Anomalous Conformations of RNA Constituents : 2D NMR and Calculational Studies

摘要: Short single-stranded RNA fragments normally display a strong tendency to favour right-handed helical conformation. Relatively small changes in enthalpy and/or entropy of stacking, induced by minor structural variations may cause large difference stacking behaviour aqueous solution, but do not appear affect the detailed geometry stacked state. Recently developed NMR methods that allow for determination sugar-phosphate backbone along β (O5’-C5’), γ (C5’-C4’), δ (C4’-C3’), and e (C3’-O3’) are surveyed. At level trimers higher oligomers conformational transmission factors, such as next-nearest-neighbour interactions, come into play. For example, trimer U-A¯-U (A¯ = m2 6A) behaves fashion can be predicted from known properties its dimer constituents U-A¯ A¯-U, whereas A¯-U-A¯ an entirely different way. In latter compound two purines engage 1-3 interaction. same time central pyrimidine residue is pushed outside purine-purine interaction zone (bulge-out).