Johnson Research Foundation, School of Medicine, University of Pennsylvania, 19104, Philadelphia, Pennsylvania.
J Membr Biol. 1970 Dec;2(1):235-51. doi: 10.1007/BF01869862.
Cytochromec added during the formation of lecithin-cardiolipin liquid crystals in 0.015M KCl is readily bound. After successive washings with 0.15M KCl, only about 50% of this bound cytochromec is removed. The remaining cytochromec is resistant to further salt extraction, and the amount of this cytochromec that is bound varies with the concentration of added cytochromec to a maximum binding ratio of 1∶70, mole ratio cytochromec to phospholipid. This binding appears to be electrostatic; it is competitively inhibited by increasing the initial molarity of KCl from 0.015 to 0.10M. Binding of cytochromec is insignificant in the absence of cardiolipin, and is affected by varying the pH. Electron microscope studies of osmium tetroxide-stained thin sections show that the liquid crystals consist of vesicles, each of which contains a large number of concentric, alternating light and dense lines. The dense lines have been identified by other workers with the polar head groups of the phospholipids on the surface of a bilayer, and the light area represents the hydrophobic interior. The addition of cytochromec causes an average decrease in the number of lines per vesicle. It increases the center-to-center distance between two neighboring light or dense lines and the width of the dense lines. On the basis of this evidence and electrostatic binding, it is concluded that cytochromec is binding on the polar surfaces of the phospholipid bilayers comprising the liquid crystalline vesicles.
在 0.015M KCl 中形成的卵磷脂-心磷脂液晶中添加细胞色素 c 后很容易被结合。用 0.15M KCl 连续洗涤后，只有约 50%的结合细胞色素 c 被去除。其余的细胞色素 c 抵抗进一步的盐提取，并且结合的细胞色素 c 的量随添加的细胞色素 c 的浓度变化而变化，最大结合比为 1∶70，摩尔比细胞色素 c 与磷脂。这种结合似乎是静电的；它被竞争性抑制，方法是将初始 KCl 的摩尔浓度从 0.015M 增加到 0.10M。在没有心磷脂的情况下，细胞色素 c 的结合可以忽略不计，并且受 pH 值变化的影响。四氧化锇染色的超薄切片电子显微镜研究表明，液晶由囊泡组成，每个囊泡包含大量同心、交替的亮线和暗线。其他研究人员已经将暗线鉴定为双层磷脂表面的极性头部基团，而亮区代表疏水区。添加细胞色素 c 会导致每个囊泡中的线数平均减少。它增加了两个相邻亮线或暗线之间的中心到中心距离和暗线的宽度。根据这些证据和静电结合，可以得出结论，细胞色素 c 结合在构成液晶囊泡的磷脂双层的极性表面上。
