Thermochemical properties of ion complexes Na+(M)n in the gas phase

Guo, Baochuan; Conklin, Breanna; Castleman, A. W.

doi:10.1021/ja00199a005

Cited by 118 publications

(93 citation statements)

References 4 publications

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“…Sodium ion adduction also shows a shift in the m o b i l i t y b et w e en th e t w o c om p ou n ds (Δ K 0 = 0.042 cm 2 /Vs; ΔCCS = 7.08 A 2 ). The most probable localization of the sodium ion is near the oxygen atom by ion-dipole attractions [41]. Therefore, the mechanism by which the conformation in the two structures changes most probably differs from the one proposed for silver cation adducts.…”

Section: Separation Of Isomers Employing Cation Adduct Formationmentioning

confidence: 88%

Adduct-ion formation in trapped ion mobility spectrometry as a potential tool for studying molecular structures and conformations

Zietek

Mengerink

Jordens

et al. 2017

Int. J. Ion Mobil. Spec.

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Recent developments in the field of ion mobility spectrometry provide new possibilities to explore and understand gas-phase ion chemistry. In this study, hyphenated trapped ion mobility spectrometry-mass spectrometry (TIMS-MS) was applied to investigate analyte ion mobility as function of adduct ion formation for twelve pharmaceutically relevant molecules, and for tetrahydrocannabinol (THC) and its isomer cannabidiol (CBD). Samples were introduced by direct infusion and ions were generated with positive electrospray ionization (ESI+) observing protonated and sodiated ions. Measurements were performed with and without addition of cesium-, lithium-, silver-and sodium ions to the samples. For the tested compounds, metal adduct ions with the same m/z but with different mobility and collision cross section (CCSs) were observed, indicating different molecular conformations. Formation of analyte dimers was also observed, which could be associated with molecular geometry of the compounds. By optimizing the range and speed of the electric field gradient and ramp, respectively, the separation of THC and CBD was achieved by employing the adduct formation. This study demonstrates that the favorable resolution of TIMS combined with the ability to detect weakly bound counter ions is a valuable means for rapid detection, separation and structural assignment of molecular isomers and analyte conformations.

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Section: Separation Of Isomers Employing Cation Adduct Formationmentioning

confidence: 88%

Adduct-ion formation in trapped ion mobility spectrometry as a potential tool for studying molecular structures and conformations

Zietek

Mengerink

Jordens

et al. 2017

Int. J. Ion Mobil. Spec.

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“…The trends in the binding of alkali metal cations to TMP are examined and allow determination of the influence of the size of the metal cation on the nature and strength of binding. The binding of alkali metal cations to TMP is also compared with that of acetone [26,30] and methanol [27][28][29][30][31][32].…”

Section: ϩmentioning

confidence: 99%

“…The ground state conformer involves bidentate binding of M ϩ to the oxo and one of the alkoxy oxygen atoms, i.e., the C3 conformer. To dissect the relative contributions of these two interactions to the binding, the M ϩ (TMP) complexes are compared with the analogous M ϩ (acetone) [26,Å30]ÅandÅM ϩ (methanol)ÅcomplexesÅ [27][28][29][30][31][32].ÅThe M M ϩ (methanol) complexes. Thus, the bidentate interaction with the alkoxy oxygen atom produces a change in the binding geometry and strength of interaction with both the oxo and alkoxy oxygen atoms that weakens these interactions relative to individual monodentate interactions, but must clearly result in overall stronger binding or such binding geometries would not correspond to the ground state conformers.…”

Section: Comparison Of Alkali Metal Cation Binding To Methanol and Acmentioning

confidence: 99%

A simple model for metal cation-phosphate interactions in nucleic acids in the gas phase: Alkali metal cations and trimethyl phosphate

