“…Another class of 2′-modification is the BNA in which the ribose 2′-oxygen is linked to the 4′-carbon via a methylene bridge as in Locked Nucleic Acid (LNA; Wengel et al, 2001) and carbocyclic-LNA (Srivastava et al, 2007; Bramsen et al, 2009), via an ethylene bridge as in ethylene-bridged nucleic acid (ENA; Hamada et al, 2002) and carbocyclic-ENA (Srivastava et al, 2007; Bramsen et al, 2009), or to the 1′-carbon as in oxetane (OXE; Pradeepkumar et al, 2003; Bramsen et al, 2009). This radical modification type generates nucleotides with interesting properties to siRNA design; The methylene bridge in the very popular LNA-modification locks the sugar moiety in the RNA-helical C3′- endo conformation, which additively increase RNA duplex thermostability by 2–10°C per LNA (Petersen and Wengel, 2003).…”