Gramicidin A(gA)is a kind of antibiotic peptide produced by bacillus brevis and it can dimerize across lipid bilayers to form a monovalent cation channel.In this work,we investigate the impact of cholesterol in the li...Gramicidin A(gA)is a kind of antibiotic peptide produced by bacillus brevis and it can dimerize across lipid bilayers to form a monovalent cation channel.In this work,we investigate the impact of cholesterol in the lipid bilayer on the binding of potassium ions with the gA channel and the transport of the ions across the channel.The results indicate that cholesterol can significantly influence the conformational stability of the gA channel and cause the channel deformation which inhibits the potassium ion binding with the channel and transport across the channel.The work provides some molecular insights into understanding of influence of lipids on the activity of gA channel in both model membranes and plasma membranes of intact cells.展开更多
Lateral organization and dynamics of lipids in plasma membranes are crucial for several cellular processes such as signal transduction across the membrane and still remain elusive.In this paper,using coarse-grained mo...Lateral organization and dynamics of lipids in plasma membranes are crucial for several cellular processes such as signal transduction across the membrane and still remain elusive.In this paper,using coarse-grained molecular dynamics simulation,we theoretically study the combined effects of headgroup charge and tail unsaturation of lipids on the lateral organization and diffusion of lipids in ternary lipid bilayers.In neutral ternary lipid bilayers composed of saturated lipids,unsaturated lipids,and cholesterols,under the conditions of given temperature and components,the main factor for the phase separation is the unsaturation of unsaturated lipids and the bilayers can be separated into liquid-ordered domains enriched in saturated lipids and cholesterols and liquid-disordered domains enriched in unsaturated lipids.Once the headgroup charge is introduced,the electrostatic repulsion between the negatively charged lipid headgroups will increase the distance between the charged lipids.We find that the lateral organization and diffusion of the lipids in the（partially） charged ternary lipid bilayers are determined by the competition between the headgroup charge and the unsaturation of the unsaturated lipids.In the bilayers containing unsaturated lipids with lower unsaturation,the headgroup charge plays a crucial role in the lateral organization and diffusion of lipids.The headgroup charge may make the lipid domains unstable and even can suppress phase separation of the lipids in some systems.However,in the bilayers containing highly unsaturated lipids,the lateral organization and diffusion of lipids are mainly dominated by the unsaturation of the unsaturated lipids.This work may provide some theoretical insights into understanding the formation of nanosized domains and lateral diffusion of lipids in plasma membranes.展开更多
Spectrin, the principal protein of the cytoskeleton of erythrocyte, plays a crucial role in the stability and flexibility of the plasma membrane of erythrocyte. In this work, we investigate the interactions between sp...Spectrin, the principal protein of the cytoskeleton of erythrocyte, plays a crucial role in the stability and flexibility of the plasma membrane of erythrocyte. In this work, we investigate the interactions between spectrins and phase-separated lipid bilayers using coarse-grained molecular dynamics simulation. We focus on the preference of spectrins with different lipids, the effects of the anionic lipids and the residue mutation on the interactions between spectrins and the lipid bilayers. The results indicate that spectrins prefer to contact with phosphatidylethanolamine(PE) lipids rather than with phosphatidylcholine(PC) lipids, and tend to contact with the liquid-disordered(Ld) domains enriched in unsaturated PE.Additionally, the anionic lipids, which show specific interaction with the positively charged or polar amino acids on the surface of the spectrins, can enhance the attraction between the spectrins and lipid domains. The mutation leads to the decrease of the structural stability of spectrins and increases the curvature of the lipid bilayer. This work provides some theoretical insights into understanding the erythrocyte structure and the mechanism of some blood diseases.展开更多
Generally speaking, the quark propagator is dependent on the quark chemical potential in the dense quantum chromodynamics （QCD）. By means of the generating functional method, we prove that the quark propagator actua...Generally speaking, the quark propagator is dependent on the quark chemical potential in the dense quantum chromodynamics （QCD）. By means of the generating functional method, we prove that the quark propagator actually depends on p4 ＋ iμ from the first principle of QCD. The relation between quark number density and quark condensate is discussed by analyzing their singularities. It is concluded that the quark number density has some singularities at certain # when T = 0, and the variations of the quark number density as well as the quark condensate are located at the same point. In other words, at a certain # the quark number density turns to nonzero, while the quark condensate begins to decrease from its vacuum value.展开更多
