Impedance spectroscopy of human erythrocyte membrane: Effect of frequency at the spectrin denaturation transition temperature

Thermal analysis of suspension impedance was applied at various frequencies, f, to study the changes in erythrocyte membranes (EM) over the temperature interval 47–53 °C where spectrin denatures. At f < crossover frequency (cof1) a decrease in EM resistance at 49.5 °C (A peak) has been observed. At f > cof1, when the capacitive conductance of EM becomes dominant, a second peak appeared at 50.5 °C (anti-A peak). The amplitudes of A and anti-A peaks reversibly depended on the phosphorylation of EM proteins. In contrast to the A peak, the anti-A peak was totally eliminated by modifications of EM with reagents that reduce EM deformability, OsO4 (0.4–1 mM) and putrescine (cytosolic concentration 1.5–2.0 mM).