  Lipid interfaces not only compartmentalize but also connect different
reaction centers within a cell architecture. These interfaces have well defined
specific heats and compressibilities, hence energy can propagate along them
analogous to sound waves. Lipid monolayers prepared at the air-water interface
of a Langmuir trough present an excellent model system to study such
propagations. Here we propose that recent observations of two-dimensional shock
waves observed in lipid monolayers also provide the evidence for the detonation
of shock waves at such interfaces, i.e. chemical energy stored in the interface
can be absorbed by a propagating shock front reinforcing it in the process. To
this end, we apply the classical theory in shock waves and detonation in the
context of a lipid interface and its thermodynamic state. Based on these
insights it is claimed that the observed self-sustaining waves in lipid
monolayers represent a detonation like phenomena that utilizes the latent heat
of phase transition of the lipids. However, the general nature of these
equations allows that other possible sources of chemical energy can contribute
to the propagating shock wave in a similar manner. Consequently, the
understanding is applied to the nerve pulse propagation that is believed to
represent a similar phenomenon, to obtain a qualitative understanding of the
pressure and temperature dependence of amplitude and threshold for action
potentials. While we mainly discuss the case of a stable detonation, the
problem of initiation of detonation at interfaces and corresponding heat
exchange is briefly discussed, which also suggests a role for thunder like
phenomena in pulse initiation.
