In a groundbreaking study, researchers from the University of Maine and Penn State have uncovered a new mechanism by which molecules can experience non-reciprocal interactions without the presence of external forces. This discovery challenges the traditional understanding of fundamental forces such as gravity and electromagnetism, which are considered to be reciprocal. The findings shed light on the complex behavior observed in living organisms and could have significant implications for our understanding of the evolution of life.
Non-reciprocal interactions refer to situations where two objects or entities do not exhibit a mutual gravitational or electromagnetic attraction or repulsion. This phenomenon is commonly observed in nature, particularly in predator-prey relationships, where predators are attracted to prey, but the prey instinctively attempts to flee. Understanding the underlying mechanisms of these non-reciprocal interactions is crucial for comprehending the intricacies of living systems.
Previously, non-reciprocal interactions in microscopic systems, such as bacteria, were attributed to external forces, such as hydrodynamics. However, the recent study published in Chem by the UMaine theoretical physicist R. Dean Astumian and collaborators Ayusman Sen and Niladri Sekhar Mandal at Penn State presents a new perspective. Their research proposes that non-reciprocal interactions at the molecular level can occur without the need for hydrodynamic effects.
The researchers argue that the non-reciprocal interactions between single molecules can be explained by invoking the local gradients of reactants and products resulting from chemical reactions facilitated by catalysts, such as enzymes. They discovered that the kinetic asymmetry, a property inherent in catalysts, controls the direction of response to a concentration gradient. This means that one molecule can be repelled by another molecule while simultaneously attracting a different molecule.
The significance of this research extends beyond molecular interactions. Non-reciprocal interactions are instrumental in the formation of complex behavior in living organisms and have been extensively studied under the umbrella of “active matter.” However, previous studies relied on the introduction of ad hoc forces to create non-reciprocal interactions. The research conducted by Mandal, Sen, and Astumian provides a fundamental molecular mechanism by which non-reciprocal interactions arise naturally between single molecules.
The identification of kinetic asymmetry as a key determinant of non-reciprocal interactions has wider implications. This property not only influences the directionality of biomolecular machines but has also been integrated into the design of synthetic molecular motors and pumps. Therefore, the collaboration between Astumian, Sen, and Mandal not only advances our understanding of non-reciprocal interactions but also holds promise for unraveling the organizational principles behind the earliest metabolic structures that eventually led to the evolution of life.
The discovery of a new mechanism for non-reciprocal interactions among molecules opens up a fascinating realm of possibilities in our understanding of complex behavior in living systems. By uncovering the role of kinetic asymmetry in controlling the directionality of these interactions, researchers have laid the foundations for future investigations into the evolution of life from simple molecules. With further exploration, this breakthrough could revolutionize our understanding of fundamental forces and reshape our perspective on how life emerged on Earth.