Deep into the red

From Scientific American, July 2009 (online May 8, 2009):
Mind control has been traditionally the realm of the hypnotist, but research in the field of fluorescent proteins is opening up the possibility of controlling cellular processes, gene activity and even behavior using nothing more than infrared light.
Fluorescent proteins, which are compounds that can absorb and then emit light, have become a powerful instrument in the cell biologist’s toolkit—so powerful, in fact, that the discovery and development of green fluorescent proteins from jellyfish earned the 2008 Nobel Prize in Chemistry. These proteins have limitations, however: They need to be excited with the blue to orange part of the visible spectrum, at wavelengths of 495 to 570 nanometers. These wavelengths of light are too short to penetrate tissue very well, and so green fluorescent proteins are mainly used in test tube studies to watch cell division or to label certain cell types.
But one of the 2008 Nobelists, Roger Y. Tsien of the University of California, San Diego, and his U.C.S.D. colleagues report in today’s issue of Science that they have developed a new fluorescent protein that could enable scientists to tag and visualize cellular activity as it happens inside a live animal. The protein, after absorbing light from the far-red part of the spectrum, shines in the near-infrared, at wavelengths of around 700 nanometers. Read more.