Isolated truncated and mutated sensor proteins derived from flavoproteins that are 12-20 KDa or less, genetically encoded for detection and imaging of protein complexes having long fluorescent lifetimes that can be 4.0 ns or greater.
STATEMENT OF GOVERNMENTAL SUPPORT
 The present invention was supported by the Laboratory Directed Research and Development program under Contract No. DE-AC02-05CH11231 awarded by the U.S. Department of Energy. The present invention was supported under RO1 GM086233-02 awarded by the NIH. The government has certain rights to the invention.