Bridging modifications were developed under the concept of "fixing the fluctuating conformation of the sugar moiety by bridging." The sugar moiety can be fixed to the RNA type (N type) by chemically modifying the 2'- and 4'-positions of the sugar moiety. This confers excellent binding affinity to the target complementary strand nucleic acid, and furthermore, steric hindrance due to bridging is expected to improve functionality including nuclease resistance. In 1997, 2',4'-BNA/LNA (bridged nucleic acid) was developed by Imanishi, Obika, and others from the School of Pharmaceutical Sciences, Osaka University.1), 2)