Basepairs involving Sugar(S) edge of Cytosine and WatsonCrick(W) edge of Uracil is shown. Highlighted examples are found from RNA crystal structures obtained from PDB.

Base pairs stabilized by N-H...N/O type hydrogen bonds only

Basepair

(type & Orientation)

*Frequency

Example

Hydrogen bonding atoms with their precursors

C:U S:W Cis

5

Optimized Model Structure

C5-O2...N3-C6

C6-O2'...O2-C1'

C:U S:W Trans

2

Optimized Model Structure

C5-O2...N3-C6

C6-O2'...O4-C5

* 1st and 2nd numbers in Frequency column represent the numbers of occurences as base pairs and as base triplets, respectively.