Modelling peptide–metal dication interactions: formamide–Ca2+ reactions in the gas phase

Abstract

The collision induced dissociation of formamide-Ca(2+) complexes produced in the gas phase through nanoelectrospray ionization yields as main products ions [CaOH](+), [HCNH](+), [Ca(NH(2))](+), HCO(+) and [Ca(NH(3))](2+) and possibly [Ca(H(2)O)](2+) and [C,O,Ca](2+), the latter being rather minor. The mechanisms behind these fragmentation processes have been established by analyzing the topology of the potential energy surface by means of B3LYP calculations carried out with a core-correlated cc-pWCVTZ basis set. The Ca(2+) complexes formed by formamide itself and formimidic acid play a fundamental role. The former undergoes a charge separation reaction yielding [Ca(NH(2))](+) + HCO(+), and the latter undergoes the most favorable Coulomb explosion yielding [Ca-OH](+) + [HCNH](+) and is the origin of a multistep mechanism which accounts for the observed loss of water and HCN. Conversely, the other isomer of formamide, amino(hydroxyl)carbene, does not play any significant role in the unimolecular reactivity of the doubly charged molecular cation.

The key role of meteorites in the formation of relevant prebiotic molecules in a formamide/water environment

“…Transition metal ions very efficiently coordinate aliphatic amides, achieving their maximum coordination number31. Alkaline earth metals and transition metal ions coordinate the nucleophilic centers in NH 2 CHO, to yield complexes with different geometries and stabilities, which are known to lose water in the presence of high energy sources to yield HCN32, one of the key intermediate in the synthesis of both nucleobases and carboxylic acids (SI #8). Different transition metal compounds have been recently reported as efficient catalysts for the prebiotic synthesis of a large panel of prebiotic molecules from NH 2 CHO in geochemical scenarios33.…”

Unimolecular Reactivity of the [Urea-Sr]2+Complex, a Metastable Dication in the Gas Phase: An Experimental and Theoretical Perspective

“…Several types of ions are observed. Like for previous studies involving either Ca 2+30, 33,36,38,59,60 or Sr 2+ , 39 Finally, due to the presence of acetonitrile in trace amounts, a [Sr(CH 3 CN)] 2+ complex is also detected at m/z 64.46. Such doubly charged complexes have been already observed with alkaline-earth dications such as Ca 2+ or Sr 2+ .…”

Theoretical Methods for Vibrational Spectroscopy and Collision Induced Dissociation in the Gas Phase

“…The reaction pathways identification (quite a tricky problem for large systems) is often guided by experiments: only products compatible with m/z observed in CID experiments are studied. This was the case for Ca 2+ /formamide [115], Ca 2+ /urea [116], or uracil interacting with Ca 2+ , Pb 2+ , Cu 2+ , or Na + [117] dissociation studies of Yanez, Salpin, and co-workers.…”