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Effective and efficient modeling of the hydrodynamics for bacterial flagella 细菌鞭毛流体力学的高效建模
Pub Date : 2024-08-12 DOI: arxiv-2408.06093
Baopi Liu, Lu Chen, Ji Zhang, Xinliang Xu
The hydrodynamic interactions between bacterial flagella and surroundingboundaries are important for bacterial motility and gait in complexenvironment. By modeling each flagellar filament that is both thin and long asa string of spheres, we show that such hydrodynamic interactions can beaccurately described through a resistance tensor, which can be efficientlyevaluated numerically. For the case of close interaction between one bacteriumand one passive colloidal sphere, we see notable difference between resultsfrom our model and those from the resistive force theory, showing that theerror arises from negligence of the width of flagellar filaments in resistiveforce theory can be strong.
细菌鞭毛与周围边界之间的流体动力学相互作用对细菌在复杂环境中的运动和步态非常重要。通过将每根既细又长的鞭毛细丝建模为一串球体,我们证明这种流体动力学相互作用可以通过阻力张量准确描述,并可以有效地进行数值评估。对于一个细菌和一个被动胶体球之间的密切相互作用,我们发现我们的模型和阻力理论的结果之间存在显著差异,这表明阻力理论中由于忽略鞭毛细丝的宽度而产生的误差可能很大。
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引用次数: 0
Modeling collagen fibril degradation as a function of matrix microarchitecture 作为基质微结构函数的胶原纤维降解建模
Pub Date : 2024-08-11 DOI: arxiv-2408.05693
B. Debnath, B. N. Narasimhan, S. I. Fraley, P. Rangamani
Collagenolytic degradation is a process fundamental to tissue remodeling. Themicroarchitecture of collagen fibril networks changes during development,aging, and disease. Such changes to microarchitecture are often accompanied bychanges in matrix degradability. In vitro, collagen matrices of the sameconcentration but different microarchitectures also vary in degradation rate.How do different microarchitectures affect matrix degradation? To answer thisquestion, we developed a computational model of collagen degradation. We firstdeveloped a lattice model that describes collagen degradation at the scale of asingle fibril. We then extended this model to investigate the role ofmicroarchitecture using Brownian dynamics simulation of enzymes in amulti-fibril three dimensional matrix to predict its degradability. Oursimulations predict that the distribution of enzymes around the fibrils isnon-uniform and depends on the microarchitecture of the matrix. Thisnon-uniformity in enzyme distribution can lead to different extents ofdegradability for matrices of different microarchitectures. Our modelpredictions were tested using in vitro experiments with synthesized collagengels of different microarchitectures. Experiments showed that indeeddegradation of collagen depends on the matrix architecture and fibrilthickness. In summary, our study shows that the microarchitecture of thecollagen matrix is an important determinant of its degradability.
胶原蛋白溶解降解是组织重塑的基本过程。胶原纤维网络的微观结构在发育、衰老和疾病过程中会发生变化。这种微观结构的变化往往伴随着基质降解性的变化。在体外,浓度相同但微体系结构不同的胶原蛋白基质的降解率也不同。为了回答这个问题,我们开发了胶原降解的计算模型。我们首先开发了一个晶格模型,该模型描述了单纤维尺度上的胶原降解。然后,我们扩展了这一模型,利用布朗动力学模拟酶在多纤维三维基质中的作用来研究微结构的作用,从而预测其降解性。我们的模拟预测,酶在纤维周围的分布并不均匀,而是取决于基质的微观结构。酶分布的这种不均匀性会导致不同微结构的基质具有不同程度的降解性。我们使用不同微观结构的合成胶凝胶进行了体外实验,检验了我们的模型预测。实验表明,胶原蛋白的降解确实取决于基质结构和纤维厚度。总之,我们的研究表明,胶原蛋白基质的微观结构是决定其降解性的重要因素。
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引用次数: 0
Dynamic cluster field modeling of collective chemotaxis 集体趋化的动态簇场模型
Pub Date : 2024-08-08 DOI: arxiv-2408.04748
Aditya Paspunurwar, Adrian Moure, Hector Gomez
Collective migration of eukaryotic cells is often guided by chemotaxis, andis critical in several biological processes, such as cancer metastasis, woundhealing, and embryogenesis. Understanding collective chemotaxis has challengedexperimental, theoretical and computational scientists because cells can sensevery small chemoattractant gradients that are tightly controlled by cell-cellinteractions and the regulation of the chemoattractant distribution by thecells. Computational models of collective cell migration that offer ahigh-fidelity resolution of the cell motion and chemoattractant dynamics in theextracellular space have been limited to a small number of cells. Here, wepresent Dynamic cluster field modeling (DCF), a novel computational method thatenables simulations of collective chemotaxis of cellular systems with O(1000)cells and high-resolution transport dynamics of the chemoattractant in thetime-evolving extracellular space. We illustrate the efficiency and predictivecapabilities of our approach by comparing our numerical simulations withexperiments in multiple scenarios that involve chemoattractant secretion anduptake by the migrating cells, regulation of the attractant distribution bycell motion, and interactions of the chemoattractant with an enzyme. Theproposed algorithm opens new opportunities to address outstanding problems thatinvolve collective cell migration in the central nervous system, immuneresponse and cancer metastasis.
