Electroporation and fusion modified by nucleic acids and complexes

The study of biopolymer modified electrofusion has been extended to nucleosides, nucleotides, polynucleotides, nucleic acids and their complexes with positively charged ligands (Ca²⁺, La³⁺, ethydiumbromid, daunomycin, poly-l-lysine, histone). Whereas the mononucleotides show different effects on the electrofusion of barley protoplasts, the behaviour of the polymers are quite similar: at low concentrations the electrofusion was enhanced remarkably and at higher concentrations (>0.05 mg ml⁻¹) an inhibition effect was detected. Shielding the negative charge of phosphate groups the DNA complexes increase F_r values to some extend. Quite strong enhancement of F_r was also measured with nucleoproteins, e.g., nucleohistone. The essential process is the interaction between the polymers and the negatively charged protoplast membrane. This interaction was compared with the adsorption behavior of these polymers on the negative mercury electrode surface which can serve as a model for a `half membrane'. With these results a first system of `biopolymer modified electrofusion' is now available.     

Polylysine supports electrofusion

A series of poly-l-lysine fractions (mean molecular masses M_m from 3970 to 132 300) at extremely low concentrations in the nanomolar range were combined with dielectrophoresis and rectangular pulsation of barley protoplasts in order to support electrofusion of membranes. Contrary to our results with dextran fractions, the poly-l-lysine fractions of high molecular masses M_m promote the synergistic effect of polymer-supported electrofusion yield more than two times. The M_m dependence of adsorption at the dropping mercury electrode is analogous to that of dextran; however, instead of a Langmuir(-Freundlich) isotherm a Frumkin type was found, because of intermolecular interaction in the adsorption layer. Therefore the adsorption mechanisms for the two biopolymers are contradictory in this respect. Again it was shown that such electrofusion experiments provide a sensitive test for two kinds of interactions between biopolymers and membranes. Moreover, the practical advantage for moderate electrofusion is the following: in presence of 10 μg ml⁻¹ (= 10^−3%) poly-l-lysine (M_m, 26300) the electrofusion yield (F_r=2.2) is the same as in polymer-free treatment with only one pulse, which must be 250 V cm⁻¹ higher. Finally, some possible mechanisms are proposed.     

Measurement and explanation of the d-d transition spectra of [Cu(o-phen)(ox) · H2O] · H2O

Aqua (1-10-phenanthroline)-(oxalato-O′O″) copper(II) monohydrate crystals have been prepared and characterized by elemental analysis, thermal analysis, infrared and electronic absorption spectrum, the later involves a strong absorption band appearing at 15 560 cm⁻¹. The experimental results are discussed quantitatively using the ligand field theory (LFT) and radial wave function of non-free copper(II). The values of <r²>, <r⁴>, <r⁻³>, B, C and ζ_3d were calculated in the light of the crystal structure. The energy level of the title crystal was interpreted comprehensively. All of our research indicates that the mixed complex of o-phen and ox exists in two forms, as reported by P. O'Brien, C. Stafford and Cheng Young, Inorg. Chim. Acta 147, 3 (1988) [1].     

Calorimetric investigation of the effect of hydroxyanthraquinones in Rheum officinale Baill on Staphylococcus aureus growth

The inhibitory effects of five hydroxyanthraquinones (HAQs) from root and rhizoma of Rheum officinale Baill, a traditional Chinese medicinal (TCM) herb, on Staphylococcus aureus growth were investigated by calorimetry. The power-time curves of S.aureus with and without HAQ were acquired and the extent and duration of inhibitory effects on the metabolism evaluated by growth rate constants (k₁, k₂), half inhibitory ratio (IC₅₀), maximum heat output (P_max) and peak time (t_p). The value of k₁ and k₂ of S. aureus in the presence of the five HAQs decreased with the increasing concentrations of HAQs. Moreover, P_max was reduced and the value of t_p increased with increasing concentrations of the five drugs. The inhibitory activity varied for different drugs. IC₅₀ of the five HAQs was 4 μg ml⁻¹ for emodin, 3.5 μg ml⁻¹ for rhein, 10 μg ml⁻¹ for aloe-emodin, 1000 μg ml⁻¹ for chrysophanol, 1600 μg ml⁻¹ for physcion. The sequence of antimicrobial activity of the five HAQs: rhein > emodin > aloe-emodin > chrysophanol > physicion.     

