Figure 34.

Chemical shift/structure relationships in nucleic acids can aid structural elucidation of ESs. A) Scatter plot of ¹³C chemical shifts obtained from the BMRB for different secondary structure contexts in RNA (Watson-Crick BPs in A-form helices: black; nucleotides in bulges, internal or apical loops: gold; syn bases: blue). B) Distribution of ¹H and ¹⁵N chemical shifts for U-N3 and G-N1 as a function of the BP type (G-C Watson-Crick BPs: red; U-A Watson-Crick BPs: blue; G-U wobbles: purple; U-G and U-U wobbles: green; sheared G-A mispairs: orange, with the base whose shifts are shown being colored), as obtained from the BMRB. C) Correlation between the C1′ and C4′ chemical shifts in RNA as obtained from a survey of the BMRB for nucleotides in different structural contexts (helical: blue; non-helical: orange; flanking,i.e., helical BP neighboring loops or bulges: green). Black lines correspond to the upper boundaries for C3′-endo sugar chemical shifts as obtained based on the average and standard deviation of the chemical shifts for helical nucleotides.(A) and (B) were reprinted with permission from [9] while (C) was reproduced with permission from [166].