Figure 6.

NMR-based (a) folding topology and (b) solution structure of the four-repeat human telomere unimolecular G-quadruplex formed by the d[TAG₃(T₂AG₃)₃] sequence (form-1) in K⁺ solution (coordinates deposition: 2JSM, 2JSK) (101). The loop types starting from the 5′-end are double-chain-reversal, edge-wise and edge-wise. Two other groups have independently investigated the same system and come to similar conclusions (102–105). NMR-based (c) folding topology and (d) solution structure of the four-repeat human telomere unimolecular G-quadruplex formed by the d[TAG₃(T₂AG₃)₃TT] sequence (form-2) in K⁺ solution (coordinates deposition: 2JSL, 2JSQ) (101). The loop types starting from the 5′-end are edge-wise, edge-wise and double-chain-reversal. One other group has independently investigated the same system and come to similar conclusions (106).