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Supramolecular assembly allows multiple chemical/bio‐components integrated as one system for cascade biochemical reactions. Herein the graphitic carbon nitrides (g‐C3N4) as photocatalyst trapped in a dipeptide hydrogel covering adenosine triphosphate (ATP) synthase accelerates the photophosphorylation through ATP synthesis. Self‐assembled N‐fluorenylmethoxycarbonyl diphenylalanine (Fmoc‐FF) as nanofibrils to allow g‐C3N4 nanosheets are embedded as a complex Fmoc‐FF/g‐C3N4 hydrogel. Fmoc‐FF gel exhibits good electronic coupling with g‐C3N4, which enables a photo‐induced proton generation. The transmembrane proton gradient can be established by ATP synthase‐lipid reconstituted on the surface of the Fmoc‐FF/g‐C3N4 hydrogel to enhance the ATP synthesis. It indicates that the Fmoc‐FF/g‐C3N4/ATP synthase‐lipid film can possess a longer‐term ATP production capability and allow repeated immersion for sustained ATP production. Such a hydrogel‐supported ATP synthesis platform is achieved by a procedure at a larger scale. [ABSTRACT FROM AUTHOR]

ABSTRACT How bacteria transition into growth arrest as part of stationary phase has been well-studied, but our knowledge of features that help cells to stay alive in the following days and weeks is incomplete. Most studies have used heterotrophic bacteria that are growth-arrested by depletion of substrates used for both biosynthesis and energy generation, making is difficult to disentangle the effects of the two. In contrast, when grown anaerobically in light, the phototrophic bacterium Rhodopseudomonas palustris generates ATP from light via cyclic photophosphorylation, and builds biomolecules from organic substrates, such as acetate. As such, energy generation and carbon utilization are independent from one another. Here, we compared the physiological and molecular responses of R. palustris to growth arrest caused by carbon source depletion in light (energy-replete) and dark (energy-depleted) conditions. Both sets of cells remained viable for 6 to 10 days, at which point dark-incubated cells lost viability, whereas light-incubated cells remained fully viable for 60 days. Dark-incubated cells were depleted in intracellular ATP prior to losing viability, suggesting that ATP depletion is a cause of cell death. Dark-incubated cells also shut down measurable protein synthesis, whereas light-incubated cells continued to synthesize proteins at low levels. Cells incubated in both conditions continued to transcribe genes. We suggest that R. palustris may completely shut down protein synthesis in dark, energy-depleted, conditions as a strategy to survive the nighttime hours of day/night cycles it experiences in nature, where there is a predictable source of energy in the form of sunlight only during the day. IMPORTANCE The molecular and physiological basis of bacterial longevity in growth arrest is important to investigate for several reasons. Such investigations could improve treatment of chronic infections, advance use of non-growing bacteria as biocatalysts to make high yields of value-added products, and improve estimates of microbial activities in natural habitats, where cells are often growing slowly or not at all. Here, we compared survival of the phototrophic bacterium Rhodopseudomonas palustris under conditions where it generates ATP (incubation in light), and where it does not generate ATP (incubation in dark) to directly assess effects of energy depletion on long-term viability. We found that ATP is important for long-term survival over weeks. However, R. palustris survives 12 h periods of ATP depletion without loss of viability, apparently in anticipation of sunrise and restoration of its ability to generate ATP. Our work suggests that cells respond to ATP depletion by shutting down protein synthesis.

I present here a personal reminiscence of the life and research of Frederick Robert (Bob) Whatley (January 26, 1924-November 14, 2020). He was responsible for showing that chloroplasts are complete units for oxygenic photosynthesis and that 'photophosphorylation' is what is common between anoxygenic and oxygenic photosynthesis. He had an innovative nature and exploited many biophysical and biochemical techniques to understand, in depth, the regulatory nature of photosynthesis. Bob Whatley was a self-sufficient, thorough, quiet, and confident scientist, but he was 'self-effacing' and never ever "blew his own horn". My presentation is mingled a bit, at places, with my own thoughts -- to give it a 'personal' touch. [ABSTRACT FROM AUTHOR]

We studied bicarbonate-induced stimulation of photophosphorylation in thylakoids isolated from leaves of Arabidopsis thaliana plants. This stimulation was not observed in thylakoids of wild-type in the presence of mafenide, a soluble carbonic anhydrase inhibitor, and was absent in thylakoids of two mutant lines lacking the gene encoding alpha carbonic anhydrase 5 (αCA5). Using mass spectrometry, we revealed the presence of αCA5 in stromal thylakoid membranes of wild-type plants. A possible mechanism of the photophosphorylation stimulation by bicarbonate that involves αCA5 is proposed.

