Concentration‐Dependent Self‐Assembly and Nanoparticle Maturation of Reflectins

Cephalopods dynamically modulate coloration for camouflage and communication through iridophores whose Bragg reflector‐like ultrastructures contain high‐refractive‐index proteins known as reflectins. However, the mechanisms linking concentration, conformation, and nanoparticle stabilization in full‐length reflectins remain poorly understood. Here, coarse‐grained molecular dynamics simulations of Doryteuthis pealeii reflectin A2 (RfA2) across five concentrations are combined with dynamic light scattering (DLS) and circular dichroism (CD) measurements. The simulations reveal rapid initial protein aggregation followed by slower structural maturation, during which interprotein interaction energy and contact networks continue to evolve. A simulation‐derived concentration‐dependent crossover separates multi‐cluster vs single‐cluster regimes and DLS shows larger assemblies at higher experimental concentrations. The simulations further delineate region‐specific secondary‐structure reorganization and CD demonstrates concentration‐sensitive structural changes with a distinct secondary‐structure redistribution. Moreover, the simulations predict concentration dependence in the contribution of intermolecular contact network reorganization; the L1, L3, and L5 linker regions supplied many of these contacts, with L3 providing the dominant contribution. Overall, these findings establish a molecular‐level framework where concentration governs RfA2 self‐assembly and continued conformational and intermolecular reorganization during maturation, providing insight into sequence‐ and assembly‐level principles regarding iridophore optical function and reflectin‐based materials design.