DPPC Membrane Under Lateral Compression and Stretching to Extreme Limits: Phase Transitions and Rupture.

Area of Science:

• Biophysics
• Materials Science
• Computational Chemistry

Background:

• Dipalmitoylphosphatidylcholine (DPPC) is a major component of mammalian cell membranes, crucial for cellular function.
• Understanding DPPC membrane behavior under mechanical stress is vital for biological and technological applications.

Purpose of the Study:

• To investigate the mechanical behavior and phase transitions of DPPC membranes under varying lateral pressures.
• To precisely identify critical phenomena, such as undulation and rupture, in DPPC bilayers.
• To determine the necessary simulation timescales for accurately capturing membrane responses to extreme stress.

Main Methods:

• Utilized microsecond-scale molecular dynamics simulations to model DPPC membranes.
• Applied lateral pressures ranging from -200 bar (stretching) to 150 bar (compression) at 323 K.
• Analyzed structural metrics to identify phase transitions and critical events.

Main Results:

• Identified a phase transition to an undulated state between 40 and 50 bar under compression.
• Observed systematic membrane thinning under stretching, with rupture probable at -170 bar and certain at -200 bar.
• Detected pressure hysteresis (10-bar shift) during the compression-decompression cycle; the stretching pathway was retraced.

Conclusions:

• DPPC membranes exhibit distinct structural responses to compression and stretching, including phase transitions and rupture.
• Microsecond simulation times are essential for accurately modeling critical phenomena in DPPC membranes under mechanical stress.
• The findings offer critical insights into membrane mechanics relevant to diverse biological and technological fields.