Dielectric relaxations on erythrocyte membrane as revealed by spectrin denaturation

We studied the effect of spectrin denaturation at 49.5 degrees C (T-A) on the dielectric relaxations and related changes in the complex impedance, Z*, complex capacitance, C*, and dielectric loss curve of suspensions containing human erythrocytes, erythrocyte ghost membranes (EMs) and Triton-X-100 residues of EMs. The loss curve prior to, minus the loss curve after T-A, resulted in a bell-shaped peak at 1.5 MHz. The changes in the real and imaginary components of Z* and C* at T-A, i.e., Delta Z(re), Delta Z(im), Delta C-re and Delta C-im, calculated in the same way, strongly varied with frequency. Between 1.0 and 12 MHz the -Delta Z(im), vs Delta Z(re,) and Delta C-im vs Delta C-re plots depicted semicircles with critical frequencies, f(cr), at 2.5 MHz expressing recently reported relaxation of spectrin dipoles. Between 0.02 and 1.0 MHz the -Delta Z(im) vs Delta Z(re) plot exhibited another relaxation whose f(cr), mirrored that of beta relaxation. This relaxation was absent on Triton-X-shells, while on erythrocytes and EMs it was inhibited by selective dissociation of either attachment sites between spectrin and bilayer. Considering above findings and inaccessibility of cytosole to outside field at such frequencies, the latter relaxation was assumed originating from a piezoelectric effect on the highly deformable spectrin filaments. (C) 2016 Elsevier B.V. All rights reserved.