Publications by authors named "Laurent Heux"

38 Publications

Biophysical analysis of the plant-specific GIPC sphingolipids reveals multiple modes of membrane regulation.

J Biol Chem 2021 Jan-Jun;296:100602. Epub 2021 Mar 27.

Laboratoire de Biogènese Membranaire, UMR 5200, CNRS, Université de Bordeaux, Villenave d'Ornon Cedex, France. Electronic address:

The plant plasma membrane (PM) is an essential barrier between the cell and the external environment, controlling signal perception and transmission. It consists of an asymmetrical lipid bilayer made up of three different lipid classes: sphingolipids, sterols, and phospholipids. The glycosyl inositol phosphoryl ceramides (GIPCs), representing up to 40% of total sphingolipids, are assumed to be almost exclusively in the outer leaflet of the PM. However, their biological role and properties are poorly defined. In this study, we investigated the role of GIPCs in membrane organization. Because GIPCs are not commercially available, we developed a protocol to extract and isolate GIPC-enriched fractions from eudicots (cauliflower and tobacco) and monocots (leek and rice). Lipidomic analysis confirmed the presence of trihydroxylated long chain bases and 2-hydroxylated very long-chain fatty acids up to 26 carbon atoms. The glycan head groups of the GIPCs from monocots and dicots were analyzed by gas chromatograph-mass spectrometry, revealing different sugar moieties. Multiple biophysics tools, namely Langmuir monolayer, ζ-Potential, light scattering, neutron reflectivity, solid state 2H-NMR, and molecular modeling, were used to investigate the physical properties of the GIPCs, as well as their interaction with free and conjugated phytosterols. We showed that GIPCs increase the thickness and electronegativity of model membranes, interact differentially with the different phytosterols species, and regulate the gel-to-fluid phase transition during temperature variations. These results unveil the multiple roles played by GIPCs in the plant PM.
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http://dx.doi.org/10.1016/j.jbc.2021.100602DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8099651PMC
March 2021

Deposition of Cellulose Nanocrystals onto Supported Lipid Membranes.

Langmuir 2020 02 4;36(6):1474-1483. Epub 2020 Feb 4.

Univ. Grenoble Alpes, CNRS, CERMAV , 38000 Grenoble , France.

The deposition of cellulose nanocrystals (CNCs) on a supported lipid bilayer (SLB) was investigated at different length scales. Quartz crystal microbalance with dissipation monitoring (QCM-D) was used to probe the bilayer formation and to show for the first time the CNC deposition onto the SLB. Specifically, classical QCM-D measurements gave estimation of the adsorbed hydrated mass and the corresponding film thickness, whereas complementary experiments using DO as the solvent allowed the quantitative determination of the hydration of the CNC layer, showing a high hydration value. Scanning force microscopy (SFM) and total internal reflection fluorescence microscopy (TIRF) were used to probe the homogeneity of the deposited layers, revealing the structural details at the particle and film length scales, respectively, thus giving information on the effect of CNC concentration on the surface coverage. The results showed that the adsorption of CNCs on the supported lipid membrane depended on lipid composition, CNC concentration, and pH conditions, and that the binding process was governed by electrostatic interactions. Under suitable conditions, a uniform film was formed, with thickness corresponding to a CNC monolayer, which provides the basis for a relevant 2D model of a primary plant cell wall.
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http://dx.doi.org/10.1021/acs.langmuir.9b02888DOI Listing
February 2020

Hybrid Gibbsite Nanoplatelet/Cellulose Nanocrystal Multilayered Coatings for Oxygen Barrier Improvement.

Front Chem 2019 17;7:507. Epub 2019 Jul 17.

Univ. Grenoble Alpes, CNRS, CERMAV, Grenoble, France.

We have investigated the ability of multilayered hybrid thin films of cellulose nanocrystals (CNCs) and gibbsite nanoplatelets (GNPs) to be built by the layer-by-layer (LbL) technique onto substrates selected for packaging applications, and to improve the oxygen barrier properties. Using complementary structural characterization techniques, namely atomic force microscopy, ellipsometry, and spectral reflectance, we show that when deposited onto model silicon substrates these hybrid films were homogenous and of reduced porosity, and were comprised of alternately deposited monolayers of GNPs and CNCs. The successful deposition of such homogeneous and dense hybrid thin films onto various types of flexible substrates showing different chemical compositions, hydrophilicity, and surface morphology, ranging from cardboard to smart paper, polyethylene (PE) films, and PE-coated cardboard was also confirmed by scanning electron microscopy observations. In view of the diversity of these substrates we could confirm the remarkable robustness of such a deposition process, likely due to (i) the adaptability of the LbL assembling technique and (ii) the strong electrostatic and hydrogen bonding interactions between GNPs and CNCs. The measurement of the oxygen transmission rate (OTR) at 23°C and 50% RH showed that the oxygen barrier properties of the bare substrates could be significantly improved (e.g., 75% decrease of the OTR) after the deposition of such thin (<100 nm) multilayered hybrid films. This lowered permeability was tentatively attributed to the highly tortuous morphology of the coating, acting to impede the gas diffusion. These partially biosourced very thin films stand as good candidates for using as coatings showing high oxygen barrier performance.
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http://dx.doi.org/10.3389/fchem.2019.00507DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6650769PMC
July 2019

Tracking of enzymatic biomass deconstruction by fungal secretomes highlights markers of lignocellulose recalcitrance.

Biotechnol Biofuels 2019 1;12:76. Epub 2019 Apr 1.

2INRA, Aix Marseille Univ., UMR1163, BBF, Biodiversité et Biotechnologie Fongiques, Marseille, France.

