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DMSO produces a new subgel phase in DPPC: DSC and X-ray diffraction study
S Tristram-Nagle1, T Moore, H I Petrache
1Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA. stn+@andrew.cmu.edu
Biochimica Et Biophysica Acta
|April 7, 1998
Summary
Dimethylsulfoxide (DMSO)/water mixtures alter dipalmitoylphosphatidylcholine (DPPC) lipid phases. DMSO addition initially slows, then accelerates, subgel phase transformation, revealing new stable phases and altered bilayer structures.
Area of Science:
- Biophysics
- Materials Science
- Physical Chemistry
Background:
- Dipalmitoylphosphatidylcholine (DPPC) is a key phospholipid in biological membranes.
- Understanding lipid phase behavior is crucial for drug delivery and biomaterial design.
- Dimethylsulfoxide (DMSO) is a common solvent with known effects on lipid hydration.
Purpose of the Study:
- To investigate the equilibrium phases and transformation kinetics of DPPC in DMSO/water mixtures.
- To characterize the structural and thermodynamic changes induced by varying DMSO concentrations.
- To elucidate the formation of novel subgel phases and their properties.
Main Methods:
- Differential Scanning Calorimetry (DSC) for thermodynamic analysis.
- X-ray Diffraction (XRD) for structural characterization.
- Electron density profiling for detailed bilayer structure determination.
Main Results:
- DMSO addition initially retards, then accelerates, the gel-to-subgel transformation.
- A new stable subgel phase (S) was identified above X = 0.10 DMSO mole fraction.
- The S phase exhibits increased bilayer thickness, altered headgroup ordering, and reduced chain tilt compared to the C subgel phase.
- Increasing DMSO concentration reduces inter-bilayer water spacing across all lipid phases.
- A distinct gel phase emerged at X = 0.20, possibly due to altered chain tilt orientation.
Conclusions:
- DMSO significantly influences DPPC phase behavior, kinetics, and structure.
- The S subgel phase represents a novel structural state of DPPC bilayers.
- DMSO's dehydrating effect is a primary driver for observed phase transitions and elevated main transition temperatures.