated that the sensor-actuator unit detects the narrowing of trachea within several hundreds milli-seconds and responds by actuating the same membrane with the driving voltage of 3-4 V and driving current of several hundred milli-ampere for each membrane. SPM array

  4. Model Membrane and Cell Studies of Antimicrobial Activity of Melittin Analogues.

    PubMed

    Jamasbi, Elaheh; Mularski, Anna; Separovic, Frances

    2016-01-01

    Melittin is a 26 residue peptide and the major component of bee (Apis mellifera) venom. Although melittin has both anticancer and antimicrobial properties, utilization has been limited due to its high lytic activity against eukaryotic cells. The mechanism of this lytic activity remains unclear but several mechanisms have been proposed, including pore formation or a detergent like mechanism, which result in lysis of cell membranes. Several analogues of melittin have been synthesized to further understand the role of specific residues in its antimicrobial and lytic activity. Melittin analogues that have a proline residue substituted for an alanine, lysine or cysteine have been studied with both model membrane systems and living cells. These studies have revealed that the proline residue plays a critical role in antimicrobial activity and cytotoxicity. Analogues lacking the proline residue and dimers of these analogues displayed decreased cytotoxicity and minimum inhibition concentrations. Several mutant studies have shown that, when key substitutions are made, the resultant peptides have more activity in terms of pore formation than the native melittin. Designing analogues that retain antimicrobial and anticancer activity while minimizing haemolytic activity will be a promising way to utilize melittin as a potential therapeutic agent.

  5. Membrane-pipette interactions underlie delayed voltage activation of mechanosensitive channels in Xenopus oocytes.

    PubMed Central

    Gil, Z; Magleby, K L; Silberberg, S D

    1999-01-01

    To investigate the mechanism for the delayed activation by voltage of the predominant mechanosensitive (MS) channel in Xenopus oocytes, currents were recorded from on-cell and excised patches of membrane with the patch clamp technique and from intact oocytes with the two-electrode voltage clamp technique. MS channels could be activated by stretch in inside-out, on-cell, and outside-out patch configurations, using pipettes formed of either borosilicate or soft glass. In inside-out patches formed with borosilicate glass pipettes, depolarizing voltage steps activated MS channels in a cooperative manner after delays of seconds. This voltage-dependent activation was not observed for outside-out patches. Voltage-dependent activation was also not observed when the borosilicate pipettes were either replaced with soft glass pipettes or coated with soft glass. When depolarizing voltage steps were applied to the whole oocyte with a two-electrode voltage clamp, currents that could be attributed to MS channels were not observed. Yet the same depolarizing steps activated MS channels in on-cell patches formed with borosilicate pipettes on the same oocyte. These observations suggest that the delayed cooperative activation of MS channels by depolarization is not an intrinsic property of the channels, but requires interaction between the membrane and patch pipette. PMID:10354436

  6. Light-activated control of protein channel assembly mediated by membrane mechanics

    NASA Astrophysics Data System (ADS)

    Miller, David M.; Findlay, Heather E.; Ces, Oscar; Templer, Richard H.; Booth, Paula J.

    2016-12-01

    Photochemical processes provide versatile triggers of chemical reactions. Here, we use a photoactivated lipid switch to modulate the folding and assembly of a protein channel within a model biological membrane. In contrast to the information rich field of water-soluble protein folding, there is only a limited understanding of the assembly of proteins that are integral to biological membranes. It is however possible to exploit the foreboding hydrophobic lipid environment and control membrane protein folding via lipid bilayer mechanics. Mechanical properties such as lipid chain lateral pressure influence the insertion and folding of proteins in membranes, with different stages of folding having contrasting sensitivities to the bilayer properties. Studies to date have relied on altering bilayer properties through lipid compositional changes made at equilibrium, and thus can only be made before or after folding. We show that light-activation of photoisomerisable di-(5-[[4-(4-butylphenyl)azo]phenoxy]pentyl)phosphate (4-Azo-5P) lipids influences the folding and assembly of the pentameric bacterial mechanosensitive channel MscL. The use of a photochemical reaction enables the bilayer properties to be altered during folding, which is unprecedented. This mechanical manipulation during folding, allows for optimisation of different stages of the component insertion, folding and assembly steps within the same lipid system. The photochemical approach offers the potential to control channel assembly when generating synthetic devices that exploit the mechanosensitive protein as a nanovalve.

  7. Highly active carbonaceous nanofibers: a versatile scaffold for constructing multifunctional free-standing membranes.

    PubMed

    Liang, Hai-Wei; Zhang, Wen-Jun; Ma, Yi-Ni; Cao, Xiang; Guan, Qing-Fang; Xu, Wei-Ping; Yu, Shu-Hong

    2011-10-25

    Translating the unique characteristics of individual nanoscale components into macroscopic materials such as membranes or sheets still remains a challenge, as the engineering of these structures often compromises their intrinsic properties. Here, we demonstrate that the highly active carbonaceous nanofibers (CNFs), which are prepared through a template-directed hydrothermal carbonization process, can be used as a versatile nanoscale scaffold for constructing macroscopic multifunctional membranes. In order to demonstrate the broad applicability of the CNF scaffold, we fabricate a variety of CNF-based composite nanofibers, including CNFs-Fe(3)O(4), CNFs-TiO(2), CNFs-Ag, and CNFs-Au through various chemical routes. Importantly, all of them inherit unique dimensionality (high aspect ratio) and mechanical properties (flexibility) of the original CNF scaffolds and thus can be assembled into macroscopic free-standing membranes through a simple casting process. We also demonstrate the wide application potentials of these multifunctional composite membranes in magnetic actuation, antibiofouling filtration, and continuous-flow catalysis.

  8. Effect of ozone on the performance of a hybrid ceramic membrane-biological activated carbon process.

    PubMed

    Guo, Jianning; Hu, Jiangyong; Tao, Yi; Zhu, Jia; Zhang, Xihui

    2014-04-01

    Two hybrid processes including ozonation-ceramic membrane-biological activated carbon (BAC) (Process A) and ceramic membrane-BAC (Process B) were compared to treat polluted raw water. The performance of hybrid processes was evaluated with the removal efficiencies of turbidity, ammonia and organic matter. The results indicated that more than 99% of particle count was removed by both hybrid processes and ozonation had no significant effect on its removal. BAC filtration greatly improved the removal of ammonia. Increasing the dissolved oxygen to 30.0 mg/L could lead to a removal of ammonia with concentrations as high as 7.80 mg/L and 8.69 mg/L for Processes A and B, respectively. The average removal efficiencies of total organic carbon and ultraviolet absorbance at 254 nm (UV254, a parameter indicating organic matter with aromatic structure) were 49% and 52% for Process A, 51% and 48% for Process B, respectively. Some organic matter was oxidized by ozone and this resulted in reduced membrane fouling and increased membrane flux by 25%-30%. However, pre-ozonation altered the components of the raw water and affected the microorganisms in the BAC, which may impact the removals of organic matter and nitrite negatively.

  9. Sch proteins are localized on endoplasmic reticulum membranes and are redistributed after tyrosine kinase receptor activation.

    PubMed Central

    Lotti, L V; Lanfrancone, L; Migliaccio, E; Zompetta, C; Pelicci, G; Salcini, A E; Falini, B; Pelicci, P G; Torrisi, M R

    1996-01-01

    The intracellular localization of Shc proteins was analyzed by immunofluorescence and immunoelectron microscopy in normal cells and cells expressing the epidermal growth factor receptor or the EGFR/erbB2 chimera. In unstimulated cells, the immunolabeling was localized in the central perinuclear area of the cell and mostly associated with the cytosolic side of rough endoplasmic reticulum membranes. Upon epidermal growth factor treatment and receptor tyrosine kinase activation, the immunolabeling became peripheral and was found to be associated with the cytosolic surface of the plasma membrane and endocytic structures, such as coated pits and endosomes, and with the peripheral cytosol. Receptor activation in cells expressing phosphorylation-defective mutants of Shc and erbB-2 kinase showed that receptor autophosphorylation, but not Shc phosphorylation, is required for redistribution of Shc proteins. The rough endoplasmic reticulum localization of Shc proteins in unstimulated cells and their massive recruitment to the plasma membrane, endocytic structures, and peripheral cytosol following receptor tyrosine kinase activation could account for multiple putative functions of the adaptor protein. PMID:8628261

