Hervé Desvaux

Bio: Hervé Desvaux is an academic researcher from Université Paris-Saclay. The author has contributed to research in topics: Xenon & Nuclear magnetic resonance spectroscopy. The author has an hindex of 29, co-authored 80 publications receiving 2256 citations. Previous affiliations of Hervé Desvaux include Alternatives & DSM.

Swollen liquid-crystalline lamellar phase based on extended solid-like sheets

Abstract: Ordering particles at the nanometre length scale is a challenging and active research area in materials science. Several approaches have so far been developed, ranging from the manipulation of individual particles to the exploitation of self-assembly in colloids. Nanometre-scale ordering is well known to appear spontaneously when anisotropic organic moieties form liquid-crystalline phases; this behaviour is also observed for anisotropic mineral nanoparticles resulting in the formation of nematic, smectic and hexagonal mesophases. Here we describe a lyotropic liquid-crystalline lamellar phase comprising an aqueous dispersion of planar solid-like sheets in which all the atoms involved in a layer are covalently bonded. The spacing of these phosphatoantimonate single layers can be increased 100-fold, resulting in one-dimensional structures whose periodicity can be tuned from 1.5 to 225 nanometres. These highly organized materials can be mechanically or magnetically aligned over large pH and temperature ranges, and this property can be used to measure residual dipolar couplings for the structure determination of biomolecules by liquid-state NMR. We also expect that our approach will result in the discovery of other classes of mineral lyotropic lamellar phases.

Water soluble cryptophanes showing unprecedented affinity for xenon: candidates as NMR-based biosensors.

Abstract: Cryptophanes bearing OCH2COOH groups in place of the methoxy groups represent a new class of xenon-carrier molecules soluble in water at biological pH. By using 1H and 129Xe NMR (thermally- and laser-polarized dissolved gas), the structural and dynamical behaviors of these host molecules as well as their interaction with xenon are studied. They are shown to exist in aqueous solution under different conformations in very slow exchange. A saddle form present for one of these conformations could explain the 1H NMR spectra. Whereas the cryptophanes in such a conformation are unable to complex xenon, unprecedented high binding constants are found for cryptophanes in the other canonical crown−crown conformation. These host molecules could therefore be valuable candidates for biosensing using 129Xe MRI.

A cryptophane core optimized for xenon encapsulation.

Abstract: The smallest cryptophane ever synthesized, cryptophane-1.1.1 (1), whose internal volume is estimated to be 81 A3, exhibits the highest binding constant (10000 M-1 at 293 K) in organic solution for xenon encapsulation determined to date. The very slow kinetics of decomplexation on the NMR time scale results in an extremely sharp 129Xe NMR signal for the Xe@1 complex, which shows an unexpected low-frequency shift. The free energy of activation for decomplexation of xenon at 293 K is ΔG⧧out = 64.9 ± 3 kJ mol-1 (ΔH⧧out = 43.2 ± 1.6 kJ mol-1; ΔS⧧out = −74 ± 3 J mol-1 K-1). These properties suggest that the cryptophane core of 1 is optimized for use in sensing applications in combination with laser-polarized xenon.

Off-resonance rf fields in heteronuclear NMR: Application to the study of slow motions

Abstract: The advantages of using off-resonance rf fields in heteronuclear self-relaxation experiments are explored on a fully 15N-enriched protein It is firstly shown that in the absence of slow motions the longitudinal and transverse 15N self-relaxation rate values derived with this method are in agreement with the ones measured by the classical inversion-recovery and Carr–Purcell–Meiboom–Gill (CPMG) sequences, respectively Secondly, by comparing the 15N transverse self-relaxation rates obtained by the proposed off-resonance sequence and by the CPMG sequence, 11 residues out of the 61 of toxin α are shown to exhibit a chemical exchange phenomenon in water on a time scale ranging from 1 µs to 100 ms By varying the effective field amplitude, chemical exchange processes involving these residues are measured and the corresponding correlation times are evaluated without having assumed any motion model Similar, though less precise, results are given by the analysis of the 15N off-resonance self-relaxation rates on the basis of the Lipari–Szabo model to describe the fast internal dynamics of toxin α

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Art of electronics

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Graphene chiral liquid crystals and macroscopic assembled fibres

Abstract: Chirality and liquid crystals are both widely expressed in nature and biology Helical assembly of mesophasic molecules and colloids may produce intriguing chiral liquid crystals To date, chiral liquid crystals of 2D colloids have not been explored As a typical 2D colloid, graphene is now receiving unprecedented attention However, making macroscopic graphene fibres is hindered by the poor dispersibility of graphene and by the lack of an assembly method Here we report that soluble, chemically oxidized graphene or graphene oxide sheets can form chiral liquid crystals in a twist-grain-boundary phase-like model with simultaneous lamellar ordering and long-range helical frustrations Aqueous graphene oxide liquid crystals were continuously spun into metres of macroscopic graphene oxide fibres; subsequent chemical reduction gave the first macroscopic neat graphene fibres with high conductivity and good mechanical performance The flexible, strong graphene fibres were knitted into designed patterns and into directionally conductive textiles