Department of Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia.
J Mol Graph Model. 2012 Mar;33:52-60. doi: 10.1016/j.jmgm.2011.11.004. Epub 2011 Dec 6.
The structure of helices within proteins is often distorted from the ideal linear topology. Curvature of the helix axis can be measured by determining the radius of a circle fit to the axis. Described here is a method of defining a curved path that places backbone atoms (usually Cα) equidistantly from the path. The variance in the distance of backbone atoms from the helix axis is minimised to produce the parametric equations that describe the intersection of a sphere and a plane. The geometric properties of the helix (including helix radius, radius of curvature, and pitch) can be readily obtained from these equations. The approach is applicable to any form of helix, can use any atom in the peptide to determine the axis, can be applied to any polypeptide including mixed α/β peptides, and does not rely on a regular spacing of peptide monomers in the polypeptide chain.
蛋白质中的螺旋结构常常偏离理想的线性拓扑。可以通过确定与轴拟合的圆的半径来测量螺旋轴的曲率。这里描述了一种定义弯曲路径的方法，该方法使骨干原子（通常为 Cα）等距于该路径。通过最小化骨干原子与螺旋轴之间的距离变化来生成描述球体与平面相交的参数方程。可以从这些方程中轻松获得螺旋的几何性质（包括螺旋半径、曲率半径和螺距）。该方法适用于任何形式的螺旋，可以使用肽中的任何原子来确定轴，可以应用于任何多肽，包括混合的α/β 多肽，并且不依赖于多肽链中肽单体的规则间隔。
