High molecular weight (HMW) dissolved organic nitrogen (DON), especially proteinaceous materials, can persist in the deep ocean and sediment. How these materials, despite the parent source being considered labile, are transformed to be resistant to biodegradation is not yet fully understood. By conducting photo-oxidation experiments on model proteins (fetuin, cytochrome c, bovine serum albumin, and lectin) in artificial seawater, our results revealed that photo-oxidation can induce cross-linking of proteins, resulting in a change in the refractory nature of proteins and aggregation. The formation of higher molecular weight products compared to the native proteins, with simultaneously increased carbonyl content, was observed by gel electrophoresis (SDS-PAGE). The model proteins ultimately became more resistant to proteolysis. The addition of reactive oxygen species (i.e. H₂O₂ and •OH) accelerated the observed transformations. This study demonstrates that photo-oxidation can transform labile proteinaceous materials into refractory matter, providing a novel mechanism for the preservation of HMW DON in the ocean.

高分子量（HMW）溶解的有机氮（DON），尤其是蛋白质类物质，可以持续存在于深海和沉积物中。尽管母本来源不稳定，但如何将这些材料转化为抗生物降解的方法尚未完全了解。通过对模型蛋白（胎蛋白，细胞色素c（牛血清白蛋白和凝集素）在人造海水中的结果，我们的研究结果表明，光氧化可以诱导蛋白质的交联，从而导致蛋白质的耐火性和聚集性发生变化。通过凝胶电泳（SDS-PAGE）观察到与天然蛋白质相比，形成了更高分子量的产物，同时羰基含量增加。模型蛋白质最终变得对蛋白水解更具抗性。加入活性氧（即H ₂ O ₂和•OH）可加速观察到的转变。这项研究表明，光氧化可以将不稳定的蛋白质物质转化为难熔物质，为在海洋中保存HMW DON提供了新的机制。