The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform
John E Heuser - One of the best experts on this subject based on the ideXlab platform.
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deep etch em reveals that the early poxvirus envelope is a single Membrane Bilayer stabilized by a geodetic honeycomb surface coat
Journal of Cell Biology, 2005Co-Authors: John E HeuserAbstract:Three-dimensional “deep-etch” electron microscopy (DEEM) resolves a longstanding controversy concerning poxvirus morphogenesis. By avoiding fixative-induced Membrane distortions that confounded earlier studies, DEEM shows that the primary poxvirus envelope is a single Membrane Bilayer coated on its external surface by a continuous honeycomb lattice. Freeze fracture of quick-frozen poxvirus-infected cells further shows that there is only one fracture plane through this primary envelope, confirming that it consists of a single lipid Bilayer. DEEM also illustrates that the honeycomb coating on this envelope is completely replaced by a different paracrystalline coat as the poxvirus matures. Correlative thin section images of infected cells freeze substituted after quick-freezing, plus DEEM imaging of Tokuyasu-type cryo-thin sections of infected cells (a new application introduced here) all indicate that the honeycomb network on immature poxvirus virions is sufficiently continuous and organized, and tightly associated with the envelope throughout development, to explain how its single lipid Bilayer could remain stable in the cytoplasm even before it closes into a complete sphere.
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deep etch em reveals that the early poxvirus envelope is a single Membrane Bilayer stabilized by a geodetic honeycomb surface coat
Journal of Cell Biology, 2005Co-Authors: John E HeuserAbstract:Three-dimensional “deep-etch” electron microscopy (DEEM) resolves a longstanding controversy concerning poxvirus morphogenesis. By avoiding fixative-induced Membrane distortions that confounded earlier studies, DEEM shows that the primary poxvirus envelope is a single Membrane Bilayer coated on its external surface by a continuous honeycomb lattice. Freeze fracture of quick-frozen poxvirus-infected cells further shows that there is only one fracture plane through this primary envelope, confirming that it consists of a single lipid Bilayer. DEEM also illustrates that the honeycomb coating on this envelope is completely replaced by a different paracrystalline coat as the poxvirus matures. Correlative thin section images of infected cells freeze substituted after quick-freezing, plus DEEM imaging of Tokuyasu-type cryo-thin sections of infected cells (a new application introduced here) all indicate that the honeycomb network on immature poxvirus virions is sufficiently continuous and organized, and tightly associated with the envelope throughout development, to explain how its single lipid Bilayer could remain stable in the cytoplasm even before it closes into a complete sphere.
Patrick Williamson - One of the best experts on this subject based on the ideXlab platform.
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Phospholipid Scramblases.
Lipid insights, 2016Co-Authors: Patrick WilliamsonAbstract:The distribution of phospholipid types between the two leaflets of a Membrane Bilayer is a controlled feature of Membrane structure. One of the two Membrane catalytic activities governing this distribution randomizes the composition of the two leaflets-the phospholipid scramblases. Two proteins (Xkr8 and TMEM16F) required for the activation of these activities have been identified. One of these proteins (TMEM16F) is quite clearly a scramblase itself and provides insight into the mechanism by which transBilayer phospholipid movement is facilitated.
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phospholipid scramblase an update
FEBS Letters, 2010Co-Authors: Edouard M. Bevers, Patrick WilliamsonAbstract:The best understood consequence of the collapse of lipid asymmetry is exposure of phosphatidylserine (PS) in the external leaflet of the plasma Membrane Bilayer, where it is known to serve at least two major functions: providing a platform for development of the blood coagulation cascade and presenting the signal that induces phagocytosis of apoptotic cells. Lipid asymmetry is collapsed by activation of phospholipid scramblase(s) that catalyze bidirectional transBilayer movement of the major classes of phospholipid. The protein corresponding to this activity is not yet known. Observations on cells from patients with Scott syndrome, a rare hereditary bleeding disorder resulting from impaired lipid scrambling, have shown that there are multiple activation pathways that converge on scramblase activity.
Alexandros Makriyannis - One of the best experts on this subject based on the ideXlab platform.
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The conformation, location, and dynamic properties of the endocannabinoid ligand anandamide in a Membrane Bilayer.
The Journal of biological chemistry, 2005Co-Authors: Xiaoyu Tian, Jianxin Guo, Fen‐mei Yao, De-ping Yang, Alexandros MakriyannisAbstract:The endogenous cannabinoid ligand anandamide is biosynthesized from Membrane phospholipid precursors and is believed to reach its sites of action on the CB1 and CB2 receptors through fast lateral diffusion within the cell Membrane. To gain a better insight on the stereochemical features of its association with the cell Membrane and its interaction with the cannabinoid receptors, we have studied its conformation, location, and dynamic properties in a dipalmitoylphosphatidylcholine multilamellar model Membrane Bilayer system. By exploiting the Bilayer lattice as an internal three-dimensional reference grid, the conformation and location of anandamide were determined by measuring selected inter- and intramolecular distances between strategically introduced isotopic labels using the rotational echo double resonance (REDOR) NMR method. A molecular model was proposed to represent the structural features of our anandamide/lipid system and was subsequently used in calculating the multispin dephasing curves. Our results demonstrate that anandamide adopts an extended conformation within the Membrane with its headgroup at the level of the phospholipid polar group and its terminal methyl group near the Bilayer center. Parallel static (2)H NMR experiments further confirmed these findings and provided evidence that anandamide experiences dynamic properties similar to those of the Membrane phospholipids and produces no perturbation to the Bilayer. Our results are congruent with a hypothesis that anandamide approaches its binding site by laterally diffusing within one Membrane leaflet in an extended conformation and interacts with a hydrophobic groove formed by helices 3 and 6 of CB1, where its terminal carbon is positioned close to a key cysteine residue in helix 6 leading to receptor activation.
