As illustrated by the results above, through careful tailoring of G4-forming sequences we achieve a dramatic reduction of the intrinsic conformational heterogeneity of the wild-type telomeric G4s and a selective favoring of specific G4 conformations that are otherwise only marginally stable. Our single-molecule FRET experiments utilizing these sequences allowed obtaining characteristic signatures of different G4 conformations and thus permitted linking the experimentally observed E states to distinct folded G4 conformations.