Redox Reaction

Chicken egg white protects the embryo from bacterial invaders by presenting an assortment of antagonistic activities that combine together to both kill and inhibit growth. The key features of the egg white anti-bacterial system are iron restriction, high pH, antibacterial peptides and proteins, and viscosity. Salmonella enterica serovar Enteritidis is the major pathogen responsible for egg-borne infection in humans, which is partly explained by its exceptional capacity for survival under the harsh conditions encountered within egg white. However, at temperatures up to 42°C, egg white exerts a much stronger bactericidal effect on S. Enteritidis than at lower temperatures, although the mechanism of egg white-induced killing is only partly understood. Here, for the first time, the impact of exposure of S. Enteritidis to egg white under bactericidal conditions (45°C) is explored by global-expression analysis. A large-scale (18.7% of genome) shift in transcription is revealed suggesting ...

The redox properties of hydralazine were studied by cyclic voltammetric method. The effect of scan rates on the voltammogram of hydralazine was studied and various electrochemical parameters e.g.E pa , E pc , I pa , I pc were determined. The results show a quasireversible behavior of hydralazine hydrochloride.

Arsenic contamination in water poses a significant global health risk, necessitating efficient and sustainable remediation strategies. Arsenic contamination affects groundwater in at least 106 countries, potentially exposing over 200 million people to elevated levels, primarily through contaminated drinking water. Among the most affected regions, Bangladesh remains a critical case study, where widespread reliance on shallow tubewells has resulted in one of the largest mass poisonings in history. Bio-based nanomaterials have emerged as promising solutions due to their eco-friendly nature, cost-effectiveness, and high adsorption capabilities. These nanomaterials offer a sustainable approach to arsenic remediation, utilizing materials like biochar, modified biopolymers, and bio-based aerogels, which can effectively adsorb arsenic and other pollutants. The use of environmentally friendly nanostructures provides a potential option for improving the efficiency and sustainability of arsenic remediation from groundwater. This review explores the mechanisms underlying arsenic remediation using such nanomaterials, including adsorption, filtration/membrane technology, photocatalysis, redox reactions, complexation, ion exchange, and coagulation-flocculation. Despite their potential, challenges such as scalability, stability, and regeneration hinder widespread application. We discuss recent advancements in material design, surface modifications, and hybrid systems that enhance performance. Finally, future perspectives are highlighted, including the integration of these bio-derived systems with smart sensing technologies, sustainable water-treatment frameworks, smart design, and life-cycle integration strategies, particularly for use in resource-constrained regions like Bangladesh and other globally impacted areas.

The molybdenum cofactor is composed of a molybdenum coordinated by one or two rather complicated ligands known as either molybdopterin or pyranopterin. Pterin is one of a large family of bicyclic N-heterocycles called pteridines. Such molecules are widely found in Nature, having various forms to perform a variety of biological functions. This article describes the basic nomenclature of pterin, their biological roles, structure, chemical synthesis and redox reactivity. In addition, the biosynthesis of pterins and current models of the molybdenum cofactor are discussed.

In situ infrared reflection spectra of thin polypyrrole films electrodeposited on platinum were obtained in aqueous KNO 3 , KCl and KF solutions, within a wide potential interval ranging from the reduced, insulating state, to the oxidative degradation of the material. These spectra provide information on the molecular changes resulting from the generation of charge carriers (radical cations and dications) in this conjugated heterocyclic system, as well as the irreversible chemical changes accompanying its electrochemical oxidation at very positive potentials. The spectral region between 1000 and 1700 cm -1 contains information on the relative populations of charge defects as a function of potential, and the results confirm that electronic charge transport at moderate potentials is due to formation of radical cations, which oxidize further or recombine to form dications as the potential increases. At more positive potentials the polymer degrades with formation of carbonyl and hydroxyl groups as well as CO 2 . The overoxidation process occurs at less positive potential in F -solution due to nucleophilic attack of OH -ions originating from dissociation of the aqueous solvent, as shown by the infrared spectra and previous calorimetric evidence. In the absence of irreversible chemical changes due to overoxidation, the infrared spectra obtained in the different solutions were similar, indicating weak interactions between ions and charge defects in the backbone.

This activity introduces digital microfluidics and the usage of aqueous droplets as independent chemical microreactors for reaction kinetics studies. Students build their own droplet generator from common macroscopic glassware and connecting parts, to create trains of millimetric droplets in which a redox reaction takes place. The activity allows working on reaction kinetics, hydrodynamics at low Reynolds number and image analysis at a macroscopic scale.

