Structural Dynamics of the Oxygen-Evolving Complex of Photosystem II in Water-Splitting Action

Comparative analysis of differential gene expression reveals novel insights into the heteroblastic foliage functional traits of Pinus massoniana seedlings

Pinus massoniana needles, rich in medicinal polysaccharides and flavonoids, undergo heteroblastic foliage, transitioning from primary needles (PN) to secondary needles (SN) during growth, resulting in altered functional traits. Despite its significance, the molecular regulatory mechanisms governing these traits remain unclear. This study employs Iso-Seq and RNA-Seq analyses to explore differentially expressed genes (DEGs) associated with functional traits throughout the main growth season of heteroblastic foliage. Co-expression network analysis identified 34 hub genes and 17 key transcription factors (TFs) influencing light-harvesting antenna, photosystem I and II, crucial in photosynthesis regulation. Additionally, 14 genes involved in polysaccharide metabolism pathways, synthesizing sucrose, glucose, UDP sugars, and xylan, along with four genes in flavonoid biosynthesis pathways, regulating p-coumaroyl-CoA, quercetin, galangin, and myricetin production, exhibited differential expression between PN and SN. Further analysis unveils a highly interconnected network among these genes, forming a pivotal cascade of TFs and DEGs. Therefore, heteroblastic changes significantly impact needle functional traits, potentially affecting the pharmacological properties of PN and SN. Thus, these genomic insights into understanding the molecular-level differences of heteroblastic foliage, thereby establishing a foundation for advancements in the pharmaceutical industry related to needle-derived products.

Quantifying the ultrafast and steady-state molecular reduction potential of a plasmonic photocatalyst

Plasmonic materials are promising photocatalysts as they are well suited to convert light into hot carriers and heat. Hot electron transfer is suggested as the driving force in many plasmon-driven reactions. However, to date, there are no direct molecular measures of the rate and yield of plasmon-to-molecule electron transfer or energy of these electrons on the timescale of plasmon decay. Here, we use ultrafast and spectroelectrochemical surface-enhanced Raman spectroscopy to quantify electron transfer from a plasmonic substrate to adsorbed methyl viologen molecules. We observe a reduction yield of 2.4 to 3.5% on the picosecond timescale, with plasmon-induced potentials ranging from [Formula: see text]3.1 to [Formula: see text]4.5 mV. Excitingly, some of these reduced species are stabilized and persist for tens of minutes. This work provides concrete metrics toward optimizing material-molecule interactions for efficient plasmon-driven photocatalysis.

Comparison of photosynthetic responses between haptophyte Phaeocystis globosa and diatom Skeletonema costatum under phosphorus limitation

The diatom Skeletonema costatum and the haptophyte Phaeocystis globosa often form blooms in the coastal waters of the South China Sea. Skeletonema costatum commonly dominates in nutrient enrichment coastal waters, whereas P. globosa starts flourishing after the diatom blooms when phosphorus (P) is limited. Therefore, P limitation was proposed to be a critical factor affecting diatom-haptophyte transition. To elucidate the tolerance to P limitation in P. globosa compared with S. costatum, the effect of P limitation on their photosystem II (PSII) performance was investigated and their photosynthesis acclimation strategies in response to P limitation were evaluated. P limitation did not affect the growth of P. globosa over 7 days but decreased it for S. costatum. Correspondingly, the PSII activity of S. costatum was significantly inhibited by P limitation. The decline in PSII activity in S. costatum under P limitation was associated with the impairment of the oxygen-evolving complex (the donor side of PSII), the hindrance of electron transport from Q_A ^- to Q_B (the acceptor side of PSII), and the inhibition of electron transport to photosystem I (PSI). The 100% decrease in D1 protein level of S. costatum after P limitation for 6 days and PsbO protein level after 2 days of P limitation were attributed to its enhanced photoinhibition. In contrast, P. globosa maintained its photosynthetic activity with minor impairment of the function of PSII. With accelerated PSII repair and highly increased non-photochemical quenching (NPQ), P. globosa can avoid serious PSII damage under P limitation. On the contrary, S. costatum decreased its D1 restoration under P limitation, and the maximum NPQ value in S. costatum was only one-sixth of that in P. globosa. The present work provides extensive evidence that a close interaction exists between the tolerance to P limitation and photosynthetic responses of S. costatum and P. globosa.

