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![Product ion spectra (i.e., MS² fragmentations) of (a)-(b) [C16Glu-H]ˉ (m/z 384 with R1 = CH3(CH2)13-) at ELab = 17 eV and ELab = 30 eV, and (c)-(d) [C16GluMe-H]ˉ (m/z 398) at ELab = 17 eV and ELab = 30 eV, respectively (accurate m/z values and corresponding elemental composition reported in Table S1)](publication/358112924/figure/fig1/AS:1129735631441932@1646361372683/Product-ion-spectra-ie-MS-fragmentations-of-a-b-C16Glu-H-m-z-384-with.png)
Product ion spectra (i.e., MS² fragmentations) of (a)-(b) [C16Glu-H]ˉ (m/z 384 with R1 = CH3(CH2)13-) at ELab = 17 eV and ELab = 30 eV, and (c)-(d) [C16GluMe-H]ˉ (m/z 398) at ELab = 17 eV and ELab = 30 eV, respectively (accurate m/z values and corresponding elemental composition reported in Table S1)
Source publication
![Product ion spectra (i.e., MS² fragmentations) of (a)-(b) [C16Glu-H]ˉ...](publication/358112924/figure/fig1/AS:1129735631441932@1646361372683/Product-ion-spectra-ie-MS-fragmentations-of-a-b-C16Glu-H-m-z-384-with_Q320.jpg)
The identification of bacterial metabolites produced by the microbiota is a key point to understand its role in human health. Among them, lipo-amino acids (LpAA), which are able to cross the epithelial barrier and to act on the host, are poorly identified. Structural elucidation of few of them was performed by high-resolution tandem mass spectromet...
Citations
... 14 We then determined lipoamino acid (LpAA) and GABA-lipopeptide structures by high-resolution mass spectrometry and developed a quantitative method of newly identified LpAA and lipopeptide-GABA by liquid chromatography coupled to mass spectrometry (LC-MS/MS) in different strains of bacteria. 15 16 We hypothesised that visceral hypersensitivity in adulthood may originate from functional intestinal microbiota dysbiosis induced by stress in pregnancy. Based on our previous studies demonstrating the ability of lipids to regulate sensory neuron activation, 14 17 18 we assumed that bacteria-derived GABA-lipopeptides may be the link between functional dysbiosis and IBS symptoms. ...
... PS induces visceral hypersensitivity in the adult offspring. VMR to colorectal distensions in control (white) or PS (black) mice in response to increasing pressures of distension(15,30,45 and 60 mm Hg) was measured in both male (A) and female (B) offspring. Data are expressed as mean±SEM (n=14-19 mice/group, three independent experiments). ...
... significantly different from the corresponding control group. (C) VMR to colorectal distensions in response to increasing pressures of distension(15,30,45 and 60 mm Hg) was measured in both M and FM PS offspring. Measurements were done before (white) and after intracolonic administrations of C14AsnGABA (black). ...
Objectives:
Clinical studies revealed that early-life adverse events contribute to the development of IBS in adulthood. The aim of our study was to investigate the relationship between prenatal stress (PS), gut microbiota and visceral hypersensitivity with a focus on bacterial lipopeptides containing γ-aminobutyric acid (GABA).
Design:
We developed a model of PS in mice and evaluated, in adult offspring, visceral hypersensitivity to colorectal distension (CRD), colon inflammation, barrier function and gut microbiota taxonomy. We quantified the production of lipopeptides containing GABA by mass spectrometry in a specific strain of bacteria decreased in PS, in PS mouse colons, and in faeces of patients with IBS and healthy volunteers (HVs). Finally, we assessed their effect on PS-induced visceral hypersensitivity.
Results:
Prenatally stressed mice of both sexes presented visceral hypersensitivity, no overt colon inflammation or barrier dysfunction but a gut microbiota dysbiosis. The dysbiosis was distinguished by a decreased abundance of Ligilactobacillus murinus, in both sexes, inversely correlated with visceral hypersensitivity to CRD in mice. An isolate from this bacterial species produced several lipopeptides containing GABA including C14AsnGABA. Interestingly, intracolonic treatment with C14AsnGABA decreased the visceral sensitivity of PS mice to CRD. The concentration of C16LeuGABA, a lipopeptide which inhibited sensory neurons activation, was decreased in faeces of patients with IBS compared with HVs.
Conclusion:
PS impacts the gut microbiota composition and metabolic function in adulthood. The reduced capacity of the gut microbiota to produce GABA lipopeptides could be one of the mechanisms linking PS and visceral hypersensitivity in adulthood.
