Laboratoire de Glycochimie, des Antimicrobiens
et des Agroressources UMR 7378 CNRS


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Christine CEZARD

Maître de Conférences

Mail :

Tel : 03 22 82 76 73

Fax : 03 22 82 75 60

Axe de recherche : Chimie pour le Vivant

Description des travaux de recherche

Afin de mieux comprendre les mécanismes régissant les relations structure-activité au sein de systèmes à visée thérapeutique, des calculs de chimie quantique et de dynamique moléculaire sont menés en complément des synthèses effectuées au laboratoire.

  • Complexes cyclodextrines-ligand : Étude par dynamique moléculaire du comportement de cyclodextrines natives et substituées en solution,  de leur pouvoir complexant ainsi que de l’impact de la nature du substituant et du solvant.
  • Hétérocycles azotés : Étude par chimie quantique de réactions d’alkylations énantiosélectives de dérivés de pipéridines et pipérazines afin d’en déterminer le chemin réactionnel et identifier les états de transition.
  • Peptidomimétiques : Étude structurales de cyclopeptides afin d’élucider leur structure secondaire par des méthodes de dynamique moléculaire et spectroscopiques de type FT-IR et dichroïsme circulaire. 

Mots clés : N.C.

Sélection de publications

Fundamental insight into the interaction between a lithium salt and an inorganic filler for ion mobility using a synergic theoretical-experimental approach
Bidal, J.; CÉZard, C.; Bouvier, B.; Hadad, C.; Nguyen Van Nhien, A.; Becuwe, M.
J. Colloid Interface Sci. 2022.
The present paper aims at providing a fundamental insight into the interaction between a lithium salt and an inorganic filler in a perspective of lithium mobility. Through a synergistic approach, coupling experimental results and molecular dynamics simulations, the influence of the surface chemical state of the nanosilica Stöber-type on the dissociation of LiTFSI and its impact on the lithium conduction properties are studied. For this purpose, the surface modification of silica nanoparticles was performed by different methods such as calcination, lithiation and capping with organosilane. The impact of the surface modification on the dissociation of the lithium salt is further investigated by electrochemical impedance spectroscopy after impregnation of the material with a defined amount of lithium salt. The combined experimental and in silico analyses of the results, performed for the first time on such systems, allow a detailed understanding of the interaction between the salt and the support and should prove itself useful for the future design of hybrid polymer electrolytes in new generation batteries.

Cyclodextrin complexation studies as the first step for repurposing of chlorpromazine
Wang, Z.; Landy, D.; Sizun, C.; Cézard, C.; Solgadi, A.; Przybylski, C.; de Chaisemartin, L.; Herfindal, L.; Barratt, G.; Legrand, F.-X.
Int. J. Pharm. 2020, 584, 119391.
The antipsychotic drug chlorpromazine (CPZ) has potential for the treatment of acute myeloid leukemia, if central nervous system side-effects resulting from its passage through the blood–brain barrier can be prevented. A robust drug delivery system for repurposed CPZ would be drug-in-cyclodextrin-in-liposome that would redirect the drug away from the brain while avoiding premature release in the circulation. As a first step, CPZ complexation with cyclodextrin (CD) has been studied. The stoichiometry, binding constant, enthalpy, and entropy of complex formation between CPZ and a panel of CDs was investigated by isothermal titration calorimetry (ITC). All the tested CDs were able to include CPZ, in the form of 1:1, 1:2 or a mixture of 1:1 and 1:2 complexes. In particular, a substituted γ-CD, sugammadex (the octasodium salt of octakis(6-deoxy-6-S-(2-carboxyethyl)-6-thio)cyclomaltooctaose), formed exclusively 1:2 complexes with an extremely high association constant of 6.37 × 109 M−2. Complexes were further characterized by heat capacity changes, one- and two-dimensional (ROESY) nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics simulations. Finally, protection of CPZ against photodegradation by CDs was assessed. This was accelerated rather than reduced by complexation with CD. Altogether these results provide a molecular basis for the use of CD in delayed release formulations for CPZ.

