MECHANISMS OF IONIC CHANNEL ACTIVITY

离子通道是跨越细胞膜的蛋白质大分子。 它们打开和关闭或关闭它们的毛孔，控制离子的流量 跨膜，因此，膜电位。从长远来看 拟议研究的目标是确定门控机制 离子通道。为了实现这一目标，将从 单离子通道的膜片钳技术和分析 电脑。要研究的通道是大电导 钙激活钾通道(BK通道)和快氯通道， 从哺乳动物骨骼肌细胞膜中获得 组织培养。将开展七个具体项目：(一)至 确定离子通道的门控动力学是否可用以下公式描述 具有离散状态和恒定转移速率的模型 状态(马尔可夫模型)或具有状态连续体和 分形标度(分形模型)；(2)确定是否简略 在流经的电流中常见的中断(闪烁) 单个通道是由于通道完全或部分关闭而产生的； 采用一种先进的方法来确定动态浇口机构， 其使用了在单个 通道电流记录，并考虑到两者的有限时间 分辨率和当前记录中的噪音。这种方法使用计算机 模拟计算，对于给定的浇注机构，二维 相邻打开和关闭间隔持续时间的分布，然后 与实验分布进行了比较。这种先进的方法将是 用于确定：(4)快氯的稳态选通机制 通道；(5)电压调节FAST活动的机制 (6)正常模式下的钙激活门控机制 BK通道；以及(7)其他模式的更改的门控机制 BK频道的。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的，它表明：开放的数量 和关闭的状态，状态之间的转换路径，能量 过渡的障碍，以及通道活动是如何通过 电压或钙引起能量屏障高度的变化。 表征离子通道是了解离子通道的重要一步 肌肉功能正常和肌肉疾病的分子基础 其中离子通道的数量和/或功能中的缺陷 牵连其中。一旦确定了正常渠道的特征，就会 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.