Role of combined cell membrane and wall mechanical properties regulated by polarity signals in cell budding

AbstractThe budding yeast, Saccharomyces cerevisiae, is a prime biological model to study mechanisms underlying asymmetric growth. Previous studies have shown that, prior to yeast bud emergence, polarization of a conserved small GTPase, Cdc42, must be established. Additionally, hydrolase changes the mechanical properties of the cell wall and plasma membrane with the periplasm between them (cell surface). However, how the surface mechanical properties in the emerging bud are different from the properties of the mother cell and their role in bud formation are not well understood. We hypothesize that the polarized chemical signal alters the local dimensionless ratio of stretching to bending stiffness of the cell surface of the emerging yeast bud. To test this hypothesis, a novel three-dimensional coarse-grained particle-based model has been developed which describes inhomogeneous mechanical properties of the cell surface. Model simulations suggest that regulation of the dimensionless ratio of stretching to bending stiffness of the cell surface is necessary to initiate bud formation. Furthermore, model simulations predict that bud shape depends strongly on the experimentally observed molecular distribution of the polarized signaling molecule Cdc42, while the neck shape of the emerging bud is strongly impacted by the properties of the chitin and septin ring. This 3D model of asymmetric cell growth can also be used for studying viral budding and other vegetative reproduction processes performed via budding.

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Beam Theory of Thermal–Electro-Mechanical Coupling for Single-Wall Carbon Nanotubes

Nanomaterials ◽

10.3390/nano11040923 ◽

2021 ◽

Vol 11 (4) ◽

pp. 923

Author(s):

Kun Huang ◽

Ji Yao

Keyword(s):

Mechanical Properties ◽

Carbon Nanotubes ◽

Beam Theory ◽

Bending Stiffness ◽

Single Wall Carbon Nanotubes ◽

Beam Model ◽

Euler Beam ◽

New Model ◽

Mechanical Coupling ◽

Electrostatic Fields

The potential application field of single-walled carbon nanotubes (SWCNTs) is immense, due to their remarkable mechanical and electrical properties. However, their mechanical properties under combined physical fields have not attracted researchers’ attention. For the first time, the present paper proposes beam theory to model SWCNTs’ mechanical properties under combined temperature and electrostatic fields. Unlike the classical Bernoulli–Euler beam model, this new model has independent extensional stiffness and bending stiffness. Static bending, buckling, and nonlinear vibrations are investigated through the classical beam model and the new model. The results show that the classical beam model significantly underestimates the influence of temperature and electrostatic fields on the mechanical properties of SWCNTs because the model overestimates the bending stiffness. The results also suggest that it may be necessary to re-examine the accuracy of the classical beam model of SWCNTs.

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Unveiling the Dynamics of KRAS4b on Lipid Model Membranes

The Journal of Membrane Biology ◽

10.1007/s00232-021-00176-z ◽

2021 ◽

Author(s):

Cesar A. López ◽

Animesh Agarwal ◽

Que N. Van ◽

Andrew G. Stephen ◽

S. Gnanakaran

Keyword(s):

Molecular Mechanisms ◽

Hypervariable Region ◽

Small Gtpase ◽

Model Systems ◽

Coarse Grained ◽

Regulatory Function ◽

Limited Information ◽

Long Time ◽

Cell Growth And Differentiation ◽

State Models

AbstractSmall GTPase proteins are ubiquitous and responsible for regulating several processes related to cell growth and differentiation. Mutations that stabilize their active state can lead to uncontrolled cell proliferation and cancer. Although these proteins are well characterized at the cellular scale, the molecular mechanisms governing their functions are still poorly understood. In addition, there is limited information about the regulatory function of the cell membrane which supports their activity. Thus, we have studied the dynamics and conformations of the farnesylated KRAS4b in various membrane model systems, ranging from binary fluid mixtures to heterogeneous raft mimics. Our approach combines long time-scale coarse-grained (CG) simulations and Markov state models to dissect the membrane-supported dynamics of KRAS4b. Our simulations reveal that protein dynamics is mainly modulated by the presence of anionic lipids and to some extent by the nucleotide state (activation) of the protein. In addition, our results suggest that both the farnesyl and the polybasic hypervariable region (HVR) are responsible for its preferential partitioning within the liquid-disordered (Ld) domains in membranes, potentially enhancing the formation of membrane-driven signaling platforms. Graphic Abstract

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Grain growth behaviour and mechanical properties of coarse-grained cemented carbides with bimodal grain size distributions

Materials Science and Engineering A ◽

10.1016/j.msea.2020.140586 ◽

2020 ◽

pp. 140586

Author(s):

Rengui He ◽

Qiumin Yang ◽

Bin Li ◽

Jia Lou ◽

Hailin Yang ◽

...

Keyword(s):

Mechanical Properties ◽

Grain Size ◽

Grain Growth ◽

Coarse Grained ◽

Cemented Carbides ◽

Size Distributions ◽

Growth Behaviour ◽

Grain Size Distributions ◽

Bimodal Grain Size

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Rheology of hydrocarbon gels

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1950.0008 ◽

1950 ◽

Vol 200 (1061) ◽

pp. 183-188 ◽

Cited By ~ 21

Keyword(s):

Mechanical Properties ◽

Experimental Measurement ◽

Theoretical Basis ◽

Continuous Media ◽

Point Of View ◽

Coarse Grained ◽

Testing Instrument ◽

Fine Grained ◽

Mineral Oils ◽

Space And Time

Hydrocarbon gels contain a number of materials, such as rubber, greases, saponified mineral oils, etc., of great interest for various engineering purposes. Specific requirements in mechanical properties have been met by producing gels in appropriately chosen patterns of constituent components of visible, colloidal, molecular and atomic sizes, ranging from coarse-grained aggregates, represented by sponges, foams, emulsions, etc.; to fine-grained and apparently homogeneous ones, represented by optically clear compounds. The engineer who has to deal with the whole range of such materials will adopt a macroscopic point of view, based on an apparent continuity of all the material structures and of the distributions in space and time of the displacements and forces occurring under mechanical actions. It has been possible to determine these distributions in the framework of a comprehensive scheme in which the fundamental principles of the mechanics of continuous media provide the theoretical basis, and a testing instrument of new design, termed Rheogoniometer, the means of experimental measurement (Weissenberg 1931, 1934, 1946, 1947, 1948).

