Evidence for two-dimensional solitary sound waves in a lipid controlled interface and its implications for biological signalling

Abstract

Biological membranes by virtue of their elastic properties should be capable of propagating localized perturbations analogous to sound waves. However, the existence and the possible role of such waves in communication in biology remain unexplored. Here, we report the first observations of twodimensional solitary elastic pulses in lipid interfaces, excited mechanically and detected by FRET. We demonstrate that the nonlinearity near a maximum in the susceptibility of the lipid monolayer results in solitary pulses that also have a threshold for excitation. These experiments clearly demonstrate that the state of the interface regulates the propagation of pulses both qualitatively and quantitatively. Finally, we elaborate on the striking similarity of the observed phenomenon to nerve pulse propagation and a thermodynamic basis of cell signalling in general.

Label-free optical detection of action potential in mammalian neurons

“…5(C)). The estimated bandwidth and frequencies are comparable to the reported values in lipid monolayer [60]. We believe that the temporal variation of the optical pulses from the AP signal is due to various combination of factors contributing to the electromechanical coupling.…”

“…Lipid monolayers have shown to support propagating 2D pressure pulses [62]. A recent experimental study has characterized the nature of propagating acoustic waves in lipid monolayers [60]. Depending on the magnitude of excitation, different lateral compressibility regimes of lipid monolayer support propagating pulses of varying timescales and frequencies bandwidths.…”

“…Biological membranes can support stationary resonant modes of vibration as well as travelling waves of various forms including surface acoustic waves [5,[60][61][62]. The top surface (cell-media interface) of the neuronal cell body is a curved membrane under tension that is attached to the bottom (cell-glass interface), and can support 2D Eigen modes of vibration (Fig.…”

“…In the nonlinear compressibility regime, a soliton like pulse propagation with a wide frequency spread (few Hz to 300 Hz) was observed. While in the linear compressibility regime, a transient wave with a reduced amplitude and a narrow frequency distribution travels in the lipid monolayer [60]. Wavelet analysis (Fig.…”

Solitary electromechanical pulses in lobster neurons

“…Recently, there have been various reports, both theoretical and experimental, regarding the possibility of mechanical pulse propagation in artificial systems close to transitions and in nerves (14,16,17,21,22,(31)(32)(33). Heimburg and Jackson (14) argued that, close to the phase transitions found in biological tissue, electromechanical solitons with properties similar to those of the action potential can travel along the nerve axons.…”