This paper proposes a 3-dimensional coarse grain model of microtubules and treats the tubulin monomer as a sphere of multiple patches, with parameters chosen to yield experimental values of bending and stretching stif...This paper proposes a 3-dimensional coarse grain model of microtubules and treats the tubulin monomer as a sphere of multiple patches, with parameters chosen to yield experimental values of bending and stretching stiffness. The model has demonstrated the ability to produce the bistability of tubulin sheets, elastic deformation near the tip, and cracking and peeling of protofilaments. This model is expected to take into account the structural and mechanical aspects underlying the physical mechanism of polymerization/depolymerization and dynamic instability of microtubules.展开更多
N-budding lipid vesicles with single holes were analyzed theoretically by taking into account the line tension of membrane with a hole and the bending energy of membranes based on the Spontaneous-Curvature (SC) model....N-budding lipid vesicles with single holes were analyzed theoretically by taking into account the line tension of membrane with a hole and the bending energy of membranes based on the Spontaneous-Curvature (SC) model. We solved numerically the Euler-Lagrange equation and the boundary conditions holding on the membrane edge to obtain axisymmetric vesicle shapes, which minimize the total energy. The numerical results show that the size of the opening-up vesicle is larger when the line tension is lower. In other words, additive protein molecules reduce the line tension of lipid membranes, such as talin dose.展开更多
The interaction between C60 nanoparticles and biomembranes has been of great interest in researches over the past decades due to their novel applications as well as potential cytotoxicity.In this work,we study the def...The interaction between C60 nanoparticles and biomembranes has been of great interest in researches over the past decades due to their novel applications as well as potential cytotoxicity.In this work,we study the deformation of the small unilamellar vesicles composed of dipalmitoylphosphatidylcholine(DPPC)lipid bilayers infiltrated with C60 nanoparticles of different molecular concentrations through coarse-grained molecular dynamics simulations.By employing the Helfrich spontaneous curvature model,the bending modulus and the spontaneous curvature of the vesicles with C60 nanoparticles of different concentrations are obtained according to the simulation data.The results show that the bending modulus and the spontaneous curvature of pure DPPC vesicle membranes are approximately 1.6×10^-19J and 1.4 nm^-1,respectively.Both of them increase linearly approximately as the C60 concentration increases from 0 to 16.3%.The density profiles of vesicles,the order of lipid packing and the diffusion characteristics of DPPC and C60 are also investigated.展开更多
The membrane’s dynamics is very important for cells.A membrane in 2-dimensional space can be seen as an incompressible closed curve in a plane or a cylindrical surface in 3-dimensional space.In this paper,we design a...The membrane’s dynamics is very important for cells.A membrane in 2-dimensional space can be seen as an incompressible closed curve in a plane or a cylindrical surface in 3-dimensional space.In this paper,we design a second-order accurate numerical algorithm to simulate the shape transformation of the membrane.In the algorithm,we use the tangent angles to present the curve and avoid the difficulties from the constraint of curve’s incompressible condition.A lot of interesting phenomena are obtained.Some of them are very like the life processes of cells,such as exocytosis and endocytosis.Furthermore,we can see the relation between two dynamic models clearly.At last,considering the influence of the inner incompressible fluids partially,we add a constraint:the area circled by the membrane maintain invariable.The numerical results show the dynamic motions of a curve remaining its local arc length and inner area constant.展开更多
We propose a mathematically rigorous method to measure the spontaneous curvature of a bilayer membrane by molecular dynamics(MD)simulation,which provides description of the molecular mechanisms that cause the spontane...We propose a mathematically rigorous method to measure the spontaneous curvature of a bilayer membrane by molecular dynamics(MD)simulation,which provides description of the molecular mechanisms that cause the spontaneous curvature.As a main result,for the membrane setup investigated,the spontaneous curvature is proved to be a constant plus twice the mean curvature of the membrane in its tensionless ground state.The spontaneous curvature due to the built-in transbilayer asymmetry of the membrane in terms of lipid shape is studied by the proposed method.A linear dependence of the spontaneous curvature with respect to the head-bead diameter difference and the lipid mixing ratio is discovered.The consistency with the theoretical results provides evidence supporting the validity of our method.展开更多
We consider that the observable cosmological constant is the sum of the vacuum （Avac） and the induced term （Aind - 3m^2/4） with m being the ultra-llght masses （≈ Hubble parameter） implemented in the theory from...We consider that the observable cosmological constant is the sum of the vacuum （Avac） and the induced term （Aind - 3m^2/4） with m being the ultra-llght masses （≈ Hubble parameter） implemented in the theory from supergravities arguments and non-minimal coupling. In the absence of a scalar buildup of matter fields, we study its effects on spontaneous symmetry breaking with a Higgs potential and show how the presence of the ultra-light masses yields some important consequences for the early universe and new constraints on the Higgs and electroweak gauge bosons masses.展开更多
基金supported by the National Natural Science Foundation of China(11072230 and 11132009)Hundred Talents Project of Chinese Academy of Sciences
文摘This paper proposes a 3-dimensional coarse grain model of microtubules and treats the tubulin monomer as a sphere of multiple patches, with parameters chosen to yield experimental values of bending and stretching stiffness. The model has demonstrated the ability to produce the bistability of tubulin sheets, elastic deformation near the tip, and cracking and peeling of protofilaments. This model is expected to take into account the structural and mechanical aspects underlying the physical mechanism of polymerization/depolymerization and dynamic instability of microtubules.
