Electron Donor Compounds Research Articles

The Effect of Fermentation Time Variation on Antioxidant Activity of Fermented Robusta Coffee Leaves (Coffea canephora Pierre ex A.Froehner) Brew

Antioxidants are electron-donor compounds that can delay, slow down and prevent free radical reactions. Fermentation is a chemical change that occurs due to the activity of microorganisms which can increase the amount of phenols in tea thereby increasing its antioxidant activity. Fermentation is carried out with the help of a Symbiotic Culture of Bacteria and Yeast (SCOBY) culture, which is commonly used in the production of kombucha. Kombucha is a fermented tea drink produced from leaves that contain high phenols such as robusta coffee leaves (Coffea canephora Pierre ex A.Froehner). Factors that affect the fermentation process are pH and fermentation time. This study aimed to explain the effect of fermentation time on the antioxidant activity of fermented robusta coffee leaves brew. Brewed robusta coffee leaves were made by brewing robusta coffee leaves simplicia powder, adding kombucha liquid starter, then fermented for 0; 3; 7; 14; and 21 days, then pH and antioxidant activity was measured using UV-Visible spectrophotometer using the 2,2-dipheny-1,1-picrylhydrazyl (DPPH) at a wavelength of 516 nm. This study showed that 0; 3; 7; 14; and 21 days fermented robusta coffee leaves brew have pH of 6,07; 4,62; 4,07; 3,21; and 2,74, and IC50 values is 285,1645 μg/ml; 219,7012 μg/ml; 192,2325 μg/ml; 187,0434 μg/ml; and 173,9249 µg/ml. There is an effect of fermentation time variation on the antioxidant activity of fermented robusta coffee leaves brew. Keyword: Antioxidant, Fermentation, pH, Robusta coffee leaves, Time variation

Transcriptional and Metabolic Response of a Strain of Escherichia coli PTS- to a Perturbation of the Energetic Level by Modification of [ATP]/[ADP] Ratio.

The intracellular [ATP]/[ADP] ratio is crucial for Escherichia coli's cellular functions, impacting transport, phosphorylation, signaling, and stress responses. Overexpression of F1-ATPase genes in E. coli increases glucose consumption, lowers energy levels, and triggers transcriptional responses in central carbon metabolism genes, particularly glycolytic ones, enhancing carbon flux. In this contribution, we report the impact of the perturbation of the energetic level in a PTS- mutant of E. coli by modifying the [ATP]/[ADP] ratio by uncoupling the cytoplasmic activity of the F1 subunit of the ATP synthase. The disruption of [ATP]/[ADP] ratio in the evolved strain of E. coli PB12 (PTS-) was achieved by the expression of the atpAGD operon encoding the soluble portion of ATP synthase F1-ATPase (strain PB12AGD+). The analysis of the physiological and metabolic response of the PTS- strain to the ATP disruption was determined using RT-qPCR of 96 genes involved in glucose and acetate transport, glycolysis and gluconeogenesis, pentose phosphate pathway (PPP), TCA cycle and glyoxylate shunt, several anaplerotic, respiratory chain, and fermentative pathways genes, sigma factors, and global regulators. The apt mutant exhibited reduced growth despite increased glucose transport due to decreased energy levels. It heightened stress response capabilities under glucose-induced energetic starvation, suggesting that the carbon flux from glycolysis is distributed toward the pentose phosphate and the Entner-Duodoroff pathway with the concomitant. Increase acetate transport, production, and utilization in response to the reduction in the [ATP]/[ADP] ratio. Upregulation of several genes encoding the TCA cycle and the glyoxylate shunt as several respiratory genes indicates increased respiratory capabilities, coupled possibly with increased availability of electron donor compounds from the TCA cycle, as this mutant increased respiratory capability by 240% more than in the PB12. The reduction in the intracellular concentration of cAMP in the atp mutant resulted in a reduced number of upregulated genes compared to PB12, suggesting that the mutant remains a robust genetic background despite the severe disruption in its energetic level.

