3,313 research outputs found
Wellesly Sh. W. to Mr. James Meredith (2 October 1962)
Full text linkSigned by Wellesly Sh. W.https://egrove.olemiss.edu/mercorr_pro/1531/thumbnail.jp
SMA-SH: Modified styrene maleic acid copolymer for functionalization of lipid nanodiscs
No full textChallenges in purification and subsequent functionalization of membrane proteins often complicate their biochemical and biophysical characterization. Purification of membrane proteins generally involves replacing the lipids surrounding the protein with detergent molecules, which can affect protein structure and function. Recently, it was shown that styrene–maleic acid copolymers (SMA) can dissolve integral membrane proteins from biological membranes into nanosized discs. Within these nanoparticles, proteins are embedded in a patch of their native lipid bilayer that is stabilized in solution by the amphipathic polymer that wraps the disc like a bracelet. This approach for detergent-free purification of membrane proteins has the potential to greatly simplify purification but does not facilitate conjugation of functional compounds to the membrane proteins. Often, such functionalization involves laborious preparation of protein variants and optimization of labeling procedures to ensure only minimal perturbation of the protein. Here, we present a strategy that circumvents several of these complications through modifying SMA by grafting the polymer with cysteamine. The reaction results in SMA that has solvent-exposed sulfhydrils (SMA-SH) and allows tuning of the coverage with SH groups. Size exclusion chromatography, dynamic light scattering, and transmission electron microscopy demonstrate that SMA-SH dissolves lipid bilayer membranes into lipid nanodiscs, just like SMA. In addition, we demonstrate that, just like SMA, SMA-SH solubilizes proteoliposomes into protein-loaded nanodiscs. We covalently modify SMA-SH-lipid nanodiscs using thiol-reactive derivatives of Alexa Fluor 488 and biotin. Thus, SMA-SH promises to simultaneously tackle challenges in purification and functionalization of membrane proteins.BN/Marie-Eve Aubin-Tam LabBN/Andreas Engel La
Omega-3 fatty acid eicospentaenoic acid attenuates MPP+-induced neurodegeneration in fully differentiated human SH- SY5Y and primary mesencephalic cells
No full textEicosapentaenoic acid ( EPA), a neuroactive omega-3 fatty acid, has been demonstrated to exert neuroprotective effects in experimental models of Parkinson's disease ( PD), but the cellular mechanisms of protection are unknown. Here, we studied the effects of EPA in fully differentiated human SH-SY5Y cells and primary mesencephalic neurons treated with MPP+. In both in-vitro models of PD, EPA attenuated an MPP+-induced reduction in cell viability. EPA also prevented the presence of electron-dense cytoplasmic inclusions in SH-SY5Y cells. Then, possible mechanisms of the neuroprotection were studied. In primary neurons, EPA attenuated an MPP+-induced increase in Tyrosine-related kinase B (TrkB) receptors. In SH-SY5Y cells, EPA down-regulated reactive oxygen species and nitric oxide. This antioxidant effect of EPA may have been mediated by its inhibition of neuronal NADPH oxidase and cyclo-oxygenase-2 ( COX-2), as MPP+ increased the expression of these enzymes. Furthermore, EPA prevented an increase in cytosolic phospholipase A2 ( cPLA2), an enzyme linked with COX-2 in the potentially pro-inflammatory arachidonic acid cascade. Lastly, EPA attenuated an increase in the bax:bcl-2 ratio, and cytochrome c release. However, EPA did not prevent mitochondrial enlargement or a decrease in mitochondrial membrane potential. This study demonstrated cellular mechanisms by which EPA provided neuroprotective effects in experimental P
Effects of Na Neutralization Level on the SH Behaviour after Ballistic Tests of EMAA Based Ionomers
