标题： 在活细胞粘弹性环境中建模磁敏感离子通道 显示英文标题

标题： Modeling magnetosensitive ion channels in viscoelastic environment of living cells

摘要： 我们提出并研究了一种假设的磁敏感离子通道模型，长期以来人们认为这种模型可能是解释弱磁场对从磁趋性细菌到鱼类、鸟类、大鼠、蝙蝠及其他哺乳动物（包括人类）等生物的影响的一个可能候选者。 该模型的核心是由一组磁小体组成的短链，这些磁小体作为传感器，通过弹性连接器与形成细胞膜中小簇的离子通道的门控元件耦合。 磁传感器的一端固定在附着于膜上的细胞骨架元素上，并暴露在粘弹性的胞质溶胶中。 其自由端可以在粘弹性的胞质溶胶中随机且次扩散地重新定向，响应外部磁场的变化，并打开耦合离子通道的门。 由于门控元件的双稳态特性，传感器的动力学通常是双稳态的，门控元件可以处于两种状态，其概率取决于传感器的方向。 对于实际参数，研究表明，对于由单畴磁小体构成的传感器棒（每根磁小体具有在磁趋性细菌和其他生物中发现的典型尺寸，或者甚至只有一个足够大的自然存在的特征尺寸的纳米颗粒），该模型通道可以在地球磁场中运行，这些单畴磁小体的数量仅为5到7个。 研究表明，由于介质的粘弹性，双稳态门控动力学通常表现出通道在开放和关闭状态下的停留时间呈幂律和拉伸指数分布。 这为解释其他离子通道的这种异常动力学提供了通用的物理机制，这些离子通道的传感器在由胞质溶胶或生物膜提供的粘弹性环境中移动，在相当普遍的情况下，超出了我们探索的磁敏感离子通道这一迷人假设的范围。 显示英文摘要

摘要： We propose and study a model of hypothetical magnetosensitive ionic channels which are long thought to be a possible candidate to explain the influence of weak magnetic fields on living organisms ranging from magnetotactic bacteria to fishes, birds, rats, bats and other mammals including humans. The core of the model is provided by a short chain of magnetosomes serving as a sensor which is coupled by elastic linkers to the gating elements of ion channels forming a small cluster in the cell membrane. The magnetic sensor is fixed by one end on cytoskeleton elements attached to the membrane and is exposed to viscoelastic cytosol. Its free end can reorient stochastically and subdiffusively in viscoelastic cytosol responding to external magnetic field changes and open the gates of coupled ion channels. The sensor dynamics is generally bistable due to bistability of the gates which can be in two states with probabilities which depend on the sensor orientation. For realistic parameters, it is shown that this model channel can operate in the magnetic field of Earth for a small number (5 to 7) of single-domain magnetosomes constituting the sensor rod each of which has a typical size found in magnetotactic bacteria and other organisms, or even just one sufficiently large nanoparticle of a characteristic size also found in nature. It is shown that due to viscoelasticity of medium the bistable gating dynamics generally exhibits power law and stretched exponential distributions of the residence times of the channels in their open and closed states. This provides a generic physical mechanism for explanation of the origin of such anomalous kinetics for other ionic channels whose sensors move in viscoelastic environment provided by either cytosol or biological membrane, in a quite general context, beyond the fascinating hypothesis of magnetosensitive ionic channels we explore.