Chitosan-Modified Polyethyleneimine Nanoparticles for Enhancing the Carboxylation Reaction and Plants' CO2 Uptake

Increasing plants' photosynthetic efficienc y is a major challenge that must be addressed in order to cover the food demands of the growing population in the changing climate. Photosynthes i s is greatly limited at the initial carboxylation reaction, where CO2 is converted to the organic acid 3-PGA, catalyzed by the RuBisCO enzyme. RuBisCO has poor affinity for CO2, but also the CO2 concentration at the RuBisCO site is limited by the diffusion of atmospheric CO2 through the various leaf compartments to the reaction site. Beyond genetic engineer-ing, nanotechnology can offer a materials-based approach for enhancing photosynthesis, and yet, it has mostly been explored for the light-dependent reactions. In this work, we developed polyethyleneimine-based nanoparticl e s for enhancing the carbox-ylation reaction. We demonstrate that the nanoparticles can capture CO2 in the form of bicarbonate and increase the CO2 that reacts with the RuBisCO enzyme, enhancing the 3-PGA production in in vitro assays by 20%. The nanoparticles can be introduced to the plant via leaf infiltration and, because of the functionalization with chitosan oligomers, they do not induce any toxic effect to the plant. In the leaves, the nanoparticles localize in the apoplastic space but also spontaneously reach the chloroplasts where photosynthetic activity takes place. Their CO2 loading-dependent fluorescence verifies that, in vivo, they maintain their abi l i t y to capture CO2 and can be therefore reloaded with atmospheric CO2 while in planta. Our results contribute to the development of a nanomaterials-based CO2-concentrating mechanism in plants t h a t can potentially increase photosynthetic efficiency and overall plants' CO2 storage

Unified analysis of shape and structural connectivity of neural pathways

International audienceAn abnormal brain development due to a neuropsychiatric disorder can influence the shape and the anatomical organization of both white and grey matter structures. An example is the syndrome of Gilles de la Tourette (GTS) which is thought to be associated with dysfunctions of the cortico-striato-pallido-thalamic circuits [6]. These anatomical complexes should be studied as a whole, analysing both the shape and the relative position of their structures.Atlas constructions permit to estimate an average shape complex of a given population, called template, and its deformations towards the shape complexes of each subject. The template represents the morphological invariants of the population whereas the deformations capture its variability.Previous works defined these deformations as single diffeomorphisms acting on the entire 3D space, so that ending points of fiber bundles could not move independently of grey matter structures [1,2,4,5]. This implicitly assumes that fiber bundles connect the same areas of grey matter structures across subjects. This assumption is not compatible with the aforementioned hypothesis about GTS [6] which relates the syndrome to atypical configurations of neural circuits. We propose a new atlas construction method which can handle both fibers and surfaces and which is based on a double diffeomorphism. This permits to analyse the morphological variations of each structure and the changes in the relative position between fiber bundles and grey matter structures, namely the variations in structural connectivity

PET-BIDS, an extension to the brain imaging data structure for positron emission tomography

The Brain Imaging Data Structure (BIDS) is a standard for organizing and describing neuroimaging datasets, serving not only to facilitate the process of data sharing and aggregation, but also to simplify the application and development of new methods and software for working with neuroimaging data. Here, we present an extension of BIDS to include positron emission tomography (PET) data, also known as PET-BIDS, and share several open-access datasets curated following PET-BIDS along with tools for conversion, validation and analysis of PET-BIDS datasets

PET-BIDS, an extension to the brain imaging data structure for positron emission tomography

The Brain Imaging Data Structure (BIDS) is a standard for organizing and describing neuroimaging datasets. It serves not only to facilitate the process of data sharing and aggregation, but also to simplify the application and development of new methods and software for working with neuroimaging data. Here, we present an extension of BIDS to include positron emission tomography (PET) data (PET-BIDS). We describe the PET-BIDS standard in detail and share several open-access datasets curated following PET-BIDS. Additionally, we highlight several tools which are already available for converting, validating and analyzing PET-BIDS datasets.Competing Interest StatementThe authors have declared no competing interest

The past, present, and future of the Brain Imaging Data Structure (BIDS)

The Brain Imaging Data Structure (BIDS) is a community-driven standard for the organization of data and metadata from a growing range of neuroscience modalities. This paper is meant as a history of how the standard has developed and grown over time. We outline the principles behind the project, the mechanisms by which it has been extended, and some of the challenges being addressed as it evolves. We also discuss the lessons learned through the project, with the aim of enabling researchers in other domains to learn from the success of BIDS

