Sodium Dithionite Research Articles

Preparation and characterization of amino modified eucalyptus biochar

Amino modified eucalyptus biochar (ABC) was prepared from eucalyptus biochar by amino amendment with ammonia, concentrated nitric acid, concentrated sulfuric acid and sodium dithionite. The preparation parameters of ABC were optimized by orthogonal experiment. It was found that the optimal preparation process of ABC was: carbonization temperature was 300°C, volume ratio of nitric acid to sulfuric acid was 2:1 and the consumption of ammonia water was 15 ml. The results of characterization indicated that the morphological structure of ABC changed, and the amino functional group was successfully loaded on the surface of the biochar.

Benzo[d]imidazol-5-yl)-5-(substituted)-1,3,4-Oxadiazoles: Synthesis, Anticancer, Antimicrobial and In Silico Studies

Background:Cancer is a fatal disease for mankind; continuous research is still going on for the invention of potent anticancer drugs. In this view, 1, 3, 4-Oxadiazoles are privileged molecules which attracted medicinal chemists towards their anticancer properties.Methods:A new series of benzo[d]imidazol-5-yl)-5-(substituted)-1,3,4-oxadiazole derivatives was synthesized in an efficient ‘one-pot’ nitro reductive cyclization using sodium dithionite as a cyclizing agent by a conventional method with good yield. All the structures of the synthesized molecules were characterized by IR, 1H NMR, HRMS and Mass spectral analysis. Anticancer activity screening against A375 melanoma cancer cell line and MDA-MB-231 breast cancer cell line along with antimicrobial activity were carried out using agar well diffusion method.Results:Compounds 8a and 8j of the series emerged as potent anticancer agents against A375 melanoma cancer cell line with IC50 47.06 µM and 36.76 µM, respectively. In silico studies also revealed that compounds 8a and 8j showed highest interaction with 2OH4 protein of VEGFR-2 tyrosine kinase. Substantial antibacterial and antifungal activities against the tested microorganism were observed for compounds 8j and 8g.Conclusion:Potent anticancer property has been observed with 1,3,4-Oxadiazole linked tetrafluro substituted benzene ring 8j indicating that future research on these type of molecules can be continued to improve the anticancer activity.

2-(3,4-Dimethoxyphenyl)-N-(4-methoxyphenyl)-1-propyl-1H-benzo[d]imidazole-5-carboxamide

2-(3,4-Dimethoxyphenyl)-N-(4-methoxyphenyl)-1-propyl-1H-benzo[d]imidazole-5-carboxamide was synthesized by the ‘one-pot’ reductive cyclization of N-(4-methoxyphenyl)-3-nitro-4-(propylamino)benzamide with 3,4-dimethoxybenzaldehyde, using sodium dithionite as a reductive cyclizing agent using DMSO as a solvent. The structure of newly synthesized compound was elucidated based on IR, 1H-NMR, 13C-NMR, and LC-MS data.

The conversion of azo-quenchers to fluorophores

In this short note we describe the conversion of the widely used fluorescence quenching azo-dyes DABCYL and HABA to fluorophores. The dyes were conjugated to the proteins RNase and human serum albumin (HSA) and subsequently reduced using sodium dithionite (Na2S2O4), thus forming amine-containing fluorophores. Since this chemical reaction can be applied to any azo-containing quencher compound, a great variety of substances can be readily obtained synthetically. This approach provides a promising tool in the use of fluorescence-based investigations of biomolecular interactions.

Fiber structures and properties of eucalyptus kraft pulp via different bleaching methods

Abstract The fiber morphology, the content of hydrogen bonds (HBs) of different models, cellulose crystalline structure, water retention value (WRV), and strength properties of eucalyptus pulp bleached by different bleaching methods (hydrogen peroxide bleaching and sodium dithionite bleaching) were investigated. The results of fourier transform infrared spectrometer (FTIR) showed that the content of intramolecular hydrogen bonds (HBintra) increased by 11.6 % and 4.8 % after hydrogen peroxide bleaching and sodium dithionite bleaching, respectively. The energy of the hydrogen bonds was changed after bleaching treatment. The hydrogen bonding distances showed a small change after different bleaching treatment. The results of X-ray diffraction (XRD) demonstrated a decrease in the average width of crystallite size in the (002) lattice plane after different bleaching treatment, which was the same trend with the variability of cellulose crystallinity. Compared with the unbleached pulp, the WRV and strength properties of the bleached pulp increased after each bleaching process. Tear index of handsheets made from the hydrogen peroxide and sodium dithionite bleaching pulps were 46.0 % and 54.8 %, respectively. The sodium dithionite bleaching treatment had more significant effects on fiber swelling capability.

