Publications by authors named "Fabio Ziarelli"

62 Publications

Production and properties of non-cytotoxic pyomelanin by laccase and comparison to bacterial and synthetic pigments.

Sci Rep 2021 04 20;11(1):8538. Epub 2021 Apr 20.

Mediterranean Institute of Oceanology (MIO), Aix-Marseille Université, 163 avenue de Luminy, 13288, Marseille Cedex 9, France.

Pyomelanin is a polymer of homogentisic acid synthesized by microorganisms. This work aimed to develop a production process and evaluate the quality of the pigment. Three procedures have been elaborated and optimized, (1) an HGA-Mn chemical autoxidation (Pyo yield 0.317 g/g substrate), (2) an induced bacterial culture of Halomonas titanicae through the 4-hydroxyphenylacetic acid-1-hydroxylase route (Pyo, 0.55 g/L), and (3) a process using a recombinant laccase extract with the highest level produced (Pyo, 1.25 g/g substrate) and all the criteria for a large-scale prototype. The chemical structures had been investigated by C solid-state NMR (CP-MAS) and FTIR. C-C bindings predominated in the three polymers, C-O-C (ether) linkages being absent, proposing mainly C-C (α-bindings) and C-C (β-bindings) configurations. This work highlighted a biological decarboxylation by the laccase or bacterial oxidase(s), leading to the partly formation of gentisyl alcohol and gentisaldehyde that are integral parts of the polymer. By comparison, Pyo exhibited an M of 5,400 Da, was hyperthermostable, non-cytotoxic even after irradiation, scavenged ROS induced by keratinocytes, and had a highly DPPH-antioxidant and Fe-reducing activity. As a representative pigment of living cells and an available standard, Pyo might also be useful for applications in extreme conditions and skin protection.
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http://dx.doi.org/10.1038/s41598-021-87328-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8058095PMC
April 2021

Monitoring Crystallization Processes in Confined Porous Materials by Dynamic Nuclear Polarization Solid-State Nuclear Magnetic Resonance.

J Am Chem Soc 2021 04 15;143(16):6095-6103. Epub 2021 Apr 15.

Aix Marseille Univ, CNRS, ICR, 13397 Marseille, France.

Establishing mechanistic understanding of crystallization processes at the molecular level is challenging, as it requires both the detection of transient solid phases and monitoring the evolution of both liquid and solid phases as a function of time. Here, we demonstrate the application of dynamic nuclear polarization (DNP) enhanced NMR spectroscopy to study crystallization under nanoscopic confinement, revealing a viable approach to interrogate different stages of crystallization processes. We focus on crystallization of glycine within the nanometric pores (7-8 nm) of a tailored mesoporous SBA-15 silica material with wall-embedded TEMPO radicals. The results show that the early stages of crystallization, characterized by the transition from the solution phase to the first crystalline phase, are straightforwardly observed using this experimental strategy. Importantly, the NMR sensitivity enhancement provided by DNP allows the detection of intermediate phases that would not be observable using standard solid-state NMR experiments. Our results also show that the metastable β polymorph of glycine, which has only transient existence under bulk crystallization conditions, remains trapped within the pores of the mesoporous SBA-15 silica material for more than 200 days.
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http://dx.doi.org/10.1021/jacs.0c12982DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8154530PMC
April 2021

Poly(β-cyclodextrin)-Activated Carbon Gel Composites for Removal of Pesticides from Water.

Molecules 2021 Mar 6;26(5). Epub 2021 Mar 6.

Coimbra Chemistry Centre, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal.

Pesticides are widely used in agriculture to increase and protect crop production. A substantial percentage of the active substances applied is retained in the soil or flows into water courses, constituting a very relevant environmental problem. There are several methods for the removal of pesticides from soils and water; however, their efficiency is still a challenge. An alternative to current methods relies on the use of effective adsorbents in removing pesticides which are, simultaneously, capable of releasing pesticides into the soil when needed. This reduces costs related to their application and waste treatments and, thus, overall environmental costs. In this paper, we describe the synthesis and preparation of activated carbon-containing poly(β-cyclodextrin) composites. The composites were characterized by different techniques and their ability to absorb pesticides was assessed by using two active substances: cymoxanil and imidacloprid. Composites with 5 and 10 wt% of activated carbon showed very good stability, high removal efficiencies (>75%) and pesticide sorption capacity up to ca. 50 mg g. The effect of additives (NaCl and urea) was also evaluated. The composites were able to release around 30% of the initial sorbed amount of pesticide without losing the capacity to keep the maximum removal efficiency in sorption/desorption cycles.
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http://dx.doi.org/10.3390/molecules26051426DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7962014PMC
March 2021

Solvent suppression in solid-state DNP NMR using Electronic Mixing-Mediated Annihilation (EMMA).

