Force-induced α-β transitions in coiled coil (CC) structures
by Anna-Maria Tsirigoni
Spectral Analysis of a Fast Biomolecular Transition in Magnetic Tweezers Measurements
by Sebastian Belau
Location: MLUconf
Time: 15.20 – 17.00
Abstracts
Force-induced α-β transitions in coiled coil (CC) structures
Anna-Maria Tsirigoni
Coiled coils (CCs) are α-helical structures that can be found in a large number of proteins of the cytoskeleton and the extracellular matrix. Increasing evidence indicate that CCs undergo a mechanically induced structural transition leading to the formation of β-sheet structures with possible amyloid-like character. However, the molecular determinants of this α-β transition (αβT) are currently unknown. The aim of this project is to unravel the intrinsic and extrinsic factors that are responsible for this transition, when applying a shear force as the key constraint. Specifically, it will answer the question if and how this force-induced αβT depends on CC sequence and length and how it compares to the temperature-induced αβT of CCs. The investigation will be performed in two ways, firstly at the single-molecule level using AFM-based single molecule force spectroscopy, where the force-induced αβT will be studied. Secondly, at the ensemble level, where CCs serve as physical crosslinks in poly(ethylene glycol)-based biohybrid hydrogels. The formed biohybrid hydrogel acts as force transducer and therefore allows for mechanically loading the CC crosslinks, in order to observe the αβT using a standard rheology setup. The above mentioned methods will be applied to synthetic as well as recombinantly expressed CC sequences, which are known to undergo force-induced αβT. This combination will allow for discriminating sequence specific versus universal features that determine the αβT and it’s (ir)reversibility.
Spectral Analysis of a Fast Biomolecular Transition in Magnetic Tweezers Measurements
Sebastian Belau
Dynamic structural changes in biomolecules such as proteins and DNA are crucial for their correct function. These processes often involve transient intermediate states that occur on the (sub-)millisecond timescale. The investigation of such fast dynamics is experimentally challenging in particular in single molecule measurements. Here we investigate the limited branch migration of a Holliday junction within the torsionally constraint DNA of a magnetic tweezers setup. We gain access to the force-dependent stepping dynamics of the junction in the xx µs to x ms range using power spectral density analysis of the DNA length fluctuations. We expect that this technique can be extended to other biological systems where the individual structural transitions are too short and fast to be resolved in real-time. In our experiments the DNA length is obtained from the position of an attached magnetic particle.
