The temperature dependence of lipid membrane permeability, its quantized nature, and the influence of anesthetics

Abstract

We investigate the permeability of lipid membranes for fluorescence dyes and ions. We find that permeability reaches a maximum close to the chain melting transition of the membranes. Close to transitions, fluctuations in area and compressibility are high, leading to an increased likelihood of spontaneous lipid pore formation. Fluorescence Correlation Spectroscopy (FCS) reveals the permeability for rhodamine dyes across 100 nm vesicles. Using FCS, we find that the permeability of vesicle membranes for fluorescence dyes is within error proportional to the excess heat capacity. To estimate defect size we measure the conductance of solvent-free planar lipid bilayer. Microscopically, we show that permeation events appear as quantized current events. Further, we demonstrate that anesthetics lead to a change in membrane permeability that can be predicted from their effect on heat capacity profiles. Depending on temperature, the permeability can be enhanced or reduced. We demonstrate that anesthetics decrease channel conductance and ultimately lead to 'blocking' of the lipid pores in experiments performed at or above the chain melting transition. Our data suggest that the macroscopic increase in permeability close to transitions and microscopic lipid channel formation are the same physical process.

12 pages, 6 figures

References in corpus (3)

• The thermodynamics of general anesthesia
• Phase state dependent current fluctuations in pure lipid membranes
• The influence of anesthetics, neurotransmitters and antibiotics on the relaxation processes in lipid membranes

Cited by in corpus (18)

• Lipid Ion Channels
• The capacitance and electromechanical coupling of lipid membranes close to transitions. The effect of electrostriction
• Phase state dependent current fluctuations in pure lipid membranes
• Melting transitions in biomembranes
• Voltage-gated lipid ion channels
• Electrical properties of polar membranes
• Comparing ion conductance recordings of synthetic lipid bilayers with cell membranes containing TRP channels
• The thermodynamics of general and local anesthesia
• Ion-channel-like behavior in lipid bilayer membranes at the melting transition
• The thermodynamics of lipid ion channel formation in the absence and presence of anesthetics. BLM experiments and simulations
• The thermodynamic soliton theory of the nervous impulse and possible medical implications
• Phase transitions in biological membranes
• The excitable fluid mosaic
• The Physics of Nerves
• The mechanical properties of nerves, the size of the action potential, and consequences for the brain
• A physical perspective on lithium therapy
• Topological derivative for a fast identification of short, linear perfectly conducting cracks with inaccurate background information
• Nonlinear conductance, rectification and mechanosensitive channel formation of lipid membranes