The Chemical Sensitivity of Hybrid Porphyrin Materials

Porphyrins and corroles have been used in the last two decades to prepare sensor arrays for a variety of applications [1]. The wide chemical interactivity of these porphyrinoids sustains these applications making possible the measurement of complex patterns of volatile compounds. The interplay between the metal ion, the aromatic ring and the peripheral compounds establishes unique selectivity patterns which are fundamental elements for sensor array design and development. Films of porphyrins and corroles can be adequately applied to inorganic surfaces making possible the preparation of different kinds of chemical sensors. Among them mass transducers, such as Quartz Microbalances (QMBs), have been found particularly suitable for several applications. QMBs do not select the different interaction mechanisms, thus this transducer offer the unique chance to investigate the whole bouquet of interactions established between the volatile compounds and the sensitive layers. Porphyrins and corroles coated QMB sensor arrays have been successfully used in several application in particular to investigate in humans the relationships between volatilome and pathologies. Results include the diagnosis of lung cancer from breath [2], kidney cancer from urines [3], and COVID-19 from blood serum [4].In the last years, we have been interested in replicating the behavior of QMB sensor arrays with other transduction principle which enables a more simple sensor system design and even the integration of sensors in wearable supports. To this regard the simplest sensor is that based on electric impedance variation. For this scope porphyrins have been grafted onto the surface of nanostructures that can provide a change of impedance as a result of the chemical interaction between porphyrinoids and volatile compounds. For instance, layers of porphyrinoids coated ZnO nanoparticles shown sensitivity towards a large spectra of compounds [5]. Exploiting the optical properties of porphyrins, the sensitivity of this sensors can be triggered by light. As a result, these devices show a negative sensitivity to electron donor compounds (e.g. amines) and a positive sensitivity respect to other compounds. This property can be fruitfully exploited in sensor arrays configuration to classify complex samples such as foods and furthermore to detect spoilage processes. Another example is provided by porphyrnoids coated silica nanoparticles. In this case, the dielectric properties of silica are exploited to develop capacitive sensors whose capacitance is modulated by the absorption of volatile compounds. These sensors retains the chemical sensitivity properties of porphyrins allowing for instance to reproduce the results of the QMB sensors in the identification of COVID-19 blood serum sample.

Chain elongation may occur in protein mixed-culture fermentation without supplementing electron donor compounds

This study focuses on verifying the occurrence of elongation processes during protein mixed culture fermentation, without the supplementation of electron donor compounds. During casein mixed-culture fermentation at pH 5, it was observed that longer chain volatile fatty acid production increased, which could not be justified by the associated amino acid consumption. Consequently, the occurrence of chain elongation processes was hypothesized. To verify this hypothesis, three casein batch tests, with and without acetic acid initial supplementation, were performed at pH 5. The results suggest that acetic and propionic acids are indeed consumed to selectively generate n-valeric acid through the coupling with electron donor amino acids, whose consumption was further verified through the amino acid analysis. Prolonged simultaneous availability of suitable amino acids and short chain volatile fatty acids and an acid equivalent concentration threshold were identified as key parameters for the occurrence of chain elongation. The supplementation of acetic acid at the beginning of the test changed the selectivity of the elongation process, promoting n-butyric and iso-valeric production. The associated mechanisms were preliminary conceptualized, constituting a first step for further studies on the subject. To the best of our knowledge, this is the first study demonstrating the feasibility of chain elongation processes during protein mixed culture fermentation without electron donor supplementation.

Molecular photonics of dienones based on cycloalkanones and their derivatives

Spectroscopic, luminescent, and spectral kinetic properties of cycloalkanone-based dienones and their diethylamino, methylthio, methoxy, and dimethoxy derivatives were studied. The presence of electron-donating substituents results in a red shift of the absorption and fluorescence spectral maxima. A laser pulse causes dienones to undergo intersystem crossing to the underlying triplet state with a lifetime of 0.2–40 μs as well as results in the formation of stable photoproducts capable of photoinduced conversion to the initial dienones. It also gives rise to intermediate products resulting from redox photoreactions of 2,4-bis(4-diethylaminobenzylidene)cyclobutanone in methanol in the presence of electron donor (ascorbic acid) and acceptor (para-nitroacetophenone) compounds.

