One key feature of biological systems is the existence of chemically fueled, transient structure and function, like the on-demand formation/degradation of tubulin, actin fibers etc. Supramolecular polymers as synthetic mimic of such biomaterials has shown great promise in a number of areas, including biomedicine, sensing and energy harvesting. However, the main challenge is to actively regulate the shape, function and performance of these materials, while maintaining constant, physiological conditions. This has inspired recent research towards temporal control of nanostructures, which is achieved by using (bio-)catalysis to activate building blocks and thereby drive assembly. In this regard, potential for design of active supramolecular nanostructures based on peptide nanotechnology is increasingly appreciated. The objective of this work is demonstration of active encoding of nanostructures by using simple amino acids, resulting in transient conducting nanowires. We designed a self-assembling core molecule with two in-built competing reactive sites, consisting of the organic semiconductor naphthalenediimide (NDI), conjugated with D and L enantiomer of tyrosine methyl esters. The stereoselective fast enzymatic reaction at the L enantiomer compared to the D enantiomer provides the necessary kinetic competition to achieve temporal control over assembly. By simply adding one of a range of encoding amino acids in the presence of enzyme α-chymotrypsin, we achieve pathway selection between hydrolysis and acylation at both chiral ends. This results in an in situ modification of the amphiphilic structures, giving rise to unique self-assembly trajectories that are time programmed by the nature of encoding amino acid. Taking advantage of the semiconducting nature of the NDI core, electronic wires could be formed and subsequently degraded, resulting in temporally regulated electro-conductivity. Such a system holds great promise towards interfacing biology with electronics. Overall, the biocatalytic incorporation of encoding amino acids around a functional core offers a general approach to modulate, switch or fine-tune supramolecular structures over time.

Amino acid-encoded biocatalytic self-assembly enables the formation of tansient functional nanostructures

2019 Spring National Meeting

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