ABSTRACT
The limits of self-assembly and host-guest chemistry in water solutions containing competitive solutes are largely unexplored. We report here a new family of self-assembling systems that are stitched together at two levels by reversible hydrazone bonds and by non-covalent self-assembly in strongly denaturing conditions. Three different hydrazides of various charge and hydrophobicity are combined with an aldehyde-containing calixarene, and each system spontaneously forms AB hydrazones that subsequently self-assemble into four-component (AB)2 structures in water. The assemblies display varying responses to added NaCl and/or urea. The most robust assembly survives completely intact in solution up to 5 M urea. We also combine the aldehyde calixarene with two different hydrazides in the same tube to create complex, competitive dynamic libraries. We report experiments in which the composition of the dynamic equilibrating library is under the control of self-assembly, allowing the systems to choose the components that form the most stable assemblies under a variety of competitive solutions conditions. These dynamic networks of equilibrating molecules maintain remarkably similar equilibrium positions under widely varying concentrations of urea and NaCl.
ABSTRACT
Many indicator displacement assays can detect biological analytes in water, but these often have reduced performance in the presence of an unavoidable component: NaCl. We report here a new self-assembled sensor, DimerDye, that uses a novel photochemical guest-sensing mechanism and that is intrinsically tolerant of cosolutes. We synthetically integrated a dye into a calixarene macrocycle, forming two new merocyanine calixarenes (MCx-1 and MCx-2). Both compounds self-assemble into nonemissive dimers in water. The addition of good guests like trimethyllysine induces a turn-on fluorescence response of MCx-1 due to simultaneous dimer dissociation and formation of an emissive host-guest complex. DimerDyes remain functional in solutions containing the various salts, metal ions, and cofactors that are needed for enzymatic reactions. MCx-1 provides a real-time, turn-on fluorescence signal in response to the lysine methyltransferase reaction of PRDM9.
