Drittes Physikalisches Institut - AG Schmidt

Bachelor-, Master-, PhD and Postdoc positions available

In the group of Prof. Christoph Schmidt, Molecular and Cellular Biophysics, there are positions available as of now for bachelor students, master students, Phd students and postdocs.

Specific areas of research with open positions are:
ERC Advanced Grant "The Physical Basis of Cellular Mechano-chemical Control Circuits"

Movie 1: Stem-cell derived cardiomyocytes, with Z-bands labeled, attached to a patterned soft substrate. Regular contractions must be controlled by mechanical signaling across the whole cell.

Biological cells possess a chemical "sense of smell" and a physical "sense of touch". To interact physically, cells are equipped with both, force-generating structures, and stress sensors including force-sensitive structural proteins and mechanosensitive ion channels. A major challenge for biophysical research remains to identify the crucial mechanosensitive elements in cells and by their connections to biochemical signals and transcription control. The overall goal of the project is to quantitatively establish pathways from mechanical input signal to transcription control. We use optical traps and atomic force microscopy to manipulate cells and infrared-fluorescent single-walled carbon nanotubes to track intracellular dynamics.

Research Center SFB 937 "Collective Behavior of Soft and Biological Matter" Project "Active model biopolymer networks in vitro and in vivo"

Movie 2: Fluorescently-labeled actin cortices in a model system of water droplets in oil can be assembled in Xenopus frog egg extract as highly active quasi-2D layers near the interface. Myosin motors cause the networks to contract and form a cap which maintains a dynamic steady state, i.e. constantly looses actin by depolymerization and gains actin by accretion from the periphery.

Active matter is defined as a soft material internally driven by mechanical non-equilibrium processes. The cytoskeleton is a prototypical example of this state of matter. We here study three-component in vitro model systems made from cytoskeletal filaments, motor proteins and physiological crosslinkers as well as single cells. We use laser-interferometry-based one-and two-particle microrheology to analyze the interplay between viscoelastic properties and non-equilibrium stress fluctuations. We also develop a new approach using fluorescent single-walled carbon nanotubes as multi-scale stealth probes for measuring viscoelasticity and fluctuations in living cells.

Research Center SFB 937 "Collective Behavior of Soft and Biological Matter"
Project "Self-organization of the nuclear array in early Drosophila embryos"

Movie 3: Early Drosophila embryo in the syncytial stage. Chromosomes are fluorescently labeled and four nuclear duplications are seen.

In this project we study biological active matter on the tissue level. The Drosophila blastoderm embryo is a syncytium with up to ~6000 nuclei that are arranged in a 2D layer at the cortex of the embryo, embedded in F-actin and microtubule networks. The nuclei and the cytoskeleton undergo stereotypic movements and changes in organization during development. Forces generated by motor proteins interacting with actin and microtubules drive the system out of equilibrium. We will develop methods to record local and collective fluctuations and movements of nuclei, centrosomes, molecular motors during waves of collective nuclear divisions. We employ fluorescent single-walled carbon nanotubes as stealth probes to record fluctuations and directed motions in the fly embryos. We also develop mathematical and statistical methods to analyze and model the experimental data.

Research Center SFB 803 "Functionality Controlled by Organization in and between Membranes",
Project "Mechanosensitive Channels in model lipid bilayers"
Primary cilium of kidney epithelial cells with mechanosensitive channels. a) Schematic sketch of a primary cilium and its intracellular anchoring, with PC2 channels that are believed to be mechanically opened. b) DIC micrograph of a primary cilium deflected in buffer flow of ~4.8 µm/s. c) DIC micrograph of a primary cilium with an attached bead deflected by an optical trap.

Many cells have developed specialized structures to detect forces and mechanical signals. A prominent role is believed to be played by mechanosensitive ion channels. We use microfabricated porous substrates and microfluidics in conjunction with cell-free protein expression to reconstitute mechanosensitive channels and to gain a micromechanical understanding of their function. We use electrical recording to measure channel activity and hydrostatic pressure, optical trapping and atomic force microscopy to drive channel opening.

Please inquire for details and direct applications by email to: christoph.schmidt@phys.uni-goettingen.de