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The SARS-Cov-2 covid-19 pandemic outbreak continues to claim victims to this day. As the vaccine is ineffective for completely eradicating the virus, there is an urgent need to look at other solutions, including developing antivirals.
Lipopeptides, particularly surfactin, have been recognized for their antiviral activity against several enveloped viruses. However, a better comprehension of their mode of action is necessary to develop antivirals based on those lipopeptides. Moreover, studying several variants allows a better insight into the relationships between the structure of lipopeptides and their antiviral activity.
In this work, a biophysical approach involving the use of liposomes as membrane biomimetic models was used. Four liposome models were created, including one aiming to mimic the host cell plasma membrane and one seeking to mimic the viral membrane.
The effect of surfactin variants on membrane permeability and fluidity was analyzed on these biomimetic liposomes.
Several mechanisms have been suggested to explain the surfactins action on liposomes. It was hypothesized that some variants had two-stage effects on membranes incorporating lipids such as cholesterol and PE. These lipids, potentially at the origin of this biphasic mechanism, could make the membrane more resistant to high surfactin concentrations. It was also hypothesized that the structure of some variants might influence the toxicity of surfactins on the membranes. Finally, it was observed that the studied variants might be more toxic on biological mimicking membranes than viral ones. Further studies are nevertheless mandatory to assert all these hypotheses.

Coronavirus --- Liposomes --- Characterisation --- Biophysics --- Membranes --- Surfactin --- Lipopeptides --- In vitro --- Sciences du vivant > Multidisciplinaire, généralités & autres

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The cyclic lipopeptide (CLP) surfactin is secreted by Bacillus spp. such as Bacillus velezensis, a plant growth promoting rhizobacteria (PGPR). This molecule has biological functions among which the ability to stimulate the induced systemic resistance (ISR) in several plant models. This phenomenon could be part of the transition to sustainable agriculture since it can help the plant to face many pathogens infections. However, the molecular basis of ISR induction by surfactin is still poorly understood. In this context, a structure-activity approach of surfactin has been adopted to get deeper insights into the relation between this CLP and ISR . Thus, the aim of this thesis is to evaluate the impact
of structural changes in the plant immunization potential of surfactin. For this purpose, naturally occurring variants of surfactin, pumilacidin and lichenysin, have been chosen. These CLPs vary in fatty acid chain length and in peptide composition. In order to deepen our knowledge in the induction of ISR in planta, the reactive oxygen species (ROS) burst and the stimulation of the transcriptional factor MYB72, two plant immunity markers, have been studied. To achieve these objectives, surfactin, pumilacidin and lichenysin have been produced and purified in order to test their ability to trigger ROS burst and myb72 stimulation in addition to their activity as ISR elicitors in Arabidopsis thaliana L. (Arabidopsis), the plant model used in this study. In this work, we firstly demonstrate that the structure of surfactin is determinant for ISR induction in Arabidopsis. Then, regarding ISR markers, our results suggest that myb72 could be an interesting ISR marker where ROS burst alone is not sufficient to trigger ISR. Moreover, we prove that the change of one single amino acid in the peptide ring of the CLP can alter the activity of surfactin. Furthermore, this work provides new insight into ISR induction and in particular on the role of the enzyme, β-glucosidase
BGLU42 in relation to myb72.

Surfactin --- Pumilacidin --- ISR --- Lichenysin --- Arabidopsis --- Bacillus --- Structure --- Sciences du vivant > Biochimie, biophysique & biologie moléculaire --- Sciences du vivant > Microbiologie

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Very few materials have attracted so much attention in recent years, both from researchers and industry, as layered double hydroxides (LDHs) have. LDHs, which are also referred to as anionic clays or hydrotalcites, are a wide class of inorganic ionic lamellar clay materials consisting of alternately stacked positively charged metal hydroxide layers with intercalated charge-balancing anions in hydrated interlayer regions. Their unique properties, such as their extremely high versatility in chemical composition and intercalation ability, extraordinary tuneability in composition as well as morphology, good biocompatibility and high anion exchangeability, have triggered immense interdisciplinary interest for their use in many different fields of chemistry, biology, medicine, and physics. Indeed, the applications of LDHs are constantly growing: LDHs, in the form of aggregated lamellar clusters, exfoliated single-layer nanosheets, or hierarchical films of interconnected nanoplatelets, can be effectively used as nanoscale vehicles in drug delivery, heterogeneous catalysts and supports for molecular catalysts, ion exchangers and adsorbents, solid electrolytes or fillers in electrochemistry, for the fabrication of superhydrophobic surfaces, water treatment and purification, and the synthesis of functional thin films. This book gathers the contributions to the Special Issue “Layered Double Hydroxides” of Crystals, which includes two review articles and seven research papers.

