CONTROL OF MEMBRANE TRANSPORT BY OSMOTIC STRESS

测量离子电池开启和关闭过程中的内部体积变化 跨膜通道，我们一直在让灌流的制剂 正渗透应激和负渗透应激。航道打通的额外工作 在渗透胁迫下，以电流-电压曲线的位移或 作为通道的开启/关闭统计中的偏差。压制和 鱿鱼巨轴突钾离子通道电导的增强 很好地对应了人们对渗透压力的预期反应。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。线粒体的电压依赖性 插入平面脂质双层的阴离子通道(VDAC)显示出体积 2到4万立方埃的变化。这些都是很大的变化 与传统的阻塞或局部门控模型不一致，但 配套车型有较大的关闭渠道空间。微型计算机 数据分析系统已进一步适用于这些测量。 缝隙结是离子直接转移的轨迹和小的 分子从一个细胞到另一个细胞。我们已(1)合并了来自 将缝隙连接分离成小泡，(2)应用密度移位技术 选择包含大开放通道的囊泡，以及(3)结合 这些通道变成了平面双层。一种特定于运输的纯化 含有通道的囊泡已经被开发出来以提高效率 重建的结果。主要有三种大小的电导变化 被人看到了。它们分别是20-30、60-70和110-130ps，每一个都有不同的 电压敏感度、不对称性和动力学程度。膜 含有多个通道，对阴离子具有选择性。

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.