Atom transfer radical additions (ATRAs) promoted by catalytic amounts of amines: The effective iododifluoroalkylation of alkenes/alkynes

Rencently, fluoroalkylation reactions initiated via noncovalent interaction (halogen bond or EDA complexes) have become an attractive method access to fluoro-containing compounds, and most of those reactions were promoted by visible light and stoichiometric electron-donor compounds. Here, a novel atom transfer radical addition (ATRA) reaction promoted by catalytic amount of 1,4-dimethylpiperazine at heating condition is developed. This protocol enables a simple and practical alternative for the effective iododifluoroalkylation of alkenes or alkynes, which features synthetic simplicity, wide substrate scope and feasibility of product transformations.

Spontaneous and stimulated emission of thin-film polymer structures in the presence of nitrotoluene vapour

The features of spontaneous and stimulated emission of polyfluorenes, polyvinylcarbazole, and low-molecular-weight electron-donor compounds incorporated into various materials are studied in the presence of nitrotoluene vapour. Lasing in planar thin-film waveguides is achieved. The dynamics of the lasing spectra of a thin-film optical chemical sensor is presented. It is shown that the response time of the sensor in the lasing regime is 30 s before the lasing intensity decreases by 50% from the initial level.

Synthesis of Polypropylene in the Liquid Monomer in the Presence of a Titanium—Magnesium Catalyst: Effect of Various Internal Donors

The influence of supported titanium-magnesium catalysts with various internal and external donors on the propylene polymerization in the liquid monomer medium and the characteristics of the polypropylene formed were studied. The following internal donors were used: dibutyl phthalate, diisobutyl phthalate, 9,9′-bis(methoxymethyl) fluorene, and diethyl 2,3-diisopropylsuccinate. The catalysts studied allow synthesis of polypropylene with high isotacticity (>96%) and different molecular-mass distribution (Mw/Mn from 3.3 to 6.3). The influence of external donors (alicyclic, amine) in combination with phthalate and nonphthalate electron-donor compounds on the stereospecificity and activity of the catalysts and on their sensitivity to hydrogen was studied. The optimum catalytic systems for preparing polypropylene for various purposes can be found by varying pairs of internal and external donors.

Primary Productivity Was Limited by Electron Donors Prior to the Advent of Oxygenic Photosynthesis

AbstractTo evaluate productivity on the early Earth before the advent of oxygenic photosynthesis, we integrated estimates of net primary production by early anaerobic metabolisms as limited by geological fluxes of key electron donor compounds, phosphate, and fixed nitrogen. These calculations show that productivity was limited by fluxes of electron donor compounds to rates that were orders of magnitude lower than today. Results suggest that ferrous iron provided a minor fuel for net primary productivity compared to molecular hydrogen. Fluxes of fixed nitrogen and phosphate were in excess of demands by the electron donor‐limited biosphere, even without biological nitrogen fixation. This suggests that until life learned to use water as an electron donor for photosynthesis, the size and productivity of the biosphere were constrained by the geological supply of electron donors and there may not have been much ecological pressure to evolve biological nitrogen fixation. Moreover, extremely low productivity in the absence of oxygenic photosynthesis has implications for the potential scale of biospheres on icy worlds such as Enceladus and Europa, where photosynthesis is not possible and life would be unable to escape electron donor limitation.

Photocatalytic evolution of H2 from aqueous solutions of two-component electron-donor substrates in the presence of g-C3N4 activated by heat treatment in the KCl + LiCl melt

It has been shown that post-synthetic heat treatment of g-C3N4 in the melt of potassium and lithium salts leads to a significant increase of photocatalytic activity in the hydrogen formation from aqueous solutions of electron-donor compounds compared to the initial g-C3N4. This could be explained in terms of formation more crystalline graphitic carbon nitride (CGCN) with enhanced ability for absorption of higher amounts of visible light. Simultaneously, this treatment significantly decreases level of electron-hole recombination. It has been established that coincident use of two donors of different nature (organic acid and alcohol) with CGCN significantly increases rate of hydrogen formation. The possible explanation to this phenomenon could be find within acidic activation of CGCN. The influence of a number of factors on the efficiency of photocatalytic hydrogen production under visible light in systems based on the received carbon nitride has been investigated. The apparent quantum yields of the hydrogen evolution process with use of CGCN were determined as 23.6 and 5.6% at 405 and 435 nm, respectively.

