title: Dielectric relaxations on erythrocyte membrane as revealed by spectrin denaturation.
abstract: We studied the effect of spectrin denaturation at 49.5°C (TA) 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 TA, resulted in a bell-shaped peak at 1.5MHz. The changes in the real and imaginary components of Z* and C* at TA, i.e., ΔZre, ΔZim, ΔCre and ΔCim, calculated in the same way, strongly varied with frequency. Between 1.0 and 12MHz the -ΔZim vs ΔZre, and ΔCim vs ΔCre plots depicted semicircles with critical frequencies, fcr, at 2.5MHz expressing recently reported relaxation of spectrin dipoles. Between 0.02 and 1.0MHz the -ΔZim vs ΔZre plot exhibited another relaxation whose fcr 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.
authors.affiliation: Dept. of Physics, Biophysics, Reontgenology and Radiology, Medical Faculty, Thracian University, Stara Zagora 6000, Bulgaria. Electronic address: ivanov_it@gbg.bg.
authors.forename: I T
authors.initials: IT
authors.lastname: Ivanov
authors.affiliation: Dept. of Physics, Biophysics, Reontgenology and Radiology, Medical Faculty, Thracian University, Stara Zagora 6000, Bulgaria.
authors.forename: B
authors.initials: B
authors.lastname: Paarvanova
mesh_terms: D017097:Electric Impedance; D004910:Erythrocyte Membrane / Q000378:metabolism*; D006801:Humans; D008051:Lipid Bilayers / Q000378:metabolism; D011489:Protein Denaturation; D013049:Spectrin / Q000737:chemistry* / Q000378:metabolism; D013696:Temperature
chemical_list: D008051:Lipid Bilayers; D013049:Spectrin
keywords: Dielectric spectroscopy; Piezoeffect on spectrin; Spectrin repeat unit