Influence of polarisation analysis on buffer subtraction in biology

Protein dynamics play a vital role in biology. Quasi elastic neutron scattering is an ideal method to access these, data analysis is performed based on the assumption that the scattering spectrum is incoherent. To observe the full range of dynamical changes the proteins need to be observed in solution. This solution is usually a fully deuterated buffer, while the protein remains deuterated. It is generally assumed that while the buffer leads to a coherent contribution, which can be taken into account during data analysis by subtracting the buffer contribution from the sample spectrum. Polarised QENS experiments on LET allow for the coherent and incoherent contributions to be separated. By comparing the results from the polarised QENS experiment and the standard analysis method from unpolarised QENS it will be possible to experimentally check the current approach to data analysis.

蛋白质动力学在生物学中发挥着至关重要的作用。准弹性中子散射（Quasi Elastic Neutron Scattering, QENS）是研究这类动力学过程的理想手段，其数据分析通常基于散射光谱为非相干散射的前提假设。为完整观测蛋白质动力学变化的全范围，需在溶液环境下对蛋白质进行观测。该实验体系通常采用完全氘代缓冲液，同时保证蛋白质本身为氘代形式。学界普遍假设，缓冲液会引入相干散射贡献，而该贡献可通过在数据分析阶段从样品光谱中扣除缓冲液本底贡献的方式予以修正。在LET装置上开展的极化准弹性中子散射（Polarised Quasi Elastic Neutron Scattering, 极化QENS）实验可实现相干与非相干散射贡献的分离。通过对比极化QENS实验结果与非极化QENS的标准数据分析方法所得结果，便可从实验层面验证当前主流的数据分析范式。