Background: Lignocellulose biomass is known as a recalcitrant material towards enzymatic hydrolysis, increasing the process cost in biorefinery. In nature, filamentous fungi naturally degrade lignocellulose, using an arsenal of hydrolytic and oxidative enzymes. Assessment of enzyme hydrolysis efficiency generally relies on the yield of glucose for a given biomass. To better understand the markers governing recalcitrance to enzymatic degradation, there is a need to enlarge the set of parameters followed during deconstruction.

Results: Industrially-pretreated biomass feedstocks from wheat straw, miscanthus and poplar were sequentially hydrolysed following two steps. First, standard secretome from was used to maximize cellulose hydrolysis, producing three recalcitrant lignin-enriched solid substrates. Then fungal secretomes from three basidiomycete saprotrophs ( and ) displaying various hydrolytic and oxidative enzymatic profiles were applied to these recalcitrant substrates, and compared to the secretome. As a result, most of the glucose was released after the first hydrolysis step. After the second hydrolysis step, half of the remaining glucose amount was released. Overall, glucose yield after the two sequential hydrolyses was more dependent on the biomass source than on the fungal secretomes enzymatic profile. Solid residues obtained after the two hydrolysis steps were characterized using complementary methodologies. Correlation analysis of several physico-chemical parameters showed that released glucose yield was negatively correlated with lignin content and cellulose crystallinity while positively correlated with xylose content and water sorption. Water sorption appears as a pivotal marker of the recalcitrance as it reflects chemical and structural properties of lignocellulosic biomass.

Conclusions: Fungal secretomes applied to highly recalcitrant biomass samples can further extend the release of the remaining glucose. The glucose yield can be correlated to chemical and physical markers, which appear to be independent from the biomass type and secretome. Overall, correlations between these markers reveal how nano-scale properties (polymer content and organization) influence macro-scale properties (particle size and water sorption). Further systematic assessment of these markers during enzymatic degradation will foster the development of novel cocktails to unlock the degradation of lignocellulose biomass.
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http://dx.doi.org/10.1186/s13068-019-1417-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6442405PMC
April 2019

Injectable and Gellable Chitosan Formulations Filled with Cellulose Nanofibers for Intervertebral Disc Tissue Engineering.

Polymers (Basel) 2018 Oct 27;10(11). Epub 2018 Oct 27.

Institute of Microsystems Engineering IMTEK, Laboratory for Sensors, University of Freiburg, 79110 Freiburg, Germany.

The development of non-cellularized injectable suspensions of viscous chitosan (CHI) solutions (1.7⁻3.3% (/)), filled with cellulose nanofibers (CNF) (0.02⁻0.6% (/)) of the type nanofibrillated cellulose, was proposed for viscosupplementation of the intervertebral disc nucleus pulposus tissue. The achievement of CNF/CHI formulations which can gel in situ at the disc injection site constitutes a minimally-invasive approach to restore damaged/degenerated discs. We studied physico-chemical aspects of the sol and gel states of the CNF/CHI formulations, including the rheological behavior in relation to injectability (sol state) and fiber mechanical reinforcement (gel state). CNF-CHI interactions could be evidenced by a double flow behavior due to the relaxation of the CHI polymer chains and those interacting with the CNFs. At high shear rates resembling the injection conditions with needles commonly used in surgical treatments, both the reference CHI viscous solutions and those filled with CNFs exhibited similar rheological behavior. The neutralization of the flowing and weakly acidic CNF/CHI suspensions yielded composite hydrogels in which the nanofibers reinforced the CHI matrix. We performed evaluations in relation to the biomedical application, such as the effect of the intradiscal injection of the CNF/CHI formulation in pig and rabbit spine models on disc biomechanics. We showed that the injectable formulations became hydrogels in situ after intradiscal gelation, due to CHI neutralization occurring in contact with the body fluids. No leakage of the injectate through the injection canal was observed and the gelled formulation restored the disc height and loss of mechanical properties, which is commonly related to disc degeneration.
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http://dx.doi.org/10.3390/polym10111202DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6290636PMC
October 2018

Adsorption versus grafting of poly(N-Isopropylacrylamide) in aqueous conditions on the surface of cellulose nanocrystals.

Carbohydr Polym 2019 Apr 9;210:100-109. Epub 2019 Jan 9.

Univ. Grenoble Alpes, CNRS, Grenoble INP,(1) LGP2, F-38000, Grenoble, France; Institut Universitaire de Français, F-75000, Paris, France. Electronic address:

This study proposes a grafting strategy of thermo-sensitive amine-terminated oligomers of Poly(N-Isopropylacrylamide) (Pnipam) onto the surface of Cellulose Nanocrystals (CNCs). Pnipam grafting in aqueous condition via peptidic coupling was explored to obtain CNC hydrogel with thermo-reversible aggregation and new colloidal properties. A discussion between grafting vs adsorption /presence of the Pnipam is proposed. A large range of experimental techniques was used to investigate the properties of the CNC decorated with polymer and to confirm the grafting. Elemental analysis, infrared spectroscopy, solid state NMR and conductometric titration of washed CNC-g-Pnipam demonstrate that at least a part of Pnipam was covalently bonded with CNC. A thermo-reversible aggregation was observed by Dynamic Light Scattering experiments and thermo-sensitive behavior is observed by rheological experiments. For grafted polymer the viscosity increases from 0.008 to 40 Pa∙s at low shear rate when the LCST is reached, whereas, in the case of polymer adsorption, the viscosity increases only from 0.002 to 0.3 Pa∙s. This thermo-reversible, bio-based and biocompatible system paves the way for the design of injectable hydrogel and biomedical nanocomposite materials.
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http://dx.doi.org/10.1016/j.carbpol.2019.01.022DOI Listing
April 2019

Periodate Oxidation Followed by NaBH Reduction Converts Microfibrillated Cellulose into Sterically Stabilized Neutral Cellulose Nanocrystal Suspensions.

