Photosynthetic Energy Conversion Research Articles

Intracellular Gold Nanocluster/Organic Semiconductor Heterostructure for Enhancing Photosynthesis.

Photosynthetic microorganisms, which rely on light-driven electron transfer, store solar energy in self-energy carriers and convert it into bioenergy. Although these microorganisms can operate light-induced charge separation with nearly 100% quantum efficiency, their practical applications are inherently limited by the photosynthetic energy conversion efficiency. Artificial semiconductors can induce an electronic response to photoexcitation, providing additional excited electrons for natural photosynthesis to improve solar conversion efficiency. However, challenges remain in importing exogenous electrons across cell membranes. In this work, we have developed an engineered gold nanocluster/organic semiconductor heterostructure (AuNC@OFTF) to couple the intracellular electron transport chain of living cyanobacteria. AuNC@OFTF exhibits a prolonged excited state lifetime and effective charge separation. The internalized AuNC@OFTF permits its photogenerated electrons to participate in the downstream of photosystem II and construct an oriented electronic highway, which enables a five-fold increase in photocurrent in living cyanobacteria. Moreover, the binding events of AuNC@OFTF established an abiotic-biotic electronic interface at the thylakoid membrane to enhance electron flux and finally furnished nicotinamide adenine dinucleotide phosphate. Thus, AuNC@OFTF can be exploited to spatiotemporally manipulate and enhance the solar conversion of living cyanobacteria in cells, providing an extended nanotechnology for re-engineering photosynthetic pathways.

Lighting the way: Compelling open questions in photosynthesis research.

Photosynthesis - the conversion of energy from sunlight into chemical energy - is essential for life on Earth. Yet there is much we do not understand about photosynthetic energy conversion on a fundamental level: how it evolved and the extent of its diversity, its dynamics, and all the components and connections involved in its regulation. In this commentary, researchers working on fundamental aspects of photosynthesis including the light-dependent reactions, photorespiration, and C4 photosynthetic metabolism pose and discuss what they view as the most compelling open questions in their areas of research.

Solar Azo-Switches for Effective E→Z Photoisomerization by Sunlight.

Natural photoactive systems have evolved to harness broad-spectrum light from solar radiation for critical functions such as light perception and photosynthetic energy conversion. Molecular photoswitches, which undergo structural changes upon light absorption, are artificial photoactive tools widely used for developing photoresponsive systems and converting light energy. However, photoswitches generally need to be activated by light of specific narrow wavelength ranges for effective photoconversion, which limits their ability to directly work under sunlight and to efficiently harvest solar energy. Here, focusing on azo-switches-the most extensively studied photoswitches, we demonstrate effective solar E→Z photoisomerization with photoconversions exceeding 80 % under unfiltered sunlight. These sunlight-driven azo-switches are developed by rendering the absorption of E isomers overwhelmingly stronger than that of Z isomers across a broad ultraviolet to visible spectrum. This unusual type of spectral profile is realized by a simple yet highly adjustable molecular design strategy, enabling the fine-tuning of spectral window that extends light absorption beyond 600 nm. Notably, back-photoconversion can be achieved without impairing the forward solar isomerization, resulting in unique light-reversible solar switches. Such exceptional solar chemistry of photoswitches provides unprecedented opportunities for developing sustainable light-driven systems and efficient solar energy technologies.

Solar Azo‐Switches for Effective E→Z Photoisomerization by Sunlight

AbstractNatural photoactive systems have evolved to harness broad‐spectrum light from solar radiation for critical functions such as light perception and photosynthetic energy conversion. Molecular photoswitches, which undergo structural changes upon light absorption, are artificial photoactive tools widely used for developing photoresponsive systems and converting light energy. However, photoswitches generally need to be activated by light of specific narrow wavelength ranges for effective photoconversion, which limits their ability to directly work under sunlight and to efficiently harvest solar energy. Here, focusing on azo‐switches—the most extensively studied photoswitches, we demonstrate effective solar E→Z photoisomerization with photoconversions exceeding 80 % under unfiltered sunlight. These sunlight‐driven azo‐switches are developed by rendering the absorption of E isomers overwhelmingly stronger than that of Z isomers across a broad ultraviolet to visible spectrum. This unusual type of spectral profile is realized by a simple yet highly adjustable molecular design strategy, enabling the fine‐tuning of spectral window that extends light absorption beyond 600 nm. Notably, back‐photoconversion can be achieved without impairing the forward solar isomerization, resulting in unique light‐reversible solar switches. Such exceptional solar chemistry of photoswitches provides unprecedented opportunities for developing sustainable light‐driven systems and efficient solar energy technologies.

