Cu²⁺–diethylaminosalicylaldehyde self-dimer for regulation of DNA amplification with changes in fluorescence

In this study we developed a new green-fluorescent nucleoside (dUHzDESA) by attaching a diethylaminosalicylaldehyde (DESA) unit to deoxyuridine (dU) through a hydrazone (Hz) linker. Interestingly, dUHzDESA chelated selectively with Cu²⁺ ions to form dimer pairs in DNA duplexes with a change in fluorescence. We used this property of Cu²⁺-induced dUHzDESA dimer pairing to regulate DNA amplification processes [i.e., the polymerase chain reaction (PCR) of linear DNA and the rolling circle amplification (RCA) of circular DNA] by exploiting corresponding changes in conformation. We synthesized DNA containing hydrazone–DESA (HyDESA) functional groups by applying stepwise enzymatic syntheses and post-synthetic methods using deoxyuridine triphosphate (dUHzTP) and DESA, producing the linear templates DESAHzDNA1 and DESAHzDNA2 and the cyclic template C-Hz9-DNA-DESA. PCR amplification of DESAHzDNA1 and DESAHzDNA2 and RCA of the circular DNA C-Hz9-DNA-DESA could be regulated reversibly, by adding Cu²⁺ ions for switching off and glutathione for switching on. The fluorescence of the HzDESA functional group allowed us to monitor the switching off and on of these amplification processes. Thus, coordination chemistry has potential for application in the regulation of amplification of DNA.