Magn Reson Chem 2020 11 4;58(11):1076-1081. Epub 2020 Feb 4.

Aix Marseille Univ, CNRS, ICR, Marseille, France.

We show here that the Electronic Mixing-Mediated Annihilation (EMMA) method, previously reported for the suppression of background signals in solid-state nuclear magnetic resonance spectra, can be successfully applied to remove the solvent signals observed in the case of nuclear magnetic resonance spectra obtained with dynamic nuclear polarization. The methodology presented here is applied to two standard sample preparation methods for dynamic nuclear polarization, namely, glass forming and incipient wetness impregnation. It is demonstrated that the Electronic Mixing-Mediated Annihilation method is complementary to the different methods for solvent suppression based on relaxation filters and that it can be used to preserve the quantitative information that might be present in the pristine spectra.
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http://dx.doi.org/10.1002/mrc.5001DOI Listing
November 2020

A Karplus Equation for the Conformational Analysis of Organic Molecular Crystals.

Angew Chem Int Ed Engl 2019 11 4;58(45):16047-16051. Epub 2019 Sep 4.

Aix Marseille Univ, CNRS, ICR UMR 7273, Marseille, France.

Vicinal scalar couplings ( J) are extensively used for the conformational analysis of organic compounds in the liquid state through empirical Karplus equations. In contrast, there are no examples of such use for the structural investigation of solids. With the support of first principles calculations, we demonstrate here that C- C J coupling constants ( J ) measured on a series of isotopically enriched solid amino acids and sugars can be related to dihedral angles by a simple Karplus-like relationship, and we provide a parameterized Karplus function for the conformational analysis of organic molecular crystals. Under the experimental conditions discussed, torsional angles can be estimated from the experimental J values with an accuracy of 10° using this function. These results open new perspectives towards the use of J as a new analytical tool that could considerably simplify structure determination of functional organic solids.
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http://dx.doi.org/10.1002/anie.201906359DOI Listing
November 2019

Pre-treatment of a sugarcane bagasse-based substrate prior to saccharification: Effect of coffee pulp and urea on laccase and cellulase activities of Pycnoporus sanguineus.

J Environ Manage 2019 Jun 19;239:178-186. Epub 2019 Mar 19.

Aix Marseille Université, Avignon Université, CNRS, IRD, IMBE, Marseille, France. Electronic address:

Production of second-generation bioethanol uses lignocellulose from agricultural by-products such as sugarcane bagasse (SCB). A lignocellulose pre-treatment is required to degrade lignin, ensuring further efficient saccharification. Two experimental designs were set up to define culture conditions of Pycnoporus sanguineus in mesocosms to increase laccase activities and thus delignification. The first experimental design tested the effect of phenolic complementation (via coffee pulp) and the use of urea as a simple nitrogen source and the second defined more precisely the percentages of coffee pulp and urea to enhance delignification. The responses measured were: lignocellulolytic activities, laccase isoform profiles by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and the chemical transformation of the substrate using solid-state NMR of 13C. Adding 10% of coffee pulp increased laccase activities and fungal biomass (32.5% and 16% respectively), enhanced two constitutive isoforms (R 0.23 and 0.27), induced a new isoform (R 0.19) and led to a decrease in total aromatics. However, higher concentrations of coffee pulp (25%) decreased laccase and cellulase activities but no decrease in aromaticity was observed, potentially due to the toxic effect of phenols from coffee pulp. Moreover, laccase production was still inhibited even for lower concentrations of urea (0-5%). Our findings revealed that an agricultural by-product like coffee pulp can enhance laccase activity -though to a threshold- and that urea limited this process, indicating that other N-sources should be tested for the biological delignification of SCB.
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http://dx.doi.org/10.1016/j.jenvman.2019.03.033DOI Listing
June 2019

A Strategy for Probing the Evolution of Crystallization Processes by Low-Temperature Solid-State NMR and Dynamic Nuclear Polarization.

J Phys Chem Lett 2019 Apr 18;10(7):1505-1510. Epub 2019 Mar 18.

Aix Marseille Univ, CNRS, ICR , 13397 Marseille , France.

Crystallization plays an important role in many areas, and to derive a fundamental understanding of crystallization processes, it is essential to understand the sequence of solid phases produced as a function of time. Here, we introduce a new NMR strategy for studying the time evolution of crystallization processes, in which the crystallizing system is quenched rapidly to low temperature at specific time points during crystallization. The crystallized phase present within the resultant "frozen solution" may be investigated in detail using a range of sophisticated NMR techniques. The low temperatures involved allow dynamic nuclear polarization (DNP) to be exploited to enhance the signal intensity in the solid-state NMR measurements, which is advantageous for detection and structural characterization of transient forms that are present only in small quantities. This work opens up the prospect of studying the very early stages of crystallization, at which the amount of solid phase present is intrinsically low.
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http://dx.doi.org/10.1021/acs.jpclett.9b00306DOI Listing
April 2019

Brute-force solvent suppression for DNP studies of powders at natural isotopic abundance.

