Chemically Fueled, Active Droplets Prevent the Aging of Peptides into Amyloid-Like Fibers.

Abstract

Protein aggregation is a hallmark of molecular aging and is implicated in various neurodegenerative diseases. Aggregation proceeds via autocatalytic, thermodynamically favored pathways. Yet in living systems, dynamic, active regulation and compartmentalization─such as in biomolecular condensates─can suppress or delay such irreversible assembly. Here, we describe a peptide that exhibits pathway-dependent self-assembly into either amyloid-like fibers or fuel-driven droplets. The peptide was designed to undergo chemical activation via a carbodiimide-driven reaction cycle, which transiently neutralizes its overall charge and promotes droplet formation. In the absence of fuel, the peptide slowly self-assembles into stable fibers through an autocatalytic process resembling amyloid aging. However, upon repeated or continuous fueling, the peptide forms active droplets that persist for days and remain resistant to fiber formation. Thus, we demonstrate that the fuel-driven active state can completely suppress fiber nucleation and growth. These findings demonstrate that the constant turnover of peptides through activation and deactivation can act as a kinetic sink, sequestering peptides and delaying the transition to the thermodynamically favored fiber state. Our results establish a minimal, chemically controlled system in which phase behavior and aging can be modulated by energy input. This work provides new insight into how nonequilibrium processes can temporally regulate self-assembly, mimicking cellular strategies for protein homeostasis. More broadly, it offers a model for studying the prevention of pathological aggregation and opens routes toward designing synthetic systems that emulate the dynamic regulation of living matter.