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Interactions between molecules that are not equal and opposite, a seeming violation of Newton’s third law of motion, can occur naturally according to new research. A kinase enzyme adds a chemical modification to other molecules, resulting in a phosphorylated protein. Phosphatase enzymes remove the modifications, such that the kinases create products that are acted upon by phosphatases and vice versa. Researchers demonstrated that the kinase is attracted to the phosphatase, but the phosphatase is repelled by the kinase, in what is called a non-reciprocal interaction. Illustration Credit: Niladri Sekhar Mandal / Pennsylvania State University (CC BY-NC-ND 4.0 DEED) |
It turns out that every action may not have an equal and opposite reaction, despite what Newton’s third law of motion says, according to new research conducted by a team from Penn State and the University of Maine. The finding could offer insight into how certain molecular interactions could have evolved in a pre-life world.
The work was published in the journal Chem, and the researchers said this is the first demonstration of the mechanism by which these interactions occur at the molecular level. Last year’s discovery by researchers at Kyoto University that sperm movement does not cause an opposite reaction in its environment as it moves provided an example of a seeming violation of Newton’s third law of motion, but it did not address the mechanism.
“We all have heard the phrase ‘every action has an equal and opposite reaction,’ to describe Newton’s third law of motion, but we see examples that seemingly violate this every day, especially in the behavior of complex living systems small and large where there is constant input of energy,” said Ayusman Sen, Verne M. Willaman Professor of Chemistry in the Eberly College of Science at Penn State and one of the research team leaders. “An example at the larger scale is that a predator is attracted to its prey, but the prey is repelled by the predator. This type of interaction is called non-reciprocal, and we were interested to see if it also occurred in the much simpler interactions among molecules with constant energy input.”