MECHANISMS OF IONIC CHANNEL ACTIVITY

离子通道是跨越细胞膜的大蛋白质大分子。 它们打开和关闭，或者说控制它们的毛孔，控制离子的流动 穿过细胞膜，从而产生膜电位。 长期 提出的研究目标是确定门控机制 离子通道。 为了实现这一目标，将记录电流， 单离子通道的膜片钳技术和分析 电脑 研究的通道是大电导通道 钙激活钾通道（BK通道）和快Cl通道， 从哺乳动物骨骼肌细胞的膜中获得， 组织培养 将开展七个具体项目：（1） 确定离子通道的门控动力学是否最好地描述为 模型与离散状态和恒定的过渡率之间的 状态（马尔可夫模型）或具有连续状态的模型， 分形尺度（分形模型）;（2）确定是否简要 在流过的电流中经常观察到的中断（闪烁） 单通道由通道完全或部分闭合引起;（3） 实施用于确定动态浇口机制的先进方法， 它使用所有的非冗余的动力学信息， 通道电流记录，并考虑到有限的时间 分辨率和当前记录中的噪声。 该方法使用计算机 模拟计算，对于给定的浇注机制，二维 相邻打开和关闭间隔持续时间的分布，然后 与实验分布相比。 这种方法将是 用于确定：（4）快Cl的稳态门控机制 （5）电压调节快通道活动的机制 Cl通道;（6）正常模式的Ca激活门控机制。 BK通道;（7）其他模式的门控机制改变 BK频道。 在每种情况下，最有可能的门控机制将是 根据动力学方案定义，该方案表明： 和关闭状态，状态之间的跃迁路径，能量 转换的障碍，以及通道活动如何通过 电压或钙引起的能垒高度的变化。 表征离子通道是理解离子通道的重要一步。 正常肌肉功能和肌肉疾病的分子基础 其中离子通道的数量和/或功能的缺陷 牵连 一旦正常信道被表征， 可以确定它们的数量和/或功能是否在 疾病状态。

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 Cl 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 Cl channel; (5) mechanism by which voltage modulates the activity of the fast Cl 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.