Dicyclohexylcarbodiimide Research Articles

Comparable antibacterial effects and action mechanisms of silver and iron oxide nanoparticles on Escherichia coli and Salmonella typhimurium

The current research reports the antibacterial effects of silver (Ag) and citric acid coated iron oxide (Fe3O4) NPs on Escherichia coli wild type and kanamycin-resistant strains, as well as on Salmonella typhimurium MDC1759. NPs demonstrated significant antibacterial activity against these bacteria, but antibacterial effect of Ag NPs is more pronounced at low concentrations. Ag NPs inhibited 60–90% of S. typhimurium and drug-resistant E. coli. The latter is more sensitive to Fe3O4 NPs than wild type strain: the number of bacterial colonies is decreased ~ 4-fold. To explain possible mechanisms of NPs action, H+-fluxes through the bacterial membrane and the H+-translocating FOF1-ATPase activity of bacterial membrane vesicles were studied. N,N′-Dicyclohexylcarbodiimide (DCCD)-sensitive ATPase activity was increased up to ~ 1.5-fold in the presence of Fe3O4 NPs. ATPase activity was not detected by Ag NPs even in the presence of DCCD, which confirms the bactericidal effect of these NPs. The H+-fluxes were changed by NPs and by addition of DCCD. H2 yield was inhibited by NPs; the inhibition by Ag NPs is stronger than by Fe3O4 NPs. NPs showed antibacterial effect in bacteria studied in concentration-dependent manner by changing in membrane permeability and membrane-bound enzyme activity. The FOF1-ATPase is suggested might be a target for NPs.

Electrogenesis in Plasma Membrane Fraction of Halotolerant Microalga Dunaliella maritima and Effects of N,N′-Dicyclohexylcarbodiimide

The effects of N,N'-dicyclohexylcarbodiimide (DCCD), non-specific inhibitor of various transport systems functioning in biological membranes, on Na+-transporting P-type ATPase of the green halotolerant microalga Dunaliella maritima were studied in the experiments with vesicular plasma membranes isolated from the alga cells. The effects of DCCD on electrogenic/ion transport function of the enzyme and its ATP hydrolase activity were investigated. Electrogenic/ion transport function of the enzyme was recorded as a Na+-dependent generation of electric potential on the vesicle membranes with the help of the potential-sensitive probe oxonol VI. It was found that unlike many other ion-transporting ATPases, the Na+-ATPase of D. maritima is insensitive to DCCD. This agent did not inhibit either ATP hydrolysis catalyzed by this enzyme or its transport activity. At the same time DCCD affected the ability of the vesicle membranes to maintain electric potential generated by the D. maritima Na+-ATPase. The observed effects can be explained based on the assumption that DCCD interacts with the Na+/H+ antiporter in the plasma membrane of D. maritima.

External succinate and potassium ions influence Dcu dependent FOF1-ATPase activity and H+ flux of Escherichia coli at different pHs.

During fermentation Escherichia coli transport succinate mainly via Dcu family carriers. Current paper describes the role of externally added succinate on N'N'-dicyclohexylcarbodiimide (DCCD) sensitive ATPase activity and H+ flux depending on potassium ions. At pH 7.5 in wild type membrane vesicles DCCD-sensitive ATPase activity was the same as in dcuACBD quadruple mutant. In dcuACB it was increased ~ 3.3 fold while in dcuD DCCD-sensitive ATPase activity was absent. The DCCD-sensitive H+ efflux was fully dependent on FOF1 only in dcuACB mutant. This activity depended on potassium ions and only in dcuACBD mutant DCCD-sensitive ATPase activity was stimulated ~ 3 fold. At pH 5.5 DCCD-sensitive ATPase activities were determined in dcuACB or dcuD mutants but not in wild type. Interestingly, addition of potassium ions enhanced DCCD-sensitive ATPase activity in dcuD mutant ~ 3-fold compared to wild type. In dcuD mutant ~ 3-fold higher H+ uptake was registered, compared to wild type. Taken together it can be concluded that at pH 7.5 the FOF1-activity depends on DcuACB. Moreover, DcuACB but not DcuD are working towards H+ uptake direction. DcuD contributes to H+ efflux at pH 7.5 while at pH 5.5 it affects H+ influx when external succinate is present.