Extracellular Electron Transfer via Outer Membrane Cytochromes in a Methanotrophic Bacterium Methylococcus capsulatus (Bath).

Electron exchange reactions between microbial cells and solid materials, referred to as extracellular electron transfer (EET), have attracted attention in the fields of microbial physiology, microbial ecology, and biotechnology. Studies of model species of iron-reducing, or equivalently, current-generating bacteria such as Geobacter spp. and Shewanella spp. have revealed that redox-active proteins, especially outer membrane c-type cytochromes (OMCs), play a pivotal role in the EET process. Recent (meta)genomic analyses have revealed that diverse microorganisms that have not been demonstrated to have EET ability also harbor OMC-like proteins, indicating that EET via OMCs could be more widely preserved in microorganisms than originally thought. A methanotrophic bacterium Methylococcus capsulatus (Bath) was reported to harbor multiple OMC genes whose expression is elevated by Cu starvation. However, the physiological role of these genes is unknown. Therefore, in this study, we explored whether M. capsulatus (Bath) displays EET abilities via OMCs. In electrochemical analysis, M. capsulatus (Bath) generated anodic current only when electron donors such as formate were available, and could reduce insoluble iron oxides in the presence of electron donor compounds. Furthermore, the current-generating and iron-reducing activities of M. capsulatus (Bath) cells that were cultured in a Cu-deficient medium, which promotes high levels of OMC expression, were higher than those cultured in a Cu-supplemented medium. Anodic current production by the Cu-deficient cells was significantly suppressed by disruption of MCA0421, a highly expressed OMC gene, and by treatment with carbon monoxide (CO) gas (an inhibitor of c-type cytochromes). Our results provide evidence of EET in M. capsulatus (Bath) and demonstrate the pivotal role of OMCs in this process. This study raises the possibility that EET to solid compounds is a novel survival strategy of methanotrophic bacteria.

Composition of Concentrates Isolated by Complexation with Aluminum and Zinc Halides from Petroleum Fuel Fractions during Their Desulfurization

An experimental study on obtaining concentrates of organic compounds from fuel fractions of petroleum by complexation with metal halides: aluminum chloride, aluminum bromide, anhydrous zinc chloride, and its crystal hydrate has been performed. Optimal conditions have been selected for the complexation reaction of aluminum and zinc halides with electron-donor compounds of diesel and jet fuels. The degree of removal of organic sulfur compounds from the diesel or jet fuel by complexation with aluminum chloride reaches 79.6 or 10.0 rel. %, respectively. It has been found that the concentrates obtained contain a large amount of normal and weakly branched alkanes, which form clathrates with polar components of the donor–acceptor complex (DAC). A mechanism is proposed for the intermolecular interaction of alkanes with the DAC components by hydrogen bonding with halogen, oxygen, and sulfur atoms.

Photocatalytic activity of nanostructured composites based on layered niobates and C3N4 in the hydrogen evolution reaction from electron donor solutions under visible light

Nanostructured composites based on layered niobates KNb3O8, K3Н3Nb10.8O30 and HNb3O8 as well as C3N4 were obtained. It was established that the rate of hydrogen evolution from electron donors water solutions under visible light using composites niobate/C3N4 as photocatalysts significantly exceeds the rate value for an individual C3N4. This phenomenon was explained by an effective separation of photogenerated charges between the components of the composite and thus a decrease of the electron-hole recombination. Transition from an individual C3N4 to the composites niobate/C3N4 allows significantly extend the list of an effective electron donor compounds for the photocatalytic hydrogen evolution process.

