Kolloquium 09.05.2017 16.30 s.t in Room 222 of the Institute for Applied Physics

Nonlinear dynamics of beating cilia and flagella: Swimming, steering, and synchronization

Dr. Benjamin M. Friedrich, TU Dresden, Center for Advancing Electronics Dresden (cfaed), Biological Algorithms Group


Cilia and flagella represent a best-seller of nature: their regular bending waves propel cellular swimmers such as sperm cells and green alga in a liquid. Collections of these slender cell appendages can synchronize their beat to pump fluids inside human airways and brain ventricles effectively.
In this talk, I will address the physics of flagellar swimming and how mechanical and chemical signals control these biological oscillators.
In the first part, I will a present a theory of sperm chemotaxis, i.e. the directed navigation of flagellated sperm cells in response to signaling molecules released by the egg. We show how swimming along helical paths results in an effective navigation strategy that can cope with molecular shot noise of cellular concentration measurements. Thereby, spatial information about a concentration gradient becomes encoded in the phase of an oscillatory temporal signal perceived by the swimming cell along its helical path. This theory has recently been confirmed by experiments that track swimming sperm cells in three space dimension in artificial concentration fields of signaling molecules [1].
In the second part, I will discuss flagellar synchronization as an emergent phenomenon in collections of several flagella, which arises from mutual a hydro-mechanical coupling. We present a theory of the beating flagellum as a noisy limit-cycle oscillator, which is fully calibrated by experimental data. In particular, we show using theory and experiment how external mechanical forces change speed and shape of the flagellar beat, or even stall the beat reversibly [2]. This flagellar load-response is key prerequisite for flagellar synchronization.
We present a link between the efficiency of the flagellum to convert chemical energy into mechanical work and its ability to synchronize. Finally, we characterize the beating flagellum as a noisy oscillator, whose non-equilibrium fluctuations induce stochastic phase-slips in pairs of phase-locked flagella [3].

[1] J.F. Jikeli et al.: Sperm navigation along helical paths in 3D chemoattractant landscapes, Nature Communications 6, 2015
[2] G.S. Klindt, C. Ruloff, C. Wagner, B.M. Friedrich, Load-response of the flagellar beat, Phys. Rev. Lett. 117, 2016
[3] R. Ma, G.S. Klindt, I.-H. Riedel-Kruse, F. Jülicher, B.M. Friedrich: Active phase and amplitude fluctuations of flagellar beating, Phys. Rev. Lett. 113, 2014

Einladende: S. Gurevich

All Termine SS 2017

Highlights der Physik

Struktur & Symmetrie

19. - 23. September 2017, Münster

Die 17. Ausgabe der „Highlights der Physik“ Ausstellung findet diemal in Münster statt. Das Thema Struktur und Symmerie hat starke Berührungspunkte mit Nonlinear Science. Weitere Informationen finden Sie auf der offiziellen Webseite der Veranstaltung  Link zur Webseite

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Das Center for Nonlinear Science (CeNoS) ist eine zentrale wissenschaftliche Einrichtung der Westfälischen Wilhelms-Universität Münster und besteht aus den beteiligten Arbeitsgruppen die im Moment sechs verschiedenen Fachbereichen angehören. Mitglied kann jede an der Thematik interessierte Arbeitsgruppe oder jede/r interessierte Wissenschafter/in der Universität Münster werden.Das CeNoS versteht sich als Dach für die grundlagenorientierte Forschung und Lehre an Fragestellungen zu nichtlinearen Systemen sowie für Anwendungen der Ergebnisse in verschiedenen Gebieten. Darüber hinaus dient es als Forum des interdisziplinären Dialogs zwischen Wissenschaftlern und Wissenschaftlerinnen verschiedener wissenschaftlicher Fachdisziplinen.