Mixture Of Dimethylformamide Research Articles

Room temperature synthesis of polyvinyl alcohol stabilized palladium nanoparticles: Solvent effect on shape and electro-catalytic activity

Palladium nanoparticles have been synthesized at room temperature, 25±.5°C by the reduction of K2PdCl4 using biocompatible polymer polyvinyl alcohol (PVA) as reducing and stabilizing agent in water and aqueous dimethyl formamide (DMF) media with varying composition of DMF. The effect of variation of composition of aqueous DMF on growth, morphology and size of palladium nanocrystals is explained. Different aqueous DMF mixtures furnish palladium nanoparticles of different shapes like triangular plates, cuboids, hexagon with different average edge length between (3–30 nm) indicating preferential interaction and blocking of DMF to some specific planes of nanocrystals leading to various shapes. The synthesized nanoparticles have been characterized by different spectroscopic, microscopic and electro-analytical studies like cyclic voltammetry (CV), chronopotentiometry (CP) and chronoamperometry (CA). The increase in electro-catalytic activity is found to decrease with the increased size of the embedded crystallites deposited on the support constituting the electrodes and hence on the precursor medium. The same order of the studied electrodes is found from mole normalized peak current density values (Amol−1Pd) in CV, transition time in CP and steady current density values in CA, on increasing the content of DMF in the aqueous DMF solvent system as expected. The outcomes are explained on the basis of the crystallite size, morphology of the surface, unequal development of certain planes and purity of the products as guided by the rate of nucleation and growth of the particles formed in different media.

A Comparative study of Vilsmeier-Haack Formylation Reactions With Phenols Under Solvent Less And Solvent Conditions

The Vilsmeier-Haack reaction with phenols has been carried out under solvent free conditions and as well as solvent conditions. The reactants are taken in a mortar and grounded with a pestle for about 20 to 30 min at room temperature. The reactants are taken in a beaker and placed in microwave for about 30 secs to 1 min. The reactions afforded formyl derivatives in fairly good yields when a mixture of dimethyl formamide (DMF) and SOCl2 is used as VH reagent. Results of solvent free reactions are more superior over solution phase reactions with very good yields and far lesser reaction times.

Extractive distillation of methylal/methanol mixture using the mixture of dimethylformamide (DMF) and ionic liquid as entrainers

Methylal is used as an important synthetic fuel blended with diesel oil to reduce the particulate emissions of toxic gas pollutants without affecting the energy density. The mixed entrainers (dimethylformamide (DMF) + ionic liquid (IL)) are proposed to replace conventional DMF for the separation of methylal and methanol by extractive distillation. [EMIM]+[Ac]− might be the most promising entrainer screened by COSMO-RS model considering relative volatility and solvent capacity together. Vapor–liquid equilibrium (VLE) experiments demonstrated that the relative volatility of methylal to methanol is obviously improved after the addition of [EMIM]+[Ac]− into DMF. Moreover, the UNIFAC-Lei model was extended to the methylal-methanol-DMF-IL system, and the corresponding interaction parameters were obtained and input into the equilibrium (EQ) stage model established in this work. Based on the thermodynamic study, process simulation was developed. It was found that the overall heat duty of reboilers decreased 9.25% using the proposed mixed entrainers when compared to pure DMF. In addition, the COSMO-RS model and DFT calculation provide some theoretical insights into the separation mechanism.

Cadmium(ii) terephthalates based on trinuclear units {Cd3(bdc)3}: control of coordination structure dimensionality and luminescence properties

Two metal-organic coordination polymers based on cadmium(ii) ions and terephthalic (1,4-benzenedicarboxylic) acid were synthesized in dimethylformamide or a mixture of dimethylformamide and methanol: [Cd3(bdc)3(dmf)4] (1, bdc is 1,4-benzenedicarboxylate, dmf is N,N´-dimethylformamide) and [Cd3(bdc)3(dmf)2] (2), respectively. According to the single-crystal X-ray diffraction data, both compounds are built up by the trinuclear carboxylate units {Cd3(O2CR)6}. Compound 1 has a layered structure, whereas compound 2 has a three-dimensional structure due to the presence of additional coordination interactions between adjacent trinuclear units and the formation of polymer chains {Cd3(dmf)2(μ2-O2CR-κ1,κ1)2(μ2-O2CR-κ2,κ1)4(O2CR-κ1)2}. The synthesized compounds were characterized by IR spectroscopy, thermogravimetric analysis, elemental analysis, and powder X-ray diffrac- tion. The luminescence properties of these compounds provide evidence for the existence of both intraligand and charge-transfer transitions. The luminescence quantum yields for both compounds are 10%.

