  Hydrated interfaces are ubiquitous in biology and appear on all length scales
from ions, 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, whose controllable thermodynamic state 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 timeresolved 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 to 3mV based on the assumption of static
mechano-electrical coupling. We show that the underlying physics for such
propagating pulses is the same for synthetic (DPPC) 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 neither based on protein-protein or
receptor-ligand interaction nor on diffusion.
