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Beaupre BA, Moran GR. N5 Is the New C4a: Biochemical Functionalization of Reduced Flavins at the N5 Position. Front Mol Biosci 2020; 7:598912. [PMID: 33195440 PMCID: PMC7662398 DOI: 10.3389/fmolb.2020.598912] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 10/05/2020] [Indexed: 12/31/2022] Open
Abstract
For three decades the C4a-position of reduced flavins was the known site for covalency within flavoenzymes. The reactivity of this position of the reduced isoalloxazine ring with the dioxygen ground-state triplet established the C4a as a site capable of one-electron chemistry. Within the last two decades new types of reduced flavin reactivity have been documented. These studies reveal that the N5 position is also a protean site of reactivity, that is capable of nucleophilic attack to form covalent bonds with substrates. In addition, though the precise mechanism of dioxygen reactivity is yet to be definitively demonstrated, it is clear that the N5 position is directly involved in substrate oxygenation in some enzymes. In this review we document the lineage of discoveries that identified five unique modes of N5 reactivity that collectively illustrate the versatility of this position of the reduced isoalloxazine ring.
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Affiliation(s)
- Brett A Beaupre
- Department of Chemistry and Biochemistry, Loyola University Chicago, Chicago, IL, United States
| | - Graham R Moran
- Department of Chemistry and Biochemistry, Loyola University Chicago, Chicago, IL, United States
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2
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Colombo C, Pitirollo O, Lay L. Recent Advances in the Synthesis of Glycoconjugates for Vaccine Development. Molecules 2018; 23:molecules23071712. [PMID: 30011851 PMCID: PMC6099631 DOI: 10.3390/molecules23071712] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 07/09/2018] [Accepted: 07/11/2018] [Indexed: 12/25/2022] Open
Abstract
During the last decade there has been a growing interest in glycoimmunology, a relatively new research field dealing with the specific interactions of carbohydrates with the immune system. Pathogens’ cell surfaces are covered by a thick layer of oligo- and polysaccharides that are crucial virulence factors, as they mediate receptors binding on host cells for initial adhesion and organism invasion. Since in most cases these saccharide structures are uniquely exposed on the pathogen surface, they represent attractive targets for vaccine design. Polysaccharides isolated from cell walls of microorganisms and chemically conjugated to immunogenic proteins have been used as antigens for vaccine development for a range of infectious diseases. However, several challenges are associated with carbohydrate antigens purified from natural sources, such as their difficult characterization and heterogeneous composition. Consequently, glycoconjugates with chemically well-defined structures, that are able to confer highly reproducible biological properties and a better safety profile, are at the forefront of vaccine development. Following on from our previous review on the subject, in the present account we specifically focus on the most recent advances in the synthesis and preliminary immunological evaluation of next generation glycoconjugate vaccines designed to target bacterial and fungal infections that have been reported in the literature since 2011.
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Affiliation(s)
- Cinzia Colombo
- Dipartimento di Chimica, Universita' degli Studi di Milano, via Golgi 19, 20133 Milano, Italy.
| | - Olimpia Pitirollo
- Dipartimento di Chimica, Universita' degli Studi di Milano, via Golgi 19, 20133 Milano, Italy.
| | - Luigi Lay
- Dipartimento di Chimica, Universita' degli Studi di Milano, via Golgi 19, 20133 Milano, Italy.