Some perspectives on nitrogen-doped carbon nanotube synthesis from acetonitrile and N,N′-dimethylformamide mixtures

This work reports on the influence of the ratio of sp3 (N,N′-dimethylformamide, DMF) to sp (acetonitrile) hybridised nitrogen within the carbon source used in the synthesis of nitrogen-doped carbon nanotubes (N-CNTs) by means of the floating catalyst chemical vapour deposition method. The physicochemical properties of the N-CNTs were investigated by means of scanning and transmission electron microscopies, textural characteristics, powder X-ray diffraction, X-ray photoelectron spectroscopy, thermal gravimetric analysis and elemental analysis. When the two nitrogen sources were compared before mixing, it was found that sp3 hybridised nitrogen in DMF was a more effective source for the incorporation of nitrogen atoms (5.87%) than sp hybridised nitrogen in acetonitrile (3.49%). The number of walls within the N-CNT synthesised from the sp3 nitrogen source was tailored by changing the synthesis temperature. Overall, a 1:3 sp3:sp ratio produced N-CNTs with the highest nitrogen content of 9.38% and a general abundance of pyrrolic nitrogen moieties within the samples. The best synthesis temperature in terms of nitrogen content and largest composition of N-CNTs with least residual iron was found to be 900 °C. Varying ratio of sp3:sp hybridised nitrogen is suitable for tailoring the physicochemical properties of N-CNTs towards preferred applications.

Synthesis and spectral properties of β-bromo-substituted nickel(II) tetraphenylporphyrins

Bromination of (5,10,15,20-tetraphenylporphyrinato)nickel(II) with N-bromosuccinimide in chloroform and chloroform–dimethylformamide mixture and complexation of 2-bromo-5,10,15,20-tetraphenylporphyrin and 2,3,12,13-tetrabromo-5,10,15,20-tetraphenylporphyrin with nickel(II) acetate in dimethylformamide have been studied. The resulting nickel(II) complexes with mono-, tetra-, and octabromo-5,10,15,20-tetraphenylporphyrins have been identified by electronic absorption, IR, 1H NMR, and mass spectra.

An Insight into a Fascinating DMF‐Water Mixed Solvent System: Physicochemical and Electrochemical Studies

AbstractA systematic study of electrical conductivity, density and viscosity over solutions of tetraethylammonium bromide(TEAB) and 1‐butyl‐3‐methylimidazolium methylsulfate ([BMIM][MeSO4]) in variedly composed dimethyl formamide (DMF) plus water mixtures was carried to explore the potential advantages of such mixed solvent systems for electrochemical investigations. The estimated transport and bulk characteristics of TEAB and [BMIM][MeSO4] in the mixed solvent revealed strong composition dependent interactions are present in the DMF‐Water mixed solvent systems. Such results intrigued us to study the impact of solution properties of DMF‐water systems on electrochemical behavior of redox probe para‐nitrotoluene (PNT).The estimated transport, kinetic and thermodynamic parameters were correlated with the estimated values for viscosity, density and calculated values of dielectric constant for the mixed solvent. The kinetics of PNT was found to be controlled by outer sphere solvent reorganization in DMF‐water solvent system for both the supporting electrolytes viz. TEAB and [BMIM][MeSO4], upto composition range of 0.35 mole fraction of DMF in water.

