An Experimental and Theoretical Investigation of Gas‐Phase Reactions of Ca²⁺with Glycine

Abstract

The gas-phase reactions between Ca(2+) and glycine ([Ca(gly)](2+)) have been investigated through the use of mass spectrometry techniques and B3-LYP/cc-pWCVTZ density functional theory computations. The major peaks observed in the electrospray MS/MS spectrum of [Ca(gly)](2+) correspond to the formation of the [Ca,C,O(2),H](+), NH(2)CH(2) (+), CaOH(+), and NH(2)CH(2)CO(+) fragment ions, which are produced in Coulomb explosion processes. The computed potential energy surface (PES) shows that not only are these species the most stable product ions from a thermodynamic point of view, but they may be produced with barriers lower than for competing processes. Carbon monoxide is a secondary product, derived from the unimolecular decomposition of some of the primary ions formed in the Coulomb explosions. In contrast to what is found for the reactions of Ca(2+) with urea ([Ca(urea)](2+)), minimal unimolecular losses of neutral fragments are observed for the gas-phase fragmentation processes of [Ca(gly)](2+), which is readily explained in terms of the topological differences between their respective PESs.

Complexation of Ca2+ with selenocysteine and effects on its intrinsic acidity

“…Also, in agreement with the behavior reported for serine, 25 the global minimum of the [Sec-Ca] 2+ PES is a CS structure, what is at variance with glycine, 46 where the global minimum of the PES is a SB structure. The interconversion between local minima of the [Sec-Ca] 2+ PES is reported in Figure 4.…”

Ab initio modelling of protein–biomaterial interactions: influence of amino acid polar side chains on adsorption at hydroxyapatite surfaces

“…It is well known that the most stable gas-phase [Ca-Gly] 2+ isomer exhibits Gly in its zwitterionic state [60]; however, structural information on the remaining [Ca-AA] 2+ ion complexes is scarce. Thus, we simulated the [Ca-AA] 2+ ion complexes, in which the AAs are both in their neutral and zwitterionic state.…”

Theoretical Study of the Interaction of 1,2-Dithiolene Ligands with the Mg2+ and Ca2+ Aquacations: Electronic, Geometric and Energetic Analysis

“…Several studies report this methodology to determine the strength of binding of metal cations and ligands. [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][38][39][40][41][42][43][44][45][46][47] …”

“…Yánez et al 34 extensively studied the interaction of metal cations with O-, N-and S-coordinating ligands. [31][32][33][34] Geometrical, electronic and energetic characteristics of the complexes and the isolated ligands were rationalized to explain metal-ligand affinity trends. It was found that the peripheral groups bonded to the anchoring atom that binds to the metal cation modulate the interaction strength.…”

“…21 The interaction between divalent metal cations and organic ligands was analyzed in a large number of studies. [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] The interaction of alkaline earth metal cations with Oand N-coordinating ligands was quantified by binding energies, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies and energy gap values as well as metal-ligand bond length, and ligand-to-metal electronic donation. It was seen that the O-coordinating ligands have the largest affinity for those cations.…”