i-Motif folding intermediates with zero-nucleotide loops are trapped by 2′-fluoroarabinocytidine via F···H and O···H hydrogen bonds

Abstract

The oligonucleotide d(TC5) forms a well-characterized tetrameric i-motif in solution; however, the isolation of dimeric and trimeric intermediates remains challenging. Here, the authors report that 2′-deoxy-2′-fluoroarabinocytidine substitutions can prompt TC5 to form dimeric i-motif folding intermediates through fluorine and oxygen hydrogen bonds.