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Why is DNA polymorphic while RNA is not?
Author(s) -
Sundaralingam M.,
Rao S. T.
Publication year - 2009
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560240729
Subject(s) - chemistry , dna , rna , deoxyribose , steric effects , base pair , stereochemistry , intramolecular force , nucleic acid , hydrogen bond , nucleobase , ring (chemistry) , molecule , biochemistry , organic chemistry , gene
In DNA, the base‐sugar hydrophobic interactions between the 2′‐methylene group of the 2′‐deoxyribose sugar and the base (H6 in pyrimidines and H8 in purines) on the 3′‐side appear to act as a ball joint and facilitate the A‐DNA ↔ B‐DNA conformational interconversion by lowering the pseudorotational barrier. These and other sugar‐base interactions coupled with the inherently more flexible 2′‐deoxyribofuranose ring allow DNA to occur in a variety of polymorphic helical states. In contrast, the 2′‐hydroxyl group in RNA not only sterically disfavors the B‐type structure, but the inherently less flexible ribofuranose ring is further stabilized in the A‐type structure by intramolecular hydrogen‐bonded water bridge between the 2′‐OH group and the base (O2 in pyrimidines and N3 in purines). This lack of flexibility of RNA dictates that DNA‐RNA hybrid structures assume the A‐type helix.