真核细胞的集体迁移通常由趋化作用引导,在癌症转移、伤口愈合和胚胎发育等多个生物过程中至关重要。由于细胞能感知非常微小的趋化梯度,而这种梯度受细胞-细胞相互作用和细胞对趋化物质分布的调节的严格控制,因此理解集体趋化现象对实验、理论和计算科学家提出了挑战。细胞集体迁移的计算模型能高保真地解析细胞运动和细胞外空间的趋化因子动态,但这种模型仅限于少数细胞。在这里,我们将介绍动态簇场建模(Dynamic cluster field modeling,DCF),这是一种新颖的计算方法,可以模拟细胞数为 O(1000)个的细胞系统的集体趋化以及趋化物质在随时间演变的细胞外空间的高分辨率迁移动力学。我们通过将数值模拟与多种情况下的实验进行比较,包括迁移细胞分泌和吸收趋化吸引剂、细胞运动对吸引剂分布的调节以及趋化吸引剂与酶的相互作用,说明了我们的方法的效率和预测能力。提出的算法为解决涉及中枢神经系统细胞集体迁移、免疫反应和癌症转移等悬而未决的问题提供了新的机遇。
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引用次数: 0
Molecular dynamics characterization of the free and encapsidated RNA2 of CCMV with the oxRNA model 利用 oxRNA 模型对 CCMV 的游离和包封 RNA2 进行分子动力学表征
Pub Date : 2024-08-07 DOI: arxiv-2408.03662
Giovanni Mattiotti, Manuel Micheloni, Lorenzo Petrolli, Luca Tubiana, Samuela Pasquali, Raffaello Potestio
The cowpea chlorotic mottle virus (CCMV) has emerged as an exemplary modelsystem to assess the balance between electrostatic and topological features ofssRNA viruses, specifically in the context of the viral self-assembly process.Yet, in spite of its biophysical significance, little structural data of theRNA content of the CCMV virion is currently available. Here, the conformationaldynamics of the RNA2 fragment of CCMV was assessed via coarse-grained moleculardynamics simulations, employing the oxRNA2 model. The behavior of RNA2 has beencharacterized both as a freely-folding molecule and within a mean-fielddepiction of a CCMV-like capsid. For the latter, a multi-scale approach wasemployed, to derive a radial potential profile of the viral cavity, fromatomistic structures of the CCMV capsid in solution. The conformationalensembles of the encapsidated RNA2 were significantly altered with respect tothe freely-folding counterparts, as shown by the emergence of long-range motifsand pseudoknots in the former case. Finally, the role of the N-terminal tailsof the CCMV subunits (and ionic shells thereof) is highlighted as a criticalfeature in the construction of a proper electrostatic model of the CCMV capsid.
