Mainly for the problem that the friction force generated by the existing process of bind-ing,fixing and fastening the flexible cable on the satellite is unknown,the friction force analysis and experimental research on...Mainly for the problem that the friction force generated by the existing process of bind-ing,fixing and fastening the flexible cable on the satellite is unknown,the friction force analysis and experimental research on the binding point of the flexible cable are carried out.The equivalent model of the cable bundle bound by nylon cable ties is established,the force on the binding point is analyzed,and the empirical formula for calculating the friction force at the binding point is estab-lished.The formula shows that the friction force is related to the cable bundle diameter,the number of winding cycles of silicone rubber tape,the width of nylon cable ties,and the binding force.The friction force tests of the cable diameter of 5.06 mm,8.02 mm,24.02 mm,38.04 mm under different winding turns of tape were carried out,which was compared with the theoretical calculation value.It is concluded that the calculation accuracy of the theoretical model is more than 95%,which can estimate the actual friction force value accurately.This provides a reference and basis for the theoretical and experimental research on the friction force of the flexible cable binding point on satellite.展开更多
Conformational changes to 1,4-β-D-glucan cellobiohydrolase I(CBHI)in response to its binding with p-nitrophenylβ-D-cellobioside(PNPC)were analyzed by second-derivative fluorescence spectrometry at the saturation bin...Conformational changes to 1,4-β-D-glucan cellobiohydrolase I(CBHI)in response to its binding with p-nitrophenylβ-D-cellobioside(PNPC)were analyzed by second-derivative fluorescence spectrometry at the saturation binding point.Irreversible changes to the configuration of PNPC during the course of the binding process were characterized by UV spectral analysis.Isothermal titration calorimetry(ITC)was used to determine the stoichiometry of binding(i.e.the number of molar binding sites)of PNPC to CBHI.Two points on the surface of the CBHI molecule interact with PNPC,and irreversible changes to the configuration of PNPC occur during its conversion to p-nitrophenyl(PNP).The ITC studies demonstrated that the binding of PNPC to CBHI is an irreversible process,in which heat is released,but where there is no reversible equilibrium between PNPC-CBHI and CBHI and PNPC.On the other hand,PNP and cellobiose need to be released from the PNPC-CBHI complex to facilitate the repeated binding of new PNPC molecules to the renewable CBHI molecules.Therefore,we speculate that the energy,which powers the configurational change of PNPC as it is converted to PNP,is generated from cyclic changes in the conformation of CBHI during the binding/de-sorption process.These new insights may provide a basis for a better understanding of the binding mechanism in enzyme-substrate interactions.展开更多
基金supported by National Defense Basic Scientific Research Funding Project(No.JCKY2022203C048)Equipment Advanced Research Funding Program(No.41423010401).
文摘Mainly for the problem that the friction force generated by the existing process of bind-ing,fixing and fastening the flexible cable on the satellite is unknown,the friction force analysis and experimental research on the binding point of the flexible cable are carried out.The equivalent model of the cable bundle bound by nylon cable ties is established,the force on the binding point is analyzed,and the empirical formula for calculating the friction force at the binding point is estab-lished.The formula shows that the friction force is related to the cable bundle diameter,the number of winding cycles of silicone rubber tape,the width of nylon cable ties,and the binding force.The friction force tests of the cable diameter of 5.06 mm,8.02 mm,24.02 mm,38.04 mm under different winding turns of tape were carried out,which was compared with the theoretical calculation value.It is concluded that the calculation accuracy of the theoretical model is more than 95%,which can estimate the actual friction force value accurately.This provides a reference and basis for the theoretical and experimental research on the friction force of the flexible cable binding point on satellite.
基金the National Natural Science Foundation of China(Grant Nos.30370013 and 30500007)
文摘Conformational changes to 1,4-β-D-glucan cellobiohydrolase I(CBHI)in response to its binding with p-nitrophenylβ-D-cellobioside(PNPC)were analyzed by second-derivative fluorescence spectrometry at the saturation binding point.Irreversible changes to the configuration of PNPC during the course of the binding process were characterized by UV spectral analysis.Isothermal titration calorimetry(ITC)was used to determine the stoichiometry of binding(i.e.the number of molar binding sites)of PNPC to CBHI.Two points on the surface of the CBHI molecule interact with PNPC,and irreversible changes to the configuration of PNPC occur during its conversion to p-nitrophenyl(PNP).The ITC studies demonstrated that the binding of PNPC to CBHI is an irreversible process,in which heat is released,but where there is no reversible equilibrium between PNPC-CBHI and CBHI and PNPC.On the other hand,PNP and cellobiose need to be released from the PNPC-CBHI complex to facilitate the repeated binding of new PNPC molecules to the renewable CBHI molecules.Therefore,we speculate that the energy,which powers the configurational change of PNPC as it is converted to PNP,is generated from cyclic changes in the conformation of CBHI during the binding/de-sorption process.These new insights may provide a basis for a better understanding of the binding mechanism in enzyme-substrate interactions.
