astronomer corner

sciencenote:

For the past 20 years, scientists have used a variety of colored fluorescent proteins, derived from jellyfish and corals, to visualize cells and their organelles and molecules. But using fluorescent probes to peer inside live mammals has posed a major challenge. The reason: hemoglobin in an animal”s blood effectively absorbs the blue, green, red and other wavelengths used to stimulate standard fluorescent proteins along with any wavelengths emitted by the proteins when they do light up. To overcome that roadblock, the laboratory of Vladislav Verkhusha, Ph.D., associate professor of anatomy and structural biology at Einstein and the study”s senior author, engineered a fluorescent protein from a bacterial phytochrome (the pigment that a species of bacteria uses to detect light). This new phytochrome-based fluorescent protein, dubbed iRFP, both absorbs and emits light in the near-infrared portion of the electromagnetic spectrum – the spectral region in which mammalian The researchers targeted their fluorescent protein to the liver – an organ particularly difficult to visualize because of its high blood content. Adenovirus particles containing the gene for iRFP were injected into mice. Once the viruses and their gene cargoes infected liver cells, the infected cells expressed the gene and produced iRFP protein. The mice were then exposed to near-infrared light and it was possible to visualize the resulting emitted fluorescent light using a whole-body imaging device. Fluorescence of the liver in the infected mice was first detected the second day after infection and reached a peak at day five. (See accompanying image.) Additional experiments showed that the iRFP fluorescent protein was nontoxic.