scholarly journals Pattern formation and polarity sorting of driven actin filaments on lipid membranes

2021 ◽  
Vol 118 (6) ◽  
pp. e2017047118
Author(s):  
Alfredo Sciortino ◽  
Andreas R. Bausch
Keyword(s):  
Lipid Membranes ◽  
Collective Motion ◽  
Topological Defects ◽  
Binary Interaction ◽  
Complex Structures ◽  
Supported Lipid Bilayer ◽  
Binary Collisions ◽  
The Individual ◽  
Interaction Rule ◽  
Positive Half

Collective motion of active matter is ubiquitously observed, ranging from propelled colloids to flocks of bird, and often features the formation of complex structures composed of agents moving coherently. However, it remains extremely challenging to predict emergent patterns from the binary interaction between agents, especially as only a limited number of interaction regimes have been experimentally observed so far. Here, we introduce an actin gliding assay coupled to a supported lipid bilayer, whose fluidity forces the interaction between self-propelled filaments to be dominated by steric repulsion. This results in filaments stopping upon binary collisions and eventually aligning nematically. Such a binary interaction rule results at high densities in the emergence of dynamic collectively moving structures including clusters, vortices, and streams of filaments. Despite the microscopic interaction having a nematic symmetry, the emergent structures are found to be polar, with filaments collectively moving in the same direction. This is due to polar biases introduced by the stopping upon collision, both on the individual filaments scale as well as on the scale of collective structures. In this context, positive half-charged topological defects turn out to be a most efficient trapping and polarity sorting conformation.

scholarly journals Every Detail Matters. That Is, How the Interaction between Gα Proteins and Membrane Affects Their Function

Membranes ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 222
Author(s):  
Agnieszka Polit ◽  
Paweł Mystek ◽  
Ewa Błasiak
Keyword(s):  
Signal Transduction ◽  
G Protein ◽  
G Proteins ◽  
Lipid Membranes ◽  
Signaling Proteins ◽  
Heterotrimeric G Proteins ◽  
Membrane Attachment ◽  
The Individual ◽  
Multicellular Organisms ◽  
G Protein Coupled

In highly organized multicellular organisms such as humans, the functions of an individual cell are dependent on signal transduction through G protein-coupled receptors (GPCRs) and subsequently heterotrimeric G proteins. As most of the elements belonging to the signal transduction system are bound to lipid membranes, researchers are showing increasing interest in studying the accompanying protein–lipid interactions, which have been demonstrated to not only provide the environment but also regulate proper and efficient signal transduction. The mode of interaction between the cell membrane and G proteins is well known. Despite this, the recognition mechanisms at the molecular level and how the individual G protein-membrane attachment signals are interrelated in the process of the complex control of membrane targeting of G proteins remain unelucidated. This review focuses on the mechanisms by which mammalian Gα subunits of G proteins interact with lipids and the factors responsible for the specificity of membrane association. We summarize recent data on how these signaling proteins are precisely targeted to a specific site in the membrane region by introducing well-defined modifications as well as through the presence of polybasic regions within these proteins and interactions with other components of the heterocomplex.

An Approach for Structural-Acoustic Optimization of Ribbed Panels Using Component Mode Synthesis

2012 ◽  
Author(s):  
Micah R. Shepherd ◽  
Stephen A. Hambric
Keyword(s):  
Optimization Problem ◽  
Optimization Problems ◽  
Sound Radiation ◽  
Component Mode Synthesis ◽  
Complex Structures ◽  
Couple Dynamics ◽  
The Individual ◽  
Global Design Optimization ◽  
Control Designs ◽  
Speed And Accuracy

Component mode synthesis (CMS) is an approach used to couple dynamics of complex structures using modes of individual components. A CMS approach is developed to determine the response of a ribbed panel based on the individual rib and plate modes. The CMS method allows for rapid evaluation of noise-control designs as component modes need to be solved only once. Since efficient evaluation is required for global design optimization procedures, the CMS approach can be well suited in optimization problems. A simple structural-acoustic optimization problem was created to demonstrate the utility of the formulation by finding the optimal rib location and material to reduce sound radiation for a point-driven plate. Several parameters of the optimization algorithm are varied to test convergence speed and accuracy.

scholarly journals A first-principle mechanism for particulate aggregation and self-assembly in stratified fluids

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Roberto Camassa ◽  
Daniel M. Harris ◽  
Robert Hunt ◽  
Zeliha Kilic ◽  
Richard M. McLaughlin
Keyword(s):  
Self Assembly ◽  
Large Scale ◽  
Collective Motion ◽  
Solute Diffusion ◽  
Many Body ◽  
Complex Interplay ◽  
Fluid Systems ◽  
The Individual ◽  
Many Particles ◽  
Fundamental Mechanism

