Besseau L, Giraud-Guille M M
Histophysique et Cytophysique-EPHE, Observatoire Océanologique de Banyuls Université, P. & M. Curie, France.
J Mol Biol. 1995 Aug 11;251(2):197-202. doi: 10.1006/jmbi.1995.0426.
Liquid crystalline assemblies occur spontaneously in highly concentrated solutions of type I acid-soluble calf skin collagen. The degree of order, identified by optical microscopy in polarized light, varies from a random distribution of molecules at low concentrations to highly organized structures as the concentration increases up to 80 mg/ml. Ultrastructural studies using classical techniques of chemical fixation are inappropriate for liquid crystalline phases due to the absence of stable links maintaining their three-dimensional order. In order to analyse the collagen liquid crystalline phases by electron microscopy the viscous preparations were stabilized under ammonia vapour. Observations of the gels in polarized light indicated that the liquid crystalline order, established at acidic pH in a sol state, persists at neutral pH in a gel state. Transmission electron microscopic observations allow us to validate the geometrical model interpreted from observations in polarizing microscopy, that is continuously twisting orientations in cholesteric phases characterized by typical series of arced patterns when viewed in oblique sections. A significant result is that the ultrastructure of the stabilized liquid crystalline collagen faithfully mimics fibrillar patterns described in vivo in extracellular matrices. This strongly supports the hypothesis that liquid crystalline properties are involved in the morphogenesis of collagen matrices.
液晶组装体在I型酸溶性小牛皮胶原蛋白的高浓度溶液中自发形成。通过偏光显微镜确定的有序程度，从低浓度下分子的随机分布到浓度增加至80毫克/毫升时高度有序的结构不等。由于缺乏维持其三维秩序的稳定连接，使用经典化学固定技术进行的超微结构研究不适用于液晶相。为了通过电子显微镜分析胶原蛋白液晶相，粘性制剂在氨蒸气下得以稳定。在偏光下对凝胶的观察表明，在酸性pH值下以溶胶状态建立的液晶秩序，在中性pH值下以凝胶状态持续存在。透射电子显微镜观察使我们能够验证从偏光显微镜观察中解释的几何模型，即在斜截面观察时，胆甾相中的连续扭曲取向以典型的弧形图案系列为特征。一个重要的结果是，稳定化的液晶胶原蛋白的超微结构忠实地模仿了体内细胞外基质中描述的纤维状图案。这有力地支持了液晶特性参与胶原蛋白基质形态发生的假说。