Solid State Nucl Magn Reson 2019 07 23;99:15-19. Epub 2019 Feb 23.

Aix Marseille Univ, CNRS, ICR, Marseille, France. Electronic address:

A method based on highly concentrated radical solutions is investigated for the suppression of the NMR signals arising from solvents that are usually used for dynamic nuclear polarization experiments. The presented method is suitable in the case of powders, which are impregnated with a radical-containing solution. It is also demonstrated that the intensity and the resolution of the signals due to the sample of interest is not affected by the high concentration of radicals. The method proposed here is therefore valuable when sensitivity is of the utmost importance, namely samples at natural isotopic abundance.
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http://dx.doi.org/10.1016/j.ssnmr.2019.02.002DOI Listing
July 2019

Reducing the computational cost of NMR crystallography of organic powders at natural isotopic abundance with the help of C- C dipolar couplings.

Magn Reson Chem 2019 05 11;57(5):256-264. Epub 2019 Mar 11.

Aix Marseille Univ, CNRS, ICR, Marseille, France.

Structure determination of functional organic compounds remains a formidable challenge when the sample exists as a powder. Nuclear magnetic resonance crystallography approaches based on the comparison of experimental and Density Functional Theory (DFT)-computed H chemical shifts have already demonstrated great potential for structure determination of organic powders, but limitations still persist. In this study, we discuss the possibility of using C- C dipolar couplings quantified on powdered theophylline at natural isotopic abundance with the help of dynamic nuclear polarization, to realize a DFT-free, rapid screening of a pool of structures predicted by ab initio random structure search. We show that although C- C dipolar couplings can identify structures possessing long range structural motifs and unit cell parameters close to those of the true structure, it must be complemented with other data to recover information about the presence and the chemical nature of the supramolecular interactions.
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http://dx.doi.org/10.1002/mrc.4848DOI Listing
May 2019

Insights into the Crystallization and Structural Evolution of Glycine Dihydrate by In Situ Solid-State NMR Spectroscopy.

Angew Chem Int Ed Engl 2018 05 8;57(22):6619-6623. Epub 2018 May 8.

School of Chemistry, Cardiff University, Park Place, Cardiff, Wales, CF10 3AT, UK.

In situ solid-state NMR spectroscopy is exploited to monitor the structural evolution of a glycine/water glass phase formed on flash cooling an aqueous solution of glycine, with a range of modern solid-state NMR methods applied to elucidate structural properties of the solid phases present. The glycine/water glass is shown to crystallize into an intermediate phase, which then transforms to the β polymorph of glycine. Our in situ NMR results fully corroborate the identity of the intermediate crystalline phase as glycine dihydrate, which was first proposed only very recently.
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http://dx.doi.org/10.1002/anie.201801114DOI Listing
May 2018

Diastereoselective Synthesis of a Dyn[3]arene with Distinct Binding Behaviors toward Linear Biogenic Polyamines.

Org Lett 2018 04 6;20(8):2420-2423. Epub 2018 Apr 6.

Institut de Chimie et Biochimie Moléculaires et Supramoléculaires, UMR 5246 CNRS - Université Claude Bernard Lyon1 - CPE Lyon , 43 Boulevard du 11 Novembre 1918 , Villeurbanne Cedex 69622 , France.

The extension of the family of dyn[ n]arenes toward a three-membered macrocycle is reported. Through a templated approach, a single diastereoisomer of a dyn[3]arene that bears six carboxyl groups could be isolated by precipitation in 59-63% yield and excellent purity (≥95%). A combination of experimental and computational experiments in water at physiological pH revealed that the macrocycle could bind parent biogenic polyamines with a unique diversity of surface-binding modes. Whereas no binding event could be accurately measured with 1,3-diaminopropane, spermidine formed a classical stoichiometric complex with the dyn[3]arene in the millimolar concentration range. On the other hand, the data obtained for spermine could only be attributed to a more complex binding event with the formation of a 2:1 complex at high [host]/[guest] ratios and redistribution toward a 1:1 complex upon further addition of guest.
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http://dx.doi.org/10.1021/acs.orglett.8b00766DOI Listing
April 2018

Dynamic Nuclear Polarization NMR as a new tool to investigate the nature of organic compounds occluded in plant silica particles.

Sci Rep 2017 06 13;7(1):3430. Epub 2017 Jun 13.

Earth System Science, University of California, Irvine, USA.