Adaptive modifications in plant sulfur metabolism over evolutionary time.

Sulfur (S) is an essential element for life on Earth. Plants are able to take up and utilize sulfate (SO42-), the most oxidized inorganic form of S compounds on Earth, through the reductive S assimilatory pathway that couples with photosynthetic energy conversion. Organic S compounds are subsequently synthesized in plants and made accessible to animals, primarily as the amino acid methionine. Thus, plant S metabolism clearly has nutritional importance in the global food chain. S metabolites may be part of redox regulation and drivers of essential metabolic pathways as cofactors and prosthetic groups, such as Fe-S centers, CoA, thiamine, and lipoic acid. The evolution of the S metabolic pathways and enzymes reflects the critical importance of functional innovation and diversifications. Here we review the major evolutionary alterations that took place in S metabolism across different scales and outline research directions that may take advantage of understanding the evolutionary adaptations.

Drilling into the physiology, transcriptomics, and metabolomics to enhance insight on Vallisneria denseserrulata responses to nanoplastics and metalloid co-stress

Co-contamination of nanoplastics (NPs) and arsenic (As) in aquatic environments poses a serious threat to the growth of aquatic plants, but the molecular toxicity mechanism leading to this joint effect on submerged macrophytes is still unclear. Here, we investigated the physiological, transcriptomic, metabolomic responses, and organelle changes in submerged macrophyte, Vallisneria denseserrulata (V. denseserrulata), to single/combined exposure to NPs and As. Our results showed that co-exposure alters physiological traits in V. denseserrulata including chlorophyll, sugars, proteins, malondialdehyde, and antioxidant enzymes. The presence of NPs exacerbated As distribution 36.2–47.2% higher than the control in plant tissues, thus enhancing combined pollution to plants. Integration of physiological traits and differentially expressed genes via weighted correlation network analysis implicated stress-responsive candidate modules related to key enzymes, such as ribulose-bisphosphate carboxylase, alanine transaminase, aspartate aminotransferase, phosphofructokinase-1, and phenylalanine ammonia-lyase. Metabolomics profiling identified carbohydrates, amino acids, organic acids, and fatty acids. Conjoint transcriptome and metabolome analysis revealed that photosynthetic systems, energy conversion, and oxidative and antioxidant regulation are the key defensive response mechanisms for V. denseserrulata under NPs-As co-exposure. Taken together, our multi-omics study provided new molecular insights into submerged macrophytes tolerance mechanisms against combined NPs and As toxicity, highlighting potential targets for stress mitigation and biomonitoring in contaminated aquatic ecosystems.

Electrical signals of the plasma membrane and their effect on chlorophyll fluorescence in <i>chara</i> chloroplasts <i>in vivo</i>

Action potentials of plant cells are involved in regulation of many cell processes, such as photosynthesis and cytoplasmic streaming. Excitable cells of characean algae submerged in media with elevated K+ content are able to generate hyperpolarizing electrical responses. This active response of plasma membrane arises upon the passage of inward electric current comparable in extent to natural currents circulating in illuminated Chara internodes. It remains currently unknown whether the hyperpolarizing electrical signals in Chara affect the photosynthetic activity. Here we show that the negative shift of cell membrane potential, which causes the K+ influx into the cytoplasm, is accompanied by a delayed decrease in the effective chlorophyll fluorescence yield (F′) and maximal yield (Fm′) under low background light (12.5 µmol m-2 s-1). The transient changes in F′ and Fm′ were evident under illumination only, which indicates their close relation to photosynthetic energy conversion in chloroplasts. The passage of inward current caused an increase in pH at the cell surface (pHo), which reflects a high H+/OH- conductance of the plasmalemma and points to the decrease in cytoplasmic pH due to H+ entry into the cell. The shifts in pHo arising in response to the first hyperpolarizing pulse disappeared upon repeated stimulations, thus indicating the long-term inactivation of plasmalemmal H+/OH- conductance. Despite the suppression of plasmalemmal H+ fluxes, the hyperpolarizing responses and the analyzed chlorophyll fluorescence changes did not disappear. The results indicate the participation of K+ flows between the outer medium, cytoplasm, and stroma in chloroplast functional changes that are reflected by the dynamics of F′ and Fm′.

