Exploiting the nonlinear dynamics in the negative feedback loop, we propose a statistical signal-response model to describe the different oscillatory behaviour in a biological network motif. By choosing the delay as a...Exploiting the nonlinear dynamics in the negative feedback loop, we propose a statistical signal-response model to describe the different oscillatory behaviour in a biological network motif. By choosing the delay as a bifurcation parameter, we discuss the existence of Hopf bifurcation and the stability of the periodic solutions of model equations with the centre manifold theorem and the normal form theory. It is shown that a periodic solution is born in a Hopf bifurcation beyond a critical time delay, and thus the bifurcation phenomenon may be important to elucidate the mechanism of oscillatory activities in regulatory biological networks.展开更多
With the aid of stochastic delayed-feedback differential equations, we derive an analytic expression for the power spectra of reacting molecules included in a generic biological network motif that is incorporated with...With the aid of stochastic delayed-feedback differential equations, we derive an analytic expression for the power spectra of reacting molecules included in a generic biological network motif that is incorporated with a feedback mechanism and time delays in gene regulation. We systematically analyse the effects of time delays, the feedback mechanism, and biological stochasticity on the power spectra. It has been clarified that the time delays together with the feedback mechanism can induce stochastic oscillations at the molecular level and invalidate the noise addition rule for a modular description of the noise propagator. Delay-induced stochastic resonance can be expected, which is related to the stability loss of the reaction systems and Hopf bifurcation occurring for solutions of the corresponding deterministic reaction equations. Through the analysis of the power spectrum, a new approach is proposed to estimate the oscillation period.展开更多
The importance of stochasticity in cellular processes is increasingly recognized in both theoretical andexperimental studies.General features of stochasticity in gene regulation and expression are briefly reviewed in ...The importance of stochasticity in cellular processes is increasingly recognized in both theoretical andexperimental studies.General features of stochasticity in gene regulation and expression are briefly reviewed in thisarticle,which include the main experimental phenomena,classification,quantization and regulation of noises.Thecorrelation and transmission of noise in cascade networks are analyzed further and the stochastic simulation methodsthat can capture effects of intrinsic and extrinsic noise are described.展开更多
There have been many recent studies devoted to the consequences of stochasticity in protein circuitry. Stress conditions, including DNA damage, hypoxia, heat shock, nutrient deprivation, and oncogene activation, can r...There have been many recent studies devoted to the consequences of stochasticity in protein circuitry. Stress conditions, including DNA damage, hypoxia, heat shock, nutrient deprivation, and oncogene activation, can result in the activation and accumulation of p53. Several experimental studies show that oscillations can be induced by DNA damage following nuclear irradiation. To explore the underlying dynamical features and the role of stochasticity, we discuss the oscillatory dynamics in the well-studied regulatory network motif. The fluctuations around the fixed point of a delayed system are Gaussian in the limit of sufficiently weak delayed feedback, and remain Gaussian along a limit cycle when viewed tangential to the trajectory. The experimental results are recapitulated in this study. We illustrate several features of the p53 activities, which are robust when the parameters change. Furthermore, the distribution in protein abundance can be characterized by its non-Gaussian nature.展开更多
How ATP binding initiates the docking process of kinesin's neck linker is a key question in understanding kinesin mechanisms. By exploiting a molecular dynamics method, we investigate the initial conformation of kine...How ATP binding initiates the docking process of kinesin's neck linker is a key question in understanding kinesin mechanisms. By exploiting a molecular dynamics method, we investigate the initial conformation of kinesin's neck linker in its docking process. We find that, in the initial conformation, the neck linker has interactions with /30 and forms a 'cover-neck bundle' structure with/30. From this initial structure, the formation of extra turns and the docking of the cover- neck bundle structure can be achieved. The motor head provides a forward force on the initial cover-neck bundle structure through ATP-induced rotation. This force, together with the hydrophobic interaction of ILE327 with the hydrophobic pocket on the motor head, drives the formation of the extra turn and initiates the neck linker docking process. Based on these findings, a pathway from ATP binding-induced motor head rotation to neck linker docking is proposed.展开更多
