Physical modeling of non-equilibrium processes in biological systems



Transport, Aggregation and Molecular cooperativity

Funding period 2017-2020

 

Announcements:

SFB Seminar

Tue, 23/01/2018 - 14:15
,
Campus SB, E2 6, Room E04

Prof. Dr. Holger Kress
(
Host: Dr. Jean-Baptiste Fleury
)
Biological Physics Group, University of Bayreuth

Size-dependent organelle transport during phagocytosis

Phagocytosis of bacteria and other pathogens by macrophages is a key process of the mammalian immune system. The intracellular maturation of phagosomes, which often leads to the degradation of the internalized pathogens, shows high organelle-to-organelle variations that are not clearly understood. An important part of the maturation is the phagosomal transport from the cell periphery towards the perinuclear region. We hypothesize that the phagosome size influences the phagosomal transport and therefore also potentially the maturation process. We tested this hypothesis by tracking phagosomes with different diameters between 1 μm and 3 μm inside macrophages. We show that the transport efficiency increases with increasing phagosome size although the instantaneous velocities of the investigated phagosomes are very similar to each other. In addition, we found that the share of bi-directional motion as well as the transport from the nucleus back to the periphery decreases with increasing phagosome size. We show that dynein is significantly involved in the phagosomal transport, in particular in the persistent centripetal transport of large phagosomes. In addition, actin-dependent motion is also contributing to the transport, in particular to the transport of small phagosomes. Furthermore we investigated the spatial distribution of dyneins and microtubules, and found that density differences between the nucleus-facing side of phagosomes and the opposite side can explain part of the observed transport characteristics. Our findings suggest that a basic size-dependent cellular sorting mechanism might exist that supports inward transport of large phagocytosed pathogens for facilitating their digestion and that simultaneously supports outward transport of small pathogen fragments for example for antigen presentation.

SFB Seminar

Thu, 25/01/2018 - 15:15
,
Campus SB, Building E2 6, Room E11

Dr. Daiki Matsunaga
(
Host: Prof. Dr. Christian Wagner
)
Rudolf Peierls Centre for Theoretical Physics, University of Oxford

Position control of magnetic particles/swimmers under flow

In recent years, magnetic particles have been extensively used in biomedical and microfluidic applications. Movements and collective behaviours of these particles are also interesting from a perspective of the active matter physics. In this talk, we firstly report our new method to control position of an ellipsoidal magnetic colloids inside a tube flow. Secondly, we explain mechanism of an interesting collective motion of magnetotactic bacteria.

 

 

IRTG Lecture

Tue, 30/01/2018 - 14:15
,
Campus SB, E2 6, Room E04

Dr. Monika Bozem, Phillip Knapp
(
Host: Dr. Hendrik Hähl
)
Department of Biophysics, UdS (HOM)

Electrochemical H2O2 determinations from single living human mono­cytes

Hydrogen peroxide (H2O2) belongs to the reactive oxygen species (ROS). In low concentrations (nM to low µM), it displays intra- and extracellular signaling functions, mainly by oxidizing target molecules, like proteins and lipids. Likewise, yet in much higher concentrations (high µM to mM), H2O2 is employed by specialized cells to kill pathogens, like bacteria. Cellular production of H2O2 is paralleled by effective H2O2 degradation due to a multitude of enzymatic systems. Thus, balanced intracellular [H2O2] levels are obtained, guaranteeing physiological functioning of the cell. Using a scanning electrochemical microscope (SECM) and platinum ultramicroelec­trodes, basal and stimulated H2O2 production and concomitant degradation from single primary human monocytes were measured in real-time and with high temporal resolution (1 Hz). Electro­chemically produced signals can be quantified for each measuring point, and thus enable insight into the dynamics of [H2O2] changes over time and under different patho-/physiological conditions.