Recovery of metals by ion exchange process using chelating resin and sodium dithionite

Chelating ion exchange resins can be used to recover metals from nickel laterite leach solution. The main problem is the high presence of iron. In pH above 2.00, iron precipitates and there is co-precipitation of copper and cobalt, which decreases recovery process efficiency. To solve this problem, a conversion of Fe(III) to Fe(II) can be the solution, where Fe(II) will precipitate just at pH 5.00. This reducing process can also increase metals recovery, where ferrous iron occupies less active sites on the resin than ferric iron. However, studies do not evaluate what happens to the resin under this situation. This work aimed to study the copper, nickel and cobalt recovery using chelating ion exchange resin Lewatit TP 207 and reducing process using sodium dithionite 1 mol.L−1. Sodium dithionite was used to convert Fe(III) to Fe(II). The effect of reducing agent on the resin was studied. Three different solutions where prepared to simulate the real nickel laterite leach solution. Batch experiments were performed to study the effect of pH to recover metals and to compare the results with and without the reducing agent. Results showed that metals adsorption increased when the ferric iron was converted to ferrous iron by reducing process. Chelating resin adsorbed more copper and also was selective for this metal at pH 2.50. Nickel and cobalt adsorption were higher at pH 3.50, but the resin was not selective for these metals under this pH. The order of selectivity of chelating resin changed when pH increased.

Effect of sodium hydrosulphite treatment on the quality of non-centrifugal sugar: Jaggery

Jaggery is a non-centrifugal sweetener produced by thermo-chemical treatments of sugarcane juice. The traditional practices involved in making jaggery are usually tailored using chemicals to meet consumer requirements. Sodium hydrosulphite (hydros) is a commonly employed chemical in the jaggery industry to improve its colour. This article presents a comparative study of jaggery made with and without hydros treatments. The differences in properties, such as sorption behaviour, colour, polyphenols, flavonoids, minerals, and sulphur dioxide content, were measured. Hydros-treated jaggery was found to be brighter in colour with a lower browning index by 5–10. SO2 content of hydros-treated jaggery was >70 ppm, while minerals, polyphenols, and flavonoids were less abundant compared to control jaggery, thereby compromising overall quality. Based on the experiments carried out, the optimum treatment of hydros can be employed to satisfy consumer demand while producing an acceptable quality of jaggery that conforms to norms.

The l-Thr Kinase/l-Thr-Phosphate Decarboxylase (CobD) Enzyme from Methanosarcina mazei Gö1 Contains Metallocenters Needed for Optimal Activity.

The MM2060 (cobD) gene from Methanosarcina mazei strain Gö1 encodes a protein (MmCobD) with l-threonine kinase (PduX) and l-threonine-O-3-phosphate decarboxylase (CobD) activities. In addition to the unexpected l-Thr kinase activity, MmCobD has an extended carboxy-terminal (C-terminal) region annotated as a putative metal-binding zinc finger-like domain. Here, we demonstrate that the C-terminus of MmCobD is a ferroprotein containing ∼25 non-heme iron atoms per monomer of protein. The absence of the C-terminus substantially reduces, but does not abolish, enzymatic activities in vitro and in vivo. Single-residue substitutions of C-terminal putative Fe-binding cysteinyl and histidinyl residues resulted in the loss of Fe and changes in enzyme activity levels. Salmonella enterica ΔpduX and ΔcobD strains were used as heterologous hosts to assess coenzyme B12 biosynthesis as a function of 17 MmCobD variants tested. Some of the latter displayed 5-fold higher enzymatic activity in vitro and enhanced the growth rate of the S. enterica strains that synthesized them. Most of the MmCobD variants tested were up to 6-fold less active in vitro and supported slow growth rates of the S. enterica strains that synthesized them; some substitutions abolished enzyme activity. MmCobD exhibited an ultraviolet-visible absorption spectrum consistent with [4Fe-4S] clusters that appeared to be susceptible to oxidation by H2O2 and reduction by sodium dithionite. The presence of FeS clusters in MmCobD was corroborated by electron paramagnetic resonance and magnetic circular dichroism studies. Collectively, our results suggest that MmCobD contains one or more diamagnetic [4Fe-4S]2+ center(s) that may play a structural or regulatory role.

