RNA decomposition by pyrite-induced radicals and possible role of lipids during the emergence of life

Generation of radical species (e.g., hydroxyl radical (OH)-O-.) by silicates is well documented, and it has been shown that these radicals can readily destroy biomolecules. While quartz and asbestos have received considerable attention, pyrite (FeS2), the most abundant iron sulfide, has received almost no attention in this context. Batch experiments were performed to determine the effects of pyrite-induced .OH on RNA in the presence and absence of lipids. The effect of the presence of lipids on RNA stability was evaluated by coating pyrite as well as encapsulating RNA in bilayer-vesicles. Rapid degradation of RNA was observed in the presence of pyrite, whereas significantly slower RNA decomposition was observed in experiments in the presence of lipids, regardless of whether the lipids were coating the pyrite or encapsulating the RNA. Given the presence of pyrite on early Earth, its reaction with water may have formed hydroxyl radicals (.OH), which could have limited the stability of prebiotic biomolecules critical to the emergence and evolution of life. The lipid-mediated reduction of RNA decomposition suggests a possible protective mechanism that could have been a prerequisite for the origin of life. (C) 2004 Elsevier B.V. All rights reserved.