  10. Bovine serum albumin with glycated carboxyl groups shows membrane-perturbing activities.

    PubMed

    Yang, Shin-Yi; Chen, Ying-Jung; Kao, Pei-Hsiu; Chang, Long-Sen

    2014-12-15

    The aim of the present study aimed to investigate whether glycated bovine serum albumin (BSA) showed novel activities on the lipid-water interface. Mannosylated BSA (Man-BSA) was prepared by modification of the carboxyl groups with p-aminophenyl α-d-mannopyranoside. In contrast to BSA, Man-BSA notably induced membrane permeability of egg yolk phosphatidylcholine (EYPC)/egg yolk sphingomyelin (EYSM)/cholesterol (Chol) and EYPC/EYSM vesicles. Noticeably, Man-BSA induced the fusion of EYPC/EYSM/Chol vesicles, but not of EYPC/EYSM vesicles. Although BSA and Man-BSA showed similar binding affinity for lipid vesicles, the lipid-bound conformation of Man-BSA was distinct from that of BSA. Moreover, Man-BSA adopted distinct structure upon binding with the EYPC/EYSM/Chol and EYPC/EYSM vesicles. Man-BSA could induce the fusion of EYPC/EYSM/Chol vesicles with K562 and MCF-7 cells, while Man-BSA greatly induced the leakage of Chol-depleted K562 and MCF-7 cells. The modified BSA prepared by conjugating carboxyl groups with p-aminophenyl α-d-glucopyranoside also showed membrane-perturbing activities. Collectively, our data indicate that conjugation of carboxyl groups with monosaccharide generates functional BSA with membrane-perturbing activities on the lipid-water interface.

  11. Effect of N-terminal truncation on antibacterial activity, cytotoxicity and membrane perturbation activity of Cc-CATH3.

    PubMed

    Jittikoon, Jiraphun; Ngamsaithong, Narumon; Pimthon, Jutarat; Vajragupta, Opa

    2015-10-01

    A series of amino-terminal truncated analogues of quail antimicrobial peptide Cc-CATH3(1-29) were created and examined antibacterial activity against Gram-positive bacteria, cytotoxicity against mouse fibroblast cell line, and membrane perturbation activity against various membrane models. Parent peptide Cc-CATH3(1-29) and the first four-residue truncated peptide Cc-CATH3(5-29) were active in all tested experiments. In contrast, the eight- and twelve-residue truncated variants Cc-CATH3(9-29) and Cc-CATH3(13-29) appeared to have lost activities. Cc-CATH3(1-29) and Cc-CATH3(5-29) possessed antibacterial activity with minimum inhibitory concentrations of 2-4 and 1-2 µM, respectively. For cytotoxicity, Cc-CATH3(1-29) and Cc-CATH3(5-29) displayed cytotoxicity with the IC50 values of 9.33 and 4.93 μM, respectively. Cc-CATH3(5-29) induced greater liposome membranes disruption than Cc-CATH3(1-29) regardless of lipid type and composition. The leakage results of Cc-CATH3(1-29) share a similar trend with that in Cc-CATH3(5-29); they exhibit no preferential binding to anionic phospholipids. In conclusion, the results suggested that the first four residues at the N-terminus "RVRR" is not essential for presenting all test activities. In contrast, residues five to eight of "FWPL" are necessary as the exclusion of this short motif in Cc-CATH3(9-29) and Cc-CATH3(13-29) leads to a loss of activities. This study will be beneficial for further design and development of Cc-CATH3 to be novel antibiotic.

  12. Investigating Sterol and Redox Regulation of the Ion Channel Activity of CLIC1 Using Tethered Bilayer Membranes.

    PubMed

    Al Khamici, Heba; Hossain, Khondher R; Cornell, Bruce A; Valenzuela, Stella M

    2016-12-08

    The Chloride Intracellular Ion Channel (CLIC) family consists of six conserved proteins in humans. These are a group of enigmatic proteins, which adopt both a soluble and membrane bound form. CLIC1 was found to be a metamorphic protein, where under specific environmental triggers it adopts more than one stable reversible soluble structural conformation. CLIC1 was found to spontaneously insert into cell membranes and form chloride ion channels. However, factors that control the structural transition of CLIC1 from being an aqueous soluble protein into a membrane bound protein have yet to be adequately described. Using tethered bilayer lipid membranes and electrical impedance spectroscopy system, herein we demonstrate that CLIC1 ion channel activity is dependent on the type and concentration of sterols in bilayer membranes. These findings suggest that membrane sterols play an essential role in CLIC1's acrobatic switching from a globular soluble form to an integral membrane form, promoting greater ion channel conductance in membranes. What remains unclear is the precise nature of this regulation involving membrane sterols and ultimately determining CLIC1's membrane structure and function as an ion channel. Furthermore, our impedance spectroscopy results obtained using CLIC1 mutants, suggest that the residue Cys24 is not essential for CLIC1's ion channel function. However Cys24 does appear important for optimal ion channel activity. We also observe differences in conductance between CLIC1 reduced and oxidized forms when added to our tethered membranes. Therefore, we conclude that both membrane sterols and redox play a role in the ion channel activity of CLIC1.

  13. Investigating Sterol and Redox Regulation of the Ion Channel Activity of CLIC1 Using Tethered Bilayer Membranes

    PubMed Central

    Al Khamici, Heba; Hossain, Khondker R.; Cornell, Bruce A.; Valenzuela, Stella M.

    2016-01-01

    The Chloride Intracellular Ion Channel (CLIC) family consists of six conserved proteins in humans. These are a group of enigmatic proteins, which adopt both a soluble and membrane bound form. CLIC1 was found to be a metamorphic protein, where under specific environmental triggers it adopts more than one stable reversible soluble structural conformation. CLIC1 was found to spontaneously insert into cell membranes and form chloride ion channels. However, factors that control the structural transition of CLIC1 from being an aqueous soluble protein into a membrane bound protein have yet to be adequately described. Using tethered bilayer lipid membranes and electrical impedance spectroscopy system, herein we demonstrate that CLIC1 ion channel activity is dependent on the type and concentration of sterols in bilayer membranes. These findings suggest that membrane sterols play an essential role in CLIC1’s acrobatic switching from a globular soluble form to an integral membrane form, promoting greater ion channel conductance in membranes. What remains unclear is the precise nature of this regulation involving membrane sterols and ultimately determining CLIC1’s membrane structure and function as an ion channel. Furthermore, our impedance spectroscopy results obtained using CLIC1 mutants, suggest that the residue Cys24 is not essential for CLIC1’s ion channel function. However Cys24 does appear important for optimal ion channel activity. We also observe differences in conductance between CLIC1 reduced and oxidized forms when added to our tethered membranes. Therefore, we conclude that both membrane sterols and redox play a role in the ion channel activity of CLIC1. PMID:27941637

  14. Effect of membrane-associated f1 bacteriophage coat protein upon the activity of Escherichia coli phosphatidylserine synthetase.

    PubMed Central

    Chamberlain, B K; Webster, R E

    1978-01-01

    The effects of insertion of the major coat protein of f1 bacteriophage into Escherichia coli membranes were investigated under conditions allowing in vivo analysis of phosphatidylserine synthesis. An E. coli strain possessing a temperature-sensitive phosphatidylserine decarboxylase was utilized under conditions in which the decarboxylase activity was reduced but nonlethal. The presence of the coat protein in the host membranes inhibits the activity of the phosphatidylserine synthetase and perhaps affects the activity of the phosphatidylserine decarboxylase. PMID:211116

  15. Biological removal of antiandrogenic activity in gray wastewater and coking wastewater by membrane reactor process.

    PubMed

    Ma, Dehua; Chen, Lujun; Liu, Cong; Bao, Chenjun; Liu, Rui

    2015-07-01

    A recombinant human androgen receptor yeast assay was applied to investigate the occurrence of antiandrogens as well as the mechanism for their removal during gray wastewater and coking wastewater treatment. The membrane reactor (MBR) system for gray wastewater treatment could remove 88.0% of antiandrogenic activity exerted by weakly polar extracts and 97.3% of that by moderately strong polar extracts, but only 32.5% of that contributed by strong polar extracts. Biodegradation by microorganisms in the MBR contributed to 95.9% of the total removal. After the treatment, the concentration of antiandrogenic activity in the effluent was still 1.05 μg flutamide equivalence (FEQ)/L, 36.2% of which was due to strong polar extracts. In the anaerobic reactor, anoxic reactor, and membrane reactor system for coking wastewater treatment, the antiandrogenic activity of raw coking wastewater was 78.6 mg FEQ/L, and the effluent of the treatment system had only 0.34 mg FEQ/L. The antiandrogenic activity mainly existed in the medium strong polar and strong polar extracts. Biodegradation by microorganisms contributed to at least 89.2% of the total antiandrogenic activity removal in the system. Biodegradation was the main removal mechanism of antiandrogenic activity in both the wastewater treatment systems.