Langmuir 2018 09 5;34(37):11066-11075. Epub 2018 Sep 5.

Univ. Grenoble Alpes, CNRS, CERMAV , 38000 Grenoble , France.

The periodate oxidation of microfibrillated cellulose followed by a reduction treatment was implemented to produce a new type of sterically stabilized cellulosic nanocrystals, which were characterized at the molecular and colloidal length scales. Solid-state NMR data showed that these treatments led to objects consisting of native cellulose and flexible polyols resulting from the oxidation and subsequent reduction of cellulose. A consistent set of data from dynamic light scattering, turbidimetry, transmission electron microscopy, and small-angle X-ray scattering experiments further showed that stable neutral elongated nanoparticles composed of a crystalline cellulosic core surrounded by a shell of dangling polyol chains were produced. The dimensions of these biosourced nanocrystals could be controlled by the degree of oxidation of the parent dialdehyde cellulose sample. The purely steric origin of the colloidal stability of these nanoparticles is a strong asset for their use under conditions where electrostatics no longer provides colloidal stability.
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http://dx.doi.org/10.1021/acs.langmuir.8b02202DOI Listing
September 2018

Current characterization methods for cellulose nanomaterials.

Chem Soc Rev 2018 Apr;47(8):2609-2679

Department of Materials Science and Engineering, Virginia Tech, 445 Old Turner St, 203 Holden Hall, Blacksburg, 24061, VA, USA.

A new family of materials comprised of cellulose, cellulose nanomaterials (CNMs), having properties and functionalities distinct from molecular cellulose and wood pulp, is being developed for applications that were once thought impossible for cellulosic materials. Commercialization, paralleled by research in this field, is fueled by the unique combination of characteristics, such as high on-axis stiffness, sustainability, scalability, and mechanical reinforcement of a wide variety of materials, leading to their utility across a broad spectrum of high-performance material applications. However, with this exponential growth in interest/activity, the development of measurement protocols necessary for consistent, reliable and accurate materials characterization has been outpaced. These protocols, developed in the broader research community, are critical for the advancement in understanding, process optimization, and utilization of CNMs in materials development. This review establishes detailed best practices, methods and techniques for characterizing CNM particle morphology, surface chemistry, surface charge, purity, crystallinity, rheological properties, mechanical properties, and toxicity for two distinct forms of CNMs: cellulose nanocrystals and cellulose nanofibrils.
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http://dx.doi.org/10.1039/c6cs00895jDOI Listing
April 2018

Rubber materials from elastomers and nanocellulose powders: filler dispersion and mechanical reinforcement.

Soft Matter 2018 Apr;14(14):2638-2648

Univ. Grenoble Alpes, CNRS, CERMAV, F-38000 Grenoble, France.

Rubber materials with well-dispersed fillers and large mechanical reinforcement have been obtained by melt-processing a diene elastomer matrix and tailored nanocellulose powders having both a high specific surface area and a modified interface. Such filler powders with a specific surface area of 180 m2 g-1 and 100 m2 g-1 have been obtained by freeze-drying suspensions of short needle-like cellulose nanocrystals (CNCs) and entangled networks of microfibrillated cellulose (MFC) in tert-butanol/water, respectively. A quantitative and toposelective filler surface esterification was performed using a gas-phase protocol either with palmitoyl chloride (PCl) to obtain a hydrophobic but non-reactive nanocellulose interface, or with 3,3'-dithiopropionic acid chloride (DTACl) to introduce reactive groups that can covalently bind the nanocellulose interface to the dienic matrix in a subsequent vulcanization process. A set of filled materials was prepared varying the filler morphology, interface and volume fraction. Transmission electron microscopy images of ultrathin cryo-sections showed that modified nanocellulose fillers presented a relatively homogeneous distribution up to a volume fraction of 20%. The materials also exhibited a significant modulus increase, while keeping an extensibility in the same range as that of the neat matrix. Strikingly, in the case of the reactive interface, a strong stress-stiffening behavior was evidenced from the upward curvature of the tensile curve, leading to a large increase of the ultimate stress (up to 7 times that of the neat matrix). Taken together, these properties, which have never been previously reported for nanocellulose-filled elastomers, match well the mechanical characteristics of industrial carbon black or silica-loaded elastomers.
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http://dx.doi.org/10.1039/C8SM00210JDOI Listing
April 2018

Heterogenization of a [NiFe] Hydrogenase Mimic through Simple and Efficient Encapsulation into a Mesoporous MOF.

Inorg Chem 2017 Dec 1;56(24):14801-14808. Epub 2017 Dec 1.

Département de Chimie Moléculaire, Univ. Grenoble Alpes, CNRS , 38000 Grenoble, France.

