Water splitting Dotaz Zobrazit nápovědu
Titanium oxide (TiO2) and iron oxide (α-Fe2O3) hematite films have potential applications as photoanodes in electrochemical water splitting. In the present work TiO2 and α-Fe2O3 thin films were prepared by two methods, e.g., sol-gel and High Power Impulse Magnetron Sputtering (HiPIMS) and judged on the basis of physical properties such as crystalline structure and surface topography and functional properties such as simulated photoelectrochemical (PEC) water splitting conditions. It was revealed that the HiPIMS method already provides crystalline structures of anatase TiO2 and hematite Fe2O3 during the deposition, whereas to finalize the sol-gel route the as-deposited films must always be annealed to obtain the crystalline phase. Regarding the PEC activity, both TiO2 films show similar photocurrent density, but only when illuminated by UV light. A different situation was observed for hematite films where plasmatic films showed a tenfold enhancement of the stable photocurrent density over the sol-gel hematite films for both UV and visible irradiation. The superior properties of plasmatic film could be explained by ability to address some of the hematite drawbacks by deposition of very thin films (25 nm) consisting of small densely packed particles and by doping with Sn.
The effect of water-splitting Mn complex on light-induced redox changes of cytochrome b(559) (cyt b(559)) was studied in spinach photosystem II (PSII) membranes. Photoreduction of the heme iron in the intact PSII membranes was completely suppressed by DCMU, whereas photoreduction and photooxidation of the heme iron in the Mn-depleted PSII membranes were unaffected by DCMU. Interestingly, photoreduction and photooxidation of the heme iron in the Mn-depleted PSII membranes were completely diminished by exogenous superoxide dismutase (SOD), whereas no effect of SOD on photoreduction of the heme iron was observed in the intact PSII membranes. The current work shows that the light-induced redox changes of cyt b(559) proceed via a different mechanism in the both types of PSII membranes. In the intact PSII membranes, photoreduction of the heme iron is mediated by plastoquinol. However, in the Mn-depleted PSII membranes, photoreduction and photooxidation of the heme iron are mediated by superoxide anion radical formed in PSII.
- MeSH
- cytochromy typu b chemie metabolismus MeSH
- fotosystém II (proteinový komplex) chemie metabolismus MeSH
- konformace proteinů MeSH
- mangan nedostatek metabolismus MeSH
- oxidace-redukce MeSH
- rostlinné proteiny metabolismus MeSH
- Spinacia oleracea metabolismus MeSH
- voda metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Introduction: Rheumatoid arthritis (RA) is a chronic autoimmune disease with unknown cause. It mainly affects joints and, without proper treatment, negatively impacts their movement, causes painful deformities, and reduces the patients' quality of life. Current treatment options consist of various types of disease-modifying antirheumatic drugs (DMARDs), however 20-30% of patients are partially resistant to them. Therefore, development of new drugs is necessary. Possible option are compounds exhibiting their action via endocannabinoid system, which plays an important role in pain and inflammation modulation. One such compound - cannabidiol (CBD) has already been shown to attenuate synovitis in animal model of RA in in vivo studies. However, it has low bioavailability due to its low water solubility and lipophilicity. This issue can be addressed by preparation of a lipid containing formulation targeting lymphatic system, another route of absorption in the body. Materials and Methods: CBD-containing emulsion was prepared by high-shear homogenization and its droplet size distribution was analysed by optical microscopy. The relative oral bioavailability compared to oil solution as well as total availability of CBD were assessed in a cross-over study in rats and absorption of CBD via lymphatic system was observed. The effect of CBD on the animal model of RA was determined. Results: Compared to oil solution, the emulsion exhibited higher absolute oral bioavailability. Significant lymphatic transport of CBD was observed in all formulations and the concentrations in lymph were calculated. The therapeutic effect of CBD on RA was confirmed as an improvement in clinical symptoms as well as morphological signs of disease activity were observed during the study. Conclusion: In this work, we prepared a simple stable emulsion formulation, determined the pharmacokinetic parameters of CBD and calculated its absolute bioavailability in rats. Moreover, we successfully tested the pharmaceutical application of such a formulation and demonstrated the positive effect of CBD in an animal model of RA.