Carbon capture and biocatalytic oxygen production of photosystem II from thylakoids and microalgae on nanobiomaterials

Enhanced carbon capture and oxygen production via water splitting was observed by controlling the plasmon-induced resonance energy transfer (PIRET) for photosystem II (PSII) in thylakoid extracts and spirulina assembled on gold nanoparticle (AuNP) dimer arrays. The two types of vertical (V) and horizontal (H) AuNP dimer arrays were uniformly inserted inside pore diameter-controlled templates. Based on the theoretical calculations, the longitudinal mode of the H AuNP dimer array was found to be sensitive to the nanogap distances between the two AuNPs in resonance with the absorption at P680 of the PSII. The longitudinal modes that interacted with P680 of PSII increased from the V to the H conformer. The optical properties from the H AuNP dimer array caused overlapping absorbance and photoluminescence with PSII, and the H AuNP dimer arrays exhibited a significant increase in carbon capture and oxygen generation rates in comparison with those of the bare PSII protein complex under light irradiation via the controlled PIRET process.

Impact of nanoparticles and their ionic counterparts derived from heavy metals on the physiology of food crops

Heavy metals and their engineered nanoparticle (NP) counterparts are emerging contaminants in the environment that have captured the attention of researchers worldwide. Although copper, iron, zinc and manganese are essential micronutrients for food crops, higher concentrations provoke several physiological and biochemical alterations that in extreme cases can lead to plant death. The effects of heavy metals on plants have been studied but the influence of nanoparticles (NPs) derived from these heavy metals, and their comparative effect is less known. In this critical review, we have found similar impacts for copper and manganese ionic and NP counterparts; in contrast, iron and zinc NPs seem less toxic for food crops. Although these nutrients are metals that can be dissociated in water, few authors have conducted joint ionic state and NP assays to evaluate their comparative effect. More efforts are thus required to fully understand the impact of NPs and their ion counterparts at the physiological, metabolic and molecular dimensions in crop plants.

Autologous manganese phosphates with different Mn sites for electrocatalytic water oxidation

Herein, we report two autologous phosphates obtained from the same parent material for electrocatalytic water oxidation. These two phosphates have many similarities except the coordination structure of the Mn centers. It has been straightforwardly observed that the highly asymmetric geometry of Mn2P2O7 can stabilize the active Mn(iii) to promote water oxidation.

A rich catalog of C-C bonded species formed in CO2 reduction on a plasmonic photocatalyst

The understanding and rational design of heterogeneous catalysts for complex reactions, such as CO₂ reduction, requires knowledge of elementary steps and chemical species prevalent on the catalyst surface under operating conditions. Using in situ nanoscale surface-enhanced Raman scattering, we probe the surface of a Ag nanoparticle during plasmon-excitation-driven CO₂ reduction in water. Enabled by the high spatiotemporal resolution and surface sensitivity of our method, we detect a rich array of C₁-C₄ species formed on the photocatalytically active surface. The abundance of multi-carbon compounds, such as butanol, suggests the favorability of kinetically challenging C-C coupling on the photoexcited Ag surface. Another advance of this work is the use of isotope labeling in nanoscale probing, which allows confirmation that detected species are the intermediates and products of the catalytic reaction rather than spurious contaminants. The surface chemical knowledge made accessible by our approach will inform the modeling and engineering of catalysts.

Nanoscale optical imaging in chemistry

Single-molecule-level measurements are bringing about a revolution in our understanding of chemical and biochemical processes. Conventional measurements are performed on large ensembles of molecules. Such ensemble-averaged measurements mask molecular-level dynamics and static and dynamic fluctuations in reactivity, which are vital to a holistic understanding of chemical reactions. Watching reactions on the single-molecule level provides access to this otherwise hidden information. Sub-diffraction-limited spatial resolution fluorescence imaging methods, which have been successful in the field of biophysics, have been applied to study chemical processes on single-nanoparticle and single-molecule levels, bringing us new mechanistic insights into physiochemical processes. However, the scope of chemical processes that can be studied using fluorescence imaging is considerably limited; the chemical reaction has to be designed such that it involves fluorophores or fluorogenic probes. In this article, we review optical imaging modalities alternative to fluorescence imaging, which expand greatly the range of chemical processes that can be probed with nanoscale or even single-molecule resolution. First, we show that the luminosity, wavelength, and intermittency of solid-state photoluminescence (PL) can be used to probe chemical transformations on the single-nanoparticle-level. Next, we highlight case studies where localized surface plasmon resonance (LSPR) scattering is used for tracking solid-state, interfacial, and near-field-driven chemical reactions occurring in individual nanoscale locations. Third, we explore the utility of surface- and tip-enhanced Raman scattering to monitor individual bond-dissociation and bond-formation events occurring locally in chemical reactions on surfaces. Each example has yielded some new understanding about molecular mechanisms or location-to-location heterogeneity in chemical activity. The review finishes with new and complementary tools that are expected to further enhance the scope of knowledge attainable through nanometer-scale resolution chemical imaging.

