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Implementation of a self‐consistent slab model of bilayer structure in the SasView suite
Journal of Applied Crystallography ( IF 5.2 ) Pub Date : 2021-01-22 , DOI: 10.1107/s1600576720015526
Luoxi Tan 1 , James G Elkins 2 , Brian H Davison 2 , Elizabeth G Kelley 3 , Jonathan Nickels 1
Affiliation  

Slab models are simple and useful structural descriptions which have long been used to describe lyotropic lamellar phases, such as lipid bilayers. Typically, slab models assume a midline symmetry and break a bilayer structure into three pieces, a central solvent‐free core and two symmetric outer layers composed of the soluble portion of the amphiphile and associated solvent. This breakdown matches reasonably well to the distribution of neutron scattering length density and therefore is a convenient and common approach for the treatment of small‐angle scattering data. Here, an implementation of this model within the SasView software suite is reported. The implementation is intended to provide physical consistency through the area per amphiphile molecule and number of solvent molecules included within the solvent‐exposed outer layer. The proper use of this model requires knowledge of (or good estimates for) the amphiphile and solvent molecule volume and atomic composition, ultimately providing a self‐consistent data treatment with only two free parameters: the lateral area per amphiphile molecule and the number of solvent molecules included in the outer region per amphiphile molecule. The use of this code is demonstrated in the fitting of standard lipid bilayer data sets, obtaining structural parameters consistent with prior literature and illustrating the typical and ideal cases of fitting for neutron scattering data obtained using single or multiple contrast conditions. While demonstrated here for lipid bilayers, this model is intended for general application to block copolymers, surfactants, and other lyotropic lamellar phase structures for which a slab model is able to reasonably estimate the neutron scattering length density/electron‐density profile of inner and outer layers of the lamellae.

中文翻译:

在 SasView 套件中实现双层结构的自洽平板模型

板模型是简单且有用的结构描述,长期以来一直用于描述溶致层状相,例如脂质双层。通常,板模型假定中线对称,并将双层结构分成三部分,一个无溶剂的中心核和两个由两亲物的可溶部分和相关溶剂组成的对称外层。这种分解与中子散射长度密度的分布相当匹配,因此是处理小角度散射数据的一种方便且常见的方法。这里报告了该模型在SasView软件套件中的实现。该实施的目的是通过每个两亲分子的面积和暴露于溶剂的外层中包含的溶剂分子的数量来提供物理一致性。正确使用该模型需要了解(或良好估计)两亲物和溶剂分子的体积和原子组成,最终提供仅具有两个自由参数的自洽数据处理:每个两亲物分子的侧面积和溶剂的数量每个两亲分子的外部区域包含分子。该代码的使用在标准脂质双层数据集的拟合中得到了证明,获得了与先前文献一致的结构参数,并说明了使用单一或多重对比条件获得的中子散射数据拟合的典型和理想情况。虽然此处针对脂质双层进行了演示,但该模型旨在一般应用于嵌段共聚物、表面活性剂和其他溶致层状相结构,其中平板模型能够合理地估计内部和外部的中子散射长度密度/电子密度分布片层的层数。
更新日期:2021-02-02
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