|The image of the week is the result of a molecular dynamics simulation of a mammalian plasma membrane (DOI). It looks like a can of worms has opened but the piece of cell wall depicted (a bilayer) consists of a complex mixture of 63 different worm-like lipids (phosphatidylcholines, sphingomyelin and gangliosides for the inside and hosphatidylethanolamine and phosphatidylserine for the outside) with additional cholesterol and water thrown in. This process is called computational microscopy.|
The details: simulations were performed using MARTINI and using a tool called INSANE (INSert membrANE), around half a million particles (lipids, water molecules and counter ions) were crammed into a box measuring 70 by 70 by 11 nm and monitored for 40 microseconds. Initially all players are distributed randomly but phase-separation takes place instantly with cholesterol congregating and also aliphatic lipid tails in general. The gangliosides were also found to form clusters.
The simulation reveals how cholesterol-rich regions flip-flop between the in- and outside. In the accompanying video these regions are like waves in an ocean. Not able to find: the amount of time the computations took, hours?, days?, weeks?. The 40 microseconds were not enough for everything to equilibrate. Hence the curiosity.