The key, say Michele Cianci of the University of Manchester and colleagues in a report published recently in the Proceedings of the National Academy of Sciences, is the lobster shell protein beta-crustacyanin. In living lobsters, this molecule binds a pigment molecule known as astaxanthin, flattening it and thus rendering it blue (a good color for crustacean camouflage). In its unbound form, however, astaxanthin is reddish-orange in hue. Cooking the lobster, it turns out, denatures the beta-crustacyanin such that it frees astaxanthin, thereby setting the shell ablaze.
Probing the color change required that the team use x-ray crystallography to analyze the beta-crustacyanin complex¿s three-dimensional structure. This was no easy task: as its name suggests, the technique requires crystals of the pigment-bound proteins--crystals that classic growing methods failed to produce. Team member Naomi Chayen of Imperial College London eventually cultivated the crystals using the so-called Microbatch method, in which they are grown in oil.
Chayen notes that in addition to resolving a longstanding biological puzzle, the new findings might have intriguing biomedical applications. "This could lead to an important new use of astaxanthin as a drug-delivery mechanism for medicines that are insoluble in water, and give designers of new food colorants or dyestuffs an interesting new capability," she remarks.