The anti-parallel basket type G4 conformation containing only two tetrads has been previously observed to form from the human telomeric sequence (7). To check if this structure could contribute to the E≈0.57 state, we used a modified telomeric sequence where a guanine at position 14 was replaced by an inosine (hTelo-I14), which has been shown to favor the formation of the 2-tetrad anti-parallel basket conformation (48). Three E states were observed in the FRET histogram obtained for this sample (Figure 2D), where the low and high E states correspond to unfolded and chair conformations, respectively, whereas the intermediate peak appearing at E≈0.6 is expected to originate from the 2-tetrad basket conformation. The E≈0.57 state observed for the wild-type sequence (Figure 1F) is thus assigned to this conformation.