Water‐dispersible polyaniline‐carbon nanotubes composites with interface covalent bond and their enhanced electrochemical and electrochromic properties

AbstractThe water‐dispersible electrochormic nanocomposites, polyaniline (PANI) connected multi‐walled carbon nanotubes (MWCNTs) by covalent bond were synthesized through a grafting polymerization process of aniline monomer with functionalized MWCNTs. N,N′‐dicyclohexylcarbodiimide (DCC) was used as dehydrant for functionalization process of MWCNTs with p‐phenylenediamine (PPD). The transmission electron microscope (TEM), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FT‐IR) were used to study the morphologies, thermal stabilities and chemical structures of the nanocomposites, respectively. The UV‐vis absorbance spectra and cyclic voltammetry behaviors of nanocomposites were tested by UV‐vis spectrometer and electrochemical workstation, respectively. It is shown show that PANI‐MWCNTs nanocomposites not only exhibit good water solubility, but also exhibit excellent film‐forming properties. The results confirm that the π‐π interactions and interfacial covalent bond between PANI and MWCNTs endow PANI‐MWCNTs excellent electrochemical and electrochromic properties. The conductive network composed of PANI and MWCNTs can significantly improve the ion transports, electron conduct and electrochromic performance of PANI. The PANI‐MWCNTs‐0.6% nanocomposite film shows highest optical contrast value (0.78) and shortest response time (3.8 seconds for coloring and 3.2 seconds for bleaching) among neat PANI and PANI‐MWCNTs nanocomposites.

Development of Novel Imaging Fluorescent Agents Bearing Anti-Inflammatory Drugs: Synthesis, Structural Characterization and Evaluation of Biological Activity

A new series of 5,6-benzocoumarin derivatives carrying anti-inflammatory drugs were synthesized via alkylamide spacers, the target to develop novel imaging fluorescent agents as useful technique to cancer early discovery. Experimentally, treatment of N-Boc-1,3-propanediamine with ethyl 5,6-benzocoumarin-3-carboxlate (III) under reflux conditions followed by hydrolyzed with CF3COOH to the corresponding primary amine (V), then treatment of derivative (V) with anti-inflammatory drugs have carboxylic group in presence of DCC (N,N'-dicyclohexylcarbodiimide) as catalyst and MeCN as solvent. The structure of the synthesized compounds was confirmed by FT-IR, NMR (1H,13C) spectral data as well as elemental analysis. The fluorescence properties study was investigated spectrophotometrically in methanol and maximum emission (λem) exhibited within range 411–436 nm, meanwhile, the quantum yields were calculated comparison to Rhodamine 6G as reference. Interestingly, the compound (III) gave a higher quantum yield (ΦF = 0.96), meanwhile, compounds (VII, VIII, IX and XI) gave reasonable quantum yields (ΦF) 0.60, 0.65, 0.78 and 0.84, respectively. All synthesized compounds were screened for their anti-AChE and antimicrobial activity. Based on the results, some of the compounds showed good activity in compared to the standard drugs.

