Preparation of oriented, fully hydrated lipid samples for structure determination using X-ray scattering

Area of Science:

• Materials Science
• Biophysics
• Physical Chemistry

Background:

• Lipid bilayer structure is crucial for biological membranes.
• Oriented lipid samples are essential for X-ray diffraction studies.
• Existing sample preparation methods have limitations in homogeneity and orientation.

Purpose of the Study:

• To introduce and describe the "rock and roll method" for lipid sample preparation.
• To demonstrate the effectiveness of this method for creating well-oriented lipid stacks.
• To compare the rock and roll method with existing techniques like spin-coating.

Main Methods:

• Solvent evaporation with controlled manual sample movement.
• Utilizing various lipid/solvent mixtures for optimal solubilization and deposition.
• Characterization of sample orientation via visual inspection, polarizing microscopy, and X-ray mosaic spread experiments.
• Atomic force microscopy for comparative analysis with spin-coated samples.

Main Results:

• The rock and roll method produces well-oriented thick stacks of approximately 2000 lipid bilayers.
• Successful orientation of diverse lipid types using tailored solvent mixtures.
• Comparison reveals rock and roll method yields less homogeneous but well-oriented stacks compared to spin-coating.
• Prepared samples are suitable for X-ray diffraction and diffuse scattering in both gel and fluid lipid phases.

Conclusions:

• The rock and roll method is an effective technique for preparing oriented lipid samples for X-ray scattering.
• This method provides a valuable alternative for researchers studying lipid phases and structures.
• The ability to fully hydrate samples under controlled conditions enhances their utility for biophysical investigations.