hydrothermal production of amphiphilic molecules from pyruvate
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HYDROTHERMAL PRODUCTIONOF AMPHIPHILIC MOLECULES
FROM PYRUVATE
HYDROTHERMAL PRODUCTIONOF AMPHIPHILIC MOLECULES
FROM PYRUVATE
R. M. Hazen, G. D. Cody, D. W. Deamer, H. S. Yoder, Jr.,J. Blank, A. Sharma, H. Morowitz
ACS Session on Hydrothermal ChemistrySan Diego, 5 April 2001
HAROLD MOROWITZ’S QUESTION
HAROLD MOROWITZ’S QUESTION
• Will hydrothermal conditions promote the carboxylation of pyruvic acid?
Experimental RationaleExperimental Rationale
• These experiments are not intended to mimic a prebiotic geochemical environment.
• They are intended to explore reaction pathways of pyruvic acid under hydrothermal conditions.
• Once such pathways are deduced, then additional experiments to optimize select pathways under plausible prebiotic conditions may be warranted.
Reactions of Pyruvic AcidReactions of Pyruvic Acid
Temperature = 150 to 300 C; Pressure = 0.05 to 0.5 GPa
•
Reactions of Pyruvic Acid – Methylsuccinic Acid
Reactions of Pyruvic Acid – Methylsuccinic Acid
Methylsuccinic acid forms by dimerization and subsequent decarboxylation of pyruvic acid.
•
Wilhelmy Plate AnalysisWilhelmy Plate Analysis
Surface active molecules reduce the surface tension of water. This response is typical of vesicle-forming molecules
•
SELDISELDI
Laser desorption/ionization time-of-flight mass spectrometry reveals homologous series of polymerization reactions.
•
100 200 300
Mass (Daltons)
I
Reactions of Pyruvic Acid – Substituted AromaticsReactions of Pyruvic Acid – Substituted Aromatics
A complex suite of substituted aromatic molecules forms by Aldol condensation and subsequent cycloaddition reactions.
•
Decarboxylation of Pyruvic AcidDecarboxylation of Pyruvic Acid
HDAC observations of CO2 formation.
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Raman Spectrum of Pyruvic Acid(Room conditions in HDAC)
Raman Spectrum of Pyruvic Acid(Room conditions in HDAC)
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Raman Spectra of Pyruvic Acid(P & T in HDAC)
Raman Spectra of Pyruvic Acid(P & T in HDAC)
•
Stability of Pyruvic Acid at P and T
Stability of Pyruvic Acid at P and T
In 2-hour experiments, pyruvic acid is rapidly consumed.
•
Reaction of Pyruvic Acid to Methylsuccinic Acid
Reaction of Pyruvic Acid to Methylsuccinic Acid
Maximum yields occur at 250 C and low pressure.
•
Reaction of Pyruvic Acid to “Product B”
Reaction of Pyruvic Acid to “Product B”
P and T both enhance yields of aromatic compounds.
•
Hydrothermal Organic SynthesisHydrothermal Organic Synthesis
• Gold tube reactors in an internally-heated, gas-media, high-pressure apparatus
Hydrothermal Organic SynthesisHydrothermal Organic Synthesis
• Hydrothermal Diamond
Anvil Cell
Hydrothermal Organic Synthesis - HDAC
Pyruvic AcidPyruvic Acid
• Reactants:Pyruvic acid + CO2 + H2O
• Conditions:200
oC
2,000 atm2 hours
• Products:A diverse suite of organic molecules
Self-Assembly of AmphiphilesSelf-Assembly of Amphiphiles
Amphiphilic molecules are observed to assemble into bilayers.
Amphiphilic components extracted from the Murchison meteorite form membrane-like structures.
0.2 m
2-D Liquid Chromatography2-D Liquid Chromatography
Silica gel plate in visible light Silica gel plate in UV light
Comparison with Murchison OrganicsComparison with Murchison Organics
Pyruvic acid reactants Murchison meteorite
Comparison with Murchison OrganicsComparison with Murchison Organics
Pyruvic acid reactants Murchison meteorite
Vesicle formation in phosphate buffer solution (pH = 8.5)
Comparison with Murchison OrganicsComparison with Murchison Organics
Pyruvic acid reactants – tof MS Murchison alkanes - GC
Analyses of vesicle-forming fraction
Amphiphiles from Pyruvic AcidForm Vesicles
Amphiphiles from Pyruvic AcidForm Vesicles
Pyruvic Acid Plays an Important Metabolic Role
Pyruvic Acid Plays an Important Metabolic Role
The carboxylation of pyruvic acid is an entry point to the reductive TCA cycle.
ConclusionsConclusions
• We did not observe the reaction of pyruvic acid + CO2 to oxaloacetic acid under our range of P, T, and X in the pure system C-O-H.
• Polymerization of pyruvic acid and its products occurs readily under hydrothermal conditions. Temperature and pressure have a significant effect on the product suites and yields.
• Products of pyruvic acid reactions under hydrothermal conditions include a suite of vesicle-forming amphiphiles.
ConclusionsConclusions
• Similarities between our experimental products and Murchison meteorite organics suggest a similar robust polymerization chemistry.
• One goal of prebiotic synthesis experiments should be to document the range of plausible environments for such organic synthesis. We can’t evaluate the role of high-pressure and hydrothermal environments without doing the experiments.
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