Zeller Dominik, Tan Pan, Hong Liang, Di Bari Daniele, Garcia Sakai Victoria, Peters Judith
University Grenoble Alpes, LiPhy, CNRS, F-38000 Grenoble, France and Institut Laue Langevin, F-38042 Grenoble Cedex 9, France.
School of Physics and Astronomy and Institute of Natural Sciences, Shanghai Jiao Tong University, Shanghai 200240, China.
Phys Rev E. 2020 Mar;101(3-1):032415. doi: 10.1103/PhysRevE.101.032415.
We present a study comparing atomic motional amplitudes in calcium rich and depleted alpha-lactalbumin. The investigations were performed by elastic incoherent neutron scattering (EINS) and molecular dynamics (MD) simulations. As the variations were expected to be very small, three different hydration levels and timescales (instrumental resolutions) were measured. In addition, we used two models to extract the mean square displacements (MSDs) from the EINS data, one taking into account the motional heterogeneity of the MSD. At a timescale of several nanoseconds, small differences in the amplitudes between the calcium enriched and depleted alpha-lactalbumin are visible, whereas at lower timescales no changes can be concluded within the statistics. The results are compared to MD simulations at 280 and 300 K by extracting the MSDs of the trajectories in two separate ways: first by direct calculation, and second by a virtual neutron experiment using the same models as for the experimental data. We show that the simulated data give qualitatively similar results as the experimental data but quantitatively there are differences. Furthermore, the distribution of the MSDs in the simulations suggests that the inclusion of heterogeneity is reasonable for alpha-lactalbumin, but a bi-or trimodal approach may be sufficient.
我们展示了一项比较富含钙和贫钙α-乳白蛋白中原子运动幅度的研究。研究通过弹性非相干中子散射（EINS）和分子动力学（MD）模拟进行。由于预计变化非常小，因此测量了三种不同的水合水平和时间尺度（仪器分辨率）。此外，我们使用两种模型从EINS数据中提取均方位移（MSD），其中一种考虑了MSD的运动异质性。在几纳秒的时间尺度上，可以看到富含钙和贫钙α-乳白蛋白之间的幅度存在微小差异，而在较低时间尺度上，根据统计结果无法得出变化结论。通过两种不同方式提取轨迹的MSD，将结果与280 K和300 K下的MD模拟进行比较：第一种是直接计算，第二种是使用与实验数据相同的模型进行虚拟中子实验。我们表明，模拟数据在定性上与实验数据相似，但在定量上存在差异。此外，模拟中MSD的分布表明，考虑异质性对于α-乳白蛋白是合理的，但双模式或三模式方法可能就足够了。
