Interaction of Alkali Metal Cations (Li+-Cs+) with Glycine in the Gas Phase: A Theoretical Study

Abstract

The complexes formed by alkali metal cations (Cat ) and glycine (Gly) were studied by means of ab initio quantum chemical methods. Seven types of Gly ± Cat interaction were considered in each case. It was found that in the most stable forms of Gly ± Li and Gly ± Na the metal ion is chelated between the carbonyl oxygen and nitrogen ends of glycine. For Gly ± K an isomer involving complexation with both oxygens of the carboxylic function is found to be degenerate with the above chelate, and becomes slightly more stable for Gly ± Rb and Gly ± Cs. In all cases, interaction of the ion with the carboxylate group of zwitterionic glycine is also low in energy. Computed binding energies (DH 298 , kcal mol À1

Observation of zwitterion formation in the gas-phase H/D-exchange with CH3OD: Solution-phase structures in the gas phase

“…Modeling of observed HDX processes and quantum chemical calculations of the potential surfaces have made a strong circumstantial case that ZW structures are traversed in many cases during HDX with basic partners like D 2 O, CH 3 OD, and ND 3 [14,16,18]. Nevertheless, computations also generally indicate that the bare ZW is sufficiently disfavored energetically that its equilibrium presence in the M ϩ /amino acid would be negligible [22,23].Here, we show unambiguous spectroscopic evidence that bare ZW can in fact be kinetically trapped as a result of the HDX of [Trp ϩ K] ϩ with CH 3 OD. Infrared multiple-photon dissociation (IR-MPD) spectroscopy of metal-tagged amino acids and peptides has already been shown to be a powerful probe for CS or ZW conformers in the gas phase [24 -28]; the chemically…”

“…Modeling of observed HDX processes and quantum chemical calculations of the potential surfaces have made a strong circumstantial case that ZW structures are traversed in many cases during HDX with basic partners like D 2 O, CH 3 OD, and ND 3 [14,16,18]. Nevertheless, computations also generally indicate that the bare ZW is sufficiently disfavored energetically that its equilibrium presence in the M ϩ /amino acid would be negligible [22,23].…”

Gas phase H/D exchange of sodiated amino acids: Why do we see zwitterions?

“…The next step is a migration of sodium cation from one side of the carboxylic group to the middle, through the transition-state TS45, which is only 0.6 to 1 kJ mol It is important to notice that a single molecule of water is sufficient to change conformation of sodiated amino acid. These findings also support assumptions made by Hoyau et al [23,24] that binding of an additional ligand (D 2 O or ND 3 ) to GlyNa ϩ would provide enough energy for CS-ZW isomerization.…”

Glycine-Zn+/Zn2+ and their hydrates: On the number of water molecules necessary to stabilize the switterionic glycine-Zn+/Zn2+ over the nonzwitterionic ones

“…Table X displays the binding energy cases for the two modes of NO and OO, in which ⌬E, ⌬E 1 , and ⌬E 2 stand for the binding energies between each of the two selected glycine isomers and bound Zn ϩ , between their complexes and the first and further the second combined water molecules, respectively. BSSE is also taken 2 , ⌬E 1 , ⌬E) and the deformation (⌬E def ) and electrostatic (⌬E elec ) contributions of ⌬E obtained at the B3LYP/6-311ϩG*//HF/6-31G* ͑B3͒ and BHLYP/6-311ϩG*//HF/6-31G* ͑BH͒ levels, respectively. Energy in the kcal/mol.…”

“…Recently, there has been a growing interest in the combination of metal ions with amino acid molecules [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and further combination with water molecules 16 due to its importance in the fields of catalysis, atmospheric chemistry or biochemistry, especially in the biochemical fields. The interaction between a metal ion and a single hydrated amino acid is essential building blocks for our understanding of the role of metal ions in the structure and function of proteins, nucleic acids and peptide hormones, which are yet often unknown, at the atomic and electronic level, while the nature of watermetal ion-biomolecule interactions remains nebulous.…”