Presence Of Fd Research Articles

Acceleration of adsorption of heavy metal ion micelles onto iron/polyvinyltetrazole adsorbents with dielectrophoresis force under polarization

Metal ions are eliminated from wastewater through absorbents via diffusion. To expedite the diffusion rate within a non-uniform electric field, an external dielectrophoresis force (FD) is introduced through frequency manipulation. Polyvinyltetrazole microadsorbents (FVTMs) incorporating iron elements are synthesized as adsorbents to bolster the FD's strength, which relies predominantly on the dielectric constants of the medium and particles. Cr(III), Cu(II), and Pb(II) are chosen to form micelles with surfactants as absorbates. These micelles (MIM) encapsulate Cr(III), Cu(II), and Pb(II) at concentrations ranging from 10 to 80 mmol L−1, driven towards the FVTMs by the attractive FD in the medium. In the absence of FD, for metal ion solutions at 80 mmol L−1, the removal ratios range from 28.6 to 32.6 % within 40 min, while in the presence of FD, the removal ratios reach the range of 89.6 to 92.3 %. The theoretical adsorption rate constants of MIMs onto the FVTMs under frequency polarization are enhanced approximately fivefold by the external FD generated at 5 V and 50 kHz. At a high frequency of 200 kHz, a repulsive FD is generated, reversing the adsorption and facilitating the recycling efficiency of FVTMs. As a result, FD can manipulate the adsorption rate with a particular frequency, enabling the removal of metal ions and the reuse of adsorbents. The FVTMs containing iron elements are reused up to 10 times under polarization switching frequencies between 50 and 200 kHz. This proposed platform introduces a novel methodology utilizing ferrous metal ion adsorbents for the rapid treatment of discharge.

Functional Dyspepsia and Irritable Bowel Syndrome are Highly Prevalent in Patients With Gallstones and Are Negatively Associated With Outcomes After Cholecystectomy: A Prospective, Multicenter, Observational Study (PERFECT - Trial).

To determine the prevalence of FD and IBS in patients eligible for cholecystectomy and to investigate the association between presence of FD/ IBS and resolution of biliary colic and a pain-free state. More than 30% of patients with symptomatic cholecystolithiasis reports persisting pain postcholecystectomy. Coexistence of FD/IBS may contribute to this unsatisfactory outcome. We conducted a multicenter, prospective, observational study (PERFECT-trial). Patients ≥18 years with abdominal pain and gallstones were included at 5 surgical outpatient clinics between 01/2018 and 04/2019. Follow-up was 6 months. Primary outcomes were prevalence of FD/IBS, and the difference between resolution of biliary colic and pain-free state in patients with and without FD/IBS. FD/IBS was defined by the Rome IV criteria, biliary colic by the Rome III criteria, and pain-free by an Izbicki Pain Score ≤10 and visual analogue scale ≤4. We included 401 patients with abdominal pain and gallstones (assumed eligible for cholecystectomy), mean age 52 years, 76% females. Of these, 34.9% fulfilled criteria for FD/IBS. 64.1% fulfilled criteria for biliary colic and 74.9% underwent cholecystectomy, with similar operation rates in patients with and without FD/IBS. Postcholecystectomy, 6.1% of patients fulfilled criteria for biliary colic, with no significant difference between those with and without FD/IBS at baseline (4.9% vs 8.6%, P = 0.22). Of all patients, 56.8% was pain-free after cholecystectomy, 40.7% of FD/IBS-group vs 64.4% of no FD/IBS-group, P < 0.001. One third of patients eligible for cholecystectomy fulfil criteria for FD/IBS. Biliary colic is reported by only a few patients postcholecys-tectomy, whereas nonbiliary abdominal pain persists in >40%, particularly in those with FD/IBS precholecystectomy. Clinicians should take these symptom-dependent outcomes into account in their shared decision-making process. The Netherlands Trial Register NTR-7307. Registered on 18 June 2018.

Long-Term Gastrointestinal Consequences are Frequent Following Sporadic Acute Infectious Diarrhea in a Tropical Country: A Prospective Cohort Study.