The dynamics of quantum discord for two identical qubits in two independent single-mode cavities and a common single-mode cavity are discussed. For the initial Bell state with correlated spins, while the entanglement ...The dynamics of quantum discord for two identical qubits in two independent single-mode cavities and a common single-mode cavity are discussed. For the initial Bell state with correlated spins, while the entanglement sudden death can occur, the quantum discord vanishes only at discrete moments in the independent cavities and never vanishes in the common cavity. Interestingly, quantum discord and entanglement show opposite behavior in the common cavity, unlike in the independent cavities. For the initial Bell state with anti-correlated spins, quantum discord and entanglement behave in the same way for both independent cavities and a common cavity. It is found that the detunings always stabilize the quantum discord.展开更多
Using cluster Monte Carlo method, we numerically investigate the coupling on the simple cubic lattice. We determine critical lines belong to the criticality in the XY model with nematic three-dimensional XY universali...Using cluster Monte Carlo method, we numerically investigate the coupling on the simple cubic lattice. We determine critical lines belong to the criticality in the XY model with nematic three-dimensional XY universality class in variable of θ （2θ） between the XY-ferromagnetic （nematic） and disordered states. Fhrthermore, the phase transition between the XY-ferromagnetic and the nematie states is found to be in the three-dimensional Ising universality class. The critical points are determined from the intersections of Binder ratios for various system sizes. With two sets of critical points obtained, we finally construct the phase diagram on the A-J plane.展开更多
The Janus monolayer transition metal dichalcogenides(TMDs)MXY(M=Mo,W,etc.and X,Y=S,Se,etc.)have been successfully synthesized in recent years.The Rashba spin splitting in these compounds arises due to the breaking of ...The Janus monolayer transition metal dichalcogenides(TMDs)MXY(M=Mo,W,etc.and X,Y=S,Se,etc.)have been successfully synthesized in recent years.The Rashba spin splitting in these compounds arises due to the breaking of out-of-plane mirror symmetry.Here we study the pairing symmetry of superconducting Janus monolayer TMDs within the weak-coupling framework near critical temperature Tc,of which the Fermi surface(FS)sheets centered around bothΓand K(K′)points.We find that the strong Rashba splitting produces two kinds of topological superconducting states which differ from that in its parent compounds.More specifically,at relatively high chemical potentials,we obtain a timereversal invariant s+f+p-wave mixed superconducting state,which is fully gapped and topologically nontrivial,i.e.,a Z_(2) topological state.On the other hand,a time-reversal symmetry breaking d+p+f-wave superconducting state appears at lower chemical potentials.This state possess a large Chern number|C|=6 at appropriate pairing strength,demonstrating its nontrivial band topology.Our results suggest the Janus monolayer TMDs to be a promising candidate for the intrinsic helical and chiral topological superconductors.展开更多
We calculate the quark number susceptibility （QNS） around the chiral critical end point （CEP）. The CEP is found to be located at （μc,Tc）= （80 MeV, 148 MeV） where μc and Tc are the critical chemical potential...We calculate the quark number susceptibility （QNS） around the chiral critical end point （CEP）. The CEP is found to be located at （μc,Tc）= （80 MeV, 148 MeV） where μc and Tc are the critical chemical potential and temperature, respectively. The QNS is found to have the highest and sharpest peak at the CEP. It is also found that, when the chemical potential μ is in the range of 60MeV≤ μ ≤ 110MeV, the QNS near the transition temperature is larger than the free field result, which indicates that the space-like damping mode dominates the degree of freedom of motion near the CEP.展开更多
An effective scheme within two displaced bosonic operators with equal positive and negative displacements is extended to study qubit-oscillator systems analytically in a unified way. Many previous analytical treatment...An effective scheme within two displaced bosonic operators with equal positive and negative displacements is extended to study qubit-oscillator systems analytically in a unified way. Many previous analytical treatments, such as generalized rotating-wave approximation （GRWA） [Phys. Rev. Lett. 99, 173601 （2007）] and an expansion in the qubit tunneling matrix element in the deep strong coupling regime [Phys. Rev. Lett. 105, 263603 （2010）] can be recovered straightforwardly within the present scheme. Moreover, further improving GRWA and the extension to the finite-bias case are implemented easily. The algebraic formulae for the eigensolutions are then derived explicitly and uniquely, which work well in a wide range of the coupling strengths, detunings, and static bias including the recent experimentally accessible parameters. The dynamics of the qubit for an oscillator in the ground state is also studied. At the experimentally accessible coupling regime, GRWA can always work well. When the coupling is enhanced to the intermediate regime, only the improving GRWA can give the correct description, while the result of GRWA shows strong deviations. The previous Van Vleck perturbation theory is not valid to describe the dynamics in the present-day experimentally accessible regime, except for the strongly biased cases.展开更多
