The goal of of A5 is to understand how condensates respond to mechanical forces and how condensate-mediated capillary forces influence the shape and organization of biopolymers.

Biomolecular condensates are mostly considered as special biochemical environments. However, due to their tendency to minimize their interfacial area, condensates generate relevant capillary forces that can bundle and bend soft cellular structures. Recently, the Grill lab has explored the mechanical effects of condensates on various biopolymers such as nucleic acids and cytoskeletal filaments. In collaboration with the Hyman and Jülicher groups, the Grill group has discovered the prewetting and co-condensation of transcription factors on DNA and that condensates can bundle DNA. Furthermore, the Grill group has discovered a condensate dynamic instability that is crucial to establishing the actin cell cortex during early nematode development. Finally, preliminary data from the Grill lab demonstrate shape changes of cortical condensates are likely driven by condensate surface tension and identify a mechanical role of DNA-binding proteins during the assembly of the nuclear periphery (Collaboration with von Appen group at MPI-CBG). Despite this progress, the rich interplay between condensate interfacial energies, condensate-polymer interaction energies, and biopolymer bending energies has not been systematically studied and remains poorly understood.

1) How do condensates respond to mechanical forces and exert capillary forces on various cellular structures?

2) Can we predict the mechanical condensate-polymer behavior?

3) How to measure the interfacial properties and interaction energies of condensates and their substrates?

Regulatory RNA folding in and around condensates

The PhD students will be trained in in soft matter physics concepts, single-molecule experiments, protein and nucleic acid molecular biology methods, data and image analysis methods and state-of-the-art instrumentation such as optical tweezers and light-sheet microscopy.

• Candidates have a Masters degree in physics, biology or related fields
• Candidates should have a sound basis in (theoretical) biophysics, polymer science, quantitative biology, or closely related fields.
• Experience in microscopy and protein isolation methods are expected

The goal of A1 is to understand how surface condensation of scaffold proteins at biological membranes can control the patterning and the mechanics of an acto-myosin cell cortex.

The formation of epithelial tissue requires precise spatiotemporal control of cell surface properties such as formation of adhesion complexes that are linked to the cell cortex at the level of the cell membrane^1,2. The Honigmann group has discovered that surface condensation of ZO scaffold proteins at the membrane is a mechanism that cells exploit to pattern adhesion complexes and the actin cortex³. In vitro reconstitutions have shown that ZO surface condensates can nucleate and bundle actin fibers, which can drive the formation of a variety of cortical patterns^4-6. How ZO surface condensation and actin polymerization are linked and what mechanical properties emerge from this is not understood.

How does surface condensation of ZO proteins induce actin recruitment and polymerization? and What are the mechanical properties of a condensed ZO1-actin cortex on the membrane?

Linking surface condensation of scaffold proteins to the assembly of cell junctions

The PhD students will be trained in protein and membrane biochemistry methods including membrane reconstitutions, biophysical methods such as fluorescence fluctuation spectroscopy, in addition to super-resolution microscopy and image analysis methods.

• Candidates have a Masters degree in biophysics or related fields
• Candidates are expected to have a solid basis in physics, biology, or related fields.
• Experience in fluorescence microscopy is plus