The determination of the chemical nature of the organic matter associated with phytoliths remains a challenge. This difficulty mainly stems from amounts of organic carbon (C) that are often well below the detection limit of traditional spectroscopic tools. Conventional solid-state C Nuclear Magnetic Resonance (NMR) is widely used to examine the nature and structure of organic molecules, but its inherent low sensitivity prohibits the observation of diluted samples. The recent advent of commercial microwave source in the terahertz range triggered a renewed interest in the Dynamic Nuclear Polarization (DNP) technique to improve the signal to noise ratio of solid-state NMR experiments. With this technique, the C spectrum of a phytolith sample containing 0.1% w/w C was obtained overnight with sufficient quality to permit a semi-quantitative analysis of the organic matter, showing the presence of peptides and carbohydrates as predominant compounds. Considering the natural abundance of the C isotope, this experiment demonstrates that DNP NMR is sufficiently sensitive to observe spin systems present in amounts as low as a few tens of ppm.
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http://dx.doi.org/10.1038/s41598-017-03659-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5469814PMC
June 2017

Additive or non-additive effect of mixing oak in pine stands on soil properties depends on the tree species in Mediterranean forests.

Sci Total Environ 2017 Jul 10;590-591:676-685. Epub 2017 Mar 10.

Institut Méditerranéen de Biodiversité et d'Ecologie marine et continentale, UMR 7263, Aix Marseille Université, Université d'Avignon, CNRS, IRD, Campus l'Etoile, Site de Saint-Jérôme, Avenue escadrille Normandie-Niemen, 13 397 Marseille Cedex 20, France. Electronic address:

This study investigated how oak abundance in pine stands (using relative Oak Basal Area %, OBA%) may modulate soil microbial functioning. Forests were composed of sclerophyllous species i.e. Quercus ilex mixed with Pinus halepensis Miller or of Q. pubescens mixed with P. sylvestris. We used a series of plots with OBA% ranging from 0 to 100% in the two types of stand (n=60) and both OLF and A-horizon compartments were analysed. Relations between OBA% and either soil chemical (C and N contents, quality of organic matter via solid-state NMR, pH, CaCO) or microbial (enzyme activities, basal respiration, biomass and catabolic diversity via BIOLOG) characteristics were described. OBA% increase led to a decrease in the recalcitrant fraction of organic matter (OM) in OLF and promoted microbial growth. Catabolic profiles of microbial communities from A-horizon were significantly modulated in Q. ilex and P. halepensis stand by OBA% and alkyl C to carboxyl C ratio (characteristic of cutin from Q. ilex tissues) and in Q. pubescens and P. sylvestris stands, by OBA% and pH. In A-horizon under Q. ilex and P. halepensis stands, linear regressions were found between catabolic diversity, microbial biomass and OBA% suggesting an additive effect. Conversely, in A-horizon Q. pubescens and P. sylvestris stands, the relationship between OBA% and either cellulase activities, polysaccharides or ammonium contents, suggested a non-additive effect of Q. pubescens and P. sylvestris, enhancing mineralization of the OM labile fraction for plots characterized by an OBA% ranging from 40% to 60%. Mixing oak with pine thus favored microbial dynamics in both type of stands though OBA% print varied with tree species and consequently sustainable soil functioning depend strongly on the composition of mixed stands. Our study indeed revealed that, when evaluating the benefits of forest mixed stand on soil microbial functioning and OM turnover, the identity of tree species has to be considered.
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http://dx.doi.org/10.1016/j.scitotenv.2017.03.023DOI Listing
July 2017

Laccase induction by synthetic dyes in Pycnoporus sanguineus and their possible use for sugar cane bagasse delignification.

Appl Microbiol Biotechnol 2017 Feb 14;101(3):1189-1201. Epub 2016 Oct 14.

Instituto de Biotecnología y Ecología Aplicada (INBIOTECA), Universidad Veracruzana, Av. de las Culturas Veracruzanas No. 101, Col. Emiliano Zapata, C.P. 910910, Xalapa, Veracruz, Mexico.

The use of synthetic dyes for laccase induction in vivo has been scarcely explored. We characterized the effect of adding different synthetic dyes to liquid cultures of Pycnoporus sanguineus on laccase production. We found that carminic acid (CA) can induce 722 % and alizarin yellow 317 % more laccase than control does, and they promoted better fungal biomass development in liquid cultures. Aniline blue and crystal violet did not show such positive effect. CA and alizarin yellow were degraded up to 95 % during P. sanguineus culturing (12 days). With this basis, CA was selected as the best inducer and used to evaluate the induction of laccase on solid-state fermentation (SSF), using sugarcane bagasse (SCB) as substrate, in an attempt to reach selective delignification. We found that laccase induction occurred in SSF, and a slight inhibition of cellulase production was observed when CA was added to the substrate; also, a transformation of SCB under SSF was followed by the C cross polarization magic angle spinning (CPMAS) solid-state nuclear magnetic resonance (NMR). Results showed that P. sanguineus can selectively delignify SCB, decreasing aromatic C compounds by 32.67 % in 16 days; O-alkyl C region (polysaccharides) was degraded less than 2 %; delignification values were not correlated with laccase activities. Cellulose-crystallinity index was increased by 27.24 % in absence of CA and 15.94 % when 0.01 mM of CA was added to SCB; this dye also inhibits the production of fungal biomass in SSF (measured as alkyl C gain). We conclude that CA is a good inducer of laccase in liquid media, and that P. sanguineus is a fungus with high potential for biomass delignification.
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http://dx.doi.org/10.1007/s00253-016-7890-0DOI Listing
February 2017