豇豆萎黄斑驳病病毒(CCMV)已成为评估 CSSRNA 病毒静电和拓扑特征之间平衡的典范模型系统,特别是在病毒自组装过程中。然而,尽管其具有重要的生物物理意义,目前却鲜有关于 CCMV 病毒 RNA 内容的结构数据。本文采用 oxRNA2 模型,通过粗粒度分子动力学模拟评估了 CCMV 的 RNA2 片段的构象动力学。RNA2 作为自由折叠分子和在类似于 CCMV 的囊膜的平均场预测中的行为都得到了描述。对于后者,采用了一种多尺度方法,从溶液中 CCMV 荚膜的解剖结构中推导出病毒腔的径向电位曲线。与自由折叠的对应物相比,包被的 RNA2 的构象组合发生了显著变化,这表现在前者出现了长程图案和假结点。最后,CCMV 亚基 N 端尾部(及其离子壳)的作用被强调为构建 CCMV 荚膜适当静电模型的关键特征。
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引用次数: 0
A ubiquitous transfer function links interacting elements to emerging property of complex systems 无处不在的传递函数将相互作用的元素与复杂系统的新特性联系起来
Pub Date : 2024-08-05 DOI: arxiv-2408.03347
Lina Yan, Jeffrey Huy Khong, Aleksandar Kostadinov, Jerry Ying Hsi Fuh, Chih-Ming Ho
In the field of complex systems, self-organization magnifies the compoundingeffects of element interactions by propagating, modifying, and enhancingfunctionality, ultimately leading to emergent system properties. Theintricacies of self-organization make unveiling the elusive link betweenelement interactions and emergent system properties akin to finding theproverbial Holy Grail. In the search for identifying a method to predictsystem-level properties, we used an inductive approach to bypass theself-organization. By observing drug interactions within biological complexsystem, system property, efficacy, emerged as a smooth response surface in themulti-dimensional space of drug-system interactions, which can be representedby the Complex System Response (CSR) function. This CSR function has beensuccessfully validated across diverse disease models in cell lines, animals,and clinical trials. Notably, the CSR function reveals that biological complexsystems exhibit second-order non-linearity. In this study, we generalized theCSR function to physical complex systems, linking maximum compressive yieldingstress to impactful manufacturing parameters of the Selective Laser Melting(SLM) process. Remarkably though anticipated, the CSR function reveals theconnection between the macroscale system property (compressive yielding stress)and the microstructure during self-organizing process. In addition, thesecond-order non-linear CSR functions ensure a single global optimum in complexsystems.
在复杂系统领域,自组织通过传播、修改和增强功能,放大了元素相互作用的复合效应,最终导致了系统的突发特性。自组织的复杂性使得揭示元素相互作用与新兴系统特性之间难以捉摸的联系无异于寻找传说中的圣杯。在寻找预测系统级特性方法的过程中,我们采用了绕过自组织的归纳法。通过观察药物在生物复杂系统中的相互作用,系统属性--药效--在药物-系统相互作用的多维空间中形成了一个平滑的响应面,可以用复杂系统响应(CSR)函数来表示。该CSR函数已在细胞系、动物和临床试验的各种疾病模型中得到成功验证。值得注意的是,CSR 函数揭示了生物复杂系统表现出的二阶非线性。在本研究中,我们将 CSR 函数推广到物理复杂系统,将最大压缩屈服应力与选择性激光熔融(SLM)工艺的影响性制造参数联系起来。令人惊讶的是,CSR 函数揭示了自组织过程中系统宏观属性(压缩屈服应力)与微观结构之间的联系。此外,这些二阶非线性 CSR 函数确保了复杂系统中的单一全局最优。
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引用次数: 0
Intermittent Run Motility of Bacteria in Gels Exhibits Power-Law Distributed Dwell Times 凝胶中细菌的间歇运行运动呈现幂律分布的停留时间
Pub Date : 2024-08-05 DOI: arxiv-2408.02317
Agniva Datta, Sönke Beier, Veronika Pfeifer, Robert Großmann, Carsten Beta
While bacterial swimming has been well characterized in uniform liquidenvironments, only little is known about how bacteria propagate through complexenvironments, such as gel-like matrices or porous media that are typicallyencountered in tissue or soil. Here, we study swimming motility of the soilbacterium Pseudomonas putida (P. putida) in polysaccharide matrices formed bydifferent concentrations of agar. P. putida cells display intermittentrun-motility in the gel, where run times are exponentially distributed andintermittently occurring dwell times follow a waiting-time distribution with apower-law decay. An analysis of the turn angle distribution suggests that both,flagella mediated turning as well as mechanical trapping in the agar matrixplay a role in the overall swimming pattern. Based on the experimentallyobserved motility pattern and measured waiting-time distributions, we propose aminimal active particle model which correctly describes the observed timedependence of the mean square displacement of the bacterial swimmers.
