Improved solid-phase microextraction device for use in on-line immunoaffinity capillary electrophoresis

A simple solid-phase microextraction device was fabricated for use in on-line immunoaffinity capillary electrophoresis (CE). The device, designed in the form of a four-part cross-shaped or cruciform configuration, includes a large-bore tube to transport samples and washing buffers and a small-bore fused-silica capillary for separation of analytes. At the intersection of the transport and separation tubes, a small cavity was fabricated, termed the analyte concentrator-microreactor, which contains four porous walls or semipermeable membranes (one for each inlet and outlet of the tubes) permitting the confinement of beads or suitable microstructures. The surface of the beads in the analyte concentrator carried a molecular recognition adsorbing chemical or affinity ligand material. The improved cruciform configuration of the analyte concentrator-microreactor device, designed for use in on-line immunoaffinity CE, enables it to specifically trap, enrich, and elute an analyte from any biological fluid or tissue sample extract without any sample pretreatment except filtration, centrifugation, and/or dilution allowing the separation and characterization of target analyte(s) with improved speed, sensitivity, and lower cost than existing techniques. As a model system, Fab' fragments derived from a purified immunoglobulin G (IgG) antibody were covalently bound to controlled-porosity glass and used as constituents of the analyte-microreactor device. The high-specificity polyclonal antibodies employed in these experiments were individually raised against the acidic nonsteroidal anti-inflammatory drugs ibuprofen and naproxen, and the neuropeptides angiotensin II, and neurotensin. These compounds, which were present in simple and complex matrices were captured by and eluted from the analyte concentrator-microreactor using a 50 mM sodium tetraborate buffer solution, pH 9.0, followed by a 100 nL plug of 300 mM glycine buffer, pH 3.4. Two analyte concentrators were tested independently: one containing Fab' fragments derived from antibodies raised against ibuprofen and naproxen; the other containing Fab' fragments derived from antibodies raised against angiotensin II and neurotensin. Each resulting electropherogram demonstrated the presence of two eluted materials in less than 20 min. Immunoaffinity CE performed in a cruciform structure was simpler and faster than previously reported in the literature using on-line microextraction devices designed in a linear format. The new concentration-separation system operated consistently for many runs, maintaining reproducible migration times and peak areas for every analyte studied.     

Synthesis and ab-initio XRPD structure of group 12 imidazolato polymers

Two new 3D homoleptic binary imidazolates, Cd(im)2 and Hg(im)2 (Him = imidazole), as well as [Hg(im)]NO3, containing 1D polycations of [Hg(im)]n(n+) formulation, have been prepared and characterized by ab-initio XRPD methods.     

Fragmentation studies on monensin A and B by accurate-mass electrospray tandem mass spectrometry

Monensin A and B were studied by electrospray ionisation tandem mass spectrometry (ESI-MS/MS) and the fragment ions were confirmed by accurate-mass measurements. Analyses were performed on both a quadrupole time-of-flight (QTOF) and a Fourier-transform ion cyclotron resonance (FTICR) mass spectrometer. The analysis revealed that fragment ions were produced by Grob-Wharton fragmentations and pericyclic rearrangements in addition to various simple neutral losses. A study of the protonated and sodiated sodium salt revealed different fragmentation pathways for these species, thus complementary structural information could be gained. A complete fragmentation pathway of monensin A and B protonated sodium salt [(M-H+Na)+H])+) and sodiated sodium salt [(M-H+Na)+Na](+) is proposed. MS(3) analysis confirmed the separate fragmentation pathways.     

Biosurfactants production by Pseudomonas aeruginosa FR using palm oil

Biosurfactants production by a strain of Pseudomonas aeruginosa using palm oil as a sole carbon source was investigated. The experiments were carried out in 500-mL conical flasks containing 100 mL of mineral media supplemented with palm oil as the sole carbon source. The P. aeruginosa FR strain was able to reduce surface tension of three tested inorganic media. Rotation velocities from 100 to 150 rpm provided free-cell fermented media with the lowest surface tension of approx 33 mN/m. Emulsification index results of even 100% were achieved when diesel was used as oil phase. Eight surface-active compounds produced by the bacterium were identified by mass spectrometry.     

Panchromatic ruthenium sensitizer based on electron-rich heteroarylvinylene π-conjugated quaterpyridine for dye-sensitized solar cells

The first example of a heteroarylvinylene π-conjugated quaterpyridine Ru(II) sensitizer (N1044) was synthesized and used in dye-sensitized solar cells; the dye has an effective panchromatic absorption band, covering the entire visible spectrum up to the NIR region, and superior electrochemical characteristics (HOMO/LUMO and bandgap energies) with respect to previous representative Ru(II) bi- and quaterpyridine sensitizers. A record IPCE curve ranging from 360 to 920 nm has been measured with a maximum of 65% at 646 nm and still 33% efficiency at 800 nm; this leads to substantially increased photocurrent (19.2 mA cm(-2)) when compared to the prototype N719 Ru(II) sensitizer.     

Exo Diels–Alder adducts between ortho‐ and para‐N‐acetoxy­phenyl­male­imides and furan

In exo‐2‐(3,5‐dioxo‐10‐oxa‐4‐aza­tri­cyclo­[5.2.1.0^2,6]­dec‐8‐en‐4‐yl)­phenyl acetate, C₁₆H₁₃NO₅, the plane of the acetoxy group lies almost perpendicular to that of the phenyl ring [dihedral angle = 89.8 (1)°], in contrast with the smaller deviations found in the para isomer exo‐4‐(3,5‐dioxo‐10‐oxa‐4‐aza­tri­cyclo­[5.2.1.0^2,6]­dec‐8‐en‐4‐yl)­phenyl acetate, C₁₆H₁₃NO₅, these being 63.6 (1) and 37.0 (1)° for the two crystallographically independent mol­ecules. Irrespective of the position of the acetoxy group, both compounds pack through soft C—H⋯X (X is O or phenyl) interactions, forming interlinked centrosymmetric tetramers in the bc plane.     