We investigate the structure of yrast bands in the transuranium nuclei ^(242)Pu and ^(244)Pu in the framework of the projected shell model,which is a fully quantum mechanical and microscopic approach.It is found that ...We investigate the structure of yrast bands in the transuranium nuclei ^(242)Pu and ^(244)Pu in the framework of the projected shell model,which is a fully quantum mechanical and microscopic approach.It is found that an appropriate modification of the standard Nilsson spin-orbital parameters in the N =6 proton shell is necessary to correctly describe the high-spin backbending phenomenon in nucleus ^(244)Pu.In order to test whether this modification is correct,the same modified parameters are used to calculate the yrast band of its neighboring isotope ^(242)Pu.It is found that without this modification,a backbending will occur at spin I =20,which is not supported by the experimental data.展开更多
The tumour suppressor p53 is a transcription factor that regulates multiple biological functions including metabolism, DNA repair, cell cycle arrest, apoptosis and senescence. About half of human cancers show a normal...The tumour suppressor p53 is a transcription factor that regulates multiple biological functions including metabolism, DNA repair, cell cycle arrest, apoptosis and senescence. About half of human cancers show a normal TP53 gene and aberrant overexpression of Mdm2. This fact promotes a promising cancer therapeutic strategy by inhibiting the interactions between p53 and Mdm2. Various inhibitors have been designed to achieve this novel approach for cancer therapy. However, the detailed competition mechanism between these inhibitors and the p53 molecule in their binding process to Mdm2 is still unclear. We investigate this competition mechanism between Nutlin3 and p53 using molecular dynamics simulations. It is found that Nutlin3 binds faster than the p53 molecule to Mdm2 to prevent p53 binding to Mdm2 when Nutlin3 and p53 have equal distance from Mdm2. Nutlin3 can also bind to the p53-Mdm2 complex to disturb and weaken the interactions between p53 and Mdm2. Consequently, p53 cannot bind to Mdm2 and its tumour suppression function is reactivated. These results provide the detailed competition mechanism between Nutlin3 and p53 in their binding to Mdm2. Because the binding site of most other inhibitors to Mdm2 is the same as Nutlin3, therefore this competition mechanism can extend to most inhibitors which target the p53-Mdm2 interaction.展开更多
the collision of very heavy nuclei ^197Au+^197Au at 15AMeV has been studied within the improved quantum molecular dynamics model. A class of ternary events satisfying nearly complete balance of mass numbers is select...the collision of very heavy nuclei ^197Au+^197Au at 15AMeV has been studied within the improved quantum molecular dynamics model. A class of ternary events satisfying nearly complete balance of mass numbers is selected. The experimental mass distributions for the system ^197Au+^197Au ternary fission fragments, the heaviest(A1), the intermediate (A2) and the lightest (A3), are reproduced well. The mean free path of nucleons in the reaction system is studied and the shorter mean free path is responsible for the ternary fission with three mass comparable fragments, in which the two-body dissipation mechanism plays a dominant role.展开更多
Ternary fission in ^197Au+^197Au collisions at 15 A MeV is investigated by using the improved quantum molecular dynamical (ImQMD) model. The experimental mass distributions for each of the three fragments are repro...Ternary fission in ^197Au+^197Au collisions at 15 A MeV is investigated by using the improved quantum molecular dynamical (ImQMD) model. The experimental mass distributions for each of the three fragments are reproduced for the first time without any freely adjusting parameters. The mechanisms of ternary fission in central and semicentral collisions are dynamically studied. In direct prolate ternary fission, two necks are found to be formed almost simultaneously and rupture sequentially in a very short time interval. Direct oblate ternary fission is a very rare fission event, in which three necks are formed and rupture simultaneously, forming three equally sized fragments along space-symmetric directions in the reaction plane. In sequential ternary fission a binary division is followed by another binary fission event after hundreds of fm/c.展开更多
研究了15 Me V/u197Au+197Au体系三裂变反应过程中体系的集体运动动能、核-核相互作用势、集体运动总动能以及核子激发能的演化过程,并讨论了该反应过程的能量耗散问题。通过与两裂变时体系总动能εtot和Θc.m.关联图作对比,初步得出三...研究了15 Me V/u197Au+197Au体系三裂变反应过程中体系的集体运动动能、核-核相互作用势、集体运动总动能以及核子激发能的演化过程,并讨论了该反应过程的能量耗散问题。通过与两裂变时体系总动能εtot和Θc.m.关联图作对比,初步得出三裂变反应体系的第一次裂变是极端深度非弹性散射过程;进一步分析了三裂变与两裂变反应体系总动能与碰撞参数的关系,发现小碰撞参数下两裂变比三裂变反应耗散的能量多大约150 Me V,大碰撞参数下三裂变比两裂变反应多消耗300 Me V。展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 10475008 and 10435020, the Scientific Research Foundation for the Returned 0verseas Chinese Scholars, Ministry of Personnel of China under Grant No M0P2006138, the Ministry of Education of China under Grant No 2005383, the Foundations for Excellent Scientists of Beijing under Grant No 20041D1300120.