Metal-Free Catalyst with Large Carbon Defects for Efficient Direct Overall Water Splitting in Air at Room Pressure

Hydrogen can be used as a conventional clean energy resource, only by obtaining it in a cheap, simple, and feasible way. From the perspective of solar energy utilization, photocatalytic water splitting is essentially limited by high electric energy and intermittent solar energy. Here, we demonstrate that the carbon defects could decompose water directly by using low-value mechanical energy in the daily environment without using the sacrificial agent. The prepared metal-free carbon catalyst (OPC-900) with rich graphene topological defects shows several redox states in acetonitrile, which can accumulate redox equivalents and respond for overall water splitting in air at room pressure. Under stirring or light conditions, charges can be created and accumulated on the catalyst surface and split water into H₂ and O₂ in low conductivity medium. The mechanical energy conversion efficiency of stirring in ultrapure water is 7.01%. Our work combines visible light with low-value mechanical energy for widespread decomposition of water to produce hydrogen in air under normal pressure.

Amphiphilic Oxo-Bridged Ruthenium "Green Dimer" for Water Oxidation

In 1982, an oxo-bridged dinuclear ruthenium(III) complex, known as “blue dimer,” was discovered to be active for water oxidation. In this work, a new amphiphilic ruthenium “green dimer” 2, obtained from an amphiphilic mononuclear Ru(bda) (N-OTEG) (L1) (1; N-OTEG = 4-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-pyridine; L1 = vinylpyridine) is reported. An array of mechanistic studies identifies “green dimer” 2 as a mixed valence of Ru^II-O-Ru^III oxo-bridged structure. Bearing the same bda^2- and amphiphilic axial ligands, monomer 1 and green dimer 2 can be reversibly converted by ascorbic acid and oxygen, respectively, in aqueous solution. More importantly, the oxo-bridged “green dimer” 2 was found to take water nucleophilic attack for oxygen evolution, in contrast to monomer 1 via radical coupling pathway for O-O bond formation. This is the first report of an amphiphilic oxo-bridged catalyst, which possesses a new oxygen evolution pathway of Ru-bda catalysts.

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Green dimer (Ru^II-O-Ru^III), referring to “blue dimer” of Ru^III-O-Ru^III, is disclosed

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The first amphiphilic μ-oxido-bridged catalyst is reported active for water oxidation

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The oxo-bridged “green dimer” 2 takes water nucleophilic attack for O-O bond formation

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This is the first Ru-bda catalyst, which possesses a new oxygen evolution pathway

On the comparison between differential vibrational spectroscopy spectra and theoretical data in the carboxyl region of photosystem II

Understanding the structural modification experienced by the Mn₄ CaO₅ oxygen-evolving complex of photosystem II along the Kok-Joliot's cycle has been a challenge for both theory and experiments since many decades. In particular, differential infrared spectroscopy was extensively used to probe the surroundings of the reaction center, to catch spectral changes between different S-states along the catalytic cycle. Because of the complexity of the signals, only a limited quantity of identified peaks have been assigned so far, also because of the difficulty of a direct comparison with theoretical calculations. In the present work, we critically reconsider the comparison between differential vibrational spectroscopy and theoretical calculations performed on the structural models of the photosystem II active site and an inorganic structural mimic. Several factors are currently limiting the reliability of a quantitative comparison, such as intrinsic errors associated to theoretical methods, and most of all, the uncertainty attributed to the lack of knowledge about the localization of the underlying structural changes. Critical points in this comparison are extensively discussed. Comparing several computational data of differential S₂ /S₁ infrared spectroscopy, we have identified weak and strong points in their interpretation when compared with experimental spectra.

Significance of hydrogen bonding networks in the proton-coupled electron transfer reactions of photosystem II from a quantum-mechanics perspective

All quantum-mechanical calculations provide insights into the effect of the hydrogen bonding network on the proton-coupled electron transfer at Y_Z and Y_D in photosystem II.