Molecular motors on lipid bilayers and silicon dioxide: different driving forces for adsorption

The control of the aggregation of biomedical nanoparticles (NP) in physiological conditions is crucial as clustering may change completely the way they interact with the biological environment. Here we show that Au nanoparticles, functionalized by an anionic, amphiphilic shell, with an overall diameter of 7 nm, spontaneously aggregate in fluid zwitterionic lipid bilayers. We use Molecular Dynamics and enhanced sampling techniques to disentangle the short-range and long-range driving forces of aggregation. At short inter-particle distances, ion-mediated, charge-charge interactions (ion bridging) stabilize the formation of large NP aggregates, as confirmed by cryo-electron microscopy. Lipid depletion and membrane curvature are the main membrane deformations driving long-range NP-NP attraction. Ion bridging, lipid depletion, and membrane curvature stem from the configurational flexibility of the nanoparticle shell. Our simulations show, more in general, that the aggregation of same-charge membrane inclusions can be expected as a result of intrinsically nanoscale effects taking place at the NP-NP and NP-bilayer soft interfaces.

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UNC-10/SYD-2 complex is sufficient to link kinesin-3 to RAB-3 containing synaptic vesicles in the absence of the motor’s PH domain

10.1101/723247 ◽

2019 ◽

Author(s):

Prerana Bhan ◽

Odvogmed Bayansan ◽

Chien-Yu Chang ◽

Syed Nooruzuha Barmaver ◽

Oliver Ingvar Wagner

Keyword(s):

Lipid Bilayers ◽

Molecular Motors ◽

Synaptic Vesicles ◽

Protein Transport ◽

Neurological Diseases ◽

Specific Interaction ◽

New Drugs ◽

Bimolecular Fluorescence Complementation ◽

Protein Accumulation ◽

Ph Domain

ABSTRACTKinesin-3 KIF1A (UNC-104 in C. elegans) is the major fast axonal transporter of STVs (synaptic vesicle protein transport vesicles) containing synaptic precursors such as RAB3A (RAB-3) or VAMP2 (SNB-1). Heritable mutations in neuronal motor proteins (and their adaptors) lead to numerous neurodegenerative diseases. The C-terminal PH (pleckstrin homolog) domain of kinesin-3 UNC-104 directly binds to phosphatidylinositol 4,5-bisphosphates that form the lipid bilayers of STVs. We hypothesized that RAB-3-bound STVs employ a dual linker UNC-10/SYD-2 (RIMS1/liprin-α in mammals) acting as a UNC-104 receptor. This tripartite RAB-3/UNC-10/SYD-2 complex would also act as an additional linker to strengthen the motor-lipid interaction. RT-PCR and Western blot experiments favor a genetic relation between SYD-2, UNC-10 and RAB-3. Co-immunoprecipitation assays revealed changes in binding affinities between SYD-2 and UNC-104 depending on the presence or absence of UNC-10 and RAB-3. Bimolecular fluorescence complementation (BiFC) assays revealed in situ interaction changes between SYD-2 and UNC-104 in either unc-10 or rab-3 mutants. Neuronal expression of UNC-104 appears to be more diffused and is restricted to travel short distances with significantly reduced speeds in these mutants. Though both SNB-1 and RAB-3 are actively transported by UNC-104, the movement of RAB-3 is generally enhanced and largely depending on the presence of the dual linker. Strikingly, the deletion of UNC-104’s PH domain did not affect UNC-104/RAB-3 colocalization but did affect UNC-104/SNB-1 colocalization. These findings solidly support the model of a dual UNC-10/SYD-2 linker acting as a sufficient buttress to connect the motor to RAB-3-containing STVs to enhance their transport.SCIENTIFIC STATEMENTThe interaction between molecular motors and their membranous vesicular cargoes is generally specific. However, for the major axonal transporter kinesin-3 UNC-104, only its weak and non-specific interaction via phosphatidylinositol 4,5-bisphosphates (forming the lipid bilayers of synaptic vesicles) has been characterized. Here, we present a novel, more specific way for UNC-104 to interact with synaptic vesicles - specifically with RAB-3 bound vesicles - via the dual linker complex UNC-10/SYD-2. Because many neurological diseases are linked to defects in axonal trafficking (often with protein accumulation phenotypes in neurons), understanding the molecular basis of motor/vesicle interaction might lead to the design of new drugs that may cure or prevent such diseases.

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On the driving forces in the type-II enzymes—Restriction molecular motors

Crystallography Reports ◽

10.1134/s1063774507060260 ◽

2007 ◽

Vol 52 (6) ◽

pp. 1094-1099 ◽

Cited By ~ 3

Author(s):

S. A. Pikin

Keyword(s):

Molecular Motors ◽

Driving Forces ◽

Type Ii

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Deposition of lipid bilayers on OH-density-controlled silicon dioxide surfaces

Journal of Vacuum Science & Technology A Vacuum Surfaces and Films ◽

10.1116/1.1943455 ◽

2005 ◽

Vol 23 (4) ◽

pp. 751-754 ◽

Cited By ~ 10

Author(s):

R. Tero ◽

T. Urisu ◽

H. Okawara ◽

K. Nagayama

Keyword(s):

Silicon Dioxide ◽

Lipid Bilayers

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Hydrodynamic collective effects of active protein machines in solution and lipid bilayers

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1506825112 ◽

2015 ◽

Vol 112 (28) ◽

pp. E3639-E3644 ◽

Cited By ~ 59

Author(s):