  16. Complex Intrinsic Membrane Properties and Dopamine Shape Spiking Activity in a Motor Axon

    PubMed Central

    Ballo, Aleksander W.; Bucher, Dirk

    2009-01-01

    We studied the peripheral motor axons of the two pyloric dilator (PD) neurons of the stomatogastric ganglion in the lobster, Homarus americanus. Intracellular recordings from the motor nerve showed both fast and slow voltage- and activity-dependent dynamics. During rhythmic bursts, the PD axons displayed changes in spike amplitude and duration. Pharmacological experiments and the voltage-dependence of these phenomena suggest that inactivation of sodium and A-type potassium channels are responsible. In addition, the “resting” membrane potential was dependent on ongoing spike or burst activity, with more hyperpolarized values when activity was strong. Nerve stimulations, pharmacological block and current clamp experiments suggest that this is due to a functional antagonism between a slow after-hyperpolarization (sAHP) and inward rectification through hyperpolarization-activated current (IH). Dopamine application resulted in modest depolarization and “ectopic” peripheral spike initiation in the absence of centrally generated activity. This effect was blocked by CsCl and ZD7288, consistent with a role of IH. High frequency nerve stimulation inhibited peripheral spike initiation for several seconds, presumably due to the sAHP. Both during normal bursting activity and antidromic nerve stimulation, the conduction delay over the length of the peripheral nerve changed in a complex manner. This suggests that axonal membrane dynamics can have a substantial effect on the temporal fidelity of spike patterns propagated from a spike initiation site to a synaptic target, and that neuromodulators can influence the extent to which spike patterns are modified. PMID:19386902

  17. Structural Correlates of Antibacterial and Membrane-Permeabilizing Activities in Acylpolyamines

    PubMed Central

    Balakrishna, Rajalakshmi; Wood, Stewart J.; Nguyen, Thuan B.; Miller, Kelly A.; Suresh Kumar, E. V. K.; Datta, Apurba; David, Sunil A.

    2006-01-01

    A homologous series of mono- and bis-acyl polyamines with varying acyl chain lengths originally synthesized for the purpose of sequestering lipopolysaccharide were evaluated for antimicrobial activity to test the hypothesis that these bis-cationic amphipathic compounds may also bind to and permeabilize intact gram-negative bacterial membranes. Some compounds were found to possess significant antimicrobial activity, mediated via permeabilization of bacterial membranes. Structure-activity relationship studies revealed a strong dependence of the acyl chain length on antimicrobial potency and permeabilization activity. Homologated spermine, bis-acylated with C8 or C9 chains, was found to profoundly sensitize Escherichia coli to hydrophobic antibiotics such as rifampin. Nonspecific cytotoxicity is a potential drawback of these membranophilic compounds. However, the surface activity of these cationic amphipaths is strongly attenuated under physiological conditions via binding to serum albumin. Significant antibacterial activity is still retained in the presence of physiological concentrations of human serum albumin, suggesting that these compounds may serve as leads in the development of novel adjuncts to conventional antimicrobial chemotherapy. PMID:16495242

  18. Caffeine-activated large-conductance plasma membrane cation channels in cardiac myocytes: characteristics and significance.

    PubMed

    Zhang, Yu-An; Tuft, Richard A; Lifshitz, Lawrence M; Fogarty, Kevin E; Singer, Joshua J; Zou, Hui

    2007-10-01

    Caffeine-activated, large-conductance, nonselective cation channels (LCCs) have been found in the plasma membrane of isolated cardiac myocytes in several species. However, little is known about the effects of opening these channels. To examine such effects and to further understand the caffeine-activation mechanism, we carried out studies using whole-cell patch-clamp techniques with freshly isolated cardiac myocytes from rats and mice. Unlike previous studies, thapsigargin was used so that both the effect of opening LCCs and the action of caffeine were independent of Ca(2+) release from intracellular stores. These Ca(2+)-permeable LCCs were found in a majority of the cells from atria and ventricles, with a conductance of approximately 370 pS in rat atria. Caffeine and all its direct metabolic products (theophylline, theobromine, and paraxanthine) activated the channel, while isocaffeine did not. Although they share some similarities with ryanodine receptors (RyRs, the openings of which give rise to Ca(2+) sparks), LCCs also showed some different characteristics. With simultaneous Ca(2+) imaging and current recording, the localized fluorescence increase due to Ca(2+) entry through a single opening of an LCC (SCCaFT) was detected. When membrane potential, instead of current, was recorded, SCCaFT-like fluorescence transients (indicating single LCC openings) were found to accompany membrane depolarizations. To our knowledge, this is the first report directly linking membrane potential changes to a single opening of an ion channel. Moreover, these events in cardiac cells suggest a possible additional mechanism by which caffeine and theophylline contribute to the generation of cardiac arrhythmias.

  19. Photosynthesis Activates Plasma Membrane H+-ATPase via Sugar Accumulation1[OPEN

    PubMed Central

    Okumura, Masaki; Inoue, Shin-ichiro; Kuwata, Keiko

    2016-01-01

    Plant plasma membrane H+-ATPase acts as a primary transporter via proton pumping and regulates diverse physiological responses by controlling secondary solute transport, pH homeostasis, and membrane potential. Phosphorylation of the penultimate threonine and the subsequent binding of 14-3-3 proteins in the carboxyl terminus of the enzyme are required for H+-ATPase activation. We showed previously that photosynthesis induces phosphorylation of the penultimate threonine in the nonvascular bryophyte Marchantia polymorpha. However, (1) whether this response is conserved in vascular plants and (2) the process by which photosynthesis regulates H+-ATPase phosphorylation at the plasma membrane remain unresolved issues. Here, we report that photosynthesis induced the phosphorylation and activation of H+-ATPase in Arabidopsis (Arabidopsis thaliana) leaves via sugar accumulation. Light reversibly phosphorylated leaf H+-ATPase, and this process was inhibited by pharmacological and genetic suppression of photosynthesis. Immunohistochemical and biochemical analyses indicated that light-induced phosphorylation of H+-ATPase occurred autonomously in mesophyll cells. We also show that the phosphorylation status of H+-ATPase and photosynthetic sugar accumulation in leaves were positively correlated and that sugar treatment promoted phosphorylation. Furthermore, light-induced phosphorylation of H+-ATPase was strongly suppressed in a double mutant defective in ADP-glucose pyrophosphorylase and triose phosphate/phosphate translocator (adg1-1 tpt-2); these mutations strongly inhibited endogenous sugar accumulation. Overall, we show that photosynthesis activated H+-ATPase via sugar production in the mesophyll cells of vascular plants. Our work provides new insight into signaling from chloroplasts to the plasma membrane ion transport mechanism. PMID:27016447

  20. Mg2+ is an essential activator of hydrolytic activity of membrane-bound pyrophosphatase of Rhodospirillum rubrum.

    PubMed Central

    Sosa, A; Ordaz, H; Romero, I; Celis, H

    1992-01-01

    The substrate for the hydrolytic activity of membrane-bound pyrophosphatase is the PP(i)-Mg2+ complex. The enzyme has no activity when the free Mg2+ concentration is lower than 10 microM (at 0.5 mM-PP(i)-Mg2+), and therefore free Mg2+ is an essential activator of the hydrolytic activity. The Km for the substrate changes in response to variation in free Mg2+ concentration, from 10.25 to 0.6 mM when free Mg2+ is increased from 0.03 to 1.0 mM respectively. The Km for Mg2+ depends on the substrate concentration: the Km decreases from 0.52 to 0.14 mM from 0.25 to 0.75 mM-PP(i)-Mg2+ respectively. The extrapolated Km for Mg2+ in the absence of the substrate is 0.73 mM. Imidodiphosphate-Mg2+ and free Ca2+ were used as competitive inhibitors of substrate and activator respectively. The equilibrium binding kinetics suggest an ordered mechanism for the activator and the substrate: Mg2+ ions bind the enzyme before PP(i)-Mg2+ in the formation of the catalytic complex, membrane-bound pyrophosphatase-(Mg2+)-(PP(i)-Mg2+). PMID:1315519

