IMPEDANCE SPECTROSCOPIC INVESTIGATION OF THE TEMPERATURE INFLUENCE ONTHE TRANSFER OF TETRAPHENYLBORATE IONS THROUGH LIPID-MEMBRANES - CALCULATION OF ENERGY BARRIERS FOR THE ION TRANSFER ACROSS LIPID-MEMBRANES
Kd. Schulze, IMPEDANCE SPECTROSCOPIC INVESTIGATION OF THE TEMPERATURE INFLUENCE ONTHE TRANSFER OF TETRAPHENYLBORATE IONS THROUGH LIPID-MEMBRANES - CALCULATION OF ENERGY BARRIERS FOR THE ION TRANSFER ACROSS LIPID-MEMBRANES, Chemical physics, 238(3), 1998, pp. 495-505
Investigating the transfer of tetraphenylborate (TPB) ions through pla
nar lipid membranes we found a strong influence of temperature on the
impedance spectrum. The impedance spectrum of TPB modified lipid membr
anes is governed by two processes, namely, the ion transfer at the mem
brane surfaces and the ion transfer across the hydrophobic interior of
the membrane. The analysis of the measured spectra showed that temper
ature predominately influences the inner ion transfer and the rate con
stant for the inner transfer, respectively. We used this temperature d
ependence to calculate energy barriers for the ion translocation acros
s the membrane interior. Varying the composition of the membrane lipid
s we found that the inner barrier not only depends on the hydrocarbon
part but also on the head group of the lipid. We explain this interest
ing result with interactions of the permeating TPB ions with the head
groups of the membrane. The above-mentioned interactions seem to immob
ilize the TPB ion at the membrane surface and to enlarge the energy ba
rrier for the ion transfer across the inner part of the lipid membrane
. The largest barriers were found for the investigated lecithins whose
phosphocholine head group strongly interacts with the TPB ions. (C) 1
998 Elsevier Science B.V. All rights reserved.