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https://www.readbyqxmd.com/read/28424773/septins-focus-cellular-growth-for-host-infection-by-pathogenic-fungi
#1
REVIEW
Michelle Momany, Nicholas J Talbot
One of the key challenges faced by microbial pathogens is invasion of host tissue. Fungal pathogens adopt a number of distinct strategies to overcome host cell defenses, including the development of specialized infection structures, the secretion of proteins that manipulate host responses or cellular organization, and the ability to facilitate their own uptake by phagocytic mechanisms. Key to many of these adaptations is the considerable morphogenetic plasticity displayed by pathogenic species. Fungal pathogens can, for example, shift their growth habit between non-polarized spores, or yeast-like cells, and highly polarized hyphal filaments...
2017: Frontiers in Cell and Developmental Biology
https://www.readbyqxmd.com/read/28417957/attractive-force-driven-superhardening-of-graphene-membranes-as-a-pin-point-breaking-of-continuum-mechanics
#2
Makoto Ashino, Roland Wiesendanger
Bending at the nanometre scale can substantially modify the mechanical, chemical and electronic properties of graphene membranes. The subsequent response of chemical bonds leads to deviations from plate idealisation in continuum mechanics. However, those phenomena have thus far been investigated exclusively by measuring the electronic properties of graphene deformed by compressing and stretching with local-probe techniques. Here, we report that the interatomic-attractive forces applied on the convexly-curved graphene by the probe tip give rise to a pin-point breaking of the plate idealisation in the continuum mechanics, facilitating atomically-localised enhancements in its chemical reactivity and mechanical strength...
April 18, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28411214/achiral-symmetry-breaking-and-positive-gaussian-modulus-lead-to-scalloped-colloidal-membranes
#3
Thomas Gibaud, C Nadir Kaplan, Prerna Sharma, Mark J Zakhary, Andrew Ward, Rudolf Oldenbourg, Robert B Meyer, Randall D Kamien, Thomas R Powers, Zvonimir Dogic
In the presence of a nonadsorbing polymer, monodisperse rod-like particles assemble into colloidal membranes, which are one-rod-length-thick liquid-like monolayers of aligned rods. Unlike 3D edgeless bilayer vesicles, colloidal monolayer membranes form open structures with an exposed edge, thus presenting an opportunity to study elasticity of fluid sheets. Membranes assembled from single-component chiral rods form flat disks with uniform edge twist. In comparison, membranes composed of a mixture of rods with opposite chiralities can have the edge twist of either handedness...
April 14, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28406172/anchored-but-not-internalized-shape-dependent-endocytosis-of-nanodiamond
#4
Bokai Zhang, Xi Feng, Hang Yin, Zhenpeng Ge, Yanhuan Wang, Zhiqin Chu, Helena Raabova, Jan Vavra, Petr Cigler, Renbao Liu, Yi Wang, Quan Li
Nanoparticle-cell interactions begin with the cellular uptake of the nanoparticles, a process that eventually determines their cellular fate. In the present work, we show that the morphological features of nanodiamonds (NDs) affect both the anchoring and internalization stages of their endocytosis. While a prickly ND (with sharp edges/corners) has no trouble of anchoring onto the plasma membrane, it suffers from difficult internalization afterwards. In comparison, the internalization of a round ND (obtained by selective etching of the prickly ND) is not limited by its lower anchoring amount and presents a much higher endocytosis amount...
April 13, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28401231/diverse-morphologies-in-thin-film-bijels-by-varying-film-thickness-and-composition
#5
Joseph M Carmack, Paul C Millett
Thin-film bijels have many potential energy and environmental applications. In this work, the metastable bijel morphology space in thin-film confinement is explored with a Cahn-Hilliard/Brownian-Dynamics computational model. The key parameters varied are the bijel liquid phase blend ratio and the bijel film thickness. Simulations reveal a broad spectrum of structurally unique morphologies that have yet to be observed in experiments and which could have interesting applications in membrane science and other domains...
April 12, 2017: Soft Matter
https://www.readbyqxmd.com/read/28400045/rapid-snare-mediated-fusion-of-liposomes-and-chromaffin-granules-with-giant-unilamellar-vesicles
#6
Agata Witkowska, Reinhard Jahn
Soluble N-ethylmaleimide-sensitive factor activating protein receptor (SNARE) proteins are the main catalysts for membrane fusion in the secretory pathway of eukaryotic cells. In vitro, SNAREs are sufficient to mediate effective fusion of both native and artificial membranes. Here we have established, to our knowledge, a new platform for monitoring SNARE-mediated docking and fusion between giant unilamellar vesicles (GUVs) and smaller liposomes or purified secretory granules with high temporal and spatial resolution...
April 8, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28382709/computational-prediction-of-the-optimal-oligomeric-state-for-membrane-inserted-%C3%AE-barrels-of-protegrin-1-and-related-mutants
#7
Richard Lipkin, Themis Lazaridis
Protegrin-1 is a widely studied 18-residue β-hairpin antimicrobial peptide. Evidence suggests that it acts via a β-barrel pore formation mechanism, but the exact number of peptides comprising the pore state is unknown. In this study, we performed molecular dynamics simulations of β-barrels of protegrin and three related mutants (v14v16l, v14v16a, and r4n) in NCNC parallel topology in implicit membrane pores of varying radius and curvature for oligomeric numbers 6-14. We then identified the optimal pore radius and curvature values for all constructs and determined the total effective energy and the translational and rotational entropic losses...
