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DTSTART;TZID=America/New_York:20231012T130000
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UID:10002826-1697115600-1697119200@cmsa.fas.harvard.edu
SUMMARY:Contractility\, structure formation and fluctuations in active gels\, with and without molecular motors
DESCRIPTION:Active Matter Seminar\n\n\nSpeaker: Fred MacKintosh (Rice University) \nTitle: Contractility\, structure formation and fluctuations in active gels\, with and without molecular motors \nAbstract: Various processes in living cells depend on contractile forces that are often generated by myosin motors in concert with polar actin filaments. A textbook example of this is the actomyosin contractile ring that forms during cell division. Recent evidence\, however\, has begun to suggest alternate or redundant mechanisms that do not depend on myosin. Experiments on simplified\, reconstituted systems also point to contractility and structure formation in disordered\, apolar arrays of filaments. We propose a motor-free mechanism that can generate contraction in biopolymer networks without the need for motors such as myosin or polar filaments such as actin. This mechanism is based on active binding and unbinding of cross-linkers that breaks the principle of detailed balance\, together with the asymmetric force-extension response of semiflexible biopolymers. We discuss the resulting force-velocity relation and other implications of this\, as well as possible evidence for non-motor force generation.
URL:https://cmsa.fas.harvard.edu/event/am-101223/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Active Matter Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Active-Matter-Seminar-10.12.23.png
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DTSTART;TZID=America/New_York:20231026T130000
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CREATED:20240223T070828Z
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UID:10002825-1698325200-1698328800@cmsa.fas.harvard.edu
SUMMARY:Scaling behavior and control of nuclear wrinkling
DESCRIPTION:Active Matter Seminar\n\n\nSpeaker: Nicolas Romeo (UChicago) \nTitle: Scaling behavior and control of nuclear wrinkling \nAbstract: The cell nucleus is enveloped by a complex membrane\, whose wrinkling has been implicated in disease and cellular aging. The biophysical dynamics and spectral evolution of nuclear wrinkling during multicellular development remain poorly understood due to a lack of direct quantitative measurements. We characterize the onset and dynamics of nuclear wrinkling during egg development in the fruit fly when nurse cell nuclei increase in size and display stereotypical wrinkling behaviour. A spectral analysis of three-dimensional high-resolution live-imaging data from several hundred nuclei reveals a robust asymptotic power-law scaling of angular fluctuations consistent with renormalization and scaling predictions from a nonlinear elastic shell model. We further demonstrate that nuclear wrinkling can be reversed through osmotic shock and suppressed by microtubule disruption\, providing tunable physical and biological control parameters for probing the mechanical properties of the nuclear envelope\, highlighting in passing the importance of nonlinear response to biological robustness.
URL:https://cmsa.fas.harvard.edu/event/am-102623/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Active Matter Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Active-Matter-Seminar-10.26.23.png
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