Dynamic Devices. Shape Switching and Substrate Binding in Ion-Controlled Nanomechanical Molecular Tweezers

Abstract

As examples of supramolecular devices performing chemical (ionic, molecular) control of binding events and models of related natural systems, two molecular conformational switches are described, which display cation-controlled nanomechanical motion coupled to substrate binding and release. The substrate binding relies on donor/acceptor interactions, provided by intercalation between planar sites located at the extremities of the switching units, whereas cation complexation is responsible for conformational regulation. The terpyridine py-py-py-based receptor is activated toward substrate binding upon complexation of a zinc(II) cation and operates in a two-state process. The replacement of the central pyridine by a 4,6-disubstituted pyridimine as in py-pym-py induces a state reversal and yields a new receptor which binds a substrate in the absence of cation, and releases it when copper(I) is introduced, following a three-step process. These systems represent effector-triggered supramolecular switching devices leading toward multistate nanomechanical chemical systems. These two systems illustrate the use of simple conformational switches in the binding site and allosteric regulation of substrate affinity.

Telomere Targeting with a New G4 Ligand Enhances Radiation-Induced Killing of Human Glioblastoma Cells

“…Owing to the propensity of the py-pym-py spacer to fold in a U-shaped conformation, TAC-Me2 may possibly adopt a tweezertype conformation in water (Fig. 1B), similar to that observed for the uncharged and monomethylated analogues in the solid state and in organic solvents (20). Interestingly, tweezer-type molecules holding 2 potentially intercalating units 7 A apart have a moderate affinity for duplex DNA based on the neighbor exclusion principle (21,22), which excludes bis-intercalation between contiguous base pairs.…”

“…1D) indicate that this compound has a preference for quadruplex structures. These experiments compare the amount of dye bound to a variety of structures (typically [12][13][14][15][16][17][18][19][20], each trapped in a small dialysis chamber immerged in a large bath containing 1 mmol/L TAC. Binding to the 2 quadruplex samples [22AG and 24G20, corresponding to the human telomeric motif [A(GGGTTA) 3 GGG] and T 2 G 20 T 2 sequence, respectively] was stronger than that for duplexes and DNA and RNA single strands [poly(rA), poly(rU), poly(dT), and poly(dU)] or i-motifs (formed with C-rich sequences).…”

Synthesis and Self‐Aggregation of Enantiopure and Racemic Molecular Tweezers Based on the Bicyclo[3.3.1]nonane Framework

“…Molecular tweezers can in principle be divided into three groups: semirigid, [6][7][8][9][10][11][12][13] conformationally labile, [2,[14][15][16][17][18][19][20] and conformationally controlled by hydrogen bonds or metal chelation. [21][22][23] The interaction that mediates the recognition process can, in addition to London dispersion forces, be based on hydrogen-bonding, [24] charge-transfer, [14] ion-p, [8,25] p-p, [1] electrostatic, [8] and coupled interactions. [26] Most common are molecular tweezers with high symmetry, but there are some chiral examples.…”

Nanoscale process systems engineering: Toward molecular factories, synthetic cells, and adaptive devices

“…Electrochemistry (e.g., molecular switch with differing cation-and anion-interaction behavior 71 ; ion-controlled molecular tweezers 72 ; electrochemically-induced rotaxane switch 46 ). 5.…”