April 2017: Journal of Peptide Science: An Official Publication of the European Peptide Society
https://www.readbyqxmd.com/read/28381413/photoreceptor-discs-form-through-peripherin-dependent-suppression-of-ciliary-ectosome-release
#8
Raquel Y Salinas, Jillian N Pearring, Jin-Dong Ding, William J Spencer, Ying Hao, Vadim Y Arshavsky
The primary cilium is a highly conserved organelle housing specialized molecules responsible for receiving and processing extracellular signals. A recently discovered property shared across many cilia is the ability to release small vesicles called ectosomes, which are used for exchanging protein and genetic material among cells. In this study, we report a novel role for ciliary ectosomes in building the elaborate photoreceptor outer segment filled with hundreds of tightly packed "disc" membranes. We demonstrate that the photoreceptor cilium has an innate ability to release massive amounts of ectosomes...
April 5, 2017: Journal of Cell Biology
https://www.readbyqxmd.com/read/28379629/characterization-of-plasma-membrane-ceramides-by-super-resolution-microscopy
#9
Anne Burgert, Jan Schlegel, Jérôme Bécam, Sören Doose, Erhard Bieberich, Alexandra Schubert-Unkmeir, Markus Sauer
The sphingolipid ceramide regulates cellular processes such as differentiation, proliferation, growth arrest, and apoptosis. Ceramide-rich membrane areas promote structural changes within the plasma membrane that segregate membrane receptors and affect membrane curvature and vesicle formation, fusion, and trafficking. Ceramides were labeled by immunocytochemistry to visualize their distribution on the plasma membrane of different cells with virtually molecular resolution by direct stochastic optical reconstruction microscopy (dSTORM)...
April 5, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28373566/membrane-fission-by-protein-crowding
#10
Wilton T Snead, Carl C Hayden, Avinash K Gadok, Chi Zhao, Eileen M Lafer, Padmini Rangamani, Jeanne C Stachowiak
Membrane fission, which facilitates compartmentalization of biological processes into discrete, membrane-bound volumes, is essential for cellular life. Proteins with specific structural features including constricting rings, helical scaffolds, and hydrophobic membrane insertions are thought to be the primary drivers of fission. In contrast, here we report a mechanism of fission that is independent of protein structure-steric pressure among membrane-bound proteins. In particular, random collisions among crowded proteins generate substantial pressure, which if unbalanced on the opposite membrane surface can dramatically increase membrane curvature, leading to fission...
April 3, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28336315/cardiolipin-and-mitochondrial-cristae-organization
#11
REVIEW
Nikita Ikon, Robert O Ryan
A fundamental question in cell biology, under investigation for over six decades, is the structural organization of mitochondrial cristae. Long known to harbor electron transport chain proteins, crista membrane integrity is key to establishment of the proton gradient that drives oxidative phosphorylation. Visualization of cristae morphology by electron microscopy/tomography has provided evidence that cristae are tube-like extensions of the mitochondrial inner membrane (IM) that project into the matrix space...
March 20, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28335714/testis-specific-atp-synthase-peripheral-stalk-subunits-required-for-tissue-specific-mitochondrial-morphogenesis-in-drosophila
#12
Eric M Sawyer, Elizabeth C Brunner, Yihharn Hwang, Lauren E Ivey, Olivia Brown, Megan Bannon, Dennis Akrobetu, Kelsey E Sheaffer, Oshauna Morgan, Conroy O Field, Nishita Suresh, M Grace Gordon, E Taylor Gunnell, Lindsay A Regruto, Cricket G Wood, Margaret T Fuller, Karen G Hales
BACKGROUND: In Drosophila early post-meiotic spermatids, mitochondria undergo dramatic shaping into the Nebenkern, a spherical body with complex internal structure that contains two interwrapped giant mitochondrial derivatives. The purpose of this study was to elucidate genetic and molecular mechanisms underlying the shaping of this structure. RESULTS: The knotted onions (knon) gene encodes an unconventionally large testis-specific paralog of ATP synthase subunit d and is required for internal structure of the Nebenkern as well as its subsequent disassembly and elongation...
March 23, 2017: BMC Cell Biology
https://www.readbyqxmd.com/read/28325841/an-inducible-amphipathic-helix-within-the-intrinsically-disordered-c-terminus-is-not-required-for-protein-biosynthesis-trafficking-or-garp2-interaction-but-can-participate-in-membrane-curvature-generation-by-peripherin-2-rds
#13
Michelle L Milstein, Victoria A Kimler, Chiranjib Ghatak, Alexey S Ladokhin, Andrew F X Goldberg
Peripherin-2/rds is required for biogenesis of vertebrate photoreceptor outer segment organelles. Its localization at the high curvature rim domains of outer segment disk membranes suggests that it may act to shape these structures; however, the molecular function of this protein is not yet resolved. Here, we apply biochemical, biophysical, and imaging techniques, to elucidate the role(s) played by the protein's intrinsically disordered C-terminal domain, and an incipient amphipathic α-helix contained within it...
