Saturday, July 5, 2008

Carp Crystals

Credit: M.C. Stevens,

A Japanese Koi fish.

Make Cosmetic Reflections

Credit: American Chemical Society

The SEM micrographs of isolated biogenic crystals from carp's skin (left) and from in-vitro grown guanine (right).

Cosmetics Meets Fish at The European Synchrotron Radiation Facility (ESRF)

ESRF is the result of unwanted side effects of CERN. It is nothing but an extremely focused hard X-ray source. Scientists put all sorts of things in front of the X-ray, using various techniques making the most incredible discoveries. A group of scientists have studied the shell of carp fish to find out how and why they shine (reflect light), just like we want some of the cosmetics to behave.

"The carp's crystals (shell) are thin plates orientated in such a way that the face of the crystal, which is also the one containing hydrogen-bonded network of guanine molecules, is exposed to the light. It is known that the in-plane molecular polarisability - and, with it, the light reflectivity - of guanine molecules is higher in the plane of the molecule than it is perpendicular to it. On the other hand, in vitro crystals are much thicker and irregular in shape. These results were unexpected and differ from theoretical predictions.

The outcome of this research shows that natural phenomena like the growth of crystals on the skin of fish have a reason behind them. "Fish invest energy in inhibiting crystal growth in the fast growing direction. This allows them to have the best possible optical properties for reflection", explains Levy-Lior."

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