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Researchers find that the equilibrium of living cells is unsteady

April 29th, 2016

Windmill — Any system in thermodynamic equilibrium is known to satisfy perfectly balanced forward and backward transitions between any two states. As famously shown by Richard Feynman in the 1960s, one important consequence of this is that it is impossible to power a motor using only thermal molecular motion. This research shows how living systems violate this principle. Thus, even stochastic fluctuations in such living systems could be used to drive a small-scale windmill, as shown. Credit: C. Hohmann, Nanosystems Initiative Munich (NIM) and M. Leunissen, Dutch Data Design.

An international team of researchers has found a way to investigate equilibrium, or the lack thereof, in cells and other living systems. They discovered that cells violate the fundamental principle of detailed balance, which is satisfied by all systems in thermodynamic equilibrium and is characterized by equal rates of forward and backward reactions between any two states of a system. The research team published their method and results in Science on 29 April 2016.

Equilibrium is a very fundamental issue that is, quite literally, a matter of life and death. Scientists have long recognized that living systems must avoid thermodynamic equilibrium. In fact, the lack of such equilibrium constitutes a key characteristic distinguishing animate from inanimate matter. After all, living systems constantly burn energy to stay alive. This consumption of energy keeps them from equilibirum, and from death. General methods to investigate the lack of equilibrium in living systems, however, have been sparse.

Researchers from Amsterdam, Goettingen, MIT, Munich and Yale have developed a method that relies only on commonly available microscopy methods and detailed statistical analysis. This allowed them to identify what keeps cells from reaching equilibrium. Importantly, their approach is non-invasive and can be used on a variety of living systems.

Detailed balance

For more than a hundred years, chemists and physicists have known that all equilibrium systems satisfy the principle of detailed balance. Detailed balance means that there are equal rates of forward and backward reactions between any two states of the system: each process is equilibrated with its reverse process. Living systems violate this principle at the molecular scale, for instance through metabolic processes that are cyclical in nature and consume energy. However, whether this is also manifest on the larger scale of cells or tissues has remained hotly debated.

The research team has now demonstrated that detailed balance is also broken at a scale greater than the molecular scale: the micrometer scale of individual cells. Specifically, they showed that the seemingly random motion of hair-like cellular protrusions of kidney cells is in fact cyclical.

Broad impact

FOM workgroup leader Fred MacKintosh (VU) is excited about the results: "This work will not only be of interest for applications to biology, but will also for the statistical mechanics and biophysics communities, because it addresses the very basic question of whether and how the lack of molecular-scale equilibrium is manifest at larger scales."

More information:
Broken detailed balance at mesoscopic scales in active biological systems, Battle, C., Broedersz, C.P., Fakhri, N., Geyer, V.F., Howard, J., Schmidt, C.F.,, MacKintosh, F.C., Science, 29 April 2016. DOI: 10.1126/science.aac8167

Provided by Fundamental Research on Matter (FOM)

Citation: Researchers find that the equilibrium of living cells is unsteady (2016, April 29) retrieved 16 June 2025 from https://sciencex.com/wire-news/223365855/researchers-find-that-the-equilibrium-of-living-cells-is-unstead.html

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