The infrared fluorescence protein war
In vivo optical imaging of deep tissues is most feasible between 650 and 900 nm because hemoglobin, water, and lipids minimally absorb these wavelenghts and tissue light-scattering is also minimal. Roger Tsien, last year's Nobel Prize in chemistry for his research on fluorescent proteins, describes now in a Science report a modified version of the Deinococcus radiodurans phytochrome engineered to be a Infrared Fluorescent Protein (IFP). The group transduced IFP into the mouse liver through an adenovirus-vector, and observed with a Maestro spectral imager that this infrared fluorescence protein performed better than a red fluorescent protein (mKate). For more background info read Brainwindows.
Shu, X., Royant, A., Lin, M., Aguilera, T., Lev-Ram, V., Steinbach, P., & Tsien, R. (2009). Mammalian Expression of Infrared Fluorescent Proteins Engineered from a Bacterial Phytochrome Science, 324 (5928), 804-807 DOI: 10.1126/science.1168683
Filonov GS, Piatkevich KD, Ting LM, Zhang Z, Kim K & Verkhusha VV (2011).
Bright and stable near-infrared fluorescent protein for in vivo imaging
Nature Biotechnology, 29, 757–761 DOI: 10.1038/nbt.1918