Complexation of glycine by manganese (II) in the gas phase: A theoretical study

Structures, Unimolecular Fragmentations, and Reactivities of the Self‐Assembled Multimetallic/Peptide Complexes [Mnn(GlyGly‐H)2n−1]+ and [Mnn+1(GlyGly‐H)2n]2+

“…Khodabandeh et al also found a considerable contribution to the metal-ligand binding was from electrostatic interactions. [27] This is in agreement with the conclusions reached in Section 2.1.3 based on the similar fragmentation patterns observed for the present Mn 2 + complexes and those observed for similar Mg 2 + complexes in a previous study.…”

“…Based on the spectroscopic data as well as the computational thermochemistries, it is most likely that the complex observed is the sextet displayed in Figure 5. In a study by Khodabandeh et al [27] on Mn 2 + complexes of glycine, it was shown that in each of the high-(S = 5/2), intermediate-(S = 3/2), and low-spin (S = 1/2) multiplicity states, the lowest energy structures are zwitterionic forms, in which Mn 2 + is interacting with carboxylate oxygen and the amine hydrogens are hydrogen bonded to carbonyl oxygen. Also, the lowest energy structure among all the different spin states is the high-spin-state sextet.…”

Quantum localization/delocalization of muonium in the glycine–K+ complex

“…It is seen that four structures (EQ 0 , EQ 1 , EQ 2 , EQ 3 ) are more stable than other structures and have comparable relative energies at this B3LYP/6-31+G(d) level without zero-point correction. This result is in good agreement with previous theoretical studies [29][30][31][32][33][34][35][36][37][38][39][40][41][42]. The EQ 2 structure is stabilized by the presence of the five-membered ring and by attractive electrostatic interactions between K + and negative charges on carboxylic oxygen and the amine nitrogen.…”

“…In addition, it should be pointed out that the interaction between potassium cation and protein plays an especially important role in the selective transport phenomenon across cell membrane. Although many structures of the glycine-K + complex have been extensively studied in the past, we have also characterized the potential energy surface profile of this system using the GRRM (Global Reaction Route Mapping) computational algorithm [43][44][45][46] (which will be described below in detail), that can automatically find all possible local minima and transition states on a given multi-dimensional potential energy surface, to confirm the previous results [29][30][31][32][33][34][35][36][37][38][39][40][41][42]. Fig.…”

“…It is also known that metal-cation binding to amino acid molecules significantly affects the relative stability of various amino acid conformers [29][30][31][32][33][34][35][36][37][38][39][40][41][42]. In particular, there have been many theoretical studies on structures and stability of the complexes between metal-cation and glycine [29][30][31][32][33][34][35][36][37][38][39][40][41][42], the simplest amino acid molecule. Among various metal ions, we here focus on the glycine-K + complex since previous electronic structure studies have shown that energy levels of the neutral and zwitterionic forms are comparable (nearly thermoneutral) and that the proton-transfer barrier height is known to be relatively low of a few kcal/mol.…”