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New Approach In The Properties Evaluation Of Ultrafine-Grained OFHC Copper

Archives of Metallurgy and Materials ◽

10.1515/amm-2015-0180 ◽

2015 ◽

Vol 60 (2) ◽

pp. 605-614 ◽

Cited By ~ 2

Author(s):

T. Kvačkaj ◽

A. Kováčová ◽

J. Bidulská ◽

R. Bidulský ◽

R. Kočičko

Keyword(s):

Mechanical Properties ◽

Strain Rate ◽

Tensile Tests ◽

Coarse Grained ◽

Wear Behaviour ◽

Ofhc Copper ◽

Strain Rates ◽

Ultrafine Grained ◽

Reduction Of Area ◽

Pin On Disk

AbstractIn this study, static, dynamic and tribological properties of ultrafine-grained (UFG) oxygen-free high thermal conductivity (OFHC) copper were investigated in detail. In order to evaluate the mechanical behaviour at different strain rates, OFHC copper was tested using two devices resulting in static and dynamic regimes. Moreover, the copper was subjected to two different processing methods, which made possible to study the influence of structure. The study of strain rate and microstructure was focused on progress in the mechanical properties after tensile tests. It was found that the strain rate is an important parameter affecting mechanical properties of copper. The ultimate tensile strength increased with the strain rate increasing and this effect was more visible at high strain rates$({\dot \varepsilon} \sim 10^2 \;{\rm{s}}^{ - 1} )$. However, the reduction of area had a different progress depending on microstructural features of materials (coarse-grained vs. ultrafine-grained structure) and introduced strain rate conditions during plastic deformation (static vs. dynamic regime). The wear behaviour of copper was investigated through pin-on-disk tests. The wear tracks examination showed that the delamination and the mild oxidational wears are the main wear mechanisms.

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Evaluation of coarse-grained mechanical properties using small direct shear test

International Journal of Geotechnical Engineering ◽

10.1080/19386362.2018.1505310 ◽

2018 ◽

pp. 1-13 ◽

Cited By ~ 1

Author(s):

SeyedArmin MotahariTabari ◽

Issa Shooshpasha

Keyword(s):

Mechanical Properties ◽

Direct Shear Test ◽

Shear Test ◽

Coarse Grained ◽

Direct Shear

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Impacts of a Parameterization Deficiency on Offline and Coupled Land Surface Model Simulations

Journal of Hydrometeorology ◽

10.1175/1525-7541(2003)004<0901:ioapdo>2.0.co;2 ◽

2003 ◽

Vol 4 (5) ◽

pp. 901-914 ◽

Cited By ~ 14

Author(s):

Yuqiong Liu ◽

Luis A. Bastidas ◽

Hoshin V. Gupta ◽

Soroosh Sorooshian

Keyword(s):

Land Surface ◽

Land Surface Model ◽

Surface Model ◽

Model Simulations

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Effects of graphene thickness and length distribution on the mechanical properties of graphene networks: A coarse-grained molecular dynamics simulation

Applied Surface Science ◽

10.1016/j.apsusc.2021.151023 ◽

2021 ◽

pp. 151023

Author(s):

Qiang Bao ◽

Zhenyu Yang ◽

Zixing Lu ◽

Xiaofan He

Keyword(s):

Mechanical Properties ◽

Molecular Dynamics ◽

Molecular Dynamics Simulation ◽

Length Distribution ◽

Dynamics Simulation ◽

Coarse Grained ◽

Coarse Grained Molecular Dynamics

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Grain Refinement and Deformation Behavior of Ultrafine Grained Pd and Pd-Ag Alloys Produced by HPT

Materials Science Forum ◽

10.4028/www.scientific.net/msf.584-586.182 ◽

2008 ◽

Vol 584-586 ◽

pp. 182-187

Author(s):

Lilia Kurmanaeva ◽

Yulia Ivanisenko ◽

J. Markmann ◽

Ruslan Valiev ◽

Hans Jorg Fecht

Keyword(s):

Mechanical Properties ◽

Deformation Behavior ◽

Materials Science ◽

High Pressure Torsion ◽

Uniform Elongation ◽

Grain Structure ◽

Coarse Grained ◽

Ultrafine Grain ◽

Ultrafine Grained ◽

Ultrafine Grain Structure

Investigations of mechanical properties of nanocrystalline (nc) materials are still in interest of materials science, because they offer wide application as structural materials thanks to their outstanding mechanical properties. NC materials demonstrate superior hardness and strength as compared with their coarse grained counterparts, but very often they possess a limited ductility or show low uniform elongation due to poor strain hardening ability. Here, we present the results of investigation of the microstructure and mechanical properties of nc Pd and Pd-x%Ag (x=20, 60) alloys. The initially coarse grained Pd-x% Ag samples were processed by high pressure torsion, which resulted in formation of homogenous ultrafine grain structure. The increase of Ag contents led to the decrease of the resulted grain size and change in deformation behavior, because of decreasing of stacking fault energy (SFE). The samples with larger Ag contents demonstrated the higher values of hardness, yield stress and ultimate stress. Remarkably the uniform elongation had also increased with increase of strength.

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