Figure 3. STD-NMR experiments for the determination of RRM3-RNA target binding affinity. (A) Expansion of the aromatic region of the 1D ¹H NMR reference spectrum (top) and STD NMR spectrum (bottom) of RRM3 with ACUCC RNA at a protein: RNA ratio of 1:13 recorded at 1 s of saturation time and 5 °C. Due to the ligand excess, the signals in the reference spectrum correspond to aromatic protons of the RNA oligonucleotide. A black star stands for the signal monitored in the isotherm. (B) Binding isotherm from STD-AF values during the titration of RRM3 with the ACUCC oligo.