Simultaneously propagating voltage and pressure pulses in lipid monolayers of pork brain and synthetic lipids
Hydrated interfaces are ubiquitous in biology and appear on all length scales from ions and individual molecules to membranes and cellular networks. In vivo, they comprise a high degree of self-organization and complex entanglement, which limits their experimental accessibility by smearing out the individual phenomenology. The Langmuir technique, however, allows the examination of defined interfaces, the controllable thermodynamic state of which enables one to explore the proper state diagrams. Here we demonstrate that voltage and pressure pulses simultaneously propagate along monolayers comprised of either native pork brain or synthetic lipids. The excitation of pulses is conducted by the application of small droplets of acetic acid and monitored subsequently employing time-resolved Wilhelmy plate and Kelvin probe measurements. The isothermal state diagrams of the monolayers for both lateral pressure and surface potential are experimentally recorded, enabling us to predict dynamic voltage pulse amplitudes of 0.1-3 mV based on the assumption of static mechanoelectrical coupling. We show that the underlying physics for such propagating pulses is the same for synthetic and natural extracted (pork brain) lipids and that the measured propagation velocities and pulse amplitudes depend on the compressibility of the interface. Given the ubiquitous presence of hydrated interfaces in biology, our experimental findings seem to support a fundamentally new mechanism for the propagation of signals and communication pathways in biology (signaling), which is based neither on protein-protein or receptor-ligand interaction nor diffusion.