海藻糖生物保护环境中水合蛋白质的高压动力学
High pressure dynamics of hydrated protein in bio-protective trehalose environment
摘要：
利用准弹性中子散射（QENS）研究了溶菌酶蛋白粉在氘代$α$、$α$ -海藻糖环境中的动力学行为。目的是通过将研究结果与不含海藻糖的参考研究结果进行比较，评估海藻糖对生物分子的气压保护益处。虽然无海藻糖的蛋白质（水合至$d_{D_2O}\simeq$ 40重量%）作为一个整体的均方位移通过增加压力而降低，但在皮秒（ps）至纳秒（ns）时间范围内的实际可观察到的弛豫动力学在很大程度上保持不受压力影响-高达2.78（2）Kbar的最大研究压力。我们的观察结果与蛋白质是否与氘代糖混合无关。这表明在大气压下水合蛋白质的构象状态保持不变的静水压力，低于2.78 Kbar。我们还发现，QENS的反应是完全恢复后，环境压力条件恢复。圆二色性和中子衍射测量证实，蛋白质的结构完整性是保守的，并保持完整，压力释放后。然而，我们观察到的准弹性中子（QENS）响应的温度从290 K降低到230 K，在这两种情况下，我们使用Kohlrausch-Williams-Watts（KWW）拉伸指数模型参数化明显变窄。只有在仪器的可访问时间窗口上不动的质子的分数，称为弹性非相干结构因子或（EISF），对压力非常敏感，随着压力的增加，仅略微但系统地增加。
英文摘要：
We present a pressure dependence study of the dynamics of lysozyme protein powder immersed in deuterated $α$,$α$-trehalose environment via quasi-elastic neutron scattering (QENS). The goal is to assess the baro-protective benefits of trehalose on bio-molecules by comparing the findings with those of a trehalose-free reference study. While the mean-square displacement of the trehalose-free protein (hydrated to $d_{D_2O}\simeq$40 w\%) as a whole, is reduced by increasing pressure, the actual observable relaxation dynamics in the pico-(ps) to nano-seconds (ns) time range remains largely unaffected by pressure - up to the maximum investigated pressure of 2.78(2) Kbar. Our observation is independent of whether or not the protein is mixed with the deuterated sugar. This suggests that the hydrated protein's conformational states at atmospheric pressure remain unaltered by hydrostatic pressures, below 2.78 Kbar. We also found the QENS response to be totally recoverable after ambient pressure conditions are restored. Circular dichroism and neutron diffraction measurements confirm that the protein structural integrity is conserved and remains intact, after pressure is released. We observe however a clear narrowing of the quasi-elastic neutron (QENS) response as the temperature is decreased from 290 K to 230 K in both cases, which we parametrize using the Kohlrausch-Williams-Watts (KWW) stretched exponential model. Only the fraction of protons that are immobile on the accessible time window of the instrument, referred to as the elastic incoherent structure factor or (EISF) is observably sensitive to pressure, increasing only marginally but systematically with increasing pressure.
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