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Buckling of filamentous actin bundles in filopodial protrusion

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Acta Mechanica Sinica 2019年第2期35卷 365-375页

作者： Yanzhong Wang jin qian Department of Engineering Mechanics Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Zhejiang University Hangzhou Zhejiang 310027 China

The mechanical behaviors of filamentous actin (F-actin) bundles play an essential role in filopodial protrusions at the leading edge of crawling cells. These bundles consist of parallel actin filaments that are hexagonally packed and interconnected via cross-linking proteins including α-actinin, filamin, and fascin. As pushing against the plasma membrane and/or external barriers, the actin bundles in filopodial protrusion inevitably encounter a compressive load. The bending stiffness and buckling stability of actin bundles are therefore important in determining the filopodia architecture and subsequent cell morphology. In this work, we employ a coarse-grained molecular dynamics model to investigate the buckling behaviors of cross-linked actin bundles under compression, which explicitly accounts for the properties of constituent filaments and the mechanical descriptions of cross-linkers. The bending stiffness of actin bundles exhibits a generic size effect depending on the number of filaments in the bundles, explicitly depending on the degree of inter-filament coupling. The distinct buckling modes are analyzed for bundles with different coupling states and strengths of cross-linkers. This study could clarify the stability and buckling mechanisms of parallelly packed actin bundles and the structure-function relations of mechanical components in filopodial protrusion.

关键词： Filopodial protrusion Actin bundle Molecular dynamics Buckling Size effect Cross-linking protein

Effects of domain unfolding and catch-like dissociation on the collective behavior of integrin-fibronectin bond clusters

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Acta Mechanica Sinica 2021年第2期37卷 229-243页

作者： Ji Lin Yanzhong Wang jin qian Department of Engineering Mechanics Key Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceZhejiang UniversityHangzhou 310027China

To gain more understanding of cell-matrix adhesion,we consider an idealized theoretical model of a cluster of integrin-fibronectin bonds at the cell-matrix interface subjected to a dynamic *** distributions of bond traction and interfacial deformation are assumed to obey classical elastic equations,whereas the dissociation/association of individual bonds as well as unfolding/refolding of fibronectin domains are described by stochastic *** stochastic-elasticity coupling,we perform Monte Carlo simulations to investigate how the collective behavior and adhesion performance of the integrin-fibronectin-mediated interface are influenced by two characteristics newly incorporated in the modeling,i.e.,catchlike dissociation between integrin and fibronectin,and unfolding of repeated domains in *** probable unfolding of fibronectin domains is found to have profound effects on the resultant adhesion energy of the integrin-fibronectin-mediated interface,and governs the failure model transiting between uniform decay and catastrophic crack-like rupture.

关键词： Integrin-fibronectin complex Cell-matrix adhesion Domain unfolding Catch bond Rate dependence Modulus effect

BLOCK BASED NEWTON-LIKE BLENDING INTERPOLATION

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Journal of Computational Mathematics 2006年第4期24卷 515-526页

作者： qian-jin Zhao Jie-qing Tan School of Computer and Information Hefei University of Technology Hefei 230009 China Department of Mathematics and Physics Anhui University of Science and Technology Huainan 232001 China Institute of Applied Mathematics Hefei University of Technology Hefei 230009 China

Newton＇s polynomial interpolation may be the favourite linear interpolation in the sense that it is built up by means of the divided differences which can be calculated recursively and produce useful intermediate results. However Newton interpolation is in fact point based interpolation since a new interpolating polynomial with one more degree is obtained by adding a new support point into the current set of support points once at a time. In this paper we extend the point based interpolation to the block based interpolation. Inspired by the idea of the modern architectural design, we first divide the original set of support points into some subsets （blocks）, then construct each block by using whatever interpolation means, linear or rational and finally assemble these blocks by Newton＇s method to shape the whole interpolation scheme. Clearly our method offers many flexible interpolation schemes for choices which include the classical Newton＇s polynomial interpolation as its special case. A bivariate analogy is also discussed and numerical examples are given to show the effectiveness of our method.

关键词： Interpolation Block based divided differences Blending method.