Preparação para Exames de Admissão Ficha 11B. Electrólise 1. A electrólise é um processo não-espontâneo, onde uma reacção química é provocada por _____. 2. A electrólise de cloreto de sódio fundido produz sódio metálico e gás cloro. Nesse processo cada ião: A. Sódio recebe dois electrões D. cloreto recebe um electrão B. Sódio recebe um electrões E. cloreto perde dois electrões C. Sódio perde um electrão. 3. Numa célula electrolítica, o cátodo é o eléctrodo que: A. Não recebe carga positiva do circuito metálico B. Recebe carga negativa do circuito metálico C. Atrai os aniões D. Recebe carga positiva do circuito metálico E. Apresenta carga eléctrica positiva 4. Complete as seguintes frases, considerando electrólise A. A massa que se liberta num eléctrodo é proporcional à ______________ que atravessa a solução (1ª Lei de Faraday). B. A massa que num eléctrodo é proporcional ao ______________ da substância formada (2ª Lei de Faraday). C. Um Faraday vale _________ Coulombs. D. _____________ de electrões é a quantidade de electrões que transporta a carga de 1 Faraday. 5. Qual é a massa de sódio que é produzida numa electrólise do cloreto de sódio fundido em que se utilizam 48250 C? 6. Numa electrólise de cloreto de sódio fundido utilizam-se 9650 C. A. Calcule a massa do gás cloro produzida. B. Calcule o volume do gás cloro formado nas CNTP. 7. Uma corrente de intensidade igual a 10 A atravessa durante 5 min uma célula electrolítica contendo sulfato de níquel (II). Qual é a massa de níquel depositada no cátodo? 8. Calcule o volume do gás cloro libertado nas CNTP na electrólise da solução aquosa de cloreto de sódio, utilizando uma corrente de 0.965 A, durante 1 min e 50 s.

The lifestyle, to which the majority of World societies are used to, is based on energy consumption. Since the Industrial Revolution, the bulk of that consumption has been accomplished by burning cheap fossil fuels. Lately, however, the depletion of those resources, as well as the increase in the consumption, especially in the so called developing countries, have produced a boost in the prices. Therefore, the investigation work on the development of alternative energy sources has seen a significant increase during the last years. This work starts by performing an analysis of the present World energy situation (2010), based on annual reports from different entities. After that, a proposal for the world energy supply, defended by some authors, is presented: the so called "Methanol Economy". The relevance given to this theory gives rise to interest in the concept of a Direct Methanol Fuel Cell (DMFC).

h i g h l i g h t s g r a p h i c a l a b s t r a c t Hybrid Co x Ni 1Àx (OH) 2 nanosheets can be prepared via a facile microwave-assisted route. The Co:Ni ratio depended size and crystal structure were demonstrated. The Co:Ni ratio depended electrochemical performance was proved. Co 0.2 Ni 0.8 (OH) 2 hexagonal nanosheets deliver a high specific capacitance of 1170 F g À1 at a current density of 4 A g À1 .

The mechanism of gold dissolution in acidic thiourea (Tu) solutions was investigated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV). CV over the potential range of À0.3 to 0.75 V vs. SCE shows peaks for the Tu/FDS (formamidine disulfide) and Au=AuðTuÞ þ 2 redox reactions. An oxidation peak associated with gold dissolution occurs at / P 0.36 V vs. SCE. This peak is often not observed in the first scan and its presence and magnitude are sensitive to the positive sweep potential limit of the first scan. FDS addition to the solution or adsorbed on the electrode has a strong catalytic effect and makes gold dissolution peak shift to lower potential during the first scan. This catalytic effect is identical to that exerted by scanning to higher potential. Tu/FDS ratio has a significant effect on thiourea stability, and it should be about 10:1 for the minimum thiourea decomposition and maximum gold dissolution rate. EIS results at 0.5À0.7 V vs. SCE with only Tu initially present in solution reveal a high-frequency capacitive loop associated with double layer charging, a medium-frequency inductive loop associated with FDS adsorption, and a low-frequency capacitive loop related to Tu oxidation. It appears that FDS adsorption on the gold surface activates the dissolution of gold and inhibits the oxidation of Tu.

Redox flow batteries and in particular the vanadium redox flow battery (VRFB) are in an advanced state after many work performed in conversion, storage, supply of energy from natural sources or electrical energy and the many applications. These batteries when utilized for large scale grid storage must have long live, durability for large numbers of charge/discharge cycles, high round-trip efficiency, rapid response to changes and reasonable capital cost. The power and energy capacity of the vanadium redox flow battery (VRFB) system can be separated; the power of the system is determined by the number of cells in the stack and the size of the electrodes whereas the energy storage capacity is determined by the concentration and volume of the electrolyte. In this article we present a general view of the vanadium redox flow cell and battery, its composition, properties and applications, and some results obtained in our laboratory as the voltage (1.47), charge yield (92.37), voltage yiel...

Bidimensional spectroelectrochemistry is an analytical technique that provides simultaneously one electrochemical and two spectroscopic signals. Taking the plane of the electrode surface as a spatial reference, normal-beam and parallel-beam UV-Vis absorbance signals are simultaneously obtained, which convey important information about the electrochemical systems studied. A new bidimensional spectroelectrochemistry cell is presented in this work. Based on a previous model, the new cell uses a reflection probe to enhance the normal-beam signal. Moreover, the new arrangement of the normal-beam allows us to use any kind of solid electrode. The new cell is validated using a standard system, o-tolidine. The usefulness of the cell is demonstrated by studying the electrically controlled release of hexacyanoferrate from a polypyrrole film. Our experiments show that not only hexacyanoferrate but also oligomers retained in the film are released.

