Vibrational Signature of Charge Solvation vs Salt Bridge Isomers of Sodiated Amino Acids in the Gas Phase

Kapota, Catherine; Lemaire, Joël; Maı̂tre, Philippe; Ohanessian, Gilles

doi:10.1021/ja036932v

Cited by 265 publications

(349 citation statements)

References 51 publications

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“…The band for the C=O stretch mode of a neutral carboxylic acid should occur for a free acid around 1780 cm -1 34 and shifts to 1710 cm -1 when strongly hydrogen bonded to another acid 35 or 1727 cm -1 when coordinated to a Na + ion. 36 For a deprotonated carboxylic acid (carboxylate), on the other hand, the strong band for the anti-symmetric stretching mode is found at 1620-1640 cm -1 and the weaker band for the symmetric stretching mode is typically located at 1300-1400 cm -1 . 37,38 In the IR spectra of all serine clusters investigated here (see Fig.…”

Section: An Interesting Question Is Howmentioning

confidence: 99%

Infrared spectrum and structure of the homochiral serine octamer–dichloride complex

et al. 2017

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The amino acid serine is known to form a very stable octamer which has properties that sets it apart from serine complexes having different sizes or from complexes composed of other amino acids. For example, both singly protonated serine octamers and anionic octamers complexed with two halogen ions, strongly prefer homochirality even when assembled from racemic D, L mixtures.Consequently, the structures of these complexes are of great interest but no acceptable candidates have so far been identified. Here we investigate anionic serine octamers coordinated with two chloride ions using a novel ion mobility/infrared spectroscopy technique in combination with theoretical calculations. The results allow the identification of a unique structure for (Ser 8 Cl 2 ) 2-that is highly symmetric, very stable, homochiral and whose calculated properties match those observed in the experiments. 3Clusters of atoms or molecules with unusually high relative intensities in mass spectra are termed "magic". In many instances, those "magic" clusters could be assigned to specific structures, often of high symmetry. Examples are numerous and include rare gas clusters 1 , fullerenes, most notably C 60 , 2 Ti 8 C 12 "metallocarbohedrane", 3 metal clusters such as Au 20 , 4,5 and highly symmetric protonated water clusters. 6,7 In the case of C 60 , the initial observation of magic numbers in mass spectra eventually led to the discovery of a new group of materials and a new form of carbon.Occasionally a "magic" cluster resists structural characterization. A famous example is the serine octamer. After electrospray of solutions containing serine, it was first observed that a cluster with the composition (Ser 8 H) + dominated the mass spectrum. 8 This is in contrast to mass spectra of other amino acid clusters, for which the intensity patterns of peaks in their mass spectra show much smoother evolution. The experimental observations have spurred calculations, and several candidates for structures of cationic serine octamers have been proposed. 8,17,[19][20][21] However, for most of them, the proposed structures do not provide an obvious reason for the observed homochirality. In addition, while the calculations indicate that the proposed structures are stable, they are not dramatically more stable compared to serine clusters of different sizes. Thus, there is no general consensus of the structure of serine octamer clusters and the quest for finding a structure that is compatible with the experimental observations is still ongoing. 4In contrast to the abundance of studies on the cationic serine octamer, little attention has so far been given to the anionic species. Here, we present results from a study on serine cluster anions, in which we couple ion mobility-mass spectrometry (IMS-MS) with infrared (IR) spectroscopy.IMS-MS gives the absolute, angle averaged collision cross section (CCS) of specific clusters and this value can be used to determine the overall size of the cluster and to judge if particular calculated structures are compa...

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Section: An Interesting Question Is Howmentioning

confidence: 99%

Infrared spectrum and structure of the homochiral serine octamer–dichloride complex

et al. 2017

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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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“…Upon further protonation, more COOH moieties are formed, thus explaining the linear increase in intensity of this band with increasing charge state. Another conceivable assignment for the 1483 cm À1 mode may be the umbrella mode of the NH 3 1 moiety, whose absorption is known to be quite intense in the gas phase, 17 and for which gas phase 17 and matrix isolation studies 31 show a band position in close proximity with the 1483 cm À1 band. Cytochrome c contains 18 lysine residues that form NH 3 1 moieties upon protonation.…”

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confidence: 99%

Charge-state resolved mid-infrared spectroscopy of a gas-phase protein

Oomens

Polfer

Moore

et al. 2005

Phys. Chem. Chem. Phys.

160

147

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Infrared spectra of a 104 amino-acid protein in the gas phase as a function of its charge state are presented. The spectra contain clearly resolvable bands in the amide I and II spectral regions, as well as a band at 1483 cm–1, which is not observed in solution phase spectroscopy and is especially prominent for the higher charge states. Compared to solution, the amide I band is blue-shifted and the amide II band red-shifted, as expected for species in an environment with reduced hydrogen bonding. The band positions are suggestive of a mostly -helical structure of the protein and their widths are comparable to those in solution, suggesting a similar conformational distribution

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Vibrational Signature of Charge Solvation vs Salt Bridge Isomers of Sodiated Amino Acids in the Gas Phase

Cited by 265 publications

References 51 publications

Infrared spectrum and structure of the homochiral serine octamer–dichloride complex

Infrared spectrum and structure of the homochiral serine octamer–dichloride complex

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

Charge-state resolved mid-infrared spectroscopy of a gas-phase protein

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