Transducing chemical energy through catalysis by an artificial molecular motor

24 May 2024, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Cells display a range of mechanical activities enabled by the cytoskeleton, a viscoelastic hydrogel manipulated by motor proteins powered through catalysis. This raises the question of how the acceleration of a chemical reaction can enable the energy released from that reaction to be transduced, and thereby work to be done, by a molecular catalyst. Here we demonstrate the molecular-level transduction of chemical energy to mechanical force in the form of the powered contraction and powered re-expansion of a crosslinked polymer gel driven by the directional rotation of embedded artificial catalysis-driven molecular motors. Continuous 360° rotation of the rotor about the stator of motor-molecules incorporated within the polymeric framework of the gel, twists the polymer chains of the crosslinked network around one another (either clockwise or anti-clockwise, depending on the chirality of the fuelling system). This progressively increases writhe and tightens entanglements, causing macroscopic contraction of the gel to ~70% of its original volume. The limit of contraction corresponds to the stall force of the motor; the point at which, despite catalysis continuing, the untwisting force exerted by the entwined strands balances conformation selection in the motor’s catalytic cycle. Subsequent addition of the opposite enantiomeric fuelling system powers rotation of the motor-molecules of the contracted gel in the reverse direction, unwinding the entanglements and causing the gel to re-expand. Continued powered twisting of the strands in the new direction causes the gel to contract once again. The experimental demonstration of work against a load by a synthetic catalyst, and the mechanism of the transduction of energy by a catalyst through kinetic asymmetry in its acceleration of a fuel-to-waste reaction, informs both the debate surrounding the mechanism of force generation by biological motors and the design principles for artificial molecular nanotechnology.

Keywords

molecular motors
energy transduction
dissipative systems
chemical fuels

Supplementary materials

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SI Experimental procedures & characterisation data
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Experimental procedures & characterisation data
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Supplementary Video S1
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Close up video of first 20 h fuelled contraction of gel-1 with (S,S)-2 and (S)-4
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Supplementary Video S2
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Full video (0-160 h) of fuelled contraction of gel-1 with (S,S)-2 and (S)-4
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Supplementary Video S3
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Close up video of first 20 h fuelled contraction of gel-1 with (R,R)-2 and (R)-4
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Supplementary Video S4
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Full video (0-160 h) of fuelled contraction of gel-1 with (R,R)-2 and (R)-4
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Supplementary Video S5
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Treatment of gel-1 with achiral fuel DIC and DMAP
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Supplementary Video S6
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Treatment of control gel-1-Me2 with (S,S)-2 and (S)-4
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Supplementary Video S7
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Close up video of first 20 h fuelled expansion–contraction experiment
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Supplementary Video S8
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Full video (0-100 h) of fuelled expansion–contraction experiment, pre-contracted gel ((S,S)-2 and (S)-4) treated with (R,R)-2 and (R)-4
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Supplementary Video S9
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Expansion–contraction control, pre-contracted gel ((S,S)-2 and (S)-4) treated with achiral DIC and DMAP
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