AbstractAn extremely broad and important class of phenomena in nature involves the settling and aggregation of matter under gravitation in fluid systems. Here, we observe and model mathematically an unexpected fundamental mechanism by which particles suspended within stratification may self-assemble and form large aggregates without adhesion. This phenomenon arises through a complex interplay involving solute diffusion, impermeable boundaries, and aggregate geometry, which produces toroidal flows. We show that these flows yield attractive horizontal forces between particles at the same heights. We observe that many particles demonstrate a collective motion revealing a system which appears to solve jigsaw-like puzzles on its way to organizing into a large-scale disc-like shape, with the effective force increasing as the collective disc radius grows. Control experiments isolate the individual dynamics, which are quantitatively predicted by simulations. Numerical force calculations with two spheres are used to build many-body simulations which capture observed features of self-assembly.

scholarly journals Conformity in the collective: differences in hunger affect individual and group behavior in a shoaling fish

2019 ◽  
Vol 30 (4) ◽  
pp. 968-974 ◽  
Author(s):  
Alexander D M Wilson ◽  
Alicia L J Burns ◽  
Emanuele Crosato ◽  
Joseph Lizier ◽  
Mikhail Prokopenko ◽  
...  
Keyword(s):  
Collective Behavior ◽  
Nearest Neighbor ◽  
Collective Motion ◽  
Internal State ◽  
Group Behavior ◽  
Fundamental Interest ◽  
Individual Level ◽  
Group Members ◽  
The Individual ◽  
Nearest Neighbor Distances

Abstract Animal groups are often composed of individuals that vary according to behavioral, morphological, and internal state parameters. Understanding the importance of such individual-level heterogeneity to the establishment and maintenance of coherent group responses is of fundamental interest in collective behavior. We examined the influence of hunger on the individual and collective behavior of groups of shoaling fish, x-ray tetras (Pristella maxillaris). Fish were assigned to one of two nutritional states, satiated or hungry, and then allocated to 5 treatments that represented different ratios of satiated to hungry individuals (8 hungry, 8 satiated, 4:4 hungry:satiated, 2:6 hungry:satiated, 6:2 hungry:satiated). Our data show that groups with a greater proportion of hungry fish swam faster and exhibited greater nearest neighbor distances. Within groups, however, there was no difference in the swimming speeds of hungry versus well-fed fish, suggesting that group members conform and adapt their swimming speed according to the overall composition of the group. We also found significant differences in mean group transfer entropy, suggesting stronger patterns of information flow in groups comprising all, or a majority of, hungry individuals. In contrast, we did not observe differences in polarization, a measure of group alignment, within groups across treatments. Taken together these results demonstrate that the nutritional state of animals within social groups impacts both individual and group behavior, and that members of heterogenous groups can adapt their behavior to facilitate coherent collective motion.

Fabrication of Metallic Nanocomponents by Forging of Ni3Al-Nanoparticles.

2012 ◽  
Vol 1412 ◽  
Author(s):  
Landefeld Andreas ◽  
Rösler Joachim
Keyword(s):  
High Performance ◽  
High Strength ◽  
Complex Structures ◽  
Free Standing ◽  
Large Numbers ◽  
Upset Forging ◽  
Nanoscale Fabrication ◽  
The Individual ◽  
Near Future ◽  
Very High

ABSTRACTThe trend to manufacture components reduced in size at the micro- and nano-scale is obvious and is becoming more and more the state of art in designing actuators, sensors and chips. In recent years, nanoscale fabrication has developed considerably, but the fabrication of freestanding nanosize components is still a great challenge. The fabrication of metallic nanocomponents utilizing three basic steps is demonstrated here. First, metallic alloys are used as factories to produce a metallic raw stock of nano-objects/nanoparticles in large numbers. These objects are then isolated from the powder containing thousands of such objects inside a scanning electron microscope using manipulators, and placed on a micro-anvil or a die. Finally, the shape of the individual nano-object is changed by nanoforging using a microhammer to get specific geometries such as discs and more complex components such as gears and wheels in the near future. The almost cubic particles are essentially defect-free, therefore, provide very high strength (σ>2500MPa) in combination with excellent formability (|ϕ|>1,6). There are two approaches for forming these small particles. Upset forging is used to forge small discs (height<100nm) and to shape the nanoparticle in specific areas. Press forging into nano-dies is used to forge more complex structures. In this way free-standing, high-strength, metallic nanoobjects may be shaped into components with dimensions in the 100 nm range. By assembling such nano-components, high-performance microsystems can be fabricated, which are truly in the micrometre scale (the size ratio of a system to its component is typically 10:1).

scholarly journals Introduction

2008 ◽  
Vol 366 (1873) ◽  
pp. 2095-2102 ◽  
Author(s):  
I Eames
Keyword(s):  
Gas Phase ◽  
Microelectromechanical Systems ◽  
Collective Motion ◽  
Daily Activities ◽  
Health Physics ◽  
Theme Issue ◽  
Technological Developments ◽  
The Common ◽  
The Individual ◽  
Solid Liquid

