Step Reaction Research Articles

In Situ Fabrication of Nanoceria with Oxidase-like Activity at Neutral pH: Mechanism and Boosted Bio-Nanozyme Cascades

Catalytic cascades have drawn much attention by avoiding the isolation of intermediates and due to high atom economy. Yet, developing an efficient, one-pot biocatalytic cascade remains challenging. Combined with the selectivity of biological enzymes and tunable activity of nanozymes, we herein demonstrate an effective bio-nanozyme cascade formed by glucose oxidase (GOx) and in situ-generated nanoceria. The prepared H2O2-nanoceria complex shows strong oxidative activity for common chromogenic substrates under physiological conditions, which are the optimal reaction conditions for most biological enzymes. Interestingly, GOx not only provides H2O2 for the second step reaction but also simultaneously leads to 7.4-fold enhancement of activity. We characterized the process of in situ generation of nanoceria at pH 7.0 and how proteins boost the activity by enhancing product desorption. In addition, the proposed one-pot bio-nanozyme cascade shows high stability and analytical performance for serum glucose with a detection limit of 5 μM.

Synthesis and Characterization of Heterocyclic Compounds Derived from Schiff base Glycerol Triester

Heterocyclic compounds were prepared from Schiff bases triester derivatives, the first step was included, p- aminobenzoic acids convert to p-amino benzoyl chloride in the presence of thionyl chloride then glycerol was added to form triesters compound A. second step reaction of triester product with the 4-nitrobenzaldehyde, and 3-amino benzaldehyde to produce M1, and M2. The third step. Involve reacted Schiff bases triester derivatives to give heterocyclic compounds M1S, M1A, M2P, and M2K. The structure of all compounds is monitored by (TLC), and identified by many techniques 1HNMR, FT-IR, and melting point.

Coating Characteristic of Hydroxyapatite on Titanium Substrates via Hydrothermal Treatment

Medical pure titanium (Ti) shows excellent chemical stability and mechanical properties in clinical uses, but its initial fixation with host bone, when implanted, is usually delayed owing to the bioinert Ti surface. In this study, we fabricate the hydroxyapatite (HA)-coated titanium by three steps reactions: (1) to form an activated O2− layer by immersing Ti substrate into an alkaline solution such as NaOH; (2) the O2− bonds with Ca2+ to form Ca–O–Ti bonding, in which O plays the part of bridge materials between Ca and Ti substrate and (3) the conversion of Ca–O–Ti samples to HA-coated Ti samples by immersion into Na2HPO4 2 M at 180 °C for 48 h using hydrothermal methods. The effect of different phosphate solutions (NaH2PO4 2 M and Na2HPO4 2 M solution) and hydrothermal treatment time (24 and 48 h) on the characteristic of hydroxyapatite coating titanium substrate is also investigated using the optical microscope, thin film XRD and SEM/EDX. The HA-coated Ti samples fabricated by immersion into Na2HPO4 2 M at 180 °C for 48 h show fiber HA covering Titan substrate with a diameter varying from 0.1 to 0.3 µm. These HA-coated Ti samples can be regarded as promising multifunctional biomaterials.

Synthesis and characterization of organosoluble thermally stable polyamides containing spacer methylene linkage and bulky tetraphenylfuran moiety

Thermally stable and organo-soluble polyamides synthesized by polycondensation reaction of diacid monomer, 2, 5-bis (4-carboxymethylene phenyl) 3, 4-diphenyl furan (BCMPDF) with various commercially available aromatic diamines such as 4,4′-Oxydianiline, 4,4′-methylenedianiline, 4,4'-sulphonyldianiline, 4,4'-Diaminobenzophenone and 4,4'-(hexafluoroisopropylidene)dianiline by using Yamazaki’s direct phosphorylation method. A 2, 5-bis (4-carboxymethylene phenyl) 3, 4-diphenyl furan (BCMPDF) as a new compound containing methylene linkage and bulky moiety of tetraphenylfuran was successfully prepared by a four step reaction. The resulted polymers show excellent thermal stability, good solubility in aprotic polar solvent and inherent viscosities between 0.50 and 0.58 dl/g. Wide angle X-ray diffraction of all these PAs show amorphous nature. Polyamides showed glass-transition temperatures in the range of 169–213 °C indicate that polymers are easily processable. Thermogravimetric analysis of the polyamides indicated a 10% weight loss (T10) in the temperature range of 449–510 °C and char yields at 900 °C under nitrogen atmosphere in the range of 49–58% depending on the diamine monomer used for the synthesis polyamides. The structure -property correlation among these polyamides were discussed. The limiting oxygen indexes of all polyamides are more than 37.1, thus such type polymers of can act as flame retardant materials. These polyamides will be useful for high performance applications.

