A graphic illustrating the four possible interactions between two particles, showcasing the complex web of forces and interactions present at the molecular level. Credit: R. Dean Astumian
Researchers from the University of Maine and Penn State made a groundbreaking discovery that molecules experience non-reciprocal interactions without the influence of external forces.
Our physical world is largely governed by reciprocal forces such as gravity and electromagnetism. However, daily interactions and phenomena often do not follow this reciprocal law.
Take the relationship between a predator and its prey, for instance. The predator is attracted to the prey, but the prey actively flees from the predator. Such non-reciprocal interactions are fundamental in the complex behaviors exhibited by living organisms. While microscopic systems like bacteria have been thought to be influenced by hydrodynamic or other external forces, the same explanation previously applied to interactions between single molecules.
Published in Chem, UMaine theoretical physicist R. Dean Astumian, along with Ayusman Sen and Niladri Sekhar Mandal at Penn State, have presented a new mechanism by which single molecules can interact non-reciprocally without the influence of hydrodynamic effects.
This mechanism involves the local gradients of reactants and products due to reactions facilitated by chemical catalysts, which can include enzymes in a biological context. This mechanism suggests that due to the properties of catalysts, one molecule can be repelled by, but also attract, another molecule.
This discovery is a critical breakthrough that helps explain the processes by which simple matter evolves into complex structures. Understanding non-reciprocal interactions may play a key role in uncovering the mysteries of molecular transformations.
Earlier efforts to introduce non-reciprocal interactions were focused on incorporating ad hoc forces. However, Astumian, Mandal, and Sen present a fundamental molecular mechanism behind these interactions, building on their earlier work regarding the directional motion of a single catalyst molecule in a concentration gradient using reaction energy. This groundbreaking research is an essential step forward in our understanding of molecular interactions and their influence on complex systems.
