SNIPPETS

Why does cooking turn lobsters red?

Q: Why do lobsters turn from dark blue-green to red when boiled? And why are they that dark colour in the first place?

A: A relatively simple explanation for the colour change emerged in a study published in 2002: Heat changes the shape of a protein called beta-crustacyanin in the shell, relaxing its bonds with the pigment astaxanthin. The freed pigment reflects wavelengths of light in the red spectrum. But it turned out that the heat-related shape change accounted for only about a third of the colour difference, according to a 2005 study by Dutch researchers in The Journal of the American Chemical Society. The new research pointed to a complex quantum-physics interaction that would account for a much larger shift —and for the living lobster’s original colour. When the red pigment is fully hidden in the enclosing protein, it absorbs all wavelengths of light, red as well as blue and green, so the lobster appears black. The previous research had found that the red pigment molecules were grouped in pairs within the crustacyanin, crossing each other in a tight X formation. The Dutch researchers calculated that they interfered with one another, causing shifts in their quantum energy states, thus altering the wavelengths of light that are absorbed. Using nuclear magnetic resonance imaging and spectroscopy to examine protein-pigment interactions, the researchers found that this effect was a large one, suggesting that it is the primary source of lobster colour.

C CLAIBORNE RAY

Male sensitivity written in genes

In human development, certain genes act as master switches, ensuring that we are born with similar attributes (one head, two lungs, 10 fingers) in nearly all circumstances. Such genes tend to be highly reliable and resistant to environmental factors. But the gene responsible for activating male development is surprisingly unstable, leaving the pathway to male sexuality fraught with inconsistency, a study finds. The SRY gene on the Y chromosome sets off the growth of male sex organs in human embryos (all of which start out essentially female). To study the gene, researchers at Case Western Reserve University looked at families in which daughters inherited a Y chromosome, a rare occurrence in which SRY fails to fire, leaving a genetically male embryo to develop as a sterile female. They found that SRY is highly vulnerable to environmental factors, allowing the slightest interruption to significantly alter male sexual development. That leads to a wide divergence of testosterone-related male attributes (among them muscle mass and aggression) from one man to another, according to the study, which was published in The Proceedings of the National Academy of Sciences. The variability probably serves an evolutionary purpose, said one of the authors, Dr Michael Weiss.

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