Fig. 3

Chemical modifications of miRNA oligonucleotides. Structures of chemically modification. a Structures of the most commonly used chemical modifications in oligonucleotide chemistry; locked nucleic acid (LNA) is a bicyclic RNA analogue in which the ribose is locked in a C3′-endo conformation by introduction of a 2′-O,4′-C methylene bridge, b the nonbridging phosphate atom is replaced with a sulfur atom to give a phosphorothioate (PS) modification, c six-membered morpholine ring replaces the sugar moiety in morpholino oligomers. d In the ribose 2′-OH group modification: the 2′-OH group is modified with 2′-O-methyl (2′-O-Me), e 2′-OH group is modified with 2′-fluoro (2′-F), f 2′-OH group is modified with 2′-O-methoxyethyl (2′-MOE)