A cautionary note on \u201cexothermic events\u201d upon contact of carbodiimide coupling agents and the cellulose solvent N-methylmorpholine-N-oxide

The cellulose solvent N-methylmorpholine-N-oxide monohydrate (NMMO) reacts violently with carbodiimide coupling agents, such as the widely used DCC (dicyclohexylcarbodiimide) and EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide), which can cause explosions, heavy smoke generation and complete charring of the reaction mixtures. For this reason it is clear that cellulose or other carbohydrates dissolved in NMMO (“Lyocell conditions”) cannot be safely esterified or amidified under DCC/EDC conditions. It is important to note that cellulosic material regenerated from NMMO solutions also poses a risk if it contains residual NMMO, which can then come into contact with DCC-type coupling agents in non-aqueous media, as recent accidents have unfortunately shown. Similarly, EDC/DCC traces in cellulose can have detrimental effects when trying to dissolve the material in NMMO. Working in aqueous systems generally reduces the risk of uncontrolled reactions, while alcohols or aprotic solvents are not very effective in this regard. Washing for NMMO removal or EDC/DCC removal should therefore always be carried out by aqueous media, if any possible, if there is a potential risk that the reagents might come into contact later. This warning describes the potential hazards of the reagent combination, highlights the underlying degradation mechanism and explains the precautions to be taken to avoid any “exothermic events”.Graphic abstract

Molecular Docking, G-QSAR Studies, Synthesis and Anticancer Screening of Some New 2-Phenazinamines as Bcr-Abl Tyrosine Kinase Inhibitors.

The computational studies on 2-phenazinamines with their protein targets have been carried out to design compounds with potential anticancer activity. This strategy of designing compounds possessing selectivity over specific tyrosine kinase has been achieved through G-QSAR and molecular docking studies. The objective of this research has been to design newer 2-phenazinamine derivatives as Bcr-Abl tyrosine kinase inhibitors by G-QSAR, molecular docking studies followed by wet lab studies along with evaluation of their anticancer potential. Computational chemistry was done by using VLife MDS 4.3 and Autodock 4.2 followed by wet lab experiments for synthesizing 2- phenazinamine derivatives. The chemical structures of ligands in 2D were drawn by employing Chemdraw 2D Ultra 8.0 and were converted into 3D. These were optimised by using semiempirical method called MOPAC. The protein structure was retrieved from RCSC protein data bank as PDB file. The binding interactions of protein and ligands were done by using PYMOL. The molecular properties of the designed compounds were predicted in silico by using Osiris property explorer. Later, we synthesized novel 13 2-phenazinamine derivatives by treating parent compound with various aldehydes in the presence of dicyclohexylcarbodiimide (DCC) and urea to afford 2-(2-chlorophenyl)-3-(phenazin-2-yl) thiazolidin-4-one and another series of derivatives synthesized with different aldehydes in the presence of p-toluylsulphonic acid, diphydropyridine and benzene sulfonyl chloride to afford benzenesulfonyl-N-(2-chlorobenzyl)-phenazin-2-amine. All the derivatives were tested for invitro anticancer activity on K562 human chronic myelogenous leukemia cell line by employing MTT assay method. The developed G-QSAR models were found to be statistically significant with respect to training (r2=0.8074), cross-validation (q2=0.6521), and external validation (pred_r2=0.5892). The best developed G-QSAR model suggested that the XlogP values of phenazinamine derivatives were found to be highly influential in determining biological activity. The standard drug was found to exhibit binding energy - 6.79 kcal/mol and the derivatives 5b and 6c exhibited binding energy of - 7.46 and - 8.51; respectively. Compounds 5b, 6c were observed to possess good lipophilicity and were found to exhibit better activity than other compounds in the series, although less than standard doxorubicin. The synthesis of these 2-phenazinamine derivatives (5a-m) is reported to be obtained from 2,4- dinitrodiphenylamine by applying appropriate synthetic route. Compounds 5b and 6c showed better cytotoxic activity against K562 cancer cell line when compared to other compounds of the series, although less than standard doxorubicin.