In the quest for new, efficient, and noble-metal-free H-evolution catalysts, hydrogenase enzymes are a source of inspiration. Here, we describe the development of a new hybrid material based on a structural and functional [NiFe]-hydrogenase model complex (NiFe) incorporated into the Zr-based MOF PCN-777. The bulk [email protected] material was synthesized by simple encapsulation. Characterization by solid-state NMR and IR spectroscopy, SEM-EDX, ICP-OES, and gas adsorption confirmed the inclusion of the guest. FTO-supported thin films of the [email protected] composite were obtained by electrophoretic deposition of the bulk material and characterized by SEM-EDX, ICP-OES, and cyclic voltammetry. The average surface concentration of electroactive NiFe catalyst in the film was found to be ∼9.6 × 10 mol cm, implying that a surprisingly high fraction (37%) of NiFe units incorporated in the MOF are electroactive. By cyclic voltammetry, we showed that NiFe maintains its electrocatalytic capabilities for H reduction inside the MOF cavities, even if under controlled-potential electrolysis conditions the activity of NiFe cannot be discerned from that of free PCN-777 and FTO.
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http://dx.doi.org/10.1021/acs.inorgchem.7b01824DOI Listing
December 2017

pH-Sensitive Interactions between Cellulose Nanocrystals and DOPC Liposomes.

Biomacromolecules 2017 Sep 29;18(9):2918-2927. Epub 2017 Aug 29.

Univ. Grenoble Alpes , Centre de Recherches sur les Macromolécules Végétales (CERMAV), F-38000 Grenoble, France.

The interaction of 1,2 dioleolyl-sn-glycero-3-phosphatidylcholine (DOPC) vesicles with cellulose nanocrystals (CNCs) using several complementary techniques. Dynamic light scattering, zeta-potential, cryo-transmission electron microscopy and isothermal titration calorimetry (ITC) analyses confirmed the formation of pH-dependent CNC-liposome complexes. ITC was used to characterize the thermodynamic properties of this interaction. Positive values of enthalpy were found at pH lower than 5 where the charge sign of the constituents was opposite. The association was more pronounced at lower pH, as indicated by the higher values of association constant. We suggest that the positive enthalpy is derived from the release of counterions from the particle hydration shell during the association and that the charge of the vesicles plays a significant role in this interaction.
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http://dx.doi.org/10.1021/acs.biomac.7b00872DOI Listing
September 2017

Structural Variations in Hybrid All-Nanoparticle Gibbsite Nanoplatelet/Cellulose Nanocrystal Multilayered Films.

Langmuir 2017 08 2;33(32):7896-7907. Epub 2017 Aug 2.

Université Grenoble Alpes, Centre de Recherches sur les Macromolécules Végétales (CERMAV) , F-38000 Grenoble, France.

Cellulose nanocrystals (CNCs) are promising biosourced building blocks for the production of high performance materials. In the last ten years, CNCs have been used in conjunction with polymers for the design of multilayered thin films via the layer-by-layer assembly technique. Herein, polymer chains have been replaced with positively charged inorganic gibbsite nanoplatelets (GN) to form hybrid "nanoparticle-only" composite films. A combination of atomic force microscopy and neutron reflectivity experiments was exploited to investigate the growth and structure of the films. Data show that the growth and density of GN/CNC films can be tuned over a wide range during preparation by varying the ionic strength in the CNC suspension and the film drying protocol. Specifically, thin and dense multilayered films or very thick, more porous mixed slabs, as well as intermediate internal structures, could be obtained in a predictable manner. The influence of key physicochemical parameters on the multilayer film buildup was elucidated and the film architecture was linked to the dominating interaction forces between the components. The degree of structural control over these hybrid nanoparticle-only films is much higher than that reported for CNC/polymer films, which offers new properties and potential applications as separation membranes or flame retardant coatings.
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http://dx.doi.org/10.1021/acs.langmuir.7b02352DOI Listing
August 2017

Dynamically Controlled Iridescence of Cholesteric Cellulose Nanocrystal Suspensions Using Electric Fields.

Adv Mater 2017 Mar 23;29(11). Epub 2017 Jan 23.

Centre de Recherche sur les Macromolécules Végétales (CERMAV-CNRS), Université Grenoble Alpes, F-38000, Grenoble, France.

Cellulose nanocrystal suspensions in apolar solvent spontaneously form iridescent liquid-crystalline phases but the control of their macroscopic order is usually poor. The use of electric fields can provide control on the cholesteric orientation and its periodicity, allowing macroscopic sample homogeneity and dynamical tuning of their iridescent hues, and is demonstrated here.
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http://dx.doi.org/10.1002/adma.201606208DOI Listing
March 2017

The Reductive Dehydration of Cellulose by Solid/Gas Reaction with TiCl at Low Temperature: A Cheap, Simple, and Green Process for Preparing Anatase Nanoplates and TiO /C Composites.

Chemistry 2016 Nov 13;22(48):17262-17268. Epub 2016 Oct 13.

Institut Charles Gerhardt Montpellier UMR 5253 CNRS-UM-ENSCM, CMOS, University of Montpellier, Place E. Bataillon, 34095, Montpellier Cedex 5, France.

Metal oxides and metal oxide/carbon composites are entering the development of new technologies and should therefore to be prepared by sustainable chemistry processes. Therefore, a new aspect of the reactivity of cellulose is presented through its solid/gas reaction with vapour of titanium(IV) chloride in anhydrous conditions at low temperature (80 °C). This reaction leads to two transformations both for cellulose and titanium(IV) chloride. A reductive dehydration of cellulose is seen at the lowest temperature ever reported and results in the formation of a carbonaceous fibrous solid as the only carbon-containing product. Simultaneously, the in situ generation of water leads to the formation of titanium dioxide with an unexpected nanoplate morphology (ca. 50 nm thickness) and a high photocatalytic activity. We present the evidence showing the evolution of the cellulose and the TiO nanostructure formation, along with its photocatalytic activity. This low-temperature process avoids any other reagents and is among the greenest processes for the preparation of anatase and also for TiO /carbon composites. The anisotropic morphology of TiO questions the role of the cellulose on the growing process of these nanoparticles.
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http://dx.doi.org/10.1002/chem.201603086DOI Listing
November 2016

Adjustment of the Chiral Nematic Phase Properties of Cellulose Nanocrystals by Polymer Grafting.