Growing actin networks regulated by obstacle size and shape

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Acta Mechanica Sinica 2017年第2期33卷 222-233页

作者： Bo Gong Ji Lin jin qian Department of Engineering Mechanics Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Zhejiang University Hangzhou 310027 China

Growing actin networks provide the driving force for the motility of cells and intracellular pathogens. Based on the molecular-level processes of actin polymerization, branching, capping, and depolymerization, we have developed a modeling framework to simulate the stochastic and cooperative behaviors of growing actin networks in propelling obstacles, with an emphasis on the size and shape effects on work capacity and filament orientation in the growing process. Our results show that the characteristic size of obstacles changes the protrusion power per unit length, without influencing the orientation distribution of actin filaments in growing networks. In contrast, the geometry of obstacles has a profound effect on filament patterning, which influences the orientation of filaments differently when the drag coefficient of environment is small, intermediate, or large. We also discuss the role of various parameters, such as the aspect ratio of obstacles, branching rate, and capping rate, in affecting the protrusion power of network growth.

关键词： Actin network Growth dynamics Monte Carlo simulation Size effect Shape effect

Risk assessment of water security in Haihe River Basin during drought periods based on D-S evidence theory

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Water Science and Engineering 2014年第2期7卷 119-132页

作者： qian-jin DONG Xia LIU State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University Hubei Provincial Collaborative Innovation Center for Water Resources Security Wuhan University School of Geography and Planning Sun Yat-sen University

The weights of the drought risk index （DRI）, which linearly combines the reliability, resiliency, and vulnerability, are difficult to obtain due to complexities in water security during drought periods. Therefore, drought entropy was used to determine the weights of the three critical indices. Conventional simulation results regarding the risk load of water security during drought periods were often regarded as precise. However, neither the simulation process nor the DRI gives any consideration to uncertainties in drought events. Therefore, the Dempster-Shafer （D-S） evidence theory and the evidential reasoning algorithm were introduced, and the DRI values were calculated with consideration of uncertainties of the three indices. The drought entropy and evidential reasoning algorithm were used in a case study of the Haihe River Basin to assess water security risks during drought periods. The results of the new DRI values in two scenarios were compared and analyzed. It is shown that the values of the DRI in the D-S evidence algorithm increase slightly from the original results of Zhang et al. （2005）, and the results of risk assessment of water security during drought periods are reasonable according to the situation in the study area. This study can serve as a reference for further practical application and planning in the Haihe River Basin, and other relevant or similar studies.

关键词： risk assessment " water security " drought periods " entropy " D-S evidence theory "evidential reasoning algorithm " Haihe River Basin

Phase Diagram of the 2-Dimensional Ising Model with Dipolar Interaction

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Chinese Physics Letters 2001年第4期18卷 491-494页

作者： SUN Gang CHU qian-jin Institute of Physics Chinese Academy of SciencesBeijing 100080

We treat the 2-dimensional Ising model with the dipolar interaction by the numerical calculation under the restriction that the spin configurations are distributed with a 4 × 4 *** phase diagram with respect to temperature and dipolar interaction strength is *** characters of the phase diagram are consistent with those obtained in the references by the Monte Carlo simulation,except that we find a new rectangle phase,which is ordered in the spin structure with the 1 × 2 rectangle.

关键词： strength diagram phase

Preface to the Special Issue on the Dynamic Behaviors and Energy Absorption of Materials and Structures

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Acta Mechanica Solida Sinica 2021年第6期34卷 781-782页

作者： jin qian Ronghao Bao Weiqiu Chen Department of Engineering Mechanics Key Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceZhejiang UniversityHangzhou 310027China

In this themed issue of Acta Mechanica Solida Sinica(AMSS),leading experts and researchers are joining together to celebrate Professor Tongxi Yu’s 80th birthday and pay tribute to his distinguished career spanning over five decades,devoted to pioneering research in the fields of impact dynamics,plasticity,energy absorption,textile and cellular materials,nano-composites,*** Yu has been a much-admired teacher,a mentor and a friend to all who worked with him throughout his career,and this collection of articles is contributed by people who have had association with Professor Yu as colleagues,students,postdocs or collaborators.