New biobased-zwitterionic ionic liquids: efficiency and biocompatibility for the development of sustainable biorefinery processes
Huet, G.; Araya-Farias, M.; Alayoubi, R.; Laclef, S.; Bouvier, B.; Gosselin, I.; Cézard, C.; Roulard, R.; Courty, M.; Hadad, C.; Husson, E.; Sarazin, C.; Nguyen Van Nhien, A.
Green Chem. 2020, 22, 2935-2946.
A new family of biobased-zwitterionic ionic liquids (ZILs) have been synthesized starting from the renewable resource l-histidine natural amino acid and varying the lengths of the alkyl chains. These ZIL derivatives were firstly studied for their biocompatibility with different microorganisms including bacteria, molds and yeast. The obtained MIC values indicated that all the microorganisms were 5 to 25 times more tolerant to ZIL derivatives than the robust 1-ethyl-3-methylimidazolium acetate [C2mim][OAc] used as a reference. Modeling studies also revealed that the presence of the cation and the anion on the same skeleton together with the length of the N-alkyl chain would govern the biocompatibility of these neoteric solvents. Among the different synthesized ZILs, the N,N′-diethyl derivative has been demonstrated to be a suitable eco-alternative to the classically used [C2mim][OAc] for efficient pretreatment of harwood sawdust leading to a significant improvement of enzymatic saccharification. In addition, with up to a 5% w/v concentration in the culture medium, ZILs did not induce deleterious effects on fermentative yeast growth nor ethanol production.

Ironing out pyoverdine’s chromophore structure: serendipity or design?
Cézard, C.; Sonnet, P.; Bouvier, B.
JBIC Journal of Biological Inorganic Chemistry 2019.
Pyoverdines are Pseudomonas aeruginosa’s primary siderophores. These molecules, composed of a fluorescent chromophore attached to a peptide chain of 6–14 amino acids, are synthesized by the bacterium to scavenge iron (essential to its survival and growth) from its environment. Hijacking the siderophore pathway to use pyoverdine–antibiotic compounds in a Trojan horse approach has shown promise but remains very challenging because of the synthetic efforts involved. Indeed, both possible approaches (grafting an antibiotic on pyoverdine harvested from Pseudomonas or designing a total synthesis route) are costly, time-consuming and low-yield tasks. Designing comparatively simple analogs featuring the salient properties of the original siderophore is thus crucial for the conception of novel antibiotics to fight bacterial resistance. In this work, we focus on the replacement of the pyoverdine chromophore, a major roadblock on the synthetic pathway. We propose three simpler analogs and evaluate their ability to complex iron and interact with the FpvA transporter using molecular modeling techniques. Based on these results, we discuss the role of the native chromophore’s main features (polycyclicity, positive charge, flexibility) on pyoverdine’s ability to bind iron and be recognized by membrane transporter FpvA and propose guidelines for the design of effective synthetic siderophores.

Impact of iron coordination isomerism on pyoverdine recognition by the FpvA membrane transporter of Pseudomonas aeruginosa
Bouvier, B.; Cezard, C.
Phys. Chem. Chem. Phys. 2017, 19, 29498-29507.
Pyoverdines, the primary siderophores of Pseudomonas bacteria, scavenge the iron essential to bacterial life in the outside medium and transport it back into the periplasm. Despite their relative simplicity, pyoverdines feature remarkably flexible recognition characteristics whose origins at the atomistic level remain only partially understood: the ability to bind other metals than ferric iron, the capacity of outer membrane transporters to recognize and internalize noncognate pyoverdines from other pseudomonads... One of the less examined factors behind this polymorphic recognition lies in the ability for pyoverdines to bind iron with two distinct chiralities, at the cost of a conformational switch. Herein, we use free energy simulations to study how the stereochemistry of the iron chelating groups influences the structure and dynamics of two common pyoverdines and impacts their recognition by the FpvA membrane transporter of P. aeruginosa. We show that conformational preferences for one metal binding chirality over the other, observed in solution depending on the nature of the pyoverdine, are canceled out by the FpvA transporter, which recognizes both chiralities equally well for both pyoverdines under study. However, FpvA discriminates between pyoverdines by altering the kinetics of stereoisomer interconversion. We present structural causes of this intriguing recognition mechanism and discuss its possible significance in the context of the competitive scavenging of iron.

The origin of the stereoselective alkylation of 3-substituted-2-oxopiperazines: A computational investigation
Cézard, C.; Bouvier, B.; Dassonville-Klimpt, A.; Sonnet, P.
Computational and Theoretical Chemistry 2016, 1078, 1-8.
2-Oxopiperazines and their derivatives are important pharmacophores found in numerous bioactive products. The potency of these compounds depends on the nature and/or position of their substituent(s) as well as on their chirality. Hence, it is important to develop, control and optimize synthetic routes leading to enantiomerically pure substituted 2-oxopiperazines. In this work we report on the origin of this stereoselectivity, upon alkylation of 2-oxopiperazines at position C3, studied by means of quantum chemistry calculations. Indeed, this alkylation with methyl chloride is predicted to afford mainly the exo product with a 98:2 ratio. To this purpose, we model the reaction path leading to both enantiomers by scrutinizing the structures and energetics of the pre-reaction complexes, the transition states and the post-reaction complexes. The computational results are in good agreement with the experimental observations, and provide valuable insights into the origins of this specificity. From the conformational analysis of the piperazine ring and of intramolecular interaction patterns, we show that the enantiofacial discrimination is achieved by a subtle balance between sterical hindrance and control of the conformation of the piperazine ring.