Alexander S. Mikhailov ◽

Raymond Kapral

Keyword(s):

Lipid Bilayers ◽

Conformational Changes ◽

Molecular Motors ◽

Molecular Machines ◽

Collective Effects ◽

Biological Cell ◽

Active Protein ◽

Diffusion Constants ◽

Large Numbers ◽

Diffusion Enhancement

The cytoplasm and biomembranes in biological cells contain large numbers of proteins that cyclically change their shapes. They are molecular machines that can function as molecular motors or carry out various other tasks in the cell. Many enzymes also undergo conformational changes within their turnover cycles. We analyze the advection effects that nonthermal fluctuating hydrodynamic flows induced by active proteins have on other passive molecules in solution or membranes. We show that the diffusion constants of passive particles are enhanced substantially. Furthermore, when gradients of active proteins are present, a chemotaxis-like drift of passive particles takes place. In lipid bilayers, the effects are strongly nonlocal, so that active inclusions in the entire membrane contribute to local diffusion enhancement and the drift. All active proteins in a biological cell or in a membrane contribute to such effects and all passive particles, and the proteins themselves, will be subject to them.

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Observation of Concanavalin-A receptors on hydrated planar erythrocyte membrane film by in situ electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100076640 ◽

1983 ◽

Vol 41 ◽

pp. 608-609

Author(s):

Neng-Bo He ◽

S.W. Hui

Keyword(s):

Lipid Bilayers ◽

Erythrocyte Membrane ◽

Lipid Membranes ◽

Surface Film ◽

Biological Membranes ◽

Electron Microscopic Observation ◽

Electron Microscopic ◽

Black Lipid Membranes ◽

Fine Mesh ◽

Planar Films

Monolayers and planar "black" lipid membranes have been widely used as models for studying the structure and properties of biological membranes. Because of the lack of a suitable method to prepare these membranes for electron microscopic observation, their ultrastructure is so far not well understood. A method of forming molecular bilayers over the holes of fine mesh grids was developed by Hui et al. to study hydrated and unsupported lipid bilayers by electron diffraction, and to image phase separated domains by diffraction contrast. We now adapted the method of Pattus et al. of spreading biological membranes vesicles on the air-water interfaces to reconstitute biological membranes into unsupported planar films for electron microscopic study. hemoglobin-free human erythrocyte membrane stroma was prepared by hemolysis. The membranes were spreaded at 20°C on balanced salt solution in a Langmuir trough until a surface pressure of 20 dyne/cm was reached. The surface film was repeatedly washed by passing to adjacent troughs over shallow partitions (fig. 1).

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Solute redistribution during in-situ irradiation of alloys in the high voltage electron microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100108994 ◽

1978 ◽

Vol 36 (1) ◽

pp. 370-371

Author(s):

P. R. Okamoto ◽

N.Q. Lam ◽

R. L. Lyles

Keyword(s):

Electron Microscope ◽

High Voltage ◽

Driving Forces ◽

Solute Diffusion ◽

Solute Redistribution ◽

Voltage Electron ◽

High Voltage Electron Microscope ◽

High Voltage Electron ◽

Thin Foils ◽

Solute Atoms

During irradiation of thin foils in a high voltage electron microscope (HVEM) defect gradients will be set up between the foil surfaces and interior. In alloys defect gradients provide additional driving forces for solute diffusion since any preferential binding and/or exchange between solute atoms and mobile defects will couple a net flux of solute atoms to the defect fluxes. Thus, during irradiation large nonequilibrium compositional gradients can be produced near the foil surfaces in initially homogeneous alloys. A system of coupled reaction-rate and diffusion equations describing the build up of mobile defects and solute redistribution in thin foils and in a semi-infinite medium under charged-particle irradiation has been formulated. Spatially uniform and nonuniform damage production rates have been used to model solute segregation under electron and ion irradiation conditions.An example calculation showing the time evolution of the solute concentration in a 2000 Å thick foil during electron irradiation is shown in Fig. 1.

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Video-microscopic measurement of cell-substratum traction forces generated by locomoting keratocytes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100146783 ◽

1993 ◽

Vol 51 ◽

pp. 188-189

Author(s):

Tim Oliver ◽

Michelle Leonard ◽

Juliet Lee ◽

Akira Ishihara ◽

Ken Jacobson

Keyword(s):

Silicone Rubber ◽

Molecular Motors ◽

Video Frame ◽

Traction Forces ◽

Cell Traction Forces ◽

Latex Beads ◽

Cell Traction ◽

Local Cell ◽

Microscopic Measurement ◽

Kinetics Of

We are using video-enhanced light microscopy to investigate the pattern and magnitude of forces that fish keratocytes exert on flexible silicone rubber substrata. Our goal is a clearer understanding of the way molecular motors acting through the cytoskeleton co-ordinate their efforts into locomotion at cell velocities up to 1 μm/sec. Cell traction forces were previously observed as wrinkles(Fig.l) in strong silicone rubber films by Harris.(l) These forces are now measureable by two independant means.In the first of these assays, weakly crosslinked films are made, into which latex beads have been embedded.(Fig.2) These films report local cell-mediated traction forces as bead displacements in the plane of the film(Fig.3), which recover when the applied force is released. Calibrated flexible glass microneedles are then used to reproduce the translation of individual beads. We estimate the force required to distort these films to be 0.5 mdyne/μm of bead movement. Video-frame analysis of bead trajectories is providing data on the relative localisation, dissipation and kinetics of traction forces.

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