Laboratoire de Cristallogenèse et Cristallographie des Protéines, IBS, Institut de Biologie Structurale Jean-Pierre Ebel, CEA, CNRS, Université Joseph Fourier, 41 Rue Jules Horowitz, F-38027 Grenoble, France.
Structure. 2010 Nov 10;18(11):1410-9. doi: 10.1016/j.str.2010.09.010.
X-ray-induced chemistry modifies biological macromolecules structurally and functionally, even at cryotemperatures. The mechanisms of x-radiation damage in colored or redox proteins have often been investigated by combining X-ray crystallography with in crystallo-ultraviolet-visible spectroscopy. Here, we used Raman microspectrophotometry to follow the onset of damage in crystalline lysozyme, notably that of disulfide bond breakage. The dose-dependent Raman spectra are consistent with a kinetic model for the rupture of disulfide bonds suggesting the rapid build up of an anionic radical intermediate. This intermediate may either revert back to the oxidized state or evolve toward protonated radical species or cleaved products. The data strongly suggest that back conversion of the anionic radical is significantly accelerated by X-rays, revealing an X-ray-induced "repair" mechanism. The possibility of X-ray-induced chemical repair is an important feature to take into account when assessing radiation damage in macromolecules.
X 射线诱导的化学反应会改变生物大分子的结构和功能，即使在低温下也是如此。通过将 X 射线晶体学与晶体中紫外可见光谱学相结合，经常研究有色或氧化还原蛋白质中 X 射线辐射损伤的机制。在这里，我们使用拉曼微光谱法来跟踪结晶溶菌酶中损伤的发生，特别是二硫键断裂的情况。与二硫键断裂的动力学模型一致的剂量依赖性拉曼光谱表明，阴离子自由基中间体的快速形成。该中间体可能会返回到氧化态，或者向质子化自由基或裂解产物演变。这些数据强烈表明，X 射线会显著加速阴离子自由基的反向转化，揭示了一种 X 射线诱导的“修复”机制。在评估大分子中的辐射损伤时，考虑 X 射线诱导的化学修复的可能性是一个重要特征。
