Bicarbonate activation of the monomeric photosystem II-PsbS/Psb27 complex.

In thylakoid membranes, photosystem II (PSII) monomers from the stromal lamellae contain the subunits PsbS and Psb27 (PSIIm-S/27), while PSII monomers (PSIIm) from granal regions lack these subunits. Here, we have isolated and characterized these 2 types of PSII complexes in tobacco (Nicotiana tabacum). PSIIm-S/27 showed enhanced fluorescence, the near absence of oxygen evolution, and limited and slow electron transfer from QA to QB compared to the near-normal activities in the granal PSIIm.

Near ambient N fixation on solid electrodes versus enzymes and homogeneous catalysts.

The Mo/Fe nitrogenase enzyme is unique in its ability to efficiently reduce dinitrogen to ammonia at atmospheric pressures and room temperature. Should an artificial electrolytic device achieve the same feat, it would revolutionize fertilizer production and even provide an energy-dense, truly carbon-free fuel. This Review provides a coherent comparison of recent progress made in dinitrogen fixation on solid electrodes, homogeneous catalysts and nitrogenases.

Simulating the low-temperature, metastable electrochromism of Photosystem I: Applications to Thermosynechococcus vulcanus and Chroococcidiopsis thermalis.

Low-temperature, metastable electrochromism has been used as a tool to assign pigments in Photosystem I (PS I) from Thermosynechococcus vulcanus and both the white light and far-red light (FRL) forms of Chroococcidiopsis thermalis. We find that a minimum of seven pigments is required to satisfactorily model the electrochromism of PS I. Using our model, we provide a short list of candidates for the chlorophyll f pigment in FRL C.

Impact of energy limitations on function and resilience in long-wavelength Photosystem II.

Photosystem II (PSII) uses the energy from red light to split water and reduce quinone, an energy-demanding process based on chlorophyll a (Chl-a) photochemistry. Two types of cyanobacterial PSII can use chlorophyll d (Chl-d) and chlorophyll f (Chl-f) to perform the same reactions using lower energy, far-red light. PSII from has Chl-d replacing all but one of its 35 Chl-a, while PSII from , a facultative far-red species, has just 4 Chl-f and 1 Chl-d and 30 Chl-a.

Bicarbonate-controlled reduction of oxygen by the Q semiquinone in Photosystem II in membranes.

Photosystem II (PSII), the water/plastoquinone photo-oxidoreductase, plays a key energy input role in the biosphere. [Formula: see text], the reduced semiquinone form of the nonexchangeable quinone, is often considered capable of a side reaction with O, forming superoxide, but this reaction has not yet been demonstrated experimentally. Here, using chlorophyll fluorescence in plant PSII membranes, we show that O does oxidize [Formula: see text] at physiological O concentrations with a of 10 s.

Femtosecond visible transient absorption spectroscopy of chlorophyll--containing photosystem II.

The recently discovered, chlorophyll--containing, far-red photosystem II (FR-PSII) supports far-red light photosynthesis. Participation and kinetics of spectrally shifted far-red pigments are directly observable and separated from that of bulk chlorophyll- We present an ultrafast transient absorption study of FR-PSII, investigating energy transfer and charge separation processes. Results show a rapid subpicosecond energy transfer from chlorophyll- to the long-wavelength chlorophylls- The data demonstrate the decay of an ∼720-nm negative feature on the picosecond-to-nanosecond timescales, coinciding with charge separation, secondary electron transfer, and stimulated emission decay.

[A diagnostic-therapeutic pathway for patients with kidney stone disease: 2020 update].

The natural history of urinary kidney stone disease includes the risk of relapses and can be associated with the risk of chronic kidney disease, bone and cardiovascular disease. For this reason, a wide clinical-metabolic assessment of the kidney stone patient is of great importance since the first presentation of the stone, to set an appropriate preventive treatment. The proposed diagnostic-therapeutic pathway includes a careful medical history, in order to highlight a secondary kidney stone disease and the main risk factors for kidney stones, chronic renal disease, or cardiovascular and bone disease; a metabolic evaluation on multiple levels, according to the severity of the disease, and the presence or absence of risk factors, and appropriate instrumental investigations.

Bicarbonate-Mediated CO Formation on Both Sides of Photosystem II.

