1N66:
reference: Structure of the pyrimidine-rich internal loop in the poliovirus 3'-UTR: the importance of maintaining pseudo-2-fold symmetry in RNA helices containing two adjacent non-canonical base-pairs., Lescrinier EM, Tessari M, van Kuppeveld FJ, Melchers WJ, Hilbers CW, Heus HA, J Mol Biol 2003 Aug 22;331(4):759-69. PMID: 12909008

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