Discrete and Polymeric Cobalt Pyrophosphates Derived from Pyrophosphoric Acid Diester Ar2H2P2O7

While the structural elucidation and coordination chemistry of organo‐monophosphates have been well investigated, research on the simplest member of organo‐oligophosphates, viz. diorganopyrophosphates, is relatively rare due to the inherent hydrolytic instability of the ligand. Water elimination from the 2,6‐diisopropyl phenyl phosphate (dippH2) by the action of dicyclohexylcarbodiimide (DCC) results in the isolation of a diorganopyrophosphates ligand formulated as [O{P(OAr)(OH)(O)}2] (1 or pyrodippH2) (Ar = 2,6‐diisopropylphenyl). Due to the instability of 1, it has been transformed into its sodium salt [O{P(OAr)(ONa)(O)}2] (2), which has been used for further reactions to prepare cobalt pyrophosphate complexes 3–7. Reaction of 2 with anhydrous cobalt(II) chloride in the presence of N‐heterocyclic ligands results in the formation of [Co(pyrodipp)(imz)3] (3), [Co(pyrodipp)(bpy)2](CH3OH) (4) and [Co(pyrodipp)(phen)2] (5) (imz = imidazole; bpy = 2,2'‐bipyridine; phen = 1,10‐phenanthroline). Use of multidentate ancillary ligand such as 4‐pyridyl‐2,2':6',2''‐terpyridine (pyterpy) under similar reaction conditions leads to the formation of a one‐dimensional zig‐zag cobalt pyrophosphate coordination polymer [Co(pyrodipp)(pyterpy)(CH3OH)]n (6). In the absence of any ancillary ligand, the reaction between cobalt(II) chloride and 2 in acetonitrile results in the isolation of an interesting inorganic polymer [Co(pyrodipp)(CH3CN)2]n (7), whose backbone consists of a chain of spirocycles of CoP2O3 rings, joined at the cobalt centers. The newly synthesized cobalt pyrophosphates 3–7 have been characterized by both analytical and spectroscopic techniques, magnetic studies apart from single‐crystal X‐ray diffraction studies in each case. A striking and persistent structural feature in 3–7 is the presence of the cobalt pyrophosphate six‐membered metallacycle Co(OPOPO). While cobalt metal exists in trigonal bipyramidal geometry in complex 3, distorted octahedral coordination geometry is observed for cobalt centers in complexes 4–7.

Rivet-Inspired Modification of Aramid Fiber by Decorating with Silica Particles to Enhance the Interfacial Interaction and Mechanical Properties of Rubber Composites.

A rivet–inspired method of decorating aramid fiber (AF) with silica particles (SiO2) is proposed to produce SiO2@AF hybrid materials that have largely enhanced interfacial interaction with the rubber matrix. AF was firstly surface-modified with polyacrylic acid (PAA) to obtain PAA–AF, and SiO2 was silanized with 3-aminopropyltriethoxysilane to obtain APES–SiO2. Then, SiO2@AF was prepared by chemically bonding APES–SiO2 onto the surface of PAA–AF in the presence of dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP). With the incorporation of SiO2@AF into the rubber matrix, SiO2@AF hybrid materials with high surface roughness can play a role as ‘rivets’ to immobilize large numbers of rubber chains on the surface. The tear strength and tensile strength of rubber composite that filling 4 phr SiO2@AF are dramatically increased by 97.8% and 89.3% compared to pure rubber, respectively. Furthermore, SiO2@AF has superiority in enhancing the cutting resistance of rubber composites, in contrast with unmodified AF and SiO2. SiO2@AF is suitable to be applied as a novel reinforcing filler in rubber composites for high performance.

Recyclable heterogeneous palladium-catalyzed carbonylative Sonogashira coupling under CO gas-free conditions

A convenient, efficient and practical heterogeneous palladium-catalyzed carbonylative Sonogashira coupling of aryl iodides with terminal alkynes under CO gas-free conditions has been developed by using an MCM-41-supported bidentate phosphine palladium acetate complex as catalyst. Here, formic acid was used as the CO source with dicyclohexylcarbodiimide (DCC) as the activator and a wide variety of alkynyl ketones were generated in moderate to high yields. This heterogeneous palladium catalyst can be easily recovered via a simple filtration process and recycled up to 8 times without apparent loss of activity.

