Femtosecond Single-Particle Diffractive Imaging of Computationally Designed De Novo Protein Complexes with XFEL Pulses

Outrunning radiation damage, femtosecond pulses of x-ray free-electron lasers (XFELs) open up the possibility of imaging the structure and dynamics of uncrystallized single-macromolecules, frozen in time at room-temperature, at ultrafast timescales. Imaging light-induced ultra-fast dynamics in uncrystallized macromolecules is one of the ultimate goals of XFELs, however almost all natural photoactive proteins exhibiting relevant ultrafast dynamics are too small to be imaged with the current flux capabilities of XFEL facilities without crystallization. Hence large photoactive protein systems, ideally ~MDa is desired for ambitious ps/fs time-resolved single-particle imaging (SPI) of macromolecules. Designing such large photoactive proteins is a potential-solution and with the recent advances in deep-learning, computational protein design can likely help create such large photoactive and other dynamic functional de novo protein complexes (stable in extreme conditions) with atomic precision for holographic and time-resolved SPI (TR-SPI). And in turn XFELs with their ability to image at ultrafast timescales will likely help iteratively optimize the design of de novo photoactive proteins by capturing the chromophore, protein side-chain interactions and collective motions and dynamics of the designer-proteins at ps/fs timescales. In this poster, we present the preliminary results on imaging biomedically relevant de novo octahedral protein complexes with soft-x-ray laser pulses at SQS, EuXFEL.