Figure 4.

NMR-based (a) (3 + 1) folding topology and (b) solution structure of the three-repeat human telomere bimolecular G-quadruplex formed by the d[G₃(T₂AG₃)₂T] sequence in Na⁺ solution (coordinates deposition: 2AQY) (96). All three G-tracts from one strand and the 3′-terminal G-tract from the partner strand are used to form the bimolecular G-quadruplex. (c) Schematic of hypothetical G-quadruplex formation when the 3′-end overhang (in red) invades the adjacent double-stranded segment of the telomere to form the so-called t-loop (97).