Chicken egg white protects the embryo from bacterial invaders by presenting an assortment of antagonistic activities that combine together to both kill and inhibit growth. The key features of the egg white anti-bacterial system are iron restriction, high pH, antibacterial peptides and proteins, and viscosity. Salmonella enterica serovar Enteritidis is the major pathogen responsible for egg-borne infection in humans, which is partly explained by its exceptional capacity for survival under the harsh conditions encountered within egg white. However, at temperatures up to 42 • C, egg white exerts a much stronger bactericidal effect on S. Enteritidis than at lower temperatures, although the mechanism of egg white-induced killing is only partly understood. Here, for the first time, the impact of exposure of S. Enteritidis to egg white under bactericidal conditions (45 • C) is explored by global-expression analysis. A large-scale (18.7% of genome) shift in transcription is revealed suggesting major changes in specific aspects of S. Enteritidis physiology: induction of egg white related stress-responses (envelope damage, exposure to heat and alkalinity, and translation shutdown); shift in energy metabolism from respiration to fermentation; and enhanced micronutrient provision (due to iron and biotin restriction). Little evidence of DNA damage or redox stress was obtained. Instead, data are consistent with envelope damage resulting in cell death by lysis. A surprise was the high degree of induction of hexonate/hexuronate utilization genes, despite no evidence indicating the presence of these substrates in egg white.

CoOOH nanolayers were first prepared by the successive ionic layer deposition (SILD) method using aqueous Co(OAc) 2 and K 2 S 2 O 8 solutions. The obtained nanolayers were investigated by SEM, EDX, XRD, FTIR spectroscopy and electrochemical techniques. SEM images showed that the layers formed by nanosheets of size approximately 80-100 nm which had a hexagonal crystal structure. Electrochemical study of nickel foam electrodes modified by CoOOH layer prepared by 50 SILD cycles demonstrates that specific capacitance of the film is 1520 F/g at current density 1 A/g. Repeated cycling for 1000 charge-discharge cycles demonstrates 2% capacitance fade, so such electrodes may be used as pseudocapacitor electrodes.

Successive ionic layer deposition (SILD) of NiO 1+x •nH 2 O nanolayers was first performed by an oxidation-reduction route using a Ni(NO 3) 2 and K 2 S 2 O 8 solutions. The obtained nanolayers were characterized by SEM, EDX, XRD, XPS, UV-Vis and FTIR spectroscopy and electrochemical techniques. The results showed that the as-synthesized product is formed by nanosheets with a thickness of 6-12 nm, having cubic crystal structure of NiO and rhombohedral structure of γ-NiOOH. Electrochemical characterization of the sample prepared by 100 cycles of SILD indicated a capacitive behavior with the specific capacitance value of 1015 F/g at a current density of 1 A g-1 in 1 mol L-1 KOH aqueous solution. Repeated cycling for 3000 chargedischarge cycles demonstrate 10% capacitance fade relative to the initial values. The presented convenient route of synthesis may be used for the preparation of NiO 1+x •nH 2 O nanolayers with high surface area and a large capacitance.

Oxidation of [Mo(CN)8]4-by [Mrucdtaj]", studied as a function of disappearance of [Mntcdtaj] at 510 nm, is a first order reaction with respect to both the ions. The linear plot between kob• and [WI with intercept indicates two paths; one independent (k) of and the other (kH) dependent on [W]. These paths are ascribed to the protonation equilibrium between [Mntcdtaj]" and H[Mn(cdla)], by analogy to the similar equilibrium existing in [Mn(III)edta)]-complex, and is more likely than the equilibrium involving the protonation of [Mo(CN)8(ion. The alkali metal cations (M") catalyze the observed rate in the order K+ > Na+ > Li+ ion. The data provide linear correlations between kobJ[Mo(CN)g4-] and rM"], between kobs/[Mo(CN)g 4-] and polarisability of alkali metal cations beside a linear plot between kobs/[Mo(CN)g 4-) and .,fJ!/(1 + .,fJ!) with a predictable slope-4 for the reaction between [Mntcdta)]" and [Mo(CN)g)4-. The first correlation, indicative of the ion-pair formation, is not favoured because the kobsvalue did not show sign of saturation. The second correlation indicates the formation of a bridge by the alkali metal ion between the oxidant and reductant species. The rate constants k and kH at 25°Care (7.32 ± O.17)x10 3 drn" mol? S-I and (1.3 ± 0.02)X10 7 dm" mol? S-I respectively. The related values .of the enthalpy and entropy