基金supported by the National Natural Science Foundation of China (Grant no.10374063)
文摘N-budding lipid vesicles with single holes were analyzed theoretically by taking into account the line tension of membrane with a hole and the bending energy of membranes based on the Spontaneous-Curvature (SC) model. We solved numerically the Euler-Lagrange equation and the boundary conditions holding on the membrane edge to obtain axisymmetric vesicle shapes, which minimize the total energy. The numerical results show that the size of the opening-up vesicle is larger when the line tension is lower. In other words, additive protein molecules reduce the line tension of lipid membranes, such as talin dose.
基金Project supported by the National Natural Science Foundation of China(Grant No.61475196)。
文摘The interaction between C60 nanoparticles and biomembranes has been of great interest in researches over the past decades due to their novel applications as well as potential cytotoxicity.In this work,we study the deformation of the small unilamellar vesicles composed of dipalmitoylphosphatidylcholine(DPPC)lipid bilayers infiltrated with C60 nanoparticles of different molecular concentrations through coarse-grained molecular dynamics simulations.By employing the Helfrich spontaneous curvature model,the bending modulus and the spontaneous curvature of the vesicles with C60 nanoparticles of different concentrations are obtained according to the simulation data.The results show that the bending modulus and the spontaneous curvature of pure DPPC vesicle membranes are approximately 1.6×10^-19J and 1.4 nm^-1,respectively.Both of them increase linearly approximately as the C60 concentration increases from 0 to 16.3%.The density profiles of vesicles,the order of lipid packing and the diffusion characteristics of DPPC and C60 are also investigated.
基金the special funds for Major State Research Projects 2005CB321704National Science Foundation of China for Distinguished Young Scholars 10225103 and 20490222.
文摘The membrane’s dynamics is very important for cells.A membrane in 2-dimensional space can be seen as an incompressible closed curve in a plane or a cylindrical surface in 3-dimensional space.In this paper,we design a second-order accurate numerical algorithm to simulate the shape transformation of the membrane.In the algorithm,we use the tangent angles to present the curve and avoid the difficulties from the constraint of curve’s incompressible condition.A lot of interesting phenomena are obtained.Some of them are very like the life processes of cells,such as exocytosis and endocytosis.Furthermore,we can see the relation between two dynamic models clearly.At last,considering the influence of the inner incompressible fluids partially,we add a constraint:the area circled by the membrane maintain invariable.The numerical results show the dynamic motions of a curve remaining its local arc length and inner area constant.
基金the financial support through the Natural Science Foundation of China No.11004131the financial support by the Natural Science Foundation of China No.50930003.
文摘We propose a mathematically rigorous method to measure the spontaneous curvature of a bilayer membrane by molecular dynamics(MD)simulation,which provides description of the molecular mechanisms that cause the spontaneous curvature.As a main result,for the membrane setup investigated,the spontaneous curvature is proved to be a constant plus twice the mean curvature of the membrane in its tensionless ground state.The spontaneous curvature due to the built-in transbilayer asymmetry of the membrane in terms of lipid shape is studied by the proposed method.A linear dependence of the spontaneous curvature with respect to the head-bead diameter difference and the lipid mixing ratio is discovered.The consistency with the theoretical results provides evidence supporting the validity of our method.
文摘We consider that the observable cosmological constant is the sum of the vacuum （Avac） and the induced term （Aind - 3m^2/4） with m being the ultra-llght masses （≈ Hubble parameter） implemented in the theory from supergravities arguments and non-minimal coupling. In the absence of a scalar buildup of matter fields, we study its effects on spontaneous symmetry breaking with a Higgs potential and show how the presence of the ultra-light masses yields some important consequences for the early universe and new constraints on the Higgs and electroweak gauge bosons masses.
