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ANR funded project

Défi de tous les savoirs (DS10)
Edition 2015


PREBIOM


Primitive Earth - Biomolecules Interacting with hydrothermal Oceanic Minerals

Which role did mineral surfaces play in the emergence of Life?
The aim of the PREBIOM project is not to solve the whole issue of the origin of life but to focus on one aspect that is amenable to a few years' time frame : the concentration of the elementary building blocks of life such as amino acids and nucleotides on mineral surfaces to concentrations allowing polymerization, a prerequisite to the formation of the proto-biopolymers of proteins and nucleic acids.

Interactions between prebiotic molecules and minerals' surfaces in the context of the early Earth and origin of life
We recognize the existence of other explanations for the rise in biological complexity, and we do not exclude them, but the focus of the project is to explore the chemistry that occurs at mineral surfaces. The PREBIOM project (Primitive Earth Biomolecules Interacting with Oceanic Minerals) focuses on the minerals that were abundant in the Hadean oceans and the pressure and temperature conditions characteristics of oceanic hydrothermal systems. We target a series of minerals that could be formed from the hydrothermal alteration of peridotites, komatiites, basalts and gabbros. They include serpentine minerals, talc, brucite, magnesium and iron-rich clay minerals, iron oxides and sulfides. Adsorption isotherms of amino acids and nucleotides will be measured at ambient pressure when not yet available as well as under hydrothermal conditions. Adsorption of organic molecules under hydrothermal conditions has never been investigated, although hydrothermal organic synthesis has already revealed facile reaction mechanisms for the production and polymerization of a variety of biomolecules. Interpretation of adsorption isotherms with in situ and ex situ spectroscopic analyses of the adsorbed biomolecules and theoretical calculations should lead to a detailed understanding of the reaction mechanisms for condensation, adsorption and polymerization. In addition to the above minerals, the experiments will also be performed on the one hand on high-surface silica as a reference material and on the other hand on natural samples of hydrothermal black and white chimneys representative of the three types of hydrothermal venting systems known to date.

Adsorption isotherms on well-characterized mineral surface, hydrothermal experiments, X-ray and vibrational spectroscopies, adsorption mechanisms
Most of the targeted iron and magnesium-rich minerals that could result from the hydrothermal alteration of peridotites, komatiites, basalts and gabbros have been purchased and/or synthesized. Their specific surface area has been measured by BET from nitrogen sorption isotherms. TEM allows determining the average particle dimensions and Small Angle X-ray Scattering (SAXS) is used to complement data as necessary. CEC is measured by exchanging the cations with the hexamminecobalt(III) cation. High-resolution gas adsorption and AFM is also used to assess the morphological properties of the minerals. This suite of methods best constrains the specific surface area of the minerals.
Condensation, adsorption and polymerization experiments are performed following conventional protocols well established in the different groups. One experimental novelty in this project will be the adsorption experiments under hydrothermal conditions, at the pressure, temperature and redox conditions characteristics in hydrothermal vents. Adsorption is quantified using UV-Vis spectroscopy to measure the adsorption yield, including the measurement of adsorption isotherms. Thermogravimetric analyses provide the data for condensation and polymerization. The mechanisms of condensation, adsorption and polymerization will be investigated also using X-ray diffraction and a series of complementary spectroscopic techniques all available in the PREBIOM team. Most analyses will be done ex situ, while some in situ measurements will be performed at the LGL (Lyon) that is equipped to perform in situ spectroscopy at high pressure and temperature.
Interpretations of the experimental data in terms of yield and mechanism of the reactions will strongly benefit from the molecular simulations and macroscopic surface complexation models. Collaborative experimental and theoretical work is new to this topic.

Results

We studied the adsorption of RNA and DNA monomers on minerals that were abundant in the early Earth environment as the result of aqueous or hydrothermal alteration of the primitive oceanic crust. It included Fe-Mg rich swelling clays and non-swelling phyllosilicates suspended in an aqueous saline solution analog to seawater. We found that DNA adsorbs much more strongly than RNA, and that any monomer containing the G nucleobase adsorbed more strongly than one containing the C nucleobase. We could infer that all nucleotides behave as homologous molecules in regard to their adsorption onto the studied mineral surfaces. At low to moderate surface loadings and pH 7, adsorption certainly proceeds by ligand exchange between the phosphate group and the hydroxyls of the broken edges of phyllosilicates leading to the saturation of lateral surfaces. Below pH 4, swelling clays also adsorb nucleotides through cation exchange on basal surfaces. We propose that Fe-Mg rich phyllosilicates tightly bind nucleotides and concentrate them up to 1000 times the solution concentration under ambient conditions. Nontronites have the most diverse and favorable adsorption behaviors and could have helped to the concentration and polymerization of nucleotides under primitive Earth-like conditions. Although the salinity of the primitive ocean is still a matter of debate, we could show that the adsorption capacity of swelling clays is very sensitive to the actual salinity and composition of the ocean. An hadean ocean richer in divalent cations that the modern ocean would strongly enhance the role of clay surfaces with respect to their adsorption capacity toward nucleotides and potentially favor their polymerization.
Finally, we could show that amino acids polymerize rapidly under hydrothermal conditions over a limited pressure range and the yield of the reaction depends on the presence of catalyst minerals such as magnetite.

