Figure 2.

Overview of possible configurations when combining two T^ImH+ nucleotides within an otherwise unspecified dsDNA sequence. (A) and (B) provide a schematic evaluation of the positions amenable to introduction of a second T^ImH+ in the presence (indicated by T* in the sequence) of a non-motif respectively in-motif T^ImH+ nucleotide. The letter ‘b’ (for both) is used to indicate that a second T^ImH+ introduced at this position may adopt an in-motif or non-motif configuration depending on the local base-pair context. When only a non-motif configuration is possible, this is indicated with ‘n’. The pK_a-motif is shown as explained in Figure 1B. The ‘x’ indicates a position where the outcome of introducing a second T^ImH+ creates an ambiguous situation, because two pK_a-motifs overlap (see text).