Absolute Potassium Cation Affinities (PCAs) in the Gas Phase

Lau, Justin Kai-Chi; Wong, Carrie Hoi Shan; Ng, Po Shan; Siu, Fung Ming; Ling, Ngai; Tsang, Chun Wai

doi:10.1002/chem.200204678

Cited by 44 publications

(29 citation statements)

References 81 publications

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“…As can be seen in Table 1 Figure 4. The K ϩ affinity values calculated by Tsang and coworkers [13] were used for this figure. Because in this work no value exists for the binding affinity of K ϩ (Met), we take the experimental value of 33.9 Ϯ 2.6 kcal/mol from reference [41] determined by Armentrout and coworkers.…”

Section: Solvation Effect and Water Binding Energiesmentioning

confidence: 99%

“…Because in this work no value exists for the binding affinity of K ϩ (Met), we take the experimental value of 33.9 Ϯ 2.6 kcal/mol from reference [41] determined by Armentrout and coworkers. The K ϩ scale was anchored by K ϩ (Gly), taking the value reported by Armentrout et al [16], 29.4 kcal/mol, and 28.3 kcal/mol [13] as the reference value. This adjustment to the K ϩ scale of reference [13] leads to the value of 32.8 kcal/mol for K ϩ (Met), which was used for Figure 4.…”

Section: Solvation Effect and Water Binding Energiesmentioning

confidence: 99%

“…The K ϩ scale was anchored by K ϩ (Gly), taking the value reported by Armentrout et al [16], 29.4 kcal/mol, and 28.3 kcal/mol [13] as the reference value. This adjustment to the K ϩ scale of reference [13] leads to the value of 32.8 kcal/mol for K ϩ (Met), which was used for Figure 4. As can be seen in this figure, a linear Figure 4, can be explained as being a consequence of direct interaction of the first water molecule with the K ϩ ion of AAK ϩ (H 2 O) and the electrostatic nature of the AAK ϩ Ϫ H 2 O binding.…”

Section: Solvation Effect and Water Binding Energiesmentioning

confidence: 99%

“…The effect of the side chain illustrated here by a decrease in the water binding energies in AAK ϩ (H 2 O) n ϭ 1,2 and previously [39] for AANa ϩ (H 2 O) n ϭ 1,2 with increasing K ϩ and Na ϩ affinities to AA, respectively, is in line with observations [4,14,18] that the binding of K ϩ and Na ϩ to amino acids is dominated by the interaction with the amino acid backbone and enhanced by interaction with the sidechain substituent. The binding enhancement effect of the phenyl substituent is manifested by the difference in the K ϩ binding energies to Ala (29.6 kcal/mol [13] and Phe (34.8 kcal/mol [13], while the electron withdrawing effect is demonstrated by the observed difference between the hydration energies for AlaK ϩ and PheK ϩ , Table 1. Although this method of estimating influence is not fully satisfactory because the aliphatic portion is expected to contribute to the Ala Ϫ K ϩ binding as well, the comparison shows the magnitude of the aromatic side-chain substituent effects on the enhancement in the AA Ϫ K ϩ binding (ϳ17%) and weakening (ϳ11%) of the AAK ϩ -H 2 O interaction.…”

Section: Solvation Effect and Water Binding Energiesmentioning

confidence: 99%

“…They play an important role in several biochemical functions such as enzyme regulation, transfer of metal ions from intracellular to extracellular environments, electrical excitability of nerves, stabilization of DNA structures and so on [1]. Therefore, the interaction between alkali metal cations and various amino acids (AAs) has attracted considerable attention, and many experimental and theoretical studies have been conducted [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. These studies show that K ϩ binds to AAs quite differently than Na ϩ .…”

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Hydration of potassiated amino acids in the gas phase