Experimental and theoretical studies of the topological and energy parameters in the crystal of 4,7-di-tert-butyl-2-phenyl-1,3,2-benzodioxaborole

The electron density distribution in the crystal of 4,7-di-tert-butyl-2-phenyl-1,3,2-benzodioxaborole (1) was examined both experimentally and theoretically. According to the theory “Atoms in Molecules”, the B-O bonds are “intermediate” interactions (?²γ(r) > 0, h _e(r) < 0), while the B-C(Ph), O-C, and C-C bonds are “shared” (?²γ(r) < 0, h _e(r) < 0). The energies of intra- and intermolecular interactions in the crystals were estimated. Compound 1 is inert to oxygen, which agrees with the low HOMO energy (?6.26 eV).     

Analytical Hartree-Fock electron densities for singly charged cations and anions

The Hartree-Fock (HF) electron density has an important property that it is identical to the unknown exact density to the first order in the perturbation theory. We generate the spherically averaged HF electron density ρ(r) by using the numerical HF method for the singly charged 53 cations from Li⁺ to Cs⁺ and 43 anions from H⁻ to I⁻ in their ground state. The resultant density is then accurately fitted into an analytical function F(r), which is expressed by a linear combination of basis functions r ⁿⁱ exp(−ζ _i r). The present analytical approximation F(r) has the following properties: (1) F(r) is nonnegative, (2) F(r) is normalized, (3) F(r) reproduces the HF moments <r ^k > (k=−2 to +6), (4) F(0) is equal to ρ(0), (5) F ^′(0) satisfies the cusp condition and (6) F(r) has the correct exponential decay in the long-range asymptotic region. The present results together with our previous ones for neutral atoms provide a compilation of accurate analytical approximations of the HF electron densities for all the neutral and singly charged atoms with the number of electrons N≤54. Received: 11 July 1997 / Accepted: 27 August 1997     

Diffusion coefficient for model potentials through mean square displacement

The Chakrabarti velocity autocorrelation function has been used in the evaluation of the mean square displacement <r²(t)> of liquid argon and sodium for hard sphere and square well model potentials. The <r²(t) > plots become linear in the long time limit, yielding diffusion coefficients in agreement with experiment.     

Effect of post-deposition annealing temperature on RF-sputtered HfO2 thin film for advanced CMOS technology

Structural and electrical properties of HfO₂ gate-dielectric metal-oxide-semiconductor (MOS) capacitors deposited by sputtering are investigated. The HfO₂ high-k thin films have been deposited on p-type <100> silicon wafer using RF-Magnetron sputtering technique. The Ellipsometric, FTIR and AFM characterizations have been done. The thickness of the as deposited film is measured to be 35.38 nm. Post deposition annealing in N₂ ambient is carried out at 350, 550, 750 °C. The chemical bonding and surface morphology of the film is verified using FTIR and AFM respectively. The structural characterization confirmed that the thin film was free of physical defects and root mean square surface roughness decreased as the annealing temperature increased. The smooth surface HfO₂ thin films were used for Al/HfO₂/p-Si MOS structures fabrication. The fabricated Al/HfO₂/p-Si structure had been used for extracting electrical properties such as dielectric constant, EOT, interface trap density and leakage current density through capacitance voltage and current voltage measurements. The interface state density extracted from the G–V measurement using Hill Coleman method. Sample annealed at 750 °C showed the lowest interface trap density (3.48 × 10¹¹ eV⁻¹ cm⁻²), effective oxide charge (1.33 × 10¹² cm⁻²) and low leakage current density (3.39 × 10⁻⁹ A cm⁻²) at 1.5 V.     

Synthesis,structure, and bonding of the hexagonal form of the oxide carbide ScAlOC

