In biology, self-assembly of proteins and energy-consuming reaction cycles are intricately coupled. For example, tubulin is activated and deactivated for assembly by a guanosine triphosphate (GTP)-driven reaction cycle, and the emerging microtubules catalyze this reaction cycle by changing the microenvironment of the activated tubulin. Recently, synthetic analogs of chemically fueled assemblies have emerged, but examples in which assembly and reaction cycles are reciprocally coupled remain rare. In this work, we report a peptide that can be activated and deactivated for self-assembly. The emerging assemblies change the microenvironment of their building blocks, which consequently accelerate the rates of building block deactivation and reactivation. We quantitatively understand the mechanisms at play, and we are thus able to tune the catalysis by molecular design of the peptide precursor.

In living systems, fuel-driven assembly is ubiquitous, and examples include the formation of microtubules or actin bundles. These structures have inspired researchers to develop synthetic counterparts, leading to exciting new behaviors in man-made structures. However, most of these examples are serendipitous discoveries because clear design rules do not yet exist. In this work, we show design rules to drive peptide self-assembly regulated by a fuel-driven reaction cycle. We demonstrate that, by altering the ratio of attractive to repulsive interactions between peptides, the behavior can be toggled between no assembly, fuel-driven dissipative self-assembly, and a state in which the system is permanently assembled. These rules can be generalized for other peptide sequences. In addition, our finding is explained in the context of the energy landscapes of self-assembly. We anticipate that our design rules can further aid the field and help the development of autonomous materials with life-like properties.

Complex coacervated-based assemblies form when two oppositely charged polyelectrolytes combine to phase separate into a supramolecular architecture. These architectures range from complex coacervate droplets, spherical and worm-like micelles, to vesicles. These assemblies are widely applied, for example, in the food industry, and as underwater or medical adhesives, but they can also serve as a great model for biological assemblies. Indeed, biology relies on complex coacervation to form so-called membraneless organelles, dynamic and transient droplets formed by the coacervation of nucleic acids and proteins. To regulate their function, membraneless organelles are dynamically maintained by chemical reaction cycles, including phosphorylation and dephosphorylation, but exact mechanisms remain elusive. Recently, some model systems also regulated by chemical reaction cycles have been introduced, but how to design such systems and how molecular design affects their properties is unclear. In this work, we test a series of cationic peptides for their chemically fueled coacervation, and we test how their design can affect the dynamics of assembly and disassembly of the emerging structures. We combine them with both homo- and block copolymers and study the morphologies of the assemblies, including morphological transitions that are driven by the chemical reaction cycle. We deduce heuristic design rules that can be applied to other chemically regulated systems. These rules will help develop membraneless organelle model systems and lead to exciting new applications of complex coacervate-based examples like temporary adhesives.

In chemically fueled supramolecular materials, molecular self‐assembly is coupled to a fuel‐driven chemical reaction cycle. The fuel‐dependence makes the material dynamic and endows it with exciting properties like adaptivity and autonomy. In contrast to the large work on the self‐assembly of small molecules, we herein designed a diblock copolymer, which self‐assembles into transient micelles when coupled to a fuel‐driven chemical reaction cycle. Moreover, we used these transient block copolymer micelles to locally increase the concentration of hydrophobic reagents and thereby function as a transient nanoreactor.

Membraneless organelles are droplets in the cytosol that are regulated by chemical reactions. Increasing studies suggest that they are internally organized. However, how these subcompartments are regulated remains elusive. Herein, we describe a complex coacervate‐based model composed of two polyanions and a short peptide. With a chemical reaction cycle, we control the affinity of the peptide for the polyelectrolytes leading to distinct regimes inside the phase diagram. We study the transitions from one regime to another and identify new transitions that can only occur under kinetic control. Finally, we show that the chemical reaction cycle controls the liquidity of the droplets offering insights into how active processes inside cells play an important role in tuning the liquid state of membraneless organelles. Our work demonstrates that not only thermodynamic properties but also kinetics should be considered in the organization of multiple phases in droplets.