A mathematical analysis of the GW0 method for computing electronic excited energies of molecules

This paper analyses the GW method for finite electronic systems. In a first step, we provide a mathematical framework for the usual one-body operators that appear naturally in many-body perturbation theory. We then discuss the GW equations which construct an approximation of the one-body Green's function, and give a rigorous mathematical formulation of these equations. Finally, we study the well-posedness of the GW0 equations, proving the existence of a unique solution to these equations in a perturbative regime

Phase transition in the Peierls model for polyacetylene

We consider the Peierls model for closed polyactetylene chains with an even number of carbon atoms as well as infinite chains, in the presence of temperature. We prove the existence of a critical temperature below which the chain is dimerized, and above which it is 1-periodic. The chain behaves like an insulator below the critical temperature and like a metal above it. We characterize the critical temperature in the thermodynamic limit model, and prove that it is exponentially small in the rigidity of the chain. We study the phase transition around this critical temperature.Comment: Final version to appear in Ann. Henri Poincar{\'e

Contribution of tissue textural pattern and conventional index to glioma staging in FDopa-PET/CT

National audienceAim: We studied whether the characterization of tumor texture in FDopa-PET/CT could assist in the identification of tumor grades in both primitive and recurrent gliomas. Materials and Methods: Eighty one patients with gliomas were studied, including 52 newly diagnosed tumors and 29 recurrent tumors. For each tumor, the SUVpeak and metabolic volume (MV) were measured, as well as 32 textural indices (TI). The ability of SUVpeak, MV and TI was investigated by using each index alone first (with ROC analyses), and then by using couples consisting of one TI with SUVpeak in a binomial model (with ROC analyses and a reclassification method). The pathological examination was assumed to provide the gold standard grade. Results: Neither SUVpeak nor MV could discriminate low-grade tumors (LG) from high-grade tumors (HG) in newly-diagnosed tumors, while SUVpeak alone could discriminate LG from HG in recurrent tumors (p=0.02). Combining a TI with SUVpeak led to a significant LG / HG discrimination for newly-diagnosed tumors (p = 0.01). Among all TI, entropy led to the best reclassification performance. Conclusion: The co-analysis of FDopa-PET/CT SUVpeak and well-selected TI (such as entropy) made it possible to improve the classification of newly-diagnosed gliomas

Molecular cloning and functional characterization of psoralen synthase, the first committed monooxygenase of furanocoumarin biosynthesis

Ammi majus L. accumulates linear furanocoumarins by cytochrome P450 (CYP)-dependent conversion of 6-prenylumbelliferone via (؉)-marmesin to psoralen. Relevant activities, i.e. psoralen synthase, are induced rapidly from negligible background levels upon elicitation of A. majus cultures with transient maxima at 9 -10 h and were recovered in labile microsomes. Expressed sequence tags were cloned from elicited Ammi cells by a nested DD-RT-PCR strategy with CYP-specific primers, and full-size cDNAs were generated from those fragments correlated in abundance with the induction profile of furanocoumarin-specific activities. One of these cDNAs representing a transcript of maximal abundance at 4 h of elicitation was assigned CYP71AJ1. Functional expression in Escherichia coli or yeast cells initially failed but was accomplished eventually in yeast cells after swapping the N-terminal membrane anchor domain with that of CYP73A1. The recombinant enzyme was identified as psoralen synthase with narrow substrate specificity for (؉)-marmesin. Psoralen synthase catalyzes a unique carbon-chain cleavage reaction concomitantly releasing acetone by syn-elimination. Related plants, i.e. Heracleum mantegazzianum, are known to produce both linear and angular furanocoumarins by analogous conversion of 8-prenylumbelliferone via (؉)-columbianetin to angelicin, and it was suggested that angelicin synthase has evolved from psoralen synthase. However, (؉)-columbianetin failed as substrate but competitively inhibited psoralen synthase activity. Analogy modeling and docked solutions defined the conditions for high affinity substrate binding and predicted the minimal requirements to accommodate (؉)-columbianetin in the active site cavity. The studies suggested that several point mutations are necessary to pave the road toward angelicin synthase evolution. Furanocoumarins are produced by many plants, mostly of the Apiaceae, Rutaceae, Moraceae, or the Coronilla and Psoralea genera of the Fabaceae (1-3). Multiple pharmacological effects have been ascribed to several of these metabolites (4 -6), which were included in clinical screenings but received attention also for their inhibitory effect on monooxygenases involved in drug metabolism (7-9) and potential toxicity (10). The (dihydro)furan-substituted 2H-1-benzopyran-2-one forms the characteristic core structure, and the annulation type distinguishes the linear furanocoumarins or psoralens from the angular furanocoumarin

