Preferential interaction of alpha-tocopherol with phosphatidylcholines in mixed aqueous dispersions of phosphatidylcholine and phosphatidylethanolamine.
The effect of alpha-tocopherol on the structure and phase behaviour of mixed aqueous dispersions of phosphatidylcholine and phosphatidylethanolamine has been examined by synchrotron X-ray diffraction and freeze-fracture electron microscopy. Equimolar mixtures of fully saturated derivatives of phospholipids that show gel phase immiscibility were examined including dimyristoylglycerophosphocholine/dipalmitoylglycerophosphoethanolamin e and distearoylglycerophosphocholine/dilauroylglycerophosphoethanolamine++ +. Analysis of the X-ray scattering intensities recorded at wide angles during heating scans of mixed aqueous dispersions containing 2.5 or 5 mol% alpha-tocopherol showed that alpha-tocopherol disordered the acyl chain packing of the phosphatidylcholine to a greater extent than the phosphatidylethanolamine component of the mixture. This suggested that alpha-tocopherol preferentially interacts with phosphatidylcholine rather than phosphatidylethanolamine, irrespective of whether this was the high or low melting point component of the mixture. The presence of 20 mol% alpha-tocopherol in either phospholipid mixture prevented gel phase separation during the prior cooling scan and no conclusions could be drawn as to the distribution of alpha-tocopherol in these mixtures.
Wang
X
X
Division of Life Sciences, King's College London, UK.
Quinn
P J
PJ
D005614:Freeze Fracturing; D008854:Microscopy, Electron; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism*; D010714:Phosphatidylethanolamines / Q000737:chemistry / Q000378:metabolism*; D012996:Solutions; D017356:Synchrotrons; D014810:Vitamin E / Q000737:chemistry / Q000378:metabolism*; D014961:X-Ray Diffraction
D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D012996:Solutions; D014810:Vitamin E