Evidence for the Formation of Gas-Phase Inclusion Complexes with Cyclodextrins and Amino Acids

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Protonated complexes of amino acids and underivatized ␤-cyclodextrin, produced by electrospray ionization and trapped in the Fourier transform mass spectrometer, undergo formation of ternary complexes when reacted with alkyl amine. Based on the reactivities of the protonated amino acid complexes with alkylamines, the reactivities of the corresponding amino acid esters, and partially derivatized ␤-cyclodextrin hosts, we conclude that the ternary complexes are salt-bridge zwitterionic species composed of amino acid zwitterions and protonated alkylamine all interacting with the hydroxyl groups on the narrow rim of the cyclodextrin. Molecular modeling calculations and experimental results suggest that the interactions of the amino acids with the rims contribute greatly to the formation of the zwitterionic species. (J Am Soc Mass Spectrom 2005, 16, 166 -175)

supporting

confidence: 58%

Zwitterion formation in gas-phase cyclodextrin complexes

Ahn

Cong

Lebrilla

et al. 2005

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“…It has been reported previously that the rates of reaction for the gas-phase exchange in derivatized ␤ -CD differ among enantiomers [15,16,18,19]. Furthermore, molecular modeling calculations with L-and D-enantiomers illustrate that the interactions between the amino acid guest and the derivatized ␤-CD host produce distinct complex structures [16,18,19].…”

Section: Reactions Of Amino Acids and Their Enantiomersmentioning

confidence: 85%

“…Gas-phase complexes of tri-O-methyl ␤-cyclodextrin (␤-CD*) and di-O-methyl ␤-cyclodextrin (␤-CD°) with protonated amino acids (AA) undergo exchange reactions with amines in the gas-phase [15,16]. For example, the protonated ␤-CD* -amino acid complex, [␤-CD*:AA ϩ H] ϩ , reacts with an alkyl amine to produce the protonated ␤-CD*-alkylamine complex and a neutral amino acid, which is released from the ␤-CD* cavity after proton transfer (Scheme 1).…”

mentioning

confidence: 99%

Structural relationships in small molecule interactions governing gas-phase enantioselectivity and zwitterionic formation

Cong

Czerwieniec

McJimpsey

et al. 2006

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Gas-phase zwitterionic amino acids were formed in complexes of underivatized ␤-cyclodextrin through reactions with a neutral base, n-propylamine. The reaction was performed in the analyzer cell of an electrospray ionization-Fourier transform mass spectrometer. Most of the natural amino acids were studied with three cyclodextrin hosts including ␣-, ␤-, and ␥-cyclodextrin to understand better the structural features that lead to the stabilization of the zwitterionic complexes. Molecular dynamics calculations were performed to provide insight into the structural features of the complexes. The rate constants of the reactions were obtained through kinetic plots. Examination of both L-and D-enantiomers of the amino acid showed that the reaction was enantioselective. The reaction was then employed to analyze mixtures of Glu enantiomers naturally occurring in the bacteria Bacillus licheniformis. (J Am Soc Mass Spectrom 2006, 17, 442-452)

“…The molecule was constructed and pre-minimized in the consistent valence force field (CVFF) implemented in the Insight II program as previously described [60]. Temperature annealing was done by heating the molecule to 600 K for 200 ps.…”

Section: Molecular Modelingmentioning

confidence: 99%

Evidence for long-range glycosyl transfer reactions in the gas phase

Franz

Lebrilla

2002

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A long-range glycosyl transfer reaction was observed in the collision-induced dissociation Fourier transform (CID FT) mass spectra of benzylamine-labeled and 9-aminofluorene-labeled lacto-N-fucopentaose I (LNFP I) and lacto-N-difucohexaose I (LNDFH I). The transfer reaction was observed for the protonated molecules but not for the sodiated molecules. The long-range glycosyl transfer reaction involved preferentially one of the two L-fucose units in labeled LNDFH I. CID experiments with labeled LNFP I and labeled LNFP II determined the fucose with the greatest propensity for migration. Further experiments were performed to determine the final destination of the migrating fucose. , and post-translational protein modification [6 -8]. Whereas the insight into the physical process of carbohydrate recognition is in its infancy, considerable progress has been made towards the quantitation and structural elucidation of biologically active oligosaccharides. NMR [9] yields structural information about oligosaccharides. Frequently, however, an inherent problem is the limited amount of sample causing NMR experiments to become time-consuming or impossible. The sensitivity and accuracy of mass spectrometry has made this technique the best choice for analysis of oligosaccharides [10,11]. Structural information can be derived from collision-induced dissociation (CID) [12][13][14][15][16][17][18][19][20] or from post-source decay (PSD) time-of-flight (TOF) experiments [21][22][23][24][25][26]. Fragmentation of glycosidic bonds provides information about the monosaccharide sequence and computer algorithms can extract sequence information from web-based catalogs of MS n spectra [27]. However, the assignment of anomeric configuration [28 -35] and linkage [18, 36 -38] within the oligosaccharide structure is not a trivial task. Glycosidase digestion [13, 39 -47] in conjunction with mass spectrometric analysis can be used to assign linkage and stereochemistry. In an alternative approach, CID-fragmentation patterns have been linked to structural motifs in the oligosaccharide (catalog library approach) [12].We recently reported on the use of more nucleophilic benzylogous amines, such as benzylamine and 9-aminofluorene, for the labeling of oligosaccharides and the experimental results of FT-MS experiments with the labeled oligosaccharides [48]. Detection of 5 pmol of 9-amino fluorene-labeled oligosaccharide was achieved with a photo diode array during HPLC separation. The label combines low cost with good nucleophilicity and ease of introduction. The behavior of oligosaccharides derivatized with benzylogous amines such as benzylamine in CID experiments has not been reported, although data obtained from PSD matrix-assisted laser desorption/ionization (MALDI)-TOF experiments have been published [25,49].In this paper, we discuss a long-range glycosyl transfer that occurs during CID for benzylamine-and 9-AmFL-labeled oligosaccharides. The transfer of a fucose across three monosaccharide units was observed only in protonated molecules. To t...