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Pore formation and lipid rearrangement are important features of lipid membranes, important for understanding the fundamental biology of cells and the mechanics of electroporation and membrane-active molecules in synthetic biology applications.

This project was inspired by noticing that the Chain Coordinate for pore formation gave very different results if you used Lipid21 compared with CHARMM36 to form pores in DMPC membranes. Turns out the three behave quite differently when you start deforming the membranes.

Pore formation energy barriers computed using the three force fields for different lipids revealed a consistent pattern. Lipid21 had a higher energy barrier than the other two. This appears to correlate with tilt modulus (k_θ) - how easy it is to rotate a lipid against the membrane normal.

27/10/26, 12:58 pm0 reposts0 likes

Further, these pores had very short lifetimes when the biasing potential was dropped. It should be noted, however, that experimental measurements of pore lifetimes under electrical potentials give much longer lifetimes than observed in MD simulations.

Morphology of formed pores followed from the observed energy barriers and metastability. CHARMM36 and Slipids rearranged into toroidal pores, while Lipid21 had a core composed of pure water and resisted formation the entire way.

Astute readers might have noticed that I haven't mentioned the right panels of the figures covering DMPG (negatively charged) membranes.That's where things get weird. Lipid21 is known to freeze with the state-of-the-art JC ion set. We found that Slipids has the same problem, to a lesser extent.