溯经典之源，探交叉之本。与我们共赴物理生物学经典读书会（Physical Biology Journal Club），回到伟大思想诞生的现场！
Topic:
Stochastic Mechanics of Actin Polymerization: From Brownian Ratchet Theory to Single-Filament Force Measurements
Speaker: Dr. Hanqing Guo (郭瀚卿), Westlake University
Reference:
[1] Qian, Hong. A Stochastic Analysis of a Brownian Ratchet Model for Actin-Based Motility. Molecular & Cellular Biomechanics, vol. 1, no. 4, 2004, pp. 267-78.
[2] Footer, Matthew J., et al. Direct Measurement of Force Generation by Actin Filament Polymerization Using an Optical Trap. Proceedings of the National Academy of Sciences, vol. 104, no. 7, 2007, pp. 2181-86.
Key Words: Brownian ratchet, Actin polymerization, Mean-square displacement, Optical trap, Stall force, Single-molecule biophysics
Time: 16:00-17:30, Thursday, April 9 & 16, 2026
Venue: E14-326, Research Center, Westlake University
Abstract:
Actin polymerization drives cellular protrusion through a Brownian ratchet mechanism, yet a quantitative understanding requires both rigorous stochastic theory and direct force measurements. Qian (2004) developed a stochastic analytical framework for the polymerization ratchet, deriving exact expressions for mean-square displacement and effective diffusion constants that characterize actin-based stepping dynamics. Footer et al. (2007) directly tested the physical predictions of such ratchet models using optical tweezers, measuring piconewton-scale stall forces and revealing that small parallel bundles exhibit “dynamic stall”—where filaments act independently rather than cooperatively due to length fluctuations. Together, these studies illustrate the convergence of stochastic modeling and single-molecule experimentation in quantifying the force-velocity relationship and mechanochemical coupling of actin-based motility.
读书会简介：物理生物学读书会由西湖大学交叉科学中心（CIS）师生共同发起，每周四在轻松自由的氛围中，深入研读物理生物学领域的经典文献，通过追本溯源，激发思想碰撞，促进跨学科交流与合作。
发起人：钱紘，徐小婵
主讲人：以博士后和博士生为核心，全员开放！我们热忱欢迎每一位希望分享的主讲人。
参与成员：欢迎全校所有对物理生物学等交叉领域有浓厚兴趣的师生加入。
地点：科研中心 E14-326 会议室
形式：读书会每周聚焦物理生物学领域的一篇经典论文或书籍章节，通过主讲人领读与集体讨论，理解相关领域的核心概念、理论与模型，系统梳理该领域的基础知识、核心问题与研究范式。
Overview: The Physical Biology Journal Club is a weekly Friday lunchtime event hosted by the faculty and students of the Center for Interdisciplinary Studies (CIS). Our goal is to help everyone learn about how key concepts and groundbreaking discoveries have shaped and inspired the entire research fields. Through lively, in-depth discussion of classic physical biology papers and books, we explore the history, foundational principles, research methodologies, and the remarkable stories of the scientists behind them. Join us to connect with the roots of physical biology and spark ideas in a welcoming environment.
Organizers: Hong Qian, Xiaochan Xu
Speaker: Led by postdocs & PhDs, and everyone can be a host!
Audience: All with a strong interest in physical biology are warmly welcomed.
Venue: E14-326, Research Center, Westlake University
Contact Information
Ms. Jin Liang (梁金), liangjin@westlake.edu.cn, Center for Interdisciplinary Studies (CIS)
