A DNA nanoswitch incorporating the fluorescent base analogue 2-aminopurine detects single nucleotide mismatches in unlabelled targetsElectronic supplementary information (ESI) available: Fig. S1, emission spectra of AP with and without Mg2+; Fig. S2, excitation spectra of AP with and without Mg2+; Fig. S3, excitation spectra of nanoswitches with and without Mg2+; Fig. S4, time-resolved data for all open nanoswitches; Fig. S5, time-resolved data for all closed nanoswitches; Fig. S6, proportional change in time-resolved emission for all nanoswitches; Table S1, time-resolved emission data. See DOI: 10.1039/b900325h

DNA nanoswitches can be designed to detect unlabelled nucleic acid targets and have been shown to discriminate between targets which differ in the identity of only one base. This paper demonstrates that the fluorescent base analogue 2-aminopurine (AP) can be used to discriminate between nanoswitches with and without targets and to discriminate between matched and mismatched targets. In particular, we have used both steady-state and time-resolved fluorescence spectroscopy to determine differences in AP environment at the branchpoint of nanoswitches assembled using complementary targets and targets which incorporate single base mismatches. [ABSTRACT FROM AUTHOR]