University of Augsburg, Experimental Physics I, Augsburg, Germany.
Biophys J. 2009 Nov 18;97(10):2710-6. doi: 10.1016/j.bpj.2009.07.049.
Sound waves are excited on lipid monolayers using a set of planar electrodes aligned in parallel with the excitable medium. By measuring the frequency-dependent change in the lateral pressure, we are able to extract the sound velocity for the entire monolayer phase diagram. We demonstrate that this velocity can also be directly derived from the lipid monolayer compressibility, and consequently displays a minimum in the phase transition regime. This minimum decreases from v(0) = 170 m/s for one-component lipid monolayers down to v(m) = 50 m/s for lipid mixtures. No significant attenuation can be detected confirming an adiabatic phenomenon. Finally, our data propose a relative lateral density oscillation of Deltarho/rho approximately 2%, implying a change in all area-dependent physical properties. Order-of-magnitude estimates from static couplings therefore predict propagating changes in surface potential of 1-50 mV, 1 unit in pH (electrochemical potential), and 0.01 K in temperature, and fall within the same order of magnitude as physical changes measured during nerve pulse propagation. These results therefore strongly support the idea of propagating adiabatic sound waves along nerves as first thoroughly described by Kaufmann in 1989 and recently by Heimburg and Jackson, but already claimed by Wilke in 1912.
声波在脂质单层中使用一组与可兴奋介质平行对齐的平面电极激发。通过测量侧向压力随频率的变化，我们能够提取整个单层相图的声速。我们证明，该速度也可以直接从脂质单层压缩性中得出，并且在相变区域显示出最小值。这个最小值从单一组分脂质单层的 v(0) = 170 m/s 下降到脂质混合物的 v(m) = 50 m/s。没有检测到明显的衰减，证实了绝热现象。最后，我们的数据提出了相对横向密度振荡的 Deltarho/rho 约为 2%，意味着所有依赖于面积的物理性质都发生了变化。因此，来自静态耦合的数量级估计预测表面电势会发生传播变化，幅度为 1-50 mV、1 个 pH 单位（电化学势）和 0.01 K 的温度变化，并且与神经脉冲传播过程中测量到的物理变化处于同一数量级。这些结果因此强烈支持沿着神经传播绝热声波的想法，这是 Kaufmann 在 1989 年和 Heimburg 和 Jackson 最近提出的，Wilke 在 1912 年就已经提出过。
