Biomolecular cryocrystallography: Structural changes during flash-cooling
Biomolecular cryocrystallography: Structural changes during flash-cooling
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DOI：
10.1073/pnas.0308315101
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发表时间：
2004-04-06
影响因子：
11.1
通讯作者：
Halle, B
中科院分区：
文献类型：
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作者：
Halle, B
为了最大限度地减少辐射损伤，生物大分子的晶体结构通常在快速冷却至低温（比正常生理范围低约 150-200 K）后确定。此类结构的生物学相关性依赖于这样的假设：快速冷却足够快，能够在室温平衡状态下动力学捕获大分子和相关溶剂。为了测试这个假设，我们使用二态模型来计算典型蛋白质晶体快速冷却期间预期的结构变化。分析表明，快速冷却的蛋白质晶体中的许多自由度在接近 200 K 的温度下被淬灭，其中局部构象和缔合平衡可能强烈地向低焓状态转变。这种冷冻产物对于强溶剂耦合过程来说应该是最重要的，例如非极性空腔和表面区域的水合、溶剂暴露侧链的构象转换以及弱配体结合。这里考虑的模型中出现的动态猝灭也可以使与蛋白质中原子波动相关的玻璃化转变合理化。
To minimize radiation damage, crystal structures of biological macromolecules are usually determined after rapid cooling to cryogenic temperatures, some 150-200 K below the normal physiological range, The biological relevance of such structures relies on the assumption that flash-cooling is sufficiently fast to kinetically trap the macromolecule and associated solvent in a room-temperature equilibrium state. To test this assumption, we use a two-state model to calculate the structural changes expected during rapid cooling of a typical protein crystal. The analysis indicates that many degrees of freedom in a flash-cooled protein crystal are quenched at temperatures near 200 K, where local conformational and association equilibria may be strongly shifted toward low-enthalpy states. Such cryoartifacts should be most important for strongly solvent-coupled processes, such as hydration of nonpolar cavities and surface regions, conformational switching of solvent-exposed side chains, and weak ligand binding. The dynamic quenching that emerges from the model considered here can also rationalize the glass transition associated with the atomic fluctuations in the protein.