  1. The activation loop of PIP5K functions as a membrane sensor essential for lipid substrate processing

    PubMed Central

    Liu, Aizhuo; Sui, Dexin; Wu, Dianqing; Hu, Jian

    2016-01-01

    Phosphatidylinositol 4-phosphate 5-kinase (PIP5K), a representative member of the phosphatidylinositol phosphate kinase (PIPK) family, is a major enzyme that biosynthesizes the signaling molecule PI(4,5)P2 (phosphatidylinositol 4,5-bisphosphate) in eukaryotic cells. The stringent specificity toward lipid substrates and the high sensitivity to the membrane environment strongly suggest a membrane-sensing mechanism, but the underlying structural basis is still largely unknown. We present a nuclear magnetic resonance (NMR) study on a peptide commensurate with a PIP5K’s activation loop, which has been reported to be a determinant of lipid substrate specificity and subcellular localization of PIP5K. Although the activation loop is severely disordered in the crystal structure of PIP5K, the NMR experiments showed that the largely unstructured peptide folded into an amphipathic helix upon its association with the 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) micellar surface. Systematic mutagenesis and functional assays further demonstrated the crucial roles of the amphipathic helix and its hydrophobic surface in kinase activity and membrane-sensing function, supporting a working model in which the activation loop is a critical structural module conferring a membrane-sensing mechanism on PIP5K. The activation loop, surprisingly functioning as a membrane sensor, represents a new paradigm of kinase regulation by the activation loop through protein-membrane interaction, which also lays a foundation on the regulation of PIP5K (and other PIPKs) by membrane lipids for future studies. PMID:28138522

  2. A pore-forming toxin requires a specific residue for its activity in membranes with particular physicochemical properties.

    PubMed

    Morante, Koldo; Caaveiro, Jose M M; Tanaka, Koji; González-Mañas, Juan Manuel; Tsumoto, Kouhei

    2015-04-24

    The physicochemical landscape of the bilayer modulates membrane protein function. Actinoporins are a family of potent hemolytic proteins from sea anemones acting at the membrane level. This family of cytolysins preferentially binds to target membranes containing sphingomyelin, where they form lytic pores giving rise to cell death. Although the cytolytic activity of the actinoporin fragaceatoxin C (FraC) is sensitive to vesicles made of various lipid compositions, it is far from clear how this toxin adjusts its mechanism of action to a broad range of physiochemical landscapes. Herein, we show that the conserved residue Phe-16 of FraC is critical for pore formation in cholesterol-rich membranes such as those of red blood cells. The interaction of a panel of muteins of Phe-16 with model membranes composed of raft-like lipid domains is inactivated in cholesterol-rich membranes but not in cholesterol-depleted membranes. These results indicate that actinoporins recognize different membrane environments, resulting in a wider repertoire of susceptible target membranes (and preys) for sea anemones. In addition, this study has unveiled promising candidates for the development of protein-based biosensors highly sensitive to the concentration of cholesterol within the membrane.

  3. α-Synuclein Membrane Association Is Regulated by the Rab3a Recycling Machinery and Presynaptic Activity*♦

    PubMed Central

    Chen, Robert H. C.; Wislet-Gendebien, Sabine; Samuel, Filsy; Visanji, Naomi P.; Zhang, Gang; Marsilio, Diana; Langman, Tammy; Fraser, Paul E.; Tandon, Anurag

    2013-01-01

    α-Synuclein is an abundant presynaptic protein and a primary component of Lewy bodies in Parkinson disease. Although its pathogenic role remains unclear, in healthy nerve terminals α-synuclein undergoes a cycle of membrane binding and dissociation. An α-synuclein binding assay was used to screen for vesicle proteins involved in α-synuclein membrane interactions and showed that antibodies directed to the Ras-related GTPase Rab3a and its chaperone RabGDI abrogated α-synuclein membrane binding. Biochemical analyses, including density gradient sedimentation and co-immunoprecipitation, suggested that α-synuclein interacts with membrane-associated GTP-bound Rab3a but not to cytosolic GDP-Rab3a. Accumulation of membrane-bound α-synuclein was induced by the expression of a GTPase-deficient Rab3a mutant, by a dominant-negative GDP dissociation inhibitor mutant unable to recycle Rab3a off membranes, and by Hsp90 inhibitors, radicicol and geldanamycin, which are known to inhibit Rab3a dissociation from membranes. Thus, all treatments that inhibited Rab3a recycling also increased α-synuclein sequestration on intracellular membranes. Our results suggest that membrane-bound GTP-Rab3a stabilizes α-synuclein on synaptic vesicles and that the GDP dissociation inhibitor·Hsp90 complex that controls Rab3a membrane dissociation also regulates α-synuclein dissociation during synaptic activity. PMID:23344955

  4. Alkyl Galactofuranosides Strongly Interact with Leishmania donovani Membrane and Provide Antileishmanial Activity

    PubMed Central

    Suleman, Muhammad; Gangneux, Jean-Pierre; Legentil, Laurent; Belaz, Sorya; Cabezas, Yari; Manuel, Christelle; Dureau, Rémy; Sergent, Odile; Burel, Agnès; Daligault, Franck; Ferrières, Vincent

    2014-01-01

    We investigated the in vitro effects of four alkyl-galactofuranoside derivatives, i.e., octyl-β-d-galactofuranoside (compound 1), 6-amino-β-d-galactofuranoside (compound 2), 6-N-acetamido-β-d-galactofuranoside (compound 3), and 6-azido-β-d-galactofuranoside (compound 4), on Leishmania donovani. Their mechanism of action was explored using electron paramagnetic resonance spectroscopy (EPR) and nuclear magnetic resonance (NMR), and ultrastructural alterations were analyzed by transmission electron microscopy (TEM). Compound 1 showed the most promising effects by inhibiting promastigote growth at a 50% inhibitory concentration (IC50) of 8.96 ± 2.5 μM. All compounds exhibit low toxicity toward human macrophages. Compound 1 had a higher selectivity index than the molecule used for comparison, i.e., miltefosine (159.7 versus 37.9, respectively). EPR showed that compound 1 significantly reduced membrane fluidity compared to control promastigotes and to compound 3. The furanose ring was shown to support this effect, since the isomer galactopyranose had no effect on parasite membrane fluidity or growth. NMR showed a direct interaction of all compounds (greatest with compound 1, followed by compounds 2, 3, and 4, in descending order) with the promastigote membrane and with octyl-galactopyranose and octanol, providing evidence that the n-octyl chain was primarily involved in anchoring with the parasite membrane, followed by the putative crucial role of the furanose ring in the antileishmanial activity. A morphological analysis of compound 1-treated promastigotes by TEM revealed profound alterations in the parasite membrane and organelles, but this was not the case with compound 3. Quantification of annexin V binding by flow cytometry confirmed that compound 1 induced apoptosis in >90% of promastigotes. The effect of compound 1 was also assessed on intramacrophagic amastigotes and showed a reduction in amastigote growth associated with an increase of reactive oxygen

  5. Alkyl galactofuranosides strongly interact with Leishmania donovani membrane and provide antileishmanial activity.

    PubMed

    Suleman, Muhammad; Gangneux, Jean-Pierre; Legentil, Laurent; Belaz, Sorya; Cabezas, Yari; Manuel, Christelle; Dureau, Rémy; Sergent, Odile; Burel, Agnès; Daligault, Franck; Ferrières, Vincent; Robert-Gangneux, Florence

    2014-01-01

    We investigated the in vitro effects of four alkyl-galactofuranoside derivatives, i.e., octyl-β-D-galactofuranoside (compound 1), 6-amino-β-D-galactofuranoside (compound 2), 6-N-acetamido-β-D-galactofuranoside (compound 3), and 6-azido-β-D-galactofuranoside (compound 4), on Leishmania donovani. Their mechanism of action was explored using electron paramagnetic resonance spectroscopy (EPR) and nuclear magnetic resonance (NMR), and ultrastructural alterations were analyzed by transmission electron microscopy (TEM). Compound 1 showed the most promising effects by inhibiting promastigote growth at a 50% inhibitory concentration (IC50) of 8.96±2.5 μM. All compounds exhibit low toxicity toward human macrophages. Compound 1 had a higher selectivity index than the molecule used for comparison, i.e., miltefosine (159.7 versus 37.9, respectively). EPR showed that compound 1 significantly reduced membrane fluidity compared to control promastigotes and to compound 3. The furanose ring was shown to support this effect, since the isomer galactopyranose had no effect on parasite membrane fluidity or growth. NMR showed a direct interaction of all compounds (greatest with compound 1, followed by compounds 2, 3, and 4, in descending order) with the promastigote membrane and with octyl-galactopyranose and octanol, providing evidence that the n-octyl chain was primarily involved in anchoring with the parasite membrane, followed by the putative crucial role of the furanose ring in the antileishmanial activity. A morphological analysis of compound 1-treated promastigotes by TEM revealed profound alterations in the parasite membrane and organelles, but this was not the case with compound 3. Quantification of annexin V binding by flow cytometry confirmed that compound 1 induced apoptosis in >90% of promastigotes. The effect of compound 1 was also assessed on intramacrophagic amastigotes and showed a reduction in amastigote growth associated with an increase of reactive oxygen

  6. Fatty acid composition of plasma lipids and erythrocyte membranes during simulated extravehicular activity

    NASA Astrophysics Data System (ADS)

    Skedina, M. A.; Katuntsev, V. P.; Buravkova, L. B.; Naidina, V. P.