March 21, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28322223/origins-of-chemoreceptor-curvature-sorting-in-escherichia-coli
#14
Will Draper, Jan Liphardt
Bacterial chemoreceptors organize into large clusters at the cell poles. Despite a wealth of structural and biochemical information on the system's components, it is not clear how chemoreceptor clusters are reliably targeted to the cell pole. Here, we quantify the curvature-dependent localization of chemoreceptors in live cells by artificially deforming growing cells of Escherichia coli in curved agar microchambers, and find that chemoreceptor cluster localization is highly sensitive to membrane curvature. Through analysis of multiple mutants, we conclude that curvature sensitivity is intrinsic to chemoreceptor trimers-of-dimers, and results from conformational entropy within the trimer-of-dimers geometry...
March 21, 2017: Nature Communications
https://www.readbyqxmd.com/read/28321192/quantifying-the-frictional-forces-between-skin-and-nonwoven-fabrics
#15
Kavinda Jayawardana, Nicholas C Ovenden, Alan Cottenden
When a compliant sheet of material is dragged over a curved surface of a body, the frictional forces generated can be many times greater than they would be for a planar interface. This phenomenon is known to contribute to the abrasion damage to skin often suffered by wearers of incontinence pads and bed/chairbound people susceptible to pressure sores. Experiments that attempt to quantify these forces often use a simple capstan-type equation to obtain a characteristic coefficient of friction. In general, the capstan approach assumes the ratio of applied tensions depends only on the arc of contact and the coefficient of friction, and ignores other geometric and physical considerations; this approach makes it straightforward to obtain explicitly a coefficient of friction from the tensions measured...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/28317901/membrane-remodeling-by-the-m2-amphipathic-helix-drives-influenza-virus-membrane-scission
#16
Agnieszka Martyna, Basma Bahsoun, Matthew D Badham, Saipraveen Srinivasan, Mark J Howard, Jeremy S Rossman
Membrane scission is a crucial step in all budding processes, from endocytosis to viral budding. Many proteins have been associated with scission, though the underlying molecular details of how scission is accomplished often remain unknown. Here, we investigate the process of M2-mediated membrane scission during the budding of influenza viruses. Residues 50-61 of the viral M2 protein bind membrane and form an amphipathic α-helix (AH). Membrane binding requires hydrophobic interactions with the lipid tails but not charged interactions with the lipid headgroups...
March 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28300412/reconciling-differences-between-lipid-transfer-in-free-standing-and-solid-supported-membranes-a-time-resolved-small-angle-neutron-scattering-study
#17
Benny Wah, Jeffrey M Breidigan, Joseph Adams, Piotr Horbal, Sumit Garg, Lionel Porcar, Ursula Perez-Salas
Maintaining compositional lipid gradients across membranes in animal cells is essential to biological function, but what is the energetic cost to maintain these differences? It has long been recognized that studying the passive movement of lipids in membranes can provide insight into this toll. Confusingly the reported values of inter- and, particularly, intra-lipid transport rates of lipids in membranes show significant differences. To overcome this difficulty, biases introduced by experimental approaches have to be identified...
March 29, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28298095/membrane-stress-profiles-from-self-consistent-field-theory
#18
Christina L Ting, Marcus Müller
Using self-consistent field theory (SCFT), we develop an accurate, local expression for the stress profiles in membranes and soft matter interfaces, in general. The bond stresses are expressed in terms of pre-computed chain propagators, which are used to describe the statistical weight of the molecules and therefore require minimal additional calculations. In addition, we overcome the resolution limit of the molecular bond length by including the Irving and Kirkwood bond assignment and recover a constant normal stress profile across an interface...
March 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28298093/erratum-membrane-curvature-generated-by-asymmetric-depletion-layers-of-ions-small-molecules-and-nanoparticles-j-chem-phys-145-074117-2016
#19
Bartosz Różycki, Reinhard Lipowsky
No abstract text is available yet for this article.
March 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28294967/single-lipid-molecule-dynamics-on-supported-lipid-bilayers-with-membrane-curvature
#20
Philip P Cheney, Alan W Weisgerber, Alec M Feuerbach, Michelle K Knowles
The plasma membrane is a highly compartmentalized, dynamic material and this organization is essential for a wide variety of cellular processes. Nanoscale domains allow proteins to organize for cell signaling, endo- and exocytosis, and other essential processes. Even in the absence of proteins, lipids have the ability to organize into domains as a result of a variety of chemical and physical interactions. One feature of membranes that affects lipid domain formation is membrane curvature. To directly test the role of curvature in lipid sorting, we measured the accumulation of two similar lipids, 1,2-Dihexadecanoyl-sn-glycero-3-phosphoethanolamine (DHPE) and hexadecanoic acid (HDA), using a supported lipid bilayer that was assembled over a nanopatterned surface to obtain regions of membrane curvature...
March 15, 2017: Membranes
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