Langmuir 2016 05 19;32(17):4305-12. Epub 2016 Apr 19.

Université Grenoble Alpes , Centre de Recherches sur les Macromolécules Végétales (CERMAV), F-38000 Grenoble, France.

The self-organization properties of sulfated cellulose nanocrystals, TEMPO-oxidized cellulose nanocrystals and polymer-decorated cellulose nanocrystals suspensions in water were investigated and compared. Polarized light optical microscopy observations showed that these three systems phase separated to form a lower anisotropic chiral-nematic phase and an upper isotropic phase following a nucleation and growth mechanism, proving that surface-grafted polymer chains did not inhibit the self-organization properties of CNCs. The phase diagrams and pitch of the suspensions were shown to strongly depend on the surface chemistry of the nanoparticles and the nature of the interacting forces. Especially, the entropic repulsion contribution of the polymer chains to the overall interactions forces resulted in a decrease of the critical volume fractions due to an increase of the effective diameter of the rods. Additionally, above a cellulose volume fraction of 3.5% v/v, the pitch was significantly smaller for polymer-decorated CNC suspensions than for sulfated as-prepared CNC ones, revealing stronger chiral interactions with the surface-grafted chains. In all cases, the addition of small quantities of monovalent salt induced an increase of the critical concentrations, but values for polymer-decorated CNCs were always the smallest ones due to entropic repulsion forces. Overall, results show that polymer grafting provides more tunability to the chiral-nematic phase properties of CNCs, including an enhanced expression of the chirality.
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http://dx.doi.org/10.1021/acs.langmuir.6b00690DOI Listing
May 2016

Probing the Functions of Carbohydrate Binding Modules in the CBEL Protein from the Oomycete Phytophthora parasitica.

PLoS One 2015 21;10(9):e0137481. Epub 2015 Sep 21.

Université de Toulouse; INSA, UPS, INP, LISBP, 135 Avenue de Rangueil, F-31077 Toulouse, France; CNRS, UMR5504, F-31400 Toulouse, France; INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France.

Oomycetes are microorganisms that are distantly related to true fungi and many members of this phylum are major plant pathogens. Oomycetes express proteins that are able to interact with plant cell wall polysaccharides, such as cellulose. This interaction is thought to be mediated by carbohydrate-binding modules that are classified into CBM family 1 in the CAZy database. In this study, the two CBMs (1-1 and 1-2) that form part of the cell wall glycoprotein, CBEL, from Phytophthora parasitica have been submitted to detailed characterization, first to better quantify their interaction with cellulose and second to determine whether these CBMs can be useful for biotechnological applications, such as biomass hydrolysis. A variety of biophysical techniques were used to study the interaction of the CBMs with various substrates and the data obtained indicate that CBEL's CBM1-1 exhibits much greater cellulose binding ability than CBM1-2. Engineering of the family 11 xylanase from Talaromyces versatilis (TvXynB), an enzyme that naturally bears a fungal family 1 CBM, has produced two variants. The first one lacks its native CBM, whereas the second contains the CBEL CBM1-1. The study of these enzymes has revealed that wild type TvXynB binds to cellulose, via its CBM1, and that the substitution of its CBM by oomycetal CBM1-1 does not affect its activity on wheat straw. However, intriguingly the addition of CBEL during the hydrolysis of wheat straw actually potentiates the action of TvXynB variant lacking a CBM1. This suggests that the potentiating effect of CBM1-1 might not require the formation of a covalent linkage to TvXynB.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0137481PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4577117PMC
May 2016

Conversion of Nanocellulose Aerogel into TiO2 and [email protected] Nano-thorns by Direct Anhydrous Mineralization with TiCl4. Evaluation of Electrochemical Properties in Li Batteries.

ACS Appl Mater Interfaces 2015 Jul 2;7(27):14584-92. Epub 2015 Jul 2.

†Institut Charles Gerhardt Montpellier UMR 5253 - CMOS Pl. E. BATAILLON 34090 Montpellier, France.

Nanostructured TiO2 and [email protected] nanocomposites were prepared by an original process combining biotemplating and mineralization of aerogels of nanofibrillated cellulose (NFC). A direct one step treatment of NFC with TiCl4 in strictly anhydrous conditions allows TiO2 formation at the outermost part of the nanofibrils while preserving their shape and size. Such [email protected] composites can be transformed into TiO2 nanotubes (TiO2-NT) by calcination in air at 600 and 900 °C, or into [email protected] nanocomposites by pyrolysis in argon at 600 and 900 °C. Detailed characterization of these materials is reported here, along with an assessment of their performance as negative electrode materials for Li-ion batteries.
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http://dx.doi.org/10.1021/acsami.5b00299DOI Listing
July 2015

Preparation of cellulose II and IIII films by allomorphic conversion of bacterial cellulose I pellicles.

Mater Sci Eng C Mater Biol Appl 2015 Jun 23;51:167-73. Epub 2015 Feb 23.

Université Grenoble Alpes, Centre de Recherches sur les Macromolécules Végétales (CERMAV), F-38000 Grenoble, France; CNRS, CERMAV, F-38000 Grenoble, France.

