1A8N:
reference: Solution structure of a Na cation stabilized DNA quadruplex containing G.G.G.G and G.C.G.C tetrads formed by G-G-G-C repeats observed in adeno-associated viral DNA., Kettani A, Bouaziz S, Gorin A, Zhao H, Jones RA, Patel DJ, J Mol Biol 1998 Sep 25;282(3):619-36. PMID: 9737926

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