Simon Fabiunke, Christian Fillafer und Matthias Schneider sind an der Medizinischen und Biologischen Physik der TU-Dortmund.
Abstract:
Nonlinear pulses like action potential are considered to be purely electrical phenomena. However, it has been shown that thermal, mechanical, chemical and optical changes also occur at the excitable membrane. From a thermodynamic perspective such pulses have been described as a propagating state change in the cell membrane.In the present work, we investigated the emission properties of a commonly used potential-sensitive dye (di-4-ANEPPDHQ) as a function of state in phospholipid vesicles and cell membranes. When the thermodynamic state of vesicles made from di-myristoylphosphatidylserine (DMPS) was changed by temperature or pH, the fluorescence intensity and spectrum of the embedded dye underwent characteristic changes. During the transition from the liquid-disordered to the liquid-ordered phase, the fluorescence intensity exhibited a maximum and the emission spectrum shifted to shorter wavelengths (by 26 nm). Subsequently, the same dye was incorporated into the plasma membrane of an excitable cell (Chara braunii). When an action potential was triggered the emission spectrum shifted to shorter wavelengths. This indicates that propagation of an action potential is associated with a significant change of state of the excitable cell membrane.