MECHANISMS OF IONIC CHANNEL ACTIVITY

离子通道是跨越细胞的蛋白质大分子 膜。它们打开和关闭，或关闭毛孔，控制 离子通过膜的通量，因此，膜 潜力。拟议研究的长期目标是 以确定离子通道的门控机制。去工作 为了实现这一目标，将从单个离子记录电流 采用膜片钳技术的通道，并通过 电脑。要研究的通道是大电导 钙激活钾通道(BK通道)与FAST C_1 通道，取自哺乳动物骨骼的膜 在组织培养中生长的肌肉细胞。七个具体项目将 将进行：(1)确定浇注动力学是否 离子通道最好用具有离散状态的模型来描述 状态之间的恒定转移率(马尔科夫模型) 或者通过具有状态连续体和分形标度的模型 (分形模型)；(2)确定短暂中断是否 (闪烁)通常在流经单个电流的情况下观察到 航道完全或部分关闭引起的航道； 实施一种确定动态浇注的先进方法 机构，它使用了所有非冗余的动力 单通道电流记录中的信息 考虑到有限的时间分辨率和 当前记录。该方法使用计算机模拟来 对于给定的浇口机构，计算二维 相邻打开和关闭间隔持续时间的分布， 然后与实验分布进行比较。这 将采用先进的方法确定：(4)稳态 快C1通道的选通机构；(5)通过该机构 电压调节快通道的活动；(6)钙- BK正常模式的激活门控机构 通道；以及(7)改变了另一个通道的门控机构 BK频道的模式。在每种情况下，最有可能的门控 机构将根据运动方案来定义，该方案 指示：打开和关闭状态的数量，转换 州与州之间的通道，能源障碍 转换，以及如何通过电压调制通道活动 或钙引起能量屏障高度的变化。 表征离子通道是迈向 了解两种正常肌肉功能的分子基础 以及那些肌肉疾病，在数量和/或缺陷上 还涉及到离子通道的功能。曾经的常态 通道的特征，将有可能确定是否 它们的数量和/或功能在疾病状态下会发生变化。

Ion channels are large protein macromolecules which span cell membranes. They open and close, or gate their pores, controlling the flux of ions across the membrane, and consequently, membrane potential. The long term objectives of the proposed research are to determine the gating mechanisms of ion channels. To work towards this goal, currents will be recorded from single ion channels with the patch clamp technique and analyzed by computer. The channels to be studied are the large conductance calcium-activated potassium channel (BK channel) and the fast C1 channel, obtained from the membrane of mammalian skeletal muscle cells grown in tissue culture. Seven specific projects will be carried out: (1) to determine whether the gating kinetics of ion channels are best described by models with discrete states and constant transition rates between the states (Markovian models) or by models with a continuum of states and fractal scaling (fractal models); (2) to determine whether the brief interruptions (flickers) commonly observed in currents flowing through single channels arise from complete or partial channel closures; (3) to implement an advanced method for determining kinetic gating mechanisms, which uses all of the non-redundant kinetic information in the single channel current record and which takes into account both limited time resolution and the noise in the current record. This method uses computer simulation to calculate, for a given gating mechanisms, the two-dimensional distributions of adjacent open and shut interval durations, which are then compared to the experimental distributions. This advanded method will be used to determine: (4) the steady-state gating mechanism of the fast C1 channel; (5) mechanism by which voltage modulates the activity of the fast C1 channel; (6) the Ca- activated gating mechanism for the normal mode of the BK channel; and (7) the altered gating mechanisms for the other modes of the BK channel. In each case, the most likely gating mechanisms will be defined in terms of kinetic schemes which indicate: the numbers of open and shut states, the transition pathways between the states, the energy barriers for the transitions, and how channel activity is modulated through voltage or calcium induced changes in energy barrier heights. Characterizing ion channels is an important step towards understanding the molecular basis of both normal muscle function and those muscle diseases where defects in the numbers and/or functions of ion channels are implicated. Once the normal channels are characterized, it will be possible to determine if their numbers and/or functions are altered in the disease states.