Precision oligomers for the control of self-assembly and catalysis

The precise design of chain molecules is exploited by living organisms to, e.g., store information, catalyze reactions, or guide assembly processes. Reaching such a degree of precision in synthetic chains not based on peptides nor nucleic acids can nowadays be achieved for oligomers of moderate length. In this context, we have developed a flexible synthetic route of functional oligo(triazole-urethane)s, allowing us to install a wide range of chemical groups in a specific sequence along short chains of precise length and chirality. Among these, we have especially focused on groups active in the trifunctional catalytic aerobic oxidation of alcohols, and on hydrogen-binding groups derived from nucleobases (recognition units). When oligomers bearing the three groups involved in this catalytic cycle are attached along trimeric chains, a very strong effect of sequence on catalytic activity is observed, with a factor of up to ten measured between the best and worse sequences. This can be partly explained by network graphs obtained from molecular dynamics simulations, showing how non-active groups of the chain backbone may prevent the catalytic groups to be spatially close and cooperate in the catalytic cycle, depending on sequence. We also synthesized more complex hexameric chains bearing complementary recognition units and elements of the catalytic triad, which are not independently active but assemble in solution to form a quaternary catalytically-active structure. This results in a catalytic turn-over frequency (TOF) whose concentration- and temperature-dependence can be correlated to the binding constants of the recognition units measured by NMR titration. In particular, the TOF becomes almost concentration-independent at low temperatures over a large range of concentrations. This behavior is reminiscent of enzymes, although our catalytic moieties are not fixed in a rigid framework as in proteins. Finally, we also started to synthesize chiral oligomeric chains with a p