We studied bicarbonate-induced stimulation of photophosphorylation in thylakoids isolated from leaves of Arabidopsis thaliana plants. This stimulation was not observed in thylakoids of wild-type in the presence of mafenide, a soluble carbonic anhydrase inhibitor, and was absent in thylakoids of two mutant lines lacking the gene encoding alpha carbonic anhydrase 5 (αCA5). Using mass spectrometry, we revealed the presence of αCA5 in stromal thylakoid membranes of wild-type plants. A possible mechanism of the photophosphorylation stimulation by bicarbonate that involves αCA5 is proposed. [ABSTRACT FROM AUTHOR]

The prevailing understanding on the light reaction of oxygenic photosynthesis (photolytic photophosphorylation & NADPH synthesis) considers the vast majority of the diverse pigments, chlorophyll binding proteins (CBPs) and light harvesting complexes (LHCs) as photon-energy relaying facets; only the chlorophyll a couplets at the reaction center of the two photosystems I & II are deemed to serve as photo-excitable electron emitters. Highlighting the historical perspectives involved, we present reasons why this conventional perception is unmet by theoretical foundations, unsupported by molecular awareness on the various pigments and unverified by physiological data available on chloroplasts. Further, we propose a simple diffusible reactive oxygen species (DROS)-based mechanism for correlating the functions of various light harvesting LHCs and CBPs with the reaction centers of Photosystems I & II. The projected hypothesis may also provide a new perspective to photoreception research.

Plant-growth-promoting bacteria (PGPB) are gaining attention as a sustainable alternative to current agrochemicals. This study evaluated the impact of three Bacillus spp. (5PB1, 1PB1, FV46) and one Brevibacillus sp. (C9F) on the important crop tomato (Solanum lycopersicum) using the model cv. 'MicroTom'. The effects of these isolates were assessed on (a) seedlings' growth and vigor, and (b) adult potted plants. In potted plants, several photosynthetic parameters (chlorophylls (a and b), carotenoids and anthocyanins contents, transpiration rate, stomatal conductance, net CO2 photosynthetic rate, and intercellular CO2 concentration, and on chlorophyll fluorescence yields of light- and dark-adapted leaves)), as well as soluble sugars and starch contents, were quantified. Additionally, the effects on redox status were evaluated. While the growth of seedlings was, overall, not influenced by the strains, some effects were observed on adult plants. The Bacillus safensis FV46 stimulated the content of pigments, compared to C9F. Bacillus zhangzhouensis 5PB1 increased starch levels and was positively correlated with some parameters of the photophosphorylation and the gas exchange phases. Interestingly, Bacillus megaterium 1PB1 decreased superoxide (O2-) content, and B. safensis FV46 promoted non-enzymatic antioxidant defenses, increasing total phenol content levels. These results, conducted on a model cultivar, support the theory that these isolates differently act on tomato plant physiology, and that their activity depends on the age of the plant, and may differently influence photosynthesis. It would now be interesting to analyze the influence of these bacteria using commercial cultivars. [ABSTRACT FROM AUTHOR]

Textbooks of biochemistry will explain that the otherwise endergonic reactions of ATP synthesis can be driven by the exergonic reactions of respiratory electron transport, and that these two half-reactions are catalyzed by protein complexes embedded in the same, closed membrane. These views are correct. The textbooks also state that, according to the chemiosmotic coupling hypothesis, a (or the) kinetically and thermodynamically competent intermediate linking the two half-reactions is the electrochemical difference of protons that is in equilibrium with that between the two bulk phases that the coupling membrane serves to separate. This gradient consists of a membrane potential term Δψ and a pH gradient term ΔpH, and is known colloquially as the protonmotive force or pmf. Artificial imposition of a pmf can drive phosphorylation, but only if the pmf exceeds some 150-170 mV; to achieve in vivo rates the imposed pmf must reach 200 mV. The key question then is 'does the pmf generated by electron transport exceed 200 mV, or even 170 mV?' The possibly surprising answer, from a great many kinds of experiment and sources of evidence, including direct measurements with microelectrodes, indicates it that it does not. Observable pH changes driven by electron transport are real, and they control various processes; however, compensating ion movements restrict the Δψ component to low values. A protet-based model, that I outline here, can account for all the necessary observations, including all of those inconsistent with chemiosmotic coupling, and provides for a variety of testable hypotheses by which it might be refined. [ABSTRACT FROM AUTHOR]

