Design of two and three input molecular logic gates using non-Watson-Crick base pairingbased molecular beacons?

摘要

This study presents a single, resettable, and sensitive molecular beacon (MB) used to operate molecularscale logic gates. The MB consists of a random DNA sequence, a fluorophore at the 50-end, and a quencher at the 3'-end. The presence of Hg~(2+), Ag~+, and coralyne promoted the formation of stable T-Hg~(2+)-T, C-Ag~+-C, and A_2-coralyne-A_2 coordination in the MB probe, respectively, thereby driving its conformational change. The metal ion or small molecule-mediated coordination of mismatched DNA brought the fluorophore and the quencher into close proximity, resulting in collisional quenching of fluorescence between the two organic dyes. Because thiol can bind Hg~(2+) and remove it from the T-Hg~(2+)-T-based MB, adding thiol to a solution of the T-Hg~(2+)-T-based MB allowed the fluorophore and the quencher to be widely separated. A similar phenomenon was observed when replacing Hg~(2+) with Ag~+. Because Ag~+ strongly binds to iodide, cyanide, and cysteine, they were capable of removing Ag~+ from the C-Ag~+-C-based MB, restoring the fluorescence of the MB. Moreover, the fluorescence of the A_2-coralyne-A_2-based MB could be switched on by adding polyadenosine. Using these analytes as inputs and the MB as a signal transducer, we successfully developed a series of twoinput, three-input, and set-reset logic gates at the molecular level.