Do biological molecular machines maximise performance by harnessing ‘demonic’ powers? Matt Leighton, a physicist at Yale University in New Haven, Connecticut, speculates on this intriguing possibility in a thread on X/Twitter about his recent preprint with FQxI physicist John Bechhoefer, of Simon Fraser University in Burnaby, British Columbia, and colleagues.
Bechhoefer was awarded a grant in FQxI's "Information as Fuel" round to create a mini-engine, from a microbead suspended in a fluid. Thermal fluctuations would usually just jiggle the bead at random, but the team was able to set the system up to cannily exploit these natural jostles to do useful work. In this way, they created a mini 'Maxwell’s demon' engine–an engine that extracted work from information about the environment. You can read more about their project in Colin Stuart’s article, "Good Vibrations."
In their new FQxI-funded paper, Leighton, Bechhoefer and colleagues investigated whether real-world molecular machines might be performing a similar trick. “The inside of the cell, where these machines operate, is a storm of powerful fluctuations,” Leighton wrote on X/Twitter. “A Maxwell demon can leverage these fluctuations to enhance its performance, instead of just fighting against them.”
The team created a new statistical estimator to detect “demonic” behavior by measuring mean squared displacements in and out of equilibrium. Specifically, they studied the molecular machine kinesin, and found that it becomes “increasingly demonic as the strength of (nonequilibrium) fluctuations in its environment goes up,” Leighton wrote. “This transition to operating as a Maxwell Demon coincides with an increase in velocity!”
Image depicts an artist's impression of kinesin moving across microtubules, by Kateryna Kon.