Photosynthetic reactions are, so to speak, the source of energy for all organisms on the earth. Thus, ATP synthase of the phototroph is the key enzyme on the reaction process that converts light energy into chemical energy, and is the grand energy conversion system of all photosynthetic organisms. The activity of ATP synthase is finely regulated to ensure that ATP synthesis is carried out continuously and to provide the energy needed for photosynthesis under constantly changing environmental conditions. Since the molecular structure of ATP synthase was elucidated by X-ray crystallography at the end of the 20th century, much progress has been made in understanding the molecular mechanism of ATP synthase catalytic reaction. The active use of cyanobacterial ATP synthase in research has also led to the understanding of photosynthetic ATP synthase at the molecular level. The regulatory mechanism of this enzyme has also been understood at the molecular level over the last 20 years. This review provides an overview of the history of such studies, particularly of the regulation of enzyme activity by the γ subunit and the ɛ subunit. [ABSTRACT FROM AUTHOR]

Highlights • Echophysiological effects of calcium particle films were examined in coffee trees. • The removal of the films was monitored using a colorimeter CR-400. • The coffee trees presented different responses under the shading conditions. • Calcium particle films are promising to promote coffee trees protection. Abstract Conilon coffee (Coffea canephora Pierre ex A. Froehner) is an important agricultural crop in Brazil due to its high economic value. This plant species is sensitive to the effects of high levels of solar radiation and temperature, which could limit its wide cultivation in the Brazilian Northeast region. However, management practices such as shading could increase the feasibility of its cultivation. This study aimed to evaluate the effects of different shading methods and the use of calcium particle films on the conilon coffee ecophysiological parameters in the coastal flatland the State of Sergipe, Brazil. The field experiment was carried out as randomized block design with four treatments: i) Natural shading (intercropping coffee and banana plants), ii) Artificial shading with 10% w/v CaCO 3 particle films; iii) Artificial shading with 20% w/v CaO particle films; and iv) and control (without shading), and four replicates. Measurements were performed 7, 21 and 35 days after film application at 9:00 h and 12:00 h. Individual parameters, gas exchange efficiency, chlorophyll a fluorescence and maintenance of film coverage on leaves were evaluated. Artificial shading with particle films promoted greater physiological stability of the coffee plants during diurnal meteorological oscillations as compared to the control, resulting in higher rates of liquid photosynthesis (A), better control on stomatal conductance (gs) and transpiration (E). Improvement was also observed in the plant water use efficiency (WUE and IWUE) and in the reduction of leaf temperature. Calcium particle films were more efficient in providing protection to the photosystems and improving photochemical efficiency and energy conversion for photophosphorylation than natural shading. However, the results were more pronounced at 21 days after film application and more persistent for treatment with 20% CaO film. Therefore, calcium particle films are useful tools to alleviate coffee plants stress under adverse climate conditions. [ABSTRACT FROM AUTHOR]

Graphical abstract Contrary to biochemistry, a designed system effectively enhances photophosphorylation by photo-induced proton-scavenging through molecular assembly. Abstract At present, photophosphorylation in natural or artificial systems is accomplished by the production of protons or their pumping across the biomembranes. Herein, different from this strategy above, we demonstrate a designed system which can effectively enhance photophosphorylation by photo-induced proton-scavenging through molecular assembly. Upon the introduction of photobase generators, a (photo-) chemical reaction occurs to produce hydroxyl ions. Accompanying the further extramembranous acid-base neutralization reaction, an outbound flow of protons is generated to drive the reconstituted adenosine triphosphate (ATP) synthase to produce ATP. That is, contrary to biochemistry, the proton gradient to drive photophosphorylation derives from the scavenging of protons present in the external medium by hydroxyl ions, produced by the partially photo-induced splitting of photobase generator. Such assembled system holds great potential in ATP-consuming bioapplications. [ABSTRACT FROM AUTHOR]

