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

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Reactions of Pyruvic Acid – Methylsuccinic Acid

Reactions of Pyruvic Acid – Methylsuccinic Acid

Methylsuccinic acid forms by dimerization and subsequent decarboxylation of pyruvic acid.

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Wilhelmy Plate AnalysisWilhelmy Plate Analysis

Surface active molecules reduce the surface tension of water. This response is typical of vesicle-forming molecules

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SELDISELDI

Laser desorption/ionization time-of-flight mass spectrometry reveals homologous series of polymerization reactions.

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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.

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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)

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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.

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Reaction of Pyruvic Acid to Methylsuccinic Acid

Reaction of Pyruvic Acid to Methylsuccinic Acid

Maximum yields occur at 250 C and low pressure.

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Reaction of Pyruvic Acid to “Product B”

Reaction of Pyruvic Acid to “Product B”

P and T both enhance yields of aromatic compounds.

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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.