Structure elucidation of a complex CO-based organic framework material by NMR crystallography.

Chem Sci 2016 Jul 22;7(7):4379-4390. Epub 2016 Mar 22.

Institut des Sciences et Ingénierie Chimiques , Ecole Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne , Switzerland.

A three-dimensional structural model of a complex CO-based organic framework made from high molecular weight, self-assembled, flexible and multi-functional oligomeric constituents has been determined by solid-state NMR including DNP-enhanced experiments. The complete assignment of the N, C and H resonances was obtained from a series of two-dimensional through space and through bond correlation experiments. MM-QM calculations were used to generate different model structures for the material which were then evaluated by comparing multiple experimental and calculated NMR parameters. Both NMR and powder X-ray diffraction were evaluated as tools to determine the packing by crystal modelling, and at the level of structural modelling used here PXRD was found not to be a useful complement. The structure determined reveals a highly optimised H-bonding network that explains the unusual selectivity of the self-assembly process which generates the material. The NMR crystallography approach used here should be applicable for the structure determination of other complex solid materials.
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http://dx.doi.org/10.1039/c5sc03810cDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6014084PMC
July 2016

Determining carbon-carbon connectivities in natural abundance organic powders using dipolar couplings.

Chem Commun (Camb) 2016 Jun;52(55):8565-8

Aix-Marseille Université, CNRS, ICR (UMR 7273), 13397 Marseille, France. and Institut Universitaire de France, 75005 Paris, France.

We present a solid-state NMR methodology capable of investigating the carbon skeleton of natural abundance organic powders. The methodology is based on the (13)C-(13)C dipolar coupling interaction and allows carbon-carbon connectivities to be unambiguously established for a wide range of organic solids. This methodology is particularly suitable for disordered solids, such as natural or synthetic macromolecules, which cannot be studied using conventional diffraction or NMR techniques.
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http://dx.doi.org/10.1039/c6cc04202cDOI Listing
June 2016

Silica materials with wall-embedded nitroxides provide efficient polarization matrices for dynamic nuclear polarization NMR.

Chem Commun (Camb) 2016 Apr;52(32):5531-3

Aix-Marseille Université, CNRS, ICR UMR 7273, 13397 Marseille, France.

Hybrid mesoporous silica materials with wall-embedded nitroxides are shown to efficiently polarize impregnated substrates in high-field dynamic nuclear polarization magic-angle spinning solid-state NMR experiments.
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http://dx.doi.org/10.1039/c6cc01809bDOI Listing
April 2016

Fluoride-ion-conducting Polymers: Ionic Conductivity and Fluoride Ion Diffusion Coefficient in Quaternized Polysulfones.

Chemphyschem 2015 Dec 2;16(17):3631-6. Epub 2015 Oct 2.

Aix Marseille University, CNRS, MADIREL (UMR 7246), Campus St Jerome, F-13397, Marseille, France.

We describe the three-step synthesis of a new polymeric fluoride ion conductor based on the fully aromatic polymer polysulfone (PSU). In the first step, PSU is chloromethylated (CM-PSU) using reagents (i.e., stannic chloride, paraformaldehyde, and trimethylchlorosilane) that are less toxic than those used in the standard procedure. In the second step, CM-PSU reacts with a tertiary amine (trimethylamine or 1,4-diazabicyclo[2.2.2]octane) to form quaternary ammonium groups fixed on the PSU backbone and mobile chloride counter-anions. The chloride ions can, in a third step, be exchanged with fluoride ions by immersion of the ionomer in NaF solution. The fluoride ion conductivity reaches 3-5 mS cm(-1) at 25 °C and 5-10 mS cm(-1) at 40 °C. We determined the F(-) diffusion coefficient in these ionomers by pulsed gradient spin-echo (PGSE) high-resolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR) spectroscopy and by impedance spectroscopy using the Nernst-Einstein relation. The diffusion coefficients determined by the two methods are in good agreement, ranging from 2 to 4×10(-10)  m(2)  s(-1) . The porosity and tortuosity of the ionomer membranes can be estimated.
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http://dx.doi.org/10.1002/cphc.201500643DOI Listing
December 2015

Up to 100% Improvement in Dynamic Nuclear Polarization Solid-State NMR Sensitivity Enhancement of Polymers by Removing Oxygen.

