Active Mechanical Threading by a Molecular Motor**

Abstract

Molecular motors transform external energy input into directional motions and offer exquisite precision for nano-scale manipulations. To make full use of molecular motor capacities, their directional motions need to be transmitted and used for powering downstream molecular events. Here we present a macrocyclic molecular motor structure able to perform repetitive molecular threading of a flexible tetraethylene glycol chain through the macrocycle. This mechanical threading event is actively powered by the motor and leads to a direct translation of the unidirectional motor rotation into unidirectional translation motion (chain versus ring). The mechanism of the active mechanical threading is elucidated and the actual threading step is identified as a combined helix inversion and threading event. The established molecular machine function resembles the crucial step of macroscopic weaving or sewing processes and therefore offers a first entry point to a "molecular knitting" counterpart.

Coupled Rotary and Oscillatory Motion in a Second-Generation Molecular Motor Pd Complex

“…19 Lightdriven mechanical threading of a flexible tetraethylene glycol chain through a macrocycle was realized in a hemithioindigobased molecular motor. 20 Similarly, coupling between rotary and reciprocating motion on the nanoscale was demonstrated using a [1]rotaxane whose two components (macrocycle and shaft) were connected to the two halves of a molecular motor (Figure 1D), 21 mimicking a reverse reciprocating engine, powered not by the reciprocating but by the rotary motion. An earlier example used a stiff-stilbene 22 co-workers by demonstrating active and unidirectional acceleration of biaryl rotation using a molecular motor (Figure 1E).…”

“…A study on a different second-generation motor featuring an extended aromatic core revealed a helix inversion coupled to its rotation as a byproduct of the steric clash in the newly introduced extended lower half (Figure C) . Light-driven mechanical threading of a flexible tetraethylene glycol chain through a macrocycle was realized in a hemithioindigo-based molecular motor . Similarly, coupling between rotary and reciprocating motion on the nanoscale was demonstrated using a [1]­rotaxane whose two components (macrocycle and shaft) were connected to the two halves of a molecular motor (Figure D), mimicking a reverse reciprocating engine, powered not by the reciprocating but by the rotary motion.…”