Figure 4. PROP ring proton ¹H-NMR chemical shift variation upon amino acids addition reported as Δ.

Δ = (|(δ’−δ₀)|/δ₀)·100 represents the absolute value of the difference between the ¹H-NMR signal (ppm) of the PROP ring proton in the absence (δ₀) and in the presence (δ’) of the amino acid of the Ps-1 and II-2 sequences, normalized for δ₀ and expressed as a percentage. For each amino acid, two spectra were recorded in 0.5 mL of 5 mM D₂O solution before and after the addition of an equimolar amount of PROP.