Selective binding of choline by a phosphate-coordination-based triple helicate featuring an aromatic box

Abstract

In nature, proteins have evolved sophisticated cavities tailored for capturing target guests selectively among competitors of similar size, shape, and charge. The fundamental principles guiding the molecular recognition, such as self-assembly and complementarity, have inspired the development of biomimetic receptors. In the current work, we report a self-assembled triple anion helicate (host 2) featuring a cavity resembling that of the choline-binding protein ChoX, as revealed by crystal and density functional theory (DFT)-optimized structures, which binds choline in a unique dual-site-binding mode. This similarity in structure leads to a similarly high selectivity of host 2 for choline over its derivatives, as demonstrated by the NMR and fluorescence competition experiments. Furthermore, host 2 is able to act as a fluorescence displacement sensor for discriminating choline, acetylcholine, l-carnitine, and glycine betaine effectively.

Coordination cages as permanently porous ionic liquids

“…Future work will target the preparation of permanently porous liquids with still larger cavities, capable of binding more complex molecules as guests. While to the best of our knowledge coordination cages have not been previously used as scaffolds for porous liquids, supramolecular capsules have been constructed with a range of different sizes, geometries, and guest-binding preferences [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] . By using coordination cages to build the cavities within porous liquids, we envisage new fluids with pores selected from the extensive library of existing coordination cages [41][42][43] .…”

Peripheral Templation‐Modulated Interconversion between an A4L6 Tetrahedral Anion Cage and A2L3 Triple Helicate with Guest Capture/Release

“…To get more details of the templating properties of TMA to the T conformer, [TBA] 6 [(PO 4 ) 2 L 3 ] (TBA=tetrabutylammonium) was synthesized, wherein the big size of the countercation excluded their templation effect either in the central cavity or at peripheral grooves . The 1 H NMR spectrum of [TBA] 6 [(PO 4 ) 2 L 3 ] showed only one set of signals corresponding to the helicate H structure (Figure a), which was further confirmed by HRMS ([ L 3 (PO 4 ) 2 (TBA) 2 H] 3− , obsd.…”

“…Subsequently, some biologically important species, namely, choline and its derivatives (choline=Ch, acetylcholine=Ach, l ‐carnitine=LC, and glycine betaine=GB), which are quite similar to TMA as quaternary ammonium cations, were tested as potential guests. After separately adding one equiv of the guests (relative to the T ), to a solution of the T (TM‐C6), both Ch and ACh induced pronounced broaden of the aromatic H1 (Figure a,b) and a sharp singlet at 0.54 ppm (Δ δ =−2.86 ppm for Ch and Δ δ =−2.92 ppm for ACh), which is typical evidence of the deep encapsulated “Me 3 N‐ + ” head . In contrast, no binding of LC and GB was observed.…”

“…In our recent work, selective encapsulation of biomolecules (e.g. choline) or highly reactive species (P 4 , As 4 ) was achieved by an A 2 L 3 (A=anion, L=ligand) triple helicate cage, or A 4 L 4 face‐based tetrahedral cages –. Though these assemblies displayed instant assembling/disassembling behaviors under mild conditions, no supramolecular transformations have been observed yet.…”

Construction and interconversion of anion-coordination-based (‘aniono’) grids and double helicates modulated by counter-cations

“…In the pursuit of more complex anion-based systems, we move forward from the bis–bis(urea)17 to the bis–tris(urea) unit 18. The tris(urea) subunit exhibits stronger coordination affinity than the bis(urea) and forms stable A L 2 phosphate complexes with binding constants even comparable to those of some metal complexes 18 a .…”