Berlin 2008 – scientific programme

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BP: Fachverband Biologische Physik

BP 17: Physics of Cells

BP 17.5: Talk

Wednesday, February 27, 2008, 15:00–15:15, PC 203

Dynamics of different probe particles to study local micro-environments inside living cells — •Michael Duits, Yixuan Li, Siva Vanapalli, and Frieder Mugele — MESA+ institute, University of Twente, PO Box 217, 7500 AE The Netherlands

To understand the dynamics of particles inside living cells in relation to intracellular rheology, we examined living endothelial cells in untreated form, and after (chemical) interventions, aimed at revealing specific contributions to particle motions via driving forces or passive mechanical resistances. Endogenous granules (EG) and ballistically injected particles (BIP) were used as tracers. At 37 C the mean-squared displacement (MSD) showed different time dependence for the two probes. While EGs showed only a linear dependence, for BIPs also a transition to a plateau at small lagtimes was observed. Moreover, the (normalized) MSDs were much larger for the EGs. This suggests different local micro-environments for EGs and BIPs. Also the sets of individual trajectories were analyzed. Here, both the magnitude and the power-law exponent showed distributions that suggest heterogeneity in the environment for both probes. Depletion of intracellular ATP resulted in opposite effects on the MSDs of EGs and BIPs. While for EGs the MSD and the fraction of trajectories with superdiffusive exponents were reduced, for BIPs an increase in MSD was found. It thus seems that ATP depletion not only annihilates active processes, but also alters the cytoskeleton. These observations of cytoskeletal network heterogeneities have profound implications for the quantification of global mechanical behavior in living cells.