The Effect of Solvents on the Performance of CH3NH3PbI3 Perovskite Solar Cells

The properties of perovskite solar cells (PSCs) fabricated using various solvents was studied. The devices had an indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS)/CH3NH3PbI3 (fabricated by using various solvents)/fullerene (C60)/bathocuproine (BCP)/silver (Ag) structure. The solvents used were dimethylformamide (DMF), γ-butyrolactone (GBL), dimethyl sulfoxide (DMSO), a mixture of DMSO and DMF (1:1 v/v), and a mixture of DMSO and GBL (DMSO: GBL, 1:1 v/v), respectively. The power conversion efficiency (PCE) of the device fabricated using DMF is zero, which is attributed to the poor coverage of CH3NH3PbI3 film on the substrate. In addition, the PCE of the device made using GBL is only 1.74% due to the low solubility of PbI2 and CH3NH3I. In contrast, the PCE of the device fabricated using the solvents containing DMSO showed better performance. This is ascribed to the high solubilization properties and strong coordination of DMSO. As a result, a PCE of 9.77% was obtained using a mixed DMSO:GBL solvent due to the smooth surface, uniform film coverage on the substrate and the high crystallization of the perovskite structure. Finally, a mixed DMSO: DMF:GBL (5:2:3 v/v/v) solvent that combined the advantages of each solvent was used to fabricate a device, leading to a further improvement of the PCE of the resulting PSC to 10.84%.

The effect of surface treatment in polyacrylic acid solution on the photoluminescent properties of porous silicon

Porous silicon (por-Si) has a unique combination of physicochemical parameters: well-developed surface and hence high sorption. Depending on technology it is possible to form nanometer size pores and clusters in porous silicon which makes this material promising for developments in the field of optoelectronics and sensors. However the high surface activity makes por-Si unstable when exposed to atmosphere.In this work we have studied the effect of por-Si surface treatment in a polyacrylic acid water solution on the composition and photoluminescence (PL) of the material. Por-Si was produced from two fluoric acid solutions. One was a standard solution of fluoric acid, isopropyl alcohol and hydrogen peroxide, and the other was a mixture of fluoric acid and dimethylformamide. We have shown that depending on por-Si technology, its treatment in polyacrylic acid solution allows increasing and stabilizing por-Si PL or changing PL band position and significantly increasing its integral intensity.

A thermodynamic study of complexation process between N,N′-dipyridoxylidene(1,4-butanediamine) and Cd2+ in some binary mixed solvents using conductometry

Complexation of the Cd2+ ion with N,N′-dipyridoxylidene(1,4-butanediamine) Schiff base was studied in pure solvents including acetonitrile (AN), ethanol (EtOH), methanol (MeOH), tetrahydrofuran (THF), dimethylformamide (DMF), water (H2O), and various binary solvent mixtures of acetonitrile–ethanol (AN–EtOH), acetonitrile–methanol (AN–MeOH), acetonitrile–tetrahydrofuran (AN–THF), acetonitrile–dimethylformamide (AN–DMF), and acetonitrile–water (AN–H2O) systems at different temperatures using the conductometric method. The conductance data show that the stoichiometry of complex is 1: 1 [ML] in all solvent systems. A non-linear behavior was observed for changes of log K f of [Cd(N,N′-dipyridoxylidene(1,4-butanediamine)] complex versus the composition of the binary mixed solvents, which was explained in terms of solvent–solvent interactions. The results show that the thermodynamics of complexation reaction is affected by the nature and composition of the mixed solvents.

Porosity and swelling properties of novel polyurethane–ascorbic acid scaffolds prepared by different procedures for potential use in bone tissue engineering

In this work, a novel polyurethane (PU) system based on poly(ethylene-butylene) adipate diol, 1,6-hexamethylene diisocyanate, 1,4-butanediol, and ascorbic acid was used to prepare scaffolds with potential applications in bone tissue engineering. Two fabrication methods to obtain porous materials were chosen: phase separation (PS)/salt particle leaching (PL) and solvent casting (SC)/salt PL. The calculated porosity demonstrated that scaffolds with a higher porosity were obtained (76–86%) using the PS/PL method. The morphology of pores was examined with the use of optical stereomicroscope and scanning electron microscope. The appropriate porosity, pore morphology, and swelling properties for bone tissue scaffolds were obtained for our novel PU system by the PS/PL method using 15 wt% solution of PU in the mixture of dimethylformamide (DMF)/tetrahydrofuran solvents and by SC/PL method from 20 wt% from DMF. The distilled water and saline water swelling for those samples was also appropriate for bone tissue scaffold application.

