Related Experiment Videos
Polymorphism in myristoylpalmitoylphosphatidylcholine
S Tristram-Nagle1, Y Isaacson, Y Lyatskaya
1Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA. stn+@andrew.cmu.edu
Chemistry and Physics of Lipids
|January 20, 2000
Summary
This study reveals that mixed-chain lipids like myristoylpalmitoylphosphatidylcholine (MPPC) form stable subgel and ripple phases upon temperature changes, unlike same-chain lipids. These phases exhibit distinct X-ray diffraction patterns and thermal behaviors.
Area of Science:
- Lipid bilayer thermodynamics
- Membrane biophysics
- Materials science
Background:
- Mixed-chain phosphatidylcholines (PCs) exhibit complex phase behaviors.
- Understanding lipid phase transitions is crucial for membrane function.
- Myristoylpalmitoylphosphatidylcholine (MPPC) is a model mixed-chain PC.
Purpose of the Study:
- To investigate the phase transitions and structural properties of MPPC near full hydration.
- To characterize the formation and stability of subgel and ripple phases in MPPC.
- To compare the phase behavior of mixed-chain PCs with same-chain PCs.
Main Methods:
- Synthesis of MPPC with minimal acyl chain migration.
- Temperature-jump (T-jump) experiments to induce phase transitions.
- X-ray diffraction (low-angle and wide-angle) to analyze phase structures.
Main Results:
- MPPC readily forms a stable subgel phase below 20°C after T-jumping from the Lα phase.
- Above 24°C, MPPC forms a ripple phase with coexisting wavelengths (240 Å and 130 Å).
- Melting from the subgel phase results in a ripple phase with a single wavelength (130 Å).
- No stable gel phase was observed; instead, an ill-defined pattern transformed into subgel or ripple phases.
- Wide-angle X-ray diffraction showed distinct patterns for subgel and ripple phases.
Conclusions:
- MPPC exhibits distinct subgel and ripple phases dependent on temperature.
- The absence of a stable gel phase in MPPC is attributed to the dominance of the subgel phase.
- Further research is needed to elucidate the subgel structure and molecular interactions in mixed-chain PCs.