Prototypes of natural biosystems provide opportunities for artificial biomimetic systems to break the limits of natural reactions and achieve output control. However, mimicking unique natural structures and ingenious functions remains a challenge. Now, multiple biochemical reactions were integrated into artificially designed compartments via molecular assembly. First, multicompartmental silica nanoparticles with hierarchical structures that mimic the chloroplasts were obtained by a templated synthesis. Then, photoacid generators and ATPase‐liposomes were assembled inside and outside of silica compartments, respectively. Upon light illumination, protons produced by a photoacid generator in the confined space can drive the liposome‐embedded enzyme ATPase towards ATP synthesis, which mimics the photophosphorylation process in vitro. The method enables fabrication of bioinspired nanoreactors for photobiocatalysis and provides insight for understanding sophisticated biochemical reactions. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Enzyme activity of PSB wastewater treatment were studied for the first time. • Oxygen was beneficial for COD degradation and detrimental for PSB growth. • Oxygen promoted PFK and PK activity and inhibited RuBisCO activity. • PFK and PK worked in COD degradation and RuBisCO and HK worked in PSB growth. Abstract Photosynthetic bacteria (PSB) wastewater treatment is a novel method that can simultaneously achieve wastewater purification and recourse recovery. Oxygen conditions can significantly influence PSB metabolism and wastewater treatment; however, the roles of key enzymes in this process have been unclear. This study investigated the effects of different oxygen conditions on respiratory enzymes (hexokinase, HK; phosphofructokinase, PFK; and pyruvate kinase, PK) and the photosynthetic enzyme RuBisCO of PSB. The results showed that HK activity was almost the highest under anaerobic condition; PFK activity was the highest (311 nmol/min∙g) and PK the most quickly reached its peak under aerobic condition; and RuBisCO activity was the highest (107 nmol/min g) under anaerobic condition. The above results illustrated that HK might simultaneously regulate PSB growth and COD degradation, and its main role might be PSB growth regulation. PFK and PK might function in COD degradation while RuBisCO might function in PSB growth. Further, oxygen was beneficial for COD degradation and detrimental for PSB growth. This study provides a theoretical basis for the development of PSB wastewater treatment. [ABSTRACT FROM AUTHOR]

Chickpea is a grain legume that enhances soil fertility and represents an important source of green proteins for human health. It is typically cultivated in marginal areas with limited water availability. The aim of this study was to shed light into the molecular mechanisms of drought tolerance of this legume. First, the physiological response of nine stable genotype lines in control and drought-stress conditions was assessed. Two of these genotypes (Desi PI5980808 and Kabuli Flip07 318 C) showed opposite physiological responses to drought stress. Desi PI5980808 displayed a reduced chlorophyll content and an unaltered concentration of osmolytes (proline and soluble sugars) under drought stress. Kabuli Flip07 318 C did not show any reduction in photosynthesis and chlorophyll content, but a significant increase of proline and soluble sugars was observed under the drought stress. To identify genes and molecular mechanisms involved in drought tolerance, RNA-seq was performed in control conditions and after one week of drought stress in these two contrasting genotypes. The genotype with higher drought sensitivity showed more intense changes in gene expression than the genotype with less sensitivity, up-regulating genes involved in photophosphorylation process (transferases, oxygen lyases and oxidoreductases), hormones (brassinosteroids, abscisic acid and gibberellin response), solute transporters, nutrient uptake, and cell wall properties (cellulose synthases, hemicellulose synthases, poligalacturonases, pectate lyases). Small number of up-regulated genes in the genotype with lower drought sensitivity included those involved in chromatin modifications. These results will be helpful for further studies aiming at identifying genes and molecular markers to be used in breeding strategies to develop chickpea cultivars more resilient to water stress. [Display omitted] • Osmolites and chlorophyll content were linked to drought tolerance. • Phosphorylation processes were induced in drought-sensitive genotype. • Brassinosteroid genes are linked to drought responses. • Genes involved in chromatin modifications were induced in tolerant genotype. • Drought modulates cell wall and transport-related genes. [ABSTRACT FROM AUTHOR]

