Research Spotlight: Why are most biological lipids asymmetric in their acyl chain?

Posted on September 03, 2021

Asymmetric Phospholipids

Phospholipids are vital to living cells, surrounding them in a flexible and selectively permeable membrane. These membranes must be able to move molecules in and out of the cell and divide to produce new cells. Phospholipids contain two fatty acyl chains. These chains can be either saturated or unsaturated. The majority of phospholipids found in cell membranes are asymmetrical concerning their fatty acyl chains and contain one saturated and one unsaturated chain. Previously, we did not have a good understanding of why this is the case. Thanks to Dr. Antonny and his team of researchers we now have a clearer picture!

This research used a comprehensive analysis to investigate the effect that acyl chain asymmetry and polyunsaturation have on the mechanical activity of dynamin. The acyl chain profile determines if a membrane will be resistant or permissive to dynamin-mediated membrane vesiculation. There is a narrow window that allows for phospholipid membranes to be both highly deformable and still impermeable to small solutes. Asymmetric phospholipids containing one unsaturated and one polyunsaturated acyl chain are much less “leaky” than membranes made up of symmetrical polyunsaturated acyl chains. The asymmetrical phospholipids are also readily vesiculated by dynamin.

Rotational freedom is a key characteristic of polyunsaturated acyl chains. The presence of saturated carbons between unsaturated carbons allows for an exceptionally high rotational freedom compared to the rotational freedom observed around saturated carbons surrounded by zero or one unsaturated carbon atom. The greater the amount of unsaturation in an acyl chain, the greater the rotational freedom observed. So, one polyunsaturated acyl chain should allow for the membrane to readily adapt the conformation to membrane curvature while the saturated acyl chain provides secure lipid packaging to prevent the passage of small molecules.

This information could also be applied to various ratios of lipids in human health. For example, saturated-decosahexaenoic acid (DHA) (omega-3) are systematically better for membrane vesiculation than other saturated-polyunsaturated phospholipids, such as saturated-arachidonate (omega-6). The omega-6/omega-3 ratio is important for human health and this research could give key insight into the balance of these phospholipids and the effect that it plays on health.

A membrane’s ability to vesiculate and simultaneously act as a selective barrier is key to its function. These properties have to be perfectly balanced to allow for both. The research from Dr. Antonny’s lab suggests that this balance can be fine-tuned through asymmetry and unsaturation in acyl chain lengths of phospholipids.

Thank you, Dr. Antonny, for being a loyal friend and customer of Avanti! We are proud to provide the highest-quality lipids for the highest-quality research. We look forward to seeing what else this partnership can accomplish! To read even more about this topic, click HERE!

Image Credit: Original Research Publication