A preparation of tert-butyl esters of amino acid is described that proceeds from protected amino acids and tert-butanol using anhydrous magnesium sulfate and an excess of boron trifluoride diethyl etherate as additional reagents. The method affords tert-butyl esters in good yields and a variety of amino acid side chains and substituents tolerate the reaction conditions.
Identification of lipopeptides (LpAA) synthesized from bacteria involves the study of structural characterization. Twenty LpAA have been characterized using commercial tandem high-resolution mass spectrometers in negative electrospray, employing nonresonant excitation in "RF only" collision cells and generally behave identically. However, [LpAA-H]- (AA = Asp or Glu) shows surprising fragmentation pathways, yielding a complementary fatty acid carboxylate and dehydrated amino acid fragment anions. In this study, the dissociation mechanisms of [C12Glu-H]- were determinate using energy-resolved mass spectrometry (ERMS). Product ion breakdown profiles are, generally, unimodal with full width at half-maximum (fwhm) increasing as product ion m/z ratios decrease, except for the two product ions of interest (fatty acid carboxylate and dehydrated glutamate) characterized by broad and composite profiles. Such behavior was already shown for other ions using a custom-built guided ion beam mass spectrometer. In this study, we investigate the meaning of these particular profiles from an ERMS breakdown, using fragmentation mechanisms depending on the collision energy. ERMS on line with ion mobility spectrometry (IMS), here called ER-IMS, provides a way to probe such questions. Broad or composite profiles imply that the corresponding product ions may be generated by two (or more) pathways, resulting in common or isomeric product ion structures. ER-IMS analysis indicates that the fatty acid carboxylate product ion is produced with a common structure through different pathways, while dehydrated glutamate has two isomeric forms depending on the mechanism involved. Drift time values correlate with the calculated collision cross section that confirms the product ion structures and fragmentation mechanisms.
De nombreuses études ont démontrées l'implication du microbiote intestinal dans la physiologie et la physiopathologie de l'hôte. Parmi les bactéries probiotiques, Escherichia coli Nissle 1917 a été décrite pour ses propriétés analgésiques. L'étude d'extraits lipidiques de cette bactérie par spectrométrie de masse à haute résolution a permis d'identifier le C12AsnGABA, un lipopeptide qu'elle synthétise via son ilot pks. In vivo, le C12AsnGABA est capable d'inhiber l'hypersensibilité viscérale. Ce lipopeptide bactérien possède donc des propriétés analgésiques. Afin de déterminer si le C12AsnGABA appartient à une nouvelle famille lipidique, nous avons étendu l'analyse à plusieurs espèces bactériennes et mis en place un workflow analytique de chromatographie liquide couplée à la spectrométrie de masse en tandem à haute résolution spécifique aux lipopeptides. Celui-ci, comprend plusieurs étapes interconnectées entres-elles et indispensables ayant été optimisées séparément. Vingt-trois nouveaux lipides bactériens ont ainsi pu être caractérisés. Classiquement, l'élucidation structurale de ces composés est réalisée en électrospray à l'aide de la spectrométrie de masse en tandem après de la fragmentation par dissociation induite par collision. Lors de ma thèse, nous avons combiné les modes d'activation résonnant et non résonnant afin de mettre en évidence les pertes consécutives et les pertes directes pour permettre une meilleure compréhension des mécanismes de fragmentations impliqués. Parmi les résultats obtenus, des ions fragments produits inattendus ont été découverts et ont fait l'objet d'une seconde étude. Les courbes d'évolutions des profils en fonction de l'énergie ont été réalisées et ont permis de mettre en évidence pour la première fois la présence de courbes Gaussiennes élargies et de courbes multi-composites. Ce comportement, jamais décrit auparavant, questionne sur l'origine de ces processus qui semblent être indépendant de l'instrumentation. Nous avons considéré la possibilité que deux chemins réactionnels puissent mener à la formation d'un même ion produit fragment dans le cas des courbes Gaussiennes élargies. Dans le cas des courbes composites, nous avons émis l'hypothèse que deux chemins réactionnels, le premier à basse énergie et le second à plus haute énergie menait chacun à la formation d'un ion de structure différente mais de masse identique. Par des analyses de mobilité ionique cyclique couplée à de la spectrométrie de masse et des calculs quantiques, nous avons pu confirmer nos hypothèses. Ces travaux de thèse ont permis d'identifier 23 nouveaux composés produits par le microbiote intestinal. Leur caractérisation structurale nous a permis de d'identifier des comportements de fragmentation inattendu générant des ions fragments d'acides gras jamais décrits. Nous avons démontré que deux chemins réactionnels pouvaient exister pour générer deux ions produits de même rapport masse sur charge mais de structures différentes, se traduisant par des courbes composites.