    Ten subjects (from 27 to 41 years) have been participated in 32 experiments. They were decompressed from ground level to 40-35 kPa in altitude chamber when breathed 100% oxygen by mask and performed repeated cycles of exercises (3.0 Kcal/min). The intervals between decompressions were 3-5 days. Plasma lipid and erythrocyte membrane fatty acid composition was evaluated in the fasting venous blood before and immediately after hypobaric exposure. There were 7 cases decompression sickness (DCS). Venous gas bubbles (GB) were detected in 27 cases (84.4%). Any significant changes in the fatty acid composition of erythrocyte membranes and plasma didn't practically induce after the first decompression. However, by the beginning of the second decompression the total lipid level in erythrocyte membranes decreased from 54.6 mg% to 40.4 mg% in group with DCS symptoms and from 51.2 mg% to 35.2 mg% (p < 0.05) without DCS symptoms. In group with DCS symptoms a tendency to increased level of saturated fatty acids in erythrocyte membranes (16:0, 18:0), the level of the polyunsaturated linoleic fatty acid (18:2) and arachidonic acid (20:4) tended to be decreased by the beginning of the second decompression. Insignificant changes in blood plasma fatty acid composition was observed in both groups. The obtained biochemical data that indicated the simulated extravehicular activity (EVA) condition is accompanied by the certain changes in the blood lipid metabolism, structural and functional state of erythrocyte membranes, which are reversible. The most pronounced changes are found in subjects with DCS symptoms.

  7. FCCP depolarizes plasma membrane potential by activating proton and Na+ currents in bovine aortic endothelial cells.

    PubMed

    Park, Kyu-Sang; Jo, Inho; Pak, Kim; Bae, Sung-Won; Rhim, Hyewhon; Suh, Suk-Hyo; Park, Jin; Zhu, Hong; So, Insuk; Kim, Ki Whan

    2002-01-01

    We investigated the effects of carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP), a protonophore and uncoupler of mitochondrial oxidative phosphorylation in mitochondria, on plasma membrane potential and ionic currents in bovine aortic endothelial cells (BAECs). The membrane potential and ionic currents of BAECs were recorded using the patch-clamp technique in current-clamp and voltage-clamp modes, respectively. FCCP activated ionic currents and depolarized the plasma membrane potential in a dose-dependent manner. Neither the removal of extracellular Ca2+ nor pretreatment with BAPTA/AM affected the FCCP-induced currents, implying that the currents are not associated with the FCCP-induced intracellular [Ca2+]i increase. FCCP-induced currents were significantly influenced by the changes in extracellular or intracellular pH; the increased proton gradient produced by lowering the extracellular pH or intracellular alkalinization augmented the changes in membrane potential and ionic currents caused by FCCP. FCCP-induced currents were significantly reduced under extracellular Na+-free conditions. The reversal potentials of FCCP-induced currents under Na+-free conditions were well fitted to the calculated equilibrium potential for protons. Interestingly, FCCP-induced Na+ transport (subtracted currents, I(control)- I(Na+-free) was closely dependent on extracellular pH, whereas FCCP-induced H+transport was not significantly affected by the absence of Na+. These results suggest that the FCCP-induced ionic currents and depolarization, which are strongly dependent on the plasmalemmal proton gradient, are likely to be mediated by both H+ and Na+ currents across the plasma membrane. The relationship between H+ and Na+ transport still needs to be determined.

  8. Regulation of the Membrane Insertion and Conductance Activity of the Metamorphic Chloride Intracellular Channel Protein CLIC1 by Cholesterol

    PubMed Central

    Valenzuela, Stella M.; Alkhamici, Heba; Brown, Louise J.; Almond, Oscar C.; Goodchild, Sophia C.; Carne, Sonia; Curmi, Paul M. G.; Holt, Stephen A.; Cornell, Bruce A.

    2013-01-01

    The Chloride Intracellular ion channel protein CLIC1 has the ability to spontaneously insert into lipid membranes from a soluble, globular state. The precise mechanism of how this occurs and what regulates this insertion is still largely unknown, although factors such as pH and redox environment are known contributors. In the current study, we demonstrate that the presence and concentration of cholesterol in the membrane regulates the spontaneous insertion of CLIC1 into the membrane as well as its ion channel activity. The study employed pressure versus area change measurements of Langmuir lipid monolayer films; and impedance spectroscopy measurements using tethered bilayer membranes to monitor membrane conductance during and following the addition of CLIC1 protein. The observed cholesterol dependent behaviour of CLIC1 is highly reminiscent of the cholesterol-dependent-cytolysin family of bacterial pore-forming proteins, suggesting common regulatory mechanisms for spontaneous protein insertion into the membrane bilayer. PMID:23457643

  9. Regulation of the membrane insertion and conductance activity of the metamorphic chloride intracellular channel protein CLIC1 by cholesterol.

    PubMed

    Valenzuela, Stella M; Alkhamici, Heba; Brown, Louise J; Almond, Oscar C; Goodchild, Sophia C; Carne, Sonia; Curmi, Paul M G; Holt, Stephen A; Cornell, Bruce A

    2013-01-01

    The Chloride Intracellular ion channel protein CLIC1 has the ability to spontaneously insert into lipid membranes from a soluble, globular state. The precise mechanism of how this occurs and what regulates this insertion is still largely unknown, although factors such as pH and redox environment are known contributors. In the current study, we demonstrate that the presence and concentration of cholesterol in the membrane regulates the spontaneous insertion of CLIC1 into the membrane as well as its ion channel activity. The study employed pressure versus area change measurements of Langmuir lipid monolayer films; and impedance spectroscopy measurements using tethered bilayer membranes to monitor membrane conductance during and following the addition of CLIC1 protein. The observed cholesterol dependent behaviour of CLIC1 is highly reminiscent of the cholesterol-dependent-cytolysin family of bacterial pore-forming proteins, suggesting common regulatory mechanisms for spontaneous protein insertion into the membrane bilayer.

  10. Listeriolysin O Membrane Damaging Activity Involves Arc Formation and Lineaction -- Implication for Listeria monocytogenes Escape from Phagocytic Vacuole

    PubMed Central

    Ruan, Yi; Rezelj, Saša; Bedina Zavec, Apolonija; Anderluh, Gregor; Scheuring, Simon

    2016-01-01

    Listeriolysin-O (LLO) plays a crucial role during infection by Listeria monocytogenes. It enables escape of bacteria from phagocytic vacuole, which is the basis for its spread to other cells and tissues. It is not clear how LLO acts at phagosomal membranes to allow bacterial escape. The mechanism of action of LLO remains poorly understood, probably due to unavailability of suitable experimental tools that could monitor LLO membrane disruptive activity in real time. Here, we used high-speed atomic force microscopy (HS-AFM) featuring high spatio-temporal resolution on model membranes and optical microscopy on giant unilamellar vesicles (GUVs) to investigate LLO activity. We analyze the assembly kinetics of toxin oligomers, the prepore-to-pore transition dynamics and the membrane disruption in real time. We reveal that LLO toxin efficiency and mode of action as a membrane-disrupting agent varies strongly depending on the membrane cholesterol concentration and the environmental pH. We discovered that LLO is able to form arc pores as well as damage lipid membranes as a lineactant, and this leads to large-scale membrane defects. These results altogether provide a mechanistic basis of how large-scale membrane disruption leads to release of Listeria from the phagocytic vacuole in the cellular context. PMID:27104344

  11. Development of adsorptive membranes by confinement of activated biochar into electrospun nanofibers

    PubMed Central

    Taheran, Mehrdad; Naghdi, Mitra; Knystautas, Emile; Verma, Mausam; Surampalli, Rao Y; Valero, Jose R