From the graphical representation of the Dyson-Schwinger equation for the dressed gluon propagator it is shown that the gluon propagator in the Wigner phase should be different from that in the Nambu phase.Based on th...From the graphical representation of the Dyson-Schwinger equation for the dressed gluon propagator it is shown that the gluon propagator in the Wigner phase should be different from that in the Nambu phase.Based on this analysis,we propose a modified gluon propagator to reflect this fact.With such a modified gluon propagator,in the framework of the Nambu Jona Lasinio (NJL) model,we obtain the Wigner solution to the quark gap equation at finite current quark mass,which has not been found in literature.This provides a new point of view to study partial restoration of chiral symmetry at finite temperature and chemical potential.展开更多
Recent measurement on an LC resonator magnetically coupled to a superconducting qubit [Phys.Rev.Lett.105 (2010)237001] shows that the system operates in the ultra-strong coupling regime and crosses the limit of validi...Recent measurement on an LC resonator magnetically coupled to a superconducting qubit [Phys.Rev.Lett.105 (2010)237001] shows that the system operates in the ultra-strong coupling regime and crosses the limit of validity for the rotating-wave approximation of the Jaynes-Cummings model By using extended bosonic coherent states,we solve the Jaynes-Cummings model exactly without using the rotating-wave approximation.Our numerically exact results for the spectrum of the flux qubit coupled to the LC resonator are fully consistent with the experimental observations.The smallest Bloch-Siegert shift obtained is consistent with that observed in this experiment.In addition,the Bloch-Siegert shifts in arbitrary level transitions and for arbitrary coupling constants are predicted.展开更多
Taking into account the effect of the generalized Gor'kov and Melik-Barkhudarov(GMB)approximation,we calculate the radio-frequency spectra of balanced and homogeneous ultracold Fermi gases within the framework of ...Taking into account the effect of the generalized Gor'kov and Melik-Barkhudarov(GMB)approximation,we calculate the radio-frequency spectra of balanced and homogeneous ultracold Fermi gases within the framework of the non-self-consistent T-matrix approximation at unitarity in the normal phase.The corresponding equations are numerically calculated on the real frequency axis directly.It is found that our results agree well with the experimental result of the radio-frequency spectroscopy[Phys.Rev.Lett.101(2008)140403].展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11674287)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LY19A040009)。
文摘Gramicidin A(gA)is a kind of antibiotic peptide produced by bacillus brevis and it can dimerize across lipid bilayers to form a monovalent cation channel.In this work,we investigate the impact of cholesterol in the lipid bilayer on the binding of potassium ions with the gA channel and the transport of the ions across the channel.The results indicate that cholesterol can significantly influence the conformational stability of the gA channel and cause the channel deformation which inhibits the potassium ion binding with the channel and transport across the channel.The work provides some molecular insights into understanding of influence of lipids on the activity of gA channel in both model membranes and plasma membranes of intact cells.
基金Project supported by the National Natural Science Foundation of China(Grant No.11674287)China Scholarship Council
文摘Lateral organization and dynamics of lipids in plasma membranes are crucial for several cellular processes such as signal transduction across the membrane and still remain elusive.In this paper,using coarse-grained molecular dynamics simulation,we theoretically study the combined effects of headgroup charge and tail unsaturation of lipids on the lateral organization and diffusion of lipids in ternary lipid bilayers.In neutral ternary lipid bilayers composed of saturated lipids,unsaturated lipids,and cholesterols,under the conditions of given temperature and components,the main factor for the phase separation is the unsaturation of unsaturated lipids and the bilayers can be separated into liquid-ordered domains enriched in saturated lipids and cholesterols and liquid-disordered domains enriched in unsaturated lipids.Once the headgroup charge is introduced,the electrostatic repulsion between the negatively charged lipid headgroups will increase the distance between the charged lipids.We find that the lateral organization and diffusion of the lipids in the（partially） charged ternary lipid bilayers are determined by the competition between the headgroup charge and the unsaturation of the unsaturated lipids.In the bilayers containing unsaturated lipids with lower unsaturation,the headgroup charge plays a crucial role in the lateral organization and diffusion of lipids.The headgroup charge may make the lipid domains unstable and even can suppress phase separation of the lipids in some systems.However,in the bilayers containing highly unsaturated lipids,the lateral organization and diffusion of lipids are mainly dominated by the unsaturation of the unsaturated lipids.This work may provide some theoretical insights into understanding the formation of nanosized domains and lateral diffusion of lipids in plasma membranes.