Red single crystals of a hexagonal form of ScAlOC were obtained as a by-product from the synthesis of ScAl₃C₃ by reacting scandium and carbon in an aluminium melt at 1820 °C. The crystal structure (hP8, space group P6₃mc, Z = 2, a = 3.24793(3) Å, c = 10.1739(1) Å, 629 refl., 15 param., R₁(F) = 0.010, wR₂(F²) = 0.023) can directly be derived from the binary nitrides AlN and ScN or the oxide carbides Sc(O,C) and Al(O,C), respectively. ScAlOC-II or h-ScAlOC represents a new structure type with simple closest packing of alternating layers of oxygen and carbon. The stacking sequence is ABAC (=(hc)₂) with oxygen in a cubic and carbon in a hexagonal sequence. According to the difference in size Sc occupies octahedral voids between every second layer leading to layers of edge-sharing ScO₃C₃ octahedra. Aluminium is located in half of the tetrahedral voids. The AlOC₃-tetrahedra are connected to layers by common corners of the carbon atoms. h-ScAlOC continues the row of the rare examples of oxide carbides with ordered anion distribution. Band structure calculations by FP-(L)APW methods revealed that ScAlOC is electron precise with a band gap of 1.2 eV. Calculations of charges by the Bader-method reveal values of Sc^+1.87, Al^+2.33, O^−1.52 and C^−2.67. Together with the charge densities and the values of the Laplacian this stands for a mainly ionic bonding containing significant covalent contributions, too. Despite the close similarity to rhombohedral ScAlOC (r-ScAlOC) there is a striking difference in colour, as r-ScAlOC is black. This is confirmed and explained by the results of the P-DOS, because the lowest states of the conduction band are determined by Sc-d-states. These are significantly lower in r-ScAlOC with ScC₆ and ScO₆ octahedra than in h-ScAlOC leading to a calculated band gap of 0.3 eV.     

Magnetic properties of MoS2 nanotubes doped with lithium

DC magnetization measurements of lithium-doped molybdenum sulfide nanotubes (Li_xMoS₂, 2.2<x<2.5) reveal a very large, nearly linear temperature-dependent susceptibility. The susceptibility in the temperature interval from 300 to 2 K is more than 10⁻² emu mol⁻¹, which is more than 100 times larger than the susceptibility of Li metal. The M(H) curves (0 kOe≤H≤50 kOe) measured at several temperatures between 2 and 300 K show a very small temperature dependence. Besides the linear part of M(H) for H>10 kOe, the nonlinear part in H<5 kOe with saturation at approximately 10 kOe can be observed. This suggests a formation of ferromagnetic clusters even at room temperature. No magnetic phase transition between 2 and 300 K has been detected.     

Achieving high electrode specific capacitance with materials of low mass specific capacitance: Potentiostatically grown thick micro-nanoporous PEDOT films

Electrode materials for supercapacitors are at present commonly evaluated and selected by their mass specific capacitance (C_M, F g⁻¹). However, using only this parameter may be a misleading practice because the electrode capacitance also depends on kinetics, and may not increase simply by increasing material mass. It is therefore important to complement C_M by the practically accessible electrode specific capacitance (C_E, F cm⁻²) in material selection. Poly[3,4-ethylene-dioxythiophene] (PEDOT) has a mass specific capacitance lower than other common conducting polymers, e.g. polyaniline. However, as demonstrated in this communication, this polymer can be potentiostatically grown to very thick films (up to 0.5 mm) that were porous at both micro- and nanometer scales. Measured by both cyclic voltammetry and electrochemical impedance spectrometry, these thick PEDOT films exhibited electrode specific capacitance (C_E, F cm⁻²) increasing linearly with the film deposition charge, approaching 5 F cm⁻², which is currently the highest amongst all reported materials.     

Determination of urinary methylhippuric acids using MIL-53-NH2 (Al) metal–organic framework in microextraction by packed sorbent followed by HPLC–UV analysis

For the analysis of methylhippuric acids (MHAs) in human urine samples, in this study, a new method based on the metal–organic framework (MOF) of MIL-53-NH₂ (Al) in microextraction by packed sorbent (MEPS) was developed. The synthesis of MIL-53-NH₂ (Al) was characterized by Fourier transform infrared spectra, field emission-scanning electron microscopy and X-ray diffraction. Response surface methodology was used to investigate the influences of several parameters including type and volume of elution, type of conditional solvent, sample volume and extraction cycle on MEPS efficiency. The results showed good recoveries (>94%) and excellent extraction efficiencies (>96%) at three different concentrations of 50, 500 and 1500 μg ml⁻¹ (as low, mid and high concentrations, respectively) of MHA isomers. Calibration curves of MHAs were linear over the concentration range of 1–1500 μg ml⁻¹, with high correlation coefficients (r ≥ 0.998). The reproducibility of the proposed MIL-53-MEPS for determination of three isomers of MHA was found to be in the range of 3.5–11.1%. After optimization of the proposed technique, it was used to analyze MHAs in urine samples of workers exposed to xylenes in a petrochemical plant in Asalouyah, Iran. The results indicated that the MOF–MEPS method was selective, sensitive, rapid and efficient for the extraction of urinary MHAs. The technique is also environmentally friendly and inexpensive, and the MOF sorbent is reusable.     

