1FUF:
reference: Crystal structures of two forms of a 14-mer RNA/DNA chimer duplex with double UU bulges: a novel intramolecular U*(A x U) base triple., Deng J, Xiong Y, Sudarsanakumar C, Shi K, Sundaralingam M, RNA 2001 Oct;7(10):1425-31. PMID: 11680847

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