Cytochrome c was electrostatically immobilized onto a COOH-terminated alkanethiol self-assembled monolayer (SAM) on a gold electrode at ionic strengths of less than 40 mM. Scanning electrochemical microscopy (SECM) was used to simultaneously measure the electron transfer (ET) kinetics of the bimolecular ET between a solution-based redox mediator and the immobilized protein and the tunneling ET between the protein and the underlying gold electrode. Approach curves were recorded with ferrocyanide as a mediator at different coverages of cytochrome c and at different substrate potentials, allowing the measurement of k BI) 2 × 10 8 mol-1 cm 3 s-1 for the bimolecular ET and k°) 15 s-1 for the tunneling ET. The kinetics of ET was also found to depend on the immobilization conditions of cytochrome c: covalent attachment gave slightly slower tunneling ET values, and a mixed CH 3 /COOH-terminated ML gave faster tunneling ET rates. This is consistent with previous studies and is believed to be related to the degree of mobility of cyt c in its binding configuration and its orientation with respect to the underlying electrode surface.

The redox properties of a series of 1-aza-, 1,5-diaza-and 1,8-diazaanthracene-4,9,10-triones are reported. The results obtained show that the presence of electron-withdrawing heterocyclic nitrogen atoms causes an increase of the reduction potentials, and also the expected similar effect of electron-withdrawing substituents. /^-substituted derivatives exhibited a reduction at ca.-1.45 V, which is assigned to the α,β-unsaturated carbonyl system. In contrast with their 2-oxo vinylogues, 1,5-diaza-and 1,8-diazaanthracene-4,9,10-triones show three reduction potentials. On the basis of the results obtained with W-substituted derivatives, the first of these potentials is attributed to the presence of detectable amounts of the 4-hydroxy-tautomers.

SummaryAb initio quantum chemical computations at the Hartree-Fock 6-31g** level of theory were performed on pterin, 7,8-dihydropterin and 5,6,7,8 -tetrahydropterin. The resulting electronic charge density functions and the electrostatic potential functions of the molecules are visualized by graphical software. The results demonstrate the profound changes in electronic properties among these structurally closely related compounds. Our contribution may serve as a basis for deeper insight into the molecular characteristics, also of other chemically or biologically important pterin derivatives of different oxidation state.

The effects of 17 different pteridine derivatives on rat liver microsomal cytochrome P-450 catalyzed degradation of aminoantipyrin were studied. Neopterin (41% of control), biopterin (42%), monapterin (73%), pterin (74 %), luma zine (75%) and 6-methylpterin (77%) significantly inhibit the degradation of aminoantipyrin. 6,7-Dimethylpterin (80 %) and 6-hydroxymethylpterin (89%) show weak but non-significant effects, and the remaining pteridine derivatives investigated (pterin-6-carboxylate, pterin-7-carboxylate , pterin-6-aldehyde, 7,8-dihydro-neopterin, 7,8-dihydro-biopterin, sepiapterin, xanthopterin, isoxanthopterin, and leukopterin) do not interact with the enzyme system. In addition, spectroscopic investigations were performed for colourless pteridine derivatives. Neopterin, biopterin, monapterin and pterin yielded type II binding spectra, indicating their binding to the heme iron of the active center of the enzyme. In agreement with the inhibition studies, 7,8-dihydroneopterin and 7,8-dihydrobiopterin did not exhibit spectroscopic evidence tor their interaction with the enzyme system. When attempting to correlate structural features of the pteridine compounds with their effect on the cytochrome P450 system , presence of a hydroxy function at C 2 ' of an alkyl sidechain at C 6 of the ring system was found to be particularly important for inhibition of aminoantipyrin degradation, while a 7,8-dihydro structure has the opposite effect. Interestingly, pteridines strongly interacting \vith the cytochrome P450 system also cause strong enhancement of radical-induced luminol-dependent chemiluminescence and of the growth-inhibitory potential of radical-yielding disinfectants towards bacteria, •while 7,8-dihydropteridines in these other experimental systems sh ow strong scavenger activity.

Summary In order to investigate the stabilities of different tautomeric forms of pteridine derivatives with a phenacetyl side chain in the 6- or 7-position, we have performed ab initio quantum chemical geometry optimizations of both the keto form and the vinylogous amide form of 6- and 7-phenacetyl pterin. The results are in accordance with experimental expectations: the keto form is slightly more stable for the 6-substituted derivative (1 .8 kcal per mol). while the vinylogous amide form is substantially more stable for the 7-substituted compound (8 .7 kcal per mol). The vinylogous amide forms are planar molecules, and this geometry enables the interaction between the hydrogen atom at N-5 (or N-8) and the carbonyl function of the side chain. Inspection of the calculated electron densities (population analysis) underlines the suggestion that the vinylogous amide form of 7-phenacetyl pterin is stabilized by a shift of electron density from the nitrogen bonded to C-2 to the carbonyl o...