Electrical Signals at the Plasma Membrane and Their Influence on Chlorophyll Fluorescence of Chara Chloroplasts in vivo.

Action potentials of plant cells are engaged in the regulation of many cell processes, including photosynthesis and cytoplasmic streaming. Excitable cells of characean algae submerged in a medium with an elevated K+ content are capable of generating hyperpolarizing electrical responses. These active responses of plasma membrane originate upon the passage of inward electric current comparable in strength to natural currents circulating in illuminated Chara internodes. So far, it remained unknown whether the hyperpolarizing electrical signals in Chara affect the photosynthetic activity. Here, we showed that the negative shift of cell membrane potential, which drives K+ influx into the cytoplasm, is accompanied by a delayed decrease in the actual yield of chlorophyll fluorescence F' and the maximal fluorescence yield Fm' under low background light (12.5 µmol m-2 s-1). The transient changes in F' and Fm' were evident only under illumination, which suggests their close relation to the photosynthetic energy conversion in chloroplasts. Passing the inward current caused an increase in pH at the cell surface (pHo), which reflected high H+/OH- conductance of the plasmalemma and indicated a decrease in cytoplasmic pH due to the H+ entry into the cell. The shifts in pHo arising in response to the first hyperpolarizing pulse disappeared upon repeated stimulation, thus indicating the long-term inactivation of plasmalemmal H+/OH- conductance. Suppression of plasmalemmal H+ fluxes did not abolish the hyperpolarizing responses and the analyzed changes in chlorophyll fluorescence. These results suggest that K+ fluxes between the extracellular medium, cytoplasm, and stroma are involved in the functional changes of chloroplasts reflected by transients of F' and Fm'.

Photosynthetic light harvesting and energy conversion.

Photosynthetic light harvesting and energy conversion.

Microalgae-material hybrid for enhanced photosynthetic energy conversion: a promising path towards carbon neutrality.

Photosynthetic energy conversion for high-energy chemicals generation is one of the most viable solutions in the quest for sustainable energy towards carbon neutrality. Microalgae are fascinating photosynthetic organisms, which can directly convert solar energy into chemical energy and electrical energy. However, microalgal photosynthetic energy has not yet been applied on a large scale due to the limitation of their own characteristics. Researchers have been inspired to couple microalgae with synthetic materials via biomimetic assembly and the resulting microalgae-material hybrids have become more robust and even perform new functions. In the past decade, great progress has been made in microalgae-material hybrids, such as photosynthetic carbon dioxide fixation, photosynthetic hydrogen production, photoelectrochemical energy conversion and even biochemical energy conversion for biomedical therapy. The microalgae-material hybrid offers opportunities to promote artificially enhanced photosynthesis research and synchronously inspires investigation of biotic-abiotic interface manipulation. This review summarizes current construction methods of microalgae-material hybrids and highlights their implication in energy and health. Moreover, we discuss the current problems and future challenges for microalgae-material hybrids and the outlook for their development and applications. This review will provide inspiration for the rational design of the microalgae-based semi-natural biohybrid and further promote the disciplinary fusion of material science and biological science.

Engineering Exciton Dynamics with Synthetic DNA Scaffolds.

