Sophie Lecomte

Altered structural connectivity of cortico-striato-pallido-thalamic networks in Gilles de la Tourette syndrome

See Jackson (doi:10.1093/brain/awu338) for a scientific commentary on this article. The neural substrate of Gilles de la Tourette syndrome is unknown. Worbe et al. use probabilistic tractography to demonstrate widespread structural abnormalities in cortico-striato-pallido-thalamic white matter pathways—likely arising from abnormal brain development—in patients with this syndrome.

Electrochemistry, AFM, and PM‐IRRA Spectroscopy of Immobilized Hydrogenase: Role of a Hydrophobic Helix in Enzyme Orientation for Efficient H2 Oxidation

Nickel–iron hydrogenase ([NiFe] Hase) catalyzes hydrogen splitting into protons and electrons, and is a potential biocatalyst in fuel cells. Three FeS clusters aligned as a conductive wire drive electrons from the [NiFe] active site to the surface of the enzyme, where the redox partner (including the electrode) binds. Direct enzyme connection gave access to thermodynamic and kinetic data of enzymatic reactions through direct electron transfer (DET). Mediated electron transfer (MET) allowed recreation of the physiological electron-transfer chain, and/or connection of unfavorably oriented enzymes. Previous work demonstrated that DET or MET processes for H2 oxidation by a soluble, O2-sensitive [NiFe] Hase from Desulfovibrio species could be controlled by electrostatic interaction. The presence of an acidic patch of amino acids, coupled to a dipole moment pointing towards the distal FeS cluster (positioned at the surface of the enzyme), allowed orientation of the enzyme, which turned upside down as a function of the charge on the electrochemical interface. Recently, we reported on the electrochemistry of membrane-bound Aquifex aeolicus (Aa) [NiFe] Hase, which exhibits outstanding resistance to O2, CO, and heat. [8–10] Efficient immobilization of this Hase was achieved on graphite electrodes, in aqueous electrolytes and ionic liquids, by encapsulation in carbon nanotube networks, or connection to a redox polymer. In contrast to the soluble, O2sensitive [NiFe] Hase, no specific orientation could be obtained by electrostatic interaction for Aa Hase, and thus control of the electron-transfer process was not possible. A model structure accordingly put forward a very different environment of the distal FeS cluster, with no charged amino acid patch, in accordance with the membrane anchorage. We analyze herein H2 oxidation by Aa Hase immobilized on self-assembled monolayers (SAMs) on gold electrodes as a function of both the length and the nature of the thiol derivative (see SI 1 and SI 2 in the Supporting Information). For the first time, AFM and polarization modulation infrared reflection adsorption (PM-IRRA) studies are reported for understanding Aa Hase orientation and its consequences for electron-transfer process in H2 oxidation. Positively charged 4-aminothiophenol (ArNH2) and negatively charged 6-mercaptohexanoic acid (C5COOH) SAMs both yield DET and MET processes for H2 oxidation (Figure 1a and b), and neither process is favored over the other. A mixed process was similarly observed for H2 oxidation at charged short-chain alkanethiols, which are known to bemore disordered. This strongly suggests that electroenzymatic H2 oxidation is linked to multiple orientations of Hase on top of the charged SAMs, and not to Hase present inside possible SAM defects. The lipophilic methylene blue (MB) molecule

Rubber Elongation Factor (REF), a Major Allergen Component in Hevea brasiliensis Latex Has Amyloid Properties

REF (Hevb1) and SRPP (Hevb3) are two major components of Hevea brasiliensis latex, well known for their allergenic properties. They are obviously taking part in the biosynthesis of natural rubber, but their exact function is still unclear. They could be involved in defense/stress mechanisms after tapping or directly acting on the isoprenoid biosynthetic pathway. The structure of these two proteins is still not described. In this work, it was discovered that REF has amyloid properties, contrary to SRPP. We investigated their structure by CD, TEM, ATR-FTIR and WAXS and neatly showed the presence of β-sheet organized aggregates for REF, whereas SRPP mainly fold as a helical protein. Both proteins are highly hydrophobic but differ in their interaction with lipid monolayers used to mimic the monomembrane surrounding the rubber particles. Ellipsometry experiments showed that REF seems to penetrate deeply into the monolayer and SRPP only binds to the lipid surface. These results could therefore clarify the role of these two paralogous proteins in latex production, either in the coagulation of natural rubber or in stress-related responses. To our knowledge, this is the first report of an amyloid formed from a plant protein. This suggests also the presence of functional amyloid in the plant kingdom.

Detection of an estrogen derivative in two breast cancer cell lines using a single core multimodal probe for imaging (SCoMPI) imaged by a panel of luminescent and vibrational techniques

3-Methoxy-17α-ethynylestradiol or mestranol is a prodrug for ethynylestradiol and the estrogen component of some oral contraceptive formulations. We demonstrate here that a single core multimodal probe for imaging - SCoMPI - can be efficiently grafted onto mestranol allowing its tracking in two breast cancer cell lines, MDA-MB-231 and MCF-7 fixed cells. Correlative imaging studies based on luminescence (synchrotron UV spectromicroscopy, wide field and confocal fluorescence microscopies) and vibrational (AFMIR, synchrotron FTIR spectromicroscopy, synchrotron-based multiple beam FTIR imaging, confocal Raman microspectroscopy) spectroscopies were consistent with one another and showed a Golgi apparatus distribution of the SCoMPI-mestranol conjugate in both cell lines.