Macromol Rapid Commun 2015 Aug 26;36(15):1416-21. Epub 2015 May 26.

Aix-Marseille Université, CNRS, ICR (UMR 7273), 13397, Marseille cedex 20, France.

High-field dynamic nuclear polarization (DNP) has emerged as a powerful technique for improving the sensitivity of solid-state NMR (SSNMR), yielding significant sensitivity enhancements for a variety of samples, including polymers. Overall, depending upon the type of polymer, the molecular weight, and the DNP sample preparation method, sensitivity enhancements between 5 and 40 have been reported. These promising enhancements remain, however, far from the theoretical maximum (>1000). Crucial to the success of DNP SSNMR is the DNP signal enhancement (εDNP ), which is the ratio of the NMR signal intensities with and without DNP. It is shown here that, for polymers exhibiting high affinity toward molecular oxygen (e.g., polystyrene), removing part of the absorbed (paramagnetic) oxygen from the solid-state samples available as powders (instead of dissolved or dispersed in a solvent) increases proton nuclear relaxation times and εDNP, hereby providing up to a two-fold sensitivity increase (i.e., a four-fold reduction in experimental time).
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http://dx.doi.org/10.1002/marc.201500133DOI Listing
August 2015

Surface modification of silk fibroin fibers with poly(methyl methacrylate) and poly(tributylsilyl methacrylate) via RAFT polymerization for marine antifouling applications.

Mater Sci Eng C Mater Biol Appl 2015 Jun 11;51:233-41. Epub 2015 Mar 11.

Université de Toulon, MAPIEM, EA 4323, 83957 La Garde, France.

In this study, silk fibroin surface containing hydroxyl and aminogroups was firstly modified using a polymerizable coupling agent 3-(trimethoxysilyl) propyl methacrylate (MPS), in order to induce vinyl groups onto the fiber surface. The reversible addition-fragmentation chain transfer (RAFT)-mediated polymerization of methyl methacrylate (MMA) and tributylsilyl methacrylate (TBSiMA) through the immobilized vinyl bond on the silk fibroin surface in the presence of 2-cyanoprop-2-yl dithiobenzoate (CPDB) as chain-transfer agent and 2,2'-azobis(isobutyronitrile) (AIBN) as initiator was conducted in toluene solution at 70°C for 24h. The structure and properties of the modified fiber were characterized by Fourier Transform Infrared Spectroscopy, (13)C, (29)Si Nuclear Magnetic Resonance (NMR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), confirming the presence of the coupling molecule and the methacrylate groups onto the silk fibroin fiber surface. Molecular weight distributions were assessed by triple detection size exclusion chromatography (TD-SEC) in order to verify the livingness of the polymerization.
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http://dx.doi.org/10.1016/j.msec.2015.03.006DOI Listing
June 2015

Quantitative structural constraints for organic powders at natural isotopic abundance using dynamic nuclear polarization solid-state NMR spectroscopy.

Angew Chem Int Ed Engl 2015 May 23;54(20):6028-31. Epub 2015 Mar 23.

Aix-Marseille Université, CNRS, ICR (UMR 7273), 13397 Marseille cedex 20 (France).

A straightforward method is reported to quantitatively relate structural constraints based on (13)C-(13)C double-quantum build-up curves obtained by dynamic nuclear polarization (DNP) solid-state NMR to the crystal structure of organic powders at natural isotopic abundance. This method relies on the significant gain in NMR sensitivity provided by DNP (approximately 50-fold, lowering the experimental time from a few years to a few days), and is sensitive to the molecular conformation and crystal packing of the studied powder sample (in this case theophylline). This method allows trial crystal structures to be rapidly and effectively discriminated, and paves the way to three-dimensional structure elucidation of powders through combination with powder X-ray diffraction, crystal-structure prediction, and density functional theory computation of NMR chemical shifts.
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http://dx.doi.org/10.1002/anie.201501172DOI Listing
May 2015

Probing crystal packing of uniformly (13)C-enriched powder samples using homonuclear dipolar coupling measurements.

Solid State Nucl Magn Reson 2015 Feb 16;65:114-21. Epub 2014 Dec 16.

Aix-Marseille Université, CNRS, ICR UMR 7273, 13397 Marseille, France.

