3SYW:
reference: Myotonic dystrophy type 1 RNA crystal structures reveal heterogeneous 1 x 1 nucleotide UU internal loop conformations., Kumar A, Park H, Fang P, Parkesh R, Guo M, Nettles KW, Disney MD, Biochemistry. 2011 Nov 15;50(45):9928-35. Epub 2011 Oct 20. PMID: 21988728

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