Amplification of fibroblast growth factor receptor2 (FGFR2) has been regarded as a druggable target in gastric cancer (GC). Despite known potential of AZD4547, a selective inhibitor of FGFR 1–3, to suppress tumorigenic effects of activated FGFR2, resistance to the targeted agent has been an unresolved issue. This study was performed to elucidate the mechanism of AZD4547 resistance in GC cells. SNU-16 cells were used to establish an AZD4547-resistant GC cell line, SNU-16R. Elevated phosphorylation of EphB3 was confirmed using the Human Phospho-Receptor Tyrosine Kinase Array kit. A tyrosine kinase inhibitor (TKI) of EphB3 was used to investigate the effects of suppressed EphB3 activity in the SNU-16R cell line. SNU-16R cells exhibited upregulated phosphorylation of EphB3. Treatment of SNU-16R cells with the EphB3 TKI resulted in induction of apoptosis, decreased cellular viability, and cell cycle arrest at sub-G1 phase. SNU-16R cells expressed upregulated levels of N-cadherin, vimentin, Snail, matrix metalloproteinase 2 (MMP-2), and MMP-9, and reduced levels of E-cadherin, characteristic of epithelial to mesenchymal transition (EMT). Matrigel invasion assay also demonstrated the increased invasiveness of SNU-16R cells. EphB3 TKI treatment inhibited EMT of SNU-16R cells. Activation of mammalian target of rapamycin (mTOR) through the Ras-ERK1/2 pathway was suggested as the signal transduction mechanism downstream EphB3 by showing enhanced phosphorylation of Raf-1, MEK1/2, ERK1/2, mTOR and its downstream substrates in SNU-16R cells. As expected, EphB3 TKI decreased phosphorylation of these proteins. Our data suggest phosphorylation of mTOR through signaling by EphB3 is a potential mechanism of AZD4547 resistance in GC cells. [ABSTRACT FROM AUTHOR]

The gene cycA encodes a periplasmic protein, cytochrome c 2 (cyt c 2 ), which dominates electron transfer from the membrane-bound ubiquinol: cyt c 2 oxidoreductase (cyt bc 1 ) to the photosynthetic reaction center, contributing to the production of transmembrane proton potential and then the synthesis of ATP. For photosynthetic bacteria, the total energy supply for light anaerobic growth and hydrogen production comes from photophosphorylation. As a result, the key protein encoding gene plays an important role in hydrogen production. To figure out the specific effect of cycA expression level on H 2 production ability of Rhodobacter sphaeroides HY01, cycA -expression plasmids derived from pRK415 and pBBR1MCS-2 were constructed and then crossed into the parent strain R. sphaeroides HY01 for H 2 production test. And further verification by RT-PCR suggested that there was about 20% enhancement of cycA expression level by pBBR1MCS-2 where the H 2 production performance of corresponding strain was improved by 6–8% compared with blank control. In contrast, cycA expression level was about 3.4 folds by vector pRK415 compared with control strain, but corresponding strains showed slightly depressed H 2 production performance. Besides, the mutant XJ01 with cycA gene overexpressing by 70% in the genome of HY01( hupSL : cycA ) also showed positive effect on hydrogen production performance. The results demonstrated that slightly overexpression of cycA could enhance the hydrogen production rate, but too much higher level of cycA -expression could show negative effect on H 2 production performance of R. sphaeroides HY01. [ABSTRACT FROM AUTHOR]

Abstract: A natural–artificial hybrid system was constructed to enhance photophosphorylation. The system comprises chloroplasts modified with optically matched quantum dots (chloroplast–QD) with a large Stokes shift. The QDs possess a unique optical property and transform ultraviolet light into available and highly effective red light for use by chloroplasts. This favorable feature enables photosystem II contained within the hybrid system to split more water and produce more protons than chloroplasts would otherwise do on their own. Consequently, a larger proton gradient is generated and photophosphorylation is improved. At optimal efficiency activity increased by up to 2.3 times compared to pristine chloroplasts. Importantly, the degree of overlap between emission of the QDs and absorption of chloroplasts exerts a strong influence on the photophosphorylation efficiency. The chloroplast–QD hybrid presents an efficient solar energy conversion route, which involves a rational combination of a natural system and an artificial light‐harvesting nanomaterial. [ABSTRACT FROM AUTHOR]

