Fig. 2. (A) SNAr reaction of DFS with peptides is sequence and solvent-dependent. (B) Rates in all conditions were measured by monitoring absorbance at 320 nm, and identities of the products were confirmed by NMR and Liquid Chromatography Mass-Spectrometry (LCMS, ESI Fig. S7 and S12–S15†). (C) The rate of the reaction correlates with acidity of the thiol; pKa were estimated by measuring the absorbance of peptides at 240 nm as described in ESI Fig. S18† and were in accordance with previously reported values for CXC peptides.25.
