Frauenfelder Hans, Young Robert D, Fenimore Paul W
Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545;
Department of Physics, Illinois State University, Bloomington-Normal, IL 61790.
Proc Natl Acad Sci U S A. 2017 May 16;114(20):5130-5135. doi: 10.1073/pnas.1612267114. Epub 2017 May 1.
We recently introduced a model of incoherent quasielastic neutron scattering (QENS) that treats the neutrons as wave packets of finite length and the protein as a random walker in the free energy landscape. We call the model ELM for "energy landscape model." In ELM, the interaction of the wave packet with a proton in a protein provides the dynamic information. During the scattering event, the momentum [Formula: see text] is transferred by the wave packet to the struck proton and its moiety, exerting the force [Formula: see text] The resultant energy [Formula: see text] is stored elastically and returned to the neutron as it exits. The energy is given by [Formula: see text], where [Formula: see text] is the ambient temperature and [Formula: see text] ([Formula: see text] 91 K Å) is a new elastobaric coefficient. Experiments yield the scattering intensity (dynamic structure factor) [Formula: see text] as a function of [Formula: see text] and [Formula: see text] To test our model, we use published data on proteins where only thermal vibrations are active. ELM competes with the currently accepted theory, here called the spatial motion model (SMM), which explains [Formula: see text] by motions in real space. ELM is superior to SMM: It can explain the experimental angular and temperature dependence, whereas SMM cannot do so.
我们最近引入了一种非相干准弹性中子散射（QENS）模型，该模型将中子视为有限长度的波包，将蛋白质视为自由能景观中的随机漫步者。我们将该模型称为ELM，即“能量景观模型”。在ELM中，波包与蛋白质中质子的相互作用提供了动态信息。在散射事件中，动量[公式：见原文]由波包传递给被撞击的质子及其部分，施加力[公式：见原文]。产生的能量[公式：见原文]被弹性存储，并在中子离开时返回给中子。能量由[公式：见原文]给出，其中[公式：见原文]是环境温度，[公式：见原文]（[公式：见原文]91 K Å）是一个新的弹性压力系数。实验得出散射强度（动态结构因子）[公式：见原文]作为[公式：见原文]和[公式：见原文]的函数。为了测试我们的模型，我们使用已发表的关于仅热振动活跃的蛋白质的数据。ELM与当前被接受的理论（这里称为空间运动模型（SMM））竞争，SMM通过实空间中的运动来解释[公式：见原文]。ELM优于SMM：它可以解释实验角度和温度依赖性，而SMM则不能。