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Small angle X-ray diffraction and differential scanning calorimetric studies on O-methyl-(−)-Δ8-tetrahydrocannabinol and its 5′ iodinated derivative in Membrane Bilayers
Biochimica et biophysica acta, 1995Co-Authors: Thomas Mavromoustakos, De-ping Yang, Alexandros MakriyannisAbstract:Abstract We have previously studied and compared the location of (−)-Δ8-tetrahydrocannabinol (Δ8-THC) with that of O-methyl-Δ8-THC (Me-Δ8-THC) in the Membrane using partially hydrated dimyristoylphosphatidylcholine (DMPC) Bilayers ((Mavromoustakos et al. (1990) Biophys. Acta 1024, 336–344; Yang et al. (1993) Life Sci. 53, 117–122). Δ8-THC was found to be located near the Membrane interface with its phenolic hydroxyl group anchored near the carbonyl groups of DMPC while the more lipophilic Me-Δ8-THC is located deeper in the Membrane Bilayer. Parallel experiments using Me-Δ8-THC and its 5′-iodo analog (5′-I-Me-Δ8-THC allowed us to determine the topography of these two molecules in the Bilayer. Our results from small angle X-ray diffraction and differential scanning calorimetry (DSC) combined with previous data on the orientation of Me-Δ8-THC in model Membranes, led us to the conclusion that these molecules intercalate between contiguous acyl chains in the lipophilic moiety of the Membrane Bilayer. The terminal iodo group in 5′-IMe-Δ8-THC was found to reside in a region extending approx. ± 5 A from the center of the Bilayers. The location of Me-Δ8-THC in the Membranes as well as its orientation may explain its inability to effectively perturb the Bilayer lipid chains.
Nicolas S. Shu - One of the best experts on this subject based on the ideXlab platform.
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Structural Evolution and Membrane Interaction of the 40-Residue β Amyloid Peptides: Differences in the Initial Proximity between Peptides and the Membrane Bilayer Studied by Solid-State Nuclear Magnetic Resonance Spectroscopy
Biochemistry, 2014Co-Authors: Wei Qiang, Rumonat D. Akinlolu, Mimi Nam, Nicolas S. ShuAbstract:Interactions between the β amyloid (Aβ) peptides and cellular Membranes have severe consequences such as neuronal cell disruption and therefore may play important roles in Alzheimer’s disease. Understanding the structural basis behind such interactions, however, is hindered by the complexity of the Aβ–Membrane systems. In particular, because the Aβ peptides are partially incorporated in the Membrane Bilayer after enzymatic cleavage, there are multiple possibilities in terms of the initial proximity between the peptides and Membranes. Structural studies using in vitro model systems with either externally added or preincorporated Aβ in Membrane Bilayers resulted in distinct evolution pathways. Previous work has shown that the externally added Aβ formed long and mature filaments, while preincorporated Aβ generated short and curvy fibrils. In this study, we perform detailed characterizations on the structural evolution and Membrane interaction for these two pathways, using a combination of solid-state nuclear...
F. Separovic - One of the best experts on this subject based on the ideXlab platform.
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Solid-state NMR study of antimicrobial peptides from Australian frogs in phospholipid Membranes
European Biophysics Journal, 2004Co-Authors: M. S. Balla, J. H. Bowie, F. SeparovicAbstract:Antimicrobial peptides, isolated from the dorsal glands of Australian tree frogs, possess a wide spectrum of biological activity and some are specific to certain pathogens. These peptides have the capability of disrupting bacterial Membranes and lysing lipid Bilayers. This study focused on the following amphibian peptides: (1) aurein 1.2, a 13-residue peptide; (2) citropin 1.1, with 16 residues; and (3) maculatin 1.1, with 21 residues. The antibiotic activity and structure of these peptides have been studied and compared and possible mechanisms by which the peptides lyse bacterial Membrane cells have been proposed. The peptides adopt amphipathic α-helical structures in the presence of lipid micelles and vesicles. Specifically^ 15N-labelled peptides were studied using solid-state NMR to determine their structure and orientation in model lipid Bilayers. The effect of these peptides on phospholipid Membranes was determined by^ 2H and ^31P solid-state NMR techniques in order to understand the mechanisms by which they exert their biological effects that lead to the disruption of the bacterial cell Membrane. Aurein 1.2 and citropin 1.1 are too short to span the Membrane Bilayer while the longer maculatin 1.1, which may be flexible due to the central proline, would be able to span the Bilayer as a transMembrane α-helix. All three peptides had a peripheral interaction with phosphatidylcholine Bilayers and appear to be located in the aqueous region of the Membrane Bilayer. It is proposed that these antimicrobial peptides have a "detergent"-like mechanism of Membrane lysis.