Interaction of Li+, Na+, and K+ with the Proline Amino Acid. Complexation Modes, Potential Energy Profiles, and Metal Ion Affinities

Marino, Tiziana; Russo, Nino; Toscano, Marirosa

doi:10.1021/jp027063j

Cited by 104 publications

(116 citation statements)

References 73 publications

(130 reference statements)

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“…[1][2][3][4][5][6][7][8][9][10][11] Gas-phase study of complexes involving much larger peptide substrates has become experimentally accessible with the emergence of electrospray ionization, and also computationally accessible with advancing computational tools.…”

Section: Introductionmentioning

confidence: 99%

Alkali Metal Complexes of the Dipeptides PheAla and AlaPhe: IRMPD Spectroscopy

2008

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Complexes of PheAla and AlaPhe with alkali metal ions Na + and K + were generated by electrospray ionization, isolated in the Fourier-transform ion cyclotron resonance (FT-ICR) ion trapping mass spectrometer, and investigated spectroscopically by infrared multiple-photon dissociation (IRMPD) using light from the FELIX free electron laser over the mid-infrared range from 500 to 1900 cm -1 . Conclusions about structural features of the complexes were drawn by comparison with predicted spectra and relative free energies calculated by DFT for a number of candidate conformers.Combining spectroscopic and energetic results, it is established that the metal ion is always chelated by the amide carbonyl oxygen, and that the C-terminal hydroxyl does not complex the metal ion and is in the endo conformation. It is also likely that the aromatic ring of Phe always chelates the metal ion in a cation-π binding configuration. Along with the amide CO and ring chelation sites, a third Lewis-basic group almost certainly chelates the metal ion, giving a threefold chelation geometry. This third site may be either the Cterminal carbonyl oxygen, or the N-terminal amino nitrogen. From the spectroscopic and computational evidence, a slight preference was given to the carbonyl group, in an RO a O t chelation pattern, but the amino group is almost equally likely (particularly for 2

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Section: Introductionmentioning

confidence: 99%

Alkali Metal Complexes of the Dipeptides PheAla and AlaPhe: IRMPD Spectroscopy

2008

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“…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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confidence: 99%

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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“…Protonated octamers of serine are unusually stable in the gas phase [39 -41] and a structure in which all the serine molecules are zwitterionic has been proposed [39,40]. For proline, attachment of an alkali metal or Ag ϩ cation can make the zwitterion or salt-bridge form more stable than the nonzwitterion or charge-solvated form by 2-7 kcal/mol [30,42,43], but for Cu ϩ , the chargesolvated form is 3.4 kcal/mol more stable [32,44]. The higher propensity for arginine and proline to form zwitterion or salt-bridge structures is due in part to the higher gas-phase proton affinity of the proton acceptor and the poor charge-solvating ability in the case of proline.…”

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confidence: 99%

Binding energies of water to lithiated valine: Formation of solution-phase structure in vacuo

Lemoff

Williams

2004

J. Am. Soc. Mass Spectrom.

100

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Dissociation kinetics for loss of a water molecule from hydrated ions of lithiated valine, alanine ethyl ester and betaine are determined using blackbody infrared radiative dissociation at temperatures between Ϫ60 and 110°C. From master equation modeling of these data, values of the threshold dissociation energy are obtained for clusters containing one through three water molecules. By comparing the values for valine with its two isomers, one a model for the nonzwitterion structure, the other a model for the zwitterion structure, information about the structure of valine in these hydrated clusters is inferred. Structures, relative energies, and water binding energies for these ions are also calculated at the B3LYP/6-31ϩϩG** level of theory. With one water molecule, both experiment and theory indicate that valine is not a zwitterion and that the lithium ion coordinates with the amino nitrogen and the carbonyl oxygen (NO coordinated) and the water molecule interacts directly with the lithium ion. With two water molecules, the zwitterion and nonzwitterion structures are nearly isoenergetic, but the experiment clearly indicates a NO-coordinated nonzwitterion structure. With three water molecules, both the experimental data and theory indicate that the lithium ion binds to the carboxylate group of valine, i.e., valine is zwitterionic with three water molecules. The agreement between the experimentally determined and calculated binding energies is good for all the clusters, with deviations of Յ 0.12 eV. M olecular structure in solution depends on both the intrinsic properties of the molecule and on the effects of the surrounding solvent molecules. Exclusion of water from the interior of proteins influences protein folding and conformation. Similarly, lipid bilayer formation is due to differences in water interaction with the polar and hydrophobic ends of the lipid molecules. Gas-phase experiments make possible investigation of the intrinsic properties of the molecule. Differences between gas-phase and solution-phase structure can be attributed to solvent effects. Studies of gas-phase peptides indicate that ␣-helices can be stable in the absence of water and indicate that the propensity for helix formation for some amino acids differs in the gas phase and in solution [1,2]. For example, peptides with high valine content have a higher helix-forming propensity than their alanine analogues in the gas phase, but just the opposite is observed in aqueous solution [1].In the condensed phase, specific water molecules can play an important role in molecular structure. Such specific water molecules are often observed in crystal structures of proteins and other molecules. Evidence for specific water has been reported by Jarrold and coworkers for the molecule BPTI which tightly binds one water molecule in the gas phase [3,4]. Magic hydration numbers for gramicidin S at 8, 11, and 14 water molecules suggest stable solvation shells around the doubly protonated gas-phase ion [5], while a magic hydration number of 40 water molecules h...

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Interaction of Li⁺, Na⁺, and K⁺ with the Proline Amino Acid. Complexation Modes, Potential Energy Profiles, and Metal Ion Affinities

Cited by 104 publications

References 73 publications

Alkali Metal Complexes of the Dipeptides PheAla and AlaPhe: IRMPD Spectroscopy

Alkali Metal Complexes of the Dipeptides PheAla and AlaPhe: IRMPD Spectroscopy

Hydration of potassiated amino acids in the gas phase

Binding energies of water to lithiated valine: Formation of solution-phase structure in vacuo

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