FIGURE 1.

In vitro selection of ligand-binding aptamers with fluorescence detection. The green pathway shows a relatively conventional two-step strategy of (1) selecting an aptamer responsive to a given ligand such as ATP, followed by (2) appending a fluorescent chromophore that renders the aptamer useful for signaling (Jhaveri et al. 2000b). The blue pathway shows an alternate one-step strategy in which fluorescent aptamers are selected directly by incorporation of one or more fluorescently labeled mononucleotides during the selection process (Jhaveri et al. 2000a).