Khaykovich Boris, Hossain Chintan, McManus Jennifer J, Lomakin Aleksey, Moncton David E, Benedek George B
Nuclear Reactor Laboratory, Massachusetts Institute of Technology, 138 Albany Street, Cambridge, MA 02139, USA.
Proc Natl Acad Sci U S A. 2007 Jun 5;104(23):9656-60. doi: 10.1073/pnas.0702967104. Epub 2007 May 24.
We report the results of x-ray-scattering studies of individual helical ribbons formed in multicomponent solutions of cholesterol solubilized by various surfactants. The solutions were chemically defined lipid concentrate (CDLC) and model bile. In these and many analogous multicomponent surfactant-cholesterol solutions, helical ribbons of two well defined pitch angles, namely 11 degrees and 54 degrees, are formed. We have suggested previously that this remarkable stability results from an underlying crystalline structure of the sterol ribbon strips. Using a synchrotron x-ray source, we have indeed observed Bragg reflections from individual ribbons having 11 degrees pitch angle. We have been able to deduce the parameters of the unit cell. The crystal structure of these ribbons is similar to that of cholesterol monohydrate, with the important difference that the length of the unit cell perpendicular to the cholesterol layers is tripled. We discuss possible origins for this triplication as well as the connection between the crystalline structure and the geometrical form of the helical ribbons.
我们报告了对由各种表面活性剂增溶的胆固醇多组分溶液中形成的单个螺旋带进行X射线散射研究的结果。这些溶液是化学定义的脂质浓缩物（CDLC）和模拟胆汁。在这些以及许多类似的多组分表面活性剂-胆固醇溶液中，形成了两种具有明确螺距角的螺旋带，即11度和54度。我们之前曾提出，这种显著的稳定性源于甾醇带条的潜在晶体结构。使用同步加速器X射线源，我们确实观察到了具有11度螺距角的单个带的布拉格反射。我们已经能够推导出晶胞的参数。这些带的晶体结构与一水合胆固醇的晶体结构相似，重要的区别在于垂直于胆固醇层的晶胞长度增加了两倍。我们讨论了这种三倍增加的可能起源以及晶体结构与螺旋带几何形状之间的联系。
