March 5, 2024

New Study Discovers Molecules Exhibiting Non-reciprocal Interactions Without External Forces

In a recent study conducted by researchers from the University of Maine and Penn State, it has been found that molecules can experience non-reciprocal interactions even without the presence of external forces. This discovery challenges the belief that interactions between individual molecules can only be explained by external factors such as hydrodynamic forces.

However, everyday experiences often involve interactions that do not follow this reciprocal law. For instance, predators are attracted to prey, but the prey tend to flee from the predator. Such non-reciprocal interactions are crucial for complex behavior observed in living organisms.

Previous understanding of non-reciprocal interactions in microscopic systems, such as bacteria, revolved around the influence of hydrodynamic forces or other external factors. It was believed that a similar explanation could be applied to interactions between single molecules.

However, the research published in Chem presents a new mechanism that explains how single molecules can interact non-reciprocally without the involvement of hydrodynamic effects. According to the study, this mechanism relies on the local gradients of reactants and products created by chemical catalysts, such as enzymes. These catalysts exhibit a property called kinetic asymmetry, which determines their response to concentration gradients. As a result, one molecule can be repelled by, while another molecule is attracted to, the same catalyst.

The researchers had a breakthrough moment when they realized that this kinetic asymmetry, inherent to catalysts, controls the direction of their response to concentration gradients. This property, being subject to evolution and adaptation, plays a significant role in non-reciprocal interactions between molecules and may have contributed to the complexification of matter.

While previous studies on non-reciprocal interactions focused on the incorporation of ad hoc forces, this research by Mandal, Sen, and Astumian reveals a fundamental molecular mechanism that gives rise to such interactions between single molecules. The findings build upon their earlier work, which demonstrated how a catalyst molecule could utilize the energy from a reaction to undergo directional motion in a concentration gradient.

The significance of kinetic asymmetry in determining non-reciprocal interactions extends beyond this study. It has also been identified as a crucial factor in the directionality of biomolecular machines and has been utilized in the design of synthetic molecular motors and pumps.

The collaboration between Astumian, Sen, and Mandal aims to uncover the organizational principles behind the formation of loose associations between different catalysts. These associations may have played a crucial role in the development of early metabolic structures, ultimately leading to the evolution of life.

Astumian sees the understanding of kinetic asymmetry as a potential opportunity to unravel the evolutionary processes that transformed simple molecules into life. Beyond that, this knowledge can be applied to the design of molecular machines and associated technologies, opening up new possibilities for advancements in various fields. Although this research is still in its early stages, it holds promise for gaining insights into the complexification of matter and harnessing kinetic asymmetry for practical applications.

1. Source: Coherent Market Insights, Public sources, Desk research
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