Wang Wangchen, Pan Deng, Song Yang, Liu Wenhan, Yang Lin, Huang Huey W
Department of Physics & Astronomy, Rice University, Houston, Texas 77251, USA.
Biophys J. 2006 Jul 15;91(2):736-43. doi: 10.1529/biophysj.105.080267. Epub 2006 Apr 21.
The structures of the unit cells of lipid phases that exhibit long-range crystalline order but short-range liquid-like disorder are of biological interests. In particular, the recently discovered rhombohedral phase has a unit cell containing either the structure of a membrane fusion intermediate state or that of a peptide-induced transmembrane pore, depending on the lipid composition and participating peptides. Diffraction from such systems generally presents a difficult phase problem. The existing methods of phase determination all have their limitations. Therefore it is of general interest to develop a new phasing method. The method of multi-wavelength anomalous dispersion is routinely used in protein crystallography, but the same method is difficult for lipid systems for the practical reason that the commonly used lipid samples for diffraction do not have a well-defined thickness. Here we describe a practical approach to use the multi-wavelength anomalous dispersion method for lipid structures. The procedure is demonstrated with the lamellar phase of a brominated lipid. The method is general to all phases as long as anomalous diffraction is applicable.
具有长程晶体有序但短程类似液体无序的脂质相晶胞结构具有生物学意义。特别地，最近发现的菱面体相的晶胞包含膜融合中间态结构或肽诱导的跨膜孔结构，这取决于脂质组成和参与的肽。来自此类系统的衍射通常存在困难的相位问题。现有的相位确定方法都有其局限性。因此，开发一种新的相位确定方法具有普遍意义。多波长反常色散方法在蛋白质晶体学中经常使用，但对于脂质系统来说，同样的方法却很困难，实际原因是用于衍射的常用脂质样品没有明确界定的厚度。在这里，我们描述了一种将多波长反常色散方法用于脂质结构的实用方法。该过程通过一种溴化脂质的层状相进行了演示。只要反常衍射适用，该方法对所有相都是通用的。