Improvement of photobiological hydrogen production in Chlorococcum minutum using various oxygen scavengers

The depletion of non-renewable energy resources such as fossil fuels urge the human society to concentrate more on renewable energy including production of biological hydrogen (H2) from algae. Biological hydrogen or biohydrogen is one of the cleanest and efficient alternate energy sources for human needs. It is a well-known fact that hydrogenase (H2ase) will work in anoxic condition which is the key enzyme in H2 generation from photosynthetic algae or advanced plants. Keeping in view the significance of anoxic condition, the present study deals with screening of three oxygen scavengers/removers such as sodium sulfite (Na2SO3), sodium metabisulfite (Na2S2O5) and sodium dithionite (Na2S2O4) individually along with universal tris-acetate-phosphate (TAP) medium for improvement of biohydrogen production in green alga Chlorococcum minutum (C. minutum) under in vitro conditions. To the best of our knowledge, for the first time improvement in hydrogen production was achieved using sodium sulfite and sodium metabisulfite individually with algal cultures. Efficient photobiological H2 production was observed at 24 h in C. minutum in the presence of all the three oxygen scavengers when compared to untreated samples via limiting the oxygen levels but output was more with sodium sulfite treatment. Particularly 0.8 mM Na2SO3 is best for enhancement of H2 production at 24 h when compared to other two scavengers and this may be due to high oxidation state and more electron negativity of this compound. Apart from augmentation in H2 production in this species, present screening may also be helpful for researchers working in the area of biological H2 generation.

Characterization of kraft pulp delignification using sodium dithionite as bleaching agent

The delignification of kraft pulp with sodium dithionite was studied to remove lignin content in the pulp. The sodium dithionite dissolves the chromophoric groups and residual lignin present in the pulp. The increase in dosage of sodium dithionite and reaction temperature of delignification has positive effect on kappa reduction of pulp. X ray diffraction was used to determine the crystallinity index of bleached pulp. The crystallinity increased from 83.3% for unbleached pulp to 86.7% after delignification. Fourier transform infrared spectroscopy shows the reduction in hydrogen bonding in bleached pulp and also the conversion of cellulose I to cellulose II. FT-Raman spectra shows that the fluorescence observed in the spectra of unbleached pulp reduced significantly in comparison to the spectra of bleached pulp resulting in removal of residual lignin and chromophoric groups present in the pulp. Scanning electron imaging shows the smoothening of fiber surface after bleaching. The delignification reaction followed first-order kinetics and activation energy is 33.57kJ/mol.

Gated Mesoporous Silica Nanocarriers for Hypoxia-Responsive Cargo Release.

Mesoporous silica nanocarriers (MSNs) are appealing in terms of their large cavity surface area and high loading capacity, but they have been suffering from premature cargo release. Herein, we report a gated smart MSN that is sensitive to low oxygen concentration (i.e., hypoxia) via taking advantage of the superior electron-accepting ability of the azobenzene moiety. The azobenzene polymer was employed as the responsive gate-keeper that was deposited on the MSN surface, followed by coating with amphiphilic Pluronic F68 for steric stabilization. The obtained nanocarriers were less than 200 nm. The in vitro polymer degradation was spectrophotometrically witnessed via the employment of a reducing agent, namely, sodium dithionite, with astrong electron-donating ability. The hypoxia-responsive cargo release from the gated MSN was quantitatively demonstrated in breast cancer cells (MCF-7) using the fluorescence resonance energy transfer (FRET) technique where coumarin 6 and rhodamine B was selected as the FRET donor and acceptor, respectively. The FRET ratio was used as the index and decreased linearly over time under hypoxia, whereas it almost remained steady under normoxia. In addition, a model photosensitizer, namely, chlorin e6, was also loaded in the gated MSN whose toxicity under hypoxia was verified. This study developed a hypoxia-responsive MSN with the azobenzene polymer as the removable gate-keeper, which would expand the application of MSNs in pharmaceutical and biomedical areas since thelow oxygen concentration is a unique trigger in many pathological conditions.

