Figure 2.

Single-molecule FRET histograms as a function of K⁺ concentrations for the mutated HTDMs; (A) side-guanine (s-mut1) and (B) central-guanine (c-mut). The single-molecule FRET histograms of c-mut were previously reported (22). The peaks at zero result from donor-only molecules and hence are ignored. (C) Comparison of folded FRET peaks at 200 mM K⁺ for each mutated HTDM (top: s-mut1, middle: s-mut2 and bottom: c-mut). All the peaks were fitted by multiple Gaussian functions. Two peaks in s-muts correspond to folded states. In c-mut, the low FRET peak (∼0.45) represents an unfolded single-stranded overhang, and two other peaks correspond to folded states.