Task 3 – Adsorption of biomolecules on minerals surfaces and activation under ambient pressure and controlled water activity
Task leader Jean-François Lambert
Participants LRS PhENIx LIEC
- Evaluation of biomolecules condensation reactions at ambient pressure
- Dependency on water activity
- Reversibility of condensation and adsorption
- Experimental determination of thermodynamic parameters
Description of work
- Measurement of adsorption isotherms
- Calorimetric experiments during adsorption of biomolecules
- Monitoring condensation reactions by thermal analysis
- Characterization of adsorbed biomolecules before and after thermal activation (XRD, Raman and IR spectroscopies, solid state NMR, XPS, NAP-XPS, high-resolution gas adsorption, STXM)
- Desorption of biomolecules, identification in solution by MALDI-TOF analysis
Role of participants
J-F. Lambert (LRS): task leader, coordination with tasks 2 and 4
M. Jaber (LRS): spectroscopic characterization (solid-state NMR)
T. Georgelin (LRS): spectroscopic characterization (Raman and IR), MALDI-TOF analysis
M. Akouche (LRS): adsorption and desorption of nucleotides
Post-doc (to be hired): amino acids adsorption and desorption isotherms, thermal analysis and monitoring of condensation reactions in conditions of controlled water activity
L. Michot (PhENIx): Spectroscopic characterization (NAP XPS, STXM)
A. Razafitinamaharavo (LIEC): High-resolution gas adsorption
Risks and contingency plan
The proposed methodology has already been successfully used to evidence peptide bond formation for several amino acids on different substrates, and recently to evidence ribose and nucleotide phosphorylation reactions, which are closely related to nucleotide polymerization. There is little doubt that it will provide valuable information
Deliverables / milestones
D3.1 – identification of the most reactive systems (toward condensation reactions) for further in-depth characterization
D3.2 – understanding of adsorption mechanisms on the systems selected in D3.1 (in close cooperation with task 5)
D3.3 – understanding the mechanisms of catalytic activation of biomolecules through their interaction with surface sites
M3.1 – A list of model minerals classified with respect to their efficiency in catalyzing condensation reactions (to be used in task 4; m12)
M3.2 – An identification of adsorption mechanisms of amino acids and nucleotides on said minerals (m24)
M3.3 – At least partial identification of surface-catalyzed reaction pathways leading to condensation of amino acids and nucleotides (m36)
D3.1 identification of the most reactive systems (toward condensation reactions) for further in-depth characterization
Two very promising systems have been identified, namely (Glu+Leu)/SiO2 and (Asp+Val)/SiO2. They show high-yield polymerization to linear oligopeptides up to n = 11 upon simple thermal activation to moderate temperatures (120-150°C). It breaks the record of polymer length for preparations in prebiotically realistic conditions. A preliminary report on these systems has been submitted for publication.
D3.2 and M3.2 Understanding of adsorption mechanisms on the systems selected in D3.1
Macroscopic studies, IR and preliminary NMR data indicate that the adsorption mechanisms on silica involve the formation of specific patterns of H-bonds. A Ph. D. thesis (Hagop Abadian) is being devoted to in-depth understanding of these adsorption mechanisms using advanced solid-state NMR methods. Additional information is available for adsorption mechanisms on clays (ion-exchange, except for acidic AAs), Fe oxides, and sulfides.
D3.3 and M3.3 Understanding the mechanisms of catalytic activation of biomolecules through their interaction with surface sites
Advanced Mass Spectrometric (FT-ICR) characterization of the peptides produced by catalytic activation of the amino acids has proved very useful to understand the peptide condensation reaction. Elementary steps involved in the formation of short peptides, and from there of longer ones, can be identified in this way.
A Ph.D. thesis will start in October 2018 with the aim to perfect the analytical methods applied to this problem and make them quantitative. Molecular level understanding of the mechanisms for each step will constitute the following stage in the elucidation of polypeptides formation, and is connected to D3.2.
M3.1 A list of model minerals classified with respect to their efficiency in catalyzing condensation reactions
Among tested materials, condensation reactions are most efficient on silica in terms of overall yield. They often, however, produce the evolutionary “dead end” DKP. Higher yields of oligopeptides are obtained on some Fe oxides, and on CuS (covellite). Swelling clay minerals (nontronite and montmorillonite) are not very efficient, and tend to activate decomposition reactions such as decarboxylation.