CONTROL OF MEMBRANE TRANSPORT BY OSMOTIC STRESS

测量离子泵打开和关闭过程中的内部体积变化 跨膜通道，我们一直在进行灌注制剂， 正、负渗透胁迫。 渠道开放的额外工作 在渗透胁迫下的电压变化被测量为电流-电压曲线的偏移，或者 作为通道的开/闭统计中的偏差。 抑制和 鱿鱼巨轴突钾通道电导的增强 很好地对应于人们对渗透压的预期反应。 数据 不适合简单的阻塞模型。 推断的通道音量具有 上限为1300立方埃。 线粒体电压依赖性 阴离子通道（VDAC）插入平面脂质双层显示体积 2万到4万立方埃的变化。 这些都是巨大的变化 与传统的阻塞或局部选通模型不一致， 配套车型主要有封闭式的通道空间。 微型计算机 数据分析系统已进一步适用于这些测量。 差距结是离子直接迁移的场所， 从一个细胞到另一个细胞。 我们（1）将材料从 分离缝隙连接形成囊泡，（2）应用密度漂移技术 选择含有大的开放通道的囊泡，和（3）掺入 这些通道变成平面双层。 一种转运特异性纯化 已经开发了含有通道的囊泡以提高效率 的重组。 主要有三种电导变化 被人看见了 它们分别为20-30、60-70和110-130 pS，各自具有不同的 电压灵敏度、不对称性和动力学的程度。 膜 含有几个通道的阴离子选择性。

To measure the internal volume change during opening and closing of ionic transmembrane channels, we have been subjecting perfused preparations to positive and negative osmotic stress. The extra work of channel opening under osmotic stress is measured as a shift in the current-voltage curve or as a bias in the open/closed statistics of a channel. Suppression and enhancement of potassium channel conductance in the squid giant axon correspond nicely to the response one expects to osmotic stress. The data do not fit a simple blocking model. The channel volume inferred has an upper bound of 1300 cubic angstroms. The mitochondrial voltage-dependent anion channel (VDAC) inserted into planar lipid bilayers shows a volume change of 20 to 40 thousand cubic angstroms. These are large changes inconsistent with traditional blocking or local gating models but supporting models with major closure of the channel space. A microcomputer data analysis system has been further adapted for these measurements. The gap junction is the locus of direct transfer of ions and small molecules from cell to cell. We have (1) incorporated material from isolated gap junctions into vesicles, (2) applied a density shift technique to select vesicles containing large open channels, and (3) incorporated those channels into planar bilayers. A transport-specific purification of vesicles containing channels has been developed to improve the efficiency of the reconstitution. Predominantly three sizes of conductance changes were seen. They were 20-30, 60-70, and 110-130 pS, each having different degrees of voltage sensitivity, asymmetry, and kinetics. Membranes containing several channels were anion selective.