Tandem mass spectrometry of Cu(II) complexes: the effects of ligand donor group on dissociation

Chaparro, Amanda L.; Vachet, Richard W.

doi:10.1002/jms.446

Cited by 24 publications

(16 citation statements)

References 62 publications

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“…Theoretical calculations are also used to generate the candidate structures of the peptide-metal ion complex, which provide theoretical evidences to support our experimental observations. In related work, Vachet and coworkers compared the effects of ligand donor group on dissociation of Cu(II) complexes, and their results suggest that Cu 2ϩ ions prefer to remain coordinated to thio group rather than other functional groups such as amino and imidazole [31,32]. Kass and coworkers utilized H/D exchange experiments and high level calculations to compare the gas-phase acidities of the cysteine thiol group and carboxyl group [33].…”

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confidence: 99%

Amino acid influence on copper binding to peptides: Cysteine versus arginine

Fernandez-Lima

Russell

2010

J. Am. Soc. Mass Spectrom.

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Matrix assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) and theoretical calculations [density functional theory (DFT)] were utilized to investigate the influence of cysteine side chain on Cu(+) binding to peptides and how Cu(+) ions competitively interact with cysteine (-SH/SO(3)H) versus arginine. Results from theoretical and experimental (fragmentation reactions) studies on [M + Cu](+) and [M + 2Cu - H](+) ions suggest that cysteine side chains (-SH) and cysteic acid (-SO(3)H) are important Cu(+) ligands. For example, we show that Cu(+) ions are competitively coordinated to the -SH or SO(3)H groups; however, we also present evidence that the proton of the SH/SO(3)H group is mobile and can be transferred to the arginine guanidine group. For [M + 2Cu - H](+) ions, deprotonation of the -SH/SO(3)H group is energetically more favorable than that of the carboxyl group, and the resulting thiolate/sulfonate group plays an important role in the coordination structure of [M + 2Cu - H](+) ions, as well as the fragmentation patterns.

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confidence: 99%

Amino acid influence on copper binding to peptides: Cysteine versus arginine

Fernandez-Lima

Russell

2010

J. Am. Soc. Mass Spectrom.

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“…H 2 (99.99%) was obtained from Merriam Graves (Springfield, MA). Additional details for the syntheses of these ligands can be found in previous publications [18,21].…”

Section: Ligand and Metal Complex Synthesismentioning

confidence: 99%

Gas-phase reactions of divalent Ni complex ions with acetonitrile: Chelate ring size, inductive, and steric effects

Combariza

Vachet

2004

J. Am. Soc. Mass Spectrom.

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Ni(II) complexes of a series of pentadentate polyamine ligands have been reacted with CH 3 CN in the gas phase using a modified quadrupole ion trap mass spectrometer. The ligands have structural features such that upon complexation, chelate ring size, sterics, and inductive effects can be evaluated in the gas phase. Rate and equilibrium constants for CH 3 CN addition to the metal complexes show that there is a general decrease in the gas-phase reactivity as the chelate ring size is increased. Density functional theory calculations at the B3LYP/LANL2DZ level of theory have been used to obtain minimum energy structures and Mulliken charges for the complexes. The decreased reactivity observed as the chelate ring size is increased correlates with a decrease in the atomic charge on the metal. A larger chelate ring size enhances ligand flexibility and improves the overlap of the ligand's donor atoms with the metal center. Adding methyl groups adjacent to or on the nitrogen donor groups of a ligand also decreases the rate and equilibrium constants for the reactions of a given complex with CH 3 CN. Analysis of Mulliken charges for these complexes indicates that both inductive and steric effects are responsible for lower complex reactivity. These results suggest that while the gas-phase reactivity of a metal complex with CH 3 CN is very dependent on the functional groups directly bound to the metal, in some cases steric effects can conceal the correlation between reactivity and coordination structure. T he chemistry of transition metal ions is quite diverse mainly because they can be tuned by the type, number, and orientation of the ligands coordinated to them. Knowledge of this coordination sphere provides insight into metal complex reactivity, and a variety of techniques including X-ray spectroscopies, NMR, and electron paramagnetic resonance (EPR) have been used to gather coordination structure information. If metal complexes are present at low concentrations or in complicated mixtures, though, these techniques can have difficulty providing coordination structure. Consequently, we have begun to investigate the advantage of using mass spectrometry (MS) to gather coordination structure information.For several reasons we have chosen not to rely on the typical dissociation methods (e.g., collision-induced dissociation [CID]) for acquiring metal complex structural information by MS. One reason is that, while the dissociation patterns and dynamics of metal complexes have not been exhaustively studied, most results indicate that rearrangement reactions involving the loss of small neutrals from large ligands or the loss of intact ligands from multi-ligated metal ions are typical [1][2][3][4][5][6][7][8][9][10][11]. Unfortunately, neither provides much insight into the coordination sphere, as they do not necessarily reveal whether the groups lost were coordinated to the metal or not. Furthermore, during collisional activation, even at low energies, scrambling of the metal's coordination sphere can occur because of relatively w...

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“…Numerous multidentate ligands have been evaluated for suitability in such experiments [26][27][28] crown ethers, and their derivatives. Most experiments have used divalent copper as the metal in these ternary complexes, but other metal ions have also been tried [26,29].…”

Section: Introductionmentioning

confidence: 99%