Postinfection irritable bowel syndrome (PI-IBS) and functional dyspepsia (PI-FD), though reported from the temperate countries, have not been studied in the tropics; PI-malabsorption syndrome (MAS), which mimics PI-IBS, is reported from the tropics. No report till date on PI-IBS excluded PI-MAS. We studied: (i) the frequency of continuing bowel dysfunction after acute gastroenteritis (AG), (ii) its predictors, and (iii) PI-MAS among patients with PI-IBS. 345 consecutive subjects each, with AG and age- and gender-matched healthy controls were followed up 3-monthly for 12 months using a translated-validated questionnaire and functional gastrointestinal disorders (FGIDs) were diagnosed by Rome III criteria. Symptom duration >3 months but <6 months was diagnosed as chronic bowel dysfunction (CBD) and dyspeptic symptoms, respectively. MAS was diagnosed if 2/3 tests (D-xylose H2 breath test, Sudan III-stained stool microscopy, and duodenal histology) were abnormal. Fecal microbiological studies were performed in 245/345 (71%) patients. AG patients more often developed PI-IBS and PI-FD than controls (16.5 vs. 2.6% and 7.4 vs. 0.6%, respectively; p<0.001). Presence of FD was a risk factor for PI-IBS and IBS for PI-FD. On multivariate analysis, dyspeptic symptoms, CBD, and weight loss were the risk factors for PI-FGIDs. The frequency of PI-IBS following Vibrio cholera and other bacterial infection was comparable. Malabsorption was present among 2/23 (9%) patients with PI-IBS. FGIDs are common after AG; dyspeptic symptoms, CBD, and weight loss were risk factors for PI-FGIDs. Vibrio cholerae infection caused PI-FGID, which was never reported. About 9 % patients fulfilling the criteria for PI-IBS had PI-MAS.

Photosynthetic electron partitioning between [FeFe]-hydrogenase and ferredoxin:NADP + -oxidoreductase (FNR) enzymes in vitro

Photosynthetic water splitting, coupled to hydrogenase-catalyzed hydrogen production, is considered a promising clean, renewable source of energy. It is widely accepted that the oxygen sensitivity of hydrogen production, combined with competition between hydrogenases and NADPH-dependent carbon dioxide fixation are the main limitations for its commercialization. Here we provide evidence that, under the anaerobic conditions that support hydrogen production, there is a significant loss of photosynthetic electrons toward NADPH production in vitro. To elucidate the basis for competition, we bioengineered a ferredoxin-hydrogenase fusion and characterized hydrogen production kinetics in the presence of Fd, ferredoxin:NADP(+)-oxidoreductase (FNR), and NADP(+). Replacing the hydrogenase with a ferredoxin-hydrogenase fusion switched the bias of electron transfer from FNR to hydrogenase and resulted in an increased rate of hydrogen photoproduction. These results suggest a new direction for improvement of biohydrogen production and a means to further resolve the mechanisms that control partitioning of photosynthetic electron transport.

Evaluation of the participation of ferredoxin in oxygen reduction in the photosynthetic electron transport chain of isolated pea thylakoids.

The contribution to reduction of oxygen by ferredoxin (Fd) to the overall reduction of oxygen in isolated pea thylakoids was studied in the presence of Fd versus Fd + NADP(+). The overall rate of electron transport was measured using a determination of Photosystem II quantum yield from chlorophyll fluorescence parameters, and the rate of oxidation of Fd was measured from the light-induced redox changes of Fd. At low light intensity, increasing Fd concentration from 5 to 30 microM in the absence of NADP(+) increased the proportion of oxygen reduction by Fd from 25-35 to 40-60% in different experiments. This proportion decreased with increasing light intensity. When NADP(+) was added in the presence of 15 microM Fd, which was optimal for the NADP(+) reduction rate, the participation of Fd in the reduction of oxygen was low, no more than 10%, and it also decreased with increasing light intensity. At high light intensity, the overall oxygen reduction rates in the presence of Fd + NADP(+) and in the presence of Fd alone were comparable. The significance of reduction of dioxygen either by water-soluble Fd or by the membrane-bound carriers of the photosynthetic electron transport chain for redox signaling under different light intensities is discussed.