- MeSH
- aplikace orální MeSH
- bolest farmakoterapie MeSH
- emulze MeSH
- kanabidiol * farmakologie chemie MeSH
- klinické křížové studie MeSH
- krysa rodu rattus MeSH
- kvalita života MeSH
- revmatoidní artritida * farmakoterapie MeSH
- voda MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Background and study aims Single-center studies, which were retrospective and/or involved unblinded colonoscopists, have suggested that water exchange, but not water immersion, compared with air insufflation significantly increases the adenoma detection rate (ADR), particularly in the proximal and right colon. Head-to-head comparison of the three techniques with ADR as primary outcome and blinded colonoscopists has not been reported to date. In a randomized controlled trial with blinded colonoscopists, we aimed to evaluate the impact of the three insertion techniques on ADR.Patients and methods A total of 1224 patients aged 50 - 70 years (672 males) and undergoing screening colonoscopy were randomized 1:1:1 to water exchange, water immersion, or air insufflation. Split-dose bowel preparation was adopted to optimize colon cleansing. After the cecum had been reached, a second colonoscopist who was blinded to the insertion technique performed the withdrawal. The primary outcome was overall ADR according to the three insertion techniques (water exchange, water immersion, and air insufflation). Secondary outcomes were other pertinent overall and right colon procedure-related measures.Results Baseline characteristics of the three groups were comparable. Compared with air insufflation, water exchange achieved a significantly higher overall ADR (49.3 %, 95 % confidence interval [CI] 44.3 % - 54.2 % vs. 40.4 % 95 %CI 35.6 % - 45.3 %;P = 0.03); water exchange showed comparable overall ADR vs. water immersion (43.4 %, 95 %CI 38.5 % - 48.3 %;P = 0.28). In the right colon, water exchange achieved a higher ADR than air insufflation (24.0 %, 95 %CI 20.0 % - 28.5 % vs. 16.9 %, 95 %CI 13.4 % - 20.9 %;P = 0.04) and a higher advanced ADR (6.1 %, 95 %CI 4.0 % - 9.0 % vs. 2.5 %, 95 %CI 1.2 % - 4.6 %;P = 0.03). Compared with air insufflation, the mean number of adenomas per procedure was significantly higher with water exchange (P = 0.04). Water exchange achieved the highest cleanliness scores (overall and in the right colon). These variables were comparable between water immersion and air insufflation.Conclusions The design with blinded observers strengthens the validity of the observation that water exchange, but not water immersion, can achieve significantly higher adenoma detection than air insufflation. Based on this evidence, the use of water exchange should be encouraged.Trial registered at ClinicalTrials.gov (NCT02041507).
- MeSH
- adenom diagnostické zobrazování MeSH
- časná detekce nádoru metody MeSH
- colon ascendens MeSH
- colon transversum MeSH
- dvojitá slepá metoda MeSH
- insuflace MeSH
- kolonoskopie metody MeSH
- léčebná irigace metody MeSH
- lidé středního věku MeSH
- lidé MeSH
- nádory tračníku diagnostické zobrazování MeSH
- purgativa aplikace a dávkování MeSH
- senioři MeSH
- voda MeSH
- vzduch MeSH
- Check Tag
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- multicentrická studie MeSH
- randomizované kontrolované studie MeSH
- srovnávací studie MeSH
BACKGROUND & AIMS: Unsedated colonoscopy is acceptable for diagnostic, surveillance, and screening indications worldwide. However, insertion of the colonoscope can be painful; it is not clear which technique is least painful and thereby increases the likelihood of colonoscopy completion. We performed a head-to-head comparison of air insufflation (AI), carbon dioxide (CO2) insufflation, water immersion (WI), and water exchange (WE) to determine which combination of insertion techniques produces the least amount of pain. METHODS: In a patient-blinded prospective trial, 624 subjects were assigned randomly to groups that underwent colonoscopy with AI-AI, CO2-CO2, WI-AI, WE-AI, WI-CO2, or WE-CO2 insertion and withdrawal techniques, including on-demand sedation, at the St. Barbara Hospital (Iglesias, Italy) or the Vìtkovice Hospital (Ostrava, Czech Republic), from October 2013 through June 2014. The primary outcome was real-time maximum insertion pain (0 = none, 10 = worst), recorded by an unblinded nurse assistant. At discharge, a blinded observer recorded the recalled maximum insertion pain and patients' and investigators' guesses about method or gas used. RESULTS: Patients and investigators correctly guessed the method used for fewer than 44% of procedures, confirming adequate blinding. The correlation between real-time and recalled maximum insertion pain (r = 0.9; P < .0005) confirmed internal validation of the primary outcome. The WE group had the lowest scores: mean pain values were 5.2 for AI-AI (95% confidence interval [CI], 4.6-5.8), 4.9 for CO2-CO2 (95% CI, 4.3-5.4), 4.3 for WI-CO2 (95% CI, 3.8-4.9), 4.0 for WI-AI (95% CI, 3.5-4.5), 3.1 for WE-CO2 (95% CI, 2.7-3.4), and 3.1 for WE-AI (95% CI, 2.7-3.6) (P < .0005). The highest proportions of patients completing unsedated colonoscopy were in the WE groups. WE groups also had significantly better colon cleanliness, particularly in the transverse and right colon (P < .0005). One limitation of the study was that colonoscopists and assistants were not blinded to water-aided insertion methods. CONCLUSIONS: In a prospective study of colonoscopy insertion methods, CO2 insufflation did not reduce real-time maximum insertion pain. Compared with AI or CO2, WI and WE reduced insertion pain. The least painful technique was WE, which significantly increased completion of unsedated colonoscopy and bowel cleanliness without prolonging insertion time. ClinicalTrials.gov number: NCT01954862.