Tuning the Wrinkles in 3D Graphene Architectures for Mass and Electron Transport

AbstractDue to the high in‐plane Young's modulus and defects, graphene is prone to deformations such as wrinkles. The effects of wrinkles on the mass and electron transport properties need to be elucidated as graphene has great potential in applications such as catalysis, sensors, energy storage, and conversion. In this paper, the wrinkling of graphene oxide sheets is dominated by the mass ratio of graphene oxide to N,N′‐dicyclohexylcarbodiimide (DCC) to fabricate 3D graphene architectures (TDGAs) with tunable porosity. This template‐free DCC tactic of regulating the wrinkling procedure forms hierarchical porosity and modulates the exposure of defect sites. Considering the confinement effect of the wrinkles and defect sites, orthorhombic phase Nb2O5 (T‐Nb2O5) nanoparticles are loaded onto TDGAs, and as‐obtained T‐Nb2O5@TDGAs composites exhibit favorable properties of Li‐ion and electron transport after the wrinkle structures are optimized. The DCC tactic manifests excellent performance in manipulating mass transport properties through tuning the wrinkles on TDGAs‐based composites, which may greatly contribute to graphene based materials with high performances in energy storage.

Synthesis, Antitubercular Activity, Molecular Modeling and Docking Studies of Novel Thiazolidin-4-One Linked Dinitrobenzamide Derivatives

Background: Tuberculosis is a catastrophe sprawled across the world. The World Health Organization Global Tuberculosis Report 2017 inferred that there were an estimated 10.4 million people suffered from tuberculosis including 490000 Multidrug-Resistant TB (MDR-TB) cases. Several new lead molecules like dinitrobenzamide derivatives were found to be highly active against multidrugresistant strains of M. tuberculosis. To further explore the pharmacophoric space around the dinitobenzamide moiety, a series of compounds have been synthesized by linking it with the thiazolidin- 4-one. The presented work is an effort to study the biological effect of thiazolidin-4-one scaffold on dinitrobenzamide derivatives as antitubercular agents. A molecular modeling study was also performed on the synthesized molecules to reveal the requirements for further lead optimization. Methods: The thiazolidin-4-one linked 3,5-dinitrobenzamide derivatives have been synthesized by onepot three-component condensation reaction of an amine, substituted aldehydes and thioglycolic acid in presence of N, N'-Dicyclohexylcarbodiimide (DCC). These compounds were evaluated against Mycobacterium tuberculosis H37Ra. A pharmacophore modeling approach has been used in order to explore the collection of possible pharmacophore queries of thiazolidin-4-one linked 3, 5-dinitrobenzamide derivatives against M. tuberculosis. The synthesized compounds were docked on to the M. tuberculosis DprE1 enzyme to identify the structural features requirement of these analogs against this potential target of M. tuberculosis. Results: The synthesized compounds showed the antitubercular activity in the range of 6.25-50 μg/ml. The pharmacophore modeling suggests that the presence of aromatic moiety, thiazolidin-4-one ring and one of the nitro groups are significant for inhibiting the enzymatic activity. While docking studies showed that hydrophobic and hydrogen bond interactions of the aromatic moiety and nitro group crucial to inactivate the DprE1 enzyme. Conclusion: The study showed that the linking of thiazolidin-4-one with dinitrobenzamide leads to compounds active against M. tuberculosis. These findings also suggested that further lead optimization would be carried out by focusing on the aromatic system along with electron-rich substituents placed on the thiazolidin-4-one for making better hydrophobic and hydrogen bond interactions with the DprE1 target.