Direct determination of kanamycin in raw materials, veterinary formulation and culture media using a novel liquid chromatography-evaporative light scattering method

A novel method for the direct determination of kanamycin A and its minor component kanamycin B was developed and validated based on reversed phase liquid chromatography with evaporative light scattering detector (ELSD). ELSD response to kanamycins was found to be enhanced by: (a) decrease of peak width and asymmetry (obtained by controlling the mobile phase acidity or ratio of organic solvent to water), (b) use of ion-pairing acidic reagents of increased molecular mass, and (c) increase of mobile phase volatility. Utilizing an Spherisorb ODS-2 C₁₈ column, the selected optimized mobile phase was water-acetonitrile (60:40, v/v), containing 11.6 mM heptafluorobutyric acid (isocratic elution with flow rate of 1.0 ml min⁻¹). Kanamycin A was eluted at 3.9 min and kanamycin B at 5.0 min with a resolution of 2.7. Logarithmic calibration curves were obtained from 0.6 to 28 μg ml⁻¹ (r > 0.9998) for kanamycin A and 4-36 μg ml⁻¹ (r > 0.9994) for kanamycin B, with a LOD equal to 0.20 and 1.4 μg ml⁻¹, respectively.In kanamycin acid sulfate pharmaceutical raw materials, the simultaneous determination of sulfate (t_R = 2.1 min, LOD = 2.3 μg ml⁻¹, %R.S.D. = 1.7, r > 0.9998) and kanamycins was feasible. No significant difference (t-test) was found between the results of the developed LC-ELSD method and those of reference methods, while recovery from kanamycin B spiked samples ranged from 95 to 105%. The developed method was also applied with very good accuracy for the determination of kanamycin A in veterinary formulation (%recovery 95-103, %R.S.D. < 1.4, n = 3) and for the determination of kanamycins A and B in bacteria culture media (%recovery 102 and 99, respectively).     

Crystal and molecular structure of (η3-allyl)carbonylchlorobis(dimethylphenylphosphine)- iridium(III) hexafluorophosphate, [Ir(η3-C3H5)Cl(CO)(P(CH3)2(C6H5))2][PF6

The structure of (η³-allyl)carbonylchlorobis(dimethylphenylphosphine)-iridium(III) hexafluorophosphate, [Ir(η³-C₃H₅)Cl(CO)(P(CH₃)₂(C₆H₅))₂][PF₆], has been determined from three-dimensional X-ray data to add support for a proposed mechanism of the oxidative addition of allyl halides to IrX(CO)(PR₃)₂ (X = halide). The compound crystallizes in space group C⁵_2h-P2₁/c with four formula units in a cell of dimensions a = 11.027(1), b = 12.230(2), c = 19.447(5) Å, and β = 103.16(2)⁰. Least-squares refinement of the structure has led to a value of the conventional R index (on F) of 0.066 for the 3018 independent reflections having F²₀>3—(F²₀). The crystal structure consists of discrete, monomericions. The hexafluorophosphate anion is disordered. The coordination geometry around the iridium atom may be described as octahedral, with the chloro ligand trans to the carbonyl group and each phosphorus atom trans to a terminal carbon of the allyl group. Structural parameters: Ir—P = 2.366(4), 2.347(3);Ir—Cl = 2.389(3); Ir—C(allyl) = 2.28(1), 2.24(1),2.25(1); Ir—C (carbonyl) = 1.85(1) Å; P—Ir—P = 105.7(1); C(terminal)—Ir—C(terminal) = 66.2(8); C—C—C = 125(2)^o. The allyl group makes an angle of 126^o with the P—Ir—P plane. Correlations between geometric structure and number of d electrons are noted among several M—C₃H₅-complexes, and are interpreted in the light of theoretical models of the M—C₃H₅- bond.     