Research & information: general --- layered double hydroxide --- memory effect --- rare earth --- europium --- 1,3,5-benzenetricarboxylic acid --- alginate beads --- green sorbent --- selective adsorption --- heavy metals --- tetracycline --- metal hydroxides --- layered double hydroxides --- removal --- water sample --- Bacillus subtilis --- surfactin --- quantitative analysis --- fermentation --- growth phase --- cellular biology --- catalysis --- DNA --- drug delivery --- hydrotalcite --- osteogenesis --- photocatalysis --- RNA. --- antimonate uptake --- mine water --- brandholzite --- zincalstibite --- iron precursor --- acidic residual solution --- LDH synthesis --- Mo(VI) adsorption --- resveratrol --- solid lipid nanoparticles --- endurance exercise --- mitochondrial nutrients --- mitochondrial quality control --- origin of life --- layer double hydroxide --- synthetic biology --- bioinspired devices --- biosensors --- bioanalysis --- n/a

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Very few materials have attracted so much attention in recent years, both from researchers and industry, as layered double hydroxides (LDHs) have. LDHs, which are also referred to as anionic clays or hydrotalcites, are a wide class of inorganic ionic lamellar clay materials consisting of alternately stacked positively charged metal hydroxide layers with intercalated charge-balancing anions in hydrated interlayer regions. Their unique properties, such as their extremely high versatility in chemical composition and intercalation ability, extraordinary tuneability in composition as well as morphology, good biocompatibility and high anion exchangeability, have triggered immense interdisciplinary interest for their use in many different fields of chemistry, biology, medicine, and physics. Indeed, the applications of LDHs are constantly growing: LDHs, in the form of aggregated lamellar clusters, exfoliated single-layer nanosheets, or hierarchical films of interconnected nanoplatelets, can be effectively used as nanoscale vehicles in drug delivery, heterogeneous catalysts and supports for molecular catalysts, ion exchangers and adsorbents, solid electrolytes or fillers in electrochemistry, for the fabrication of superhydrophobic surfaces, water treatment and purification, and the synthesis of functional thin films. This book gathers the contributions to the Special Issue “Layered Double Hydroxides” of Crystals, which includes two review articles and seven research papers.

Research & information: general --- layered double hydroxide --- memory effect --- rare earth --- europium --- 1,3,5-benzenetricarboxylic acid --- alginate beads --- green sorbent --- selective adsorption --- heavy metals --- tetracycline --- metal hydroxides --- layered double hydroxides --- removal --- water sample --- Bacillus subtilis --- surfactin --- quantitative analysis --- fermentation --- growth phase --- cellular biology --- catalysis --- DNA --- drug delivery --- hydrotalcite --- osteogenesis --- photocatalysis --- RNA. --- antimonate uptake --- mine water --- brandholzite --- zincalstibite --- iron precursor --- acidic residual solution --- LDH synthesis --- Mo(VI) adsorption --- resveratrol --- solid lipid nanoparticles --- endurance exercise --- mitochondrial nutrients --- mitochondrial quality control --- origin of life --- layer double hydroxide --- synthetic biology --- bioinspired devices --- biosensors --- bioanalysis --- layered double hydroxide --- memory effect --- rare earth --- europium --- 1,3,5-benzenetricarboxylic acid --- alginate beads --- green sorbent --- selective adsorption --- heavy metals --- tetracycline --- metal hydroxides --- layered double hydroxides --- removal --- water sample --- Bacillus subtilis --- surfactin --- quantitative analysis --- fermentation --- growth phase --- cellular biology --- catalysis --- DNA --- drug delivery --- hydrotalcite --- osteogenesis --- photocatalysis --- RNA. --- antimonate uptake --- mine water --- brandholzite --- zincalstibite --- iron precursor --- acidic residual solution --- LDH synthesis --- Mo(VI) adsorption --- resveratrol --- solid lipid nanoparticles --- endurance exercise --- mitochondrial nutrients --- mitochondrial quality control --- origin of life --- layer double hydroxide --- synthetic biology --- bioinspired devices --- biosensors --- bioanalysis