基金supported by the National Natural Science Foundation of China (Grant No. 11674287)Zhejiang Provincial Natural Science Foundation of China(Grant No. LY19A040009)。
文摘Spectrin, the principal protein of the cytoskeleton of erythrocyte, plays a crucial role in the stability and flexibility of the plasma membrane of erythrocyte. In this work, we investigate the interactions between spectrins and phase-separated lipid bilayers using coarse-grained molecular dynamics simulation. We focus on the preference of spectrins with different lipids, the effects of the anionic lipids and the residue mutation on the interactions between spectrins and the lipid bilayers. The results indicate that spectrins prefer to contact with phosphatidylethanolamine(PE) lipids rather than with phosphatidylcholine(PC) lipids, and tend to contact with the liquid-disordered(Ld) domains enriched in unsaturated PE.Additionally, the anionic lipids, which show specific interaction with the positively charged or polar amino acids on the surface of the spectrins, can enhance the attraction between the spectrins and lipid domains. The mutation leads to the decrease of the structural stability of spectrins and increases the curvature of the lipid bilayer. This work provides some theoretical insights into understanding the erythrocyte structure and the mechanism of some blood diseases.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11275097,11475085,11105122,and 11535005the Jiangsu Planned Projects for Postdoctoral Research Funds under Grant No 1402006C
文摘Generally speaking, the quark propagator is dependent on the quark chemical potential in the dense quantum chromodynamics （QCD）. By means of the generating functional method, we prove that the quark propagator actually depends on p4 ＋ iμ from the first principle of QCD. The relation between quark number density and quark condensate is discussed by analyzing their singularities. It is concluded that the quark number density has some singularities at certain # when T = 0, and the variations of the quark number density as well as the quark condensate are located at the same point. In other words, at a certain # the quark number density turns to nonzero, while the quark condensate begins to decrease from its vacuum value.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11174254)the National Basic Research Program of China (Grant Nos. 2011CBA00103 and 2009CB929104)
文摘The dynamics of quantum discord for two identical qubits in two independent single-mode cavities and a common single-mode cavity are discussed. For the initial Bell state with correlated spins, while the entanglement sudden death can occur, the quantum discord vanishes only at discrete moments in the independent cavities and never vanishes in the common cavity. Interestingly, quantum discord and entanglement show opposite behavior in the common cavity, unlike in the independent cavities. For the initial Bell state with anti-correlated spins, quantum discord and entanglement behave in the same way for both independent cavities and a common cavity. It is found that the detunings always stabilize the quantum discord.
基金Supported by National Natural Science Foundation of China under Grant No. 10974180
文摘Using cluster Monte Carlo method, we numerically investigate the coupling on the simple cubic lattice. We determine critical lines belong to the criticality in the XY model with nematic three-dimensional XY universality class in variable of θ （2θ） between the XY-ferromagnetic （nematic） and disordered states. Fhrthermore, the phase transition between the XY-ferromagnetic and the nematie states is found to be in the three-dimensional Ising universality class. The critical points are determined from the intersections of Binder ratios for various system sizes. With two sets of critical points obtained, we finally construct the phase diagram on the A-J plane.
基金Project supported by the National Natural Science Foundation of China(Grant No.11904155)。
文摘The Janus monolayer transition metal dichalcogenides(TMDs)MXY(M=Mo,W,etc.and X,Y=S,Se,etc.)have been successfully synthesized in recent years.The Rashba spin splitting in these compounds arises due to the breaking of out-of-plane mirror symmetry.Here we study the pairing symmetry of superconducting Janus monolayer TMDs within the weak-coupling framework near critical temperature Tc,of which the Fermi surface(FS)sheets centered around bothΓand K(K′)points.We find that the strong Rashba splitting produces two kinds of topological superconducting states which differ from that in its parent compounds.More specifically,at relatively high chemical potentials,we obtain a timereversal invariant s+f+p-wave mixed superconducting state,which is fully gapped and topologically nontrivial,i.e.,a Z_(2) topological state.On the other hand,a time-reversal symmetry breaking d+p+f-wave superconducting state appears at lower chemical potentials.This state possess a large Chern number|C|=6 at appropriate pairing strength,demonstrating its nontrivial band topology.Our results suggest the Janus monolayer TMDs to be a promising candidate for the intrinsic helical and chiral topological superconductors.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11105122,11275097 and 11475085the Foundation of Graduate School of Nanjing University under Grant No 2014CL02
文摘We calculate the quark number susceptibility （QNS） around the chiral critical end point （CEP）. The CEP is found to be located at （μc,Tc）= （80 MeV, 148 MeV） where μc and Tc are the critical chemical potential and temperature, respectively. The QNS is found to have the highest and sharpest peak at the CEP. It is also found that, when the chemical potential μ is in the range of 60MeV≤ μ ≤ 110MeV, the QNS near the transition temperature is larger than the free field result, which indicates that the space-like damping mode dominates the degree of freedom of motion near the CEP.
