Time-resolved monitoring of the formation of toroid topologies in polypeptide self-assembly

We request beam time on ID2 with the stopped-flow device to monitor the formation of toroid poly(benzyl-L-glutamate) (PBLG) nanoparticles. Upon solvent-shifting (good to poor solvent) this hydrophobic homopeptide forms nanoparticles (100-800 nm) with a variety of morphologies, including toroids and other multi-handle topologies. Until now, no satisfactory mechanism has been proposed to account for the emergence of these intriguing shapes. Our preliminary experiments unambiguously show that the toroids exist in solution (cryo-TEM, SAXS) and that they form within less than 10s (stopped-flow). However, more information is needed about the structural changes at this time scale. Today, time resolved USAXS-SAXS coupled with stopped-flow is the only experiment able to monitor the topological changes from an isotropic droplet to a toroidal particle. Beyond the specific case of PBLG, these results will provide new information about the nucleation and growth mechanism in the context of nanopreci