Wincel

2007

J. Am. Soc. Mass Spectrom.

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The thermochemistry of stepwise hydration of several potassiated amino acids was studied by measuring the gas-phase equilibria, AAK ϩ (H 2 O) nϪ1 ϩ H 2 O ϭ AAK ϩ (H 2 O) n (AA ϭ Gly, AL, Val, Met, Pro, and Phe), using a high-pressure mass spectrometer. The AAK ϩ ions were obtained by electrospray and the equilibrium constants K nϪ1,n were measured in a pulsed reaction chamber at 10 mbar bath gas, N 2 , containing a known partial pressure of water vapor. Determination of the equilibrium constants at different temperatures was used to obtain the ϩ and Na ϩ ions are the most abundant metal cations in living systems. They play an important role in several biochemical functions such as enzyme regulation, transfer of metal ions from intracellular to extracellular environments, electrical excitability of nerves, stabilization of DNA structures and so on [1]. Therefore, the interaction between alkali metal cations and various amino acids (AAs) has attracted considerable attention, and many experimental and theoretical studies have been conducted [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. These studies show that K ϩ binds to AAs quite differently than Na ϩ . For example, in the case of aliphatic AAs such as glycine (Gly), alanine (Ala), and valine (Val), the Na ϩ ion is coordinated to nitrogen and carbonyl oxygen (NO coordination) in the lowest energy conformers, while K ϩ prefers to bind to the carbonyl and hydroxyl oxygen atoms of the charge-solvated form (OO coordination) [6,8,10,16]. In proline (Pro), phenylalanine (Phe), and cysteine (Cys), the modes of K ϩ binding are similar to those of the corresponding Na ϩ complexes [3-5, 12, 20].Molecular dynamics simulations of a bacterial potassium ion channel reveal a significant selectivity filter for K ϩ compared with Na ϩ ions [21,22]. The different hydration state of Na ϩ and K ϩ in the channel inner pore is postulated to be a basic factor determining ionic selectivity [23,24]. Investigations into the relative energetics of noncovalent interactions between single amino acids, metal ions and water molecules could provide important information to explain ion channel function at a molecular level. Despite the considerable amount of experimental and theoretical studies that have been conducted on the binding of Na ϩ and K ϩ to amino acids, little data are available on the interactions of water molecules with metal ion/amino acid complexes. Because metal ions and biomolecules are normally surrounded by water in living systems, these interactions are of significant importance in understanding biological systems. Williams and coworkers [8,[25][26][27][28][29][30][31] studied the modes of metal ion and water binding in hydrated complexes of alkali metal cationized valine, glutamine, lysine, and ␣-methyl-proline using both black-␣ ␣ body infrared radiative dissociation (BIRD) experiments and theory. Armentrout et al. investigated the sequential bond energies of water to sodiated glycine [32] and proline [33] by threshold collision-induced dissociation ...

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Section: Solvation Effect and Water Binding Energiesmentioning

confidence: 99%

Section: Solvation Effect and Water Binding Energiesmentioning

confidence: 99%

Section: Solvation Effect and Water Binding Energiesmentioning

confidence: 99%

Section: Solvation Effect and Water Binding Energiesmentioning

confidence: 99%

mentioning

confidence: 99%

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Hydration of potassiated amino acids in the gas phase

Wincel

2007

J. Am. Soc. Mass Spectrom.

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Cationic Transition Metal Arene Interactions

Diefenbach

Schwarz

1998

Encyclopedia of Computational Chemistry

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Describing selected examples, this contribution aims at discussing structural, electronic, and thermochemical aspects of cationic transition metal–arene complexes in gas‐phase chemistry. The main focus is cast on the application of quantum chemistry to metal–benzene complexes and derivatives and on a comparison to experiment where appropriate. The reader is taken through an overview starting from general electronic and molecular orbital considerations and leading to structural and thermochemical implications thereof. A short section on transition metal–arene reactivity and a final paragraph on miscellaneous related systems conclude the article.

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Gas‐Phase Cation Affinity and Basicity Scales

Laurence

Gal

2009

Lewis Basicity and Affinity Scales

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The study of the formation of complexes between cations and chemical species in the gas phase offers the unique possibility of measuring the intrinsic (i.e. free of solvent and counter ion influences) Lewis basicity of these species. Although the charge-transfer component of the interaction energy in cation adducts is normally smaller than the electrostatic and polarization components, gas-phase cations are generally considered as archetypal Lewis acids because the full positive charge of the naked cation allows strong binding with classical Lewis bases. In fact, almost any entity bearing some electron density, such as the rare gases, can form complexes with cations that may be observable in the gas phase.There is a large array of cations that have been studied in the gas phase for their interaction with Lewis bases (generally neutral organic molecules) and are still being actively investigated today. The most studied is the proton [1-6]. This special cation will not be dealt with in this chapter (however, see Section 1.3 in Chapter 1), since the proton and its transfer serve to define the Brönsted acids and bases, as opposed to Lewis acids and bases, which do not exchange protons. Moreover, although the proton and a cation with an empty orbital may be seen as identical from the point of view of the Lewis theory, the special 'electronic structure' of the proton (in fact the absence of any electron) makes the proton affinity and basicity scales completely different, qualitatively and quantitatively, from any other cation scales. A significant part of the studies of the interaction of gas-phase metal cations with organic molecules was devoted to their chemical reactivity: bond insertion, bond cleavage, elimination and so on. This aspect is not considered here, although some of these reactions may be used as indirect routes for the formation of cation/molecule adducts.Apart from the proton, experimental studies have focused primarily on the binding of alkali metal cations and transition metal monocations. Few studies have considered alkaline Lewis Basicity and Affinity Scales: Data and Measurement

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Absolute Potassium Cation Affinities (PCAs) in the Gas Phase

Cited by 44 publications

References 81 publications

Hydration of potassiated amino acids in the gas phase

Hydration of potassiated amino acids in the gas phase

Cationic Transition Metal Arene Interactions

Gas‐Phase Cation Affinity and Basicity Scales

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