Dronpa: a light-switchable fluorescent protein for opto-biomechanics.

Since the development of the green fluorescent protein, fluorescent proteins (FP) are indispensable tools in molecular biology. Some FPs change their structure under illumination, which affects their interaction with other biomolecules or proteins. In particular, FPs that are able to form switchable dimers became an important tool in the field of optogenetics. They are widely used for the investigation of signaling pathways, the control of surface recruitment, as well as enzyme and gene regulation. However, optogenetics did not yet develop tools for the investigation of biomechanical processes. This could be leveraged if one could find a light-switchable FP dimer that is able to withstand sufficiently high forces. In this work, we measure the rupture force of the switchable interface in pdDronpa1.2 dimers using atomic force microscopy-based single molecule force spectroscopy. The most probable dimer rupture force amounts to around 80 pN at a pulling speed of 1600 nm/s. After switching of the dimer using illumination at 488 nm, there are hardly any measurable interface interactions, which indicates the successful dissociation of the dimers. Hence this Dronpa dimer could expand the current toolbox in optogenetics with new opto-biomechanical applications like the control of tension in adhesion processes.