Recent research led by Professor Neal Devaraj from the University of California San Diego's Department of Chemistry and Biochemistry offers a possible answer. Published in 'Nature Chemistry', this study explores the potential formation of early cell membranes through reactions involving basic molecules present on prebiotic Earth.
Cellular life depends on lipid membranes, essential structures that contain and support cell functions. Lipids, composed of long fatty acid chains, were necessary for these early membranes. However, how these components formed from the simpler molecules available billions of years ago has remained a puzzle.
Evidence suggests that primitive Earth had short fatty chains with fewer than 10 carbon-carbon bonds, while more complex fatty chains needed for cellular vesicles often have longer chains. The challenge has been understanding how these chains formed stable membrane structures under early Earth conditions, where high concentrations of such molecules were unlikely.
Professor Devaraj explained the challenge: "On the surface, it may not seem novel because lipid production happens in the presence of enzymes all the time. But over four billion years ago, there were no enzymes. Yet somehow these first protocell structures were formed. How? That's the question we were trying to answer."
The research team began by experimenting with cysteine, an amino acid, and a short-chain choline thioester. Silica glass served as a mineral catalyst, facilitating the reaction by attracting the thioester molecules to its negatively charged surface. This interaction enabled the cysteine and thioesters to react and produce lipid molecules, resulting in stable membrane vesicles at concentrations much lower than would have been required without a catalyst.
"Part of the work we're doing is trying to understand how life can emerge in the absence of life. How did that matter-to-life transition initially occur?" Devaraj noted. "Here we have provided one possible explanation of what could have happened."
Research Report:Protocells by spontaneous reaction of cysteine with short-chain thioesters
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