Succinimidyl carbonate coupling

Figure 13.6 APTS-modified surfaces can be activated with DSC to form amine-reactive succinimidyl carbonates for coupling proteins or other amine-containing molecules.

Miron, T., and Wilchek, M. (1993) A simplified method for the preparation of succinimidyl carbonate polyethylene glycol for coupling to proteins. Bioconjugate Ghent. 4, 568-569. 

Unlike the succinimidyl succinate or succinimidyl glutarate activation methods, succinimidyl carbonate chemistry does not suffer from the presence of a labile ester bond. The intermediate carbonate may hydrolyze in aqueous solution to release NHS and C02, essentially regenerating the underivatized PEG hydroxyl. After coupling to amine-containing molecules, however, the resultant carbamate linkage stabilizes the chemistry to the point that a modified molecule will not lose PEG by hydrolytic cleavage. For these reasons, the succinimidyl carbonate method of PEG activation and... 

Miron T, Wilchek M (1993). A simplified method for the preparation of succinimidyl carbonate polyethylene glycol for coupling to proteins. Bioconjug. Chem. 4 568-569. Dolence E K, Hu C, Tsang R, et al. (1997). Electrophilic polyethylene oxides for the modification of polysaccharides, polypeptides (proteins) and surfaces. U.S. Patent 5,985,263. 

One of the first studies involved the modification of interferon of-la with linear succinimidyl carbonate PEG (SC-PEG 5 kDa), in base buffer pH 10, via a urea linkage. The coupling, performed at an equimolar ratio of protein and polymer, led mainly to mono-PEGylated isomers and, in small amounts, to di-PEGylated conjugates and free interferon. Characterization of the conjugates indicated that lysine residues were the only site of PEGylation [47]. 

EPR experiments on carbon-centred radicals with either a- or /J-boronic ester substituents have been reported.168 While the a-substituted radicals were modestly thermodynamically stable, the /J-substituted radicals underwent easy /J-climination. An EPR experiment on the photo-oxidation of phenolic compounds containing at least one free ortho position has indicated the formation of persistent secondary radicals derived from dimerization or polymerization from C-0 coupling.169 The structure of the succinimidyl radical has been re-examined using density functional theory with a variety of basis sets. The electronic ground state was found to be of cr-symmetry allowing for facile -scission. These conclusions were also predicted using MP2 but... 

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