Plants use solar energy to power cellular metabolism. The oxidation of plastoquinol and reduction of plastocyanin by cytochrome b ₆ f (Cyt b ₆ f) is known as one of the key steps of photosynthesis, but the catalytic mechanism in the plastoquinone oxidation site (Q _p ) remains elusive. Here, we describe two high-resolution cryo-EM structures of the spinach Cyt b ₆ f homodimer with endogenous plastoquinones and in complex with plastocyanin. Three plastoquinones are visible and line up one after another head to tail near Q _p in both monomers, indicating the existence of a channel in each monomer. Therefore, quinones appear to flow through Cyt b ₆ f in one direction, transiently exposing the redox-active ring of quinone during catalysis. Our work proposes an unprecedented one-way traffic model that explains efficient quinol oxidation during photosynthesis and respiration.

TRNA modifications affect ribosomal elongation speed and co-translational folding dynamics. The Elongator complex is responsible for introducing 5-carboxymethyl at wobble uridine bases (cm⁵U₃₄) in eukaryotic tRNAs. However, the structure and function of human Elongator remain poorly understood. In this study, we present a series of cryo-EM structures of human ELP123 in complex with tRNA and cofactors at four different stages of the reaction. The structures at resolutions of up to 2.9 Å together with complementary functional analyses reveal the molecular mechanism of the modification reaction. Our results show that tRNA binding exposes a universally conserved uridine at position 33 (U₃₃), which triggers acetyl-CoA hydrolysis. We identify a series of conserved residues that are crucial for the radical-based acetylation of U₃₄ and profile the molecular effects of patient-derived mutations. Together, we provide the high-resolution view of human Elongator and reveal its detailed mechanism of action.

In this work a model nanometric manganese–cobalt spinel was deposited on five selected carbon carriers (Vulcan XC-72, Printex85, multiwall carbon nanotubes (MWCNTs), mesoporous carbon CMK-1, and amorphous carbon C-am.) to examine their role in modifying the electrocatalytic properties of the supported active phase for the oxygen reduction reaction (ORR) in alkaline media. The synthesized materials were thoroughly characterized by scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), and Raman spectroscopy (RS). The results confirmed the formation of a highly crystalline nanometric manganese–cobalt spinel and allowed for assessment of an amorphous phase content in the carbon supports used. The composition of the obtained catalysts was investigated by thermogravimetric analysis (TGA) and X-ray fluorescence (XRF) measurements. The electrocatalytic properties of the supported spinels were determined by the rotating disk electrode (RDE) and the rotating ring disk electrode (RRDE) methods and compared with those of a commercial platinum catalyst (20 wt% Pt/Vulcan XC-72). STEM analysis revealed that the carbon support governs both the dispersion and the morphology of the deposited spinel. In the case of mesoporous and amorphous carbon supports, the spinel nanocrystals exhibit a polyhedral shape with almost equal abundance of the (111) and (100) facets. The shape of the spinel nanocrystals deposited on the Vulcan XC-72 and Printex85 supports is dominated by the (111) termination, whereas for the MWCNT support the (100) facet is the most abundant accompanied by the highest dispersion of the nanoparticles. Electrochemical studies of the ORR revealed that the amorphous phase fraction in the carbon support promotes 2e⁻ reduction, leading to production of HO₂ ⁻. This undesired pathway is inhibited by preferential exposition of the (100) facets. The superior performance of the MWCNT support in the 4e⁻ reduction process results from three factors: lowest content of the amorphous component, best dispersion of the spinel active phase, and its ability to promote preferential (100) faceting of the nanocrystals.

Additive manufacturing of Inconel 625 components attracts great interest due to its ability to produce parts with complex geometries that are needed for high-temperature applications in the aerospace, energy, automotive and chemical industries. To take full advantage of the potential of additive manufacturing, an in-depth understanding of the effects of prolonged high-temperature annealing on microstructure and hardness evolution is needed. Previous research in this field has mainly focused on a limited range of temperature and time. This study aims to determine the effect of prolonged high-temperature annealing on the evolution of intermetallic phases and carbides, as well as changes in the dislocation substructure of Inconel 625 superalloy additively manufactured by laser powder bed fusion subjected to stress relief annealing and subsequent isothermal annealing at a temperature up to 800 °C for 5–500 h. The microstructure development is correlated with hardness behaviour. It is determined that the microstructure evolution proceeds in four stages with temperature and time increase. In the initial stress-relieved condition, a cellular microstructure with nano-sized precipitates of the Laves phase and NbC carbides at the cell walls occurs, and hardness is equal to 300 HV10. In the 1st stage of the microstructure evolution, the γ'' phase particles precipitate on the cell walls, which results in hardening up to 383 HV10 in the specimen annealed at 700 °C for 5 h. The 2nd stage involves the precipitation of the γ'' phase both on the cell walls and inside the cells, as well as the formation of dislocation networks, which contribute to the softening effect and hardness drop to 319 HV10. In the 3rd stage, at temperature 700 and 800 °C, the δ phase, M₂₃C₆ carbides, and the Laves phase precipitate and grow, and the subgrain boundaries are formed. The hardness is in the range of 340–350 HV10 and is higher than in the 2nd stage. In the 4th stage, as the annealing time is increased at a temperature of 800 °C, the δ phase and M₂₃C₆ carbides coagulate, and the Laves phase particles spheroidize or partially dissolve. Very intense precipitation and growth of the hard δ phase particles provide an increase in hardness to 402 HV10. As a result of systematic studies, the various strengthening and softening mechanisms acting during high-temperature annealing are determined. Graphical abstract

The effect of the vanadium doping of cryptomelane K_xMn₈O₁₆ nanorods (200 × 10 nm) on bridging the tight-loose contact temperature gap in NO-assisted catalytic soot oxidation was investigated. Catalysts with 0–20% vanadium content were synthesized and characterized in terms of chemical composition, structure, and morphology by means of XRF, XRD, XPS, RS, and TEM/EDX/SAED. Based on three catalyst surface–soot particles contact modes of catalytic measurements (tight contact, loose contact, and contactless), it was found that the incorporation of vanadium into the cryptomelane framework substantially increases the deSoot activity by promoting beneficial NO oxidation into NO₂, with the strongest effect observed for 2.5% vanadium doping. The mechanistic role of NO in the kinetic coupling between ignition, catalytic combustion, and thermal afterburning is revealed, and the role of NO₂ acting as an oxygen carrier from the catalyst to soot particles allows for the rationalization of the observed catalyst performance (lowering the temperature of 50% conversion in loose contacts by ∼100 °C). The results are discussed in terms of the catalyst–soot interface model, where a gradual loss of contact points during the combustion process (passing from tight to loose contacts) is substantially compensated by the in situ generation of NO₂ controlled by the vanadium doping of the cryptomelane nanorods.