Kinetic analyses of 4E-BP1, 4E-BP1 (R51–N64), and eIF4G peptides via SPR. The effect of ionic strength at 25 °C on (A) ka, (B) kd, and (C) Kd. Statistical significance was determined using unpaired, two-tailed Student’s t tests. ns = not significant (p > 0.05). (A) **: p = 0.0025; ***: p = 0.0002. (B) **: p = 0.0023. (C) *: p = 0.0161; **: p = 0.0024 and 0.0041, respectively. Please see Tables S4–S6 for tabulated results, p values, and statistical analyses. In (A), the error bar for eIF4G is too small to see (Table S4).