Optimization of the Culture Medium Composition to Improve the Production of Hyoscyamine in Elicited Datura stramonium L. Hairy Roots Using the Response Surface Methodology (RSM)

Traditionally, optimization in biological analyses has been carried out by monitoring the influence of one factor at a time; this technique is called one-variable-at-a-time. The disadvantage of this technique is that it does not include any interactive effects among the variables studied and requires a large number of experiments. Therefore, in recent years, the Response Surface Methodology (RSM) has become the most popular optimization method. It is an effective mathematical and statistical technique which has been widely used in optimization studies with minimal experimental trials where interactive factors may be involved. This present study follows on from our previous work, where RSM was used to optimize the B5 medium composition in [NO3−], [Ca2+] and sucrose to attain the best production of hyoscyamine (HS) from the hairy roots (HRs) of Datura stramonium elicited by Jasmonic Acid (JA). The present paper focuses on the use of the RSM in biological studies, such as plant material, to establish a predictive model with the planning of experiments, analysis of the model, diagnostics and adjustment for the accuracy of the model. With the RSM, only 20 experiments were necessary to determine optimal concentrations. The model could be employed to carry out interpolations and predict the response to elicitation. Applying this model, the optimization of the HS level was 212.7% for the elicited HRs of Datura stramonium, cultured in B5-OP medium (optimized), in comparison with elicited HRs cultured in B5 medium (control). The optimal concentrations, under experimental conditions, were determined to be: 79.1 mM [NO3−], 11.4 mM [Ca2+] and 42.9 mg/L of sucrose

Evaluation of Acute and Subacute Toxicity of Fumaria officinalis Alkaloids in Mice

Background: Fumaria officinalis is largely used in traditional medicine due to its efficiency in the treatment and prevention of numerous diseases and its large spectrum of therapeutic effects. Its multiple beneficial properties are due to its richness in bioactive substances, particularly isoquinoline alkaloids. However, few studies have addressed the toxicity of this plant. Objectives: The present work aimed to study acute and subacute toxicity of alkaloids extracted from F. officinalis using Swiss albino mice as the in vivo model. Methods: Alkaloids from the aerial parts of F. officinalis were extracted and administered to male and female Swiss albino mice. The acute and subacute toxicities were studied by monitoring the weight and histopathological study of animal bodies and organs (e.g., liver, heart, spleen, and kidneys). Results: The results revealed that mice treated with increasing doses developed serious symptoms of toxicity (i.e., respiratory problems, tremors, coma, and paralysis leading the death) and lost weight. The LD50 was estimated at 1341.11 mg/kg permitting its classification as a low-toxic plant. The microscopic observations demonstrated disturbances in the kidney and liver, but not the heart and spleen. Conclusion: The alkaloids of the aerial parts of F. officinalis expressed severe toxicity in mice, particularly at high doses. Nevertheless, the neutral fraction of alkaloids is more indicated

XLF and APLF bind Ku80 at two remote sites to ensure DNA repair by non-homologous end joining

International audienceThe Ku70-Ku80 (Ku) heterodimer binds rapidly and tightly to the ends of DNA double-strand breaks and recruits factors of the non-homologous end-joining (NHEJ) repair pathway through molecular interactions that remain unclear. We have determined crystal structures of the Ku-binding motifs (KBM) of the NHEJ proteins APLF (A-KBM) and XLF (X-KBM) bound to a Ku-DNA complex. The two KBM motifs bind remote sites of the Ku80 alpha/beta domain. The X-KBM occupies an internal pocket formed by an unprecedented large outward rotation of the Ku80 alpha/beta domain. We observe independent recruitment of the APLF-interacting protein XRCC4 and of XLF to laser-irradiated sites via binding of A- and X-KBMs, respectively, to Ku80. Finally, we show that mutation of the X-KBM and A-KBM binding sites in Ku80 compromises both the efficiency and accuracy of end joining and cellular radiosensitivity. A- and X-KBMs may represent two initial anchor points to build the intricate interaction network required for NHEJ

