Tag properties of RNA tag-labeling technologies.

aSwitching of fluorescence emission depending on the existence of tag RNA.
bNumber of dyes per one tag unit. Two dyes are attached to a nucleotide in an ECHO probe and two MS2-coat proteins bind to a tag RNA.
cNucleotide length of a synthetic DNA unit containing one or more tag sequences for plasmid synthesis and the number of tag sequences therein.
dNucleotide length necessary for probe binding in a tag sequence.
eMaximum repetition number of the tag attached to an RNA sequence reported in the literature.
fMolecular beacons form a linear structure at the emissive RNA-binding state and a stem–loop structure in the nonemissive free state.
gThe structure of the malachite green aptamer includes two Watson-Crick helices flanking an asymmetric loop. See ref. [41].