基金supported by the National Natural Science Foundation of China (Grants Nos. 11174254 and 11104363)the National Basic Research Program of China (Grant Nos. 2011CBA00103 and 2009CB929104)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20110191120046)
文摘An effective scheme within two displaced bosonic operators with equal positive and negative displacements is extended to study qubit-oscillator systems analytically in a unified way. Many previous analytical treatments, such as generalized rotating-wave approximation （GRWA） [Phys. Rev. Lett. 99, 173601 （2007）] and an expansion in the qubit tunneling matrix element in the deep strong coupling regime [Phys. Rev. Lett. 105, 263603 （2010）] can be recovered straightforwardly within the present scheme. Moreover, further improving GRWA and the extension to the finite-bias case are implemented easily. The algebraic formulae for the eigensolutions are then derived explicitly and uniquely, which work well in a wide range of the coupling strengths, detunings, and static bias including the recent experimentally accessible parameters. The dynamics of the qubit for an oscillator in the ground state is also studied. At the experimentally accessible coupling regime, GRWA can always work well. When the coupling is enhanced to the intermediate regime, only the improving GRWA can give the correct description, while the result of GRWA shows strong deviations. The previous Van Vleck perturbation theory is not valid to describe the dynamics in the present-day experimentally accessible regime, except for the strongly biased cases.
基金Supported in part by the Postdoctoral Science Foundation of China under Grant No 20100471308the National Natural Science Foundation of China under Grant Nos 11105122,10935001 and 11075075the Priority Academic Program Development of Jiangsu Higher Education Institution.
文摘From the graphical representation of the Dyson-Schwinger equation for the dressed gluon propagator it is shown that the gluon propagator in the Wigner phase should be different from that in the Nambu phase.Based on this analysis,we propose a modified gluon propagator to reflect this fact.With such a modified gluon propagator,in the framework of the Nambu Jona Lasinio (NJL) model,we obtain the Wigner solution to the quark gap equation at finite current quark mass,which has not been found in literature.This provides a new point of view to study partial restoration of chiral symmetry at finite temperature and chemical potential.
基金Supported by the National Natural Science Foundation of China under Grant No 11174254the National Basic Research Program of China under Grant No 2009CB929104.
文摘Recent measurement on an LC resonator magnetically coupled to a superconducting qubit [Phys.Rev.Lett.105 (2010)237001] shows that the system operates in the ultra-strong coupling regime and crosses the limit of validity for the rotating-wave approximation of the Jaynes-Cummings model By using extended bosonic coherent states,we solve the Jaynes-Cummings model exactly without using the rotating-wave approximation.Our numerically exact results for the spectrum of the flux qubit coupled to the LC resonator are fully consistent with the experimental observations.The smallest Bloch-Siegert shift obtained is consistent with that observed in this experiment.In addition,the Bloch-Siegert shifts in arbitrary level transitions and for arbitrary coupling constants are predicted.
基金Supported in part by the National Natural Science Foundation of China under Grants Nos 11275097,10935001 and 11075075the Research Fund for the Doctoral Program of Higher Education under Grant No 2012009111002.
文摘Taking into account the effect of the generalized Gor'kov and Melik-Barkhudarov(GMB)approximation,we calculate the radio-frequency spectra of balanced and homogeneous ultracold Fermi gases within the framework of the non-self-consistent T-matrix approximation at unitarity in the normal phase.The corresponding equations are numerically calculated on the real frequency axis directly.It is found that our results agree well with the experimental result of the radio-frequency spectroscopy[Phys.Rev.Lett.101(2008)140403].
