Microtubules(MTs) are part of the cellular cytoskeleton and they play a role in many activities, such as cell division and maintenance of cell shape. In recent years, MTs have been thought to be involved in storing an...Microtubules(MTs) are part of the cellular cytoskeleton and they play a role in many activities, such as cell division and maintenance of cell shape. In recent years, MTs have been thought to be involved in storing and processing information.Several models have been developed to describe the information-processing ability of MTs. In these models, MTs are considered as a device that can transmit quantum information. However, MTs are affected by the "wet and warm" cellular environment, thus it is essential to calculate the decoherence time. Many researchers have attempted to calculate this parameter but the values that have been obtained vary markedly. Previous studies considered the cellular environment as a distant ion; however, this treatment is somewhat simplified. In this study, we develop a model to determine the decoherence time in neuronal MTs while considering the interaction effects of the neuronal fluid environment. The neuronal environment is considered as a plasmon reservoir. The coupling between MTs and neuronal environment occurs due to the interaction between dipoles and plasmon. The interaction Hamiltonian is derived by using the second quantization method, and the coupling coefficient is calculated. Finally, the decoherence time scale is estimated according to the interaction Hamiltonian.In this paper, the time scale of decoherence in MTs is approximately 1 fs-100 fs. This model may be used as a reference in other decoherence processes in biological tissues.展开更多
Among many types of proteinaceous filaments, microtubules （MTs） constitute the most rigid components of the cellular cytoskeleton. Microtubule dynamics is essential for many vital cellular processes such as intracel...Among many types of proteinaceous filaments, microtubules （MTs） constitute the most rigid components of the cellular cytoskeleton. Microtubule dynamics is essential for many vital cellular processes such as intracellular transport, metabolism, and cell division. We investigate the nonlinear dynamics of inhomogeneous microtubulin systems and the MT dynamics is found to be governed by a perturbed sine-Gordon equation. In the presence of various competing nonlinear inhomogeneities, it is shown that this nonlinear model can lead to the existence of kink and antikink solitons moving along MTs. We demonstrate kink-antikink pair collision in the framework of Hirota＇s bilinearization method. We conjecture that the collisions of the quanta of energy propagating in the form of kinks and antikinks may offer a new view of the mechanism of the retrograde and anterograde transport direction regulation of motor proteins in microtubulin systems.展开更多
We show how Jacobian elliptic functions （JEFs） can be used to solve ordinary differential equations （ODEs） describing the nonlinear dynamics of microtubules （MTs）. We demonstrate that only one of the JEFs can be...We show how Jacobian elliptic functions （JEFs） can be used to solve ordinary differential equations （ODEs） describing the nonlinear dynamics of microtubules （MTs）. We demonstrate that only one of the JEFs can be used while the remaining two do not represent the solutions of the crucial differential equation. We show that a kinkbtype soliton moves along MTs. Besides this solution, we also discuss a few more solutions that may or may not have physical meanings. Finally, we show what kind of ODE can be solved by using JEFs.展开更多
The control of dissipation and amplification of solitary waves in an electrical model of a microtubule is demonstrated.This model consists of a shunt nonlinear resistance–capacitance(J(V)–C(V)) circuit and a series ...The control of dissipation and amplification of solitary waves in an electrical model of a microtubule is demonstrated.This model consists of a shunt nonlinear resistance–capacitance(J(V)–C(V)) circuit and a series resistance–inductance(R–L) circuit. Through linear dispersion analysis, two features of the network are found, that is, low bandpass and bandpass filter characteristics. The effects of the conductance’s parameter λ on the linear dispersion curve are also analyzed. It appears that an increase of λ induces a decrease(an increase) of the width of the bandpass filter for positive(negative) values of λ. By applying the reductive perturbation method, we derive the equation governing the dynamics of the modulated waves in the system. This equation is the well-known nonlinear Schr?dinger equation extended by a linear term proportional to a hybrid parameter σ, i.e., a dissipation or amplification coefficient. Based on this parameter, we successfully demonstrate the hybrid behavior(dissipation and amplification) of the system. The exact and approximate solitary wave solutions of the obtained equation are derived, and the effects of the coefficient σ on the characteristic parameters of these waves are investigated. Using the analytical solutions found, we show numerically that the waves that are propagated throughout the system can be dissipated, amplified, or remain stable depending on the network parameters. These results are not only in agreement with the analytical predictions, but also with the existing experimental results in the literature.展开更多
