Free radical mediated x-ray damage of model membranes
Free radical mediated x-ray damage of model membranes
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DOI：
10.1016/s0006-3495(96)79787-4
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发表时间：
1996-05-01
影响因子：
3.4
通讯作者：
Caffrey, M
中科院分区：
文献类型：
--
作者：
Cheng, AC;Caffrey, M
同步加速器衍生的x射线对水性磷脂分散体的破坏作用已被评估。利用时间分辨x射线衍射和损伤产物的色谱分析，定量分析了脂质水化程度、磷脂化学结构、中间相特性、水介质组成和入射通量对损伤严重程度和进展的影响。辐照过程中产生的自旋捕获中间体的电子自旋共振测量表明这是一个自由基介导的过程。令人惊讶的是，在水胁迫条件下制备层状相时，x射线衍射显示的辐射损伤效应是难以察觉的，尽管无论水合水平如何，x射线诱导的脂质化学分解都会发生。在研究的完全水合的脂质系统中，饱和二酰基磷脂酰胆碱比酯和醚连接的磷脂酰乙醇胺和醚连接的磷脂酰胆碱对辐射损伤最敏感。在分散介质中加入缓冲液或无机盐对减少损伤发展只有很小的作用。当x射线束强度变化15倍时，发现了一个小的反向剂量率效应。这些结果有助于我们理解辐射损伤的机制，使我们认识到在评估生物材料的辐射敏感性时监测结构和成分的重要性，并有助于制定消除或减少由于越来越重要的x射线源——同步辐射造成的损伤严重程度的策略。由于损伤被证明是自由基介导的，这些结果对细胞中与年龄相关的自由基积累以及这些自由基如何损害膜完整性，最终导致细胞死亡具有重要意义。
The damaging effects of synchrotron-derived x rays on aqueous phospholipid dispersions have been evaluated. The effect of degree of lipid hydration, phospholipid chemical structure, mesophase identity, aqueous medium composition, and incident flux on the severity and progress of damage was quantified using time-resolved x-ray diffraction and chromatographic analysis of damage products. Electron spin resonance measurements of spin-trapped intermediates generated during irradiation suggest a free radical-mediated process. Surprisingly, radiation damage effects revealed by x-ray diffraction were imperceptible when the lamellar phases were prepared under water-stressed conditions, despite the fact that x-ray-induced chemical breakdown of the lipid occurred regardless of hydration level, Of the fully hydrated lipid systems studied, saturated diacyl-phosphatidylcholines were most sensitive to radiation damage compared to the ester- and ether-linked phosphatidylethanolamines and the ether-linked phosphatidylcholines. The inclusion of buffers or inorganic salts in the dispersing medium had only a minor effect in reducing damage development. A small inverse dose-rate effect was found when the x-ray beam intensity was changed 15-fold. These results contribute to our understanding of the mechanism of radiation damage, to our appreciation of the importance of monitoring both structure and composition when evaluating biomaterials radiation sensitivity, and to the development of strategies for eliminating or reducing the severity of damage due to an increasingly important source of x rays, synchrotron radiation. Because damage is shown to be free radical mediated, these results have an important bearing on age-related accumulation of free radicals in cells and how these might compromise membrane integrity, culminating in cell death.