Complexation and Phase Evolution at Dimethylformamide–Ag(111) Interfaces

The interaction of solvent molecules with metallic surfaces impacts many interfacial chemical processes. We investigate the chemical and structure evolution that follows adsorption of the polar solvent dimethylformamide (DMF) on Ag(111). An Ag(DMF)2 coordination complex forms spontaneously by DMF etching of Ag(111), yielding mixed films of the complexes and DMF. Utilizing ultrahigh vacuum scanning tunneling microscopy (UHV–STM), in combination with X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) computations, we map monolayer phases from the 2-D gas regime, consisting of a binary mixture of DMF and Ag(DMF)2, through the saturation monolayer limit, in which these two chemical species phase separate into ordered islands. Structural models for the near-square DMF phase and the chain-like Ag(DMF)2 phase are presented and supported by DFT computation. Interface evolution is summarized in a surface pressure–composition phase diagram, which allows structure prediction over arbitrary experimental conditions. This work reveals new surface coordination chemistry for an important electrolyte–electrode system and illustrates how surface pressure can be used to tune monolayer phases.

Interpretation of Association Behavior and Molecular Interactions in Binary Mixtures from Thermoacoustics and Molecular Compression Data

Density and acoustic velocity were measured for binary liquid mixtures of formamide, N-methylacetamide (NMA), dimethylformamide (DMF), and dimethylacetamide (DMA) with acetonitrile at atmospheric pressure and 293.15 K, 298.15 K, 303.15 K, 308.15 K, or 313.15 K over the concentration range 0.12 to 0.97. Models assuming association and nonassociation of the components of the mixtures were used to predict the behavior of the studied liquids, which would typically show weak interactions. The measured properties were fitted to the Redlich–Kister polynomial to estimate the binary coefficients and standard errors. The data were used to study the molecular interactions in the binary mixtures. Furthermore, the McAllister multibody interaction model was used to correlate the properties of the binary liquid mixtures. Testing of the nonassociation and association models for the different systems showed that, compared with the nonassociation model theoretical results, the association model theoretical results were more consistent with the experimental results.

Ultralong Perovskite Microrods: One- versus Two-Step Synthesis and Enhancement of Hole-Transfer During Light Soaking

In this work, a two-step synthesis of CH3NH3PbI3 perovskite microrods involving first the production of PbI2 microrods by the evaporation of a dimethylformamide (DMF) solution of PbI2 is introduced. The PbI2 rods, acting as a shape template, yield rod-like perovskites of similar lengths and diameters when immersed in a solution of CH3NH3I. When comparable amounts of PbI2 are used, the two-step synthesis produces perovskite microrods that are shorter and more uniform in length than the ones prepared by a one-step synthesis via the evaporation of a DMF mixture of PbI2 and CH3NH3I. This is due to an uncontrolled crystal growth reaction in the one-step synthesis versus a nucleation dominated one in the two-step synthesis. The hole-transfer dynamics from the as-prepared perovskite rods to spiro-OMeTAD is also examined. Both the photoluminescence (PL) intensity and lifetime of the perovskite in the absence of spiro-OMeTAD are found to be enhanced as the CH3NH3PbI3 rods are continuously exposed to the excitation...

Preparation and characterization of dual-template molecularly imprinted monolith with metal ion as pivot

In this work, a method for improving imprinting efficiency of dual-templates molecularly imprinted polymer was developed based on strategy of metal ion as pivot. Two templates, naproxen (NAP) and ketoprofen (KET), were simultaneously imprinted using 4-vinylpyridine (4-VP) as functional monomer and ethylene glycol dimethacrylate (EDMA) as cross-linker with Co2+ as pivot. A ternary mixture of dimethyl formamide (DMF)- dimethyl sulfoxide (DMSO)- 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) was used as the porogenic system. The resulting metal ion mediated, dual-templates molecularly imprinted monolith (MDMIM) showed excellent selectivity to the templates and analogues. In contrast to traditionally formulated MIPs made with multi-templates, reduced recognition ability toward targeted analytes on the MDMIM was not found. The structural properties of MDMIM were determined from Fourier transform infrared spectra, mercury intrusion and extrusion experiments and nitrogen adsorption–desorption isotherms. The MDMIM was then tested in the chromatographic mode due to its ability to recognize the templates. The studies of Van’t Hoff analysis indicated that the separation of the templates and their analogues on the MDMIM was an enthalpy controlled process. Collectively, metal ion as pivot is demonstrated as an effective method of imprinting dual-templates simultaneously without loss of selectivity.

