Table 2. Dissociation constants (K_d) of Δ-som and triple fluorinated Δ-som analogues obtained by ¹⁵N,¹H-HSQC and direct ¹⁹F NMR titrations.

		PROTEIN 15N/1H Tracked/μM	LIGAND 19F Tracked (Triple-F)/μM
AGSKNFFWKTFTSS	Δ-som	103 ± 47	N/A
AGSKNFFWKTFTSS	F1,2,3 Δ-som	48 ± 35	108 ± 15
AGSKNFFWKTFTSS	F1,2,3 Δ-som	48 ± 35	33 ± 11
AGSKNFFWKTFTSS	F1,2,3 Δ-som	48 ± 35	45 ± 14
AGSKNFFWKTFTSS	F1,2,3 Δ-som	48 ± 35	62 ± 13*

Phe residue(s) used to measure K_d by ¹⁹F NMR are underlined in each sequence and shown in BOLD in column 2. Standard errors from the Levenberg-Marquardt fitting routine of equation (1) were taken as the uncertainties.

^*F1,2,3 Δ-som ¹⁹F tracked K_d is the mean K_d calculated from the result obtained from each monitored ¹⁹F resonance in the triple fluorinated peptide.