We present here a tandem redox reaction strategy for building layered V 2 O 5 (LVO), conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT), and layered MnO 2 (LMO) into a sandwich structure LVO\PEDOT\LMO. The fabrication process consists of two redox reactions: i) the oxidizing polymerization of PEDOT on LVO nanosheets to form a conformal coating (LVO\PEDOT); and ii) the reduction of KMnO 4 by PEDOT to generate LMO nanoplates that stacked onto the LVO\PEDOT (LVO\PEDOT\LMO). This approach to the fabrication of a complex structure eliminates the use of any extra toxic oxidizing/reducing agents. Using LVO aerogel as the starting material, the total reaction time can be as short as 10 min. Asymmetric supercapacitors built from LVO\PEDOT\LMO cathode and active carbon (AC) anode (LVO\PEDOT\LMO||AC) using Na 2 SO 4 aqueous electrolyte showed an energy density of 39.2 Wh kg-1 (based on active materials), which is among the highest reported for supercapacitors with neutral aqueous electrolytes. The LVO\PEDOT\LMO||AC supercapacitors also offered high rate capability (21.7 Wh kg-1 at 2.2 kW kg-1) and good cycle stability (93.5 % capacitance retention after 3000 cycles). These results demonstrate that the green tandem redox

In the present article, highly capacitive NiMn-LDHs/GO composite of electrode material has been the synthesized for supercapacitor energy storage. Various analytical techniques (particularly X-ray diffraction (XRD), Raman spectroscopy, high resolution transmission electron microscopy (HRTEM), and scanning electron microscope (SEM)) have been employed to characterize the as-synthesized NiMn-LDHs/GO. The Microscopic images obtained using HRTEM analysis clearly reveal the formation of lattice fringe pattern (lattice spacing as ~ 0.22 nm) for GO, whereas SEM images shows highly porous nature. The super-capacitive performance of the as-synthesized electrode material have been accessed through an electrochemical work station comprising of a 3-electrode system. The working electrode made up of NiMn-LDHs/GO (Active material) on Ni foil (working electrode) with the help of PVDF (binder), has shown speci c capacitance of 1964 F g−1 at current density of 1 A g−1 with Galvanostatic charging/discharging (GCD) technique. It has also shown remarkable cyclic stability with a capacitance retention of 98% after 2000 cycles. The high-power density (401 W/kg) and energy density (17.78 Wh/kg) signify the high-level electrochemical supercapacitor behaviour in charge storage applications.

In the present article, highly capacitive NiMn-LDHs/GO composite of electrode material has been the synthesized for supercapacitor energy storage. Various analytical techniques (particularly X-ray diffraction (XRD), Raman spectroscopy, high resolution transmission electron microscopy (HRTEM), and scanning electron microscope (SEM)) have been employed to characterize the as-synthesized NiMn-LDHs/GO. The Microscopic images obtained using HRTEM analysis clearly reveal the formation of lattice fringe pattern (lattice spacing as ~ 0.22 nm) for GO, whereas SEM images shows highly porous nature. The super-capacitive performance of the as-synthesized electrode material have been accessed through an electrochemical work station comprising of a 3-electrode system. The working electrode made up of NiMn-LDHs/GO (Active material) on Ni foil (working electrode) with the help of PVDF (binder), has shown specific capacitance of 1964 F g−1 at current density of 1 A g−1 with Galvanostatic charging/di...

The application of layered double hydroxides for supercapacitors is drastically impaired by their adverse agglomeration and poor conductivity. Herein, we have successfully deposited ultrathin nickel cobalt aluminum layered double hydroxide nanopetals onto a conductive three-dimensional graphene structure via dept dip-coating and hydrothermal reaction. Under this facile process, the as-fabricated

In this paper we present the electrochemical study of self-assembled monolayer (SAM) created of aliphatic 1-hexadecanethiol (1-HDT) molecules adsorbed onto the gold and Au/Cr QCM crystal surfaces. We investigated the influence of 1-HDT concentration and scan rate on potential values for both adsorption and desorption processes. Our study introduces elimination voltammetry with linear scan (EVLS) as a new, improved and sufficient approach to study and characterize the SAM creation. Furthermore, formation of SAM was studied by cyclic voltammetry, electrochemical quartz crystal microbalance (QCM) and atomic force microscopy (AFM). Our study showed that the EVLS is suitable method for SAM study and gave detail information about the processes on the electrode surface. It was found that the adsorption of 1-HDT molecules on QCM crystal was more extensive than on Au electrode, i.e. molecules of 1-HDT molecules had better coverage on QCM crystal. The incomplete desorption of previously adsorbed 1-HDT from the electrode surface was observed by QCM measurements. AFM measurements confirmed that created SAM was homogenous without defects. The application of EVLS to the voltammetric signals resulted in significant increase of peak height and revealed a kinetically controlled reaction before an electron transfer proceeding in adsorbed state for oxidation processes corresponding to the 1-HDT monolayer adsorption and dithiol formation on both electrodes. A kinetically controlled reaction was detected also before the reductive desorption of previously adsorbed 1-HDT on both the electrodes.