2-step reaction kinetics for hydrogen absorption into bulk material via dissociative adsorption on the surface

We have demonstrated that the process of hydrogen absorption into a solid experimentally follows a Langmuir-type (hyperbolic) function instead of Sieverts law. This can be explained by independent two theories. One is the well-known solubility theory which is the basis of Sieverts law. It explains that the amount of hydrogen absorption can be expressed as a Langmuir-type (hyperbolic) function of the square root of the hydrogen pressure. We have succeeded in drawing the same conclusion from the other theory. It is a 2-step reaction kinetics (2sRK) model that expresses absorption into the bulk via adsorption on the surface. The 2sRK model has an advantage to the solubility theory: Since it can describe the dynamic process, it can be used to discuss both the amount of hydrogen absorption and the absorption rate. Some phenomena with absorption via adsorption can be understood in a unified manner by the 2sRK model.

Development of purified glycogen derivatives as siRNA nanovectors

Purified Glycogen (PG) is a highly hyper branched carbohydrate, characterized by high water solubility and very moderate increase in viscosity. The dendrimeric structure of PG, appropriately functionalized, makes it an alternative to current synthetic gene delivery agents. The present study explores the preparation of purified glycogen polycationic derivatives (PGPDs), developed and characterized starting from a single step reaction between PG and N,N-dialkylamino alkyl halides. Subsequently PGPDs were used for the complexation of a model siRNA nucleic acid, a transfection reagent siRNA and a fluorescein-labelled dsRNA oligomer. PGPDs-siRNA complexes were fully characterized by agarose gel electrophoresis and their efficacy was assessed by both confocal microscopy and transfection assays on breast and renal cancer cells. Results proved that PGPDs-siRNA complexes were efficient and not cytotoxic, maintaining their spherical and dendrimeric structure and, particularly, were able to effectively transfect the target cells by releasing the siRNA.

Uracil possessing “turn-on” fluorescent sensor for F− and AcO− ions with the simultaneous detection of boric acid in antiseptic eye-wash solution

Fluorescent “turn-on” method was attempted for sensitive and selective recognition of F− and AcO− ions based on uracil possessing sensor, which was synthesized by single step reaction and characterized by using common spectroscopic techniques. The presence of sensed anions in acetonitrile solution of chemosensor 1 caused approximately 60-fold (F−) and 50-fold (AcO−) enhancement in fluorescence intensity at 432 nm. The complexation behaviour of chemosensor 1with detected anions was established by 1H NMR titration studies, which pointed to the binding of the F−/AcO− ion with hydrogen of amine group of uracil to expedite its detection. Computational calculations (TD-DFT) were performed for 1-F−/AcO− to obtain theoretical evidences to the experimental results. Also, the practical applicability of the chemosensor 1 has been successfully examined for detection of boric acid in commercial antiseptic eye-wash solution.