Real-time monitoring of intracellular redox changes in Methylococcus capsulatus (Bath) for efficient bioconversion of methane to methanol

This study aimed to develop a novel method for real-time monitoring of the intracellular redox states in a methanotroph Methylococcus capsulatus, using Peredox as a genetically encoded fluorescent sensor of the NADH:NAD+ ratio. As expected, the fluorescence derived from the Peredox-expressing M. capsulatus transformant increased by supplementation of electron donor compounds (methane and formate), while it decreased by specifically inhibiting the methanol oxidation reaction. Electrochemical measurements confirmed that the Peredox fluorescence reliably represents the intracellular redox changes. This study is the first to construct a reliable redox-monitoring method for methanotrophs, which will facilitate to develop more efficient methane-to-methanol bioconversion processes.

Introduction and theoretical investigation of new azafullerene structures with nitrogen belts

Two isomers of each nitrogen-doped fullerenes C42N18 and C40N20 have been studied, including those with separated nitrogen atoms and those with a nitrogen belt in a chain form in equator of these molecules. All computations have been carried out using Gaussian 03 and NBO 5.0 programs, employing HF and DFT (at B3LYP level) methods at different basis sets. Several structural parameters for each of the isomers have been studied and the results for the isomers with a nitrogen belt have been compared with those of the isomers with separated nitrogen atoms and also with those of C60 fullerene. The structural studies show that the nitrogen belt isomers, with more all-carbon hexagonal and some nonagonal and decagonal rings, have reasonable stability. The electronic properties such as atomization energy, ionization potential, electron affinity, electronegativity, HOMO/LUMO surface energies and their gap, dipole moment, polarizability, hyperpolarizability, NBO charges and harmonic vibrational frequencies of the target compounds and C60 fullerene have been calculated. The results show that the isomers with a belt of the nitrogen atoms could have reasonable stabilities, showing relatively high electron accepting characters. They also could form donor–acceptor pairs with electron-donor compounds having close HOMO–LUMO gap, such as the isomers containing separated nitrogen atoms, and could be used for potential applications in molecular electronics.

A Novel Organic Electrical Memory Device Based on Metallofullerene-Grafted Polymer

Organic memory materials have advantages in flexible, large area film-forming, and low cost compared with inorganic storage materials. Developing new materials with high read-write speed, low-power consumption, multi-value storage capacity and other excellent properties has been a subject for the study of next-generation non-volatile storage devices. Metallofullerenes could be used either as electron acceptor or as electron donor to form charge transfer compound with polymers containing electron withdrawing or electron donor compounds. We successfully used metallofullerene-based polymer to fabricate ITO/Gd@C82-PVK/Al sandwich nonvolatile memory device. The results of I-V test indicated that the new material exhibited typical bistable electrical switching and a nonvolatile rewritable memory effect. The theory calculation indicated that the encaged metal may serve as the important electron trapping center. PVK-Gd@C82 is thus an example of a new type charge-transfer complex that integrates the conventional organic and inorganic charge transfer complexes, which provides a potential method to improve the processing, morphological stability, and electrical performance of organic memory devices.

Basicity of Stereoregulating Electron-Donor Compounds in Ziegler–Natta Catalysts: A Study by Infrared Spectroscopy and Chemical Exchange Reactions

The Lewis basicity of typical electron donor compounds used to modify heterogeneous Ziegler–Natta catalysts, such as diakyl ethers, silyl ethers, esters, and ketones, was characterized by determining their effects on the IR frequency of surface silanol groups of silica gel, which correlate with the heat of this specific interaction and with their “donicity”, i.e., with the heat of formation of their complexes with SbCl5. In this manner, ethers and silyl ethers are found to be more basic than ketones and esters. These differences in basicity are likely to affect the stereoregulating properties of such electron donor compounds in Ziegler–Natta polymerization catalysis. By consecutively adsorbing electron donors with various strengths on a MgCl2 support, it was shown that weakly basic donors, such as ethyl benzoate or dibutyl phthalate, are partially displaced by donors with higher basicity, such as valerophenone and propyltrimethoxysilane. This indicates that the displacement of inner donors of the ester type from a titanium–magnesium catalyst upon addition of typical external donors, such as silyl ethers, is controlled by the relative basicities of these donor molecules.

