Sea urchins breed crystals

How the surface determines the properties of crystals

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Over their surface, crystals communicate with their environment. In ancient monuments this is clearly visible in a veritable "loss of face", which is triggered by moisture and other factors. But minerals are not only destroyed by the surrounding substances: The environment can also control the structure of a crystal. For example, sea urchins breed their spines of self-assemble crystals in the form that is advantageous for them. This is reported by mineralogists in the scientific journal RUBIN Geowissenschaften of the Ruhr-Universit├Ąt Bochum.

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What actually happens exactly when the ravages of time gnaw at stone surfaces, is only known since modern microscopes allow insight into the dissolution processes in detail. If one observes such a process, for example by means of atomic force microscopy, one discovers that the weathering proceeds through ordered processes on the crystal surface. Water molecules settle on the surface and form a closed layer at high humidity.

The oxygen atoms of the water complement the crystal surface, they settle in "gaps". As a result, they release individual crystal molecules from the composite - small pits are formed, which in turn are the target for water molecules.

Sting is cut out of the crystal lattice

This communication of the crystal surface with its environment does not necessarily mean the dissolution, but can also influence the structure of a crystal. display

For example, sea urchins breed their skeletons and their spines in a targeted way by only growing crystals in a specific way. Proteins in the cell fluid wet the surface of the growing seed and ensure that the crystal does not grow rhombohedral, as it would without interference, but that the new atoms attach only in the desired direction.

Proteins control processes

So a sea urchin spine is practically cut out of the natural crystal lattice. Which proteins are responsible for the control processes is the subject of further research. However, initial experiments with simple amino acids have proven that targeted crystal growth is possible.

Scientists also suspect the origin of life in the communication between the surface of the crystal and its surroundings: attached to a crystal surface, the organic components of life could have come so close for the first time that they could make connections.

(idw - Ruhr-University Bochum, 16.05.2007 - DLO)