Adeno-associated virus (AAV) is a small human Dependovirus whose low immunogenicity and capacity for long-term persistence have led to its widespread use as vector for gene therapy. Despite great recent successes in AAV-based gene therapy, further improvements in vector technology may be hindered by an inadequate understanding of various aspects of basic AAV biology. AAV is unique in that its replication is largely dependent on a helper virus and cellular factors. In the absence of helper virus coinfection, wild-type AAV establishes latency through mechanisms that are not yet fully understood. Challenging the currently held model for AAV latency, we show here that the corepressor Krüppel-associated box domain-associated protein 1 (KAP1) binds the latent AAV2 genome at the rep ORF, leading to trimethylation of AAV2-associated histone 3 lysine 9 and that the inactivation of KAP1 repression is necessary for AAV2 reactivation and replication. We identify a viral mechanism for the counteraction of KAP1 in which interference with the KAP1 phosphatase protein phosphatase 1 (PP1) by the AAV2 Rep proteins mediates enhanced phosphorylation of KAP1-S824 and thus relief from KAP1 repression. Furthermore, we show that this phenomenon involves recruitment of the NIPP1 (nuclear inhibitor of PP1)-PP1α holoenzyme to KAP1 in a manner dependent upon the NIPP1 FHA domain, identifying NIPP1 as an interaction partner for KAP1 and shedding light on the mechanism through which PP1 regulates cellular KAP1 activity. [ABSTRACT FROM AUTHOR]

Abstract: Molecular assembly offers a bottom‐up way to construct biomimetic architectures with unique structures and properties. Although artificial photophosphorylation systems have long been developed, their microstructures have yet to achieve the sophisticated order and hierarchy of natural organisms. Herein, by utilizing principles in the natural plant leaves, it is shown that a biomimetic system with hierarchically ordered and compartmentalized structures, combining photosystem II (PSII) and adenosine triphosphate (ATP) synthase, can be obtained through template‐directed layer‐by‐layer assembly. Under light illumination, PSII in such a highly ordered light‐harvesting array, splits water to produce protons and electrons. Furthermore, a remarkable proton gradient is created across the covering ATP synthase‐reconstituted lipid membrane. As a consequence, highly efficient photophosphorylation is achieved. Outstandingly, the rate of ATP production in this hierarchical light‐harvesting architecture is enhanced 14 times, compared to that in the nature. This study paves a new way to assemble bioinspired systems with enhanced solar‐to‐chemical energy conversion efficiency. [ABSTRACT FROM AUTHOR]

Under optimal conditions, most of the light energy is used to drive electron transport. However, when the light energy exceeds the capacity of photosynthesis, the overall photosynthetic efficiency drops down. The present study investigated the effects of high light on rice photooxidation-prone mutant 812HS, characterized by a mutation of leaf photooxidation 1 gene, and its wild type 812S under field conditions. Our results showed no significant difference between 812HS and 812S before exposure to high sunlight. However, during exposure to high light, shoot tips of 812HS turned yellow and their chlorophyll (Chl) content decreased. Transmission electron microscopy showed that photooxidation resulted in significant damage of chloroplast ultrastructure. It was confirmed also by inhibited photophosphorylation and reduced ATP content. The decreased coupling factor of ATP, Ca-ATPase and Mg-ATPase activities also verified these results. Further, significantly enhanced activities of antioxidative enzymes were observed during photooxidation. Malondialdehyde, hydrogen peroxide, and the superoxide generation rates also increased. Chl a fluorescence analysis found that the performance index and maximum quantum yield of PSII declined on August 4, 20 days after high-light treatment. Net photosynthetic rate also decreased and substomatal CO concentration increased in 812HS at the same time. In conclusion, our findings indicated that excessive energy triggered the production of toxic reactive oxygen species and promoted lipid peroxidation in 812HS plants, causing severe damage to cell membranes, degradation of photosynthetic pigments and proteins, and ultimately inhibition of photosynthesis. [ABSTRACT FROM AUTHOR]

