Presentation: Molecular Ratchets
- The interesting stuff is far from equilibrium – how do we build systems that get there? Flagella, ATP synthase, and dynein are natural molecular machines which use various levels of rotational motion and operate far from equilibrium. With enough effort we should be able to copy and surpass these natural machines.
- To build a molecular motor we need to use energy to repetitively and progressively drive a system away from equilibrium. They must be directionally biased, repetitive, progressive, processive (multiple steps without dissociating), and ideally autonomously. The difficulty of creating motors at the nanoscale is that everything is subjected to Brownian motion and forces of viscosity, rather than simpler forces like gravity and momentum.
- Stefan is harnessing catalysts to drive reactions in one direction, simultaneously driving a molecular motor against equilibrium. Hydration of carbodiimide is an example of one such reaction. Experimenting with different fuels and barriers allows tuning of the force, speed, and efficiency of the motor.
- Stefan’s lab asked a question – can we take all this information and build an autonomous rotary motor? They used two carbon rings with carboxylic acid functional groups, along with a modular functional group, to build a simple rotary motor. By selectively forming and dissociating anhydrides, the rotor spins in a single direction.
Stefan hopes that people find applications of nonequilibrium machines, figure out how to get them to interface with other components, and copy biological designs when pursuing molecular motors.