Matsuo Tatsuhito
Institute for Quantum Life Science, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Chiba, 263-8555, Japan.
Phys Chem Chem Phys. 2023 Apr 26;25(16):11586-11600. doi: 10.1039/d3cp00409k.
Thermal fluctuations of proteins at the ps-ns timescales are important for their functions and have extensively been studied using quasi-elastic neutron scattering (QENS). In general, the QENS spectra of proteins are analyzed in terms of two populations of atoms, , the immobile fraction of atoms, the motions of which are too slow to be resolved within the instrumental energy resolution employed, and the mobile fraction of atoms, from which the average amplitude and frequency of protein atomic motions are characterized. On the other hand, it has been shown using molecular dynamics simulations that atomic motions are gradually enhanced as going from the protein core to the protein surface. Therefore, it is essential to further deconvolute the mobile fraction of atoms to study in detail the dynamical behavior of proteins. Here, an improved analytical model using QENS to deconvolute the mobile fraction of atoms into two populations of atoms, , atoms with high mobility (HM atoms) and those with low mobility (LM atoms), is proposed. It was found that both the HM atoms and the LM atoms showed gradually enhanced dynamics with an increase in temperature even though any temperature-dependent terms are not included in the model. The presented model yields physically reasonable values for dynamical parameters and hence its future application will be useful to understand the molecular mechanism of various protein functions where atoms with higher mobility on or close to the protein surface play a crucial role.
蛋白质在皮秒到纳秒时间尺度上的热涨落对其功能很重要，并且已经使用准弹性中子散射（QENS）进行了广泛研究。一般来说，蛋白质的QENS光谱是根据两类原子群体来分析的，一类是不动原子部分，其运动太慢，在所采用的仪器能量分辨率范围内无法分辨；另一类是可动原子部分，据此可以表征蛋白质原子运动的平均振幅和频率。另一方面，分子动力学模拟表明，从蛋白质核心到蛋白质表面，原子运动逐渐增强。因此，进一步对可动原子部分进行解卷积，以详细研究蛋白质的动力学行为至关重要。在此，提出了一种改进的分析模型，利用QENS将可动原子部分解卷积为两类原子群体，即高迁移率原子（HM原子）和低迁移率原子（LM原子）。结果发现，即使模型中不包含任何与温度相关的项，HM原子和LM原子的动力学都会随着温度升高而逐渐增强。所提出的模型给出了动力学参数的合理物理值，因此其未来应用将有助于理解各种蛋白质功能的分子机制，其中蛋白质表面或靠近蛋白质表面的高迁移率原子起着关键作用。