Enhancing solar energy conversion efficiency is very important for developing renewable energy, protecting the environment, and producing agricultural products. Efficient enhancement of photophosphorylation is demonstrated by coupling artificial photoacid generators (PAGs) with chloroplasts. The encapsulation of small molecular long-lived PAGs in the thylakoid lumen is improved greatly by ultrasonication. Under visible-light irradiation, a fast intramolecular photoreaction of the PAG occurs and produces many protons, remarkably enhancing the proton gradient in situ. Consequently, compared to pure chloroplasts, the assembled natural-artificial hybrid demonstrates approximately 3.9 times greater adenosine triphosphate (ATP) production. This work will provide new opportunities for constructing enhanced solar energy conversion systems. [ABSTRACT FROM AUTHOR]

Chemistry assigns phosphate (Pi) dominant roles in metabolism; however, it also renders the macronutrient a genuinely limiting factor of plant productivity. Pi bioavailability is restricted by low Pi mobility in soil and antagonized by metallic toxicities, which force roots to actively seek and selectively acquire the vital element. During the past few years, a first conceptual outline has emerged of the sensory mechanisms at root tips, which monitor external Pi and transmit the edaphic cue to inform root development. This review highlights new aspects of the Pi acquisition strategy of Arabidopsis roots, as well as a framework of local Pi sensing in the context of antagonistic interactions between Pi and its major associated metallic cations, Fe 3+ and Al 3+ . [ABSTRACT FROM AUTHOR]

We present here our tribute to an outstanding unique scientist, a pioneer of plant biochemistry, best known for his seminal ground-breaking discoveries related to electron and proton transport, and their intimate relation to ATP synthesis in chloroplasts. His dedication and in-depth understanding of science was matched by his humor. Here, we offer a modest précis of his life and research. We have also included Reminiscences from: Leonard Fish, Eric Larson, Donald Ort, Thomas Owens, and Robert Turgeon. [ABSTRACT FROM AUTHOR]

To investigate the effects of Nitrogen (N):phosphorus (P) ratio and solar ultraviolet radiation (UVR) on the growth and photophosphorylation of oceanic phytoplankton, the effects of UVR and N:P ratio on K. mikimotoi were evaluated. K. mikimotoi cells were cultured in artificial seawater (ASW) under five different N:P ratios (1:1, 16:1, 50:1, 100:1 and 200:1) for 15 days (phase 1: 1-5 day; phase 2: 6-10 day; phase 3: 11-15 days). Next, K. mikimotoi cultures were exposed to photosynthetically active radiation (PAR), PAB (PAR + UV-A + UV-B) and PA (PAR + UV-A), respectively. Finally, K. mikimotoi cells grown under the Redfield ratio (16:1) had the largest growth rate (0.257day), highest pigment concentrations (chlorophyll a (Chla): 0.465 × 10 μg cell, carotenoid (Caro): 0.249 × 10 μg cell) and maximum superoxide dismutase (SOD) activity (0.9 U × 10 cell) compared with those grown under other N:P ratios. The UV-absorbing compounds' (UV) absorbance was largest at the N:P ratio of 50:1 during the range of 310-360 nm, with a relatively higher value at the N:P ratio of 16:1. UV intensity was positively correlated with photoinhibition. K. mikimotoi cells grown at the N:P ratio of 16:1 showed the smallest photoinhibition compared to those grown at other N:P ratios under the PAR treatment with the largest r:k ratio; similar results were found for both the PA and PAB treatments. The Redfield ratio of 16:1 is optimal for the growth and photophosphorylation of K. mikimotoi. The weakest UVR-induced photoinhibition at this ratio may be attributed to the highest photosystem II (PSII) repair rate and SOD activity. [ABSTRACT FROM AUTHOR]