Low-energy ion implantation, as a new technology to produce mutation in plant breeding, has been widely applied in agriculture in China. But so far there is a little understanding of the underlying mechanisms responsi...Low-energy ion implantation, as a new technology to produce mutation in plant breeding, has been widely applied in agriculture in China. But so far there is a little understanding of the underlying mechanisms responsible for its biological effects at the cellular level. Here we report the biological effects of a nitrogen ion beams of 30 keV on the pollen grains of Pinus thunbergii Parl. In general, ion implantation inhibited pollen germination. The dose-response curve presented a particular saddle-like pattern. Ion implantation also changed the dimension of the elongated tubes and significantly induced tip swelling. Confocal microscopy indicated that the pollen tube tips in P. thunbergii contained an enriched network of microtubules. Ion implantation led to the disruption of microtubules especially in swollen tips. Treatment with colchicine demonstrated that tip swelling was caused by the disruption of microtubules in the tip, indicating a unique role for microtubules in maintaining the tip integrality of the pollen tube in conifer. Our results suggest that ion implantation induce the disruption of microtubule organization in pollen and pollen tubes and subsequently cause morphological abnormalities in the pollen tubes. This study may provide a clue for further investigation on the interaction between low-energy ion beams and pollen tube growth.展开更多
A theoretical investigation on the structural and elastic properties of ZnO nanotubes is carried out by using atomistic calculations based on an inter-atomic pair potential within the shell-model approach. The calcula...A theoretical investigation on the structural and elastic properties of ZnO nanotubes is carried out by using atomistic calculations based on an inter-atomic pair potential within the shell-model approach. The calculation results are presented for the bond length, bond angle, radius dilation, strain energy, Young modulus and Poisson ratio as a function of tube radius. For small tube radius these properties depend on the helicity of the tube, while for the tube radius larger than 6.0A, they are independent of the tube radius and helicity except for the strain energy which decreases with increasing tube radius.展开更多
The human rectal adenocarcinoma cell line(HR8348)was treated withlympholdne activated killer(LAK)cells in vitro and the changes of the microtubulin inboth the effector and target cells were investigated with the aid o...The human rectal adenocarcinoma cell line(HR8348)was treated withlympholdne activated killer(LAK)cells in vitro and the changes of the microtubulin inboth the effector and target cells were investigated with the aid of immunofluorescencemicroscopy.It was revealed that after the attachment of LAK cells to the tumor cells,theeffector-target conjugates formed and distribution of the microtubulin in both the effectorand target cells changed.In the LAK cells,the microtubulin concentrated mainly in thecontact region,forming a crescent-like structure,while in the target cells,themicrotubulin condensed into patches and fused with the crescent-like structure of the LAKcells,Eventually,the target cells degenerated and died.It was suggested that the lysis ofthe target cells may be related to the redistribution of the microtubulin in both theeffector and target cells.展开更多
Taxol was used as a tool reagent and the function of the microtubules (MTs) beneath thepostsynaptic membrane was studied in an isolated non-uniformly stretched muscle preparation of ratdiaphragm.After exposure to taxo...Taxol was used as a tool reagent and the function of the microtubules (MTs) beneath thepostsynaptic membrane was studied in an isolated non-uniformly stretched muscle preparation of ratdiaphragm.After exposure to taxol (20 μmol/L,10min),the amplitude of acetylcholine potential ofinnervated muscle endplate was decreased by 30%,but the lime course of AChP and membrane po-tential remained unchanged.The results indicate that taxol can inhibit the responsiveness ofpostsynapfic membrane.It is therefore suggested that the site of action of taxol indudng inhibitionof postsynapfic responsiveness in neuromuscular junction may be the microtubules beneath thepostsynapfic membrane.展开更多
Microtubule self-organization under mechanical and chemical regulations plays a central role in cytokinesis and cel-lular transportations.In plant-cells,the patterns or phases of cortical microtubules organizations ar...Microtubule self-organization under mechanical and chemical regulations plays a central role in cytokinesis and cel-lular transportations.In plant-cells,the patterns or phases of cortical microtubules organizations are the direct indicators of cell-phases.The dense nematic pattern of cortical microtubule array relies on the regulation of single microtubule dynamics with mechanical coupling to steric interaction among the self-organized microtubule crowds.Building upon previous mini-mal models,we investigate the effective microtubule width,microtubule catastrophe rate,and zippering angle as factors that regulate the self-organization of the dense nematic phase.We find that by incorporating the effective microtubule width,the transition from isotropic to the highly ordered nematic phase(NI phase)with extremely long microtubules will be gapped by another nematic phase which consists of relative short microtubules(NII phase).The NII phase in the gap grows wider with the increase of the microtubule width.We further illustrate that in the dense phase,the collision-induced catastrophe rate and an optimal zippering angle play an important role in controlling the order-disorder transition,as a result of the coupling between the collision events and ordering.Our study shows that the transition to dense microtubule array requires the cross-talk between single microtubule growth and mechanical interactions among microtubules in the active crowds.展开更多