Bithiophene triarylborane dyad: An efficient material for the selective detection of CN− and F− ions

A new fluorescent chemosensor based on bithiophene coupled dimesitylborane (BMB-1) was synthesized and characterized. BMB-1 was used for colorimetric and turn-on fluorescent sensing of cyanide (CN⁻) and fluoride (F⁻) ions, in the presence of other competitive anions in an aqueous (CH₃CN–H₂O) medium. BMB-1 showed a hypsochromic shift (blue shift) with addition of CN⁻ and F⁻ ions in absorption studies. The lower detection level of CN⁻ and F⁻ ions is 1.37 × 10⁻⁹ and 1.75 × 10⁻⁹ M, respectively. The BMB-1 binding mechanism is based on the nucleophilic addition of CN⁻ and F⁻ ions in the internal charge transfer transition of bithio moiety to the boranylmesitylene unit, and the color changes were observed under UV light. This result is further confirmed by Fourier transform infrared spectroscopy, mass spectrometry and density functional theory calculations. Also, the BMB-1 probe is found to be a good adsorbent for the removal of F⁻ ions in real water samples using the adsorption technique.     

Anodic waves of 9,10-phenanthrenequinone in alkaline media

9,10-Phenanthrenequinone yields at pH > 11 anodic waves, which correspond to a formation of a slightly soluble salt of mercury formed in the reaction of Hg₂²⁺ with the product of a reaction of the quinone with two OH⁻ ions. Anodic waves are a linear function of phenanthrenequinone concentration up to about 1 × 10⁻⁴M and are affected by adsorption at higher concentrations. The concentration limit depends on the cosolvent used and decreases in the sequence MeOH > EtOH > n-PrOH. At given concentrations of phenanthrenequinone and of OH⁻ ions the anodic current decreases with increasing alcohol concentration.     

O-atom transfer biomimetic oxidation of benzoin in the presence of monooxomolybdenum(IV) thiolate complexes

Novel catalytically active monooxomolybdenum(IV) species containing four thiolate ligands obtainable in solution by NaBH₄ reduction of [Mo^vO(SC₆H₅)₄]⁻, [Mo^vO(Z-cys-Val-OMe)₄]⁻, (Z=benzyloxycarbonyl), or [Mo^vO(S₂C₆H₄)₂]⁻ perform the pyridine-N-oxide oxidation of benzoin in N,N-dimethylformamide at 30 °C. The order of catalytic activity is [Mo^vO(Z-cys-Val-OMe)₄]⁻ > [Mo^vO(S₂C₆H₄)₂]⁻ > [Mo^vO(SC₆H₅)₄]⁻ ([benzoin]/[oxidant]/[catalyst]= 20/20/1), while the oxidation by air under the same catalytic conditions gives a different order, [Mo^vO(Z-cys-Val-OMe)₄]⁻> [Mo^vO(SC₆H₅)₄]⁻ >[Mo^vO(S₂C₆H₄)₂]⁻. During the catalytic cycle in the amine-N-oxide oxidation, two intermediate species, [Mo^IVOL₄]²⁻ and [Mo^VIO₂L₄]²⁻, were detected by ¹H NMR, while in the air oxidation an unidentified Mo(VT) species is involved.     

Determination of the carboxylic acid metabolite of clopidogrel in human plasma by liquid chromatography-electrospray ionization mass spectrometry

A rapid and specific liquid chromatographic-mass spectrometric method has been developed and validated for the determination of the carboxylic acid metabolite of clopidogrel in human plasma. Sulphafurazole was used as internal standard. The samples were subjected to a solid phase extraction procedure using Hypercarb cartridges. The chromatographic separation was performed on a reversed phase porous graphitized carbon column using a mobile phase consisting of 70% methanol in water containing 0.1% (v/v) trifluoroacetic acid, pumped at a flow rate of 0.25 ml min⁻¹. The analytes were detected after positive electrospray ionization using the selected ion monitoring mode of the species at m/z 308 for the carboxylic acid metabolite of clopidogrel, m/z 322 for clopidogrel and m/z 268 for sulphafurazole. Calibration graphs were linear (r>0.9994, n=6), in the range 100-1000 ng ml⁻¹ for the carboxylic acid metabolite of clopidogrel. The intra- and inter-day R.S.D. values were <3.1%, while the relative error E_r was less than −9.6% (n=6). The limits of detection (3.3σ) and quantitation (10σ) for the carboxylic acid metabolite of clopidogrel were found to be 28 and 93 ng ml⁻¹, respectively. The efficiency of the solid phase extraction procedure for the carboxylic acid metabolite of clopidogrel averaged 74.6%.