Ice formation in model biological membranes in the presence of cryoprotectors

Ice formation in model biological membranes is studied by SAXS and WAXS in the presence of cryoprotectors: dimethyl sulfoxide and glycerol, Three type s of phospholipid membranes: DPPC, DMPC, DSPC are chosen for the investigat ion as well-studied model biological membranes. A special cryostat is used for sample cooling from 14.1 degrees C to -55.4 degrees C. The ice formatio n is detected only by WAXS in binary phospholipid/water and ternary phospho lipid/cryoprotector/water systems in the condition of excess solvent. Ice f ormation in a binary phospholipid/water system creates an abrupt decrease o f the membrane repeat distance by Delta d, the so-called ice-induced dehydr ation of intermembrane space. The value of Delta d decreases as the cryopro tector concentration increases. The formation of ice does not influence the membrane structure (Delta d = 0) for cryoprotector mole fractions higher t han 0.05. (C) 2000 Elsevier Science B.V. All rights reserved.