Photostability conditions as prescribed by ICH guidelines induced highly reduction-resistant scrambled disulfides that contribute to the population of apparent nonreducible aggregates in an IgG1 mAb. Photoinduced cross-linked species were isolated under reducing conditions using an organic phase size exclusion chromatography (OP-SEC) method, followed by O¹⁸-labeling tryptic mapping to identify cross-linked peptides. Disulfide scrambling was observed within the IgG1 structurally conserved-intrachain cysteine-cysteine-tryptophan triads (Cys-Cys-Trp), and correlated with Trp-to-kynurenine (Kyn) photodegradation within these triads. We hypothesize that intrachain disulfides protect the proximal Trp within the Cys-Cys-Trp triads from photodegradation by enabling dissipation of Trp-absorbed UV energy via electron transfer to the disulfide bond. Finally, we propose three distinct mechanisms of photochemical degradation of monoclonal antibodies mediated by Trp residues.

中文翻译：

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结构保守的Cys-Cys-Trp三联体的光破坏导致IgG1单克隆抗体中的还原抗性加扰的链内二硫键。

ICH指南规定的光稳定性条件诱导了高度抗还原性的加扰的二硫化物，这有助于在IgG1 mAb中出现明显的不可还原聚集体。使用有机相尺寸排阻色谱法（OP-SEC），然后在O ^18中，在还原条件下分离出光诱导的交联物质-标记胰蛋白酶图谱以鉴定交联的肽。在IgG1结构保守的链内半胱氨酸-半胱氨酸-色氨酸三联体（Cys-Cys-Trp）中观察到二硫键加扰，并与这些三联体中的Trp-Kynurenine（Kyn）光降解相关。我们假设链内二硫键通过使电子吸收转移到二硫键的Trp吸收的UV能量消散，从而保护Cys-Cys-Trp三联体中的近端Trp免受光降解。最后，我们提出了由Trp残基介导的单克隆抗体的光化学降解的三种不同机制。