In this paper the influence of a knot on the structure of a polymethylene （PM） strand in the tensile process is investigated by using the steered molecular dynamics （SMD） method. The gradual increasing of end-to-e...In this paper the influence of a knot on the structure of a polymethylene （PM） strand in the tensile process is investigated by using the steered molecular dynamics （SMD） method. The gradual increasing of end-to-end distance, R, results in a tighter knot and a more stretched contour. That the break in a knotted rope almost invariably occurs at a point just outside the ＇entrance＇ to the knot, which has been shown in a good many experiments, is further theoretically verified in this paper through the calculation of some structural and thermodynamic parameters. Moreover, it is found that the analyses on bond length, torsion angle and strain energy can facilitate to the study of the localization and the size of a knot in the tensile process. The symmetries of torsion angles, bond lengths and bond angles in the knot result in the whole symmetry of the knot in microstructure, thereby adapting itself to the strain applied. Additionally, the statistical property of the force-dependent average knot size illuminates in detail the change in size of a knot with force f, and therefore the minimum size of the knot in the restriction of the potentials considered in this work for a PM chain is deduced. At the same time, the difference in response to uniaxial strain, between a knotted PM strand and an unknotted one is also investigated. The force-extension profile is easily obtained from the simulation. As expected, for a given f, the knotted chain has an R significantly smaller than that of an unknotted polymer. However, the scaled difference becomes less pronounced for larger values of N, and the results for longer chains approach those of the unknotted chains.展开更多
<span style="font-family:Verdana;">The paper reassesse</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family...<span style="font-family:Verdana;">The paper reassesse</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">s</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> a survival at tumor recurrence in soft matter.</span></span></span><span><span><span style="font-size:11.0pt;"> </span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">First, the </span><span style="font-family:Verdana;">stability of structural motifs</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">under shear in clusters of dipolar spheres is</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> characterized.</span><span style="font-family:Verdana;"> Next, there are introduced transitions between polymer</span><span style="font-family:Verdana;"> knots and </span><span style="font-family:Verdana;">rhythms of these transitions are obtained. </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">The </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">sensor is built for these</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> rhythms. Treatment, with a tensile force protocol, is modeled, wh</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">en</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> the tu</span><span style="font-family:Verdana;">mor in soft matter is observed by the above sensor. Survival probability, at</span><span style="font-family:Verdana;"> tumor recurrence in soft matter, is defined for the treatment with a tensile force protocol.</span><span style="font-family:Verdana;"> It is stated that the survival probability at a tensile force protocol</span><span style="font-family:Verdana;"> treat</span><span style="font-family:Verdana;">ment in</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">soft matter confirms or specifies the prognostic survival of 32 patients with</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> breast cancer.</span></span></span>展开更多
The translocation of a polymer through a pore that is much smaller than its size is a fundamental and actively researched topic in polymer physics.An understanding of the principles governing polymer translocation pro...The translocation of a polymer through a pore that is much smaller than its size is a fundamental and actively researched topic in polymer physics.An understanding of the principles governing polymer translocation provides important guidance for various practical applications,such as the separation and purification of polymers,nanopore-based single-molecule deoxyribonucleic acid/ribonucleic acid(DNA/RNA)sequencing,transmembrane transport of DNA or RNA,and infection of bacterial cells by bacteriophages.The past several decades have seen great progresses on the study of polymer translocation.Here we present an overview of theoretical,experimental,and simulational stduies on polymer translocation,focusing on the roles played by several important factors,including initial polymer conformations,external fields,polymer topology and architectures,and confinement degree.We highlight the physical mechanisms of different types of polymer translocations,and the main controversies about the basic rules of translocation dynamics.We compare and contrast the behaviors of force-induced versus flow-induced translocations and the effects of unknotted versus knotted polymers.Finally,we mention several opportunities and challenges in the study of polymer translocation.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos 20274040,20574052 and 20774066)the Program for New Century Excellent Talents in University,China (Grant No NCET-05-0538)the Natural Science Foundation of Zhejiang Province,China (Grant No R404047)
文摘In this paper the influence of a knot on the structure of a polymethylene （PM） strand in the tensile process is investigated by using the steered molecular dynamics （SMD） method. The gradual increasing of end-to-end distance, R, results in a tighter knot and a more stretched contour. That the break in a knotted rope almost invariably occurs at a point just outside the ＇entrance＇ to the knot, which has been shown in a good many experiments, is further theoretically verified in this paper through the calculation of some structural and thermodynamic parameters. Moreover, it is found that the analyses on bond length, torsion angle and strain energy can facilitate to the study of the localization and the size of a knot in the tensile process. The symmetries of torsion angles, bond lengths and bond angles in the knot result in the whole symmetry of the knot in microstructure, thereby adapting itself to the strain applied. Additionally, the statistical property of the force-dependent average knot size illuminates in detail the change in size of a knot with force f, and therefore the minimum size of the knot in the restriction of the potentials considered in this work for a PM chain is deduced. At the same time, the difference in response to uniaxial strain, between a knotted PM strand and an unknotted one is also investigated. The force-extension profile is easily obtained from the simulation. As expected, for a given f, the knotted chain has an R significantly smaller than that of an unknotted polymer. However, the scaled difference becomes less pronounced for larger values of N, and the results for longer chains approach those of the unknotted chains.
文摘<span style="font-family:Verdana;">The paper reassesse</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">s</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> a survival at tumor recurrence in soft matter.</span></span></span><span><span><span style="font-size:11.0pt;"> </span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">First, the </span><span style="font-family:Verdana;">stability of structural motifs</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">under shear in clusters of dipolar spheres is</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> characterized.</span><span style="font-family:Verdana;"> Next, there are introduced transitions between polymer</span><span style="font-family:Verdana;"> knots and </span><span style="font-family:Verdana;">rhythms of these transitions are obtained. </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">The </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">sensor is built for these</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> rhythms. Treatment, with a tensile force protocol, is modeled, wh</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">en</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> the tu</span><span style="font-family:Verdana;">mor in soft matter is observed by the above sensor. Survival probability, at</span><span style="font-family:Verdana;"> tumor recurrence in soft matter, is defined for the treatment with a tensile force protocol.</span><span style="font-family:Verdana;"> It is stated that the survival probability at a tensile force protocol</span><span style="font-family:Verdana;"> treat</span><span style="font-family:Verdana;">ment in</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">soft matter confirms or specifies the prognostic survival of 32 patients with</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> breast cancer.</span></span></span>
基金financially supported by the National Key R&D Program of China(No.2020YFA0713601)the National Natural Science Foundation of China(Nos.22073092 and 21790340)the Programs of Chinese Academy of Sciences(No.QYZDYSSW-SLH027)。
文摘The translocation of a polymer through a pore that is much smaller than its size is a fundamental and actively researched topic in polymer physics.An understanding of the principles governing polymer translocation provides important guidance for various practical applications,such as the separation and purification of polymers,nanopore-based single-molecule deoxyribonucleic acid/ribonucleic acid(DNA/RNA)sequencing,transmembrane transport of DNA or RNA,and infection of bacterial cells by bacteriophages.The past several decades have seen great progresses on the study of polymer translocation.Here we present an overview of theoretical,experimental,and simulational stduies on polymer translocation,focusing on the roles played by several important factors,including initial polymer conformations,external fields,polymer topology and architectures,and confinement degree.We highlight the physical mechanisms of different types of polymer translocations,and the main controversies about the basic rules of translocation dynamics.We compare and contrast the behaviors of force-induced versus flow-induced translocations and the effects of unknotted versus knotted polymers.Finally,we mention several opportunities and challenges in the study of polymer translocation.
