2KF7:
reference: Structure of the Human Telomere in K(+) Solution: A Stable Basket-Type G-Quadruplex with Only Two G-Tetrad Layers., Lim KW, Amrane S, Bouaziz S, Xu W, Mu Y, Patel DJ, Luu KN, Phan AT, J Am Chem Soc. 2009 Mar 9. PMID: 19271707

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