Dispersed multiphase flows—the study of the individual or collective motion of a discrete (solid/liquid/gas) phase in a continuous (liquid/gas) phase—has broad implications for health physics, processes in the natural environment, new technological developments (microelectromechanical systems) and many industrial problems. Many of these processes are important in our daily activities. In this paper, a general overview of the papers in this Theme Issue is described and some of the common issues are identified.

scholarly journals Site-Specific Tryptophan Labels Reveal Local Microsecond–Millisecond Motions of Dihydrofolate Reductase

Molecules ◽  
2020 ◽  
Vol 25 (17) ◽  
pp. 3819
Author(s):  
Morgan B. Vaughn ◽  
Chloe Biren ◽  
Qun Li ◽  
Ashwin Ragupathi ◽  
R. Brian Dyer
Keyword(s):  
Dihydrofolate Reductase ◽  
Conformational Changes ◽  
Collective Motion ◽  
Tryptophan Fluorescence ◽  
Slow Phase ◽  
Enzyme Dynamics ◽  
Wild Type ◽  
Two Phase ◽  
Protein Motions ◽  
The Individual

Many enzymes are known to change conformations during their catalytic cycle, but the role of these protein motions is not well understood. Escherichia coli dihydrofolate reductase (DHFR) is a small, flexible enzyme that is often used as a model system for understanding enzyme dynamics. Recently, native tryptophan fluorescence was used as a probe to study micro- to millisecond dynamics of DHFR. Yet, because DHFR has five native tryptophans, the origin of the observed conformational changes could not be assigned to a specific region within the enzyme. Here, we use DHFR mutants, each with a single tryptophan as a probe for temperature jump fluorescence spectroscopy, to further inform our understanding of DHFR dynamics. The equilibrium tryptophan fluorescence of the mutants shows that each tryptophan is in a different environment and that wild-type DHFR fluorescence is not a simple summation of all the individual tryptophan fluorescence signatures due to tryptophan–tryptophan interactions. Additionally, each mutant exhibits a two-phase relaxation profile corresponding to ligand association/dissociation convolved with associated conformational changes and a slow conformational change that is independent of ligand association and dissociation, similar to the wild-type enzyme. However, the relaxation rate of the slow phase depends on the location of the tryptophan within the enzyme, supporting the conclusion that the individual tryptophan fluorescence dynamics do not originate from a single collective motion, but instead report on local motions throughout the enzyme.

scholarly journals Order by disorder: saving collective motion from topological defects in a conservative model

2020 ◽  
Vol 2020 (1) ◽  
pp. 013209 ◽  
Author(s):  
Mathias Casiulis ◽  
Marco Tarzia ◽  
Leticia F Cugliandolo ◽  
Olivier Dauchot
Keyword(s):  
Collective Motion ◽  
Topological Defects

scholarly journals Cyclosporine CsA—The Physicochemical Characterization of Liposomal and Colloidal Systems

2020 ◽  
Vol 4 (4) ◽  
pp. 46
Author(s):  
Agnieszka Ewa Wiącek ◽  
Małgorzata Jurak ◽  
Agata Ładniak ◽  
Kacper Przykaza ◽  
Klaudia Szafran
Keyword(s):  
Particle Size ◽  
Lipid Membranes ◽  
Physicochemical Characterization ◽  
Colloidal Systems ◽  
Drug Bioavailability ◽  
Individual Variations ◽  
The Stability ◽  
The Individual ◽  
Formulation Stability

This paper presents an overview of the possibilities of testing various cyclosporine (CsA) formulations with an emphasis on parameters that may be key to improving the stability and biocompatibility. The feasibility of CsA colloidal systems for oral (injection) administration were investigated using different techniques and compared with similar investigations of other researchers. The chosen CsA systems were developed using dipalmitoylphosphocholine (DPPC) and/or cholesterol as a lipid matrix, stabilized with ethanol, with soybean oil or n-tetradecane as oil phase in emulsions, under natural pH, room and physiological temperature. Their integrity was found to be strictly dependent on the stabilizers. The highest CsA penetrability with the system containing phospholipid in the context of its interactions with lipid membranes was shown. Also, the bioavailability of CsA can be enhanced with the biopolymer antibacterial chitosan. This mini-review suggests the suitability of liposome/microemulsion as promising vehicles for CsA delivery. The most hopeful proved to be formulation with the smaller particle size facilitating absorption, but when safety is assessed, relying on just the particle size cannot be the only criteria. Reassumed, the CsA formulation stability known on the basis of the size and zeta potential measurements guarantees a decrease of the individual variations in the drug bioavailability, toxicity and minimizes rejection.

Sign in / Sign up

Export Citation Format

Share Document