Quantitative label-free RNA detection using surface-enhanced Raman spectroscopy

Surface-Enhanced Raman Spectroscopy (SERS) was performed to detect label-free RNA. We defined conditions which make it possible to probe the four bases of RNA, in single strands of polyadenosine (pA), polyuridine (pU), polycytosine (pC) and polyguanosine (pG). We therefore present below a quantitative analysis of mixtures of non-hybridized single strands, based on the deconvolution of the SERS mixture spectrum into the relative contributions of the SERS spectra of each constituent.

Hevea brasiliensis REF (Hev b 1) and SRPP (Hev b 3): An overview on rubber particle proteins

This review article aims to gather all the knowledge on two important proteins associated with Hevea brasiliensis rubber particles: namely the rubber elongation factor (REF) and the small rubber particle protein (SRPP). It covers more then three decades of research on these two proteins and their homologues in plants, and particularly emphasizes on the different possible properties or functions of these various proteins found in plants.

Development and Characterization of New Cyclodextrin Polymer-Based DNA Delivery Systems

In this study, we investigated whether a cyclodextrin polymer (polybetaCD) complexed with cationic adamantyl derivatives (Ada) could be used as a vector for gene delivery. DNA compaction as a function of adamantyl/DNA phosphate ratio (A/P) by this new class of vector was demonstrated using surface enhanced Raman spectroscopy, zeta potential measurements, and DNA retardation assays. Transfection data highlight the relationship between in vitro gene delivery efficiency and the combination of several physical properties of the polybetaCD/Ada/DNA polyplexes, including cationic polar headgroup valency and chemical structure of the spacer arm of Ada connectors, the adamantyl/DNA phosphate ratio (A/P) of the polybetaCD/Ada/DNA polyplexes, and the ionic strength of the medium. Finally, when associating the best formulation with a fusogenic peptide, we reached transfection levels which were of the same order as those obtained with DOTAP.

In Vivo and In Vitro Analyses of Toxic Mutants of HET-s: FTIR Antiparallel Signature Correlates with Amyloid Toxicity

The folding and interactions of amyloid proteins are at the heart of the debate as to how these proteins may or may not become toxic to their host. Although little is known about this issue, the structure seems to be clearly involved with effects on molecular events. To understand how an amyloid may be toxic, we previously generated a yeast toxic amyloid (mutant 8) from the nontoxic HET-s((218-289)) prion domain of Podospora anserina. Here, we performed a comprehensive structure-toxicity study by mutating individually each of the 10 mutations found in mutant 8. The study of the library of new mutants generated allowed us to establish a clear link between Fourier transform infrared antiparallel signature and amyloid toxicity. All of the mutants that form parallel β-sheets are not toxic. Double mutations may be sufficient to shift a parallel structure to antiparallel amyloids, which are toxic to yeast. Our findings also suggest that the toxicity of antiparallel structured mutants may be linked to interaction with membranes.

Comparative studies of nontoxic and toxic amyloids interacting with membrane models at the air-water interface.

Many in vitro studies have pointed out the interaction between amyloids and membranes, and their potential involvement in amyloid toxicity. In a previous study, we generated a yeast toxic mutant (M8) of the harmless model amyloid protein HET-s((218-289)). In this study, we compared the self-assembling process of the nontoxic wild-type (WT) and toxic (M8) protein at the air-water interface and in interaction with various phospholipid monolayers (DOPE, DOPC, DOPI, DOPS and DOPG). We first demonstrate using ellipsometry measurements and polarization-modulated infrared reflection absorption spectroscopy (PMIRRAS) that the air-water interface promotes and modifies the assembly of WT since an amyloid-like film was instantaneously formed at the interface with an antiparallel β-sheet structuration instead of the parallel β-sheet commonly observed for amyloid fibers generated in solution. The toxic mutant (M8) behaves in a similar manner at the air-water interface or in bulk, with a fast self-assembling and an antiparallel β-sheet organization. The transmission electron microscopy (TEM) images established the fibrillous morphology of the protein films formed at the air-water interface. Second, we demonstrate for the first time that the main driving force between this particular fungus amyloid and membrane interaction is based on electrostatic interactions with negatively charged phospholipids (DOPG, DOPI, DOPS). Interestingly, the toxic mutant (M8) clearly induces perturbations of the negatively charged phospholipid monolayers, leading to a massive surface aggregation, whereas the nontoxic (WT) exhibits a slight effect on the membrane models. This study allows concluding that the toxicity of the M8 mutant could be due to its high propensity to interact with membranes.

NMR investigation of pefloxacin-cation-DNA interactions: the essential role of Mg2+

Abstract 19 F-NMR spectra show that, in the absence of magnesium, pefloxacin binds poorly to DNA and preferentially to single-stranded rather than to double-stranded DNA. In the presence of a fixed concentration of magnesium (10 mM), the competition between double-stranded DNA species and pefloxacin for binding to magnesium is more important with linear DNA than with supercoiled plasmidic DNA. Only the 19 F signals of pefloxacin free and bound to magnesium are observed, but the formation of the ternary complex pefloxacin/Mg 2+ /DNA is indicated by the decrease in the integration of the proton decoupled 19 F signal at the high concentrations of double-stranded (linear and plasmidic) DNA. The variations of the 19 F NOE demonstrate that this formation depends strongly on the magnesium concentration, the optimum concentration being ≈2 mM in the presence of Escherichia coli DNA (4 mM). The 19 F NMR data show that the quinolone ring of pefloxacin has little mobility in the ternary complex. In this complex, pefloxacin could be bound to two magnesium ions, each cation acting as a bridge between this molecule and a phosphate group of the DNA backbone.