(Congreso Nacional de la Sociedad Mexicana de Electroquímica Poster Winner) Capillary Electrophoresis Coupled on Line with Mass Spectrometry Via an Electrospray Interface (CE-ESI-MS) for the Characterization of Cyclic Peptides and Their Possible Aggregation into Peptide Nanotubes

Innovation in analytical methodologies is of high impact for biomedical and environmental applications. In this context, electrokinetic methods represent powerful tools allowing selective and ultrasensitive separations. They are easy to run, versatile, of high efficiency and require very small sample amounts. One way to improve separations is to develop new nanosupports that can be integrated within the capillaries or microchannel, so as to increase separation selectivity and to generate specific interactions with some analytes[1 ]. Thereon, we aim at developing Peptide Nanotubes (PNTs) as new nanosupports, as their structure can offer high diversity and surface functionalization, they are biocompatible and stable in different media. Their cylindrical structure could be used as sieving tools to separate small compounds, amplifying possible applications. The synthesis of PNTs depends on the cyclic peptide (CP) monomers structure and concentration. It is therefore crucial to realize the physicochemical characterization of these CPs. Then, we developed a new capillary electrophoretic method coupled on line with mass spectrometry via an electrospray interface (CE-ESI-MS) to characterize the monomers, and the study of their possible aggregation. Metodology We synthesized 8 CPs (Table 1) of three internal diameters via 8, 10 and 12 D, L alternated amino acids by Fmoc-solid phase peptide synthesis technique[2]. They were purified by HPLC and the purity was determined by the development of CE-ESI-MS methodology, which allowed identifying their corresponding molecular ions, isotopes and some adducts with NH4 + and Na+. CE analysis were performed in zone mode (λ=200nm) at 25°C, with separation at 20kV along pressure application (50mbar). BGE used was 10mM ammonium carbonate (pH8.0)/EtOH (50/50, v/v), and 10mM ammonium formiate (pH3.0)/EtOH (50/50, v/v). The neutral marker was a mixture of dimethylformamide (UV detection) and glucose (MS detection). Fused silica capillaries were of 75µm internal diameter, 80cm total length and 20cm detection length. They were previously activated by successive flushes of NaOH 1M, NaOH 0.1M, H2O and BGE (934mbar) during 15 min each. Sample concentration was 3mM (dissolved in 0.1mM BGE). MS measurements (SCAN and SIM) were done with a sheath liquid composed of H2O/EtOH (10/90, v/v) containing 2.0% AcOH (0.6µL/min), a nebulizing gas (N2,g) at 10psi pressure, and a drying gas (N2,g) at 250°C (6L/min). Fragmentor voltage was fixed at 70V, and acquisition was performed in positive mode. Results The yields of synthesized CPs were between 42.0-90.0%, which are higher values than literature[3]. These compounds are soluble in basic media (pH8.0), and dissolved in acidic media (pH3.0), a protonation is expected as well as an aggregation of monomers into PNTs. It was shown that their electrophoretic mobility (µep) was in accordance with their global charge and mass, but unexpected behaviors could be due to specific cyclic configurations of peptides, due to their sequence nature. Furthermore, MS evidenced the absence of corresponding linear, protected/partially deprotected peptides, and assemblies, in the analysis conditions, proving their purity. The effect of dissolution media on the µep (calculated according to[4]) was studied for CP-8 aaSerie3. This dissolved in basic conditions presents a µep of -4.31±0.11x10-5cm2.V-1.s-1, in agreement with negatively charged compounds. When modifying analysis conditions to acidic media, a shift in mobility was observed, leading 1.11±0.02x10-5cm2.V-1.s-1, indicating a protonation of monomers and possible self-assembly. While, CP dissolved in acidic conditions, the µep is positive (2.35±0.01x10-5cm2V-1s-1). When modifying analysis conditions to basic media, a negative value was determined (-2.94±0.3x10-5cm2V-1s-1). These results seem to indicate a self-assembly between CPs in acidic media, with different stages, as µep values are different according to pH modification pathway. To further in the interpretation, the MS signal of CP dissolved in acidic media was analyzed, showing a m/z value corresponding to twice molecular mass of monomer. This indicates a minima dimerization of CPs, and probably formation of PNTs. Conclusions We designed and synthesized eight new CPs that could provide PNTs of various properties. In view of aggregation as PNTs, their structure and purity had to be verified. Therefore, a new methodology based on CE-ESI-MS was set up. After optimizing various parameters, this methodology was demonstrated to be an innovative tool for easy and quick characterization of CP. When dissolved in acidic media, µep were drastically modified possibly due to aggregation phenomenon. These pure CPs will thus be interesting potential precursors for PNTs that could be employed as nanoplatforms in diagnostics or pseudo-sieving tools for separative purposes. [1] M. Girardot, et al., Anal.Biochem, 435, 150, (2013). [2] W. C. Chan, P. D. White, Fmoc solid phase peptide synthesis, (2000). [3] S. F. Brady, et al., JOC, 44, 3101, (1979) [4] A. Varenne, et. al., Anal.Biochem., 315, 152 (2003). Figure 1