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3
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UDP-4-Keto-6-Deoxyglucose, a Transient Antifungal Metabolite, Weakens the Fungal Cell Wall Partly by Inhibition of UDP-Galactopyranose Mutase. mBio 2017; 8:mBio.01559-17. [PMID: 29162710 PMCID: PMC5698552 DOI: 10.1128/mbio.01559-17] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Can accumulation of a normally transient metabolite affect fungal biology? UDP-4-keto-6-deoxyglucose (UDP-KDG) represents an intermediate stage in conversion of UDP-glucose to UDP-rhamnose. Normally, UDP-KDG is not detected in living cells, because it is quickly converted to UDP-rhamnose by the enzyme UDP-4-keto-6-deoxyglucose-3,5-epimerase/-4-reductase (ER). We previously found that deletion of the er gene in Botrytis cinerea resulted in accumulation of UDP-KDG to levels that were toxic to the fungus due to destabilization of the cell wall. Here we show that these negative effects are at least partly due to inhibition by UDP-KDG of the enzyme UDP-galactopyranose mutase (UGM), which reversibly converts UDP-galactopyranose (UDP-Galp) to UDP-galactofuranose (UDP-Galf). An enzymatic activity assay showed that UDP-KDG inhibits the B. cinerea UGM enzyme with a Ki of 221.9 µM. Deletion of the ugm gene resulted in strains with weakened cell walls and phenotypes that were similar to those of the er deletion strain, which accumulates UDP-KDG. Galf residue levels were completely abolished in the Δugm strain and reduced in the Δer strain, while overexpression of the ugm gene in the background of a Δer strain restored Galf levels and alleviated the phenotypes. Collectively, our results show that the antifungal activity of UDP-KDG is due to inhibition of UGM and possibly other nucleotide sugar-modifying enzymes and that the rhamnose metabolic pathway serves as a shunt that prevents accumulation of UDP-KDG to toxic levels. These findings, together with the fact that there is no Galf in mammals, support the possibility of developing UDP-KDG or its derivatives as antifungal drugs.IMPORTANCE Nucleotide sugars are donors for the sugars in fungal wall polymers. We showed that production of the minor sugar rhamnose is used primarily to neutralize the toxic intermediate compound UDP-KDG. This surprising finding highlights a completely new role for minor sugars and other secondary metabolites with undetermined function. Furthermore, the toxic potential of predicted transition metabolites that never accumulate in cells under natural conditions are highlighted. We demonstrate that UDP-KDG inhibits the UDP-galactopyranose mutase enzyme, thereby affecting production of Galf, which is one of the components of cell wall glycans. Given the structural similarity, UDP-KDG likely inhibits additional nucleotide sugar-utilizing enzymes, a hypothesis that is also supported by our findings. Our results suggest that UDP-KDG could serve as a template to develop antifungal drugs.
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Winton VJ, Justen AM, Deng H, Kiessling LL. Deleterious Consequences of UDP-Galactopyranose Mutase Inhibition for Nematodes. ACS Chem Biol 2017; 12:2354-2361. [PMID: 28732158 DOI: 10.1021/acschembio.7b00487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Parasitic nematodes pose a serious threat to agriculture, livestock, and human health. Increasing resistance to antiparasitic agents underscores the need to replenish our anthelmintic arsenal. The nonpathogenic Caenorhabditis elegans, which serves as an effective model of parasitic helminths, has been used to search for new anthelmintic leads. We previously reported small-molecule inhibitors of the essential C. elegans protein UDP-galactopyranose mutase (UGM or Glf). This enzyme is required for the generation of galactofuranose (Galf)-containing glycans and is needed in nematodes for proper cuticle formation. Though our first-generation inhibitors were effective in vitro, they elicited no phenotypic effects. These findings are consistent with the known difficulty of targeting nematodes. C. elegans is recalcitrant to pharmacological modulation; typically, less than 0.02% of small molecules elicit a phenotypic effect, even at 40 μM. We postulated that the lack of activity of the UGM inhibitors was due to their carboxylic acid group, which can be exploited by nematodes for detoxification. We therefore tested whether replacement of the carboxylate with an N-acylsulfonamide surrogate would result in active compounds. UGM inhibitors with the carboxylate mimetic can phenocopy the deleterious consequences of UGM depletion in C. elegans. These findings support the use of UGM inhibitors as anthelmintic agents. They also outline a strategy to render small-molecule carboxylates more effective against nematodes.
