Phospholipids showing complex bilayer phase transitions. II. Four sulfur-containing phosphatidylcholines
✍ Scribed by Joseph Hajdu; Julian M. Sturtevant
- Publisher
- Elsevier Science
- Year
- 1990
- Tongue
- English
- Weight
- 437 KB
- Volume
- 55
- Category
- Article
- ISSN
- 0009-3084
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✦ Synopsis
The main phase transitions of aqueous dispersions of four synthetic phosphatidylcholines (PCs) containing sulfur atoms in thioester and thioether linkages have been studied by high sensitivity differential scanning calorimetry (DSC). The transition enthalpies ranged from 7.4 to 10.3 kcal mol "j, with values for t®, the temperature of maximal excess heat capacity, in the range 38.0 to 40.8°C. The corresponding values for dipalmitoyl PC (DPPC) are 8.5 kcal tool-' and 41.7°C. Curve fitting required the sum of from one to four two-state components to give an accurate representation of the observed DSC curves. Comparison of the results given here with those reported by B.Z. Chowdhry, (3. Lipka, J. Hajdu and J.M. Sturtevant, (1984) Biochemistry 23, 2044--2049, for PCs containing arnide, ether or carbamoyl linkages in place of the usual ester bonds shows that small changes in organic structure can result in large changes in thermotropic behavior. The complexity in the cases showing more than a single two-state component is presumably due to a series of sequential cooperative transitions the character of which is at present unknown.