CONTROL OF MEMBRANE TRANSPORT BY OSMOTIC STRESS

我们测量离子泵打开和关闭期间的内部体积变化 通过向跨膜通道的两侧添加不渗透的溶质， 含通道膜。 渠道开放的额外工作， 渗透应力被测量为电流-电压曲线的偏移或作为 通道的开放/闭合统计中的偏差。 我们正在测量体积 下面提到的渠道变化。 我们开发了一种新的脂质 双层室，以确保粘性溶液的良好混合， 湍流导致改进的膜稳定性。 微机数据 分析系统已经适应了这些测量。 线粒体电压依赖性阴离子通道（VDAC）插入到 平面脂质双层显示出2万至4万立方的体积变化 埃。 这是一个与传统阻塞不一致的大变化 但支持的模型与主要关闭的 通道空间 此外，VDAC作为细胞内的 建议使用稳压器。 差距结是离子直接迁移的场所， 从一个细胞到另一个细胞。 为了测量体积的变化， 连接成平面膜。 通道具有许多 连接通道成功地结合到平面膜中。 含有通道的囊泡的转运特异性纯化已经被发现。 以提高重组的效率。 我们期望 区分两种已发表的基于间隙差距结沟道的模型 根据我们的体积变化测量。

We measure the internal volume change during opening and closing of ionic transmembrane channels by adding impermeant solutes to both sides of the channel-containing membrane. 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. We are measuring volume changes in the channels mentioned below. We have developed a new lipid bilayer chamber to ensure good mixing of viscous solutions and decreased turbulence leading to improved membrane stability. A microcomputer data analysis system has been adapted for these measurements. The mitochondrial voltage-dependent anion channel (VDAC) inserted into planar lipid bilayers shows a volume change of 20 to 40 thousand cubic angstroms. This is a large change inconsistent with traditional blocking of local gating models but supporting models with major closure of the channel space. In addition, the role of VDAC as an intracellular osmoregulator is suggested. The gap junction is the locus of direct transfer of ions and small molecules from cell to cell. To measure volume changes we reconstitute junctions into planar membranes. Channels with many of the properties of junctional channels were successfully incorporated into planar membranes. A transport-specific purification of vesicles containing channels has been developed to improve the efficiency of the reconstitution. We expect to distinguish between two published models of the gap junction channel based upon our volume-change measurements.