College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China.
J Phys Chem A. 2010 Feb 18;114(6):2376-83. doi: 10.1021/jp910624z.
The structure of the water chain in the 8 x cyclo-(WL)(4) peptide nanotube embedded in the POPE lipid bilayer is studied by molecular dynamics simulations. The distribution profiles of water molecules along the nanotube axis proposes a wavelike pattern of the water chain in the nanotube, arraying in the form of a 1-2-1-2 file, in contrast to the single file in other nanochannels studied widely. Cylindrical distribution functions of water at different zones and potential of mean force of a water molecule along the axis suggest that the primary reason for forming the water-chain pattern is steric constraints. A novel hydrogen bond network in the nanotube is present such that each water in the alpha-plane zones forms two hydrogen bonds (as a donor) with the two water molecules in the adjacent midplane zone, and each water molecule in the midplane zones forms one hydrogen bond with the water molecule in the adjacent alpha-plane zone and a poor hydrogen bond with the carbonyl groups in the nanotube. Strong orientations of the water dipoles near the two opening ends pointing to the opposite directions are found, and the potential energy of a water O or H atom along the axis is explored to explain the water dipole orientations' reversing in the nanotube. Defects of the hydrogen bond network exist in the central gaps of the cyclic peptide nanotube.
在 POPE 脂质双层中嵌入的 8 x 环-(WL)(4) 肽纳米管中的水链结构通过分子动力学模拟进行了研究。水分子沿纳米管轴的分布曲线提出了纳米管中水链的波动模式，以 1-2-1-2 文件的形式排列，与广泛研究的其他纳米通道中的单文件形成对比。不同区域的水的圆柱分布函数和水分子沿轴的平均力势能表明，形成水链模式的主要原因是空间位阻。纳米管中存在新颖的氢键网络，使得 alpha 平面区域中的每个水分子都与相邻中间平面区域中的两个水分子形成两个氢键（作为供体），中间平面区域中的每个水分子都与相邻 alpha 平面区域中的水分子形成一个氢键，与纳米管中的羰基形成一个弱氢键。在两个开口端附近发现了强烈指向相反方向的水分子偶极的取向，并且沿轴探索了水分子 O 或 H 原子的势能，以解释纳米管中水分子偶极的反转。在环状肽纳米管的中心间隙中存在氢键网络的缺陷。