Comparison of hypoxic effects induced by chemical and physical hypoxia on cardiomyocytes

The degree and duration of chemical hypoxia induced by sodium dithionite (Na2S2O4) have not been reported. It is not yet clear how much reduction in the O2 concentration (physical hypoxia) can lead to hypoxia in cultured cardiomyocytes. In this study, oxygen microelectrodes were used to measure changes in the O2 concentration in media containing different concentrations of Na2S2O4. Then, hypoxic effects of 0.8, 1.0, and 2.0 mM Na2S2O4 or 1%, 3%, and 5% O2 in cultured cardiomyocytes from neonatal rats were observed and compared. The results showed that the O2 concentration failed to remain constant by Na2S2O4 treatment during the 180-minute observation period. Only the 2.0 mM Na2S2O4 group significantly increased the expression of hypoxia-inducible factor 1α (HIF-1α) and hypoxic responses. Notably, 3% O2 only significantly increased the expression of HIF-1α in cardiomyocytes, while 1% O2 not only increased the expression of HIF-1α but also increased the apoptotic rate in cardiomyocytes. These results suggest that Na2S2O4 is not suitable for establishing a hypoxic model in cultured neonatal rat cardiomyocytes, and neonatal rat cardiomyocytes cultured at or below 1% O2 induced significant hypoxic effects, which can be used as a starting O2 concentration for establishing a hypoxic cell model.

Reduction and pH dual‐responsive block copolymers containing pendent p‐nitrobenzyl carbamate functionalities: Synthesis and self‐assembly behavior

ABSTRACTWe report on the preparation of reduction‐responsive amphiphilic block copolymers containing pendent p‐nitrobenzyl carbamate (pNBC)‐caged primary amine moieties by reversible addition–fragmentation chain transfer (RAFT) radical polymerization using a poly(ethylene glycol)‐based macro‐RAFT agent. The block copolymers self‐assembled to form micelles or vesicles in water, depending on the length of hydrophobic block. Triggered by a chemical reductant, sodium dithionite, the pNBC moieties decomposed through a cascade 1,6‐elimination and decarboxylation reactions to liberate primary amine groups of the linkages, resulting in the disruption of the assemblies. The reduction sensitivity of assemblies was affected by the length of hydrophobic block and the structure of amino acid‐derived linkers. Using hydrophobic dye Nile red (NR) as a model drug, the polymeric assemblies were used as nanocarriers to evaluate the potential for drug delivery. The NR‐loaded nanoparticles demonstrated a reduction‐triggered release profile. Moreover, the liberation of amine groups converted the reduction‐responsive polymer into a pH‐sensitive polymer with which an accelerated release of NR was observed by simultaneous application of reduction and pH triggers. It is expected that these reduction‐responsive block copolymers can offer a new platform for intracellular drug delivery. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1333–1343

Remoção de óxidos de ferro de uma fonte ornamental quinhentista pertencente à Quinta da Cardiga (Torres Novas, Portugal)

The ornamental fountain in marble and breccia is a 16th century Italian work integrated in the small courtyard of the Cardiga Palace (Torres Novas, Portugal) currently in restauration process. The iron spikes used to connect the constituent elements were corroded and contaminating the base stone elements surfaces with intense stains of metallic oxides. There was a suspicion that, apart the surface, these oxides could have migrated in depth through the porous structure of the material. The performance of the iron oxides removal tests was evaluated using optical measurements in the CIELAB color space after each chelant application. Sodium dithionite was found to exert a substantially higher cleaning action than ammonium citrate. After finishing the treatment with the most efficient chelant, the chelating action was verified below the surface of the marble. It was found that at the depth of 1 mm the material remained contaminated with iron oxides, with an evident color contrast with a treated surface.

