Primitive Earth – Biomolecules Interacting with hydrothermal Oceanic Minerals

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.

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.