Single‐Molecule Magnetic, Catalytic and Photoluminescence Properties of Heterometallic 3d–4f [Ln{PZn2W10O38(H2O)2}2]11− Tungstophosphate Nanoclusters

AbstractA series of eleven lanthanide containing di‐Zinc (II) substituted heterometallic 3d–4f sandwich‐type tungstophosphate nanoclusters [Ln{PZn2W10O38(H2O)2}2]11− (Ln=NdIII, SmIII, EuIII, GdIII, TbIII, DyIII, HoIII, ErIII, TmIII, YbIII, and LuIII) have been synthesized by a single step reaction procedure. These clusters were characterized by various analytical techniques such as single crystal X‐ray diffraction (SC‐XRD), fourier transform infrared (FT‐IR) spectroscopy, high‐resolution electro‐spray ionization mass spectrometry (HR‐ESI‐MS), inductively coupled plasma atomic emission spectroscopy (ICP‐AES), solid UV/Vis, photoluminescence spectroscopy, powder X‐ray diffraction (P‐XRD) and thermogravimetric analysis (TGA). All the polyanions are isostructural and consists of a lanthanide ion sandwiched between two units of (1,5) isomer of di‐Zn substituted α‐Keggin type tungstophosphate. The complexes Sm‐2 a, Eu‐3 a, Tb‐5 a, and Dy‐6 a show good photoluminescence behavior. The catalytic properties were examined for the oxidation of thioethers. The catalyst is stable with a high turn over frequency (TOF) of 6250 h−1 and can be recovered even after 5 consecutive cycles. Furthermore, magnetic properties revealed that Gd‐4 a, Tb‐5 a, Dy‐6 a, Er‐8 a, and Yb‐10 a show single‐molecule magnetic properties.

Injectable hyaluronic acid hydrogels encapsulating drug nanocrystals for long-term treatment of inflammatory arthritis.

Antiproliferative chemotherapeutic agents offer a potential effective treatment for inflammatory arthritis. However, their clinical application is limited by high systemic toxicity, low joint bioavailability as well as formulation challenges. Here, we report an intra‐articular drug delivery system combining hyaluronic acid hydrogels and drug nanocrystals to achieve localized and sustained delivery of an antiproliferative chemotherapeutic agent camptothecin for long‐term treatment of inflammatory arthritis. We synthesized a biocompatible, in situ‐forming injectable hyaluronic acid hydrogel using a naturally occurring click chemistry: cyanobenzothiazole/cysteine reaction, which is the last step reaction in synthesizing D‐luciferin in fireflies. This hydrogel was used to encapsulate camptothecin nanocrystals (size of 160–560 nm) which released free camptothecin in a sustained manner for 4 weeks. In vivo studies confirmed that the hydrogel remained in the joint over 4 weeks. By using the collagen‐induced arthritis rat model, we demonstrate that the hydrogel‐camptothecin formulation could alleviate arthritis severity as indicated by the joint size and interleukin‐1β level in the harvested joints, as well as from histological and microcomputed tomography evaluation of joints. The hydrogel‐nanocrystal formulation strategy described here offers a potential solution for intra‐articular therapy for inflammatory arthritis.

A DFT Study on the Molecular Mechanism of Additions of Electrophilic and Nucleophilic Carbenes to Non-Enolizable Cycloaliphatic Thioketones.

The molecular mechanisms of addition of dihalocarbenes and dimethoxycarbene to thioketones derived from 2,2,4,4-tetrmethylcyclobutane-1,3-dione were examined on the basis of the DFT wb97xd/6-311g(d,p)(PCM) calculations. Obtained results demonstrated that the examined processes exhibit polar nature and in the case of electrophilic dichloro-, and dibromocarbenes are initiated by the attack of carbene species onto the sulfur atom of the C=S group. Remarkably, reactions involving more electrophilic carbenes (dichloro-, and dibromocarbene) proceeds via stepwise mechanism involving thiocarbonyl ylide as a transient intermediate. In contrast, analogous reactions with nucleophilic dimethoxycarbene occur via a single step reaction, which can be considered as the [2 + 1] cycloaddition reaction initiated by the attack onto the C=S bond. A computational study showed that difluorocarbene tends to react as a nucleophilic species and resembles rather dimethoxycarbene and not typical dihalocarbene species. Significantly higher reactivity of the thioketone unit in comparison to the ketone group, both present in 3-thioxo-2,2,4,4-tetramthylcyclobutanone molecule, was rationalized in the light of DFT computational study.