ConspectusExcitons are the molecular-scale currency of electronic energy. Control over excitons enables energy to be directed and harnessed for light harvesting, electronics, and sensing. Excitonic circuits achieve such control by arranging electronically active molecules to prescribe desired spatiotemporal dynamics. Photosynthetic solar energy conversion is a canonical example of the power of excitonic circuits, where chromophores are positioned in a protein scaffold to perform efficient light capture, energy transport, and charge separation. Synthetic systems that aim to emulate this functionality include self-assembled aggregates, molecular crystals, and chromophore-modified proteins. While the potential of this approach is clear, these systems lack the structural precision to control excitons or even test the limits of their power. In recent years, DNA origami has emerged as a designer material that exploits biological building blocks to construct nanoscale architectures. The structural precision afforded by DNA origami has enabled the pursuit of naturally inspired organizational principles in a highly precise and scalable manner. In this Account, we describe recent developments in DNA-based platforms that spatially organize chromophores to construct tunable excitonic systems. The high fidelity of DNA base pairing enables the formation of programmable nanoscale architectures, and sequence-specific placement allows for the precise positioning of chromophores within the DNA structure. The integration of a wide range of chromophores across the visible spectrum introduces spectral tunability. These excitonic DNA-chromophore assemblies not only serve as model systems for light harvesting, solar conversion, and sensing but also lay the groundwork for the integration of coupled chromophores into larger-scale nucleic acid architectures.We have used this approach to generate DNA-chromophore assemblies of strongly coupled delocalized excited states through both sequence-specific self-assembly and the covalent attachment of chromophores. These strategies have been leveraged to independently control excitonic coupling and system-bath interaction, which together control energy transfer. We then extended this framework to identify how scaffold configurations can steer the formation of symmetry-breaking charge transfer states, paving the way toward the design of dual light-harvesting and charge separation DNA machinery. In an orthogonal application, we used the programmability of DNA chromophore assemblies to change the optical emission properties of strongly coupled dimers, generating a series of fluorophore-modified constructs with separable emission properties for fluorescence assays. Upcoming advances in the chemical modification of nucleotides, design of large-scale DNA origami, and predictive computational methods will aid in constructing excitonic assemblies for optical and computing applications. Collectively, the development of DNA-chromophore assemblies as a platform for excitonic circuitry offers a pathway to identifying and applying design principles for light harvesting and molecular electronics.

Controlling photosynthetic energy conversion by small conformational changes.

Control phenomena in biology usually refer to changes in gene expression and protein translation and modification. In this paper, another mode of regulation is highlighted; we propose that photosynthetic organisms can harness the interplay between localization and delocalization of energy transfer by utilizing small conformational changes in the structure of light-harvesting complexes. We examine the mechanism of energy transfer in photosynthetic pigment-protein complexes, first through the scope of theoretical work and then by in vitro studies of these complexes. Next, the biological relevance to evolutionary fitness of this localization-delocalization switch is explored by in vivo experiments on desert crust and marine cyanobacteria, which are both exposed to rapidly changing environmental conditions. These examples demonstrate the flexibility and low energy cost of this mechanism, making it a competitive survival strategy.

Improving C3 photosynthesis by exploiting natural genetic variation: Hirschfeldia incana as a model species

AbstractDespite research efforts toward improving crop photosynthetic energy conversion efficiencies over the past 40 years, photosynthetic efficiencies remain far from their theoretical maxima. A major challenge has been that plant photosynthesis is a complex process, controlled by many underlying genetic factors and highly dynamic in response to short‐term environmental changes. Recent approaches to improving photosynthesis involved model‐based identification of the bottlenecks in photosynthesis followed by their genetic modification (GM). While these approaches were successful and inspirational, their dependency on the use of GM techniques may restrict their implementation in some jurisdictions. We therefore suggest greater research focus on a different, yet complementary, approach to improving photosynthetic efficiency: the exploration and exploitation of natural genetic variation in photosynthesis. A substantial improvement in phenotyping and genotyping technology over the past decade has highlighted natural variation in photosynthetic sub‐traits for crop and model species. However, a comprehensive understanding of all the factors responsible for photosynthetic limitations is still lacking. We therefore propose the use of high photosynthetic capacity species as models for the exploration of the physiological and genetic basis of high photosynthetic efficiency. While most high photosynthetic capacity species are not suitable as models due to complex genetics and evolutionary distance from crops, we have identified Brassicaceae species Hirschfeldia incana (L.) Lagr.‐Foss as a promising candidate. In this perspective paper, we describe and advocate the use of H. incana as a model for the exploration of high maximum CO2 assimilation rates (Pmax) found in some C3 species. We describe the basic biology and evolutionary history of the species and report preliminary data on its photosynthetic characteristics. Our findings suggest H. incana is an excellent model species for studies aiming at understanding natural genetic variation in photosynthetic efficiency.