The effect of bicarbonate (HCO) on photosystem II (PSII) activity was discovered in the 1950s, but only recently have its molecular mechanisms begun to be clarified. Two chemical mechanisms have been proposed. One is for the electron-donor side, in which mobile HCO enhances and possibly regulates water oxidation by acting as proton acceptor, after which it dissociates into CO and HO.

The primary donor of far-red photosystem II: Chl or P?

Far-red light (FRL) Photosystem II (PSII) isolated from Chroococcidiopsis thermalis is studied using parallel analyses of low-temperature absorption, circular dichroism (CD) and magnetic circular dichroism (MCD) spectroscopies in conjunction with fluorescence measurements. This extends earlier studies (Nurnberg et al 2018 Science 360 (2018) 1210-1213). We confirm that the chlorophyll absorbing at 726 nm is the primary electron donor.

Energetics of the exchangeable quinone, Q, in Photosystem II.

Photosystem II (PSII), the light-driven water/plastoquinone photooxidoreductase, is of central importance in the planetary energy cycle. The product of the reaction, plastohydroquinone (PQH), is released into the membrane from the Q site, where it is formed. A plastoquinone (PQ) from the membrane pool then binds into the Q site.

A low-potential terminal oxidase associated with the iron-only nitrogenase from the nitrogen-fixing bacterium .

The biological route for nitrogen gas entering the biosphere is reduction to ammonia by the nitrogenase enzyme, which is inactivated by oxygen. Three types of nitrogenase exist, the least-studied of which is the iron-only nitrogenase. The Anf3 protein in the bacterium is essential for diazotrophic ( nitrogen-fixing) growth with the iron-only nitrogenase, but its enzymatic activity and function are unknown.

[Nutritional diet therapy in the management of the patient with Chronic Kidney Disease in advanced phase to delay the beginning and reduce the frequency of dialysis. An option also in the pre-emptive transplant program].

The Italian nephrology has a long tradition and experience in the field of dietetic-nutritional therapy (DNT), which is an important component in the conservative management of the patient suffering from a chronic kidney disease, which precedes and integrates the pharmacological therapies. The objectives of DNT include the maintenance of an optimal nutritional status, the prevention and / or correction of signs, symptoms and complications of chronic renal failure and, possibly, the delay in starting of dialysis. The DNT includes modulation of protein intake, adequacy of caloric intake, control of sodium and potassium intake, and reduction of phosphorus intake.

Oxygenic Photoreactivity in Photosystem II Studied by Rotating Ring Disk Electrochemistry.

Protein film photoelectrochemistry has previously been used to monitor the activity of photosystem II, the water-plastoquinone photooxidoreductase, but the mechanistic information attainable from a three-electrode setup has remained limited. Here we introduce the four-electrode rotating ring disk electrode technique for quantifying light-driven reaction kinetics and mechanistic pathways in real time at the enzyme-electrode interface. This setup allows us to study photochemical HO oxidation in photosystem II and to gain an in-depth understanding of pathways that generate reactive oxygen species.

Photochemistry beyond the red limit in chlorophyll f-containing photosystems.

Photosystems I and II convert solar energy into the chemical energy that powers life. Chlorophyll a photochemistry, using red light (680 to 700 nm), is near universal and is considered to define the energy "red limit" of oxygenic photosynthesis. We present biophysical studies on the photosystems from a cyanobacterium grown in far-red light (750 nm).

Nutritional treatment of advanced CKD: twenty consensus statements.

The Italian nephrology has a long tradition and experience in the field of dietetic-nutritional therapy (DNT), which is an important component in the conservative management of the patient suffering from a chronic kidney disease, which precedes and integrates the pharmacological therapies. The objectives of DNT include the maintenance of an optimal nutritional status, the prevention and/or correction of signs, symptoms and complications of chronic renal failure and, possibly, the delay in starting of dialysis. The DNT includes modulation of protein intake, adequacy of caloric intake, control of sodium and potassium intake, and reduction of phosphorus intake.

Glycolate Induces Redox Tuning Of Photosystem II in Vivo: Study of a Photorespiration Mutant.

