Zhou S, Mozziconacci O, Kerwin BA, Schöneich C. The photolysis of disulfide bonds in IgG1 and IgG2 leads to selective intramolecular hydrogen transfer reactions of cysteine Thiyl radicals, probed by covalent H/D exchange and RPLC-MS/MS analysis.
Pharm Res 2013;
30:1291-9. [PMID:
23307417 DOI:
10.1007/s11095-012-0968-1]
[Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Accepted: 12/17/2012] [Indexed: 11/25/2022]
Abstract
PURPOSE
The evaluation of photo-instability of biotherapeutic products is mandated by regulatory agencies. Photo-irradiation can induce oxidative modifications in proteins, which may lead to undesired biological and therapeutic consequences. Among the modifications, epimerization of amino acid residues can occur upon photo-irradiation of IgGs.
METHODS
We show here, that UV irradiation (λ = 253.7 nm) of IgG1 and IgG2 leads to the formation of intermediary carbon-centered radicals, validated by covalent incorporation of deuterium into the protein primary sequence.
RESULTS
By MS/MS analysis we identified the sites of deuterium incorporation, such as the sequence QD [303:304, HC], present in the peptide of VVSVLTVVHQDWLNGK [294:309, HC] in both IgG1 and IgG2, and V [111, LC] and K [116, LC], present in the peptide VTVLGQPK [109:116, LC] in IgG2. Both peptides are in the proximity of intrachain disulfide bonds.
CONCLUSIONS
The exposure of IgG1 and IgG2 to UV-light (λ = 253.7 nm) generates specific carbon-centered radicals. The latter were evidenced by a covalent H-D exchange reaction that likely occurred through a hydrogen atom transfer reaction between cysteine thiyl radical and C-H bond.
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