All classes of pterins, fully reduced tetrahydropterins, aromatic pterins and dihydropterins have been investigated upon their effects on radical mediated reactions. Meanwhile all these classes were shown to act as both, proand antioxidants by a number of different methods including chemical, biochemical and biological systems. From reduced pterins radicals including oxygen-, nitrogen- and pterin-radicals arc formed enzymatically and non-enzymatically, reduced pterins react with free radicals and serve as reductive agents. All classes of pterins may interfere with enzymes involved in radical formation. Upon the diversity of possibilities the net effect of a particular compound is a question of the experimental settings and the physiological relevant role often remains obscure.

The effects of 17 different pteridine derivatives on rat liver microsomal cytochrome P-450 catalyzed degradation of aminoantipyrin were studied. Neopterin (41% of control), biopterin (42%), monapterin (73%), pterin (74 %), luma zine (75%) and 6-methylpterin (77%) significantly inhibit the degradation of aminoantipyrin. 6,7-Dimethylpterin (80 %) and 6-hydroxymethylpterin (89%) show weak but non-significant effects, and the remaining pteridine derivatives investigated (pterin-6-carboxylate, pterin-7-carboxylate , pterin-6-aldehyde, 7,8-dihydro-neopterin, 7,8-dihydro-biopterin, sepiapterin, xanthopterin, isoxanthopterin, and leukopterin) do not interact with the enzyme system. In addition, spectroscopic investigations were performed for colourless pteridine derivatives. Neopterin, biopterin, monapterin and pterin yielded type II binding spectra, indicating their binding to the heme iron of the active center of the enzyme. In agreement with the inhibition studies, 7,8-dihydroneopterin and 7,8-dihydrobiopterin did not exhibit spectroscopic evidence tor their interaction with the enzyme system. When attempting to correlate structural features of the pteridine compounds with their effect on the cytochrome P450 system , presence of a hydroxy function at C 2 ' of an alkyl sidechain at C 6 of the ring system was found to be particularly important for inhibition of aminoantipyrin degradation, while a 7,8-dihydro structure has the opposite effect. Interestingly, pteridines strongly interacting \vith the cytochrome P450 system also cause strong enhancement of radical-induced luminol-dependent chemiluminescence and of the growth-inhibitory potential of radical-yielding disinfectants towards bacteria, •while 7,8-dihydropteridines in these other experimental systems sh ow strong scavenger activity.

This study presents new findings of the water/ethanol (ratio) influence on the aniline hydrochloride polymerization process in presence of ammonium persulfate. Water/ethanol mixtures in presence of monomer hydrochloride, as proved by the conductometric, spectrophotometric and refractometric investigations, are far from ideal solutions and promote a partitioned environment, for the polymerization process. By controlling this key parameter (water/ethanol ratio) the polymerization can be shifted from a initial dispersion process to a solution one, followed by precipitation. The associated phenomena revealed modification in terms of conversion, structure (FTIR, UV-VIS), morphology (SEM), thermal stability and doping agent retention (TGA-DTG).

In this work, electrochemical sensors were designed and
manufactured using a Printed Circuit Board coated with copper
foil as substrate. These sensors were developed using a matrix
of the conductive polymer polyaniline and the nanostructured
compound of reduced graphene oxide, and were applied two
different drying methods: infrared light and spin coating. Then,
the  glucose oxidase enzyme of high specificity was immobilized
with glutaraldehyde solution. The sensors were analyzed in the
presence of a D-Glucose solution at a concentration of 16 mM.
The electrochemical activity was measured using the cyclic
voltamperometry technique. As for the results, those samples
dried with infrared light displayed better performance at scan
rates of 0.3 to 0.8 mV/s with a  high charge transfer of 0.8
mV/s and reversibility. On the other hand, the electrodes dried
with the spin coating method did not show reversibility. With
this technique it is highly likely to develop biosensors to detect
glucose  in diabetic people  in Peru.

In vitiligo, a common skin disorder that produces white patches of depigmentation, 7,8-dihydropterins accumulate in the presence of high concentration of H 2 O 2. In this work, we present a study of the reaction between 7,8-dihydropterins and H 2 O 2. The rate of the reaction, as well as the products formed, strongly depend on the chemical structure of the substituents. Electron-donor groups as substituents are the most reactive derivatives and undergo oxidation of the pterin moiety. The corresponding bimolecular rate constants at 37 C in neutral aqueous solutions are reported. The biological implications of the results obtained are also discussed.

The heteroditopic receptors 1 and 2 firmly include an Ag I ion into the NS 2 O 2 crown and establish selective H-bond interactions with anions at the covalently linked urea/thiourea (U/T) subunit. Studies in MeCN solution showed that the metal center induces a 10 3 −10 6-fold enhancement of the anion association constant, due to a coordinative interaction with the O/S atom of the U/T moiety. In the presence of F-, the Ag−O interaction promotes the release of a proton from one of the urea N−H fragments. Ag I coordination to the S atom of the thiourea derivative 2 promotes the formation of unusually stable H-bond complexes with Cland Br- .

