Receive our informations
Share
Cell mechanics of biomimetic and living systems
Keywords :
cell mechanics, actin dynamics, active systems
PI: Timo Betz (CV)
The mission:
The primary goal of the team is to understand the mechanics of complex systems by approaching it from bottom up, using biomimetic active systems, and from top down, by investigating simple living structures. The aim is to eventually connect the two approaches to fully understand the working mechanicsms that allow living systems to move and to modify its mechanical properties. A major direction is the investigation of driven systems, that are out of equilibrium, and to exend current theoretical concepts from the equilibrium case to complex active systems.
The main projects:
Cytoskeleton membrane interaction in red blood cells
The cytoskeleton of red blood cells dominates the mechanical behavior of the red blood cells. We investigate the mechanical consequences of the membrane cytoskeleton interaction by exploiting the thermal fluctuation of the membrane, and by active and passive rheology.
Mechanical measurements of the actin cortex
The membrane of most living cells gets its mechanical stability from the underlying actin cortex, which is in general a complex network of actin and several actin associated proteins. We are interested to dissect the importance of the different participants for the mechanical stability using in vitro reconstituted liposomes that contain a biomimetic actin cortex.
Mechanics of bleb formation
Cell blebs have been shown to occur in many cells during morphological events such as cell division and cell motility. To produce a bleb, it is believed that the actin cortex underlying the plasma membrane creates active contractile stresses that are mediated by myosin II motors. The increased tension eventually leads to either a fracture of the actin cortex, or a detachment of the cortex from the plasma membrane. Subsequently, hydrostatic pressure results in a fast growing membrane bleb. Within a minute a new actin cortex is formed, and newly arriving myosin II motors retract the bleb. We aim to study the mechanical events during the full life cycle of a bleb using advanced optical tools, traction force microscopy and nanosurgery.
Mechanics of confined actin gels
To move forward, the bacteria Listeria exploits the actin pool of an infected cell to create actin comets that propel it forward. Many properties of this system are well understood, and biomimetic bead motility essay allow reproducing this movement using reconstituted proteins. We aim to investigate the viscoelastic properties of the gel that forms around the bead by using optical tweezers. In a first stage we perform indentation experiments that are followed by active microrheology to understand possible effects of the layered and prestrained gel that is formed around the bead.
The Tools:
We developped a new optical tweezer based method that allows to measure the fluctuation spectrum of cytoskeleton-membrane systems with very high spatial and temporal accuracy. The setup can also be operated as an optical tweezer with multiple optical traps that are created by timesharing, where the laser is switched with a time resolution of 4µs to create multiple optical tweezers. This can then be used to measure multiple points of a biomimetic or living cell, or to use active methods to directly determine the mechanical properties of a system.