Gravitropic curvature growth of Arabidopsis hypocotyls mainly occurred in the rapid growing Elongation Zone(EZI),not in the slow-growing Elongation Zone(EZII).By examining reorientation of Microtubules(MT)and phenotyp...Gravitropic curvature growth of Arabidopsis hypocotyls mainly occurred in the rapid growing Elongation Zone(EZI),not in the slow-growing Elongation Zone(EZII).By examining reorientation of Microtubules(MT)and phenotype of the cell wall in the EZI and the EZII of Arabidopsis hypocotyls under normal gravitational condition,it is found that MTs in the rapid growing epidermal cells were mainly in the transverse direction,while those in the non-growing epidermal cells were in the longitudinal directions.However,this difference in cortical MT arrays between the EZI and EZII cells disappeared when the seedlings were exposed to the simulated microgravity condition on a horizontal clinostat.Field emission scanning electron microscopy revealed that the surface texture of epidermal cells,like the direction of the MT,in the EZI and the EZII also became similar when exposed to the simulated microgravity condition.This result indicated that simulate microgravity could modify the potential differentiation between the EZI and the EZII by affecting the orientation of cortical MT in the epidermal cells.展开更多
Microtubule catalyzes the mechanochemical cycle of kinesin,a kind of molecular motor,through its crucial roles in kinesin's gating,ATPase and force-generation process.These functions of microtubule are realized th...Microtubule catalyzes the mechanochemical cycle of kinesin,a kind of molecular motor,through its crucial roles in kinesin's gating,ATPase and force-generation process.These functions of microtubule are realized through the kinesin-microtubule interaction.The binding site of kinesin on the microtubule surface is fixed.For most of the kinesin-family members,the binding site on microtubule is in the groove betweenα-tubulin andβ-tubulin in a protofilament.The mechanism of kinesin searching for the appropriate binding site on microtubule is still unclear.Using the molecular dynamics simulation method,we investigate the interactions between kinesin-1 and the different binding positions on microtubule.The key non-bonded interactions between the motor domain and tubulins in kinesin's different nucleotide-binding states are listed.The differences of the amino-acid sequences betweenα-andβ-tubulins make kinesin-1 binding to theα–βgroove much more favorable than to theβ–αgroove.From these results,a two-step mechanism of kinesin-1 to discriminate the correct binding site on microtubule is proposed.Most of the kinesin-family members have the conserved motor domain and bind to the same site on microtubule,the mechanism may also be shared by other family members of kinesin.展开更多
文摘Microtubules(MTs) are part of the cellular cytoskeleton and they play a role in many activities, such as cell division and maintenance of cell shape. In recent years, MTs have been thought to be involved in storing and processing information.Several models have been developed to describe the information-processing ability of MTs. In these models, MTs are considered as a device that can transmit quantum information. However, MTs are affected by the "wet and warm" cellular environment, thus it is essential to calculate the decoherence time. Many researchers have attempted to calculate this parameter but the values that have been obtained vary markedly. Previous studies considered the cellular environment as a distant ion; however, this treatment is somewhat simplified. In this study, we develop a model to determine the decoherence time in neuronal MTs while considering the interaction effects of the neuronal fluid environment. The neuronal environment is considered as a plasmon reservoir. The coupling between MTs and neuronal environment occurs due to the interaction between dipoles and plasmon. The interaction Hamiltonian is derived by using the second quantization method, and the coupling coefficient is calculated. Finally, the decoherence time scale is estimated according to the interaction Hamiltonian.In this paper, the time scale of decoherence in MTs is approximately 1 fs-100 fs. This model may be used as a reference in other decoherence processes in biological tissues.
基金supported by the Serbian Ministry of Education and Sciences(Grant No.Ⅲ45010)the URF from Periyar University,India+4 种基金the research award of UGCthe major research project of NBHM,Indiathe Young Scientist Research Award of BRNS,Indiathe Junior Associateship of ICTP,Italythe Rajiv Gandhi National Fellowship of UGC
文摘Among many types of proteinaceous filaments, microtubules （MTs） constitute the most rigid components of the cellular cytoskeleton. Microtubule dynamics is essential for many vital cellular processes such as intracellular transport, metabolism, and cell division. We investigate the nonlinear dynamics of inhomogeneous microtubulin systems and the MT dynamics is found to be governed by a perturbed sine-Gordon equation. In the presence of various competing nonlinear inhomogeneities, it is shown that this nonlinear model can lead to the existence of kink and antikink solitons moving along MTs. We demonstrate kink-antikink pair collision in the framework of Hirota＇s bilinearization method. We conjecture that the collisions of the quanta of energy propagating in the form of kinks and antikinks may offer a new view of the mechanism of the retrograde and anterograde transport direction regulation of motor proteins in microtubulin systems.
