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The effect of salinity on the phase behaviour of purified phosphatidylethanolamine and phosphatidylglycerol isolated from a moderately halophilic eubacterium

1990; Elsevier BV; Volume: 56; Issue: 2-3 Linguagem: Inglês

10.1016/0009-3084(90)90096-a

1873-2941

Geoff Sutton, Nicholas J. Russell, Peter J. Quinn,

Protein Structure and Dynamics

The phase behaviour of purified phosphatidylethanolamine and phosphatidylglycerol isolated from the moderately-halophilic eubacterium Vibrio costicola grown in 1 M or 3 M NaCl-containing medium has been studied as a function of NaCl concenctration using differential-scanning calorimetry, freeze-fracture electron microscopy and X-ray diffraction. The two phospholipids exhibited complex phase behaviour which was dependent on the salinity of both the bacterial culture medium and the phospholipid resuspending solution. The phosphatidylethanolamine from cultures grown in 1 M or 3 M NaCl-containing media displayed a hexagonal-II phase and this phase persisted at temperatures up to 20 degrees lower when the lipid was dispersed in 3 M compared with 1 M NaCl. The Lα phase of phosphatidylethanolamine isolated from 1 M NaCl grown cultures was favoured less when the lipid was resuspended in 3 M compared with 1 M NaCl. The Lβ → Lc phase transition temperature of the phosphatidy lethanolamines coincided with ice formation. The phosphatidylglycerol samples did not exhibit non-lamellar phases over the temperature range + 50°C to − 50°C. An increase in salinity of the resuspending solution increased the Lα ↔ Lβ and Lβ ↔ Lc phase transition temperatures, indicating that the Lβ and Lβ phases were both stabilised by the higher NaCl concentration. the Lα ↔ Lβ and Lβ ↔ Lβ phase transition temperatures of phosphatidylglycerol isolated from 3 M NaCl cultures were higher than those from 1 M NaCl cultures.