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Affiliation(s)
- Valerie J. Winton
- Department
of Chemistry, University of Wisconsin—Madison, 1101 University Avenue, Madison, Wisconsin 53706-1322, United States
| | - Alexander M. Justen
- Department
of Biochemistry, University of Wisconsin—Madison, 433 Babcock Drive, Madison, Wisconsin 53706-1544, United States
| | - Helen Deng
- Department
of Biochemistry, University of Wisconsin—Madison, 433 Babcock Drive, Madison, Wisconsin 53706-1544, United States
| | - Laura L. Kiessling
- Department
of Chemistry, University of Wisconsin—Madison, 1101 University Avenue, Madison, Wisconsin 53706-1322, United States
- Department
of Biochemistry, University of Wisconsin—Madison, 433 Babcock Drive, Madison, Wisconsin 53706-1544, United States
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5
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Wangkanont K, Winton VJ, Forest KT, Kiessling LL. Conformational Control of UDP-Galactopyranose Mutase Inhibition. Biochemistry 2017; 56:3983-3992. [PMID: 28608671 PMCID: PMC5739916 DOI: 10.1021/acs.biochem.7b00189] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
UDP-galactopyranose mutase (Glf or UGM) catalyzes the formation of uridine 5'-diphosphate-α-d-galactofuranose (UDP-Galf) from UDP-galactopyranose (UDP-Galp). The enzyme is required for the production of Galf-containing glycans. UGM is absent in mammals, but members of the Corynebacterineae suborder require UGM for cell envelope biosynthesis. The need for UGM in some pathogens has prompted the search for inhibitors that could serve as antibiotic leads. Optimizing inhibitor potency, however, has been challenging. The UGM from Klebsiella pneumoniae (KpUGM), which is not required for viability, is more effectively impeded by small-molecule inhibitors than are essential UGMs from species such as Mycobacterium tuberculosis or Corynebacterium diphtheriae. Why KpUGM is more susceptible to inhibition than other orthologs is not clear. One potential source of difference is UGM ortholog conformation. We previously determined a structure of CdUGM bound to a triazolothiadiazine inhibitor in the open form, but it was unclear whether the small-molecule inhibitor bound this form or to the closed form. By varying the terminal tag (CdUGM-His6 and GSG-CdUGM), we crystallized CdUGM to capture the enzyme in different conformations. These structures reveal a pocket in the active site that can be exploited to augment inhibitor affinity. Moreover, they suggest the inhibitor binds the open form of most prokaryotic UGMs but can bind the closed form of KpUGM. This model and the structures suggest strategies for optimizing inhibitor potency by exploiting UGM conformational flexibility.
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Affiliation(s)
- Kittikhun Wangkanont
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Valerie J. Winton
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Katrina T. Forest
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA,Department of Bacteriology University of Wisconsin-Madison, Madison, WI, 53706, USA,Corresponding authors: Katrina T. Forest (Tel. 608-265-3566, ) and Laura L. Kiessling (Tel. 608-262-0541, )
| | - Laura L. Kiessling
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA,Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA,Corresponding authors: Katrina T. Forest (Tel. 608-265-3566, ) and Laura L. Kiessling (Tel. 608-262-0541, )
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6
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Villaume SA, Fu J, N'Go I, Liang H, Lou H, Kremer L, Pan W, Vincent SP. Natural and Synthetic Flavonoids as Potent
Mycobacterium tuberculosis
UGM Inhibitors. Chemistry 2017; 23:10423-10429. [DOI: 10.1002/chem.201701812] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Indexed: 01/16/2023]
Affiliation(s)
- Sydney A. Villaume
- Department of ChemistryUniversity of Namur Rue de Bruxelles 61 5000 Namur Belgium
| | - Jian Fu
- Department of ChemistryUniversity of Namur Rue de Bruxelles 61 5000 Namur Belgium
| | - Inès N'Go
- Department of ChemistryUniversity of Namur Rue de Bruxelles 61 5000 Namur Belgium
| | - Hui Liang
