[Assessment of the viscoelastic properties of biological membranes by measurements on bilayers].

The frequency characteristic of the complex Young modulus along the normal to surface is measured for the bilayer lipid membranes (BLM). For egg lecithin membranes the absolute value of the modulus (formula: see text) rises from 4.10(6) to 10(8) dyn/cm2 (n-decane) and from 10(8) to 10(9) dyn/cm2 (n-hexadecane) with the frequency change from 20 Hz to 15 000 Hz depending on different membrane solvents. (formula: see text) also rises several times if cholesterol is added or lipid hydrocarbon chains are longer or more saturated. If the solvent--n-hexadecane is freezed out in the region of 14 degrees C,(formula: see text) increases up to 10(10) dyn/cm2. The loss angle is measured and real and imaginary parts of (formula: see text) are determined. (formula: see text) posesses the relaxtion times spectrum in the range 10(-5)--10(-3) s. The conclusion is made that biological membranes like BLM have polymer properties, their (formula: see text) values may achieve 10(10) dyn/cm2 and the relaxation times are greater than 10(-3) s.