An Autonomous Bipedal Walking Device

The walking device consists of a strand of DNA that contains a 5,5 linkage in the middle.  One leg is called L-E and the other is called L-O.  It walks on a track consisting of a series of stem-loops (T1-T4) that are part of a stiff DX motif.  It is fueled by a pair of successive stem-loops (F1 and F2) that are in solution.  The driving force for its motion is the formation of more base pairs than exist at any given time.  The system is shown below.

A single step of the walker, fuelled by F1 is shown below.  L-O is attached to T1 and L-E is attached to the right side of T2.  At state 1, F1 interacts with the left side of T2, which has been freed by the binding of L-E to the right side of T2.  In stage 2, T2 invades F1.  In stage 3, F1 is split by T2, and in stage 4, F1 invades T1.  This frees L-O (stage 5), which can diffuse to T3 (stage 6).  It then invades T3, (stage 7), and T3 is split so that its left side can attack F2.  The cycle repeats with F2, and then it is free to repeat with F1 again.

The image below shows how this is a burned-bridges mechanism for motion.  The track is used up by the addition of successive fuel molecules.  Resting state 1 is converted stepwise to resting state 4 by the successive binding of three fuel molecules to the track, while the walker moves from T1 to T4.

 

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