Structural Effects of Incorporation of 2'‐Deoxy‐2'2'‐Difluorodeoxycytidine (Gemcitabine) in A‐ and B‐Form Duplexes

We report the structural effect of 2'-deoxy-2',2'-difluorocytidine (dFdC) insertions in DNA strand a : RNA hybrid duplex and self-complementary duplex. In both cases, modification slightly destabilizes provokes minor local distortions that are more pronounced case hybrid. Analysis solution structures determined by NMR methods show dFdC is an adaptable derivative adopts North type sugar conformation when inserted pure DNA, or South context hybrids. this latter context, pucker favors formation 2'F⋅⋅H8 attractive interaction with neighboring purine, which compensates destabilizing base pair distortions. These interactions share some features pseudohydrogen bonds described previously other nucleic acids fluorine modified sugars.