Physicist defends Stokes-Einstein’s validity

Photo: Young Wang, University of Arkansas
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Credit: University of Arkansas

A physicist at the University of Arkansas has defended the validity of the Stokes-Einstein equation, one of Albert Einstein’s most famous equations, as it relates to biology. The research will help scientists better understand antibiotic resistance and the mechanical properties of cancer cells.

Working with proteins in living bacteria, Yong Wang, an assistant professor at the Fulbright School of Arts and Sciences, tested the 117-year-old equation, which provided evidence of the truth about atoms and molecules. He found that the famous equation remained valid to explain how molecules move within bacteria.

“Bacterial cytoplasm is not a simple soup,” Wang said. “Our study showed that it might be more like spaghetti with tomato sauce and meatballs.”

Cytoplasm is a crowded, complex substance within bacteria. It contains high concentrations of large biological molecules, including millions of proteins, carbohydrates, salts, and all kinds of polymers and strands, such as DNA and RNA.

Wang found that although Einstein’s equation seemed to hold up for the movement of proteins within living bacteria, it remained valid by taking into account the polymers and interlocking filaments within the bacteria.

The so-called Einstein relationship – also called the Stokes-Einstein equation – is one of the major research achievements of Albert Einstein in “The Year of Miracles”, 1905. Explaining the motion of particles through a liquid, the equation is described as a stochastic model. of Brownian motion, which means that particles move randomly due to collisions with surrounding particles. Importantly, the theory provided early empirical evidence for the reality of atoms and molecules.

However, over the past two decades, scientists have challenged the theory’s validity as it applies to what’s inside living cells and bacteria. Wang’s study adds to this body of knowledge, helping to resolve the current controversy.

More importantly, it provides a basis for evaluating the mechanical properties of cells and bacteria based on Einstein’s relationship. This should help scientists understand the antibiotic resistance of some microorganisms and the mechanical properties of cancer cells, which are different from the mechanical properties of healthy and normal cells.

In this study, which was published in physical review messagesWang worked with Lin Oliver, professor and chair of the physics department, and Asma Saadoun, a doctoral student in the Microelectronics and Photonics program.


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