Figure 1: Schematic representations of the structures.
From: X-ray characterization of mesophases of human telomeric G-quadruplexes and other DNA analogues
(a) Top view of the parallel-stranded 22-mer HT-quadruplex (PDB: 1KF1) formed by the sequence AG3(TTAG3)3. In this conformation (observed in the crystalline state5 as well as in the non-crystalline state under molecular crowding conditions6,7), four parallel GGG runs form a stack of three planar G-quartets in the central core and TTA segments fold into loops projecting outwards. (b) Side view of the 22-mer HT-quadruplex. K+ ions (purple) reside inside the G-quadruplexes and they are positioned between the adjacent G-quartets. (c) G-quartet made of four GMP monomers. Thin black lines represent the hydrogen bonds holding nucleotides together in a planar cyclic arrangement. (d) Top view of the GMP-quadruplex in ordered columnar phase, where stacking is helical with an azimuthal rotation of 30° between adjacent G-quartets13. G-quartets in c & d are modeled from 22-mer HT-quadruplex (PDB: 1KF1) shown in a & b.
