Detection of nucleic acids using g-quartets and i-tetraplexes

Abstract

G-quartet structures have been found to be useful in fluorescence assays to detect a selected nucleic acid sequence. When oligonucleotides containing these structures are labeled with a donor fluorophore and an acceptor dye, the folding or interaction of the oligonucleotides in the G-quartet structure brings the donor-acceptor pair into close proximity, allowing an interaction between the two labels which results in quenching of donor fluorescence or a change in other fluorescence properties which are the result of the interaction of two dyes in close proximity. The G-quartet structure unfolds or is otherwise disrupted upon hybridization to its complementary sequence, increasing the distance between the two dye labels. This results in decreased donor quenching or a change in another proximity-related fluorescence parameter. The associated increase in donor fluorescence intensity or the change in another fluorescence parameter may be monitored as an indication of the presence of a selected nucleic acid sequence. Alternatively, in some cases a decrease in acceptor fluorescence may be monitored as an indication of the presence of the selected nucleic acid sequence when the acceptor is also a fluorophore. Related structures, such as the i-tetraplex, may also be useful in similar methods for detection of a selected nucleic acid sequence.