Fig. 3
From: Rebooting life: engineering non-natural nucleic acids, proteins and metabolites in microorganisms
Various XNA chemical structures. a Different strategies incorporating possible chemical alteration in nucleic acid structure which includes nucleobase, sugar, 2ʹ-ribose and phosphate modifications b Examples of nucleobase modified XNA molecules, including g 5-chloro-20-deoxyuridine (5ClU), 5-methyl-20-deoxycytidine (5MeC), 5-fluoro-20-deoxycytidine (5FC), 7-deaza-20-deoxyadenosine (7dA), 7-deaza-20-deoxyguanosine (7dG), 7-fluoro-7-deaza-20-deoxyguanosine (7FG), and 20-deoxyinosine (dI). c Examples of sugar modified XNA molecules, including hexitol nucleic acid (HNA), cyclohexenyl nucleic acid (CeNA), threose nucleic acid (TNA), 30–20 phosphonomethyl-threosyl nucleic acids (tPhoNA). 4ʹ-ribose-modified 4ʹ-thioDNA, arabino nucleic acid (ANA), 20-fluoro-arabino nucleic acid (FANA), and locked nucleic acid (LNA). d Examples of 2ʹ-ribose modified XNA molecules, including LNA, 20-O-methyl DNA (20-OMe-DNA), and 20-fluoro DNA (20-F-DNA). e Examples of phosphate modified XNA molecules, including tPhoNA, 50–30 phosphonomethyl-deoxyribosyl nucleic acids (dPhoNA), phosphorothioate modified DNA (PS-DNA), TriazoleDNA, and PN-DNA. f Examples of stereoisomeres molecules, including mirror-image nucleic acid (L-DNA). The figure is reproduced with permission from Eremeeva and Herdewijn [24] ©Elsevier