École Nationale Supérieure de Chimie de Rennes

The conformational properties and intrinsic reactivity of unsaturated CH2=C(R)XH systems (R = -H, -CH=CH2, -C≡CH, -C≡N, -Cl, -phenyl, -cyclopentadienyl, -pyrrole; X = O, S, Se)-namely enols, enethiols, and eneselenols-have been investigated using G4 and CCSD(T) calculations. All compounds exhibit antiperiplanar (ap) and anticlinal (ac)-conformers that are nearly isoenergetic, as their relative stabilities are governed by subtle noncovalent interactions, which are analyzed in detail. Both conformers are therefore expected to coexist in the gas phase, and because the rotational barriers are very low, their interconversion is effectively barrierless under typical conditions. In contrast, the corresponding protonated species display significantly higher barriers, approximately three to five times larger. The keto-enol tautomerization involves activation barriers exceeding 180 kJ·mol-1, confirming that, as in other keto-enol rearrangements, the process is not monomolecular. Protonation generally occurs at the methylene carbon, with the exceptions of the -C≡CH and -C≡N derivatives. Strong linear correlations are found among the proton affinities of the three families studied, which follow the trend: enols > enethiols > eneselenols. All systems behave as strong carbon bases; some are predicted to be 20-21 orders of magnitude more basic than ketene and 3-5 orders of magnitude more basic than vinylimine in terms of equilibrium constants. Deprotonation preferentially occurs at the X-H group in nearly all cases. The only exception is the cyclopentadienyl-substituted enol, for which deprotonation of the cyclopentadienyl moiety is favored due to enhanced aromatic stabilization of the resulting anion. Overall, acidity increases along the series O < S < Se.

This study investigated the valorization of green macroalgae in ethanol by the yeast Saccharomyces cerevisiae . The proof of concept was conducted with two green macroalgae hydrolysates, namely Ulva rigida and Chaetomorpha linum and the fermentation process was scaled-up from 250 mL and 500 mL shake flasks to a 3 L stirred-tank bioreactor. Firstly, the experiments used a synthetic medium based on algal hydrolysate, examining factors like nitrogen source, inoculum size, and salt content. After 72 h, ethanol yields were similar across the systems: 0.43 g.g −1 in the bioreactor, compared to 0.46 and 0.45 g.g −1 in 250 mL and 500 mL flasks, respectively. Secondly, fermenting green algae hydrolysate was tested, under similar conditions (without aeration and pH adjustment, with nitrogen enrichment, and 1 % v /v inoculum) resulted in an ethanol concentration of 9.05 g.L −1 , a yield of 0.44 g.g −1 , and 85.86 % efficiency. Thirdly, operating the process at larger scale was carried out on pilot scale of 77 L with Chaetomorpha linum hydrolysate. Glucose was fully consumed in 9 h, and maximum ethanol production (5.61 g.L −1 ) occurred after 11 h, with a yield of 0.52 g.g −1 which corresponds to the theoretical yield. • Green macroalgae as a feedstock for bioethanol production. • Lab-scale trials show bioethanol production potential. • Fermentation is possible without nitrogen supplementation and pH control. • Fermentation is possible without sterilization of the algal hydrolysate.

1-Arsabutadiyne (2-propynylidynearsine, HC3As), is efficiently produced by photolysis of propynylarsine isolated in solid argon. The observed infrared absorption spectra and predicted molecular parameters of HC3As and HC3P show significant similarities, but large differences compared to HC3N.

Pyrite, a ubiquitous sulfide mineral, exerts a strong influence on the fate of coexisting As(III) and As(V) species in natural settings, such as gold deposits, sedimentary basins, and hydrothermal systems. However, the As(III) adsorption and oxidation mechanisms on pyrite at neutral pH remain contested. Through oxic and anoxic kinetic experiments using pyrite with varying oxidation degrees, we demonstrate that As(III) adsorbs preferentially to the Fe(III) (oxy)(hydr)oxide coatings rather than to pyrite sites. Contrary to prevailing assumptions, the HO• radicals contribute minimally to As(III) oxidation at circumneutral pH. Spectroscopy and molecular simulations revealed that pyrite-generated H2O2 oxidizes As(III) via an inner-sphere electron transfer process. This heterogeneous oxidation likely proceeds through a ternary surface complexation involving arsenite and Fe sites. These findings challenge both the conventional radical-dominated pathway and the assumed mechanism of natural arsenopyrite formation. By elucidating the dominant As(III) sorption/oxidation pathway on pyrite surfaces, our findings reshape our current understanding of arsenic geochemistry. They also inform risk assessment and remediation strategies for arsenic-impacted environments.

ABSTRACT Natural and synthetic polycations are commonly used in DNA‐ and RNA‐based transfection for their ability to condense and protect nucleic acids, and the subsequent cellular uptake. While the formation of these complexes is well‐documented, fewer studies have examined their stability under both extracellular and intracellular conditions. Chitosan, a biodegradable natural polysaccharide, has shown promise for gene delivery. However, its pKa of ∼6.5 makes its ionization state highly sensitive to pH fluctuations around this value. In this study, we examined how pH‐induced changes influence the stability of chitosan/peGFP‐C3 complexes and their effects on cell viability, proliferation, and transfection efficiency in HEK293T cells. The highest transfection efficiency was achieved by transfecting the complexes at pH 6.5, followed by a medium replacement at pH 7.1, particularly with high molecular weight chitosans. Cell viability was found to be higher at pH 7.1, whereas acidic conditions (pH 6.5) affected proliferation, leading to S‐phase accumulation, suggesting potential interference with cell cycle progression. These findings underscore the critical role of pH in optimizing gene delivery and maintaining favorable cell growth conditions.