Calculations of flow-induced orientation distributions for analysis of linear dichroism spectroscopy
Calculations of flow-induced orientation distributions for analysis of linear dichroism spectroscopy
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DOI：
10.1039/c3sm27419e
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发表时间：
2013-01-01
期刊：
影响因子：
3.4
通讯作者：
Rodger, Alison
中科院分区：
文献类型：
--
作者：
McLachlan, James R. A.;Smith, David J.;Rodger, Alison
涉及流动导向样品和偏振光的光谱技术，如线性二色性(LD)，在探测生物大分子组装方面正变得越来越有用。然而，信号的大小以及在某些情况下光谱的形状取决于样品中分子取向的分布。尽管在稀释和半稀释悬浮力学的建模方面取得了很大进展，但这些理论对实践LD的社区的影响微乎其微。我们使用一个结合布朗效应和旋转的模型进行计算，该模型结合了刚性棒状颗粒稀薄悬浮液的稳态剪切流动。我们计算了三种生物分子组件：M13噬菌体、长度明确的DNA分子和FtsZ原丝取向分布的随时间变化的概率密度函数。我们的计算允许我们直接计算(而不是从实验中推断)此类组装的LD取向参数S。该模型的结果与M13噬菌体的实验结果一致，并使我们能够对合理较短的DNA分子对S进行经验估计。在分析FtsZ聚合过程的粒度分布时，我们发现该模型的结果有助于我们对该过程的理解。
Spectroscopic techniques involving flow-oriented samples and polarised light, such as linear dichroism (LD), are becoming increasingly useful to probe biomacromolecular assemblies. However, the magnitude of the signal and in some cases the shape of the spectrum are dependent on the distribution of the orientations of the molecules in the sample. Despite great progress in the modelling of dilute and semi-dilute suspension mechanics, these theories have had remarkably little impact on the community practising LD. We perform calculations with a model combining Brownian effects and rotations in a steady shear flow of a dilute suspension of rigid, rodlike particles. We calculate the time-dependent probability density functions for the orientation distributions of three biomolecular assemblies: M13 bacteriophage, DNA molecules of well-defined length, and FtsZ protofilaments. Our calculations allow us to compute directly (rather than infer from experiment) the LD orientation parameter, S, for such assemblies. The results from the model are consistent with experiment for M13 bacteriophage and allow us to estimate S empirically for reasonably short DNA molecules. In analysing the particle size distribution for the process of FtsZ polymerisation, we find that results from the model aid our understanding of the process.