The pGlow TOPO® TA Expression Kit uses the Cycle 3 GFP mutant (1) as a reporter protein for transcriptional activity. Cycle 3 GFP is ideal for non-invasive analysis of promoter elements within intact, living cells. The fluorescent property of Cycle 3 GFP allows in vivo detection in virtually any cell type or species using microscopy with wild-type GFP filter sets or by fluorescence-activated cell sorting methods.