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Cations Control Lipid Bilayer Memcapacitance Associated with Long-Term Potentiation

September 18, 2023

Scientific Achievement

Long term potentiation (LTP) an important feature of learning and memory in the brain is sensitive to different salts (KCl, NaCl, LiCl, and TmCl3), with LiCl and TmCl3 having the most profound effect in depressing LTP, relative to KCl.

Figure 1. (A) Schematic of a droplet interface bilayer (DIB) made from DPhPC (1,2-diphytanoyl-sn-glycero-3-phosphocholine)-coated water droplets with different salt solutions (KCl, NaCl, LiCl, or TmCl3) in hexadecane. Micrometer size droplets were suspended from silver/silver chloride (Ag/AgCl) electrodes. The lipid bilayer is approximately 4 nm thick. (B) A pinched hysteresis loop, plotted as charge (the time integral of the current) vs voltage (qV), is the signature of a memcapacitive system. (2,3) The green arrows indicate the directionality and sequence of the voltage polarity. The frequency of the sinusoidal voltage waveform was 0.01 Hz, and the amplitude was 0.12 V, with changes in voltage occurring in 0.97 μV increments. One complete loop took 99 s to collect. Zones I and III correspond to the positive and negative voltage-polarity-pinched hysteresis lobes, respectively. The integrated area of each lobe (zones I and III) corresponds to the energy in the lipid bilayer.

Significance and Impact

LTP is the result of nonequilibrium steady state where the membrane’s structure and dielectric properties are altered, while it dissipates energy in the form of heat.

Research Details

  • Droplet interface bilayers (DIBs) consisting of nm-thick planar lipid bilayers that form on contact between lipid coated aqueous droplets in oil were used for electrical measurements.
  • Electrical stimulation training consisted of a low-frequency sinusoidal voltage that induced structural rearrangements of the bilayer, generating long-lived LTP in the form of stored capacitive energy.
  • Different salts (KCl, NaCl, LiCl, and TmCl3), were used to measure their effect on LTP.

Related Publication: Scott, H. L. et. al. (2023). Cations Control Lipid Bilayer Memcapacitance Associated with Long-Term Potentiation. ACS Appl. Mater. Interfaces, 2023.