The fate of amino acids adsorbed on mineral matter |
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Authors: | Jean-François Lambert Lorenzo Stievano Irène Lopes Marwen Gharsallah Lingyu Piao |
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Institution: | a UPMC University Paris 6, Laboratoire de Réactivité de Surface, Case courrier 178, 4 Place Jussieu, 75252 Paris Cedex 05, France b CNRS, UMR 7609, France |
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Abstract: | We present here selected results recently obtained on the molecular characterization of amino acids adsorption on oxide minerals and their further polymerization by thermal activation, in the general frame of assessing Bernal's hypothesis on the origin of biopolymers on mineral surfaces. Adsorption mechanisms may be identified by a combination of vibrational spectroscopy, 13C solid-state NMR, and molecular modeling. Depending on a particular amino acid, the oxide surface investigated, and the water activity during adsorption (i.e., whether it is carried out from the gas phase or from an aqueous solution), contributions from electrostatic adsorption, outer-sphere and inner-sphere (coordination) complexes may be observed. These mechanisms result in significant adsorption selectivities from equimolar mixtures of different amino acids. Upon thermal activation at moderate temperatures (150-160 °C), clean polymerization events occur and can easily be observed by thermogravimetric analysis. There are some hints of selectivity in this step too. The water activity during thermal treatment plays an important role for the thermodynamics of polymerization. |
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Keywords: | Amino acids Oxide minerals Adsorption mechanism Polymerization Selectivity |
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