Successful osseointegration of orthopaedic and orthodontic implants is dependent on a competition between osteogenesis and bacterial contamination on the implant-tissue interface. Previously, by taking advantage of the highly interactive capabilities of silver nanoparticles (AgNPs), we effectively introduced an antimicrobial effect to metal implant materials using an AgNP/poly(dl-lactic- co-glycolic acid) (PLGA) coating. Although electrical forces have been shown to promote osteogenesis, creating practical materials and devices capable of harnessing these forces to induce bone regeneration remains challenging. Here, we applied galvanic reduction-oxidation (redox) principles to engineer a nanoscale galvanic redox system between AgNPs and 316L stainless steel alloy (316L-SA). Characterized by scanning electron microscopy , energy-dispersive X-ray spectroscopy, atomic force microscopy, Kelvin probe force microscopy, and contact angle measurement, the surface properties of the yield AgN...

Cyclic pyranopterin monophosphate (cPMP) is one of the most stable intermediates in Molybdenum cofactor (MoCo) biosynthetic pathway. In humans, synthesis of cPMP from Guanosine triphosphate (GTP) requires functional genes i.e. Molybdenum Cofactor Synthesis-1 (MOCS1) genes that contains for two catalytic proteins MOCS1A and MOCS1B. Importance of MOCS1A and MOCS1B for biosynthesis of MoCo reveals from the fact that its de ciency leads to MoCo type A de ciency. As there is no structure available for MOCS1 genes in the literature, tertiary structure of MOCS1 genes were investigated in this research via threading or folds recognition method by i-TASSER and validation was done using ERRAT, Verify3D and Ramachandran plots. Binding sites were predicted and validated. Docking of MOCS1A with GTP and MOCS1B with 3, 8 dihydroguanosine was done using Autodock via PyRx. Apart from this, highly con dent mutations were also predicted using SIFT and polyphen2 that can alter the structure and function of MOCS1 gene.

The electrochemical formation of a condensed methylene blue (MB+)/leucomethylene blue (LMB) monolayer at the sulphur covered gold electrode (1 M aqueous electrolyte solution, pH = 7.9) is reported. The strong interaction between MB+ and adsorbed sulphur in the monolayer is ascribed to a disulphide linkage between a sulphur adatom and the sulphur heteroatom of the perpendicularly oriented organic molecule. This binding also results in a change in the electrical properties of the sulphur monolayer, which increases the reversibility of the electron transfer in the fist adsorbed MB monolayer. The stability of the reduced monolayer at the Au-S/aqueous electrolyte interface is affected strongly by the type of anion (F-t Cl-3p NO;).

A new type of self-assembled monolayer (SAM) on gold has been reported. Electroactive SAMs of thionine formed on polyoriented gold and sulphur-modified polyoriented gold from aqueous thionine solutions of pH 7.9 have been characterized by voltammetry. In thionine SAMs formed on gold modified by a monolayer of sulphur adatoms the attachment takes place through S-S bonding between the S adatom and S heteroatom of thionine with edge-on orientation. A fast 2c reduction of thioninc molecules in the SAM, at potentials 150 mV more negative than the solution couple, leads to a complete detachment of the reduced molecules leaving the sulphur adlayer intact. In the thionine SAM formed on a flame-treated surface of polyoriented gold, the surface concentration of 4.59 × 10 m tool cm-2 corresponds to the most efficient packing of thionine molecules in a monolayer (end-on orientation). On 2c reduction of thionine molecules, the initial thionine SAM transforms irreversibly to a new surface state with one-half of the initial surfacc concentration.

A new receptor named, 2-(2-(2,4-dinitrophenyl)hydrazono)2H-indene-1,3-dione, used as a colorimetric sensor based on 2,4-dinitrophenylhydrazone derivative of ninhydrin was synthesized by simple step with good yields and characterized by IR and 1 H, 13 C NMR and MS spectroscopic techniques. The anion recognition properties were studied by UV-Vis spectroscopic technique. The results showed that the receptor had a higher affinity to F-, CN-, H2PO4-, CH3COO-and OH-, but showed no evident binding with Cl-, Brand I-. Binding of the reseptor to anions such as CN-, AcO-, F-, H2PO4-and OHexhibited an obvious color change from greenish yellow to purplish blue, which was possible to observe by the naked eye. Ninhydrin Naked-eye Anion receptor UV-Vis titration Association constant 2,4-Dinitrophenylhydrazine

The kinetics of photooxidation of pyruvate was investigated in presence of zinc oxide catalyst under illumination of visible light. The influence of different parameters such as concentrations of reactants, amount of catalyst and irradiation time was studied on the redox reaction under pseudo‐first order conditions. The results indicated that amount of catalyst, presence of electron accepter in solution and irradiation time was the key factors influencing the efficiency of photo‐oxidation of pyruvate to acetyl.

