Natarajan Upendra, Robbins Clarence
Molecular Modeling & Simulation Lab, Department of Chemical Engineering, Indian Institute of Technology, Madras, Chennai 600036, India.
J Cosmet Sci. 2010 Nov-Dec;61(6):467-77.
The use of computational chemistry techniques via molecular modeling software provides additional support to the hair surface model by Negri et al. (1) and refines the thickness of the 18-methyl eicosanoic acid (18-MEA) lipid layer attached by thioester linkages to an ultra-high-sulfur protein (UHSP) at 1.08 ± 0.2 nm. This value compares favorably to the thickness of that same layer from X-ray photoelectron spectroscopy (XPS) measurements by Ward et al. (2) at 1.00 ± 0.5 nm on Soxhlet-extracted wool. The model clarifies that the results of Ward et al. via XPS are not an artifact of high vacuum (3), but due to relaxation of the 18-MEA structure onto the wool protein backbone as suggested by Zahn et al. (4). In this molecular model, 18-MEA is attached to beta sheets of an UHSP via thioester linkages as suggested by Negri et al. in their 1993 study (15) and by earlier work by Evans et al. (5). The beta sheets of this model provide an intersheet spacing of 0.7 nm and a beta sheet density of 1.42 g/cm(3) compared with Allworden membrane fractions that varied from 1.39 to 1.54 g/cm(3) (6).
通过分子建模软件使用计算化学技术，为Negri等人（1）提出的毛发表面模型提供了额外支持，并精确测定了通过硫酯键连接到超高硫蛋白（UHSP）上的18 - 甲基二十烷酸（18 - MEA）脂质层的厚度为1.08±0.2纳米。该值与Ward等人（2）通过X射线光电子能谱（XPS）对索氏提取羊毛测量得到的同一层厚度1.00±0.5纳米相比更具优势。该模型表明，Ward等人通过XPS得到的结果并非高真空造成的假象（3），而是如Zahn等人（4）所指出的，是由于18 - MEA结构在羊毛蛋白主链上的松弛。在这个分子模型中，如Negri等人在其1993年的研究（15）以及Evans等人早期的工作（5）所表明的，18 - MEA通过硫酯键连接到UHSP的β折叠上。与Allworden膜组分的β折叠层间距为0.7纳米、β折叠密度为1.39至1.54克/立方厘米（6）相比，该模型的β折叠层间距为0.7纳米，β折叠密度为1.42克/立方厘米。
