“…Recently, fluorophore binding RNA aptamers have gained attention for their potential to meet these challenges. One of these aptamers, known as Spinach (Paige et al, 2011) or in its more recently improved form, Spinach2 (Strack et al, 2013), has been used for a number of in vitro and synthetic biology applications (Chizzolini et al, 2014; Hofer et al, 2013; Nakayama et al, 2012; Pothoulakis et al, 2014; Shu et al, 2014; van Nies et al, 2013), as well as for detecting triplet repeat RNAs (Strack et al, 2013), protein expression (Song et al, 2013), and metabolites (Paige et al, 2012) in living cells. Both aptamers bind a conditional fluorophore known as DFHBI (3,5-difluoro-4-hydroxybenzylidene imidazolinone), which is reported to have limited fluorescence on its own, but fluoresces similarly to enhanced GFP (EGFP) when bound (Paige et al, 2011).…”