A simple derivation of moir\'e-scale continuous models for twisted bilayer graphene

We provide a formal derivation of a reduced model for twisted bilayer graphene (TBG) from Density Functional Theory. Our derivation is based on a variational approximation of the TBG Kohn-Sham Hamiltonian and asymptotic limit techniques. In contrast with other approaches, it does not require the introduction of an intermediate tight-binding model. The so-obtained model has a mathematical structure similar to that of the Bistritzer-MacDonald (BM) model but it contains some additional terms. Its parameters can be easily computed from Kohn-Sham calculations on single-layer graphene and untwisted bilayer graphene with different stacking. It allows one in particular to estimate the parameters $w_{\rm AA}$ and $w_{\rm AB}$ of the BM model from first-principles. The resulting numerical values, namely $w_{\rm AA}=w_{\rm AB} \simeq 126$ meV for the experimental interlayer mean distance are in good agreement with the empirical values $w_{\rm AA}=w_{\rm AB}=110$ meV obtained by fitting to experimental data. We also show that if the BM parameters are set to $w_{\rm AA}=w_{\rm AB} \simeq 110$ meV, the BM model is an accurate approximation of the variational model. A noticeable difference between the two models is that at the first magic angle, the almost flat bands of our reduced model are isolated from the other bands by a positive gap of about 10 meV, while there is no gap with the BM model

Synthèse et accumulation d'alcaloïdes tropaniques chez Datura innoxia Mill. cultivé en hydroponie (analyse des effets de l'environnement biotique et abiotique)

Datura innoxia Mill., une plante de la famille des solanacées synthétisant des alcaloïdes tropaniques, a été utilisée comme modèle pour cette étude portant sur les cultures en hydroponie. Nous avons pu montrer que cette espèce présentait une bonne croissance en conditions hors sol et que la production d'hyoscyamine et de scopolamine était égale ou supérieure à celle obtenue en culture classique en terre. En particulier, la croissance et la quantité de métabolites secondaires accumulés dans la plantes peuvent être augmentées en jouant sur des facteurs biotiques (précurseurs, AIA, Agrobacterium rhizogenes) et abiotiques (ozone, lumière). Une petite partie des molécules contenues dans les racines sont libérées naturellement par exsudation dans la solution nutritive utilisée durant la culture. L'utilisation de traitements de perméabilisation tels que le Tween20, la température, ou la sonication permettent l'obtention d'une sortie massive des composés d'intérêt. Les alcaloïdes tropaniques ainsi relargués par les plantes peuvent ensuite être récupérés par mise en œuvre d'un piège liquide-solide basé sur des méthodes chromatographiques. L'ensemble de cette étude démontre qu'il est techniquement possible d'utiliser les cultures hors sol pour la production de métabolites secondaires végétaux.Datura innoxia Mill., is a solanaceous plant synthetizing tropane alkaloids. It bas been studied to evaluate its potential when cultivated in soil-less conditions. As compared to classical culture conditions in soil, we could demonstrate that hydropony favoured growth and secondary metabolites accumulation within the biomass. Different biotic or abiotic treatments such as - 1) feeding the plants with tropane alkaloid precursors or AIA, 2) inoculation with Agrobacterium rhizogenes, 3) optimisation of light exposure or 4) stress treatments such as ozone exposure - can lead to hyoscyamine and scopolamine overproduction. These compounds are shown to be naturally exuded from roots into the nutrient solutions used for plant growth. Permeabilisation treatments using Tween20, temperature stress or sonication can drastically enhance such metabolites release. Coupled to trapping technology based on chromatographical . techniques, hydropony is shown to be a very promising tool for producmg plant metabolItes of interest.NANCY/VANDOEUVRE-INPL (545472102) / SudocSudocFranceF

Identification des enzymes intervenant dans le transfert des acides gras dans les végétaux (spécificité de ces enzymes vis-à-vis de la prise en charge d'acides gras inhabituels)

COMPIEGNE-BU (601592101) / SudocSudocFranceF