THE CRYOPROTECTANT TREHALOSE DESTABILIZES THE BILAYER ORGANIZATION OFESCHERICHIA-COLI DERIVED MEMBRANE SYSTEMS AT ELEVATED-TEMPERATURES ASDETERMINED BY H-2 AND P-31-NMR

In this study, H-2 and P-31-NMR techniques were used to study the effe cts of trehalose and glycerol on phase transitions and lipid acyl chai n order of membrane systems derived from cells of E. coli unsaturated fatty acid auxotroph strain K1059, which was grown in the presence of [11,11-H-2(2)]-oleic acid or [11,11-H-2(2)]-elaidic acid. From an anal ysis of the temperature dependence of the quadrupolar splitting it cou ld be concluded that neither 1 M trehalose or glycerol generally had a ny significant effect on the temperature of the lamellar gel to liquid -crystalline phase transition. In the case of the oleate-containing hy drated total lipid extract, glycerol but not trehalose caused a 5 degr ees C increase of this transition temperature. In general, both cryopr otectants induced an ordering of the acyl chains in the liquid-crystal line state. Trehalose and glycerol both decrease the bilayer to non-bi layer transition temperature of the hydrated lipid extract of oleate-g rown cells by about 5 degrees C, but only trehalose in addition induce s an isotropic to hexagonal (H-II) phase transition. In the biological membranes, trehalose and not glycerol destabilised the lipid bilayer, and in the case of the E. coli spheroplasts, part of the induced non- bilayer structures is ascribed to a hexagonal (H-II) phase in analogy with the total lipids. Interestingly, 1 mM Mg2+ was a prerequisite for the destabilisation of the lipid bilayer. In the hydrated total lipid extract of E. coli grown on the more ordered elaidic acid, both trans ition temperatures were shifted about 20 degrees C upwards compared wi th the oleate-containing lipid, but the effect of trehalose on the lip id phase behaviour was similar. The bilayer destabilising ability of t rehalose might have implications for the possible protection of biolog ical systems by (cryo-)protectants during dehydration, in that protect ion is unlikely to be caused by preventing the occurrence of polymorph ic phase transitions.