Colleagues at Philips University of Marburg and the Max Planck Institute working here were the first to discover a natural molecular fractal. According to the evolutionary biochemical interpretation based on electron microscopy, fractals were created primarily by chance during evolutionary development.
Fractals are infinitely complex geometric shapes that retain their shape even if we zoom in and out by changing the scale. This concept is named after Benoit B. Mandelbrot, French-American mathematician of Polish descent. In addition to the famous Mandelbrot set, a famous fractal is also a triangle discovered by another Polish mathematician, Waclaw Sierpinski, which was created by placing a triangle at the midpoints of the sides of a regular triangle and repeating it further in smaller triangles. Formed at the peaks.
For simplicity, we have included a fractal animation – we also recommend it to those who are professionally affected by the nerve-wracking sounds used during coercive interrogations, otherwise they should be rejected.
The molecule discovered by the German researchers is a fairly common enzyme, citrate synthase from cyanobacteria. Citrate synthase is the molecule that catalyzes the first reaction of the citric acid cycle, which produces citrate.
The citric acid cycle is also called the Krebs cycle or Sint-György-Krebs cycle, since most of the molecular components of the cycle were identified by Albert Sint-György in the 1930s. Sint-György was awarded the Nobel Prize in Medicine in 1937 for his discovery of vitamin C and for deciphering the catalytic role of fumaric acid – if you were wondering what the latter is, you can now find out that it is part of this biochemical process and is used to release stored energy. But back to fractals.
Not all vessels are fractals
Fractal structures are common in nature, seen in cauliflower and many other plants, or in the structure of snowflakes. However, the true fractal characteristic is the fact that the shape of the large structure is the same as its parts. It's so rare that we don't even know about it at a molecular level yet.
As it turned out, citrate synthase spontaneously assembles into the Sierpinski triangle.
We found the structure completely by chance and couldn't believe our eyes when we saw the first electron microscope images
– says Franziska Sendker.
The protein forms these beautiful triangles, and as the fractal grows, there is a larger and larger triangular cavity in the middle. It is completely different from any protein organization we have ever seen
he added.
Understanding the structure's composition was not an easy task either, as the researchers said the imaging algorithm was also confused by the repeated triangles, and tried to automatically zoom in on the image.
Proteins are composed of complexly folded chains of amino acids, but these chains are symmetrical. Adjacent strands take a similar shape, but on a larger scale create a seamless shape. The fractional protein had no such symmetry, and the individual chains were attached to each other at different locations, thus creating a Sierpinski triangle with holes in the middle.
In nature, proteins are assembled by other proteins, and the question is whether there is any benefit from the fact that a protein can assemble itself into a fractal. Scientists manipulated the bacteria so that citrate synthase could not form larger triangles, and found that the organisms
They live happily even without fractals.
Biochemical investigation also revealed that this type of fractal appeared with different mutations and then disappeared in the generations of cyanobacteria, remaining only in one bacterial family. Fractals, both in the individual case and in phylogeny, are more a strange coincidence than a useful feature.
According to the researchers, all this indicates that the complexity of biological molecules still holds many surprises for us.
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