Effect of different coupling agents in the doping of graphite oxide with 3–3′ diaminobenzidine: textural, structural and electrical properties

The doping reactions of graphite oxide (GO) with 3-3′-diaminobenzidine (DAB) were studied using N, N′-dicyclohexylcarbodiimide (DCC), cyanuric chloride (CC) and hexafluorophosphate (HATU) as coupling agents. The bifunctionality of the coupling agents aid to interact GO functional groups with amino groups of DAB without being part of the final product. The doped materials (d-GO) and GO were characterized by thermogravimetric analysis, x-ray diffraction, FTIR/Raman spectroscopy, x-ray photoelectron, high-resolution electron microscopy and cyclic voltammetry. The GO-HATU material was more thermally stable than other graphitic material, with at 10% weight loss at 300 °C, this thermal stability is related to a more difficult intramolecular physisorbed water removal process than the other d-GO materials. GO-CC and GO-HATU materials presented 8.2 and 8.0 Å of interlayer spacing, which was associated with a good oxidation-doping process. Besides, these two materials showed modifications in the vibrations by FTIR technique, corresponding to epoxy and hydroxyl groups of the GO being more susceptible to react with the amino groups. Moreover, ID/IG ratio calculated by Raman Spectroscopy presents the following trend 0.70, 0.94, 0.97 and 1.04 for GO, GO-CC, GO-DCC and GO-HATU, respectively, this increase is related with a major disorder during the doping process. XPS analysis shows C–N and N=C bands for high resolution of C 1s and N 1s, respectively, for d-GO materials. This possibly suggests the formation of benzimidazoles during the oxidation-doping process, this generates a similar -non-lattice and -lattice oxygen amount for O 1s related to crosslinking between the functional groups of GO and DAB which improve the electronic mobility between the surface and the bulk of the final graphitic material. Finally, the obtained d-GO materials were investigated as a working electrode for electrochemical capacitors and all of them showed typical capacitive behaviour.

Fibril formation through self-assembly of a simple glycine derivative and X-ray diffraction study

Abstract N-(N-benzoyl glycinyl)-N,N′-dicyclohexylurea was synthesised by conjugating N-benzoyl glycine and dicyclohexylcarbodiimide (DCC) using triethylamine as base catalyst. A single crystal X-ray diffraction study reveals that the compound self-assembles into a supramolecular sheet structure by intermolecular N–H · · · O, C–H · · · O hydrogen bonding and non-bonding van der Waals interactions. A high resolution transmission electronic microscopic (HR-TEM) image of the compound exhibits formation of fibrils in the solid state.

A Na+ A1 AO ATP synthase with a V-type c subunit in a mesophilic bacterium.

A1 AO ATP synthases with a V-type c subunit have only been found in hyperthermophilic archaea which makes bioenergetic analyses impossible due to the instability of liposomes at high temperatures. A search for a potential archaeal A1 AO ATP synthase with a V-type c subunit in a mesophilic organism revealed an A1 AO ATP synthase cluster in the anaerobic, acetogenic bacterium Eubacteriumlimosum KIST612. The enzyme was purified to apparent homogeneity from cells grown on methanol to a specific activity of 1.2U·mg-1 with a yield of 12%. The enzyme contained subunits A, B, C, D, E, F, H, a, and c. Subunit c is predicted to be a typical V-type c subunit with only one ion (Na+ )-binding site. Indeed, ATP hydrolysis was strictly Na+ -dependent. N,N'-dicyclohexylcarbodiimide (DCCD) inhibited ATP hydrolysis, but inhibition was relieved by addition of Na+ . Na+ was shown directly to abolish binding of the fluorescence DCCD derivative, NCD-4, to subunit c, demonstrating a competition of Na+ and DCCD/NCD-4 for a common binding site. After incorporation of the A1 AO ATP synthase into liposomes, ATP-dependent primary transport of 22 Na+ as well as ΔµNa+ -driven ATP synthesis could be demonstrated. The Na+ A1 AO ATP synthase from E.limosum is the first ATP synthase with a V-type c subunit from a mesophilic organism. This will enable future bioenergetic analysis of these unique ATP synthases.

