New study shows membrane flexibility hinges on how tightly lipids are packed

Cellular membranes crap, protect and protect living cells. Membranes can even affect the behavior of a cell.

But the own erratic behavior of membranes has intrigued scientists for years.

It turns out that this is a question of perspective: when the members of the team of the physicist Rana Ashkar examined how the membranes behave on a nanometric scale, they were able to identify the unified biophysical laws to which the membranes have always joined.

Published in Nature communicationsThese results have significant implications for disease intervention methods, drug administration applications, artificial cell technologies and the next phase of membrane biophysics.

Superhero that changes composition

Mainly composed of fatty compounds called lipids, the membranes are very adaptive. They can modify their lipid composition in response to environmental factors, responding – sometimes within hours – changes in diet, pressure or temperature. This property, called homeostasis, maintains the cities of your cells happily hums in different conditions.

To understand how homeostasis works, scientists have tried to frame it in the context of an important physical principle which says that the structure of the membrane must affect its physical properties.

Makes sense, right? What something is done must have an impact on the way it behaves.

And yet, for years, the membranes have obstinately escaped this law.

The contempt for the law was in full exposure when scientists injected cholesterol into model cell membranes, modifying the structure, to see if this would affect the property of a membrane, like its flexibility or its elasticity. The results were everywhere on the board – some membranes stiffen while others have not done so.

It’s not the type of lipid but how you wander it

“It caused a dilemma on the ground,” said Ashkar. “In one way or another, cholesterol has changed the structure of certain membranes but not their elastic properties.”

The widespread hypothesis was that different types of lipids reacted differently to cholesterol. But Ashkar was not convinced. She decided to try something else. Previous studies have examined the elasticity of the membrane using macroscopic measurements. The Ashkar team looked more closely. Much closer.

By using neutrons and X -rays, team members have found that what affects elasticity is not the type of lipid but how closely they are packed in the membrane.

Certain types of lipids resist being congested, while others can be pushed as tight as sardines. And packaging density is the main factor that affects the flexibility of the membrane, which in turn regulates cellular viability.

To confirm these results more, Ashkar and his team collaborated with the Michael Brown laboratory at the University of Arizona and the Mila Doktorova laboratory at the University of Stockholm. Their nuclear resonance experiences and their calculation studies followed the same laws obtained by the Ashkar laboratory.

“The membranes can have a remarkable composition complexity, but what really matters to determine or predict their elasticity, it is how packaged they are,” said Ashkar. “And it is a very, very powerful design principle that cells seem to follow and that we can now apply in realistic artificial cells of engineering.”