[Effect of cryoprotectors on the structural state of liposomes cooled to minus 25 degrees C]

Cryoprotectors (propylene glycol), ethylene glycol, polyethylene glycol-1500 and dimethyl sulphoxide) are studied for their effect on permeability of liposomes for incorporated molecules of 5,5-dithiobis-2-nitrobenzoic acid (DTNB) under cooling within a temperature range from 0 degree C to -25 degrees C. A similarity is found in the way of ethylene glycol and propylene glycol, dimethyl sulphoxide and polyethylene glycol-1500 effect on the liposome permeability way. Cooling in the presence of ethylene glycol and propylene glycol causes changes in liposome permeability with a local maximum at -18 degrees C. In the medium with 2M NaCl and ethylene glycol, liposomes were resistant to cooling. Dimethyl sulphoxide and polyethylene glycol-1500 induced a two-phase kinetics of changes in liposome permeability, the first phase being within the 0 = -9 degrees C and the second--within -9--25 degrees C temperature ranges. The found differences are supposed to be associated with the effect of the cryoprotective compounds on the lipid crystallization in a lower-temperatures range.