Biophysical Society Bulletin | May 2022

Publications

Know the Editor Timo Betz

Georg August University Göttingen

Editor, Cell Biophysics Biophysical Journal

Timo Betz

What has been your most exciting discovery as a biophysicist?

When I started to work on red blood cell membrane fluctua- tions, I realized that by using a precise measurement of both the spontaneous fluctuations and the mechanical properties, we can make clear predictions about the metabolic processes that are actively driving the fluctuations. This was possible by a stringent application of statistical mechanics extended to nonequilibrium processes. Although we could prove that the fluctuations are partially driven by active processes, we could not cross-check our quantitative predictions, simply because one cannot simply access genetic changes in human red blood cells. However, we were able to carry the experimental approach over to mouse oocytes. Again, by combining precise measurement of the mechanical properties inside the cell, by using optical tweezers, and the spontaneous fluctuations of endogenous granules, it was possible to measure molecular properties of the myosin-V motor, which drives the granules’ motion. The fascinating thing was that we could recover the values obtained from single-molecule experiments, although we were merely looking at average statistical fluctuations and knowing the viscoelastic properties. It was like Jean Baptiste Perrin must have felt when he determined the Avogadro con- stant by just watching the diffusion of particles. What are you currently working on that excites you? I am fascinated to study how living objects fulfil their function with such amazing reliability by using the nonlinear and non- equilibrium physics that dominates living cells. As a physicist, I love statistical mechanics because it provides a wonderful access to understand the microscopic world. Unfortunately, many of the powerful tools provided by equilibrium statisti- cal mechanics cannot be applied to cellular systems, sim- ply because these are inherently driven out of equilibrium. Currently, we are working on new analysis methods that allow quantification of general mechanical properties and active forces of such living, nonequilibrium systems by simply observing the active and passive motion of particles and molecules inside cells. Although the general consensus of the past years was that it is impossible to fully quantify a system by simple passive observations, new theoretical and exper- imental methods are being developed that may eventually provide this information. The dream is to directly understand active forces, mechanical properties, and the dynamic chang- es of both within a living cell by purely observing the motion of intercellular objects.

Editor’s Pick Biophysical Journal Tether-guided lamellipodia enable rapid wound healing Elgin Korkmazhan, Andrew S. Kennard, Carlos Garzon-Coral, Clau- dia G. Vasquez, Alexander R. Dunn “As the outermost layer of organs, epithelia must withstand and respond to various physical and chemical insults. How- ever, relatively few studies to date have examined how cells act to repair damage on the seconds timescale. Here, using in vitro and zebrafish models, epithelia were subjected to acute detachment from the underlying extracellular matrix. Even during large-scale detachments, cells remained attached to the extracellular matrix via long membrane tethers. Cells rap- idly extended lamellipodia along these tethers, allowing them to reestablish contact with the underlying substrate on the seconds timescale. The tether-guided lamellipodia observed may constitute an understudied mechanism used by epithelial cells to rapidly repair the damage caused by localized wound- ing events.”

Version of Record Published February 11, 2022 DOI:https:/doi.org/10.1016/j.bpj.2022.02.006 FollowBPS Journals

on Twitter @BiophysJ @BiophysReports @BiophysicistJ

May 2022

8

T H E N E W S L E T T E R O F T H E B I O P H Y S I C A L S O C I E T Y