细菌在均匀液体环境中的游动特性已经得到了很好的描述,但对于细菌如何在复杂环境中传播却知之甚少,例如在组织或土壤中通常会遇到的凝胶状基质或多孔介质。在这里,我们研究了土壤假单胞菌(P. putida)在不同浓度琼脂形成的多糖基质中的游动性。普氏假单胞菌细胞在凝胶中显示出间歇性的游动特性,其中游动时间呈指数分布,而间歇性出现的停留时间遵循幂律衰减的等待时间分布。对转角分布的分析表明,在整个游动模式中,鞭毛介导的转角和琼脂基质中的机械捕获都发挥了作用。根据实验观察到的运动模式和测量到的等待时间分布,我们提出了一个最小活性粒子模型,该模型正确地描述了观察到的细菌游动平均平方位移的时间依赖性。
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引用次数: 0
Spontaneous and Induced Oscillations in Confined Epithelia 封闭上皮细胞的自发振荡和诱导振荡
Pub Date : 2024-08-05 DOI: arxiv-2408.02806
Toshi Parmar, Liam P. Dow, beth L. Pruitt, M. Cristina Marchetti
The feedback between mechanical and chemical signals plays a key role incontrolling many biological processes and collective cell behavior. Here wefocus on the emergence of spatiotemporal density waves in a one-dimensional"cell train." Combining a minimal theoretical model with observations in an invitro experimental system of MDCK epithelial cells confined to a linearpattern, we examine the spontaneous oscillations driven by the feedback betweenmyosin activation and mechanical deformations and their effect on the responseof the tissue to externally applied deformations. We show that the nature andfrequency of spontaneous oscillations is controlled by the size of the celltrain, with a transition from size-dependent standing waves to intrinsicspontaneous waves at the natural frequency of the tissue. The response toexternal boundary perturbations exhibit a resonance at this natural frequency,providing a possible venue for inferring the mechanochemical couplings thatcontrol the tissue behavior from rheological experiments.
机械信号和化学信号之间的反馈在控制许多生物过程和细胞集体行为中起着关键作用。在这里,我们重点研究一维 "细胞列车 "中出现的时空密度波。我们将最小理论模型与限制在线性模式中的 MDCK 上皮细胞体外实验系统中的观察结果相结合,研究了肌球蛋白激活与机械变形之间的反馈所驱动的自发振荡及其对组织对外部施加的变形所产生的影响。我们的研究表明,自发振荡的性质和频率受细胞系大小的控制,在组织的固有频率处会从依赖于大小的驻波过渡到固有的自发波。对外部边界扰动的响应在该固有频率处表现出共振,这为从流变学实验中推断控制组织行为的机械化学耦合提供了可能。
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引用次数: 0
Effect of interleaflet friction on the dynamics of molecular rotors in lipid membranes 小叶间摩擦对脂质膜中分子转子动力学的影响
Pub Date : 2024-08-02 DOI: arxiv-2408.01280
Naomi Oppenheimer, Vinny C. Suja, Howard A. Stone
Molecular rotors form twisted conformations upon photoexcitation, with theirfluorescent relaxation time serving as a measure of viscosity. They have beenused to assess membrane viscosities but yield higher values compared to othermethods. Here, we show that the rotor's relaxation time is influenced by acombination of membrane viscosity and interleaflet friction. We present atheory for the relaxation time and obtain a correction factor that accounts forthe discrepancy. If the membrane's viscosity is known, molecular rotors mayenable the extraction of the elusive interleaflet friction.
分子转子在光激发下形成扭曲构象,其荧光弛豫时间可作为粘度的测量值。分子转子已被用于评估膜的粘度,但与其他方法相比,分子转子产生的粘度值更高。在这里,我们表明转子的弛豫时间受到膜粘度和小叶间摩擦力的共同影响。我们提出了弛豫时间的理论,并得到了一个校正因子,以解释差异。如果知道膜的粘度,分子转子就可以提取难以捉摸的叶间摩擦。
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引用次数: 0
Extreme-value analysis in nano-biological systems: Applications and Implications 纳米生物系统中的极值分析:应用与影响
Pub Date : 2024-08-02 DOI: arxiv-2408.01007
Kumiko Hayashi, Nobumichi Takamatsu, Shunki Takaramoto
Extreme value analysis (EVA) is a statistical method that studies theproperties of extreme values of datasets, crucial for fields like engineering,meteorology, finance, insurance, and environmental science. EVA models extremeevents using distributions such as Fr'echet, Weibull, or Gumbel, aiding inrisk prediction and management. This review explores EVA's application tonanoscale biosystems. Traditionally, biological research focuses on averagevalues from repeated experiments. However, EVA offers insights into molecularmechanisms by examining extreme data points. We introduce EVA's concepts withsimulations and review its use in studying motor protein movements withincells, highlighting the importance of in vivo analysis due to the complexintracellular environment. We suggest EVA as a tool for extracting motorproteins' physical properties in vivo and discuss its potential in otherbiological systems. While EVA's use in nanoscale biological systems is limited,it holds promise for uncovering hidden properties in extreme data, promotingits broader application in life sciences.