Slow zeaxanthin accumulation and the enhancement of CP26 collectively contribute to an atypical non‐photochemical quenching in macroalga Ulva prolifera under high light

Non-photochemical quenching (NPQ) is an important photoprotective mechanism in plants, which dissipates excess energy and further protects the photosynthetic apparatus under high light stress. NPQ can be dissected into a number of components: qE, qZ, and qI. In general, NPQ is catalyzed by two independent mechanisms, with the faster-activated quenching catalyzed by the monomeric light-harvesting complex (LHCII) proteins and the slowly activated quenching catalyzed by LHCII trimers, both processes depending on zeaxanthin but to different extent. Here, we studied the NPQ of the intertidal green macroalga, Ulva prolifera, and found that the NPQ of U.prolifera lack the faster-activated quenching, and showed much greater sensitivity to dithiothreitol (DTT) than to dicyclohexylcarbodiimide (DCCD). Further results suggested that the monomeric LHC proteins in U.prolifera included only CP29 and CP26, but lacked CP24, unlike Arabidopsis thaliana and the moss Physcomitrella patens. Moreover, the expression levels of CP26 increased significantly following exposure to high light, but the concentrations of the two important photoprotective proteins (PsbS and light-harvesting complex stress-related [LhcSR]) did not change upon the same conditions. Analysis of the xanthophyll cycle pigments showed that, upon exposure to high light, zeaxanthin synthesis in U.prolifera was gradual and much slower than that in P.patens, and could effectively be inhibited by DTT. Based on these results, we speculate the enhancement of CP26 and slow zeaxanthin accumulation provide an atypical NPQ, making this green macroalga well adapted to the intertidal environments.

Synthesis, characterisation, and DNA interaction studies of novel Cu(II), Ni(II), and Co(II) mono and bisligand complexes of N-(1,10-phenanthrolin-5-yl)acridine-9-carboxamide

A novel acridine-linked phenanthroline ligand, N-(1,10-phenanthrolin-5-yl)acridine-9-carboxamide, (PAC) was synthesized by N,N’-dicyclohexylcarbodiimide (DCC) coupling between acridine-9-carboxylic acid and 1,10-phenanthroline-5-amine. A set of new complexes of general formulae [M(PAC)(N3)2] and [M(PAC)2(N3)2] where M = Cu(II), Ni(II), and Co(II) metal ions were synthesized and characterised by spectroscopic, electrochemical, and thermogravimetric methods. Interactions of complexes with Calf Thymus DNA were investigated using UV–visible absorption studies, fluorescent intercalator displacement assays, viscosity measurements, and cyclic voltammetric studies in phosphate buffer at pH 7.2. All the synthesized complexes were found to be potential DNA-binding agents, with significant quenching of fluorescence with the addition of DNA. Hypochromic shifts of the absorption bands with well-defined isosbestic points were observed for all complexes in the presence of the nucleic acid and the binding constants (Kb) calculated revealed high binding affinities of the complexes. Viscosity and cyclic voltammetric measurements supported appreciable intercalative interactions between the complexes and DNA.

Construction of poly(ethylene glycol)-poly(L-lactic acid)-stearic acid aspirin-loaded reverse micelles and optimization of preparation process