    2016-01-01

    Adsorptive membranes have many applications in removal of contaminants, such as heavy metals and organic contaminants from water. Recently, increasing concentrations of pharmaceutically active compounds, especially antibiotics, such as chlortetracycline in water and wastewater sources has raised concerns about their potentially adverse impacts on environment and human health. In this study, a series of polyacrylonitrile (PAN)/activated biochar nanofibrous membranes (NFMs) with different loadings of biochar (0–2%, w/w) were fabricated using electrospinning. The morphology and structure of fabricated membranes was investigated by scanning electron microscopy, Fourier transform infrared and thermogravimetric analysis. The results showed that at 1.5% of biochar loading, the surface area reached the maximum value of 12.4 m2/g and beyond this loading value, agglomeration of particles inhibited fine interaction with nanofibrous matrix. Also, the adsorption tests using chlortetracycline showed that, under environmentally relevant concentrations, the fabricated adsorptive NFMs had a potential for removal of these types of emerging contaminants from water and wastewaters. PMID:28144506

  12. Sweetness-induced activation of membrane dipole potential in STC-1 taste cells.

    PubMed

    Chen, Li-Chun; Xie, Ning-Ning; Deng, Shao-Ping

    2016-12-01

    The biological functions of cell membranes strongly influence the binding and transport of molecular species. We developed STC-1 cell line stably expressing the sweet taste receptor (T1R2/T1R3), and explored the possible correlation between sweeteners and membrane dipole potential of STC-1 cells. In this study, sweetener-induced dipole potential activation was elucidated using a fluorescence-based measurement technique, by monitoring the voltage sensitive probe Di-8-ANEPPS using a dual wavelength ratiometric approach. It indicated that the presence of sweeteners resulted in cell membrane dipole potential change, and interaction of artificial sweeteners with taste cells resulted in a greater reduction in potential compared with natural sweeteners. Our work presents a newly developed approach using a fluorescence-based measurement technique to study sweetener-induced dipole potential activation of STC-1 cells. This new approach could be used as a complementary tool to study the function of sweet taste receptors or other GPCRs and helps to understand the basis sweetness mechanism.

  13. The membrane remodeling protein Pex11p activates the GTPase Dnm1p during peroxisomal fission

    PubMed Central

    Opalinski, Lukasz; Landgraf, Christiane; Costello, Joseph; Schrader, Michael; Krikken, Arjen M.; Knoops, Kèvin; Kram, Anita M.; Volkmer, Rudolf; van der Klei, Ida J.

    2015-01-01

    The initial phase of peroxisomal fission requires the peroxisomal membrane protein Peroxin 11 (Pex11p), which remodels the membrane, resulting in organelle elongation. Here, we identify an additional function for Pex11p, demonstrating that Pex11p also plays a crucial role in the final step of peroxisomal fission: dynamin-like protein (DLP)-mediated membrane scission. First, we demonstrate that yeast Pex11p is necessary for the function of the GTPase Dynamin-related 1 (Dnm1p) in vivo. In addition, our data indicate that Pex11p physically interacts with Dnm1p and that inhibiting this interaction compromises peroxisomal fission. Finally, we demonstrate that Pex11p functions as a GTPase activating protein (GAP) for Dnm1p in vitro. Similar observations were made for mammalian Pex11β and the corresponding DLP Drp1, indicating that DLP activation by Pex11p is conserved. Our work identifies a previously unknown requirement for a GAP in DLP function. PMID:25941407

  14. Antimicrobial activity of melanoidins against Escherichia coli is mediated by a membrane-damage mechanism.

    PubMed

    Rurián-Henares, Jose A; Morales, Francisco J

    2008-04-09

    Melanoidins are brown polymeric material formed during thermal processing of food and widely distributed in the Western diet. Three water-soluble fractions were isolated from both commercial coffee and biscuit by sequential ultrafiltration steps (3 and 10 kDa cutoff). Biscuits were enzymatically digested to solubilize the protein-linked melanoidin fraction. Antimicrobial activity of melanoidins was evaluated against a Gram-negative reference pathogenic bacterium (Escherichia coli). The high-molecular-weight fraction of water-soluble melanoidins (>10 kDa) exerted the highest antimicrobial activity. The mechanism of action was further investigated by cell integrity and outer- and inner-membrane permeabilization assays. At the minimum inhibitory concentration, melanoidins provoked irreversible cell membrane disruption, which was independent of the bacterial transmembrane potential. Results indicate that water-soluble melanoidins killed pathogenic bacteria strains ( E. coli) by causing irreversible changes in both the inner and outer membranes. Likely, it allows for interference with biosynthetic processes, such as the inhibition of nutrient transport and macromolecular precursors.

  15. Human proximal tubule epithelial cells cultured on hollow fibers: living membranes that actively transport organic cations.

    PubMed

    Jansen, J; De Napoli, I E; Fedecostante, M; Schophuizen, C M S; Chevtchik, N V; Wilmer, M J; van Asbeck, A H; Croes, H J; Pertijs, J C; Wetzels, J F M; Hilbrands, L B; van den Heuvel, L P; Hoenderop, J G; Stamatialis, D; Masereeuw, R

    2015-11-16

    The bioartificial kidney (BAK) aims at improving dialysis by developing 'living membranes' for cells-aided removal of uremic metabolites. Here, unique human conditionally immortalized proximal tubule epithelial cell (ciPTEC) monolayers were cultured on biofunctionalized MicroPES (polyethersulfone) hollow fiber membranes (HFM) and functionally tested using microfluidics. Tight monolayer formation was demonstrated by abundant zonula occludens-1 (ZO-1) protein expression along the tight junctions of matured ciPTEC on HFM. A clear barrier function of the monolayer was confirmed by limited diffusion of FITC-inulin. The activity of the organic cation transporter 2 (OCT2) in ciPTEC was evaluated in real-time using a perfusion system by confocal microscopy using 4-(4-(dimethylamino)styryl)-N-methylpyridinium iodide (ASP(+)) as a fluorescent substrate. Initial ASP(+) uptake was inhibited by a cationic uremic metabolites mixture and by the histamine H2-receptor antagonist, cimetidine. In conclusion, a 'living membrane' of renal epithelial cells on MicroPES HFM with demonstrated active organic cation transport was successfully established as a first step in BAK engineering.

  16. Antimicrobial properties of membrane-active dodecapeptides derived from MSI-78.

    PubMed

    Monteiro, Claudia; Fernandes, Mariana; Pinheiro, Marina; Maia, Sílvia; Seabra, Catarina L; Ferreira-da-Silva, Frederico; Costa, Fabíola; Reis, Salette; Gomes, Paula; Martins, M Cristina L

    2015-05-01

    Antimicrobial peptides (AMPs) are a class of broad-spectrum antibiotics known by their ability to disrupt bacterial membranes and their low tendency to induce bacterial resistance, arising as excellent candidates to fight bacterial infections. In this study we aimed at designing short 12-mer AMPs, derived from a highly effective and broad spectrum synthetic AMP, MSI-78 (22 residues), by truncating this peptide at the N- and/or C-termini while spanning its entire sequence with 1 amino acid (aa) shifts. These designed peptides were evaluated regarding antimicrobial activity against selected gram-positive Staphylococcus strains and the gram-negative Pseudomonas aeruginosa (P. aeruginosa). The short 12-mer peptide CEM1 (GIGKFLKKAKKF) was identified as an excellent candidate to fight P. aeruginosa infections as it displays antimicrobial activity against this strain and selectivity, with negligible toxicity to mammalian cells even at high concentrations. However, in general most of the short 12-mer peptides tested showed a reduction in antimicrobial activity, an effect that was more pronounced for gram-positive Staphylococcus strains. Interestingly, CEM1 and a highly similar peptide differing by only one aa-shift (CEM2: IGKFLKKAKKFG), showed a remarkably contrasting AMP activity. These two peptides were chosen for a more detailed study regarding their mechanism of action, using several biophysical assays and simple membrane models that mimic the mammalian and bacterial lipid composition. We confirmed the correlation between peptide helicity and antimicrobial activity and propose a mechanism of action based on the disruption of the bacterial membrane permeability barrier.