- State Key Laboratory of Functions and Applications of Medicinal PlantsGuizhou Medical University 3491 Baijin Road Guiyang 550014 P. R. China
| | - Huayong Lou
- State Key Laboratory of Functions and Applications of Medicinal PlantsGuizhou Medical University 3491 Baijin Road Guiyang 550014 P. R. China
| | - Laurent Kremer
- IRIM (ex-CPBS)-UMR 9004Infectious Disease Research Institute of Montpellier (IDRIM)Université de Montpellier, CNRS 34293 Montpellier France
- INSERMIRIM 34293 Montpellier France
| | - Weidong Pan
- State Key Laboratory of Functions and Applications of Medicinal PlantsGuizhou Medical University 3491 Baijin Road Guiyang 550014 P. R. China
| | - Stéphane P. Vincent
- Department of ChemistryUniversity of Namur Rue de Bruxelles 61 5000 Namur Belgium
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7
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Shi Y, Colombo C, Kuttiyatveetil JRA, Zalatar N, van Straaten KE, Mohan S, Sanders DAR, Pinto BM. A Second, Druggable Binding Site in UDP-Galactopyranose Mutase from Mycobacterium tuberculosis? Chembiochem 2016; 17:2264-2273. [PMID: 27653508 DOI: 10.1002/cbic.201600469] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Indexed: 11/10/2022]
Abstract
UDP-galactopyranose mutase (UGM), a key enzyme in the biosynthesis of mycobacterial cell walls, is a potential target for the treatment of tuberculosis. In this work, we investigate binding models of a non-substrate-like inhibitor, MS-208, with M. tuberculosis UGM. Initial saturation transfer difference (STD) NMR experiments indicated a lack of direct competition between MS-208 and the enzyme substrate, and subsequent kinetic assays showed mixed inhibition. We thus hypothesized that MS-208 binds at an allosteric binding site (A-site) instead of the enzyme active site (S-site). A candidate A-site was identified in a subsequent computational study, and the overall hypothesis was supported by ensuing mutagenesis studies of the A-site. Further molecular dynamics studies led us to propose that MS-208 inhibition occurs by preventing complete closure of an active site mobile loop that is necessary for productive substrate binding. The results suggest the presence of an A-site with potential druggability, opening up new opportunities for the development of novel drug candidates against tuberculosis.
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Affiliation(s)
- Yun Shi
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Cinzia Colombo
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Jijin R A Kuttiyatveetil
- Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan, S7N 5C9, Canada
| | - Nataliya Zalatar
- Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan, S7N 5C9, Canada
| | - Karin E van Straaten
- Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan, S7N 5C9, Canada
| | - Sankar Mohan
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - David A R Sanders
- Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan, S7N 5C9, Canada
| | - B Mario Pinto
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
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8
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Mechanism-based candidate inhibitors of uridine diphosphate galactopyranose mutase (UGM). Carbohydr Res 2015; 419:1-7. [PMID: 26595659 DOI: 10.1016/j.carres.2015.10.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2015] [Revised: 10/20/2015] [Accepted: 10/22/2015] [Indexed: 01/07/2023]
Abstract
Uridine diphosphate-galactopyranose mutase (UGM), an enzyme found in many eukaryotic and prokaryotic human pathogens, catalyzes the interconversion of UDP-galactopyranose (UDP-Galp) and UDP-galactofuranose (UDP-Galf), the latter being used as the biosynthetic precursor of the galactofuranose polymer portion of the mycobacterium cell wall. We report here the synthesis of a sulfonium and selenonium ion with an appended polyhydroxylated side chain. These compounds were designed as transition state mimics of the UGM-catalyzed reaction, where the head groups carrying a permanent positive charge were designed to mimic both the shape and positive charge of the proposed galactopyranosyl cation-like transition state. An HPLC-based UGM inhibition assay indicated that the compounds inhibited about 25% of UGM activity at 500 µM concentration.
