Pyrimidine nucleoside phosphorylase(PYNP) catalyzes the reversible phosphorolysis of pyrimidines in the nucleotide synthesis salvage pathway. The enzyme has two structure states: non-active opened structure and active...Pyrimidine nucleoside phosphorylase(PYNP) catalyzes the reversible phosphorolysis of pyrimidines in the nucleotide synthesis salvage pathway. The enzyme has two structure states: non-active opened structure and active closed structure. During change from non-active opened structure to active closed structure, the protein loop connecting domain α to domain α/β becomes bent remarkablely, which results in two domains closed up, and binding pocket reduce obviously. Setting about from the inactive-open X-ray structure, applying the method of molecular dynamic simulation, putting the ligand in the active-pocket, we carry out a dynamic simulation in the CVFF force-field for the entire system. The structures obstained are more approximately to the active-close X-ray structures, it proves that the rigid movement of the domains is arouse by the inducing effect of the ligand molecules.展开更多
Based on the nonlinear displacement-strain relationship,the virtual work principle method was used to establish the nonlinear equilibrium equations of steel beams with semi-rigid connections under vertical uniform loa...Based on the nonlinear displacement-strain relationship,the virtual work principle method was used to establish the nonlinear equilibrium equations of steel beams with semi-rigid connections under vertical uniform loads and temperature change.Considering the non-uniform temperature distribution across the thickness of beams,the formulas for stresses and vertical displacements were presented.On the basis of a flowchart for analysis of the numerical example,the effect of temperature change on the elastic behavior of steel beams was investigated.It is found that the maximal stress is mainly influenced by axial temperature change,and the maximal vertical displacement is principally affected by temperature gradients.And the effect of temperature gradients on the maximal vertical displacement decreases with the increase of rotational stiffness of joints.Both the maximal stress and vertical displacement decrease with the increase of rotational stiffness of joints.It can be concluded that the effects of temperature changes and rotational stiffness of joints on the elastic behavior of steel beams are significant.However,the influence of rotational stiffness becomes smaller when the rotational stiffness is larger.展开更多
文摘Pyrimidine nucleoside phosphorylase(PYNP) catalyzes the reversible phosphorolysis of pyrimidines in the nucleotide synthesis salvage pathway. The enzyme has two structure states: non-active opened structure and active closed structure. During change from non-active opened structure to active closed structure, the protein loop connecting domain α to domain α/β becomes bent remarkablely, which results in two domains closed up, and binding pocket reduce obviously. Setting about from the inactive-open X-ray structure, applying the method of molecular dynamic simulation, putting the ligand in the active-pocket, we carry out a dynamic simulation in the CVFF force-field for the entire system. The structures obstained are more approximately to the active-close X-ray structures, it proves that the rigid movement of the domains is arouse by the inducing effect of the ligand molecules.
基金Project(50478075) supported by the National Natural Science Foundation of ChinaProject(YBJJ0817) supported by Scientific Research Foundation of Graduate School of Southeast University
文摘Based on the nonlinear displacement-strain relationship,the virtual work principle method was used to establish the nonlinear equilibrium equations of steel beams with semi-rigid connections under vertical uniform loads and temperature change.Considering the non-uniform temperature distribution across the thickness of beams,the formulas for stresses and vertical displacements were presented.On the basis of a flowchart for analysis of the numerical example,the effect of temperature change on the elastic behavior of steel beams was investigated.It is found that the maximal stress is mainly influenced by axial temperature change,and the maximal vertical displacement is principally affected by temperature gradients.And the effect of temperature gradients on the maximal vertical displacement decreases with the increase of rotational stiffness of joints.Both the maximal stress and vertical displacement decrease with the increase of rotational stiffness of joints.It can be concluded that the effects of temperature changes and rotational stiffness of joints on the elastic behavior of steel beams are significant.However,the influence of rotational stiffness becomes smaller when the rotational stiffness is larger.