A Flexible Pro‐porous Coordination Polymer: Non‐conventional Synthesis and Separation Properties Towards CO2/CH4 Mixtures

The novel coordination polymers [Cu(Hoxonic)(H₂O)]_n ( 1 ) and [Cu(Hoxonic)(bpy)_0.5]_n ? 1.5 n H₂O ( 2?H₂O ) (H₃oxonic: 4,6‐dihydroxy‐1,3,5‐triazine‐2‐carboxylic acid; bpy: 4,4′‐bipyridine) have been isolated and structurally characterised by ab initio X‐ray powder diffraction. The dense phase 1 contains 1D zig‐zag chains in which Hoxonic dianions bridge square‐pyramidal copper(II) ions, apically coordinated by water molecules. On the contrary, 2?H₂O , prepared by solution and solventless methods, is based on 2D layers of octahedral copper(II) ions bridged by Hoxonic ligands, further pillared by bpy spacers. The resulting pro‐porous 3D network possesses small hydrated cavities. The reactivity, thermal, magnetic and adsorptive properties of these materials have been investigated. Notably, the adsorption studies on 2 show that this material possesses unusual adsorption behaviour. Indeed, guest uptake is facilitated by increasing the thermal energy of both the guest and the framework. Thus, neither N₂ at 77 K nor CO₂ at 195 K are incorporated, and CH₄ is only minimally adsorbed at 273 K and high pressures (0.5 mmol g^?1 at 2500 kPa). By contrast, CO₂ is readily incorporated at 273 K (up to 2.5 mmol g^?1 at 2500 kPa). The selectivity of 2 towards CO₂ over CH₄ has been investigated by means of variable‐temperature zero coverage adsorption experiments and measurement of breakthrough curves of CO₂/CH₄ mixtures. The results show the highly selective incorporation of CO₂ in 2 , which can be rationalised on the basis of the framework flexibility and polar nature of its voids.     

Mechanism for basic hydrolysis of N-nitrosoguanidines in aqueous solution

A kinetic study was carried out on the hydrolysis of two N-nitrosoguanidines, 1-nitroso-1-methyl-3-tolylsulfonylguanidine (TSGNO) and 1-nitroso-1-methyl-3-benzoylguanidine (BCGNO). We observed an absence of buffer catalysis using H(2)PO(4)(-)/HPO(4)(2)(-), H(3)BO(3)/H(2)BO(3)(-), and HCO(3)(-)/CO(3)(2)(-) regulators and a complex dependency of the rate constant on the pH. We discovered the existence of three simultaneous reaction paths: spontaneous decomposition of the neutral form of the N-nitrosoguanidine, decomposition of the monoanion, and decomposition through the form of the dianion. The analysis of the kinetic data has allowed us to obtain the acidity constant for the formation of the monoanion of the N-nitrosoguanidine, with values of p = 11.5. The reaction rate for the process through the monoanion, k(2), decreases as the acidity increases. The application of the principle of nonperfect synchronization shows that the basicity and reactivity do not correlate when there exists a possibility of stabilization of the negative charge by resonance. This behavior is consistent with the mechanism E1cB whereby the stabler the negative charge, the slower the elimination reaction. When dealing with the case of the elimination through the neutral form we observe that the reaction rate increases together with the capacity of stabilization of the positive charge on the nitrogen atom adjacent to the imino group. For the reaction through the dianion we used a maximum value of k(3) = 10(10) s(-)(1) to estimate the value of p for the formation of the dianion of the N-nitrosoguanidine, obtaining values of p < 24.     

New butenolides in plantlets of Virola surinamensis (Myristicaceae)

A phytochemical investigation in plantlets of the Brazilian medicinal tree Virola surinamensis resulted in the isolation and structural determination of four new compounds: 3-hydroxy-4-methyl-2-(11'-piperonyl-n-undecyl)-butenolide; 3-hydroxy-4-methyl-2-(7'-piperonyl-n-heptyl)-butanolide; 9'-(3,4-methylenedioxy-phenyl)-nonanoic acid and 13'-(3,4-methylene-dioxyphenyl)-tridecanoic acid. Thirteen compounds previously isolated from seeds and adult plants were also reported.     

Electroreductive polymerization of trans-[RuCl 2(vpy) 4] on Nd-Fe-B magnets: electrochemical impedance spectroscopy interpretation, Raman spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy analysis

The electropolymerization of trans-[RuCl₂(vpy)₄] (vpy=4-vinylpyridine) monomer on Nd-Fe-B magnets was studied by electrochemical impedance spectroscopy (EIS). Impedance diagrams obtained during the polymerization process were used to monitor film formation. The EIS results gave insight into the electrochemical phenomena occurring at the magnet surface as the polymerization process progressed. The film structure and morphology were also studied by X-ray photoelectron spectroscopy, scanning electron microscopy and Raman spectroscopy. The Raman spectroscopy results showed that the polymerization takes place at the vinyl groups of the monomer and also that the redox polymer structure is very similar to that of the monomer. The ratio of the intensity of the XPS peaks for fluorine (from the electrolyte PF₆ ^–) and ruthenium present in the film showed that the polymer on Nd-Fe-B contained an equal proportion of Ru²⁺ and Ru³⁺, indicating that part of the film is positively charged, i.e. {[RuCl₂(vpy)₄]⁺} _n .