基金Project supported by Serbian Ministry of Education and Sciences (Grant No.III45010)UGC,NBHM,India (major research projects)+2 种基金BRNS,India (Young Scientist Research Award)ICTP,Italy (Junior Associateship)UGC (Rajiv Gandhi National Fellowship)
文摘We show how Jacobian elliptic functions （JEFs） can be used to solve ordinary differential equations （ODEs） describing the nonlinear dynamics of microtubules （MTs）. We demonstrate that only one of the JEFs can be used while the remaining two do not represent the solutions of the crucial differential equation. We show that a kinkbtype soliton moves along MTs. Besides this solution, we also discuss a few more solutions that may or may not have physical meanings. Finally, we show what kind of ODE can be solved by using JEFs.
文摘The control of dissipation and amplification of solitary waves in an electrical model of a microtubule is demonstrated.This model consists of a shunt nonlinear resistance–capacitance(J(V)–C(V)) circuit and a series resistance–inductance(R–L) circuit. Through linear dispersion analysis, two features of the network are found, that is, low bandpass and bandpass filter characteristics. The effects of the conductance’s parameter λ on the linear dispersion curve are also analyzed. It appears that an increase of λ induces a decrease(an increase) of the width of the bandpass filter for positive(negative) values of λ. By applying the reductive perturbation method, we derive the equation governing the dynamics of the modulated waves in the system. This equation is the well-known nonlinear Schr?dinger equation extended by a linear term proportional to a hybrid parameter σ, i.e., a dissipation or amplification coefficient. Based on this parameter, we successfully demonstrate the hybrid behavior(dissipation and amplification) of the system. The exact and approximate solitary wave solutions of the obtained equation are derived, and the effects of the coefficient σ on the characteristic parameters of these waves are investigated. Using the analytical solutions found, we show numerically that the waves that are propagated throughout the system can be dissipated, amplified, or remain stable depending on the network parameters. These results are not only in agreement with the analytical predictions, but also with the existing experimental results in the literature.
基金supported by National Key Project of China (No. 2001BA302B)
文摘Low-energy ion implantation, as a new technology to produce mutation in plant breeding, has been widely applied in agriculture in China. But so far there is a little understanding of the underlying mechanisms responsible for its biological effects at the cellular level. Here we report the biological effects of a nitrogen ion beams of 30 keV on the pollen grains of Pinus thunbergii Parl. In general, ion implantation inhibited pollen germination. The dose-response curve presented a particular saddle-like pattern. Ion implantation also changed the dimension of the elongated tubes and significantly induced tip swelling. Confocal microscopy indicated that the pollen tube tips in P. thunbergii contained an enriched network of microtubules. Ion implantation led to the disruption of microtubules especially in swollen tips. Treatment with colchicine demonstrated that tip swelling was caused by the disruption of microtubules in the tip, indicating a unique role for microtubules in maintaining the tip integrality of the pollen tube in conifer. Our results suggest that ion implantation induce the disruption of microtubule organization in pollen and pollen tubes and subsequently cause morphological abnormalities in the pollen tubes. This study may provide a clue for further investigation on the interaction between low-energy ion beams and pollen tube growth.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10025420, 10574121 and 90406024, the Ministry of Education of China, and Chinese Academy of Sciences.
文摘A theoretical investigation on the structural and elastic properties of ZnO nanotubes is carried out by using atomistic calculations based on an inter-atomic pair potential within the shell-model approach. The calculation results are presented for the bond length, bond angle, radius dilation, strain energy, Young modulus and Poisson ratio as a function of tube radius. For small tube radius these properties depend on the helicity of the tube, while for the tube radius larger than 6.0A, they are independent of the tube radius and helicity except for the strain energy which decreases with increasing tube radius.
文摘The human rectal adenocarcinoma cell line(HR8348)was treated withlympholdne activated killer(LAK)cells in vitro and the changes of the microtubulin inboth the effector and target cells were investigated with the aid of immunofluorescencemicroscopy.It was revealed that after the attachment of LAK cells to the tumor cells,theeffector-target conjugates formed and distribution of the microtubulin in both the effectorand target cells changed.In the LAK cells,the microtubulin concentrated mainly in thecontact region,forming a crescent-like structure,while in the target cells,themicrotubulin condensed into patches and fused with the crescent-like structure of the LAKcells,Eventually,the target cells degenerated and died.It was suggested that the lysis ofthe target cells may be related to the redistribution of the microtubulin in both theeffector and target cells.
