Energy consumption in chemical fuel-driven self-assembly

Nature extensively exploits high-energy transient self-assembly structures that are able to perform work through a dissipative process. Often, self-assembly relies on the use of molecules as fuel that is consumed to drive thermodynamically unfavourable reactions away from equilibrium. Implementing this kind of non-equilibrium self-assembly process in synthetic systems is bound to profoundly impact the fields of chemistry, materials science and synthetic biology, leading to innovative dissipative structures able to convert and store chemical energy. Yet, despite increasing efforts, the basic principles underlying chemical fuel-driven dissipative self-assembly are often overlooked, generating confusion around the meaning and definition of scientific terms, which does not favour progress in the field. The scope of this Perspective is to bring closer together current experimental approaches and conceptual frameworks. From our analysis it also emerges that chemically fuelled dissipative processes may have played a crucial role in evolutionary processes

Supramolecular systems chemistry

The field of supramolecular chemistry focuses on the non-covalent interactions between molecules that give rise to molecular recognition and self-assembly processes. Since most non-covalent interactions are relatively weak and form and break without significant activation barriers, many supramolecular systems are under thermodynamic control. Hence, traditionally, supra-molecular chemistry has focused predominantly on systems at equilibrium. However, more recently, self-assembly processes that are governed by kinetics, where the outcome of the assembly process is dictated by the assembly pathway rather than the free energy of the final assembled state, are becoming topical. Within the kinetic regime it is possible to distinguish between systems that reside in a kinetic trap and systems that are far from equilibrium and require a continuous supply of energy to maintain a stationary state. In particular, the latter systems have vast functional potential, as they allow, in principle, for more elaborate structural and functional diversity of self-assembled systems-indeed, life is a prime example of a far- from- -equilibrium system. In this Review, we compare the different thermodynamic regimes using some selected examples and discuss some of the challenges that need to be addressed when developing new functional supramolecular systems

Uncovering the Selection Criteria for the Emergence of Multi-Building-Block Replicators from Dynamic Combinatorial Libraries

<p>A family of self-replicating macrocycles was developed using dynamic combinatorial chemistry. Replication is driven by self-assembly of the replicators into fibrils and relies critically on mechanically induced fibril fragmentation. Analysis of separate dynamic combinatorial libraries made from one of six peptide-functionalized building blocks of different hydrophobicity revealed two selection criteria that govern the emergence of replicators from these systems. First, the replicators need to have a critical macrocycle size that endows them with sufficient multivalency to enable their self-assembly into fibrils. Second, efficient replication occurs only for library members that are of low abundance in the absence of a replication pathway. This work has led to spontaneous emergence of rephcators with unrivalled structural complexity, being built from up to eight identical subunits and reaching a MW of up to 5.6 kDa. The insights obtained in this work provide valuable guidance that should facilitate future discovery of new complex self-replicating molecules. They may also assist in the development of new self-synthesizing materials, where self-assembly drives the synthesis of the very molecules that self-assemble. To illustrate the potential of this concept, the present system enables access to self-assembling materials made from self-synthesizing macrocycles with tunable ring size ranging from trimers to octamers.</p>