As the chief energy source of eukaryotic cells, it is important to determine the thermodynamic efficiency of ATP synthesis in oxidative phosphorylation (OX PHOS). Previous estimates of the thermodynamic efficiency of this vital process have ranged from Lehninger's original back-of-the-envelope calculation of 38% to the often quoted value of 55–60% in current textbooks of biochemistry, to high values of 90% from recent information theoretic considerations, and reports of realizations of close to ideal 100% efficiencies by single molecule experiments. Hence this problem has been reinvestigated from first principles. The overall thermodynamic efficiency of ATP synthesis in the mitochondrial energy transduction OX PHOS process has been found to lie between 40 and 41% from four different approaches based on a) estimation using structural and biochemical data, b) fundamental nonequilibrium thermodynamic analysis, c) novel insights arising from Nath's torsional mechanism of energy transduction and ATP synthesis, and d) the overall balance of cellular energetics. The torsional mechanism also offers an explanation for the observation of a thermodynamic efficiency approaching 100% in some experiments. Applications of the unique, molecular machine mode of functioning of F 1 F O -ATP synthase involving direct inter-conversion of chemical and mechanical energies in the design and fabrication of novel, man-made mechanochemical devices have been envisaged, and some new ways to exorcise Maxwell's demon have been proposed. It is hoped that analysis of the fundamental problem of energy transduction in OX PHOS from a fresh perspective will catalyze new avenues of research in this interdisciplinary field. [ABSTRACT FROM AUTHOR]

Excited flavin molecules can photocatalyze reactions, leading to the accumulation of free energy in the products, and the data accumulated through biochemical experiments and by modeling prebiological processes suggest that flavins were available in the earliest stages of evolution. Furthermore, model experiments have shown that abiogenic flavin conjugated with a polyamino acid matrix, a pigment that photocatalyzes the phosphorylation of ADP to form ATP, could have been present in the prebiotic environment. Indeed, excited flavin molecules play key roles in many photoenzymes and regulatory photoreceptors, and the substantial structural differences between photoreceptor families indicate that evolution has repeatedly used flavins as chromophores for photoreceptor proteins. Some of these photoreceptors are equipped with a light-harvesting antenna, which transfers excitation energy to chemically reactive flavins in the reaction center. The sum of the available data suggests that evolution could have led to the formation of a flavin-based biological converter to convert light energy into energy in the form of ATP.

How bacteria transition into growth arrest as part of stationary phase has been well-studied, but our knowledge of features that help cells to stay alive in the following days and weeks is incomplete. Most studies have used heterotrophic bacteria that are growth-arrested by depletion of substrates used for both biosynthesis and energy generation, making is difficult to disentangle the effects of the two. In contrast, when grown anaerobically in light, the phototrophic bacterium Rhodopseudomonas palustris generates ATP from light via cyclic photophosphorylation, and builds biomolecules from organic substrates, such as acetate. As such, energy generation and carbon utilization are independent from one another. Here, we compared the physiological and molecular responses of R. palustris to growth arrest caused by carbon source depletion in light (energy-replete) and dark (energy-depleted) conditions. Both sets of cells remained viable for 6 to 10 days, at which point dark-incubated cells lost viability, whereas light-incubated cells remained fully viable for 60 days. Dark-incubated cells were depleted in intracellular ATP prior to losing viability, suggesting that ATP depletion is a cause of cell death. Dark-incubated cells also shut down measurable protein synthesis, whereas light-incubated cells continued to synthesize proteins at low levels. Cells incubated in both conditions continued to transcribe genes. We suggest that R. palustris may completely shut down protein synthesis in dark, energy-depleted, conditions as a strategy to survive the nighttime hours of day/night cycles it experiences in nature, where there is a predictable source of energy in the form of sunlight only during the day. IMPORTANCE The molecular and physiological basis of bacterial longevity in growth arrest is important to investigate for several reasons. Such investigations could improve treatment of chronic infections, advance use of non-growing bacteria as biocatalysts to make high yields of value-added products, and improve estimates of microbial activities in natural habitats, where cells are often growing slowly or not at all. Here, we compared survival of the phototrophic bacterium Rhodopseudomonas palustris under conditions where it generates ATP (incubation in light), and where it does not generate ATP (incubation in dark) to directly assess effects of energy depletion on long-term viability. We found that ATP is important for long-term survival over weeks. However, R. palustris survives 12 h periods of ATP depletion without loss of viability, apparently in anticipation of sunrise and restoration of its ability to generate ATP. Our work suggests that cells respond to ATP depletion by shutting down protein synthesis.