Outlook

The PREBIOM project deals with a fundamental question that has been the subject of passionate debates, i.e. the mechanisms through which life could have emerged on planet Earth. We cannot reasonably expect major technological or economical effect from the PREBIOM project. The conclusions that we hope to establish in terms of the relevance of the hydrothermal origin of life in interaction with mineral surfaces could have a significant impact on the scientific community working on the fundamental question of the origin of Life, and may, in addition, generate some interest to a broader audience.

Scientific outputs and patents

Three PhD candidates have already worked on the PREBIOM project. One of them has already defended her PhD thesis and two will defend in the autumn. Three graduate students and many undergraduates have benefited from the support of the PREBIOM project.
Six publications have been published or are about to be published and the results have been presented in ten communications at national and international conferences.

Partners

GL John Hopkins University and Carnegie Institution of Washington

LIEC-UMR 7360 Laboratoire Interdisciplinaire des Environnements Continentaux

LRS CNRS DR IDF SECTEUR PARIS B

PHENIX CNRS DR IDF SECTEUR PARIS B

UCBL UNIVERSITE LYON 1 CLAUDE BERNARD

ANR grant: 353 392 euros
Beginning and duration: novembre 2015 - 42 mois

Submission abstract

The question of the origin of life is a long standing one, the answer to which is likely to be very complex and require the consideration of concepts from many disciplines including biology, chemistry, astrophysics, and the Earth and Planetary sciences. The aim of this proposal is not to solve the whole issue of the origin of life but to focus on one aspect that is amenable to the time frame of a 3.5 year proposal: the concentration of the elementary building blocks of life such as amino acids and nucleotides on mineral surfaces to levels allowing polymerization, a prerequisite to forming the proto-biopolymers of proteins and nucleic acids. We recognize the existence of other explanations for the rise in biological complexity, and we do not exclude them, but the focus of our proposal is to explore the chemistry that occurs at mineral surfaces.
The PREBIOM proposal (Primitive Earth Biomolecules Interacting with Oceanic Minerals) focuses on the minerals that were abundant in the Hadean oceans and the pressure and temperature conditions characteristics of oceanic hydrothermal systems. We target a series of minerals that could be formed from the hydrothermal alteration of peridotites, komatiites, basalts and gabbros. They include serpentine minerals, talc, brucite, magnesium and iron-rich clay minerals such as nontronite and saponite, iron oxides and sulfides. Adsorption isotherms of amino acids and nucleotides will be measured at ambient pressure when not yet available as well as under hydrothermal conditions. To the best of our knowledge, adsorption of organic molecules under hydrothermal conditions has never been performed, although hydrothermal organic synthesis has already revealed facile reaction mechanisms for the production and polymerization of a variety of biomolecules. Interpretation of adsorption isotherms with in situ and ex situ spectroscopic analyses of the adsorbed biomolecules and theoretical calculations should lead to a detailed understanding of the reaction mechanisms for condensation, adsorption and polymerization. In addition to the above minerals, the experiments will also be performed on the one hand on high-surface silica as a reference material and on the other hand on natural samples of hydrothermal black and white chimneys representative of the three types of hydrothermal venting systems known to date. A limited number of biomolecules have been chosen to focus on representative interaction mechanisms with the selected minerals.
The PREBIOM interdisciplinary consortium is composed of 5 partners (LGL, Lyon; LRS, Paris; PhENIx, Paris; LIEC, Nancy; JHU/GL-CIW, USA) all of them already involved in the investigation of the interactions between organic molecules and mineral surfaces. Some partners in this consortium have collaborated. However the consortium has been significantly enlarged. It now involves complementary experimental, analytical and theoretical skills in mineralogy, chemistry, physical chemistry and geology. Collaborative experimental and theoretical work is new to this topic.
Results from the PREBIOM project are expected at various levels. The experimental and theoretical work proposed here will provide unique fundamental results on the condensation, adsorption and polymerization under thermodynamic conditions that have not yet been explored but were probably mandatory for the development of the abiotic organic synthesis of proteins and nucleic acids of intermediate length. They are a prerequisite to conduct any further (geo)chemical and thermodynamic modelling. The careful selection of mineral surfaces, biomonomers or simple molecules, and thermodynamic conditions will certainly put constraints on a suitable geological environment that may have witnessed some steps of the emergence of life on Earth. Project results will be broadly disseminated through publications and communications at international conferences and may in addition generate some interest to a broader audience.

 

ANR Programme: Défi de tous les savoirs (DS10) 2015

Project ID: ANR-15-CE31-0010

Project coordinator:
Madame Isabelle Daniel (UNIVERSITE LYON 1 CLAUDE BERNARD)

Project web site: http://prebiom.univ-lyon1.fr

 

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The project coordinator is the author of this abstract and is therefore responsible for the content of the summary. The ANR disclaims all responsibility in connection with its content.