Arkema (France)

ABSTRACT Polyketide biosynthesis relies on the conformational adaptability of type II polyketide synthases and accessory enzymes, which direct chain folding and regiospecific cyclization. The aromatase/cyclase TcmN from Streptomyces glaucescensis catalyzes the first two ring closures of tetracenomycin C. Still, the molecular basis by which conformational dynamics regulate substrate binding and product release remains unresolved. Understanding how conformational transitions control ligand recognition and prevent aggregation is crucial for deciphering the molecular bases of polyketide biosynthesis and for guiding engineering strategies to synthesize novel natural products. Here, we investigated how ligand interactions modulate the conformational equilibrium of TcmN and the mechanistic consequences for catalysis. Using NMR spectroscopy (STD, CSP, relaxation dispersion), calorimetry, molecular docking, and microsecond-scale molecular dynamics simulations, we mapped the conformational ensembles of apo TcmN and its complexes with naringenin (a substrate/product analogue) and intermediate 12 (INT12). Apo TcmN samples both open and closed conformations. Naringenin preferentially stabilizes the closed state, a conformation thought to protect hydrophobic residues from solvent exposure. In contrast, INT12 shifts the equilibrium toward the open state, characterized by an expanded cavity that permits substrate entry, product release, and accommodation of extended intermediates. Hydrogen-bond analysis highlighted conserved catalytic residues (R82, E34, Q110, T133) as key anchors for productive poses. These results establish that TcmN functions through a ligand-gated breathing mechanism, in which successive intermediates selectively tune the cavity volume and shape, balancing catalytic efficiency with protection against aggregation. Conformational adaptability emerges as a central determinant of aromatase/cyclase function, providing molecular insights relevant for polyketide biosynthetic engineering. Graphical Abstract

Background/Objectives: Accurate hydration assessment is critical for optimizing performance and preventing heat-related complications in ultra-endurance athletes. This study evaluated the agreement and reliability between urine reagent strips and refractometry for field-based hydration assessment via urine-specific gravity (USG) in ultra-trail runners. Methods: Thirty-four ultra-trail runners (22 males, 12 females; mean age 43.71 ± 11.50 years) participated during The Coastal Challenge, a 241-km multi-stage ultra-trail competition. Urine samples were collected before and after the first two stages (Stage 1: 41 km, 1071 m elevation; Stage 2: 40 km, 1828 m elevation). USG was measured using semi-quantitative urine reagent strips (Combur10Test M) and a handheld digital refractometer (Palm Abbe™). Agreement was assessed via paired t-tests, Pearson and Spearman correlations, intraclass correlation coefficients, and Bland-Altman plots across four measurement time points. Results: Strong agreement existed between methods with correlation coefficients of 0.92–0.99 (p < 0.01) within the hydration range typical of well-prepared ultra-endurance athletes (USG 1.010–1.020). No significant differences were found between devices at any time point (all p > 0.05). Bland-Altman analyses revealed minimal mean bias (range: −0.002 to +0.001 g/mL) and narrow limits of agreement, with fewer than 5% of values falling outside limits. Both methods detected significant increases in USG from pre- to post-stage (p < 0.01), indicating exercise-induced hypohydration. Conclusions: Semi-quantitative urine reagent strips and handheld refractometers demonstrate strong agreement for hydration assessment in ultra-trail runners under field conditions when not severely hypohydrated, supporting their interchangeable use for practical monitoring.

Light-curing cyanoacrylates are originally proposed in order to build three-dimensional (3D) objects. Various printing techniques are shown in proof-of-concept experiments: digital light processing (DLP), anionic continuous liquid interface polymerization (ACLIP), and volumetric 3D printing. To the best of our knowledge, this is the first case of light-induced anionic 3D printing of cyanoacrylates. Key unique selling propositions of that choice of resin are outlined: (i) tack-free polymers (no oxygen inhibition), (ii) fast postprocessing with low irradiance LEDs, (iii) thermoplastic polymers vs usual thermosets, and (iv) extremely fast propagation constants. Downsides are that printers had to be customized in order to avoid reactivity in the VAT─highlighting the need for printer manufacturers’ collaboration. Resolutions of 500 μm on the z-scale have been observed without using opacifying dyes. This paper paves the way toward light-curing anionic 3D printing. Moreover, the associated chemical mechanisms were investigated by colorimetric and real-time FTIR experiments, as well as quantum mechanical calculations. A mechanism of conversion of radicals to anionic initiating species can be proposed: Free Radical-Promoted Anionic Polymerization (FRPAP) for a very efficient curing of cyanoacrylates upon mild conditions.

Polymeric ferroelectrics are unique for their high pliability, easy fabrication into complicated shapes, and mechanical robustness along with a polar active nature. In the past few years, polymer ferroelectrics have exhibited marked improvements in the electromechanical coupling efficiency, electrostrictive strain, electrocaloric heat-pumping capability. For the first time, the piezoelectric and electromechanical coupling factors of fluorinated alkyne-modified relaxor ferroelectric tetrapolymers have surpassed those of PZT piezoceramics. Additionally, the advances in ferroelectric-based electrocaloric polymers have led to large electrocaloric cooling under ultralow electric fields. Exploiting the high electromechanical and electrocaloric performance of this new class of ferroelectric polymers, we demonstrated recently a self-actuated electrocaloric heat pump. This talk will present recent advancements in the P(VDF-TrFE) based ferroelectric polymers and their device application.