In "Lobster colour has quantum cause," Nature writes that Dutch researchers have found why lobsters change colors when they are cooked. According to Nature, "a lobster's colour is due to a pigment molecule called astaxanthin, which is attached to a protein called crustacyanin." The Dutch team, using nuclear magnetic resonance spectroscopy and computer simulations, showed that these astaxanthin molecules, grouped in pairs, are interfering with one another. As a result, it shifts their quantum energy states, altering the wavelength of light they can absorb, thus turning black when cooked. The article doesn't say how many lobsters the researchers used -- and ate -- for their experiments, but read more...
First, Nature describes the problem -- or the situation.
Chemists know that a lobster's colour is due to a pigment molecule called astaxanthin, which is attached to a protein called crustacyanin. Astaxanthin is one of the carotenoid pigments responsible for the bright red colours of many animals and plants, including those of oranges, tomatoes and some birds' feathers.
When a lobster is boiled, its crustacyanin proteins unwind in the heat and the astaxanthin pigment falls off. This 'free' astaxanthin is red, just like most other carotenoids, and gives the lobster its freshly-cooked colour. But chemists were mystified as to why live lobsters are blue-black.
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Before going further, here is a picture of a common lobster -- red before being cooked (Credit: National Oceanic and Atmospheric Administration, via Wikipedia). |
Then, Nature describes the Dutch team's experiments.
The team followed up on the discovery in 2002 that astaxanthin molecules in the crustacyanin proteins are grouped in pairs that cross each other in an X-shape.
This pairing, the researchers' calculations show, means that the two molecules interfere with one another, like cross-talk between electrical signals in neighbouring wires, and this shifts their quantum energy states. That in turn alters the wavelength of light that they absorb, accounting for most of the blackness.
And here is the conclusion of Francesco Buda of Leiden University in the Netherlands, one of the researchers involved in the project.
"It's surprising that it took such a long time to solve this problem," says Buda. But he admits it is only in the past five to ten years that computers have been able to handle the demanding quantum-mechanical calculations involved.
The research work has been published by the Journal of the American Chemical Society under the title "Spectroscopy and Quantum Chemical Modeling Reveal a Predominant Contribution of Excitonic Interactions to the Bathochromic Shift in  -Crustacyanin, the Blue Carotenoprotein in the Carapace of the Lobster Homarus gammarus." Here is a link to the abstract.
And if you want to know more about lobsters, but in plain English, you can read this page at Wikipedia. Or you can check Lobster Facts, written by Alan M. Stewart. It features a picture of a two-color lobster named the Joker, introduced by these words: "The odd thing about this animal is that the cephalothorax is all one [natural] color while the rest of the animal is symmetrically different. Even its mouth parts were normal-colored on the right, and orange on the left." Is this a real lobster or a PhotoShop joke? You'll tell me.
Sources: Philip Ball, Nature, February 15, 2005; and various websites
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