Han B G, Wolf S G, Vonck J, Glaeser R M
Graduate Group in Biophysics, University of California, Berkeley 94720.
Ultramicroscopy. 1994 Jul;55(1):1-5. doi: 10.1016/0304-3991(94)90073-6.
Imperfect specimen flatness can be a significant limitation in the application of electron crystallography to high-resolution structure analysis of biological macromolecules. We now report that the choice of solid carbon stock that is used to make evaporated carbon films can have a very great effect on the preparation of flat specimens of glucose-embedded purple membrane. The degree of purity of the carbon does not seem to be the controlling factor, and other likely factors such as the type of mica used as a substrate, the evaporation apparatus used (and its limiting vacuum), and the use of a continuous versus an interrupted evaporation protocol do not have a discernible influence. The physical or chemical basis for the observed differences in specimen flatness is still unknown; however, the important conclusion that we can communicate at this point is that the choice of evaporating material does have a major effect on the flatness of purple membrane, the specimen used here. The implication is that different sources of carbon stock should be tried whenever difficulty is encountered in the preparation of suitably flat specimens of biological macromolecules.
在将电子晶体学应用于生物大分子的高分辨率结构分析时，样品平整度欠佳可能是一个重大限制因素。我们现在报告，用于制作蒸发碳膜的固体碳源的选择，对嵌入葡萄糖的紫膜平整样品的制备可能会产生非常大的影响。碳的纯度似乎不是控制因素，其他可能的因素，如用作基底的云母类型、所使用的蒸发设备（及其极限真空度），以及采用连续蒸发协议还是间断蒸发协议，都没有明显影响。样品平整度差异背后的物理或化学基础仍不明确；然而，我们目前能够传达的重要结论是，蒸发材料的选择确实对紫膜（本文所用样品）的平整度有重大影响。这意味着，每当在制备生物大分子的合适平整样品时遇到困难，都应该尝试不同来源的碳源。