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9
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Kincaid VA, London N, Wangkanont K, Wesener DA, Marcus SA, Héroux A, Nedyalkova L, Talaat AM, Forest KT, Shoichet BK, Kiessling LL. Virtual Screening for UDP-Galactopyranose Mutase Ligands Identifies a New Class of Antimycobacterial Agents. ACS Chem Biol 2015. [PMID: 26214585 DOI: 10.1021/acschembio.5b00370] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Galactofuranose (Galf) is present in glycans critical for the virulence and viability of several pathogenic microbes, including Mycobacterium tuberculosis, yet the monosaccharide is absent from mammalian glycans. Uridine 5'-diphosphate-galactopyranose mutase (UGM) catalyzes the formation of UDP-Galf, which is required to produce Galf-containing glycoconjugates. Inhibitors of UGM have therefore been sought, both as antimicrobial leads and as tools to delineate the roles of Galf in cells. Obtaining cell permeable UGM probes by either design or high throughput screens has been difficult, as has elucidating how UGM binds small molecule, noncarbohydrate inhibitors. To address these issues, we employed structure-based virtual screening to uncover new inhibitor chemotypes, including a triazolothiadiazine series. These compounds are among the most potent antimycobacterial UGM inhibitors described. They also facilitated determination of a UGM-small molecule inhibitor structure, which can guide optimization. A comparison of results from the computational screen and a high-throughput fluorescence polarization (FP) screen indicated that the scaffold hits from the former had been evaluated in the FP screen but missed. By focusing on promising compounds, the virtual screen rescued false negatives, providing a blueprint for generating new UGM probes and therapeutic leads.
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Affiliation(s)
- Virginia A. Kincaid
- Department
of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Nir London
- Department
of Pharmaceutical Chemistry, University of California—San Francisco, San Francisco, California 94158, United States
| | - Kittikhun Wangkanont
- Department
of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Darryl A. Wesener
- Department
of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Sarah A. Marcus
- Department
of Pathobiological Sciences, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Annie Héroux
- Photon
Sciences Directorate, Brookhaven National Laboratories, Upton, New York 11973, United States
| | - Lyudmila Nedyalkova
- Ontario Institute
of Cancer Research and Faculty of Pharmacy, University of Toronto, Toronto, Canada
| | - Adel M. Talaat
- Department
of Pathobiological Sciences, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Katrina T. Forest
- Department
of Bacteriology, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Brian K. Shoichet
- Department
of Pharmaceutical Chemistry, University of California—San Francisco, San Francisco, California 94158, United States
- Ontario Institute
of Cancer Research and Faculty of Pharmacy, University of Toronto, Toronto, Canada
| | - Laura L. Kiessling
- Department
of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
- Department
of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
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10
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Wang S, Cuesta-Seijo JA, Striebeck A, Lafont D, Palcic MM, Vidal S. Design of Glycosyltransferase Inhibitors: Serine Analogues as Pyrophosphate Surrogates? Chempluschem 2015; 80:1525-1532. [DOI: 10.1002/cplu.201500282] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Indexed: 01/07/2023]
Affiliation(s)
- Shuai Wang
- Institut de Chimie et Biochimie Moléculaires et Supramoléculaires; Laboratoire de Chimie Organique 2-Glycochimie, UMR 5246; CNRS and Université Claude Bernard Lyon 1; 43 Boulevard du 11 Novembre 1918 69622 Villeurbanne France
| | | | | | - Dominique Lafont
- Institut de Chimie et Biochimie Moléculaires et Supramoléculaires; Laboratoire de Chimie Organique 2-Glycochimie, UMR 5246; CNRS and Université Claude Bernard Lyon 1; 43 Boulevard du 11 Novembre 1918 69622 Villeurbanne France
| | - Monica M. Palcic
- Carlsberg Laboratory; Gamle Carlsberg Vej 10 1799 Copenhagen V Denmark
- Department of Biochemistry and Microbiology; University of Victoria; Victoria BC V8W 3P6 Canada
| | - Sébastien Vidal
- Institut de Chimie et Biochimie Moléculaires et Supramoléculaires; Laboratoire de Chimie Organique 2-Glycochimie, UMR 5246; CNRS and Université Claude Bernard Lyon 1; 43 Boulevard du 11 Novembre 1918 69622 Villeurbanne France
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