Violation of Newton’s third law of motion discovered

Mechanics

Editorial of the Technological Innovation Website – 03/28/2024

Newton’s third law of motion

If you were surprised by two discoveries announced this month, one revealing an exception to the law that governs heat transfer and another that showed that particles with the same charge can attract each other, get ready for yet another twist in the well-known laws of physics.

It turns out that not every action can have an equal and opposite reaction, as Newton’s third law of motion says. Last year, a team from Kyoto University in Japan discovered that the movement of sperm does not cause an opposite reaction in its environment as reproductive cells move, in an apparent violation of the law of action and reaction.

Niladri Mandal and colleagues from the universities of Pennsylvania and Maine, in the USA, have now managed to unravel the mechanism behind this reactionless movement.

Mandal studied two enzymes – molecules that catalyze biochemical reactions – called kinases and phosphatases. Kinases add a chemical modification to other molecules, while phosphatases remove modifications from molecules. Thus, kinases create products that are influenced by phosphatases and vice versa.

Experiments have shown that if the phosphatase is artificially immobilized, the kinase will be attracted to it. However, in the opposite situation, in which the kinase is immobilized, the phosphatase is repelled by it. Clearly, it is an action that does not have an equal and opposite reaction.

“The non-reciprocity we see is not due to any external forces, but results from a combination of diffusion and kinetic asymmetries, which are properties of enzymes,” detailed the researcher. A kinetic asymmetry describes the relative heights of the energy barriers that control the direction of a reaction with respect to a concentration gradient – in this case, of enzymes as they move through a molecular system.

Implications for machines and life

Asymmetric interactions between these enzymes not only help elucidate the movement of molecules within cells, but can also help design synthetic molecular motors and pumps – the movement of sperm is an example of a natural molecular motor in action, which nanotechnology has been trying to achieve. reproduce.

“Not only can this provide information about the complexification of matter, but kinetic asymmetry can also be used in the design of molecular machines and associated technologies,” said team member Dean Astumian.

Most importantly, the discovery of this reactionless action may help explain the emergence of life itself.

“We are in the early stages of this work, but I see understanding kinetic asymmetry as a possible opportunity to understand how life evolved from simple molecules,” said Astumian.

“The non-reciprocal interactions allowed by kinetic asymmetry also play a crucial role in allowing molecules to interact with each other. This may have played a critical role in the processes by which simple matter becomes complex, interacting in ways that eventually led to life . As kinetic asymmetry is a property of the enzyme itself, it can undergo evolution and adaptation,” added Professor Ayusman Sen.

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