Materials Engineering Using Nano-Fibrous and Molecular Cellulose

Cellulose is the most abundant natural polymer on earth, and widely used in everyday-life products from building construction to clothing to paper. Fundamental understanding of molecular solutions of cellulose is the key to realize advanced technologies beyond cellulose fibers. It has been previously reported that certain ionic liquid and organic solvent mixtures dissolve cellulose. In this study, the tertiary phase diagram of cotton linter microcrystalline cellulose, 1-Ethyl-3-methylimidazolium acetate (EMIMAc), and dimethylformamide (DMF) mixtures has been determined using primarily optical cloud point method and small angle neutron scattering (SANS). The mechanism of cellulose dissolution in tertiary mixture has been investigated by combining quasielastic and small angle neutron scattering (QENS and SANS). As SANS data show that cellulose chains take Gaussian-like conformations in homogenous solutions, which exhibit characteristics of having an upper critical solution temperature, the dynamic signals predominantly from EMIMAc molecules indicate strong association of EMIMAc with cellulose in the dissolute state. Data indicate that a molar ratio of EMIMAc to cellulose repeating unit greater or equal than 3 is necessary but not sufficient in forming one-phase homogeneous solutions. Clustering of cellulose chains occurs at low EMIMAc/DMF or EMIMAc/cellulose ratio, or at low temperatures. The mechanism of cellulose dissolution in tertiary mixture is discussed, and the potential applications of molecular cellulose are demonstrated.

Kinetics of Photocontrollable Micelles: Light-Induced Self-Assembly and Disassembly of Azobenzene-Based Surfactants Revealed by TR-SAXS.

The kinetics of micelles involving photosensitive surfactants is still not well understood. In this work, we unravel the mechanistic pathways involved in the micelle formation and dissolution of photocontrollable micelles. We focus on the fast self-assembly processes of photosensitive cationic azobenzene-containing surfactants (AzoTMA) that display a change in hydrophobicity induced by a reversible cis-trans conformational transition upon exposure to light. By combining both in situ time-resolved small-angle X-ray scattering (SAXS) and light scattering, we characterized the detailed structure and phase behavior of AzoTMA in mixtures of water and dimethylformamide (DMF). Time-resolved synchrotron SAXS with monochromatic light as a trigger enabled us to observe the nonequilibrium formation and dissolution process of micelles (demicellization) directly on the nanoscale with a time resolution starting from milliseconds. The structural results show that in pure water UV-light illumination leads to a 12% reduction of the aggregation number of the micelles and more than a 50% increase in the critical micelle concentration (CMC). Close to the CMC, adjusted by the addition of DMF, UV light illumination leads to a complete dissolution of the micelles, while shining blue light reverses the process and leads to the reformation of micelles. The UV-triggered dissolution follows a two-step mechanism; the first and rapid (second time scale) release of unimers is followed by a slower decomposition of the micelles (over tens of seconds) as a result of an increase in temperature due to optical absorption. Similarly, the reverse process, i.e., micelle formation, occurs rapidly upon photoconversion to trans conformers under blue light, and micelles are disrupted at long exposure time due to the optical absorption and corresponding increase in temperature. Interestingly, the coexistence of unimers with regular micelles is found at all times, and no other transient assemblies could be detected by SAXS.