The structural changes resulting from the conversion of native cellulose I (Cel I) into allomorphs II (Cel II) and IIII (Cel IIII) have usually been studied using powder samples from plant or algal cellulose. In this work, the conversion of Cel I into Cel II and Cel IIII was performed on bacterial cellulose films without any mechanical disruption. The surface texture of the films was observed by atomic force microscopy (AFM) and the morphology of the constituting cellulose ribbons, by transmission electron microscopy (TEM). The structural changes were characterized using solid-state NMR spectroscopy as well as X-ray and electron diffraction. The allomorphic change into Cel II and Cel IIII resulted in films with different crystallinity, roughness and hydrophobic/hydrophilicity surface and the films remained intact during all process of allomorphic conversion.
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http://dx.doi.org/10.1016/j.msec.2015.02.025DOI Listing
June 2015

Aphanomyces euteiches cell wall fractions containing novel glucan-chitosaccharides induce defense genes and nuclear calcium oscillations in the plant host Medicago truncatula.

PLoS One 2013 23;8(9):e75039. Epub 2013 Sep 23.

Laboratoire de Recherche en Sciences Végétales (UMR 5546), Université de Toulouse (UPS), Castanet-Tolosan, France ; UMR5546, CNRS, Castanet-Tolosan, France.

N-acetylglucosamine-based saccharides (chitosaccharides) are components of microbial cell walls and act as molecular signals during host-microbe interactions. In the legume plant Medicago truncatula, the perception of lipochitooligosaccharide signals produced by symbiotic rhizobia and arbuscular mycorrhizal fungi involves the Nod Factor Perception (NFP) lysin motif receptor-like protein and leads to the activation of the so-called common symbiotic pathway. In rice and Arabidopsis, lysin motif receptors are involved in the perception of chitooligosaccharides released by pathogenic fungi, resulting in the activation of plant immunity. Here we report the structural characterization of atypical chitosaccharides from the oomycete pathogen Aphanomyces euteiches, and their biological activity on the host Medicago truncatula. Using a combination of biochemical and biophysical approaches, we show that these chitosaccharides are linked to β-1,6-glucans, and contain a β-(1,3;1,4)-glucan backbone whose β-1,3-linked glucose units are substituted on their C-6 carbon by either glucose or N-acetylglucosamine residues. This is the first description of this type of structural motif in eukaryotic cell walls. Glucan-chitosaccharide fractions of A. euteiches induced the expression of defense marker genes in Medicago truncatula seedlings independently from the presence of a functional Nod Factor Perception protein. Furthermore, one of the glucan-chitosaccharide fractions elicited calcium oscillations in the nucleus of root cells. In contrast to the asymmetric oscillatory calcium spiking induced by symbiotic lipochitooligosaccharides, this response depends neither on the Nod Factor Perception protein nor on the common symbiotic pathway. These findings open new perspectives in oomycete cell wall biology and elicitor recognition and signaling in legumes.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0075039PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3781040PMC
August 2014

Versatile gas-phase reactions for surface to bulk esterification of cellulose microfibrils aerogels.

Biomacromolecules 2013 Sep 19;14(9):3246-55. Epub 2013 Aug 19.

Centre de Recherches sur les Macromolécules Végétales, CERMAV-CNRS, BP 53, F-38041 Grenoble Cedex 9, France.

Aqueous suspensions of microfibrillated cellulose obtained by a high pressure homogenization process were freeze-dried after solvent exchange into tert-butanol. The resulting aerogels, which displayed a remarkable open morphology with a surface area reaching 100 m(2)/g, were subjected to a gas-phase esterification with palmitoyl chloride. Under these conditions, variations of the reaction temperature from 100 to 200 °C, of the reaction time from 0.5 to 2 h, and of the initial quantity of reagent, led to the preparation of a library of cellulose palmitates with DS varying from zero to 2.36. These products were characterized by gravimetry, FTIR, and (13)C solid-state NMR spectroscopy. Of special interest were the cellulose palmitate samples of low DS in the range of 0.1-0.4, which corresponded to hydrophobic cellulose microfibrils exclusively esterified at their surface while keeping intact their inner structure.
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http://dx.doi.org/10.1021/bm400864zDOI Listing
September 2013

Crystal transition between hydrate and anhydrous (1→3)-β-D-xylan from Penicillus dumetosus.

Carbohydr Polym 2013 Aug 23;97(1):105-10. Epub 2013 Apr 23.

Department of Biomaterials Science, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan.

The crystal structures of hydrated and anhydrous (1→3)-β-d-xylan and the crystal transition between them were investigated. Highly crystalline samples of (1→3)-β-d-xylan were prepared from a siphoneous green alga, Penicillus dumetosus. The crystal structure was analyzed using synchrotron X-ray diffraction and solid-state (13)C NMR spectroscopy. The hydrated form was converted to the anhydrous form with contraction in both the a-axis and c-axis directions, and the crystallinity decreased considerably at the same time. The crystal transition between hydrated and anhydrous (1→3)-β-d-xylan was monitored using synchrotron X-ray diffraction under controlled relative humidity. The transition took place at certain transition points, and was accompanied by a large hysteresis. From the difference in the weight and unit-cell volume at the transition points, the number of water molecules in the hydrated form was estimated as one per xylose residue.
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http://dx.doi.org/10.1016/j.carbpol.2013.04.035DOI Listing
August 2013

SANS measurements of semiflexible xyloglucan polysaccharide chains in water reveal their self-avoiding statistics.

Biomacromolecules 2011 Sep 22;12(9):3330-6. Epub 2011 Aug 22.

Laboratoire Léon Brillouin, CEA Saclay, 91191 Gif sur Yvette Cedex, France.