Seasonal ecophysiology of Fucus vesiculosus (Phaeophyceae) in the Northern Baltic Sea

ABSTRACT The brown macroalga Fucus vesiculosus is a foundation species in temperate rocky shores, subjected to seasonally fluctuating environmental conditions. To obtain a more complete picture of the seasonality of F. vesiculosus ecophysiology in the northern Baltic Sea, in situ photochemistry, elemental ratios and chlorophyll a and c content of the alga were investigated in field campaigns conducted in different months throughout the year during 2017. Carbon, nitrogen, carbon to nitrogen ratio and chlorophyll a and c content of the alga varied substantially throughout the year, with highest carbon content observed in summer, and highest nitrogen content in winter. C:N ratio in F. vesiculosus apical tissue ranged from 8.6 in February to 48.3 in July. Chlorophyll a and c content followed inversely the seasonal patterns of ambient irradiance. High chlorophyll a and c content in winter was associated with higher maximum photosynthetic efficiency of energy conversion (Fv/Fm), but not with efficiency of photosynthetic energy conversion under light limitation (α). Electron transport rate correlated strongly with seawater temperature, and the highest electron transport rates were observed in summer and correlated with highest internal carbon content of the alga. Redundancy analysis conducted on measured environmental variables against physiological responses identified day of year, temperature and macronutrients in seawater as the most important variables driving the observed seasonal patterns in F. vesiculosus ecophysiology. The results suggest elevated temperatures may increase Fucus growth and photosynthesis rates in the study area. Highlights Two distinct physiological states of Fucus vesiculosus were identified. The most important variables driving responses were season, temperature and macronutrients. Fucus ecophysiology shows substantial seasonality in the northern Baltic Sea.

Estimation of photosynthetic light energy conversion efficiency in winter wheat varieties under drought

Aim. Search for physiological characteristics of high-yielding varieties of winter wheat based on a comparative analysis of efficiency of solar energy conversion into biomass under natural drought during the grain filling period. Methods. Morphometric, actinometric, statistical. Results. It was found that high-yielding varieties of winter wheat had higher, than less productive ones, increment of aboveground dry matter and the radiation use efficiency in the reproductive period of development. A positive correlation was established between the radiation use efficiency of winter wheat varieties at that period and grain yield, and weight of 1000 grains. It has been suggested that the higher efficiency of light energy conversion to biomass at drought conditions in high-yielding varieties may be related to the higher demand for assimilate due to grain filling and high drought-tolerance of photosynthetic apparatus. Conclusions. A significant genotypic difference in the radiation use efficiency between winter wheat varieties of one maturity group at the reproductive period was established. Higher radiation use efficiency in the reproductive period contributed to the increase of grain productivity due to better grain filling, as evidenced by the positive correlation with the mass of 1000 grains. The presence of significant genotypic variability in this trait indicates that it can be used for genetic improvement of wheat productivity. It was found that the varieties of winter wheat Kyivska 17 and Horodnytsia can be used as donors of valuable breeding traits.