Dyspepsia and IBS Symptoms in Patients with NERD, ERD and Barrett’s Esophagus

Introduction: Irritable bowel syndrome (IBS) and functional dyspepsia (FD) are highly prevalent in the general population as does gastroesophageal reflux disease (GERD). Therefore, it is expected that these conditions may frequently overlap. Objective: We aimed at evaluating the presence ofFD and IBS symptoms in patients with erosive (ERD), non-erosive reflux disease (NERD) and Barrett’s esophagus (BE). Patients and Methods: 71 patients presenting at the reflux disease outpatient clinic were prospectively included in this study. 33 patients had NERD, 25 ERD and 13 BE according to the Montreal classification. All patients with ERD and NERD had typical reflux symptoms, as assessed by a validated GERD questionnaire (RDQ). The diagnosis of functional dyspepsia and IBS symptoms was assessed according to the Rome III criteria. Results: IBS symptoms (bloating, abdominal pain, constipation and diarrhea) were slightly more prevalent in NERD (54.6, 63.6, 21.20, 24.2%, respectively) than in ERD (48.0, 44.0, 12.0, 20.0%, respectively) and in BE (53.9, 23.10, 15,4, 23.1%, respectively), but none of these differences reached statistical significance. NERD patients had more FD symptoms than patients with ERD or BE, but again this difference did not reach statistical significance. Conclusion: Our data show that IBS and FD are common in the entire spectrum of GERD. The presence of these disorders might explain why many patients with GERD are deemed as treatment failures if they have no complete symptom relief with proton pump inhibitors.

Two isoforms of ferredoxin:NADP+ oxidoreductase from wheat leaves: purification and initial biochemical characterization

Ferredoxin:NADP(+) oxidoreductase is an enzyme associated with the stromal side of the thylakoid membrane in the chloroplast. It is involved in photosynthetic linear electron transport to produce NADPH and is supposed to play a role in cyclic electron transfer, generating a transmembrane pH gradient allowing ATP production, if photosystem II is non-functional or no NADP(+) is available for reduction. Different FNR isoforms have been described in non-photosynthetic tissues, where the enzyme catalyses the NADPH-dependent reduction of ferredoxin (Fd), necessary for some biosynthetic pathways. Here, we report the isolation and purification of two FNR isoproteins from wheat leaves, called FNR-A and FNR-B. These forms of the enzyme were identified as products of two different genes, as confirmed by mass spectrometry. The molecular masses of FNR-A and FNR-B were 34.3 kDa and 35.5 kDa, respectively. The isoelectric point of both FNR-A and FNR-B was about 5, but FNR-B appeared more acidic (of about 0.2 pH unit) than FNR-A. Both isoenzymes were able to catalyse a NADPH-dependent reduction of dibromothymoquinone and the mixture of isoforms catalysed reduction of cytochrome c in the presence of Fd. For the first time, the pH- and ionic strength dependent oligomerization of FNRs is observed. No other protein was necessary for complex formation. The putative role of the two FNR isoforms in photosynthesis is discussed based on current knowledge of electron transport in chloroplasts.

Cleavage of Chlorophyll-Porphyrin (Requirement for Reduced Ferredoxin and Oxygen)