Probing the common alkali metal affinity of native and variously methylated [small beta]-cyclodextrins by combining electrospray-tandem mass spectrometry and molecular modeling
Przybylski, C.; Bonnet, V.; Cezard, C.
Phys. Chem. Chem. Phys. 2015, 17, 19288-19305.
In the study herein, we investigated the solution and gas phase affinity of native and variously methylated [small beta]-cyclodextrins (CDs) as hosts towards three common alkali metals as guests namely lithium, sodium and potassium. For this purpose, two complementary approaches have been employed: electrospray-tandem mass spectrometry (ESI-MS/MS) with two energetic regimes: Collision Induced Dissociation (CID) and Higher Collision Dissociation (HCD), respectively, and DFT molecular modeling. These approaches have been achieved by taking into account the interaction of either one or two alkali metals with the host molecules. The results showed a good agreement between experimental and theoretical data. It was demonstrated that increasing the methylation degree strengthened the gas phase affinity towards all studied alkali metals. Furthermore, it was established that the cation selectivity was Na+ > Li+ > K+ and Li+ > Na+ > K+ for the solution and gas phase, respectively.

Selectivity of pyoverdine recognition by the FpvA receptor of Pseudomonas aeruginosa from molecular dynamics simulations
Bouvier, B.; Cezard, C.; Sonnet, P.
Phys. Chem. Chem. Phys. 2015, 17, 18022-18034.
The Gram-negative bacterium Pseudomonas aeruginosa, a ubiquitous human opportunistic pathogen, has developed resistances to multiple antibiotics. It uses its primary native siderophore, pyoverdine, to scavenge the iron essential to its growth in the outside medium and transport it back into its cytoplasm. The FpvA receptor on the bacterial outer membrane recognizes and internalizes pyoverdine bearing its iron payload, but can also bind pyoverdines from other Pseudomonads or synthetic analogues. Pyoverdine derivatives could therefore be used as vectors to deliver antibiotics into the bacterium. In this study, we use molecular dynamics and free energy calculations to characterize the mechanisms and thermodynamics of the recognition of the native pyoverdines of P. aeruginosa and P. fluorescens by FpvA. Based on these results, we delineate the features that pyoverdines with high affinity for FpvA should possess. In particular, we show that (i) the dynamics and interaction of the unbound pyoverdines with water should be optimized with equal care as the interface contacts in the complex with FpvA; (ii) the C-terminal extremity of the pyoverdine chain, which appears to play no role in the bound complex, is involved in the intermediate stages of recognition; and (iii) the length and cyclicity of the pyoverdine chain can be used to fine-tune the kinetics of the recognition mechanism.

Diesterification of 3-[(β-Cyclodextrinyl)succinamido]propane-1,2-diol Catalysed by Lipase: Diastereoselectivity or Tridimensional Substrate Specificity?
Gervaise, C.; Bonnet, V.; Nolay, F.; Cezard, C.; Stasik, I.; Sarazin, C.; Djedaini-Pilard, F.
Eur. J. Org. Chem. 2014, 2014, 6200-6209.
The transesterification of 3-[(β-cyclodextrinyl)succinamido]propane-1,2-diol with fatty esters catalyzed by immobilized lipase from Mucor miehei occurred with very different conversions of the two diastereoisomers [(R)- or (S)-amidopropanediol]. The highest conversion obsd. with the (S)-amidopropanediol can be related to either lipase diastereoselectivity or substrate specificity. To investigate the diastereoselectivity of the lipase, diastereoisomers of the methylated β-cyclodextrin were replaced by methylated glucopyranoside or methylleucine. No discrimination of the diastereoisomers by lipase was obsd. Mol. modeling was performed to assess the lipase selectivity towards the two diastereoisomers. It was found that the (R)-amidopropanediol is stabilized by hydrogen bonding with the cyclodextrin rim resulting in less reactive hydroxy groups.