Department of Engineering Science, University of Oxford, Oxford, UK.
Medizinische und Biologische Physik, Technische Universität Dortmund, Dortmund, Germany.
J R Soc Interface. 2018 Jun;15(143). doi: 10.1098/rsif.2017.0803.
Nerve impulses, previously proposed as manifestations of nonlinear acoustic pulses localized at the plasma membrane, can annihilate upon collision. However, whether annihilation of acoustic waves at interfaces takes place is unclear. We previously showed the propagation of nonlinear sound waves that propagate as solitary waves above a threshold (super-threshold) excitation in a lipid monolayer near a phase transition. Here we investigate the interaction of these waves. Sound waves were excited mechanically via a piezo cantilever in a lipid monolayer at the air-water interface and their amplitude is reported before and after a collision. The compression amplitude was observed via Förster resonance energy transfer between donor and acceptor dyes, measured at fixed points along the propagation path in the lipid monolayer. We provide direct experimental evidence for the annihilation of two super-threshold interfacial pulses upon head-on collision in a lipid monolayer and conclude that sound waves propagating in a lipid interface can interact linearly, nonlinearly, or annihilate upon collision depending on the state of the system. Thus we show that the main characteristics of nerve impulses, i.e. solitary character, velocity, couplings, all-or-none behaviour, threshold and even annihilation are also demonstrated by nonlinear sound waves in a lipid monolayer, where they follow directly from the thermodynamic principles applied to an interface. As these principles are equally unavoidable in a nerve membrane, our observations strongly suggest that the underlying physical basis of action potentials and the observed nonlinear-pules is identical.
神经冲动，以前被认为是等离子体膜局部非线性声脉冲的表现形式，可以在碰撞时湮灭。然而，界面处的声波是否会湮灭尚不清楚。我们之前展示了在脂质单层临近相变处，超过阈值（超阈值）激发时传播的非线性声波可以作为孤波传播。在这里，我们研究了这些波的相互作用。通过在气液界面处的脂质单层中的压电器件悬臂，机械地激发声波，在碰撞前后报告其振幅。通过供体和受体染料之间的Förster 共振能量转移来测量压缩幅度，在脂质单层中的传播路径上的固定点进行测量。我们提供了直接的实验证据，证明在脂质单层中两个超阈值界面脉冲在正面碰撞时会湮灭，并得出结论，在脂质界面中传播的声波可以根据系统的状态线性、非线性地相互作用或在碰撞时湮灭。因此，我们表明，神经冲动的主要特征，即孤波特性、速度、耦合、全或无行为、阈值甚至湮灭，也可以通过脂质单层中的非线性声波来证明，它们直接源自应用于界面的热力学原理。由于这些原理在神经膜中同样不可避免，我们的观察强烈表明，动作电位和观察到的非线性脉冲的潜在物理基础是相同的。