The chemical structures of some colorless catabolites that accumulate in senescent leaves have been established recently (B. Krautler, B. Jaun, W. Amrein, K. Bortlik, M. Schellenberg, P. Matile [1992] Plant Physiol Biochem 30: 333-346; W. Muhlecker, B. Krautler, S. Ginsburg, P. Matile [1993] Helv Chim Acta 76: 2976-2980). Such studies suggest that oxygenolytic cleavage of chlorophyll-porphyrin may occur by the action of a dioxygenase. We have attempted to demonstrate such an enzyme activity and to explore the requirements of the cleavage reaction in a reconstituted system of chloroplast (Chlpl) components prepared from senescent rape (Brassica napus L.) cotyledons. Intact senescent Chpls (also referred to as gerontoplasts) contain small amounts of two fluorescent chlorophyll catabolites, Bn-FCC-1 and Bn-FCC-2, probably representing primary cleavage products. Upon the incubation of Gpls in the presence of glucose-6-phosphate (Glc6P) or ATP, these catabolites (predominantly FCC-1) were produced in organello. In a reconstituted system of thylakoids and stroma fraction the FCCs (predominantly FCC-2) were produced in the presence of ferredoxin (Fd) and cofactors (NADPH, Glc6P) helping to keep Fd in the reduced state. Reduced Fd could not be replaced by other electron donors, suggesting that the putative dioxygenase requires Fd for the operation of its redox cycle. Production of FCC-2 did not occur in the absence of oxygen and it was inhibited by chelators of Fe2+. The contributions to the production of FCCs from both parts of the reconstituted system, thylakoids and stroma, are heat labile. The enzymic process in the thylakoids yields pheophorbide a, the presumptive precursor of FCCs. However, native senescent thylakoids could not be replaced as a "substrate" by free pheophorbide a. The stromal enzyme appears to have an affinity for senescent thylakoids; thus, "loaded" thylakoids capable of FCC production in the presence of Fd and cofactors were obtained upon homogenization of senescent cotyledons in a medium containing sorbitol and ascorbate. Such thylakoids were inactive if prepared from mature green cotyledons. As senescence was induced, the capacity to generate FCCs appeared and peaked when about half of the chlorophyll had disappeared from the cotyledons. The effectiveness of a relevant inhibitor showed that cytoplasmic protein synthesis was required for inducing the catabolic machinery in the loaded thylakoids. Thylakoids from mature Chlpls were ineffective as substrate of the stromal enzyme prepared from Gpls. However, senescent thylakoids yielded FCCs if challenged with stroma from either Chlpls or Gpls. Therefore, the stromal part of the system is likely to be a constitutive enzyme, and the pace-setting step of the pathway of chlorophyll breakdown seems to be located in the thylakoids.

The photoreduction of spinach ferredoxin in the presence of porphyrin and an electron donor.

It has previously been established that photosynthetic pyridine nucleotide reductase (PPNR)' or spinach ferredoxin (Fd)2 is required for the reduction of pyridine nucleotides by illuminated chloroplasts. The reduction of Fd by illuminated chloroplasts has since been described by various workers.3-5 In addition, it has been shown that Fd can be reduced by hydrogen and hydrogenase,2 hydrosulfite, and hydrogen and platinum asbestos.3 Furthermore, the photoreduction of Fd by illuminated chloroplasts with its subsequent oxidation in a dark reaction leading to the formation of reduced pyridine nucleotide has been demonstrated.4 The NADP-reducing system of spinach chloroplasts is composed of two components, a ferredoxin and a flavoprotein enzyme referred to as ferredoxin-NADP reductase (spinach pyridine nucleotide transhydrogenase or spinach NADPH diaphorase). Evidence that both components are required for the reduction of pyridine nucleotides by illuminated chloroplasts, with Fd being reduced initially by the chloroplast, has been presented.2 6-10 Krasnovsky11 first demonstrated that chlorophyll photosensitized the reduction of a number of dyes in pyridine solution, with ascorbic acid as the electron donor. Thereafter, it was shown12 13 that chlorophylls dissolved in pyridine catalyzed a photoreduction of pyridine nucleotides by ascorbate. Vernon14 reported that various porphyrins and porphyrin derivatives, as well as chlorophyll, catalyzed the photoreduction of NAD and NADP by ascorbate in aqueous media and that the reaction required the presence of partially purified Fd. Later work5, 16 with purified preparations showed that Fd did not catalyze the photoreduction of pyridine nucleotides with either hematoporphyrin or chlorophyllin a as the photocatalyst when Fd was present either alone or together with the NADP reductase. With either photocatalyst, only the NADP reductase was required for NADP photoreduction in this system. The photoreduction of NAD or NADP in chloroplasts required both the presence of Fd and the NADP diaphorase as previously noted. No evidence was presented for the photoreduction of Fd in the porphyrin (or chlorophyll)-ascorbate system. Fd, however, has been noted as the earliest chemically isolatable reductant formed during conversion of electromagnetic energy into chemical energy in photosynthesis.5 None of these previous studies have provided evidence that Fd might interact directly with chlorophyll in the intact chloroplast as the primary electron acceptor. The work to be described in this paper demonstrates that Fd can be photoreduced in the presence of a porphyrin and light with an electron donor.