In kinesin＇s mechanochemical cycle, ATP＇s binding to the nucleotide-free leading head is exquisitely gated so that futile hydrolysis is effectively avoided, Experiments show that, when both kinesin heads bind to a m...In kinesin＇s mechanochemical cycle, ATP＇s binding to the nucleotide-free leading head is exquisitely gated so that futile hydrolysis is effectively avoided, Experiments show that, when both kinesin heads bind to a microtubule~ ATP cannot bind to kinesin＇s leading head when the neck linker （NL） of this head has a backward orientation. How NL＇s backward orientation is maintained needs understanding on a structural basis. By using steered molecular dynamics and rrmtation simulations, we investigate the backward-pointing conformation of the leading head＇s NL under different inter-head tensions. We find that the NL cannot keep in a strict backward orientation solely by the inter-head tension. LYS325 （amino acid sequence in 2KIN） has an assistant locking function which locks the NL and β0 to the β-domain. This locking function has an enhanced positive cooperation with the inter-head tension. When the inter-head tension is weakened, this locking function can be broken, resulting in a loose backward orientation of the NL. The difference between the strict and loose backward orientation of the NL might be a crucial factor in the gating mechanism. These results are consistent with relevant experiments and proposals.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 total charge-changing cross sections and partial cross sections for the production of projectile fragments are measured in the interactions of 400 A MeV 20 Ne with aluminum,carbon and polyethylene targets sandwich...The total charge-changing cross sections and partial cross sections for the production of projectile fragments are measured in the interactions of 400 A MeV 20 Ne with aluminum,carbon and polyethylene targets sandwiched with CR-39 plastic nuclear track detectors.The measured total charge-changing cross sections are compared with the predictions using the Bradt-Peters semi-empirical formula,and the NUCFRAG2 and PHITS models.It is shown that the measured experimental results are in good agreement with the theoretical model prediction and other experimental results,and it can be clearly seen that the partial cross sections for fragment production show obvious odd-even effects.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 90403007, 10975044 and 10975019, the Foundation of the Ministry of Personnel of China for Returned Scholars under Grant No MOP2006138, the Eundamental Research Funds for the Central University and the Key Subject Construction Project of Hebei Provincial Universities.
文摘In kinesin＇s mechanochemical cycle, ATP＇s binding to the nucleotide-free leading head is exquisitely gated so that futile hydrolysis is effectively avoided, Experiments show that, when both kinesin heads bind to a microtubule~ ATP cannot bind to kinesin＇s leading head when the neck linker （NL） of this head has a backward orientation. How NL＇s backward orientation is maintained needs understanding on a structural basis. By using steered molecular dynamics and rrmtation simulations, we investigate the backward-pointing conformation of the leading head＇s NL under different inter-head tensions. We find that the NL cannot keep in a strict backward orientation solely by the inter-head tension. LYS325 （amino acid sequence in 2KIN） has an assistant locking function which locks the NL and β0 to the β-domain. This locking function has an enhanced positive cooperation with the inter-head tension. When the inter-head tension is weakened, this locking function can be broken, resulting in a loose backward orientation of the NL. The difference between the strict and loose backward orientation of the NL might be a crucial factor in the gating mechanism. These results are consistent with relevant experiments and proposals.
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 National Natural Science Foundation of China (11075100,10975019)Shanxi Provincial Foundation for Returned Overseas Chinese Scholars,China (2011-058)+1 种基金Natural Science Foundation of Shanxi Province,China (2011011001-2)Scientific Research Foundation for Returned Overseas Chinese Scholars,Ministry of Personnel (MOP2006138)
文摘The total charge-changing cross sections and partial cross sections for the production of projectile fragments are measured in the interactions of 400 A MeV 20 Ne with aluminum,carbon and polyethylene targets sandwiched with CR-39 plastic nuclear track detectors.The measured total charge-changing cross sections are compared with the predictions using the Bradt-Peters semi-empirical formula,and the NUCFRAG2 and PHITS models.It is shown that the measured experimental results are in good agreement with the theoretical model prediction and other experimental results,and it can be clearly seen that the partial cross sections for fragment production show obvious odd-even effects.
