Time-lapsed confocla microscopic images of T-cells undergoing apoptosis. The green fluroescence (a cyanine dye, which indicates a mitochondrial membrane potential) marks healthy cells, while the red fluorescence is derived from PhipPhiLux cleavage in apoptotic cells.
Time-of-death determinations are not just a challenge for coroners. Researchers in the field of apoptosis are constantly striving for ways to detect the onset of cell death earlier and with greater specificity to bring them closer to the true cause of cell death. Now a small company in College Park, Maryland, OncoImmunin Inc., has provided just the tool apopoticians have been seeking. Specializing in peptide-based diagnostics for cancer and infectious diseases, this company has designed a new class of fluorogenic protease substrates that gives the earliest determinations of the onset of cell death to date. PhiPhiLux, short for fluorescent-fluorescent light, incorporates the prototypical caspase-3-recognition sequence DEVD into a bifluorophore-derivitized peptide, which mimics the structural loop...

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