The relationship between the crystal packing of powder samples and long-range (13)C-(13)C homonuclear dipolar couplings is presented and illustrated for the case of uniformly (13)C-enriched L-alanine and L-histidine·HCl·H2O. Dipolar coupling measurement is based on the partial reintroduction of dipolar interactions by spinning the sample slightly off-magic-angle, while the coupling of interest for a given spin pair is isolated with a frequency-selective pulse. A cost function is used to correlate the so-derived dipolar couplings to trial crystal structures of the samples under study. This procedure allowed for the investigation of the l-alanine space group and L-histidine·HCl·H2O space group and unit-cell parameters.
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http://dx.doi.org/10.1016/j.ssnmr.2014.12.003DOI Listing
February 2015

Do spawn storage conditions influence the colonization capacity of a wheat-straw-based substrate by Agaricus subrufescens?

C R Biol 2014 Jul-Aug;337(7-8):443-50. Epub 2014 Jul 14.

Institut méditerranéen de biodiversité et d'écologie marine et continentale (IMBE), Aix Marseille université, UMR CNRS, IRD, Avignon université, faculté de Saint-Jérôme, 13397 Marseille cedex 20, France.

Storage conditions of the spawn of edible fungi are of major importance to facilitate the production of mushrooms. Here, standard storage conditions at 10°C or 15°C were used and the potential of colonization of standard European compost by the tropical species Agaricus subrufescens was assessed during the spawn running phase. Two lignocellulolytic activities, laccase and CMC-cellulase, were enhanced after storage compared to control as well as substrate transformation, as described by the aromaticity ratio and a humification ratio calculated from NMR data. This result indicates that mycelium growth probably occurred during storage at 10 or 15°C, leading to a larger amount of biomass in the inoculum. Moreover, the microbial functional diversity of the substrate was favored, showing that the electivity of the substrate was maintained. Thus, these findings indicate that recommendations for the mushroom producers can be established for A. subrufescens cultivation under European standard conditions.
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http://dx.doi.org/10.1016/j.crvi.2014.06.002DOI Listing
April 2015

Dynamic nuclear polarisation NMR of nanosized zirconium phosphate polymer fillers.

Chem Commun (Camb) 2014 Sep;50(70):10137-9

Aix Marseille Université, Centrale Marseille, CNRS, Fédération des Sciences Chimiques FR 1739, F-13397 Marseille, France.

Surface functionalisation with organic modifiers of multi-layered zirconium phosphate (ZrP) nanoparticles used as polymer fillers can be directly probed by dynamic nuclear polarisation NMR, which provides unambiguous evidence of the presence of P-O-C chemical bonds at the surface of the ZrP layers, thereby confirming successful functionalisation.
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http://dx.doi.org/10.1039/c4cc02723jDOI Listing
September 2014

A "click" chemistry constructed affinity system for 2-oxoglutaric acid receptors and binding proteins.

Org Biomol Chem 2014 Sep;12(33):6470-5

Aix-Marseille Université and CNRS, Centre Interdisciplinaire de Nanoscience de Marseille, UMR 7325, 13288, Marseille, France.

An ingenious and specific affinity resin designed to capture the 2-oxoglutaric acid (2-OG) binding proteins was constructed by appending a 2-OG tag to the solid resin via a Cu-catalyzed Huisgen "click" reaction. The so-obtained affinity resin was able to recognize, retain and separate the established 2-OG binding protein NtcA in both the pure form and crude cellular extract, thus constituting a valuable means of searching for novel 2-OG receptors with a view to exploring the signalling pathways of 2-OG, a key Krebs cycle intermediate with unprecedented signalling functions.
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http://dx.doi.org/10.1039/c4ob01005aDOI Listing
September 2014

Mimicking the 2-oxoglutaric acid signalling function using molecular probes: insights from structural and functional investigations.

Org Biomol Chem 2014 Jul;12(26):4723-9

Aix-Marseille Université, CNRS, CINaM UMR 7325, 13288, Marseille, France.

2-Oxoglutaric acid (2-OG) has gained considerable attention because of its newly discovered signalling role in addition to its established metabolic functions. With the aim of further exploring the signalling function of 2-OG, here we present a structure-activity relationship study using 2-OG probes bearing different carbon chain lengths and terminal groups. Our results highlight the importance of the five-membered carbon molecular skeleton and of the two carboxylic terminals in maintaining the signalling functions of the parent molecule 2-OG. These findings provide valuable information for designing new, effective molecular probes able to dissect and discriminate the newly discovered, complex signalling role of 2-OG from its canonical activity in metabolism.
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http://dx.doi.org/10.1039/c4ob00630eDOI Listing
July 2014

Long-term aging of a CeO(2) based nanocomposite used for wood protection.

Environ Pollut 2014 May 8;188:1-7. Epub 2014 Feb 8.

CNRS, Aix-Marseille Université, CEREGE UM34, UMR 7330, 13545 Aix en Provence, France; International Consortium for the Environmental Implications of Nanotechnology iCEINT, Aix en Provence, France.

