Magnets help tell left from right

Many molecules come in two forms or "enantiomers" that are mirror images of each other. Most chemical reactions produce equal numbers of so-called right- and left-handed enantiomers. For some reason, however, the amino acids which make up the proteins in the human body are all left-handed. Understanding the reasons for this is one of the oldest challenges in biology. Now Geert Rikken and E Raupach of the Grenoble High Magnetic Field Laboratory in France have shown for the first time that the combined effect of a magnetic field and light can lead to an excess of one type enantiomer over its mirror image (G Rikken and E Raupach 2000 Nature 405 932).