Gordeliy V I, Kiselev M A
Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna, Moscow District, Russia.
Biophys J. 1995 Oct;69(4):1424-8. doi: 10.1016/S0006-3495(95)80011-1.
Neutron diffraction is an effective method for investigating model and biological membranes. Yet, to obtain accurate structural information it is necessary to use deuterium labels and much time is needed to acquire experimental data as there are a large number of diffraction reflections to register. This paper offers a way to define the hydrophobic boundary position in lipid membranes with high accuracy and for this purpose it is sufficient to take into consideration three structural factors. The method is based on modeling the density of the neutron diffraction amplitude rho(x) in the direction of the bilayer plane normal by means of a strip function, but it also takes into consideration the fact that the multiplication of the strip function amplitude rho i by the step width zi-zi-1 makes the sum of neutron scattering amplitudes of the atoms included in the step region. On the basis of the analysis of a large number of experimental data for different membranes, the effectiveness of this method in the determination of the position of hydrophilic/hydrophobic boundary is demonstrated, including the case of various rho(x) modifications in the region of polar heads and also the different phase states of membranes. However, it is shown in the present paper that the strip function model is not an adequate instrument for the determination of other structural parameters of membranes.
中子衍射是研究模型膜和生物膜的一种有效方法。然而，为了获得准确的结构信息，有必要使用氘标记，而且由于需要记录大量的衍射反射，获取实验数据需要大量时间。本文提供了一种高精度确定脂质膜中疏水边界位置的方法，为此只需考虑三个结构因素即可。该方法基于通过带状函数对双层平面法线方向上的中子衍射振幅密度rho(x)进行建模，但它也考虑到带状函数振幅rho i与步长zi - zi - 1相乘会得到步长区域内所含原子的中子散射振幅之和这一事实。基于对不同膜的大量实验数据的分析，证明了该方法在确定亲水/疏水边界位置方面的有效性，包括极性头部区域各种rho(x)变化的情况以及膜的不同相态。然而，本文表明带状函数模型并非确定膜的其他结构参数的合适工具。
