A and B, correlation between the relative infectivities of the phage variants fd ΔN2, fd G3P Δβ6, fd wild-type G3P APA, and fd wild-type G3P toward pilus-free (F−) E. coli HB2156 cells with the midpoints of the thermal transitions, Tm, of the N2 domains of the respective G3P* variants (taken from Table 1) (A) and the apparent dissociation constants, KD(app), of the complexes between the G3P* variants and TolA-C-Aedans (taken from Table 2) (B).