A novel μ-oxo-diruthenium(III,III)-ibuprofen-(4-aminopyridine) chloride derived from the diruthenium(II,III)-ibuprofen paddlewheel metallodrug shows anticancer properties

Diruthenium(II,III) metal-metal multiply bonded paddlewheel complexes bearing non-steroidal anti-inflammatory drugs are promising anticancer metallodrugs. The [Ru2(Ibp)4Cl] (Ibp, ibuprofenate anion from HIbp ibuprofen drug), free or encapsulated, shows anticancer activity against glioblastoma (in vitro, in vivo), and against human breast and prostate cancer cells. Herein we report the interaction of [Ru2(Ibp)4Cl] and of [Ru2(Ac)4(H2O)2]PF6 (Ac, acetate) with the 4-aminopyridine (4Apy) drug. The N-ligand was capable of cleaving the paddlewheel unit with oxidation of Ru2(II,III) to Ru2(III,III)O μ-oxo core in the ibuprofen complex while the acetate complex underwent axial substitution of water by 4Apy. Carefully designed synthetic and chromatographic methods succeeded in giving the novel [Ru2O(Ibp)2(4Apy)6]Cl2 metallodrug, the first diruthenium(III,III) μ-oxo having chloride as counterion. Characterization was performed by elemental analysis, mass spectrometry, thermogravimetric analysis, electronic absorption and vibrational spectroscopies, molar conductivity and cyclic voltammetry. Kinetic studies for the μ-oxo complex (in 50:50 v/v ethanol:water) suggested an aquation/complexation equilibrium in consecutive step reactions with the exchange of the two 4Apy trans to the μ-oxo bridge by water (aquation) and the back coordination of 4Apy in excess of the N-ligand (complexation). Trypan blue assays for the novel compound showed time- and dose- dependent antiproliferative effects (at 5–50 μmol L−1) and cytotoxicity (> 20 μmol L−1), and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) assays gave IC50 value of 7.6 ± 1.5 μmol L−1 (at 48 h, 1–20 μmol L−1) against U87MG human glioblastoma cells (aggressive brain glioma cancer) pointing the metallodrug as potential candidate for novel therapies in gliomas.

Facile functionalized fluorescein derivative as a reversible fluorescence probe for selective monitor of the redox cycle between hypochlorous acid and cysteine

The reasonable cellular redox equilibrium mediated by reactive oxygen species/reactive nitrogen species and antioxidants are pivotal importance for maintaining a variety of physiological processes, and disrupted redox equilibrium may derange the cellular components and eventually may lead to cell death, irreversible tissue destruction, and various diseases. In this paper, we develop a phenylseleno-functionalized reversible fluorescent probe Fluo-Se for monitoring the hypochlorous acid/cysteine redox couple in living cells. The advantages of the probe included: a) the synthetic procedure of the probe is very simple by one step reaction; b) the probe shows high sensitivity for HOCl and cysteine (the detection limit is 1.1 nM and 3.0 nM, respectively); c) the probe exhibits high reversibility to the hypochlorous acid/cysteine redox couple both in solutions and in the living cell by taking advantage of the Se atom-led excellent reversible conversions between Fluo-Se and its oxidized product. We think that Fluo-Se should be very useful for gauging the cellular redox status mediated by the hypochlorous acid/cysteine couple.

Synthesis of 3-((trifluoromethyl)thio)indoles via trifluoromethylthiolation of 2-alkynyl azidoarenes with AgSCF3

Direct and effective trifluoromethylthiolation of 2-alkynyl azidoarenes with silver(I) trifluoromethanethiolate (AgSCF3) has been developed for the construction of 3-((trifluoromethyl)thio)indoles. The trifluoromethylthiolation protocol is compatible with a broad substrate scope, providing a variety of 3-((trifluoromethyl)thio)indoles in moderate to good yields within one step, open-air, and short reaction time.