Double Drug Delivery Using Capped Mesoporous Silica Microparticles for the Effective Treatment of Inflammatory Bowel Disease.

Silica mesoporous microparticles loaded with both rhodamine B fluorophore (S1) or hydrocortisone (S2), and capped with an olsalazine derivative, are prepared and fully characterized. Suspensions of S1 and S2 in water at an acidic and a neutral pH show negligible dye/drug release, yet a notable delivery took place when the reducing agent sodium dithionite is added because of hydrolysis of an azo bond in the capping ensemble. Additionally, olsalazine fragmentation induced 5-aminosalicylic acid (5-ASA) release. In vitro digestion models show that S1 and S2 solids are suitable systems to specifically release a pharmaceutical agent in the colon. In vivo pharmacokinetic studies in rats show a preferential rhodamine B release from S1 in the colon. Moreover, a model of ulcerative colitis is induced in rats by oral administration of 2,4,6-trinitrobenzenesulfonic acid (TNBS) solutions, which was also used to prove the efficacy of S2 for colitis treatment. The specific delivery of hydrocortisone and 5-ASA from S2 material to the colon tissue in injured rats markedly lowers the colon/body weight ratio and the clinical activity score. Histological studies showed a remarkable reduction in inflammation, as well as an intensive regeneration of the affected tissues.

A study on using modified Corchorus capsularis powder to remove macrolide group from water

AbstractThis study grafted monomer acrylamide onto cellulose (from Corchorus capsularis powder) using trigger system including sodium hydrosulfite (SB) and ammonium peroxodisulfate (APS) to remove the macrolide group (Spiramycin ‐ SPI, Erythromycin ‐ ERY, Tylosin ‐ TYL) from water. Corchorus capsularis powder was pre‐treated by sodium hydroxide 15 % (COC), then modified by a mixture of sodium bisulfite (SB) 0.15 mol/L and ammonium peroxydisulfate (APS) 0.2 mol/L. The material was grafted with monoacrylamide (AM) at ratio AM/COC = 1/1 in 2.5 hours at 60°C. The adsorbent was characterized by FTIR and SEM. After modification with AM, the adsorbent (BTA) was used to adsorb SPI, ERY, and TYL from water. Effects of pH, temperature and adsorbent dose to adsorption performance were studied. Concentration of macrolides were determined by LC/MS‐MS. Maximum adsorption capacities of SPI, ERY, TYL following Langmuir isotherm model were 50.00, 33.33, 25.00 mg/g, respectively. The adsorption constant Kp of SPI, ERY, and TYL following the Freundlich isotherm model were 5383.53, 1082.79 and 1004.76, respectively. The n constant ranged from 1 to 10. The Optimal adsorption condition of SPI, ERY, and TYL to BTA material were fixed at 30°C, pH 7.

Making conductive graphene yarn in bulk

A fast and easy method to produce conductive graphene yarn in bulk could open the door to mass production of wearable textile electronics (ACS Nano 2019, DOI: 10.1021/acsnano.9b00319). Nazmul Karim and Kostya S. Novoselov of the University of Manchester and colleagues made the flexible, washable yarn using an industrial dyeing process capable of producing 1,000 kg of the yarn in about half an hour, they say. The key is a new graphene-based dye. To make it, the researchers first dispersed graphene oxide flakes in water, then used ascorbic acid and sodium hydrosulfite to partially reduce the flakes to graphene. Next, they added polymers to the solution to prevent the flakes from clumping. They dyed a hank of cotton yarn with this solution using a lab-scale replica of a commercial yarn-dyeing machine. The partially reduced graphene oxide flakes retain some oxygen-containing functional groups that bond with the cellulose in the cotton,

Синтез мономеров для получения оптически активных полиамидоимидов. Часть 2. Синтез хиральных аминокарбоновых кислот, содержащих имидный цикл и фрагмент природной аминокислоты