关键词： devoted career Absorption

Physics problems in bio or bioinspired additive manufacturing

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Bio-Design and Manufacturing 2023年第2期6卷 99-102页

作者： Jun Yin jin qian Yong Huang The State Key Laboratory of Fluid Power and Mechatronic Systems School of Mechanical EngineeringZhejiang UniversityHangzhou 310028China Key Laboratory of 3D Printing Process and Equipment of Zhejiang Province School of Mechanical EngineeringZhejiang UniversityHangzhou 310028China Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Department of Engineering MechanicsZhejiang UniversityHangzhou 310027China Department of Mechanical and Aerospace Engineering University of FloridaGainesvilleFL 32611USA

Additive manufacturing,also known as three-dimensional(3D)printing,has attracted increasing attention due to the innovations in materials science and manufacturing over recent decades[1].Recently,innovations in biocompatible materials and biology have enabled the extension of 3D printing techniques into bioadditive manufacturing,which focuses on the fabrication of 3D engineered native-like tissues/organs[2].Currently,bioadditive manufacturing technologies can be categorized into inkjet-based bioprinting,microextrusion-based bioprinting,digital light processing(DLP)bioprinting,electric field-assisted bioprinting,and fused deposition modeling(FDM),to name a few[3,4](Fig.1).Artificial tissues and organs with delicate structures,such as the heart[5]and liver[6],have been successfully fabricated using various bioadditive manufacturing techniques.

关键词： printing additive organs

Glucagon-like peptide-1/glucose-dependent insulinotropic polypeptide dual receptor agonist DA-CH5 is superior to exendin-4 in protecting neurons in the 6-hydroxydopamine rat Parkinson model

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Neural Regeneration Research 2021年第8期16卷 1660-1670页

作者： Ling-Yu Zhang qian-qian jin Christian Hölscher Lin Li Gerontology Institute Shanxi Medical UniversityTaiyuanShanxi ProvinceChina Department of Forensic Pathology Shanxi Medical UniversityTaiyuanShanxi ProvinceChina Department of Neurology Second HospitalShanxi Medical UniversityTaiyuanShanxi ProvinceChina Research and Experimental Center Henan University of Chinese MedicineZhengzhouHenan ProvinceChina

Patients with Parkinson's disease(PD) have impaired insulin signaling in the brain. Incretin hormones, including glucagon-like peptide-1(GLP-1) and glucose-dependent insulinotropic polypeptide(GIP), can re-sensitize insulin signaling. In a recent phase II clinical trial, the first GLP-1 mimic, exendin-4, has shown reliable curative effect in patients with PD. DA-CH5 is a novel GLP-1/GIP receptor unimolecular coagonist with a novel peptide sequence added to cross the blood-brain barrier. Here we showed that both exendin-4 and DA-CH5 protected against 6-hydroxydopamine(6-OHDA) cytotoxicity, inhibited apoptosis, improved mitogenesis and induced autophagy flux in SH-SY5Y cells via activation of the insulin receptor substrate-1(IRS-1)/alpha serine/threonine-protein kinase(Akt)/c AMP response element-binding protein(CREB) pathway. We also found that DA-CH5(10 nmol/kg) daily intraperitoneal administration for 30 days post-lesion alleviated motor dysfunction in rats and prevented stereotactic unilateral administration of 6-OHDA induced dopaminergic neurons loss in the substantia nigra pars compacta. However, DA-CH5 showed curative effects in reducing the levels of α-synuclein and the levels of pro-inflammatory cytokines(tumor necrosis factor-α, interleukin-1β). It was also more effective than exendin-4 in inhibiting apoptotic process and protecting mitochondrial functions. In addition, insulin resistance was largely alleviated and the expression of autophagy-related proteins was upregulated in PD model rats after DA-CH5 treatment. These results in this study indicate DA-CH5 plays a therapeutic role in the 6-OHDAunilaterally lesioned PD rat model and is superior to GLP-1 analogue exendin-4. The study was approved by the Animal Ethics Committee of Shanxi Medical University of China.

关键词： neurodegenerative disease Parkinson's disease insulin resistance inflammation GLP-1/GIP receptor unimolecular co-agonist