  17. A protein chip membrane-capture assay for botulinum neurotoxin activity

    SciTech Connect

    Marconi, Severine; Ferracci, Geraldine; Berthomieu, Maelys; Kozaki, Shunji; Miquelis, Raymond; Boucraut, Jose; Seagar, Michael

    2008-12-15

    Botulinum neurotoxins A and B (BoNT/A and B) are neuromuscular blocking agents which inhibit neurotransmission by cleaving the intra-cellular presynaptic SNARE proteins SNAP-25 and VAMP2, localized respectively in plasma membrane and synaptic vesicles. These neurotoxins are both dangerous pathogens and powerful therapeutic agents with numerous clinical and cosmetic applications. Consequently there is a need for in vitro assays of their biological activity to screen for potential inhibitors and to replace the widely used in vivo mouse assay. Surface plasmon resonance (SPR) was used to measure membrane vesicle capture by antibodies against SNAP-25 and VAMP2. Substrate cleavage by BoNTs modified capture providing a method to assay toxin activity. Firstly using synaptic vesicles as a substrate, a comparison of the EC{sub 50}s for BoNT/B obtained by SPR, ELISA or flow cytometry indicated similar sensitivity although SPR assays were more rapid. Sonication of brain or neuronal cultures generated plasma membrane fragments with accessible intra-cellular epitopes adapted to measurement of BoNT/A activity. SPR responses were proportional to antigen concentration permitting detection of as little as 4 pM SNAP-25 in crude lysates. BoNT/A activity was assayed using monoclonal antibodies that specifically recognize a SNAP-25 epitope generated by the proteolytic action of the toxin. Incubation of intact primary cultured neurons with BoNT/A yielded an EC{sub 50} of 0.5 pM. The SPR biosensor method was sensitive enough to monitor BoNT/A and B activity in cells cultured in a 96-well format providing an alternative to experimental animals for toxicological assays.

  18. Leveraging electrokinetics for the active control of dendritic fullerene-1 release across a nanochannel membrane

    NASA Astrophysics Data System (ADS)

    Bruno, Giacomo; Geninatti, Thomas; Hood, R. Lyle; Fine, Daniel; Scorrano, Giovanni; Schmulen, Jeffrey; Hosali, Sharath; Ferrari, Mauro; Grattoni, Alessandro

    2015-03-01

    General adoption of advanced treatment protocols such as chronotherapy will hinge on progress in drug delivery technologies that provide precise temporal control of therapeutic release. Such innovation is also crucial to future medicine approaches such as telemedicine. Here we present a nanofluidic membrane technology capable of achieving active and tunable control of molecular transport through nanofluidic channels. Control was achieved through application of an electric field between two platinum electrodes positioned on either surface of a 5.7 nm nanochannel membrane designed for zero-order drug delivery. Two electrode configurations were tested: laser-cut foils and electron beam deposited thin-films, configurations capable of operating at low voltage (<=1.5 V), and power (100 nW). Temporal, reproducible tuning and interruption of dendritic fullerene 1 (DF-1) transport was demonstrated over multi-day release experiments. Conductance tests showed limiting currents in the low applied potential range, implying ionic concentration polarization (ICP) at the interface between the membrane's micro- and nanochannels, even in concentrated solutions (<=1 M NaCl). The ability of this nanotechnology platform to facilitate controlled delivery of molecules and particles has broad applicability to next-generation therapeutics for numerous pathologies, including autoimmune diseases, circadian dysfunction, pain, and stress, among others.General adoption of advanced treatment protocols such as chronotherapy will hinge on progress in drug delivery technologies that provide precise temporal control of therapeutic release. Such innovation is also crucial to future medicine approaches such as telemedicine. Here we present a nanofluidic membrane technology capable of achieving active and tunable control of molecular transport through nanofluidic channels. Control was achieved through application of an electric field between two platinum electrodes positioned on either surface of a 5

  19. Membrane filtration of two sulphonamides in tertiary effluents and subsequent adsorption on activated carbon.

    PubMed

    Hartig, C; Ernst, M; Jekel, M

    2001-11-01

    The adsorption behaviour of two polar organic micropollutants (N-n-butylbenzenesulphonamide and sulphmethoxazole) onto powdered activated carbon (PAC) under competitive conditions prior to and after filtration with a tight ultrafiltration membrane was examined. The sulphonamides were spiked into microfiltered tertiary municipal effluent in microg L(-1) quantities. Ultrafiltration of these effluents resulted in better adsorbability for both the micropollutants and the background organic matter in the permeates compared to the feed waters. This behaviour seems to be caused by a reduced blocking of micropores by lower concentrations of high molecular weight compounds in membrane filtrates. A combined treatment of ultrafiltration prior to adsorption can therefore reduce the carbon demand for potentially harmful micropollutants in effluents.

  20. Antioxidant activity of membrane-fractionated coffee extracts in dependence of the storage conditions

    NASA Astrophysics Data System (ADS)

    Mitev, D.; Peshev, D.; Peev, G.; Peeva, L.

    2016-10-01

    Present paper aims at one of the important aspects of the application of products with antioxidant activity: namely the preservation and change of their properties during the storage in different conditions, as well as their reliable characterisation. The tests of antioxidant properties were conducted with membrane-separated coffee extracts, isolated using a “Microdyn Nadir NP030P” type of commercial nanofiltration membrane (30% retention of NaCl; MWCO∼400). Prepared coffee permeates and retentates were stored 0÷10 days in cool/warm conditions, with/without air access and at different illumination conditions. The kinetics of content changes was evaluated according to Folin-Ciocalteu method of total phenolic/reducing content determination.

  1. Broad spectrum antibacterial and antifungal polymeric paint materials: synthesis, structure-activity relationship, and membrane-active mode of action.

    PubMed

    Hoque, Jiaul; Akkapeddi, Padma; Yadav, Vikas; Manjunath, Goutham B; Uppu, Divakara S S M; Konai, Mohini M; Yarlagadda, Venkateswarlu; Sanyal, Kaustuv; Haldar, Jayanta

    2015-01-28

    Microbial attachment and subsequent colonization onto surfaces lead to the spread of deadly community-acquired and hospital-acquired (nosocomial) infections. Noncovalent immobilization of water insoluble and organo-soluble cationic polymers onto a surface is a facile approach to prevent microbial contamination. In the present study, we described the synthesis of water insoluble and organo-soluble polymeric materials and demonstrated their structure-activity relationship against various human pathogenic bacteria including drug-resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and beta lactam-resistant Klebsiella pneumoniae as well as pathogenic fungi such as Candida spp. and Cryptococcus spp. The polymer coated surfaces completely inactivated both bacteria and fungi upon contact (5 log reduction with respect to control). Linear polymers were more active and found to have a higher killing rate than the branched polymers. The polymer coated surfaces also exhibited significant activity in various complex mammalian fluids such as serum, plasma, and blood and showed negligible hemolysis at an amount much higher than minimum inhibitory amounts (MIAs). These polymers were found to have excellent compatibility with other medically relevant polymers (polylactic acid, PLA) and commercial paint. The cationic hydrophobic polymer coatings disrupted the lipid membrane of both bacteria and fungi and thus showed a membrane-active mode of action. Further, bacteria did not develop resistance against these membrane-active polymers in sharp contrast to conventional antibiotics and lipopeptides, thus the polymers hold great promise to be used as coating materials for developing permanent antimicrobial paint.

  2. Antibacterial activity and in vitro evaluation of the biocompatibility of chitosan-based polysaccharide/polyester membranes.

    PubMed

    Wu, Chin-San; Hsu, Yi-Chiang; Liao, Hsin-Tzu; Cai, Yu-Xuan

    2015-12-10

    The antibacterial activity and biocompatibility of membranes of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and chitosan (CS) (PHBV)/CS) were evaluated in this study. Maleic anhydride (MA)-grafted polyhydroxyalkanoate (PHBV-g-MA) was evaluated as an alternative to PHBV. Mouse tail skin fibroblasts (FBs) were seeded on two series of these films to assess cytocompatibility. Collagen and cell proliferation analyses indicated that PHBV, PHBV-g-MA and their composite membranes were biocompatible with respect to FB proliferation. However, FB proliferation, collagen production and the percentage of normal cells growing on PHBV/CS membranes were greater than those for PHBV-g-MA/CS membranes. Cell-cycle and apoptosis assays by FBs on the PHBV-series membrane samples were not affected by DNA content related to damage; i.e. rapid apoptosis/necrosis was not observed, demonstrating the potential of PHBV/CS or PHBV-g-MA/CS membranes for biomedical material applications. Moreover, CS-based polysaccharide enhanced the Escherichia coli (BCRC 10239) antibacterial activity of the membranes. Membranes of PHBV-g-MA or PHBV containing CS-based polysaccharide had better antibacterial activity.