In a previous work, it was shown that the imidization reaction of dystereomerically pure nitrophenylcycloalkanedicarboxylic acids with natural amino acids in acetic acid proceeds with partial racemization of the α-carbon center of the amino acid fragment. Carrying out the synthesis in DMF at room temperature allows to obtain imides with preservation of the configuration of all chiral centers. New aminocarboxylic acids were synthesized based on them, which are the starting compounds for the monomers of optically active PAI. We used various reduction systems to produce aromatic amine compounds containing an imide cycle, such as tin or tin(II) chloride and hydrochloric acid, sodium dithionite in water and catalytic reduction with hydrogen in acetone or ethyl alcohol at various pressures and temperatures. The complete reduction of the nitroacid occurs only when using palladium on coal at a temperature of 100 °C and a hydrogen pressure of 40 atm or Raney nickel at 70 °C and a pressure of 65 atm H2 in ethanol. Raney nickel is very sensitive to catalytic poisons, even a small amount of impurities (such as alkali) left after the catalyst has been obtained and washed leads to its complete deactivation. Therefore, synthesis using Raney nickel, although possible, is inconvenient from a practical point of view. On the contrary, the complete reduction of the nitro group occurs at lower temperatures and pressures (50 °C, 25 atm) using palladium on coal as a catalyst after its additional activation with hydrogen. The structure of aminocarboxylic acids was confirmed by IR spectroscopy, 1H NMR spectra, elemental analysis and HPLC.

Color stripping of reactive-dyed cotton fabric in a UV/sodium hydrosulfite system with a dipping manner at low temperature

Color stripping is one of the most convenient approaches for amending various shade faults during dyeing and printing processes. However, conventional stripping processes usually bring a serious risk of environment pollution. The purpose of this work is to develop a novel, sustainable and energy-conserving method for stripping of reactive-dyed cotton substrate by employing a UV/Na2S2O4 system, in which low dosage of sodium hydrosulfite (Na2S2O4) was involved and induced by UV photocatalysis at atmospheric temperature. The effects of stripping parameters such as initial pH value of working solution, temperature and stripping duration on color stripping efficiency and fabric tensile strength were investigated. The results show that the fixed reactive dyes on cotton could be efficiently stripped in the UV/Na2S2O4 system with a photocatalytic initiation and a dipped stripping manner, along with relatively high tensile strength retention by the substrate. Moreover, an optimized photocatalytic color stripping process was recommended for degradation or stripping of the fixed reactive dye molecules in cotton fibers. Furthermore, a successful application of the proposed system was also achieved for stripping a series of the Evercion/Everlight and Megafix reactive dyes fixed on cotton. In addition, the color stripping was further successfully investigated and validated via the variations in structures and surface morphologies of the cotton fibers by utilizing Fourier transform infrared spectrometry, wide-angle X-ray diffraction and scanning electron microscopy analysis.

Flow Cytometry Study of the Non-Fickean Diffusion of Small-Charged Molecules in Poly(diallyl dimethyl ammonium chloride)/Poly(styrene sodium sulfonate) Multilayers: Impact of the Layer Number, Top Layer, and Concentration of Diffusing Molecules.

The diffusion of sodium dithionite (S2O42-) through polyelectrolyte multilayers of poly(diallyl dimethyl ammonium chloride) (PDADMAC)/poly(styrene sodium sulfonate) (PSS) assembled on colloidal particles with the layer-by-layer technique is studied by means of flow cytometry and quenching assay. Fluorescence is provided by a layer of (7-nitrobenz-2-oxa-1,3-diazol-4yl) amino) hexanoate (NBD)-labeled poly(allyl amine hydrochloride) assembled below the PDADMAC/PSS multilayer. NBD is quenched by a redox reaction with S2O42-. NBD quenching is fast at short times but strongly retarded at longer times. Quenching is faster for PDADMAC as the top layer and for increasing concentrations of S2O42-. The quenching kinetics of NBD is described with a model assuming a non-Fickean diffusion of S2O42-, with diffusion coefficients that depend on time with an inverse power law. Diffusion coefficients show little dependence on the number of layers but are highly dependent on the concentration of S2O42-. Increasing the concentration of S2O42- over 10 mol/m3 results in a decrease of the diffusion coefficient, more evident at longer times. The non-Fickean behavior for S2O42- diffusion is explained on the basis of the trapping of dithionites in the multilayers.