Synthesis, Characterization Of Thiazolidin-4-one, Oxazolidin-4-one And Imidazolidin-4-one Derivatives From 6-Amino-1, 3-dimethyluraciland Evaluation Of Their Antioxidant And Antimicrobial Agent

In this study, a new series of 6-amino-1,3-dimethyluracil derivative with 6-(3-substituted N-benzylidene)-1,3-dimethyl pyrimidine-2,4-dione-6-yl derivatives which were synthesized by using one pot synthesis. The reaction of 6-amino-1,3-dimethyluracil and different aromatic aldehyde in ethanol yielded Schiff bases (1-6). In the subsequent step reaction of Schiff bases )1-6) with 2-mercaptoacetic acid, 2-chloroacetic acid and 2-amino acetic acidn in Tetrahydrofuran yielded five membered heterocyclic rings of 6-amino-1,3-dimethyluracil derivative which includes: 2,3-thiazolidin-4-one (7-12), 2,3-oxazolidin-5-one (13-18), 2,3-imidazolidin-4-one (19-24) derivatives. The structures of newly synthesized compounds were confirmed by their physicochemical and spectral means FTIR, 1HNMR and 13CNMR. The synthesized compounds were evaluated in vitro for antioxidant and antimicrobial activities against four types of bacteria and four types of fungi

Comparing Tuberculin Anergy Skin Test Reactions and Lymphoblastic Transformation in Medical Student

Background: Tuberculin Skin Test (TST) reaction is an accepted screening test for diagnosing acute and latent Tuberculosis (TB) infection among at-risk populations. It is performed with a standard Protein Purified Derivative (PPD) solution. The skin reaction of PPD is unreliable to distinguish natural infection from the Bacillus Calmette Guerin (BCG) effect. The present survey aimed to determine the prevalence of Tuberculin Anergy (TA) reactions among medical students. Accordingly, we evaluated its sensitivity, specificity, and efficiency by applying the Recall Panel Antigen Test (RPAT) and the Lymphoblastic Transformation Test (LTT). Methods: The participants were sequentially enrolled in this study according to the designed protocol. The current study was conducted on healthy medical students before registering for the hospital training course. All research subjects were healthy, having a cicatrix of Bacillus Calmette Guerin (BCG) vaccination on the arm, and at a young age (20-24 years). Results: In total, 180 medical students met the inclusion criteria of the study. The study subjects’ Mean±SD age was 22±3.07 years (male=89, female=91). Moreover, 75 (42%) subjects presented a TA reaction in the first step of TST screening. Furthermore, 13 (64%) individuals presented a negative result of the RPAT. The sensitivity and specificity of the TST reactions, compared with the LTT were 100% and 94.4 %, respectively. Conclusion: Significant TA reactions were found among medical students with positive cicatrix post-vaccinated. The obtained data suggested that the BCG protection for individuals may be decreased as time expired. Consequently, the medical students will especially be at high risk for TB infection during the clinical training course. The collected data highlighted the patient-safety from the viewpoint of forensic medicine.

Kinetics study on reactive extraction of formic acid using tri-n-octyl amine diluted in n-butyl acetate

Abstract Formic acid is the simplest yet commercially valuable organic acid. It is widely used as a stabilizer and sterile agent in food industries. Reactive extraction is highly effective and selective technique for the recovery of formic acid from dilute solutions. Kinetics study provide rate controlling step (reaction rate or diffusion) that is required to visualize the intrinsic reactive extraction mechanism. Kinetics study of formic acid (0.1–0.4 kmol/m3) extraction with tri-n-octyl amine (TOA) (0.11–0.67 kmol/m3) in n-butyl acetate (NBA) was investigated at temperature 308 ± 1 K. Kinetics study was carried out in a Lewis cell. Effect of formic acid concentration, TOA concentration, speed of stirring, and phase volume ratio were investigated to find the reaction regime. Diffusivity coefficient (DA) of formic acid in NBA was found 3.20 × 10−7 m2/s. Reaction rate constant was evaluated to be 0.616 m3/mol s. The physical mass transfer coefficient (kL) was evaluated to be 0.8278 × 10−6 × N 3.387. The reaction was independent on hydrodynamic parameters and falls under fast reaction regime. The reaction was found first order with respect to both formic acid as well as TOA, occurring in the diffusion film. The findings of the present work are helpful in the selection of commercially viable extraction system and in the design of extractors.

