“They are looking at an area that has been largely unexplored,” he said Gruner’s saltwho studies molecular biophysics at Cornell University; He was consulted on the study but was not a co-author.
Plasmalogen lipids are also found in the human brain, and their role in deep-sea membranes may aid elucidate aspects of cell signaling. Research reveals a fresh way in which life has adapted to the most extreme conditions found in the deep ocean.
Madness in the membrane
The cells of all life on Earth are surrounded by fat molecules called lipids. If you put some lipids in a test tube and add water, they automatically arrange themselves back to back: the fatty, water-hating tails of the lipids come together to form the inner layer, and their water-loving heads come together to form the outer pieces of a slim membrane. “It’s like separating oil and water in a pot,” Winnikoff said. “It’s universal for lipids, and that’s what makes them work.”
In the case of a cell, the outer lipid membrane serves as a physical barrier that, like the outer wall of a house, provides structure and maintains the interior of the cell. But the barrier can’t be too solid: It’s dotted with proteins that need some freedom to perform various cellular tasks, such as moving molecules across the membrane. Sometimes the cell membrane breaks off, releasing chemicals into the environment, and then reattaches.
For a membrane to be robust and functional, it must be strong, fluid and lively at the same time. “The membranes are teetering on the edge of stability,” Winnikoff said. “Even though it has a really well-defined structure, all the individual molecules that make up the sheets on both sides – they keep flowing around each other. It is actually a liquid crystal.
One emerging property of this structure is that the center of the membrane is very sensitive to both temperature and pressure – much more so than other biological molecules such as proteins, DNA or RNA. If you cool a lipid membrane, for example, the molecules will move slower, “and eventually they will just stick together,” Winnikoff said, just like when you put olive oil in the refrigerator. “Biologically speaking, this is generally a bad thing.” Metabolic processes stop; the membrane may even burst and leak its contents.
To avoid this, many cold-adapted animals have membranes composed of a mixture of lipid molecules with slightly different structures to keep the liquid crystal fluid even at low temperatures. Because high pressure also slows the flow of membranes, many biologists assumed that deep-sea membranes were constructed the same way.