文摘Exploiting the nonlinear dynamics in the negative feedback loop, we propose a statistical signal-response model to describe the different oscillatory behaviour in a biological network motif. By choosing the delay as a bifurcation parameter, we discuss the existence of Hopf bifurcation and the stability of the periodic solutions of model equations with the centre manifold theorem and the normal form theory. It is shown that a periodic solution is born in a Hopf bifurcation beyond a critical time delay, and thus the bifurcation phenomenon may be important to elucidate the mechanism of oscillatory activities in regulatory biological networks.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10975019)the Foundation of the Ministry of Personnel of China for Returned Scholars (Grant No. MOP2006138)the Fundamental Research Funds for the Central Universities
文摘With the aid of stochastic delayed-feedback differential equations, we derive an analytic expression for the power spectra of reacting molecules included in a generic biological network motif that is incorporated with a feedback mechanism and time delays in gene regulation. We systematically analyse the effects of time delays, the feedback mechanism, and biological stochasticity on the power spectra. It has been clarified that the time delays together with the feedback mechanism can induce stochastic oscillations at the molecular level and invalidate the noise addition rule for a modular description of the noise propagator. Delay-induced stochastic resonance can be expected, which is related to the stability loss of the reaction systems and Hopf bifurcation occurring for solutions of the corresponding deterministic reaction equations. Through the analysis of the power spectrum, a new approach is proposed to estimate the oscillation period.
基金Supported by the National Natural Science Foundation of China under Grant No.10975019the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Personnel of China under Grant No.MOP2006138
基金Supported by the Ministry of Science and Technology of China under Grant No. 2012CB934001the National Natural Science Foundation of China under Grant No. 10975019+1 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Personnel of China under Grant No. MOP2006138the Fundamental Research Funds for the Central Universities, and Y1515530U1
文摘The importance of stochasticity in cellular processes is increasingly recognized in both theoretical andexperimental studies.General features of stochasticity in gene regulation and expression are briefly reviewed in thisarticle,which include the main experimental phenomena,classification,quantization and regulation of noises.Thecorrelation and transmission of noise in cascade networks are analyzed further and the stochastic simulation methodsthat can capture effects of intrinsic and extrinsic noise are described.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10975019)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Personnel of China (Grant No. MOP2006138)+1 种基金the Fundamental Research Funds for the Central Universitiesthe Science Foundation of the Ministry of Science and Technology of China (Grant No. 2012CB934001)
文摘There have been many recent studies devoted to the consequences of stochasticity in protein circuitry. Stress conditions, including DNA damage, hypoxia, heat shock, nutrient deprivation, and oncogene activation, can result in the activation and accumulation of p53. Several experimental studies show that oscillations can be induced by DNA damage following nuclear irradiation. To explore the underlying dynamical features and the role of stochasticity, we discuss the oscillatory dynamics in the well-studied regulatory network motif. The fluctuations around the fixed point of a delayed system are Gaussian in the limit of sufficiently weak delayed feedback, and remain Gaussian along a limit cycle when viewed tangential to the trajectory. The experimental results are recapitulated in this study. We illustrate several features of the p53 activities, which are robust when the parameters change. Furthermore, the distribution in protein abundance can be characterized by its non-Gaussian nature.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10975044 and 10975019)the Foundation of the Ministry of Personnel of China for Returned Scholars(Grant No.MOP2006138)the Fundamental Research Funds for the Central University,and the Key Subject Construction Project of Hebei Provincial Universities
文摘How ATP binding initiates the docking process of kinesin's neck linker is a key question in understanding kinesin mechanisms. By exploiting a molecular dynamics method, we investigate the initial conformation of kinesin's neck linker in its docking process. We find that, in the initial conformation, the neck linker has interactions with /30 and forms a 'cover-neck bundle' structure with/30. From this initial structure, the formation of extra turns and the docking of the cover- neck bundle structure can be achieved. The motor head provides a forward force on the initial cover-neck bundle structure through ATP-induced rotation. This force, together with the hydrophobic interaction of ILE327 with the hydrophobic pocket on the motor head, drives the formation of the extra turn and initiates the neck linker docking process. Based on these findings, a pathway from ATP binding-induced motor head rotation to neck linker docking is proposed.
