用一致相互作用计算的连续门控电流模型
Continuum gating current models computed with consistent interactions
摘要：
神经和肌肉的动作电位信号是由电压敏感通道产生的，这些通道包括一个专门的装置来感知电压。现在已知电压传感器的门控电流取决于带正电荷的胆碱通过电压传感器域的疏水塞的来回运动。由跨膜电位的变化引起的这些永久带电的丝氨酸的瞬时运动进一步拖动S4区段并通过移动S4-S5接头诱导离子传导孔的打开/关闭。离子传导孔是与电压传感器分离的装置，通过S4-S5连接器的机械运动和电场变化连接（以未知方式）。这种移动的永久电荷在各处感应电容电流。在电压传感器中，所有的东西都与其他东西相互作用，所以所有的东西都必须与其数学模型中的其他东西相互作用，就像整个蛋白质中的所有东西一样。一个PNP-立体模型的C4段和一个机械模型相结合，使用能量变分法，其中所有的运动的电荷和质量满足守恒定律的电流和质量。由此产生的一维连续体模型用于计算与实验情况相对应的各种条件下的门控电流。基于常微分方程的化学反应型模型不能用一组参数来捕捉这种相互作用。事实上，它们可能无意中违反电流守恒。电流守恒是特别重要的，因为小的违反（<0.01%）迅速（<< 10-6秒）产生破坏分子的力。我们的模型再现了门控电流的特征：（1）门控电流中的开和关电荷相等（2）QV曲线中的饱和电压依赖性和（3）门控电流作为电压函数的形状的许多（但不是全部）细节。
英文摘要：
The action potential signal of nerve and muscle is produced by voltage sensitive channels that include a specialized device to sense voltage. Gating currents of the voltage sensor are now known to depend on the back-and-forth movements of positively charged arginines through the hydrophobic plug of a voltage sensor domain. Transient movements of these permanently charged arginines, caused by the change of transmembrane potential, further drag the S4 segment and induce opening/closing of ion conduction pore by moving the S4-S5 linker. The ion conduction pore is a separate device from the voltage sensor, linked (in an unknown way) by the mechanical motion and electric field changes of the S4-S5 linker. This moving permanent charge induces capacitive current flow everywhere. Everything interacts with everything else in the voltage sensor so everything must interact with everything else in its mathematical model, as everything does in the whole protein. A PNP-steric model of arginines and a mechanical model for the S4 segment are combined using energy variational methods in which all movements of charge and mass satisfy conservation laws of current and mass. The resulting 1D continuum model is used to compute gating currents under a wide range of conditions, corresponding to experimental situations. Chemical-reaction-type models based on ordinary differential equations cannot capture such interactions with one set of parameters. Indeed, they may inadvertently violate conservation of current. Conservation of current is particularly important since small violations (<0.01%) quickly (<< 10-6 seconds) produce forces that destroy molecules. Our model reproduces signature properties of gating current: (1) equality of on and off charge in gating current (2) saturating voltage dependence in QV curve and (3) many (but not all) details of the shape of gating current as a function of voltage.
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