Non-canonical base pairing

Non-canonical base pairs are planar hydrogen-bonded of nucleobases, having hydrogen bonding patterns which differ from the observed in Watson-Crick pairs, as classic double-helical DNA. The structures polynucleotide strands both DNA and RNA molecules can be understood terms sugar-phosphate backbones consisting phosphodiester-linked D 2’ deoxyribofuranose (D ribofuranose RNA) sugar moieties, with purine or pyrimidine nucleobases covalently linked to them. Here, N9 atoms purines, guanine adenine, N1 pyrimidines, cytosine thymine (uracil RNA), respectively, form glycosidic linkages C1’ atom sugars. These schematically represented triangles one their vertices sugar, three sides accounting for edges through they bonds other including nucleobases. As also explained greater detail later this article, side opposite sugar-linked vertex is traditionally called edge, since involved forming constitute building blocks two adjacent referred to, Sugar Hoogsteen (C-H pyrimidines) edges. Each four different characterized by distinct edge-specific distribution respective bond donor acceptor atoms, complementarity which, turn, define pairing. double helical generally known have between complementary bases, Adenine: Thymine (Adenine: Uracil Guanine: Cytosine. They involve specific corresponding considered Canonical Base Pairs. At same time, helically twisted duplex grooves, major minor, respectively accessible additional potential molecular recognition events. Experimental evidence reveals that nucleotide bases capable a wide variety pairing various geometries, those Pairs [Figure 1]. Non-Canonical Pairs, held together multiple mostly stable. Most these play very important roles shaping structure function functional molecules. In addition occurrences several double-stranded stem regions, most loops bulges appear single-stranded secondary recurrent 3D motifs, where non-canonical central role. crucial mediating tertiary contacts structures.