基金Supported by Suranaree University of Technology under Grant No 15/2553the National Basic Research Development Program of China under Grant No 2007CB815003the National Natural Science Foundation of China under Grant Nos 10975190,11065001,10975019,10675170 and 61067001.
文摘We investigate the structure of yrast bands in the transuranium nuclei ^(242)Pu and ^(244)Pu in the framework of the projected shell model,which is a fully quantum mechanical and microscopic approach.It is found that an appropriate modification of the standard Nilsson spin-orbital parameters in the N =6 proton shell is necessary to correctly describe the high-spin backbending phenomenon in nucleus ^(244)Pu.In order to test whether this modification is correct,the same modified parameters are used to calculate the yrast band of its neighboring isotope ^(242)Pu.It is found that without this modification,a backbending will occur at spin I =20,which is not supported by the experimental data.
基金Supported by the National Natural Science Foundation of China under Grant No 11675018the Beijing Natural Science Foundation under Grant No 1172008the Fundamental Research Funds for the Central Universities under Grant No 2015KJJCB01
文摘The tumour suppressor p53 is a transcription factor that regulates multiple biological functions including metabolism, DNA repair, cell cycle arrest, apoptosis and senescence. About half of human cancers show a normal TP53 gene and aberrant overexpression of Mdm2. This fact promotes a promising cancer therapeutic strategy by inhibiting the interactions between p53 and Mdm2. Various inhibitors have been designed to achieve this novel approach for cancer therapy. However, the detailed competition mechanism between these inhibitors and the p53 molecule in their binding process to Mdm2 is still unclear. We investigate this competition mechanism between Nutlin3 and p53 using molecular dynamics simulations. It is found that Nutlin3 binds faster than the p53 molecule to Mdm2 to prevent p53 binding to Mdm2 when Nutlin3 and p53 have equal distance from Mdm2. Nutlin3 can also bind to the p53-Mdm2 complex to disturb and weaken the interactions between p53 and Mdm2. Consequently, p53 cannot bind to Mdm2 and its tumour suppression function is reactivated. These results provide the detailed competition mechanism between Nutlin3 and p53 in their binding to Mdm2. Because the binding site of most other inhibitors to Mdm2 is the same as Nutlin3, therefore this competition mechanism can extend to most inhibitors which target the p53-Mdm2 interaction.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10475008, 10675172 and 10875031, and Ministry of Personnel under Grant No MOP2006138 and Ministry of Education of China under Grant No MOE2005383 and the Major State Basic Research Program under Grant No 2007CB209900.
文摘the collision of very heavy nuclei ^197Au+^197Au at 15AMeV has been studied within the improved quantum molecular dynamics model. A class of ternary events satisfying nearly complete balance of mass numbers is selected. The experimental mass distributions for the system ^197Au+^197Au ternary fission fragments, the heaviest(A1), the intermediate (A2) and the lightest (A3), are reproduced well. The mean free path of nucleons in the reaction system is studied and the shorter mean free path is responsible for the ternary fission with three mass comparable fragments, in which the two-body dissipation mechanism plays a dominant role.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10875031 and 10675172, and the Ministry of Personnel under Grant No MOP2006138 and the Ministry of Education of China under Grant No MOE2005383, and the National Basic Research Program under Grant No 2007CB209900.
文摘Ternary fission in ^197Au+^197Au collisions at 15 A MeV is investigated by using the improved quantum molecular dynamical (ImQMD) model. The experimental mass distributions for each of the three fragments are reproduced for the first time without any freely adjusting parameters. The mechanisms of ternary fission in central and semicentral collisions are dynamically studied. In direct prolate ternary fission, two necks are found to be formed almost simultaneously and rupture sequentially in a very short time interval. Direct oblate ternary fission is a very rare fission event, in which three necks are formed and rupture simultaneously, forming three equally sized fragments along space-symmetric directions in the reaction plane. In sequential ternary fission a binary division is followed by another binary fission event after hundreds of fm/c.
文摘研究了15 Me V/u197Au+197Au体系三裂变反应过程中体系的集体运动动能、核-核相互作用势、集体运动总动能以及核子激发能的演化过程,并讨论了该反应过程的能量耗散问题。通过与两裂变时体系总动能εtot和Θc.m.关联图作对比,初步得出三裂变反应体系的第一次裂变是极端深度非弹性散射过程;进一步分析了三裂变与两裂变反应体系总动能与碰撞参数的关系,发现小碰撞参数下两裂变比三裂变反应耗散的能量多大约150 Me V,大碰撞参数下三裂变比两裂变反应多消耗300 Me V。