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The new model describing the organization of organisms can lead to a better understanding of biological processes



Order of life

The particles of two types (red and blue) interact with each other. While particles of the same type are inevitably subjected to reciprocal attraction or repulsion, particles of the same type may interact unconditionally. Here the green particles chase the red ones. On a large scale, highly compressed bands of blue particles will chase bands of red particles. This creates order and movement in the system. Source: MPIDS / Novak, Saha, Agudo-Canalejo, Golestanian

At first glance, a pack of wolves has nothing to do with a jar of vinegar. However, a team led by Ramin Golestanian, director at the Max Planck Institute of Dynamism and Self-Organizing, has developed a model that establishes a link between predator movement and prey. as well as the separation of the vinegar and oil. They extended a theoretical framework that has so far been valid only for inanimate matter. In addition to predators and prey, other living systems such as enzymes or self-organizing cells can now be described.


The order is not always clear at first sight. If you run with a pack of wolves hunting deer, the movements will appear chaotic. However, if the hunt is observed from the bird̵

7;s eye and over a longer period of time, patterns will become apparent in the animal’s movement. In physics, such behavior is considered orderly. But how does this order emerge? Ramin Golestanian’s Department of Living Matter Physics is dedicated to this question and studies the physical rules that govern motion in living or active systems. The Golestanian’s aim is to reveal the common characteristics of living, active matter. This includes not only larger organisms such as predators and prey but also bacteria, enzymes and motor proteins as well as artificial systems such as microscopic robots. “When we describe a group of systems that operate such for very long distances and long periods of time, the specifics of the system lose importance,” explains Golestanian. them in space become the decisive feature “.

From inanimate to living system

His group at Göttingen recently made a breakthrough in the description of living matter. To achieve this, Suquisya Saha, Jaime Agudo-Canalejo and Ramin Golestanian began with the famous description of the behavior of inanimate matter and expanded it. The main point is to take into account the fundamental difference between living and inanimate matter. In contrast to inanimate, passive, living, active matter can move on its own. Physicists use the Cahn-Hilliard equation to describe how inanimate mixtures such as oil and water emulsions dissociate.

The characteristic model developed in the 1950s is considered the standard model of phase division. It is based on the principle of reciprocity: tit-for-tat. Thus, oil has a water repellent effect like water repels oil. However, this is not always true for living matter or for working systems. A predator chases after its prey, while the prey tries to escape from its prey. Only recently has it been shown that there is incompatible (ie active) behavior even in the movement of the smallest systems such as enzymes. Therefore, enzymes can concentrate specifically in individual cell areas – essential for many biological processes. After this discovery, Göttingen researchers investigated how large accumulation of different enzymes works. Will they combine together or form a group? Will new and unforeseen features arise? With the aim of answering these questions, the team got to work.

The wave suddenly appeared

The first task is to modify the Cahn-Hilliard equation to include non-reciprocal interactions. Because the equations describe non-living systems, the reciprocity of passive interactions is ingrained in its structure. Consequently, all processes described by it end in thermodynamic equilibrium. In other words, all participants eventually entered a state of rest. However, life takes place outside of thermodynamic equilibrium. This is because living systems do not stop at rest but use energy to achieve something (eg regeneration of themselves). Suquisya Saha and her colleagues took this behavior into account by extending the Cahn-Hilliard equation by a characteristic parameter for non-reciprocal activities. In this way, they can now also describe processes that differ to any degree from passive ones.

Saha and her colleagues used computer simulation to study the effects of the included modifications. “Surprisingly, even minimal non-reciprocity leads to radical deviation from the behavior of passive systems,” says Saha. For example, the researcher observed the formation of waves traveling in a mixture of two different types of particles. In this phenomenon, the bands of one element chase the bands of the other, thus creating a moving striped pattern. In addition, complex networks can form in a mixture of particles in which small clusters of one component chase groups of another. With their work, the researchers hope to contribute to scientific progress in both physics and biology. For example, the new model can describe and predict the behavior of different cells, bacteria or enzymes. “We have taught an old dog new tricks with this model,” says Golestanian. “Our research shows that physics contributes to our understanding of biology and the challenges posed by studying living matter have opened up new avenues for fundamental research in matter. physical”.


The mathematician improves the model of the relationship between predators and prey in nature


More information:
Suquiya Saha et al. Mixture of scalar operations: Cahn-Hilliard model without elements, Physical evaluation X (Year 2020). DOI: 10.1103 / PhysRevX.10.041009

Provided by Max Planck Society

Quote: New model describing the organization of organisms that could help better understand biological processes (2020, October 30) retrieved October 30, 2020 from https://phys.org /news/2020-10-biological.html

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