Novel twisted intramolecular charge transfer (TICT) extended fluorescent styryl derivatives containing quinoline electron releasing moiety.

Novel extended fluorescent styryl derivatives were synthesized from (E)-3-(2-cyclopropyl-4-(4-fluorophenyl)quinolin-3-yl)acrylaldehyde containing quinoline ring with 4-fluorophenyl ring at the 4-position as an electron donor and different active methylene compounds as electron acceptors by conventional Knoevenagel condensation reaction. The UV-Visible absorption and fluorescence emission spectra of the dyes were studied in solvents of differing polarity and the compounds showed polarity sensitive emission properties. The dyes were characterized by the spectral analysis. Thermogravimetric analysis showed these dyes are thermally stable up to 250°C. Density Functional Theory computations have been used to derive more understanding of structural, molecular, electronic and photophysical parameters of the push-pull dyes. The computed absorption wavelength values are found to be in good agreement with the experimental results. The second order hyperpolarizability (β o) values were computed by Density Functional Theory and found to be in the range of 116.61 × 10(-31) to 898.48 × 10(-31) e.s.u.

Adducts of Trimeric Perfluro-o-Phenylene Mercury with TTF or DTT

Since the discovery of metallic conductivity in the TTF-TCNQ complex, the charge transfer (CT) complex materials have been studied for such properties as semiconductivity or superconductivity. The synthesis of new CT materials using trimeric perfluoro-ortho-phenylene mercury (Hg3) as electron acceptor compound was done first by Haneline and Gabaï [1]. A series of studies of CT materials containing Hg3 and tetrathiafulvalene (TTF) or dithieno thiophene (DTT) as an electron donor compounds was carried out by different methods. Co-crystalzation with TTF gave a larger variety of co-crystals than with DTT, producing three polymorphs and one pseudo-polymorph. One pot crystal growth of TTF and Hg3 in a 1:1 mixture of solvents dichloromethane (DCM) and dichloroethane (DCA) has led to the formation of TTF polymorphs 1 and 2 with same 1:1 donor acceptor ratio [Hg3·TTF] as well a pseudopolymorph [Hg3·TTF·DCA] 3 that contains the solvent DCA in the asymmetric unit. Slow evaporation in a 1:1 mixture of dichloromethane and carbon disulfide was used to obtain the previously reported CT [(Hg3)2·TTF] (4)1. By slow evaporation as well in pure dichloromethane was obtained the CT material [Hg3·DTT·DCM] 5. All these five CT co-crystals contain mixed donor acceptor stacks, however only in 3, 4 and 5 these stacks are parallel to each other. In the packing of 1 and 2 these stacks are in herringbone arrangement. Polymorphs 1 and 2 differ in crystal shape and color. Contacts Hg···S shorter than the sum of the Van Der Walls radii were observed in the five CTs materials reported, however only 1, 2, 3, and 5 have extended short donor acceptor molecular associates. Moreover only 3, and 5 has these extended donor acceptor associates along one direction.

Synthesis of a novel diether–ester conjugated model compound for electron donors of the polypropylene catalysts

Abstract A novel diether–ester conjugated electron donor model compound, 1,3-dimethoxypropan-2-yl benzoate, was synthesized via a reaction of 1,3-dimethoxypropan-2-ol and benzoyl chloride in the presence of triethyl amine and 4-dimethylaminopryidine. Compared to the known routes of preparing diethers, which usually employ the reactions to O -alkylate the corresponding diols with O -alkylating reagents, the presented method here provides a new way to prepare the diether electron donor compounds. It avoids employing the traditional O -alkylation reactions, so that highly toxic O -alkylating chemicals, such as iodomethane, and very strong basic deprotonating reagents, such as alkoxides or metal hydrides, are not required. The product can be obtained in high yields without complicated purification processes. Catalyst component containing the electron donor compound was prepared and used to catalyze propylene polymerization.