Wallach D F, Low D A, Bertland A V
Proc Natl Acad Sci U S A. 1973 Nov;70(11):3235-9. doi: 10.1073/pnas.70.11.3235.
The circular dichroism of hypothetical, water-filled, spherical shells, 75-3500 nm in radius, with walls 7.5 nm thick, composed of poly(L-lysine) in various conformational proportions, and suspended in water, were computed from the known optical properties of this polypeptide by classical general light-scattering theory (Mie theory). Comparison of the computed curves of circular dichroism spectra with those of diverse membranes reveals large discrepancies below 215 nm and shows that light scattering does not adequately account for the optical activity of membranes containing appreciable proportions of nonhelical conformation. However, turbidity effects can explain the anomalies of membrane optical rotatory dispersion near 233 nm, if not uniquely so. We conclude that the optical activity of neither most soluble proteins nor membrane proteins can provide accurate conformational information when synthetic polypeptides are used as standards and list the reasons for this argument. We also show that present techniques to "correct" membrane optical activity are likely to produce additional artifact.
利用经典的广义光散射理论（米氏理论），根据这种多肽已知的光学性质，计算了半径为75 - 3500纳米、壁厚度为7.5纳米、由处于各种构象比例的聚（L - 赖氨酸）组成并悬浮于水中的假设性充水球形壳的圆二色性。将计算得到的圆二色光谱曲线与各种膜的曲线进行比较，发现在215纳米以下存在很大差异，这表明光散射不能充分解释含有相当比例非螺旋构象的膜的光学活性。然而，浊度效应可以解释膜的旋光色散在233纳米附近的异常现象，即便不是唯一的解释。我们得出结论，当使用合成多肽作为标准时，大多数可溶性蛋白质和膜蛋白的光学活性都不能提供准确的构象信息，并列出了这一观点的理由。我们还表明，目前用于“校正”膜光学活性的技术可能会产生额外的假象。