We explored the behavior and the characteristics of xyloglucan polysaccharide chains extracted from tamarind seeds in aqueous media. The initial solubilization is achieved by using a 0.01 M NaOH solution. The absence of compact aggregates in the solution and the average molecular mass of the individual chains were unambiguously demonstrated by size exclusion chromatography with multi-angle light scattering detection. The composition and the stability of the solution were quantitatively checked over weeks by using liquid state nuclear magnetic resonance with DMSO as internal standard. The conformational characteristics of the chains were measured using nondestructive small-angle neutron scattering (SANS). The unambiguous determination of the Flory exponent (ν = 0.588) by SANS enabled us to directly prove that xyloglucan chains in water behave like semiflexible worm-like chains with excluded volume statistics (good solvent), contrary to most of the neutral water-soluble polymer chains that rather exhibit Gaussian statistics (θ-solvent). In addition to the Flory exponent, the persistence length l(p) and the cross section of the chains were also determined by SANS with utmost precision, with values of 80 and of 7 Å, respectively, which provides a complete description of the conformational characteristics of XG chains at all relevant length scales.
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http://dx.doi.org/10.1021/bm200881xDOI Listing
September 2011

Preparation by grafting onto, characterization, and properties of thermally responsive polymer-decorated cellulose nanocrystals.

Biomacromolecules 2010 Dec 8;11(12):3652-9. Epub 2010 Nov 8.

Centre de Recherches sur les Macromolécules Végétales (CERMAV-CNRS), BP 53, 38041 Grenoble Cedex 9, France.

The grafting of thermosensitive amine-terminated statistical polymers onto the surface of cellulose nanocrystals (CNCs) was achieved by a peptidic coupling reaction, leading to unusual properties like colloidal stability at high ionic strength, surface activity, and thermoreversible aggregation. We have used a large variety of experimental techniques to investigate the properties of the polymer-decorated CNCs at different length-scales and as a function of the different reaction parameters. A high grafting density could be obtained when the reaction was performed in DMF rather than water. Infrared and solid-state NMR spectroscopy data unambiguously demonstrated the covalent character of the bonding between the CNCs and the macromolecules, whereas TEM images showed a preserved individualized character of the modified objects. Dynamic light scattering and zeta potential measurements were also consistent with individual nanocrystals decorated by a shell of polymer chains. Surface tension measurements revealed that CNCs became surface-active after the grafting of thermosensitive amines. Decorated CNCs were also stable against high electrolyte concentrations. A thermoreversible aggregation was also observed, which paves the way for the design of stimuli-responsive biobased nanocomposite materials.
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http://dx.doi.org/10.1021/bm101106cDOI Listing
December 2010

Self-assembling and chiral nematic properties of organophilic cellulose nanocrystals.

J Phys Chem B 2009 Aug;113(32):11069-75

Centre de Recherches sur les Macromolécules Végétales-CNRS, F-38041 Grenoble Cedex 9, France.

Cotton cellulose nanocrystals with different aspect ratios have been dispersed in cyclohexane as a model apolar solvent, using surfactants. Above a critical concentration, which was higher than that in water, the suspensions spontaneously phase separated into a chiral nematic mesophase. According to Onsager's theory, the phase separation is controlled by the aspect ratio, while being influenced by the polydispersity. The sample with the highest aspect ratio did not show any phase separation but instead shows an anisotropic gel phase at high concentration. Experimental critical concentrations were found to be much lower than the predicted ones, revealing an attractive interaction between the rods. Chiral nematic pitches as small as 2 mum were found to be much lower than those measured in water, due to stronger chiral interactions in the apolar medium.
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http://dx.doi.org/10.1021/jp900122tDOI Listing
August 2009

Gas-phase surface esterification of cellulose microfibrils and whiskers.

Biomacromolecules 2009 Aug;10(8):2144-51

Centre de Recherches sur les Macromolecules Vegetales-CNRS, affiliated with the Universite Joseph Fourier and member of the Institut de Chimie Moleculaire de Grenoble, F-38041 Grenoble Cedex 9, France.

A new and highly efficient synthetic method has been developed for the surface esterification of model cellulosic substrates of high crystallinity and accessibility, namely, freeze-dried tunicin whiskers and bacterial cellulose microfibrils dried by the critical point method. The reaction, which is based on the gas-phase action of palmitoyl chloride, was monitored by solid-state CP-MAS (13)C NMR. It was found that the grafting density not only depended on the experimental conditions, but also on the nature and conditioning of the cellulose samples. The structural and morphological modifications of the substrates at various degrees of grafting were revealed by scanning electron microscopy and X-ray diffraction analysis. These characterizations indicated that the esterification proceeded from the surface of the substrate to their crystalline core. Hence, for moderate degree of substitution, the surface was fully grafted whereas the cellulose core remained unmodified and the original fibrous morphology maintained. An almost total esterification could be achieved under certain conditions, leading to highly substituted cellulose esters, presenting characteristic X-ray diffraction patterns.
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http://dx.doi.org/10.1021/bm900319kDOI Listing
August 2009

Individualization of nano-sized plant cellulose fibrils by direct surface carboxylation using TEMPO catalyst under neutral conditions.

Biomacromolecules 2009 Jul 15;10(7):1992-6. Epub 2009 May 15.

Department of Biomaterials Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan.

A new catalytic oxidation using 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) and NaClO is applied to hardwood cellulose in water at 60 °C and pH 6.8 with NaClO(2) used as a primary oxidant. The oxidized celluloses with carboxylate content of approximately 0.8 mmol/g were convertible to highly crystalline and individual fibrils 5 nm in width and at least 2 μm in length by disintegration in water. The oxidized celluloses had no aldehyde groups, and high degrees of polymerization of more than 900. Solid-state (13)C NMR and X-ray analyses revealed that the C6 carboxylate groups formed are selectively present on the crystalline fibril surfaces at high densities. Films prepared from the dispersions were transparent and flexible, and exhibited a high tensile strength of 312 MPa even at a low density of 1.47 g/cm(3).
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http://dx.doi.org/10.1021/bm900414tDOI Listing
July 2009

X-ray crystallographic, scanning microprobe X-ray diffraction, and cross-polarized/magic angle spinning 13C NMR studies of the structure of cellulose III(II).