Bicarbonate removal from the nonheme iron at the acceptor side of photosystem II (PSII) was shown recently to shift the midpoint potential of the primary quinone acceptor Q to a more positive potential and lowers the yield of singlet oxygen (O) production. The presence of Q results in weaker binding of bicarbonate, suggesting a redox-based regulatory and protective mechanism where loss of bicarbonate or exchange of bicarbonate by other small carboxylic acids may protect PSII against O in vivo under photorespiratory conditions. Here, we compared the properties of Q in the Arabidopsis () photorespiration mutant deficient in peroxisomal HYDROXYPYRUVATE REDUCTASE1 (), which accumulates glycolate in leaves, with the wild type.

Electricity generation from digitally printed cyanobacteria.

Microbial biophotovoltaic cells exploit the ability of cyanobacteria and microalgae to convert light energy into electrical current using water as the source of electrons. Such bioelectrochemical systems have a clear advantage over more conventional microbial fuel cells which require the input of organic carbon for microbial growth. However, innovative approaches are needed to address scale-up issues associated with the fabrication of the inorganic (electrodes) and biological (microbe) parts of the biophotovoltaic device.

Changes in routine laboratory tests and survival in amyotrophic lateral sclerosis.

The aim of this study is to evaluate the association between changes in routinely prescribed laboratory tests and tracheostomy-free survival in amyotrophic lateral sclerosis (ALS). Two hundred seventy-five ALS patients were retrospectively studied. BMI, forced vital capacity, hemoglobin, hematocrit, lymphocytes, cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides, proteins, albumin, creatine-phosphokinase, iron, ferritin, transferrin, glucose, urea, uric acid, and creatinine were measured every 6 months from baseline to 24 months, death or study end, together with the probability of death or tracheostomy.

Photoelectrochemistry of Photosystem II in Vitro vs in Vivo.

Factors governing the photoelectrochemical output of photosynthetic microorganisms are poorly understood, and energy loss may occur due to inefficient electron transfer (ET) processes. Here, we systematically compare the photoelectrochemistry of photosystem II (PSII) protein-films to cyanobacteria biofilms to derive: (i) the losses in light-to-charge conversion efficiencies, (ii) gains in photocatalytic longevity, and (iii) insights into the ET mechanism at the biofilm interface. This study was enabled by the use of hierarchically structured electrodes, which could be tailored for high/stable loadings of PSII core complexes and Synechocystis sp.

Bicarbonate-induced redox tuning in Photosystem II for regulation and protection.

The midpoint potential (E) of [Formula: see text], the one-electron acceptor quinone of Photosystem II (PSII), provides the thermodynamic reference for calibrating PSII bioenergetics. Uncertainty exists in the literature, with two values differing by ∼80 mV. Here, we have resolved this discrepancy by using spectroelectrochemistry on plant PSII-enriched membranes.

Photocurrents from photosystem II in a metal oxide hybrid system: Electron transfer pathways.

We have investigated the nature of the photocurrent generated by Photosystem II (PSII), the water oxidizing enzyme, isolated from Thermosynechococcus elongatus, when immobilized on nanostructured titanium dioxide on an indium tin oxide electrode (TiO2/ITO). We investigated the properties of the photocurrent from PSII when immobilized as a monolayer versus multilayers, in the presence and absence of an inhibitor that binds to the site of the exchangeable quinone (QB) and in the presence and absence of exogenous mobile electron carriers (mediators). The findings indicate that electron transfer occurs from the first quinone (QA) directly to the electrode surface but that the electron transfer through the nanostructured metal oxide is the rate-limiting step.

Intracoronary thrombolysis in patients with ST-segment elevation myocardial infarction presenting with massive intraluminal thrombus and failed aspiration.

Aim: Massive intracoronary thrombus is associated with adverse procedural results including failed aspiration and unfavourable reperfusion. In this scenario the best treatment remains unknown. We aim to evaluate the effect of low dose intracoronary thrombolysis in patients with ST-segment elevation myocardial infarction (STEMI) presenting with a large thrombus burden and failed aspiration.

[The usefulness of Moynihan questionnaire in the evaluation of knowledge on healthy diet of patients undergoing cardiology rehabilitation].

Background: The aim of study was to test the usefulness of Moynihan questionnaire in the evaluation of knowledge on healthy diet of patients undergoing cardiology rehabilitation.

Methods: We enrolled 51 patients (pts): 41 men and 10 women, mean age 67.97 +/-11.