  3. Exclusion of CD45 inhibits activity of p56lck associated with glycolipid-enriched membrane domains

    PubMed Central

    1996-01-01

    p56lck (Lck) is a lymphoid-specific Src family tyrosine kinase that is critical for T-cell development and activation. Lck is also a membrane protein, and approximately half of the membrane-associated Lck is associated with a glycolipid-enriched membrane (GEM) fraction that is resistant to solubilization by Triton X-100 (TX-100). To compare the membrane-associated Lck present in the GEM and TX-100-soluble fractions of Jurkat cells, Lck from each fraction was immunoblotted with antibody to phosphotyrosine. Lck in the GEM fraction was found to be hyperphosphorylated on tyrosine, and this correlated with a lower kinase specific activity relative to the TX-100-soluble Lck. Peptide mapping and phosphatase diagests showed that the hyperphosphorylation and lower kinase activity of GEM-associated Lck was due to phosphorylation of the regulatory COOH-terminal Tyr505. In addition, we determined that the membrane-bound tyrosine phosphatase CD45 was absent from the GEM fraction. Cells lacking CD45 showed identical phosphorylation of Lck in GEM and TX-100-soluble membranes. We propose that the GEM fraction represents a specific membrane domain present in T-cells, and that the hyperphosphorylation of tyrosine and lower kinase activity of GEM-associated Lck is due to exclusion of CD45 from these domains. Lck associated with the GEM domains may therefore consitute a reservoir of enzyme that can be readily activated. PMID:8978819

  4. Measurement of membrane fusion activity from viral membrane fusion proteins based on a fusion-dependent promoter induction system in insect cells

    PubMed Central

    Slack, J. M.; Blissard, G. W.

    2013-01-01

    Summary A number of viral membrane fusion proteins can be expressed alone on the surface of host cells, then triggered to induce cell-to-cell fusion or syncytium formation. Although rapid and easily observed, syncytium formation is not easily quantified and differences in fusion activity are not easily distinguished or measured. To address this problem, we developed a rapid and quantitative cell-to-cell fusion system that is useful for comparative analysis and may be suitable for high throughput screening. In this system, expression of a reporter protein, the enhanced green fluorescent protein (EGFP), is dependent on cell-to-cell fusion. Spodoptera frugiperda (Sf9) insect cells expressing a chimeric Lac Repressor-IE1 protein were fused to Sf9 cells containing an EGFP reporter construct under the control of a responsive lac operator containing promoter. Membrane fusion efficiency was measured from the resulting EGFP fluorescence activity. Sf9 cells expressing the Orgyia pseudotsugata Multicapsid Nucleopolyhedrovirus (OpMNPV) GP64 envelope fusion protein were used as a model to test this fusion assay. Subtle changes in fusion activities of GP64 proteins containing single amino acid substitutions in a putative membrane fusion domain were distinguished, and decreases in EGFP fluorescence corresponded to decreases in the hydrophobicity in the small putative membrane fusion domain. PMID:11562545

  5. Effect of membrane structure on the action of polyenes II: nystatin activity along the phase diagram of ergosterol- and cholesterol-containing POPC membranes.

    PubMed

    González-Damián, J; Ortega-Blake, I

    2010-09-01

    Pores formed by the polyene antibiotic nystatin were studied in solvent-free lipid membranes. The membranes were formed by the tip-dip technique using 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) with different mol fractions (0-50%) of cholesterol or ergosterol. The effects of the mol fraction of sterol and of temperature variation (15-35°C) on the activity of the pores, their unitary conductances, lifetimes and time average conductances were studied. The results were used to analyze the behavior of nystatin channels along the phase diagrams previously reported for these lipid mixtures and to propose that membrane structure is the determinant factor for the known ergosterol/cholesterol selectivity.

  6. Antibodies Against Membrane Interleukin 1α Activate Accessory Cells to Stimulate Proliferation of T Lymphocytes

    NASA Astrophysics Data System (ADS)

    Eugui, Elsie M.; Almquist, Susan J.

    1990-02-01

    Some monoclonal antibodies (mAbs) against interleukin (IL) 1α have been found to activate antigen-presenting cells (APC, human peripheral blood monocytes and B lymphocytes), so that unstimulated T lymphocytes cultured with them are induced to proliferate and secrete IL-2. Control mAbs of the same isotypes and mAbs against IL-11β do not activate APC. In the absence of APC, mAbs against IL-1α do not induce proliferation of T lymphocytes. Mitomycin C-treated activated APC still induce T-cell proliferation. Proliferation of T lymphocytes cannot be induced by culture supernatants and requires contact with APC activated by mAbs against IL-1α. The observations imply that surface membrane IL-1α can function as a triggering molecule on APC, which could play an important role in the initiation of immune responses by T lymphocytes.

  7. A Placental Polypeptide Activator of a Membranous Protein Kinase and Its Relation to Histone 1

    NASA Astrophysics Data System (ADS)

    Abdel-Ghany, M.; Riegler, C.; Racker, E.

    1984-12-01

    Crude transforming growth factor preparations of placenta contain a polypeptide that is required for the activity of a protein kinase that has been purified from plasma membrane preparations of Ehrlich ascites tumor cells. The kinase activator has been separated from transforming growth factor β by reversed-phase HPLC and affinity chromatography. Like the transforming growth factor, it is heat stable and trypsin labile, but it is not inactivated by dithiothreitol. In sodium dodecyl sulfate/polyacrylamide gel electrophoresis the purified preparation shows a major double band at about 31,000 daltons. Comparisons of electrophoretic mobility, protein kinase stimulatory activity, and cross-reactivity with an antibody against histone 1 suggest that the placental activator is identical with histone 1.

  8. CARBONIC ANHYDRASE ACTIVITY OF INTEGRAL-FUNCTIONAL COMPLEXES OF THYLAKOID MEMBRANES OF SPINACH CHLOROPLASTS.

    PubMed

    Semenihin, A V; Zolotareva, O K

    2015-01-01

    Isolated thylakoid membranes were disrupted by treatment with nonionic detergents digitonin or dodecyl maltoside. Solubilized polypeptide complexes were separated by native gel charge shift electrophoresis. The position of ATP-synthase complex and its isolated catalytic part (CF1) within gel was determined using the color reaction for ATPase activity. Due to the presence of cytochromes, the red band in unstained gels corresponded to the cytochrome b6f complex. Localization of the cytochrome b6f complex, ATP synthase and coupling CF1 in the native gel was confirmed by their subunit composition determined after SDS-electrophoretic analysis. Carbonic anhydrase (CA) activity in polypeptide zones of PS II, cytochrome b6f complex, and ATP-synthase CF1 was identified in native gels using indicator bromothymol blue. CA activity of isolated CF1 in solution was determined by infrared gas analysis as the rate of bicarbonate dehydration. The water-soluble acetazolamide, an inhibitor of CA, unlike lipophilic ethoxyzolamide inhibited CA activity of CF1 Thus, it was shown for the first time that ATP-synthase has a component which is capable of catalyzing the interconversion of forms of carbonic acid associated with proton exchange. The data obtained suggest the presence of multiple forms of carbonic anhydrase in the thylakoid membranes of spinach chloroplasts and confirm their involvement in the proton transfer to the ATP synthase.

  9. Generation, modulation and maintenance of the plasma membrane asymmetric phospholipid composition in yeast cells during growth: their relation to surface potential and membrane protein activity.

    PubMed

    Cerbón, J; Calderón, V

    1995-04-12

    During growth a cyclic exposure of anionic phospholipids to the external surface of the plasma membrane was found. The surface charge density (sigma) increased gradually reaching a maximum in the first 5 h of growth and returned gradually to their initial value at the end of the logarithmic phase of growth (10-12 h). Phosphatidylinositol, that determines to a large extent the magnitude of the sigma, increased 83% in the yeast cells during the first 4 h of growth and returned gradually to their initial level at 10-12 h. During the stationary phase (12-24 h), both sigma and the anionic/zwitterionic phospholipid ratio, remained without any significant variation. The high-affinity H-linked glutamate transport system that behaves as a sensor of the changes in the membrane surface potential (phi) increased its activity in the first 5 h and then decreased it, following with great accuracy the sigma variations and remained without changes during the stationary phase of growth. The phosphatidylserine (PS) relative concentration in the cells (9.0%) did not significantly change during the whole growth curve, but their asymmetric distribution varied, contributing to the changes in sigma. PS facing the outer membrane surface increased 2.45-times during the first 5 h of growth and then returned to their original value at the end of the log phase (12 h). Phosphatidylcholine (PC) remained constant during the whole growth curve (50%), while phosphatidylethanolamine (PE) decreased 3-fold in the first 4 h and then increased to its original value at 10 h. Interestingly, PE at the outer membrane surface remained constant (3% of the total phospholipids) during the whole growth curve. During growth yeast cells change their phospholipid composition originating altered patterns of the plasma membrane phospholipid composition and IN-OUT distribution. This dynamic asymmetry is involved in the regulation of the surface potential and membrane protein activity.

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