No full textEthylene-co-methacrylic acid (EMAA) based ionomers have thermo-mechanical properties strongly dependent on neutralization level of acid groups. Research revealed also how these materials are able to heal after ballistic impacts. In order to better understand the role of neutralization level on the Self-Healing (SH) behaviour, mechanical and ballistic tests on EMAA copolymers, neutralized with different amount of Na ions, were performed in different experimental conditions. The SH capability was studied by shooting bullets at low velocity (180 m/s) and mid velocity (400 m/s); different testing conditions such as sample thickness and bullet diameter were examined. In all impact tests, spherical projectiles were used. These experiments allowed to define a critical ratio between sample thickness and bullet diameter below which the SH behaviour does not appear. After ballistic damage, the healing efficiency was evaluated by applying a pressure difference through tested samples. Subsequently, morphology analysis of the impacted areas was made observing all tested samples by Scanning Electron Microscope (SEM). These analysis revealed different characteristic features in the damaged zones of tested polymers impacted at different projectile speed. Obtained results show how the Na ions content influences the SH capability; in particular the EMAA copolymer with the highest Na neutralization level does not show a complete hole closure after low velocity impact test. Conversely, increasing projectile speed, all the polymers exhibit nearly the same SH behaviour
Low airspeed systems for the naval SH-60 Seahawk aircraft
Full text linkPitot-static systems have long been used to measure helicopter airspeed. The Pitot-static system is inaccurate at low airspeeds (below 40 knots) due to the limited sensitivity of the sensor and interference of rotor down wash. Additionally, the Pitot-static system only measures unidirectional airspeed and unlike its fixed wing counterparts the helicopter is not limited to flight in one direction. With the changing roles of the US Navy Seahawk it is imperative that the pilot and aircrew have all the information necessary to safely complete the mission and prolong the life of the aircraft and dynamic components. With the addition of a dipping sonar to the remanufactured SH-60B aircraft (designated SH- 60R) and the conduct of combat search and rescue mission in the Navy\u27s Seahawks the aircraft will spend more time in a hover and will be flown more aggressively than in the past. This thesis examiness the advantages of incorporating a low airspeed system into the modem helicopter, in particular the SH-60 Seahawk. The author examines the low airspeed sensors and systems currently available and gives a brief description of each system\u27s operation. The author examines the challenges of installing a low airspeed sensor onto the SH-60 Seahawk. The author has determined that either a laser velocimeter or an analytical neural network system would be the best approach for a low airspeed system for the SH-60 Seahawk. The author recommends a combined approach be taken to develop both the laser velocimeter and analytical neural network, and incorporate the best system after further flight testing
ω-3 fatty acid eicosapentaenoic acid attenuates MPP+-induced neurodegeneration in fully differentiated human SH-SY5Y and primary mesencephalic cells
No full textEicosapentaenoic acid (EPA), a neuroactive omega-3 fatty acid, has been demonstrated to exert neuroprotective effects in experimental models of Parkinson's disease (PD), but the cellular mechanisms of protection are unknown. Here, we studied the effects of EPA in fully differentiated human SH-SY5Y cells and primary mesencephalic neurons treated with MPP(+) . In both in-vitro models of PD, EPA attenuated an MPP(+) -induced reduction in cell viability. EPA also prevented the presence of electron-dense cytoplasmic inclusions in SH-SY5Y cells. Then, possible mechanisms of the neuroprotection were studied. In primary neurons, EPA attenuated an MPP(+) -induced increase in Tyrosine-related kinase B (TrkB) receptors. In SH-SY5Y cells, EPA down-regulated reactive oxygen species and nitric oxide. This antioxidant effect of EPA may have been mediated by its inhibition of neuronal NADPH oxidase and cyclo-oxygenase-2 (COX-2), as MPP(+) increased the expression of these enzymes. Furthermore, EPA prevented an increase in cytosolic phospholipase A2 (cPLA2), an enzyme linked with COX-2 in the potentially pro-inflammatory arachidonic acid cascade. Lastly, EPA attenuated an increase in the bax:bcl-2 ratio, and cytochrome c release. However, EPA did not prevent mitochondrial enlargement or a decrease in mitochondrial membrane potential. This study demonstrated cellular mechanisms by which EPA provided neuroprotective effects in experimental PD.
(© 2012 The Authors Journal of Neurochemistry © 2012 International Society for Neurochemistry.
