University of Rennes

About: University of Rennes is a education organization based out in Rennes, France. It is known for research contribution in the topics: Population & Crystal structure. The organization has 18404 authors who have published 40374 publications receiving 995327 citations.

Time-Resolved in Situ Studies of Oxygen Intercalation into SrCoO2.5, Performed by Neutron Diffraction and X-ray Absorption Spectroscopy

Abstract: Electrochemical oxidation of the antiferromagnetically ordered SrCoO2.5, with brownmillerite-type structure, to the cubic ferromagnet SrCoO3, with perovskite structure, has been investigated in situ by neutron diffraction as well as by X-ray absorption fine structure (XAFS) spectroscopy in specially designed electrochemical cells. The neutron diffraction experiments were performed twice, using two different wavelengths (λ = 1.2921(2) and 4.74 A) in order to better discriminate structural and magnetic changes as functions of the charge transfer. From the neutron diffraction experiments, two intermediate phases, SrCoO2.75 and SrCoO2.82±0.07, were characterized. No superstructure reflections were observed for the corresponding SrCoO2.75 phase. Instead we observed here, for the first time, 3D oxygen ordering during an oxygen intercalation reaction, as established for SrCoO2.82±0.07, which can be described as a tetragonal unit cell, related to the perovskite cell by a ≈ 2(a√2) and c ≈ 2a. The structure of this...

Pyridine elaboration through organometallic intermediates: regiochemical control and completeness

Abstract: Pyridines carrying heterosubstituents (such as carboxy, amido, amino, alkoxy or trifluoromethyl groups or solely individual halogen atoms) can be readily and site selectively metalated. Subsequent reaction with a suitable electrophile opens rational access to a wealth of new building blocks for the synthesis of biologically active compounds. This approach relies on organometallic methods, which are both efficacious and extremely flexible as far as the substitution site and the product structure are concerned (86 references).

Transgene-Free Genome Editing in Tomato and Potato Plants Using Agrobacterium-Mediated Delivery of a CRISPR/Cas9 Cytidine Base Editor

Abstract: Genome editing tools have rapidly been adopted by plant scientists for gene function discovery and crop improvement. The current technical challenge is to efficiently induce precise and predictable targeted point mutations valuable for crop breeding purposes. Cytidine base editors (CBEs) are CRISPR/Cas9 derived tools recently developed to direct a C-to-T base conversion. Stable genomic integration of CRISPR/Cas9 components through Agrobacterium-mediated transformation is the most widely used approach in dicotyledonous plants. However, elimination of foreign DNA may be difficult to achieve, especially in vegetatively propagated plants. In this study, we targeted the acetolactate synthase (ALS) gene in tomato and potato by a CBE using Agrobacterium-mediated transformation. We successfully and efficiently edited the targeted cytidine bases, leading to chlorsulfuron-resistant plants with precise base edition efficiency up to 71% in tomato. More importantly, we produced 12.9% and 10% edited but transgene-free plants in the first generation in tomato and potato, respectively. Such an approach is expected to decrease deleterious effects due to the random integration of transgene(s) into the host genome. Our successful approach opens up new perspectives for genome engineering by the co-edition of the ALS with other gene(s), leading to transgene-free plants harboring new traits of interest.

Discrete, Solvent-Free Alkaline-Earth Metal Cations: Metal···Fluorine Interactions and ROP Catalytic Activity

Abstract: Efficient protocols for the syntheses of well-defined, solvent-free cations of the large alkaline-earth (Ae) metals (Ca, Sr, Ba) and their smaller Zn and Mg analogues have been designed. The reaction of 2,4-di-tert-butyl-6-(morpholinomethyl)phenol ({LO1}H), 2-{[bis(2-methoxyethyl)amino]methyl}-4,6-di-tert-butylphenol ({LO2}H), 2-[(1,4,7,10-tetraoxa-13-azacyclopentadecan-13-yl)methyl]-4,6-di-tert-butylphenol ({LO3}H), and 2-[(1,4,7,10-tetraoxa-13-azacyclo-pentadecan-13-yl)methyl]-1,1,1,3,3,3-hexafluoropropan-2-ol ({RO3}H) with [H(OEt2)2]+[H2N{B(C6F5)3}2]− readily afforded the doubly acidic pro-ligands [{LO1}HH]+[X]− (1), [{LO2}HH]+[X]− (2), [{LO3}HH]+[X]− (3), and [{RO3}HH]+[X]− (4) ([X]− = [H2N{B(C6F5)3}2]−). The addition of 2 to Ca[N(SiMe3)2]2(THF)2 and Sr[N(SiMe3)2]2(THF)2 yielded [{LO2}Ca(THF)0.5]+[X]− (5) and [{LO2}Sr(THF)]+[X]− (6), respectively. Alternatively, 5 could also be prepared upon treatment of {LO2}CaN(SiMe3)2 (7) with [H(OEt2)2]+[X]−. Complexes [{LO3}M]+[X]− (M = Zn, 8; Mg, 9; Ca, 10; Sr, ...