Inorganic Phosphate and Nucleotides on Silica Surface: Condensation, Dismutation, and Phosphorylation

We explore the reactivity of inorganic monophosphate ions (Pi) and 5′-adenosine monophosphate (AMP), adsorbed onto amorphous silica separately or together. This question has relevance for prebiotic chemistry scenarios and, more generally, for biomedical applications involving biomolecule adsorption. XRD, TGA, and ³¹P and ²⁹Si NMR results show that inorganic phosphate ions deposited on silica condense to polyphosphates at considerably lower temperatures than in bulk KH₂PO₄. In the same temperature range, AMP adsorbed alone undergoes dismutation reactions, yielding adenosine, ADP, and ATP; in this case, the effect of the silica surface is not obvious. When AMP and Pi are coadsorbed on silica at high loadings (5–10%), AMP dismutation and phosphorylation by Pi both occur, allowing the formation of ADP and ATP. The latter result clearly shows the ability of silica surfaces to promote the formation of molecules generally considered as “high-energy” compounds and opens the way to further research on the effect of mineral surfaces for nucleotide synthesis and ribose stabilization

Selectivities in Adsorption and Peptidic Condensation in the (Arginine and Glutamic Acid)/Montmorillonite Clay System

The present study examines the selective adsorption and polymerization of two amino acids, glutamic acid (Glu) and arginine (Arg), on a cationic clay mineral, montmorillonite (Mt). Two experimental procedures were used: selective adsorption and wet impregnation. In the first case, an adsorption selectivity is observed based on pH-dependent speciation of the amino acids. At natural pH, arginine is positively charged and thus extensively exchanges the cations in the interlayer space of the montmorillonite whereas glutamic acid is negatively charged and adsorbed in weak amounts, probably on the clay edges. In contrast, incipient wetness impregnation forces equivalent quantities of both amino acids to be deposited. After moderate thermal activation, combined characterization techniques, especially solid-state NMR and matrix-assisted laser desorption ionization time-of-flight analysis, highlight a peptidic condensation between the amino acids and hint at a selective polymerization yielding preferably heteropeptides (e.g., cyclo­(Glu-Arg)) rather than homopeptides