Publications by authors named "Simon Ollivier"

3 Publications

  • Page 1 of 1

Synthesis of an Exhaustive Library of Naturally Occurring Gal-Man and Gal-Man Disaccharides. Toward Fingerprinting According to Ring Size by Advanced Mass Spectrometry-Based IM-MS and IRMPD.

J Org Chem 2021 May 20;86(9):6390-6405. Epub 2021 Apr 20.

Univ Rennes, Ecole Nationale Supérieure de Chimie de Rennes, CNRS, ISCR - UMR 6226, F-35000 Rennes, France.

Nature offers a huge diversity of glycosidic derivatives. Among numerous structural modulations, the nature of the ring size of hexosides may induce significant differences on both biological and physicochemical properties of the glycoconjugate of interest. On this assumption, we expect that small disaccharides bearing either a furanosyl entity or a pyranosyl residue would give a specific signature, even in the gas phase. On the basis of the scope of mass spectrometry, two analytical techniques to register those signatures were considered, i.e., the ion mobility (IM) and the infrared multiple photon dissociation (IRMPD), in order to build up cross-linked databases. d-Galactose occurs in natural products in both tautomeric forms and presents all possible regioisomers when linked to d-mannose. Consequently, the four reducing Gal-Man disaccharides as well as the four Gal-Man counterparts were first synthesized according to a highly convergent approach, and IM-MS and IRMPD-MS data were second collected. Both techniques used afforded signatures, specific to the nature of the connectivity between the two glycosyl entities.
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http://dx.doi.org/10.1021/acs.joc.1c00250DOI Listing
May 2021

Anomeric Retention of Carbohydrates in Multistage Cyclic Ion Mobility (IMS): De Novo Structural Elucidation of Enzymatically Produced Mannosides.

Anal Chem 2021 04 8;93(15):6254-6261. Epub 2021 Apr 8.

INRAE, UR BIA, F-44316 Nantes, France.

Carbohydrates are complex structures that still challenge analysts today because of their different levels of isomerism, notably the anomerism of the glycosidic bond. It has been shown recently that anomerism is preserved upon gas-phase fragmentation and that high-resolution ion mobility (IMS) can distinguish anomers. However, these concepts have yet to be applied to complex biological products. We have used high-resolution IMS on a cyclic device to characterize the reaction products of Uhgb_MS, a novel mannoside synthase of the GH130 family. We designed a so-called IMS sequence consisting of (i) separating and isolating specific IMS peaks, (ii) ejecting ions to a pre-array store cell depending on their arrival time, (iii) inducing collisional activation upon reinjection, and (iv) performing multistage IMS analysis of the fragments. First, we applied IMS sequences to purely linked α1,2- and β1,2-mannooligosaccharides, which provided us with reference drift times for fragments of known conformation. Then, we performed IMS analyses of enzymatically produced mannosides and, by comparison with the references, we succeeded in determining the intrachain anomerism of a α1,2-mannotriose and a mix-linked β/α1,2-mannotetraose-a first for a crude biological medium. Our results show that the anomerism of glycosides is maintained through multiple stages of collisional fragmentation, and that standalone high-resolution IMS and IMS can be used to characterize the intrachain anomerism in tri- and tetrasaccharides in a biological medium. This is also the first evidence that a single carbohydrate-active enzyme can synthesize both α- and β-glycosidic linkages.
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http://dx.doi.org/10.1021/acs.analchem.1c00673DOI Listing
April 2021

Taxonomically Informed Scoring Enhances Confidence in Natural Products Annotation.

Front Plant Sci 2019 25;10:1329. Epub 2019 Oct 25.

Institute of Pharmaceutical Sciences of Western Switzerland (ISPSO), University of Geneva, Centre Médical Universitaire (CMU), Geneva, Switzerland.

Mass spectrometry (MS) offers unrivalled sensitivity for the metabolite profiling of complex biological matrices encountered in natural products (NP) research. The massive and complex sets of spectral data generated by such platforms require computational approaches for their interpretation. Within such approaches, computational metabolite annotation automatically links spectral data to candidate structures a score, which is usually established between the acquired data and experimental or theoretical spectral databases (DB). This process leads to various candidate structures for each MS features. However, at this stage, obtaining high annotation confidence level remains a challenge notably due to the extensive chemodiversity of specialized metabolomes. The design of a metascore is a way to capture complementary experimental attributes and improve the annotation process. Here, we show that integrating the taxonomic position of the biological source of the analyzed samples and candidate structures enhances confidence in metabolite annotation. A script is proposed to automatically input such information at various granularity levels (species, genus, and family) and complement the score obtained between experimental spectral data and output of available computational metabolite annotation tools (ISDB-DNP, MS-Finder, Sirius). In all cases, the consideration of the taxonomic distance allowed an efficient re-ranking of the candidate structures leading to a systematic enhancement of the recall and precision rates of the tools (1.5- to 7-fold increase in the F1 score). Our results clearly demonstrate the importance of considering taxonomic information in the process of specialized metabolites annotation. This requires to access structural data systematically documented with biological origin, both for new and previously reported NPs. In this respect, the establishment of an open structural DB of specialized metabolites and their associated metadata, particularly biological sources, is timely and critical for the NP research community.
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http://dx.doi.org/10.3389/fpls.2019.01329DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6824209PMC
October 2019