ABSTRACT This work aims to study the construction of reverse aspirin-loaded micelles prepared from amphiphilic PEG-PLA-SA triblock copolymers and the optimization of the preparation process. Using polyethylene glycol (PEG) as the initiator, ring-opening polymerization of L-lactide (L-LA) was used to prepare PEG-PLA diblock copolymers. Final product PEG-PLA-SA triblock copolymers were prepared by the reaction of stearic acid (SA) and PEG-PLA catalyzed by 4-dimethylaminopyridine (DMAP) and N,N’-Dicyclohexylcarbodiimide (DCC). Fourier transform infrared spectrometer (FT-IR) was used to characterize the product structure. PEG-PLA-SA triblock copolymers self-assembled in toluene/ethanol/water system to form reverse micelles, which could encapsulate aspirin into a hydrophilic core. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to determine the size and morphology of reverse micelles. The results showed that the reverse micelles are spherical, with a particle size of less than 70 nm. Response surface analysis method was applied to optimize the preparation process of PEG-PLA-SA. In vitro drug release was achieved by embedding reverse aspirin-loaded micelles in the biocompatible membrane in phosphate buffer saline (PBS) at 37°C. In the first 8 h, the drug release rate of the triblock copolymers was slower than that of the diblock copolymers. After 8 h, the drug release rate of both tended to be flat. The stability of aspirin-loaded reverse micelles was studied through accelerated test. These results indicate that reverse micelle PEG-PLA-SA may be a promising carrier for hydrophilic drugs like aspirin.

Cost-Effective Detection of Perfluoroalkyl Carboxylic Acids with Gas Chromatography: Optimization of Derivatization Approaches and Method Validation.

The reliable quantification of perfluoroalkyl carboxylic acids (PFCAs) in environmental samples like surface water by using gas chromatography (GC) remains challenging because the polar PFCAs call for derivatization before injection and problems involving the integration of sample pretreatment and derivatization procedures. Here we proposed a cost-effective method for the GC based determination of C4–C12 PFCAs in surface water samples by integrating solid phase extraction and PFCAs anilide derivatization. First, we assessed the performance of different PFCAs derivatization methods, namely esterification and amidation. Esterification was unable to derivatize C4–C6 PFCAs. On the contrary, amidation procedures by using 2,4-difluoroaniline (DFA) and N,N′-dicyclohexylcarbodiimide (DCC) could successfully transform all the PFCA analogs to produce anilide derivatives, which could be easily detected by GC. Then the reaction conditions in the amidation approach were further optimized by using orthogonal design experiments. After optimizing the instrumental parameters of GC, the limits of detection (LOD) of this derivatization method were determined to be 1.14–6.32 μg L−1. Finally, in order to establish an intact method for the quantification of PFCAs in surface water samples, solid phase extraction (SPE) was used for extraction and cleanup, which was further integrated with the subsequent amidation process. The SPE-amidation-GC method was validated for application, with good accuracy and precision reflected by the PFCAs recoveries and derivatization of triplicates. The method reported here could provide a promising and cost-effective alternative for the simultaneous determination of C4–C12 PFCAs in environmental water samples.

Formate and potassium ions affect Escherichia coli proton ATPase activity at low pH during mixed carbon fermentation

Escherichia coli is able to ferment not only single but also mixtures of carbon sources. The formate metabolism and effect of formate on various enzymes have been extensively studied during sole glucose but not mixed carbon sources utilization. It was revealed that in membrane vesicles (MV) of wild type cells grown at pH 7.5 during fermentation of the mixture of glucose (2 g/L), glycerol (10 g/L), and formate (0.68 g/L), in the assays, the addition of formate (10 mM) increased the N,N'-dicyclohexylcarbodiimide (DCCD)-inhibited ATPase activity on ~30% but no effect of potassium ions (100 mM) had been detected. In selC (coding formate dehydrogenases) and fdhF (coding formate dehydrogenase H) single mutants, formate increased DCCD-inhibited ATPase activity on ~40 and ~70%, respectively. At pH 5.5, in wild type cells MV, formate decreased the DCCD-inhibited ATPase activity ~60% but unexpectedly in the presence of potassium ions, it was stimulated ~5.8 fold. The accessible SH or thiol groups number in fdhF mutant was less by 28% compared with wild type. In formate assays, the available SH groups number was less ~10% in wild type but not in fdhF mutant. Taken together, the data suggest that proton ATPase activity depends on externally added formate in the presence of potassium ions at low pH. This effect might be regulated by the changes in the number of redox-active thiol groups via formate dehydrogenase H, which might be directly related to proton ATPase FO subunit.