ω-3 fatty acid eicosapentaenoic acid attenuates MPP+-induced neurodegeneration in fully differentiated human SH-SY5Y and primary mesencephalic cells.
No full textEicosapentaenoic acid (EPA), a neuroactive omega-3 fatty acid, has been demonstrated to exert neuroprotective effects in experimental models of Parkinson's disease (PD), but the cellular mechanisms of protection are unknown. Here, we studied the effects of EPA in fully differentiated human SH-SY5Y cells and primary mesencephalic neurons treated with MPP(+) . In both in-vitro models of PD, EPA attenuated an MPP(+) -induced reduction in cell viability. EPA also prevented the presence of electron-dense cytoplasmic inclusions in SH-SY5Y cells. Then, possible mechanisms of the neuroprotection were studied. In primary neurons, EPA attenuated an MPP(+) -induced increase in Tyrosine-related kinase B (TrkB) receptors. In SH-SY5Y cells, EPA down-regulated reactive oxygen species and nitric oxide. This antioxidant effect of EPA may have been mediated by its inhibition of neuronal NADPH oxidase and cyclo-oxygenase-2 (COX-2), as MPP(+) increased the expression of these enzymes. Furthermore, EPA prevented an increase in cytosolic phospholipase A2 (cPLA2), an enzyme linked with COX-2 in the potentially pro-inflammatory arachidonic acid cascade. Lastly, EPA attenuated an increase in the bax:bcl-2 ratio, and cytochrome c release. However, EPA did not prevent mitochondrial enlargement or a decrease in mitochondrial membrane potential. This study demonstrated cellular mechanisms by which EPA provided neuroprotective effects in experimental PD
THEORETICAL INVESTIGATIONS OF THE LIFETIME OF SH in SH and SH
No full textAuthor Institution: Department of Chemistry, The Ohio State UniversityThe state SH molecule provides a prototypical system through which the effect of dimer formation on predissociation dynamics can be investigated. In the gas phase, them is a crossing between this state and the repulsive state at above the vibrational ground state of the diatomic, resulting in the observed lifetime of 1 ns. In recent experiments, Carter and Miller observed that the lifetime is increased by as much as three orders of magnitude when SH is in a dimer with Ar or Kr. Further, the lifetime is found to be sensitive to the intermolecular state of the dimer that is accessed. In this talk we will present results of our work in modeloing these experimental results, using the empirical potential surfaces for the SH and SH dimers developed by Korambath and Hayes. We find a simple ballistic model explains many of the experimental trends. Results for approximate quantum calculations of the lifetimes will also be presented
SH-STRETCHING INTENSITIES AND INTRAMOLECULAR HYDROGEN BONDING IN ALKANETHIOLS
No full textAuthor Institution: Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand; Department of Chemistry and Biochemistry and CIRES, University of Colorado, Campus Box 215, Boulder, CO 80309The SH-stretching overtone transitions of tert-butylthiol and ethanethiol are observed using FT-IR, NIR and photoacoustic spectroscopies. The intensities of these are compared with OH-stretching overtones from the corresponding alcohols. We explain the paucity of SH-stretching intensity using an anharmonic oscillator local mode model. SH- and OH-stretching overtone spectra of 1,2-ethanedithiol and 2-mercaptoethanol are recorded to observe the different effects that hydrogen bonding involving SH - - - S, SH - - - O and OH - - - S have on the spectra. We discuss these effects with the help of high level ab initio calculations
Vibrational Analysis of the transition of SH Complexes (Rg = Ne, Ar and Kr)
No full textAuthor Institution: Laser Spectroscoy Facility, Department of Chemistry, The Ohio State UniversityThe LIF spectra of Rg SH complexes have been observed. Vibrational analysis of these spectra indicates that in Ne SH, most of observed bands are transitions to the internal rotational levels of the state. In SH and SH, we observed both pure van der Waals stretch bands and bend-stretch combination bands. Based on the isotopic shift between SH and SH, we are able to determine the absolute vibrational assignment of most observed SH bands. The details of analysis will be presented
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