Structure and nuclease resistance of 2',4'-constrained 2'-O-methoxyethyl (cMOE) and 2'-O-ethyl (cEt) modified DNAs.

Combining the structural elements of the second generation 2′-O-methoxyethyl (MOE) and locked nucleic acid (LNA) antisense oligonucleotide (AON) modifications yielded the highly nuclease resistant 2′,4′-constrained MOE and ethyl bicyclic nucleic acids (cMOE and cEt BNA, respectively). Crystal structures of DNAs with cMOE or cEt BNA residues reveal their conformational preferences. Comparisons with MOE and LNA structures allow insights into their favourable properties for AON applications.