- MeSH
- bolest * MeSH
- dospělí MeSH
- jednoduchá slepá metoda MeSH
- kolonoskopie škodlivé účinky metody MeSH
- lidé středního věku MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- prospektivní studie MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- zvířata MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- randomizované kontrolované studie MeSH
- srovnávací studie MeSH
- Geografické názvy
- Česká republika MeSH
- Itálie MeSH
Hydroxyl radical (HO•) production in photosystem II (PSII) was studied by electron paramagnetic resonance (EPR) spin-trapping technique. It is demonstrated here that the exposure of PSII membranes to heat stress (40 °C) results in HO• formation, as monitored by the formation of EMPO-OH adduct EPR signal. The presence of different exogenous halides significantly suppressed the EMPO-OH adduct EPR signal in PSII membranes under heat stress. The addition of exogenous acetate and blocker of chloride channel suppressed the EMPO-OH adduct EPR signal, whereas the blocker of calcium channel did not affect the EMPO-OH adduct EPR signal. Heat-induced hydrogen peroxide (H₂O₂) production was studied by amplex red fluorescent assay. The presence of exogenous halides, acetate and chloride blocker showed the suppression of H₂O₂ production in PSII membranes under heat stress. Based on our results, it is proposed that the formation of HO• under heat stress is linked to uncontrolled accessibility of water to the water-splitting manganese complex caused by the release of chloride ion on the electron donor side of PSII. Uncontrolled water accessibility to the water-splitting manganese complex causes the formation of H₂O₂ due to improper water oxidation, which leads to the formation of HO• via the Fenton reaction under heat stress.
- MeSH
- chloridy metabolismus MeSH
- elektronová paramagnetická rezonance metody MeSH
- fotosystém II (proteinový komplex) chemie metabolismus MeSH
- hydroxylový radikál metabolismus MeSH
- oxidace-redukce MeSH
- peroxid vodíku farmakologie MeSH
- spin trapping metody MeSH
- Spinacia oleracea chemie MeSH
- vytápění MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Metal ions play a crucial role in enzymatic reactions in all photosynthetic organisms such as cyanobacteria, algae and plants. It well known that metal ions maintain the binding of substrate in the active site of the metalloenzymes and control the redox activity of the metalloenzyme in the enzymatic reaction. A large pigment-protein complex, PSII, known to serve as a water-plastoquinone oxidoreductase, contains three metal centers comprising non-heme iron, heme iron of Cyt b559 and the water-splitting manganese complex. Metal ions bound to PSII proteins maintain the electron transport from water to plastoquinone and regulate the pro-oxidant and antioxidant activity in PSII. In this review, attention is focused on the role of PSII metal centers in (i) the formation of superoxide anion and hydroxyl radicals by sequential one-electron reduction of molecular oxygen and the formation of hydrogen peroxide by incomplete two-electron oxidation of water; and (ii) the elimination of superoxide anion radical by one-electron oxidation and reduction (superoxide dismutase activity) and of hydrogen peroxide by two-electron oxidation and reduction (catalase activity). The balance between the formation and elimination of reactive oxygen species by PSII metal centers is discussed as an important aspect in the prevention of photo-oxidative damage of PSII proteins and lipids.
- MeSH
- cytochromy typu b chemie metabolismus MeSH
- fotosystém II (proteinový komplex) chemie metabolismus MeSH
- katalytická doména MeSH
- kovy metabolismus MeSH
- kyslík metabolismus MeSH
- mangan metabolismus MeSH
- molekulární modely MeSH
- oxidace-redukce MeSH
- reaktivní formy kyslíku metabolismus MeSH
- rostliny enzymologie MeSH
- scavengery volných radikálů metabolismus MeSH
- sinice enzymologie MeSH
- voda metabolismus MeSH
- železo metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
The PsbO protein is an essential extrinsic subunit of photosystem II, the pigment-protein complex responsible for light-driven water splitting. Water oxidation in photosystem II supplies electrons to the photosynthetic electron transfer chain and is accompanied by proton release and oxygen evolution. While the electron transfer steps in this process are well defined and characterized, the driving forces acting on the liberated protons, their dynamics and their destiny are all largely unknown. It was suggested that PsbO undergoes proton-induced conformational changes and forms hydrogen bond networks that ensure prompt proton removal from the catalytic site of water oxidation, i.e. the Mn4 CaO5 cluster. This work reports the purification and characterization of heterologously expressed PsbO from green algae Chlamydomonas reinhardtii and two isoforms from the higher plant Solanum tuberosum (PsbO1 and PsbO2). A comparison to the spinach PsbO reveals striking similarities in intrinsic protein fluorescence and CD spectra, reflecting the near-identical secondary structure of the proteins from algae and higher plants. Titration experiments using the hydrophobic fluorescence probe ANS revealed that eukaryotic PsbO proteins exhibit acid-base hysteresis. This hysteresis is a dynamic effect accompanied by changes in the accessibility of the protein's hydrophobic core and is not due to reversible oligomerization or unfolding of the PsbO protein. These results confirm the hypothesis that pH-dependent dynamic behavior at physiological pH ranges is a common feature of PsbO proteins and causes reversible opening and closing of their β-barrel domain in response to the fluctuating acidity of the thylakoid lumen.
