A Ring to Rule Them All: The Effect of CyclopropaneFatty Acids on the Fluidity of Lipid Bilayers.

Cyclopropane fattyacids are widespread in bacteria. As their concentrationincreases on exposure to hostile environments, they have been proposedto protect membranes. Here, the effect of cyclopropane and unsaturatedfatty acids, both in cisand transconfigurations, on the packing, order, and fluidity of lipid bilayersis explored using molecular dynamics simulations. It is shown thatcyclopropane fatty acids disrupt lipid packing, favor the occurrenceof gauchedefects in the chains, and increase thelipid lateral diffusion, suggesting that they enhance fluidity. Atthe same time, they generally induce a greater degree of order thanunsaturated fatty acids of the same configuration and limit the rotationabout the bonds surrounding the cyclopropane ring. This indicatesthat cyclopropane fatty acids may fulfill a dual function: stabilizingmembranes against adverse conditions while simultaneously promotingtheir fluidity. Marked differences in the effect of cis- and trans-monocyclopropanated fatty acids werealso observed, suggesting that they may play alternative roles inmembranes. [ABSTRACT FROM AUTHOR]