Effect of Thermozeaxanthins on Liposome Membranes in Acidic and Basic Conditions

Thermozeaxanthins (TZS), a group of carotenoid-glucoside esters extracted from the lipids fraction of thermophilic bacterium, are amphiphilic compounds. The effects of TZS on membrane permeability were examined on large unilamellar liposomes (LUVs) in different pH buffers. The LUVs were composed of 0.01 molar of TZS and phosphatidylcholine (PC) of various lengths and saturation degrees of hydrocarbon chains. The results showed that the LUVs containing TZS were more stable than that liposomes without TZS in pH 5.0, and no significant effects in pH 8.2 and 9.0 buffer solutions. The liposomes composed of TZS and egg PC or E.coli PE were better than those DPPC or DOPC LUVs containing TZS at same experimental conditions. There was no observed difference in stability between the liposomes with or without TZS in pH 6.5 solution. Conclusions (1) Matching of rigid TZS in the lipid bilayer was important in stabilization effects on liposomes, (2)The TZS showed some stabilization effects on liposome membranes in acidic conditions and no significant effects in basic environment.