MnO2-Modified 3D-Printed Lattice Photo-Bioelectrode for Photosynthetic Energy Conversion from Spinach Thylakoids

Photosynthetic bio-solar energy conversion has been widely investigated as a promising potential in the field of renewable energy due to its high internal quantum efficiency. Thylakoid membranes (TMs) are organelles in chloroplasts where photosynthesis occurs. Once photosynthesis begins photosynthetic electrons (PEs) were generated, and they were transferred via proteins embedded in TMs by sequential redox reactions. To efficiently collect PEs, several approaches were reported to improve electrical connections such as carbon nanotube modified electrode [1], graphene oxide (GO)/TMs composites [2], or ruthenium oxide (RuO2) modified electrode [3]. As another approach, TM-alginate films were electrosprayed on SU-8 micro-pillar electrode to enlarge the electrochemical surface area between TMs and electrode [4]. However, the previous works were still limited in using two-dimensional electrodes with a marginal increase of electrode surface area.In this study, we aimed to maximize the electrochemically-active surface of TM-decorated bioelectrodes using 3D-printed polymeric lattices. We designed an octet-truss lattice structure with a high specific surface area. For the large surface area of the electrode with a high volume fraction, a strut diameter of the lattice was set to be 0.4 mm in the unit cell of an octet-truss lattice with a total length of 2.5 mm. To maximize light transmission, the octet-truss lattice was 3D-printed with a clear resin using stereolithography (SLA). To grant electrical conductivity on the hydrophobic nature of poly(urethane dimethacrylate) resin, poly(dopamine) (PDA) was polymerized as a binder on SLA-printed lattices followed by immersion in the 1.3 wt% of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solution for 30 min. After immersion in PEDOT:PSS solution, PEDOT:PSS coated lattice was gently dried to remove the remaining solution with N2 gun and annealed in a vacuum oven at 120 ℃ for 15 min. On the other hand, the intrinsic electrical conductivity of PEDOT:PSS is lower than 1 S/cm. Therefore, to enhance the conductivity of annealed PEDOT:PSS layer, PEDOT:PSS coated lattice was immersed 5 wt% of ethylene glycol (EG) solution. Then, EG-treated PEDOT:PSS coated lattice was annealed in a vacuum oven as above described. Due to the removal of surplus insulating PSS chains and reorientation of PEDOT chains, the resistance of EG-treated PEDOT:PSS coated lattice was measured thousands of times lower than no treated lattice. A manganese oxide (MnO2) was electrochemically deposited for improved attachment to TMs at 0.5 V vs Ag/AgCl for 2 min. Then, TMs of 1 mg chl/ml were drop-cast on MnO2/PEDOT:PSS/PDA octet-truss lattice electrode. Each intermediate product was carefully analyzed using SEM, optical microscopy, and fluorescence spectroscopy. The PE currents from TM/MnO2/PEDOT:PSS/PDA octet-truss lattice electrode were measured and compared to a flat electrode and with different layers of lattice structures. With 2 layers of TM/MnO2/PEDOT:PSS/PDA octet-truss lattice electrode, the PE currents were increased 4 times compared to PE currents of the flat electrode. Acknowledgement This work was supported by the National Research Foundation of Korea(NRF) Grant funded by the Korean Government(MSIT) (No. 2020R1A2C3013158), and the Human Resources Development program (No.20204030200110) of the Korea Institute of Energy Technology Evaluation and Planning(KETEP) grant funded by the Korea government Ministry of Trade, Industry and Energy.

Diurnal and Seasonal Variations of Photosynthetic Energy Conversion Efficiency of Field Grown Wheat.

Improving canopy photosynthetic light use efficiency and energy conversion efficiency (εc) is a major option to increase crop yield potential. However, so far, the diurnal and seasonal variations of canopy light use efficiency (LUE) and εc are largely unknown due to the lack of an efficient method to estimate εc in a high temporal resolution. Here we quantified the dynamic changes of crop canopy LUE and εc during a day and a growing season with the canopy gas exchange method. A response curve of whole-plant carbon dioxide (CO2) flux to incident photosynthetically active radiation (PAR) was further used to calculate εc and LUE at a high temporal resolution. Results show that the LUE of two wheat cultivars with different canopy architectures at five stages varies between 0.01 to about 0.05 mol CO2 mol–1 photon, with the LUE being higher under medium PAR. Throughout the growing season, the εc varies from 0.5 to 3.7% (11–80% of the maximal εc for C3 plants) with incident PAR identified as a major factor controlling variation of εc. The estimated average εc from tillering to grain filling stages was about 2.17%, i.e., 47.2% of the theoretical maximal. The estimated season-averaged radiation use efficiency (RUE) was 1.5–1.7 g MJ–1, which was similar to the estimated RUE based on biomass harvesting. The large variations of LUE and εc imply a great opportunity to improve canopy photosynthesis for greater wheat biomass and yield potential.