Biomacromolecules 2009 Feb;10(2):302-9

Department of Biomaterials Science, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan.

The X-ray crystallographic structure of cellulose III(II) is characterized by disorder; the unit cell (space group P2(1); a = 4.45 A, b = 7.64 A, c = 10.36 A, alpha = beta = 90 degrees, gamma = 106.96 degrees) is occupied by one chain that is the average of statistically disordered antiparallel chains. 13C CP/MAS NMR studies reveal the presence of three distinct molecular conformations that can be interpreted as a mixture of two different crystal forms, one equivalent to cellulose III(I), and another with two independent glucosyl conformations in the asymmetric unit. Both X-ray crystallographic and 13C NMR spectroscopic results are consistent with an aggregated microdomain structure for cellulose III(II). This structure can be generated from a new crystal form (space group P2(1); a = 4.45 A, b = 14.64 A, c = 10.36 A, alpha = beta = 90 degrees, gamma = 90.05 degrees; two crystallographically independent and antiparallel chains; gt hydroxymethyl groups) by multiple dislocation defects. These defects produce microdomains of the new crystal form and cellulose III(I) that scanning microprobe diffraction studies show are distributed consistently through the cellulose III(II) fiber.
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http://dx.doi.org/10.1021/bm8010227DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2771106PMC
February 2009

Non-electrostatic building of biomimetic cellulose-xyloglucan multilayers.

Langmuir 2009 Apr;25(7):3920-3

Centre de Recherche sur les Macromolecules Végétales (CERMAV-CNRS), BP 53, 38041 Grenoble Cedex 9, France.

Layer-by-layer assembly was used to build thin films, consisting of multiple layers alternating cellulose nanocrystals and xyloglucan, benefiting from the strong non-electrostatic cellulose-xyloglucan interaction. Data from atomic force microscopy and neutron reflectivity showed that these well-defined films exhibited a thickness increasing linearly with the number of layers, without increase in surface roughness. These "green" nanocomposite films, reminiscent of plant cell wall, are composed of a regular stack of single layers of cellulose nanocrystals separated by very thin xyloglucan spacers. Such architecture differs from the one formed by cellulose/polycations multilayers, where the cellulose phase itself consists of a double layer.
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http://dx.doi.org/10.1021/la802801qDOI Listing
April 2009

Cell wall chitosaccharides are essential components and exposed patterns of the phytopathogenic oomycete Aphanomyces euteiches.

Eukaryot Cell 2008 Nov 19;7(11):1980-93. Epub 2008 Sep 19.

UMR 5546, CNRS-Université Paul-Sabatier, 24 Chemin de Borde-Rouge, BP 42617, Auzeville, F-31326 Castanet-Tolosan, France.

Chitin is an essential component of fungal cell walls, where it forms a crystalline scaffold, and chitooligosaccharides derived from it are signaling molecules recognized by the hosts of pathogenic fungi. Oomycetes are cellulosic fungus-like microorganisms which most often lack chitin in their cell walls. Here we present the first study of the cell wall of the oomycete Aphanomyces euteiches, a major parasite of legume plants. Biochemical analyses demonstrated the presence of ca. 10% N-acetyl-D-glucosamine (GlcNAc) in the cell wall. Further characterization of the GlcNAc-containing material revealed that it corresponds to noncrystalline chitosaccharides associated with glucans, rather than to chitin per se. Two putative chitin synthase (CHS) genes were identified by data mining of an A. euteiches expressed sequence tag collection and Southern blot analysis, and full-length cDNA sequences of both genes were obtained. Phylogeny analysis indicated that oomycete CHS diversification occurred before the divergence of the major oomycete lineages. Remarkably, lectin labeling showed that the Aphanomyces euteiches chitosaccharides are exposed at the cell wall surface, and study of the effect of the CHS inhibitor nikkomycin Z demonstrated that they are involved in cell wall function. These data open new perspectives for the development of antioomycete drugs and further studies of the molecular mechanisms involved in the recognition of pathogenic oomycetes by the host plants.
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http://dx.doi.org/10.1128/EC.00091-08DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2583540PMC
November 2008

Structural details of cellulose nanocrystals/polyelectrolytes multilayers probed by neutron reflectivity and AFM.

Langmuir 2008 Apr 7;24(7):3452-8. Epub 2008 Mar 7.

Centre de Recherche sur les Macromolécules Végétales (CERMAV-CNRS), BP 53, 38041 Grenoble Cedex 9, France.

Neutron reflectivity measurements and AFM observations were used as complementary techniques to investigate multilayered films consisting of alternating sheets of rigid cellulose nanocrystals and flexible poly(allylamine hydrochloride) (PAH) prepared by the layer-by-layer assembly technique. Both techniques showed that smooth films with a high load of cellulose could be obtained. After deposition, the cellulose component occurred as a double layer with different densities: 50% and 25% for the lower and upper layer, respectively. A linear growth of the multilayer and the presence of a Bragg peak on neutron reflectivity curves indicated the formation of a well-ordered structure resulting from entropy-driven assembly and smoothening effect of the flexible PAH macromolecules. The possible alignment of the nanocrystals when anisotropic suspensions were used is also shown and opens the route to an improved control of the architecture of these multilayers.
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http://dx.doi.org/10.1021/la703045fDOI Listing
April 2008
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