Université de Lyon, CNRS, Université Claude Bernard Lyon 1, Institut Lumière Matière UMR 5306, 69622, Villeurbanne, France.
Université de Lyon, CNRS, Université Claude Bernard Lyon 1, ENS de Lyon, Institut des Sciences Analytiques UMR 5280, 69100, Villeurbanne, France.
J Am Soc Mass Spectrom. 2018 Sep;29(9):1826-1834. doi: 10.1007/s13361-018-1989-8. Epub 2018 Jun 12.
The nonapeptide oxytocin (OT) is used as a model sulfur-containing peptide to study the damage induced by vacuum UV (VUV) radiations. In particular, the effect of the presence (or absence in reduced OT) of oxytocin's internal disulfide bridge is evaluated in terms of photo-fragmentation yield and nature of the photo-fragments. Intact, as well as reduced, OT is studied as dianions and radical anions. Radical anions are prepared and photo-fragmented in two-color experiments (UV + VUV) in a linear ion trap. VUV photo-fragmentation patterns are analyzed and compared, and radical-induced mechanisms are proposed. The effect of VUV is principally to ionize but secondary fragmentation is also observed. This secondary fragmentation seems to be considerably enabled by the initial position of the radical on the molecule. In particular, the possibility to form a radical on free cysteines seems to increase the susceptibility to VUV fragmentation. Interestingly, disulfide bridges, which are fundamental for protein structure, could also be responsible for an increased resistance to ionizing radiations. Graphical Abstract.
神经九肽催产素（OT）被用作含硫肽的模型，以研究真空紫外（VUV）辐射引起的损伤。特别是，评估了 OT 内部二硫键的存在（或还原 OT 中的不存在）对光致断裂产率和光碎片性质的影响。完整的和还原的 OT 都被作为二价阴离子和自由基阴离子来研究。自由基阴离子通过在直线离子阱中进行双色实验（UV+VUV）来制备和光致断裂。分析和比较 VUV 光致断裂模式，并提出自由基诱导的机制。VUV 的作用主要是电离，但也观察到二次碎裂。这种二次碎裂似乎在很大程度上取决于自由基在分子上的初始位置。特别是，在游离半胱氨酸上形成自由基的可能性似乎增加了对 VUV 断裂的敏感性。有趣的是，对蛋白质结构至关重要的二硫键也可能导致对电离辐射的抵抗力增加。