极值分析(EVA)是一种研究数据集极值特性的统计方法,对工程、气象、金融、保险和环境科学等领域至关重要。EVA 使用 Fr'echet 、Weibull 或 Gumbel 等分布对极端事件进行建模,有助于风险预测和管理。这篇综述探讨了 EVA 在小尺度生物系统中的应用。传统上,生物研究侧重于重复实验的平均值。然而,EVA 可通过研究极端数据点深入了解分子机制。我们通过模拟介绍了 EVA 的概念,并回顾了它在研究细胞内运动蛋白运动中的应用,强调了由于细胞内环境复杂而进行活体分析的重要性。我们建议将 EVA 作为提取体内运动蛋白物理特性的工具,并讨论了它在其他生物系统中的应用潜力。虽然 EVA 在纳米级生物系统中的应用有限,但它有望揭示极端数据中隐藏的特性,从而促进其在生命科学领域的更广泛应用。
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引用次数: 0
Propagation of Enzyme-driven Active Fluctuations in Crowded Milieu 拥挤环境中酶驱动活性波动的传播
Pub Date : 2024-08-01 DOI: arxiv-2408.00578
Rik Chakraborty, Arnab Maiti, Diptangshu Paul, Rajnandan Borthakur, K. R. Jayaprakash, Uddipta Ghosh, Krishna Kanti Dey
We investigated the energy transfer from active enzymes to their surroundingsin crowded environments by measuring the diffusion of passive microscopictracers in active solutions of ficoll and glycerol. Despite observing lowerrates of substrate turnover and relatively smaller enhancement of passivetracer diffusion in artificial crowded media compared to those in aqueoussolutions, we found a significantly higher relative diffusion enhancement incrowded environments in the presence of enzymatic activity. Our experimentalobservations, coupled with supporting analytical estimations, underscored thecritical role of the intervening media in facilitating mechanical energydistribution around active enzymes.
我们通过测量被动微观示踪剂在ficoll和甘油的活性溶液中的扩散,研究了活性酶在拥挤环境中向周围环境的能量转移。尽管与水溶液相比,在人工拥挤介质中观察到的底物周转率较低,被动示踪剂的扩散增强相对较小,但我们发现在有酶活性的拥挤环境中,相对扩散增强明显较高。我们的实验观察结果与支持性分析估计结果相结合,强调了介入介质在促进活性酶周围机械能分布方面的关键作用。
{"title":"Propagation of Enzyme-driven Active Fluctuations in Crowded Milieu","authors":"Rik Chakraborty, Arnab Maiti, Diptangshu Paul, Rajnandan Borthakur, K. R. Jayaprakash, Uddipta Ghosh, Krishna Kanti Dey","doi":"arxiv-2408.00578","DOIUrl":"https://doi.org/arxiv-2408.00578","url":null,"abstract":"We investigated the energy transfer from active enzymes to their surroundings\u0000in crowded environments by measuring the diffusion of passive microscopic\u0000tracers in active solutions of ficoll and glycerol. Despite observing lower\u0000rates of substrate turnover and relatively smaller enhancement of passive\u0000tracer diffusion in artificial crowded media compared to those in aqueous\u0000solutions, we found a significantly higher relative diffusion enhancement in\u0000crowded environments in the presence of enzymatic activity. Our experimental\u0000observations, coupled with supporting analytical estimations, underscored the\u0000critical role of the intervening media in facilitating mechanical energy\u0000distribution around active enzymes.","PeriodicalId":501040,"journal":{"name":"arXiv - PHYS - Biological Physics","volume":"364 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141882372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
期刊
arXiv - PHYS - Biological Physics
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