Attachment, Selection, and Transformation of Prebiotic Molecules on Brucite [MgOH2] and the Implications for Chemical Evolution at Hydrothermal Systems

brucite;aspartate;ribose;amino acids;calcium;origins of life;serpentinite-hosted hydrothermal vents;early Earth;Earth & Planetary Sciences

Estrada, Charlene FaeSverjensky, Dimitri A. ;

Johns Hopkins University

关键词: brucite;    aspartate;    ribose;    amino acids;    calcium;    origins of life;    serpentinite-hosted hydrothermal vents;    early Earth;    Earth & Planetary Sciences;   

Others  :  https://jscholarship.library.jhu.edu/bitstream/handle/1774.2/39330/EstradaThesis.docx?sequence=2&isAllowed=y

瑞士|英语

来源: JOHNS HOPKINS DSpace Repository

【 摘 要 】

Serpentinite-hosted hydrothermal vents may have been plausible environments for the origins of life. Mineral assemblages within hydrothermal fields may have selected and concentrated biomolecules, although little is known about molecular interactions at these mineral surfaces. I investigated the adsorption of aspartate and ribose at the surface of brucite [Mg(OH)2], a major mineral phase at serpentinite-hosted hydrothermal vents. I characterized the attachment of these molecules onto a synthetic brucite powder with Mg2+ and Ca2+ using batch adsorption experiments. I observed that Mg2+ inhibits both aspartate and ribose adsorption, whereas Ca2+ enhances adsorption onto the brucite surface. I used surface complexation modeling to predict that both aspartate and ribose attach as cooperative calcium-ligand complexes onto brucite.To further investigate the cooperative effect of Ca2+ on biomolecule adsorption, I introduced an equimolar mixture of aspartate, glycine, lysine, leucine, and phenylalanine to the brucite surface, both with and without Ca2+. Without Ca2+, up to 8.9 % aspartate and ~5 % each of the remaining four amino acids adsorbed onto brucite. When Ca2+ was added, I observed that between 5.7 to 20 times more aspartate (37.3 %) adsorbed onto brucite compared with the remaining four amino acids (~3 % each). These results, when combined with the previous study, suggest that aspartate selectively adsorbs onto brucite as a cooperative calcium-aspartate complex. The behavior of biomolecules at high temperatures is essential for evaluating whether hydrothermal systems may have been suitable environments for life’s origins. However, the geochemical complexities of a hydrothermal system could significantly affect this process. I characterized aspartate decomposition at 200 ºC and 15.5 bars for 24 hours in inert gold capsules with controlled redox state, added ammonia, and brucite. I determined that the initial experimental conditions significantly affect the decomposition of aspartate. Biomolecule decomposition may be a more complicated process within hydrothermal systems, which may contribute a diverse array of organic species to early Earth.