Probing Exchange Pathways in One Dimensional Aggregates with Super Resolution Microscopy
Examining Supramolecular Exchange Microtubules are a natural example of a one dimensional (1D) supramolecular structure. Synthetic examples of 1D fibrils often have monomers linked by weak noncovalent interactions that allow monomers to exchange in and out of the fibrils. Albertazzi et al. (p. 491) used a combination of super resolution microscopy on individual fibrils and stochastic simulation to study monomer exchange in fibrils formed from stacked 1,3,5 benzenetricarboxamide motifs. Exchange did not require large scale depolymerization and repolymerization, or reassembly of fragments, but proceeded through individual monomers exchanging homogeneously throughout the fibrils. One dimensional supramolecular aggregates can swap constituent monomers through a homogeneous exchange mechanism. Supramolecular fibers are prominent structures in biology and chemistry. A quantitative understanding of molecular exchange pathways in these one dimensional aggregates was obtained by a combination of super resolution stochastic optical reconstruction microscopy and stochastic simulation. The potential of this methodology is demonstrated with a set of well defined synthetic building blocks that self assemble into supramolecular fibrils. Previous ensemble measurements hid all molecular phenomena underpinning monomer exchange, but the molecular pathway determined from single aggregate studies revealed unexpected homogeneous exchange along the polymer backbone. These results pave the way for experimental investigation of the structure and exchange pathways of synthetic and natural supramolecular fibers.
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