Organic field‐effect transistors (OFETs) are considered in technological applications for which low cost or mechanical flexibility are crucial factors. The environmental stability of the organic semiconductors used in OFETs has improved to a level that is now sufficient for commercialization. However, serious problems remain with the stability of OFETs under operation. The causes for this have remained elusive for many years. Surface potentiometry together with theoretical modeling provide new insights into the mechanisms limiting the operational stability. These indicate that redox reactions involving water are involved in an exchange of mobile charges in the semiconductor with protons in the gate dielectric. This mechanism elucidates the established key role of water and leads in a natural way to a universal “stress function”, describing the stretched exponential‐like time dependence ubiquitously observed. Further study is needed to determine the generality of the mechanism and th...

High-performance yet thin hybrid supercapacitors (HSC) are urgently needed to meet the increasing demands of wearable and portable electronic devices. Nevertheless, most of the current electrode designs employed to enhance the electrode capacity and conductivity provide limited volumetric capacity because they commonly rely on macroscopic, heavy support materials such as nickel foam or carbon cloth. Hence, micro-and nanostructuring strategies towards tailored electrode architectures will be vital for their utilization in practical applications. Herein, a three-dimensional (3D) self-supported hierarchical electrode was obtained by directly growing NiCo layered double hydroxide (NiCo-LDH) nanosheets on a Ni nanotube network (Ni-NTNW) via electrodeposition. The resulting electrode takes advantage of the large interface and the high redox activity of the two-dimensional (2D) coating nanosheets, whose properties are augmented by the highly porous network architecture of the onedimensional (1D) Ni-NTNW support, which enables fast mass transfer and acts as a "highway" for fast electron transfer. The fabricated NiCo-LDH@Ni-NTNW architecture replicates the thickness of the parent template (20 mm) employed for the electroless plating of the Ni-NTNW, resulting in an ultrathin battery-type electrode with a superb volumetric capacity of 126.4 C cm À3 , remarkable rate capability, and outstanding cycling stability. Additionally, the assembled NiCo-LDH@Ni-NTNW//activated carbon (AC) HSC can deliver a high volumetric capacitance of 76.7 F cm À3 at a current density of 1 mA cm À2. Meanwhile, it exhibits a high energy density of 14.7 mWh cm À3 with a maximum power density of 4769 mW cm À3 , surpassing most state-of-the-art supercapacitors that deliver high volumetric energy density. As such, hybrid core-shell nanotube networks represent an up-and-coming design paradigm for highperformance supercapacitor devices in portable devices.

We investigated the photoelectrochemical characteristics and photo-stability of Cu 2 O layered on a copper plate using a hydrophobic ionic liquid. Our findings revealed that Cu 2 O is stable under white light irradiation, provided water is removed from the electrolyte. Methyl viologen derivative, a well-established electron acceptor, was introduced to the ionic liquid electrolyte, allowing the photo-induced electron transfer reaction at the Cu 2 O/electrolyte interface to be characterized. The methyl viologen derivative exhibited two distinct redox reactions at −0.56 V and −0.98 V vs. Ag/AgCl, clearly indicating that no dimer formation or co-proportionation reaction occurred. The excessive photocurrents being continuously generated resulted from a viable photo-induced electron transfer reaction from the Cu 2 O to the acceptor. However, in contrast, the reduction of the Cu 2 O by water in the aqueous solution causes this electron transfer to be inhibited. We further demonstrate that these findings are vital to understanding the role of the Cu 2 O and its photoelectrochemical applications.

We report a novel photonic processing technique as a next-generation cost-effective method to instantaneously synthesize nanostructured manganese-cobalt mixed oxide reduced graphitic oxide (Mn-Co-rGO) as supercapacitor electrodes for energy storage.

The redox reactions of the cytochrome c oxidase from Paracoccus denitrificans were investigated in a thin‐layer cell designed for the combination of electrochemistry under anaerobic conditions with UVIVIS and IR spectroscopy. Quantitative and reversible electrochemical reactions were obtained at a surface‐modified electrode for all cofactors as indicated by the optical signals in the 400–700 nm range. Fourier transform infrared (FTIR) difference spectra of reduction and oxidation (reduced‐minus‐oxidized and oxidized‐minus‐reduced, respectively) obtained in the 1800‐1000 cm−1 range reveal highly structured band features with major contributions in the amide I (1620–1680 cm−1) and amide II (1580‐1520 cm−1) range which indicate structural rearrangements in the cofactor vicinity. However, the small amplitude of the IR difference signals indicates that these conformational changes are small and affect only individual peptide groups. In the spectral region above 1700 cm−1, a positive peak...

An easy-to-synthesis chemosensor was synthesized and employed as a selective optical chemosensor for fluoride through naked eye detection, which allow us to detect and estimate the concentration of fluoride ion accurately up to 2 μMviaratiometric responses.