Double diffeomorphism: combining morphometry and structural connectivity analysis

International audienceThe brain is composed of several neural circuits which may be seen as anatomical complexes composed of grey matter structures interconnected by white matter tracts. Grey and white matter components may be modelled as 3D surfaces and curves respectively. Neurodevelopmental disorders involve morphological and organizational alterations which can not be jointly captured by usual shape analysis techniques based on single diffeomorphisms. We propose a new deformation scheme, called double diffeomorphism, which is a combination of two diffeomorphisms. The first one captures changes in structural connectivity, whereas the second one recovers the global morphological variations of both grey and white matter structures. This deformation model is integrated into a Bayesian framework for atlas construction. We evaluate it on a data-set of 3D structures representing the neural circuits of patients with Gilles de la Tourette syndrome (GTS). We show that this approach makes it possible to localise, quantify and easily visualise the pathological anomalies altering the morphology and organization of the neural circuits. Furthermore, results also indicate that the proposed deformation model better discriminates between controls and GTS patients than a single diffeomorphism

Joint Morphometry of Fiber Tracts and Gray Matter structures using Double Diffeomorphisms

International audienceThis work proposes an atlas construction method to jointly analyse the relative position and shape of fiber tracts and gray matter structures. It is based on a double diffeomorphism which is a composition of two diffeomorphisms. The first diffeomorphism acts only on the white matter keeping fixed the gray matter of the atlas. The resulting white matter , together with the gray matter , are then deformed by the second diffeomorphism. The two diffeomorphisms are related and jointly optimised. In this way , the first diffeomorphisms explain the variability in structural connectivity within the population , namely both changes in the connected areas of the gray matter and in the geometry of the pathway of the tracts. The second diffeomorphisms put into correspondence the homologous anatomical structures across subjects. Fiber bundles are approximated with weighted prototypes using the metric of weighted currents . The atlas , the covariance matrix of deformation parameters and the noise variance of each structure are automatically estimated using a Bayesian approach. This method is applied to patients with Tourette syndrome and controls showing a variability in the structural connectiv-ity of the left cortico-putamen circuit

Synthèse stéréosélective d'iminosucre-C-glycosides par addition de réactifs organométalliques sur des N-tert-butanesulfinyl glycosylamines

International audienceA comprehensive study of the preparation and reactivity of N-tert-butanesulfinyl glycosylamines with simple Grignard and organo lithium reagents in batch vs. continuous flow chemistry is reported. As they readily react as latent imine equivalents with a variety of carbon nucleophiles, these carbohydrate derivatives constitute very useful precursors for the diastereoselective synthesis of bioactive compounds such as iminosugar-C-glycosides. A hybrid protocol, involving the addition of benzylmagnesium chloride to a (SR)arabinofuranosylamine substrate in flow, at room temperature, combined with a cyclization protocol in batch is also described for the first time. Of note, this semi-continuous flow process shortens the synthesis of imino-C-glycoside scaffolds to a single workda

Intrinsic reactivity and driving force dependence in concerted proton–electron transfers to water illustrated by phenol oxidation

Three experimental techniques, laser flash photolysis, redox catalysis, and stopped-flow, were used to investigate the variation of the oxidation rate constant of phenol in neat water with the driving force offered by a series of electron acceptors. Taking into account a result previously obtained with a low–driving force electron acceptor thus allowed scanning more than half an electron-volt driving force range. Variation of the rate constant with pH showed the transition between a direct phenol oxidation reaction at low pH, where the rate constant does not vary with pH, and a stepwise reaction involving the prior deprotonation of phenol by OH-, characterized by a unity-slope variation. Analyses of the direct oxidation kinetics, based on its variation with the driving force and on the determination of H/D isotope effects, ruled out a stepwise mechanism in which electron transfer is followed by the deprotonation of the initial cation radical at the benefit of a pathway in which proton and electron are transferred concertedly. Derivation of the characteristics of counterdiffusion in termolecular reactions allowed showing that the concerted process is under activation control. It is characterized by a remarkably small reorganization energy, in line with the electrochemical counterpart of the reaction, underpinning the very peculiar behavior of water as proton acceptor when it is used as the solvent