文摘Taxol was used as a tool reagent and the function of the microtubules (MTs) beneath thepostsynaptic membrane was studied in an isolated non-uniformly stretched muscle preparation of ratdiaphragm.After exposure to taxol (20 μmol/L,10min),the amplitude of acetylcholine potential ofinnervated muscle endplate was decreased by 30%,but the lime course of AChP and membrane po-tential remained unchanged.The results indicate that taxol can inhibit the responsiveness ofpostsynapfic membrane.It is therefore suggested that the site of action of taxol indudng inhibitionof postsynapfic responsiveness in neuromuscular junction may be the microtubules beneath thepostsynapfic membrane.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474155,11774147,11674236,and 11922506)。
文摘Microtubule self-organization under mechanical and chemical regulations plays a central role in cytokinesis and cel-lular transportations.In plant-cells,the patterns or phases of cortical microtubules organizations are the direct indicators of cell-phases.The dense nematic pattern of cortical microtubule array relies on the regulation of single microtubule dynamics with mechanical coupling to steric interaction among the self-organized microtubule crowds.Building upon previous mini-mal models,we investigate the effective microtubule width,microtubule catastrophe rate,and zippering angle as factors that regulate the self-organization of the dense nematic phase.We find that by incorporating the effective microtubule width,the transition from isotropic to the highly ordered nematic phase(NI phase)with extremely long microtubules will be gapped by another nematic phase which consists of relative short microtubules(NII phase).The NII phase in the gap grows wider with the increase of the microtubule width.We further illustrate that in the dense phase,the collision-induced catastrophe rate and an optimal zippering angle play an important role in controlling the order-disorder transition,as a result of the coupling between the collision events and ordering.Our study shows that the transition to dense microtubule array requires the cross-talk between single microtubule growth and mechanical interactions among microtubules in the active crowds.
基金Supported by the China Manned Space Flight Technology Project TG-2the National Natural Science Foundation of China(31670864)+2 种基金the National Natural Fund Joint Fund Project(U1738106)the Strategic Pioneer Projects of CAS(XDA15013900)the National Science Foundation for Young Scientists of China(31500687)
文摘Gravitropic curvature growth of Arabidopsis hypocotyls mainly occurred in the rapid growing Elongation Zone(EZI),not in the slow-growing Elongation Zone(EZII).By examining reorientation of Microtubules(MT)and phenotype of the cell wall in the EZI and the EZII of Arabidopsis hypocotyls under normal gravitational condition,it is found that MTs in the rapid growing epidermal cells were mainly in the transverse direction,while those in the non-growing epidermal cells were in the longitudinal directions.However,this difference in cortical MT arrays between the EZI and EZII cells disappeared when the seedlings were exposed to the simulated microgravity condition on a horizontal clinostat.Field emission scanning electron microscopy revealed that the surface texture of epidermal cells,like the direction of the MT,in the EZI and the EZII also became similar when exposed to the simulated microgravity condition.This result indicated that simulate microgravity could modify the potential differentiation between the EZI and the EZII by affecting the orientation of cortical MT in the epidermal cells.
基金supported by the Natural Science Foundation of Hebei Province of China(Grant No.A2020202007)the National Natural Science Foundation of China(Grant No.11605038)。
文摘Microtubule catalyzes the mechanochemical cycle of kinesin,a kind of molecular motor,through its crucial roles in kinesin's gating,ATPase and force-generation process.These functions of microtubule are realized through the kinesin-microtubule interaction.The binding site of kinesin on the microtubule surface is fixed.For most of the kinesin-family members,the binding site on microtubule is in the groove betweenα-tubulin andβ-tubulin in a protofilament.The mechanism of kinesin searching for the appropriate binding site on microtubule is still unclear.Using the molecular dynamics simulation method,we investigate the interactions between kinesin-1 and the different binding positions on microtubule.The key non-bonded interactions between the motor domain and tubulins in kinesin's different nucleotide-binding states are listed.The differences of the amino-acid sequences betweenα-andβ-tubulins make kinesin-1 binding to theα–βgroove much more favorable than to theβ–αgroove.From these results,a two-step mechanism of kinesin-1 to discriminate the correct binding site on microtubule is proposed.Most of the kinesin-family members have the conserved motor domain and bind to the same site on microtubule,the mechanism may also be shared by other family members of kinesin.
