Skip to main content
. 2017 Dec 5;139(50):18365–18375. doi: 10.1021/jacs.7b10702

Figure 4.

Figure 4

Addition of N-nucleophiles to Dha on proteins is compatible with disulfides. (a) Comparative experiment where the readily formed disulfide dimer of C2Am-Cys95 was exposed to a S-nucleophile, β-mercaptoethanol 28, and to an N-nucleophile, benzylamine 2a. (b) ESI–MS spectrum of the reaction of disulfide dimer of C2Am-Cys95 with benzylamine shows the unreacted dimer of C2Am-Cys95 indicating that benzylamine does not cross-react with the disulfide. (c) ESI–MS spectrum of the reaction of disulfide dimer of C2Am-Cys95 with β-mercaptoethanol 28 shows rapid disulfide reduction and formation of the monomer C2Am-Cys95. (d) Conversion of the free Cys34 of Recombumin to Dha and addition of benzylamine 2a. (e) ESI–MS spectrum of the product of the reaction of Recombumin-Cys34 with α,α′-dibromo-adipyl(bis)amide 10. (f) Reaction of Recombumin-Dha34 with benzylamine 2a results in a homogeneous conjugate Recombumin-NHBn34, as shown in the ESI–MS spectrum. (g) Surface representation of Recombumin showing the Cys residue at site 34 (in pink) that is first converted into Dha and then used as a handle for aza-Michael ligation. A number of disulfides bridges that are solvent exposed are shown in yellow.