Photobioanodes Based on Nanoimprinted Electrodes and Immobilized Chloroplasts

AbstractAs the global energy demand continues to increase, the interest in photosynthetic energy conversion is growing accordingly. Chloroplasts, photosynthetic organelles present in plants and algae, are attractive candidates for construction of bio solar cells; however, they have been less studied because of their complex membrane system, which restricts electrochemical communication with an electrode surface. Nevertheless, in this work photobioanodes based on planar and nanoimprinted gold substrates modified with chloroplasts were designed and evaluated. Apparently, nanoimprint lithography contributed to higher photocurrent densities, not only owing to the enlarged real surface area, but also due to boosting electrochemical communication between the photosynthetic organelles and the electrode. Combining chloroplast‐modified nanoimprinted gold electrodes with a capacitive part made of a planar gold substrate, coated with a conductive polymer, resulted in a dual‐feature photobioanode providing a lower open‐circuit potential, i. e., −0.11 V vs. Ag|AgCl|KClsat, and an enhanced capacitance of ca. 37 F m−2 upon illumination of 400 W m−2.

Effects of Long-Term Non-Pruning on Main Quality Constituents in 'Dancong' Tea (Camellia sinensis) Leaves Based on Proteomics and Metabolomics Analysis.

‘Dancong’ tea is a famous traditional Oolong tea. In order to keep the original taste of “ancient tea trees”, most of the ‘Dancong’ tea plants are planted in a single plant pattern without pruning. The objective of this study was to explore the effects of long-term non-pruning on main quality constituents in ‘Dancong’ tea. The results showed that the contents of free amino acids, chlorophylls, and floral-honey aromatic substances in tea leaves of unpruned tea plants were higher than those in every year pruned tea plants, while the catechin content in leaves of pruned tea plants was higher than that in leaves of unpruned tea plants. Quantitative proteomics analysis showed that most enzymes involved in biosynthesis of catechins were downregulated in leaves of unpruned tea plants. Five proteins involved in chlorophyll metabolism and 12 proteins related to photosynthesis were upregulated, and the results suggested that higher chlorophyll content and more efficient photosynthetic energy conversion may be important for the higher accumulation of special quality components in leaves of unpruned tea plants. The findings of this study will advance our understanding of the mechanism of formation of different metabolites in leaves of unpruned and pruned tea plants.

Electron Mediation and Photocurrent Enhancement in Dunalliela salina Driven Bio-Photo Electrochemical Cells

In recent years, finding alternatives for fossil fuels has become a major concern. One promising solution is microorganism-based bio-photo electrochemical cells (BPECs) that utilize photosynthetic solar energy conversion as an energy source while absorbing CO2 from the atmosphere. It was previously reported that in cyanobacterial-based BPECs, the major endogenous electron mediator that can transfer electrons from the thylakoid membrane photosynthetic complexes and external anodes is NADPH. However, the question of whether the same electron transfer mechanism is also valid for live eukaryotic microalgae, in which NADPH must cross both the chloroplast outer membrane and the cell wall to be secreted from the cell has remained elusive. In this work, we show that NADPH is also the major endogenous electron mediator in the microalgae Dunalliela salina (Ds). We show that the ability of Ds to tolerate high salinity enables the production of a photocurrent that is 5–6 times greater than previously reported for freshwater cyanobacterial-based BPECs in the presence or absence of exogenous electron mediators. Additionally, we show that the electron mediator Vitamin B1 can also function as an electron mediator enhancing photocurrent production. Finally, we show that the addition of both FeCN and NADP+ to Ds has a synergistic effect enhancing the photocurrent beyond the effect of adding each mediator separately.