Frequency dependence of the shear moduli of spectrin studied using a multiple lumped resonator viscoelastometer

The frequency dependence (119-7860 Hz) of the storage and loss shear moduli, G' and G'', of human erythrocyte spectrin dimer crude solutions at 22.5 degrees C has been measured using a Birnboim-Schrag multiple lumped resonator viscoelastometer. The measurements were carried out on solutions of ionic strength 1 mM containing 1.1-3.7 mg ml-1 spectrin. This corresponds to the terminal zone for G' and G''. Analysis of the data using the standard theory of hybrid relaxation spectra yields a relaxation time of 22.5 +/- 1 microseconds. The pure spectrin dimer relaxation time is estimated to be 16 +/- 3 microseconds. This result suggests that at an ionic strength of 1 mM, the spectrin dimers are extended and that the main relaxation process is simple end-over-end rotation.