Ruan

Huang

Rodgers

2008

J. Am. Soc. Mass Spectrom.

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Threshold collision-induced dissociation techniques are employed to determine the bond dissociation energies (BDEs) of complexes of alkali metal cations to trimethyl phosphate, TMP. Endothermic loss of the intact TMP ligand is the only dissociation pathway observed for all complexes. Theoretical calculations at the B3LYP/6-31G* level of theory are used to determine the structures, vibrational frequencies, and rotational constants of neutral TMP and the M ϩ (TMP) complexes. Theoretical BDEs are determined from single point energy calculations at the B3LYP/6-311ϩG(2d,2p) level using the B3LYP/6-31G* optimized geometries. The agreement between theory and experiment is reasonably good for all complexes except Li ϩ (TMP hosphate esters are integral parts of many biologically active molecules ranging from nucleic acids, lipids, and ATP to pesticides and nerve agents [1][2][3]. Serving as link components in nucleic acids, phosphate esters connect thousands of base pairs to form large molecules that contain the genetic information. These phosphate groups are deprotonated under physiological conditions. The resulting negative charges along the phosphate backbone are stabilized and neutralized by the binding of metal cations. Metal cations can and often do exert a significant influence on nucleic acid structure and genetic information transfer [4]. Metal cation binding reduces the repulsion between neighboring nucleotide units, and therefore influences the stabilization and structural dynamics of nucleic acids and lipids in membranes. For example, alkali and alkaline earth metal cations, including the most biologically important of these cations, Na ϩ and Mg 2ϩ , prefer to bind to a phosphate group rather than to the nucleobases or sugar moieties [5]. Mg 2ϩ is found to increase the melting temperature of DNA [6]. Metal cations may also be involved in the functioning of nucleic acids, e.g., metal cations are required for the proper functioning of all ribozymes [7]. Metal cation-nucleic acid interactions are currently of great interest because metal cations and metal cation-ligand complexes bind to DNA and regulate gene expression, act as drugs, or can be used as tools for molecular biology studies [8]. Hendry and Sargeson studied metal cation-promoted phosphate ester hydrolysis and found that the rate of hydrolysis is modulated by the size of the metal cation and the ease of formation of a four-membered chelate ring [9]. Dempcy and Bruice found a pentacoordinate intermediate for the catalysis of alkyl phosphate diesters [10]. Schneider and Kabelac et al. [11] studied the distribution of five metal cations (i.e., Na, and Zn 2ϩ ) and water around a negatively charged phosphate group from various crystal structures, and found that all of the cations prefer asymmetric monodentate coordination over bidentate coordination. Their ab initio calculations suggest that bidentate binding of these metal cations to an isolated phosphate group is preferred, but that the presence of even a single water molecule alters this preference. Ab...

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“…The pK a of ketoprofen is 4 The fact that the adduct ion enhancement is pronounced for ketoprofen in the presence of some additives suggests that Na + may complex species by coordinating with the unshared electrons on the carbonyl group. Sodium has been shown to coordinate between two carbonyl groups in a single compound, such as succinamide and glycylglycine [9], as well as to favorably bind two acetone molecules in a dimer-sodium complex [16]. The pseudo-molecular ion may also be formed through dimer ion-pair interactions, where the Na + cation is bound by two negatively charged ketoprofen molecules.…”

Section: Ketoprofenmentioning

confidence: 99%

Adduct formation in electrospray ionization. Part 1: Common acidic pharmaceuticals

Schug

McNair

2002

J. Sep. Science

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This study focuses on pseudo-molecular ion formation in electrospray ionization mass spectrometry (ESI-MS) of six anti-inflammatory pharmaceuticals with similar functionality. The formation of particular pseudo-molecular ions depends on ion affinity and molecular structure of the analyte as well as the solvent/buffer conditions used. Six common anti-inflammatory agents are mixed 1:1 with six different acetonitrile/aqueous buffer solutions at varying concentrations. The analytes are ibuprofen, carprofen, naproxen, ketoprofen, flurbiprofen, and fenoprofen. The pK a and surface activity of the analytes and the pH, concentration, and type of the solvent system strongly affect the ions formed [1,2]. The additives are common liquid chromatography (LC) mobile phase modifiers.The spectral intensities of three major pseudo-molecular ions were measured by flow injection analysis ESI-MS. The ions studied correspond to the deprotonated molecular ion ([M -H] -), a deprotonated dimer ion ([2M -H] -), and a deprotonated dimer ion pair with sodium ([2M -2H+Na] -). These ions were chosen due to their high relative abundance in a majority of the spectra.The pK a of the analytes studied range from 4.1 to 4.4, due to their aromatic acetic acid moiety. The common carboxylic acid group facilitates ESI of the compounds in the negative ionization mode. The changes in molecular structure of these model compounds allows for a wide variety of solution interactions. Some analytes are effectively declustered under the set conditions creating an intense [M -H] -peak, whereas others prefer to form dimers or complexes with sodium.

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Thermochemical properties of ion complexes Na+(M)n in the gas phase

Cited by 118 publications

References 4 publications

Adduct-ion formation in trapped ion mobility spectrometry as a potential tool for studying molecular structures and conformations

Adduct-ion formation in trapped ion mobility spectrometry as a potential tool for studying molecular structures and conformations

A simple model for metal cation-phosphate interactions in nucleic acids in the gas phase: Alkali metal cations and trimethyl phosphate

Adduct formation in electrospray ionization. Part 1: Common acidic pharmaceuticals

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