59 LIPID DYNAMICS IN THE EARLY EMBRYONIC DEVELOPMENT OF ZEBRAFISH BY DESORPTION ELECTROSPRAY IONIZATION MASS SPECTROMETRY IMAGING AND NANOELECTROSPRAY–MASS SPECTROMETRY

This study introduces a combination of mass spectrometry-based analytical approaches with little or no sample preparation for the study of zebrafish (Danio rerio) lipid metabolism during early development (0 through 96 h post-fertilization, hpf). Desorption electrospray ionization mass spectrometry (DESI-MS) imaging and nanoelectrospray (nESI) MS were used. Embryos (N = 107) were placed onto filter paper squares and analysed by DESI-MS imaging. Embryos were arranged in rows with each one corresponding to a different developmental time, so that each DESI-MS image contained arrays of samples at different hpf. After completion of DESI-MS acquisition, the arrays were cut into strips of paper, isolating each embryo, which was subsequently inserted into a nESI tip and analysed. All experiments were performed using a linear ion trap mass spectrometer. DESI-MS images were acquired in the positive ion mode using acetonitrile doped with 10 ppm AgNO3, which allowed for the detection of cytosolic neutral lipids, such as cholesteryl esters (CE), diacylglicerols (DAG), triacylglycerols (TAG), squalene, and ubiquinone. For the nESI, experiments were run in full mass scan and MS/MS, in both negative and positive ion mode, using a mixture of dimethylformamide and acetonitrile to detect membrane phospholipids (e.g. phosphatidylcholines and phosphatidylglycerols). Principal component analysis was used to explore DESI-MS images and nESI data in an unsupervised fashion. The combination of DESI-MS imaging, providing chemical and spatial location, and nanoESI, providing a broader and more extensive structural information, showed that the lipid content changes dramatically over the first days of development. Accumulation of DAG and TAG, which are usually concentrated in the embryos yolk sac as an important storage for early development, were observed between 0 and 48 hpf. Embryos at the intermediate phase of development (24 hpf) were distributed between those of 0 and 48 hpf, reflecting the dynamics associated with development and might be correlated with TAG consumption and de novo synthesis. After 72 and 96 hpf, samples differed from prior developmental stages by the content of squalene, ubiquinone, and CE 22 : 5 (overexpressed), while the TAG content decreased. Further decrease of TAGs and ubiquinone occurred between 72 and 96 hpf. These observations indicated that zebrafish embryos rely entirely on the yolk sac for the nutrients needed to sustain growth and survival during the first four days of development. Yolk lipids are the likely source of TAGs, as well as cholesterol, a required component of cell membranes and a precursor for bile acids. The abundance of ubiquinone can be tied to zebrafish embryo growth, differentiation and organogenesis, and activation of mitochondria.

Synthesis and characterization of chiral copper(ii) coordination polymers with 4,4´-bipyridine and lactic acid derivatives

Chiral 2D and 3D metal-organic coordination polymers [Cu2(bpy)2(Hdml)2(HCOO)]-(HCOO)·2H2O (1) and [Cu(bpy)(Hphl)(HCOO)]·H2O (2) were synthesized by heating a solution of copper(ii) salts, 4,4´-bipyridine (bpy), and α-hydroxycarboxylic acids, viz., S-3,3-dimethyllactic (H2dml) or S-3-phenyllactic (H2phl) acid, in a water—N,N´-dimethylformamide mixture. The structures of compounds 1 and 2 were determined by single-crystal X-ray diffraction. Compound 2 was characterized by X-ray powder diffraction, IR spectroscopy, thermogravimetric analysis, and elemental analysis.