Synthetic approach of ternary magnesium niobate (Mg\u2013Nb\u2013O) compounds

Magnesium based niobium oxides (Mg–Nb–O) were prepared by solid-state reactions owing to understand the function of transition metal oxides as promoters/catalysts for practical application. Magnesium niobate (Mg3Nb6O11) was synthesized for the first time in nearly pure form reported in this context. MgNb2O6 and Mg4Nb2O9 were prepared in oxidizing conditions; on the contrary, Mg3Nb6O11 preferred reducing environment. Stoichiometric mixtures of the precursor materials MgO, Nb2O5 and/or metallic Nb were annealed for the syntheses which revealed the effect of temperature on phase formation, reaction kinetics and heat of reaction. The products were examined by ex-situ, in-situ X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Crystallographic parameters of various binary and ternary compounds (Mg/Nb/O) formed in different calcination conditions, were extracted by Rietveld method. In-situ experiment results in single step reaction for the MgNb2O6 synthesis and the heat of formation of the solid-state reaction obtained to be minimum (93 kJ/mol). In contrast, the formation of Mg4Nb2O9 and Mg3Nb6O11 compounds towards pure phases rather complicated due to multistep reactions and corresponding heat of formation were estimated to be 140 and 190 kJ/mol. Experimental results have been discussed based on kinetic and thermodynamic constrains.

A One‐Pot Synthesis of “K(hfa) glyme” Adducts: Effect of the Polyether Length on the Ion Coordination Sphere

AbstractPotassium complexes are starting to gather more and more interest from academia and industry because of their intriguing application possibilities. Novel adducts of potassium hexafluoroacetylacetonato [K(hfa)] with polyethers (monoglyme, diglyme, triglyme, and tetraglyme) were synthesized through a single step reaction and characterized through FT‐IR spectroscopy as well as 1H and 13C NMR spectroscopy. Single crystal X‐ray diffraction studies enabled the identification of fascinating K coordination polymeric networks.

Chemoenzymatic Cascades toward Methylated Tetrahydroprotoberberine and Protoberberine Alkaloids.

Tetrahydroprotoberberine and protoberberine alkaloids are a group of biologically active natural products with complex molecular scaffolds. Isolation from plants is challenging and stereoselective synthetic routes, particularly of methylated compounds are limited, reducing the potential use of these compounds. In this work, we describe chemoenzymatic cascades toward various 13-methyl-tetrahydroprotoberberbine scaffolds using a stereoselective Pictet-Spenglerase, regioselective catechol O-methyltransferases and selective chemical Pictet-Spengler reactions. All reactions could be performed sequentially, without the workup or purification of any synthetic intermediates. Moreover, the naturally occurring alkaloids have the (+)-configuration and importantly here, a strategy to the (-)-isomers was developed. A methyl group at C-8 was also introduced with some stereocontrol, influenced by the stereochemistry at C-13. Furthermore, a single step reaction was found to convert tetrahydroprotoberberine alkaloids into the analogous protoberberine scaffold, avoiding the use of harsh oxidizing conditions or a selective oxidase. This work provides facile, selective routes toward novel analogues of bioactive alkaloids.

Evaporation and combustion of n-heptane droplets in supersonic combustor

The purpose of the present study is to investigate the combustion of the n-heptane droplet cloud in the supersonic combustor. The finite volume solver is developed to simulate the two-phase reacting compressible flow using single step reaction mechanism as finite rate chemistry. The focus is on the impacts of droplet size and cloud density on the performance of the scramjet. For the considered physical situation, the upper limit of the droplet size is determined to have higher combustion efficiency, and it is shown that the combustion mode is kinetic-controlled for small sizes and is evaporation-controlled for large droplet sizes. The variation of combustor’s exit total pressure and temperature is also investigated for different droplet cloud densities, demonstrating their apparent opposite behavior that must be considered to get optimum propulsion efficiency. In addition, it is illustrated that thermal choking is another criterion which should be avoided by controlling the fuel mass flow rate for intended flight conditions.