3SSF:
reference: Structure of an RNA/DNA dodecamer corresponding to the HIV-1 polypurine tract at 1.6 A resolution., Drozdzal P, Michalska K, Kierzek R, Lomozik L, Jaskolski M, Acta Crystallogr D Biol Crystallogr. 2012 Feb;68(Pt 2):169-75. Epub 2012 Jan 6. PMID: 22281746

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