2L8F:
reference: NMR structure of a 4 x 4 nucleotide RNA internal loop from an R2 retrotransposon: Identification of a three purine-purine sheared pair motif and comparison to MC-SYM predictions., Lerman YV, Kennedy SD, Shankar N, Parisien M, Major F, Turner DH, RNA. 2011 Sep;17(9):1664-77. Epub 2011 Jul 21. PMID: 21778280

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