Images of membranes (circles) taken using transmission electron cryomicroscopy. Top: membranes in a solution that contains no amino acids. Bottom: membranes in a solution containing serine, an amino acid, which triggers membranes to form multiple layers of concentric membranes. Scale bars: 100 nanometers. Alex Mileant/Caitlin Cornell
Life on Earth arose about 4 billion years ago when the first cells formed within a primordial soup of complex, carbon-rich chemical compounds. These cells faced a chemical conundrum. They needed particular ions from the soup in order to perform basic functions. But those charged ions would have disrupted the simple membranes that encapsulated the cells. A team of researchers at the University of Washington has solved this puzzle using only molecules that would have been present on the early Earth. Using cell-sized, fluid-filled compartments surrounded by membranes made of fatty acid molecules, the team discovered that amino acids, the building blocks of proteins, can stabilize membranes against magnesium ions. Their results set the stage for the first cells to encode their genetic information in RNA, a molecule related to DNA that requires magnesium for its production, while maintaining the stability of the membrane.
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