Interaction of nucleic acids with lipid membranes

Area of Science:

• Biophysics
• Materials Science
• Molecular Biology

Background:

• Understanding nucleic acid thermodynamics is crucial for molecular biology.
• Encapsulating nucleic acids within vesicles can alter their properties.
• Reverse-phase evaporation vesicles (REV) offer a method for encapsulating biomolecules.

Purpose of the Study:

• To investigate the thermodynamics of nucleic acids encapsulated within REV.
• To determine how vesicle composition and surface charge affect nucleic acid denaturation.
• To explore the interaction between nucleic acids and vesicle membranes.

Main Methods:

• Thermal denaturation studies using optical recording with a dual-wavelength spectrophotometer.
• Measurement of hypochromicity and turbidity changes at 260 nm, corrected for turbidity at 320 nm.
• Encapsulation of double-stranded DNA fragments and poly A:poly U within egg-lecithin REV, with varied surface charges using stearic acid, phosphatidyl-glycerol, and phosphatidyl-serine.

Main Results:

• Enclosure of nucleic acids in egg-lecithin REV stabilized the helix-coil transition from 70.5°C to 74°C and broadened it from 0.7°C to 2.7°C.
• Optimal enclosure yield was achieved at a 20% phosphatidyl-serine-lecithin ratio, which also broadened the transition to 5.5°C.
• At 100% phosphatidyl serine, stabilization decreased, and destabilization was observed, with similar trends for poly A:poly U.

Conclusions:

• Nucleic acid encapsulation within REV significantly alters their thermal denaturation thermodynamics.
• Vesicle surface charge plays a critical role in modulating nucleic acid stability and enclosure efficiency.
• Evidence suggests counterion replacement and direct membrane contact influence nucleic acid-membrane interactions.