A multi-scale methodology was used to characterize the long-term behavior and chemical stability of a CeO2-based nanocomposite used as UV filter in wood stains. ATR-FTIR and (13)C NMR demonstrated that the citrate coated chelates with Ce(IV) through its central carboxyl- and its α-hydroxyl- groups at the surface of the unaged nanocomposite. After 42 days under artificial daylight, the citrate completely disappeared and small amount of degradation products remained attached to the surface even after 112 days. Moreover, the release/desorption of the citrate layer led to a surface reorganization of the nano-sized CeO2 core observed by XANES (Ce L3-edge). Such a surface and structural transformation of the commercialized nanocomposite could have implications in term of fate, transport, and potential impacts towards the environment.
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http://dx.doi.org/10.1016/j.envpol.2014.01.016DOI Listing
May 2014

Functional patterns of microbial communities of rhizospheric soils across the development stages of a young mangrove in French Guiana.

Microb Ecol 2014 Feb 20;67(2):302-17. Epub 2013 Oct 20.

Institut Méditerranéen de Biodiversité et d'Ecologie marine et continentale (IMBE), Aix-Marseille Université, UMR CNRS IRD Avignon Université, Faculté de St-Jérôme, 13397, Marseille Cedex 20, France,

The functional patterns of microbial communities (microbial respiration, enzyme activities, functional diversity) and the relevant physico-chemical characteristics of rhizospheric soils were studied during the process of mudflat colonization by mangrove. The study site is a fringe mangrove stand located in Montabo Bay at Cayenne (French Guiana). It is characterized by different vegetation development stages dominated by an assemblage of Avicennia germinans and Laguncularia racemosa. Rhizospheric and surface soils were collected from three stations based on successional stages of mangrove colonization: pioneer (P), coppice (C), and young forest (F). The microbial functional patterns showed significant progressive shifts along the mangrove vegetation profile. The P stages, those most influenced by tide currents, were macroscopically characterized by hydro-sedimentary instability and micro-phytobenthic colonization of mudflat. This stage, characterized by low total organic carbon (TOC) content and quality, showed the lowest extracellular enzymatic activities and the highest functional metabolic diversities. TOC quality analyses by (13)C CPMAS NMR provided evidence of progressive TOC enrichment and an increasing imprint of aboveground vegetation on C quality as succession occurs. These differences in the origin, amount, and quality of soil organic matter (SOM) of older stages exerted both a quantitative and qualitative control over microbial functional responses. This indicated the enhancement of aboveground-belowground functional linkages, leading to the expression of high decomposition activities and a functional loss and specialization of rhizospheric microbial communities.
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http://dx.doi.org/10.1007/s00248-013-0298-9DOI Listing
February 2014

Structural requirements of 2-oxoglutaric acid analogues to mimic its signaling function.

Org Lett 2013 Sep 29;15(18):4662-5. Epub 2013 Aug 29.

Aix-Marseille Université , CINaM CNRS UMR 7325, 13288 Marseille, France, College of Chemistry and Molecular Sciences, Wuhan University , Wuhan 430072, P.R. China, Molecular Simulation Engineering Laboratory, University of Trieste , 34127 Trieste, Italy, National Interuniversity Consortium for Material Science and Technology, Research Unit MOSE-DEA, Trieste University , Italy, Spectropole , Faculté de Saint-Jérôme, Marseille, France, and Aix-Marseille Université , LCB CNRS UMR 7283, 13402 Marseille, France.

A 2-oxoglutaric acid (2-OG) probe bearing a methylene group introduced at the C4 position and a vinyl group to replace the carbonyl group at the C2 position elicited characteristic affinity for NtcA, the 2-OG receptor, while maintaining the signaling function of the parent natural metabolite 2-OG. This discovery opens new perspectives in the design, synthesis, and implementation of specific 2-OG analogues as molecular probes for investigating the complex 2-OG signaling pathways.
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http://dx.doi.org/10.1021/ol401914zDOI Listing
September 2013

19F NMR: a valuable tool for studying biological events.

Chem Soc Rev 2013 Oct;42(20):7971-82

Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.

With the spectacular advancement of NMR techniques and the flourishing of fluorine chemistry allowing the synthesis of various fluorinated molecules, (19)F NMR represents a compelling option for studying myriad biological events ranging from the structure and function of biomolecules, enzymatic mechanisms, and metabolic pathways, through to drug screening and discovery as well as medical imaging. In this tutorial review, we aim to provide readers with a brief overview of the recent applications of (19)F NMR in various areas relating to biological and biomedical research, together with a brief introduction of specific hardware improvements permitting the practical implementation of (19)F NMR.
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http://dx.doi.org/10.1039/c3cs60129cDOI Listing
October 2013
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