Studies of poly-<Emphasis Type="Italic">L</Emphasis>-lysine-starch nanoparticle preparation and its application as gene carrier

Anion starch nanoparticle (StNP) with a diameter of 50 nm was prepared in water-in-oil microemulsion, with soluble starch as raw materials and POCl₃ as crosslinking agent. PLL-StNP was prepared by linking poly-L-lysine (PLL) on the surface of StNP. At the same time, the size of PLL-StNP and its stability in aqueous solution were checked by AFM. The analysis of plasmid DNA binding, DNase I enzymatic degradation, toxicity and transfection were done. We discovered that PLL-StNP may be used as non-virus nanoparticle gene carrier. And we developed the method of preparing PLL-StNP gene carrier and used it in cell transfection. As non-virus gene carrier, PLL-StNP has some advantages, such as large load of DNA, high transfection efficiency, low cell toxicity and biodegradability.     

Phase Equilibria in the Ni–Al–W System at 900°C

Multicomponent Ni-base alloys exhibit good mechanical properties even at elevated temperatures and they are widely used for industrial production of exertion-resistive parts of engines. These properties are mainly determined by the coexistence of a disordered γ matrix with a face centred cubic lattice and cuboidal domains of its ordered γ′ structure. Therefore it is useful to study phase equilibria in Ni-base systems, namely in the regions involving both mentioned phases. One of the conclusions of our recent work on Ni–Al–Cr–W system was a necessity of modification of selected thermodynamic parameters of the ternary Ni–Al–W subsystem in order to achieve a better agreement of our experimental observations with theoretical modelling. This involves new measurements of the microstructure of selected samples of the Ni–Al–W system at 900°C and the comparison of the results with existing literature data in order to confirm our conclusions on higher order system investigated before. It is a first step on the way to an assessment of the Ni–Al–W system, which has not been done before.     

Pitzer model parameters for sparingly soluble salts from solubility measurements. The systems TlCl+SrCl2+H2O and TlCl+BaCl2+H2O at 25°C

The solubility of thallium(I) chloride has been determined in aqueous solutions of strontium chloride and barium chloride at concentrations up to 1.5 mol kg^–1. The data were analyzed using Pitzer's equations without making explicit assumption of association to ion pairs by assuming =3 instead of =2, with the ⁽¹⁾ term for TlCl being equivalent to the ⁽²⁾ term for 2-2 electrolytes. Best values of ⁽⁰⁾ and ⁽¹⁾ for TlCl are recommended together with K _s , the activity solubility product. These were used to fit the present solubility data and derive the Pitzer model mixture parameters relevant to the systems, _fTIN and _fTINCl (N=Sr, Ba). Mixture parameters for TlCl+MCl+H₂O systems are also derived to complete the parameter base. The fit of the experimental data was found to be worse when higher-order terms for asymmetrical mixing were included in the analysis. Activity coefficients for thallium(I) chloride in the mixtures are derived.     

MODULATION OF 8-METHOXYPSORALEN-DNA PHOTOADDUCT FORMATION BY CELL DIFFERENTIATION, MITOGENIC STIMULATION AND PHORBOL ESTER EXPOSURE IN MURINE T LYMPHOCYTES

Abstract The effects of cell differentiation and mitogen and phorbol ester stimulation on the formation of 8-methoxypsoralen (8-MOP)-DNA photoadducts in murine T lymphocytes were examined using ³H-8-MOP. While there were no significant differences in 8-MOP photoadduct formation among BALB/c thymocytes, splenocytes, splenic T cells and MRL/1pr lymph node cells, BALB/c bone marrow cells showed fewer photoadducts than did the lymphocytes. This suggested that proliferating progenitor cells may be resistant to 8-MOP photoadduct formation. Incubation of purified splenic T cells with lectin mitogens for 2 h or with phorbol 12-myristate 13-acetate (PMA) for 2–43 h resulted in reduction of 8-MOP photoadduct formation in the DNA, whereas 64 h cultivation with these agents augmented the photoadduct formation. The reduction of photoadduct formation induced by phytohemagglutinin was restored by the further addition of a protein kinase C (PKC) inhibitor, H-7, to the culture. Thus, it is assumed that the reduction of adduct formation evoked by mitogens and PMA is mediated in part by the activation of PKC in the cells. On the other hand, the augmentation of the adduct formation induced by the longer-period cultures with mitogens and PMA appeared to be caused by down-regulation of PKC. The present study showed that the stimulatory signals in which PKC is presumably involved affect the ability of cells to form 8-MOP-DNA photoadducts.     

Studies of amine-induced ring opening of some mesoionic xanthines

The ring-opening reactions of seven mesoionic thiazolo[3,2-a]pyrimidine-5,7-diones by a series of primary and secondary amines have been investigated. The rates of the ring fission of five N(8)-substituted mesoionic xanthines with benzylamine were measured and found to follow second order kinetics. The Hammett relationship is followed with ? value of + 0.48 in p-dioxane as solvent. The dependence of rates on temperatures has been studied for the N(8)-ethyl derivative; the energy of activation (Δ E* ) is 25.3 kcals mol^?1, the enthalpy of activation (Δ H* ) is 24.7 kcals mol^?1 and the entropy of activation (Δ S* ) is — 4.9 e.u. A slight increase in rate of reaction was observed when the solvent was changed from p-dioxane to dimethyl sulfoxide. In p-dioxane at constant mesoionic xanthine concentration, the rate constant for ring opening decreased with increasing benzylamine concentration. These results are consistent with a bimolecular nucleophilic mechanism proceeding by the rate-determining formation of a charged tetrahedral transition state.     

Indirect Determination of Sulfide by Cold Vapor Atomic Absorption Spectrometry

A method for the determination of sulfide based on its interference with the determination of Hg by cold vapor atomic absorption spectrometry is described. The decrease in mercury absorbance at 253.7nm is proportional to the concentration of sulfide over the range of 10–320ngmL^–1. The limit of detection was found to be 7ngmL^–1 and the relative standard deviation (R.S.D.) for the determination of different concentrations of sulfide was in the range of 1.8–2.2%. This method was applied to the determination of sulfide in whole human blood after gas-phase separation.     

Low-temperature electrothermal vaporization of thenoyltrifluoroacetone complex of Sc(III) and Y(III) for sample introduction in an inductively coupled plasma atomic emission spectrometry,and their determination in biological samples

A new method for inductively coupled plasma atomic emission spectrometry (ICP-AES) determination of trace Sc and Y, based on gaseous compound introduction into the plasma as their thenoyltrifluoroacetone (TTA) complexes by electrothermal vaporization was developed. Using the reagent TTA as chemical modifier can not only enhance the analytical signals, but also reduce the vaporization temperature. At a temperature of 1,000 °C the trace Sc and Y can be vaporized completely into ICP. The factors affecting the formation of the chelate and its vaporization behavior, such as drying time, vaporization temperature/time, reaction medium and the amount of TTA, were investigated in detail. Under the optimized conditions (drying temperature/time 100 °C/10 s, vaporization temperature/time 1,000 °C/4 s), the limits of detection for Sc and Y were 19 pg and 34 pg (3), respectively, and the relative standard deviations for Sc and Y were 4.2% (c _Sc=0.2 g mL^–1; n=7) and 2.6% (c _Y=0.5 g mL^–1; n=7). The linear ranges of the calibration graphs cover three orders of magnitude. The method was applied to the analysis of the biological reference materials (GBW 07602, bush branches and leaves; GBW 07604, poplar leaves), and the results obtained were in good agreement with the certified values.     

Microcalorimetry as a possible tool for phenanthrene toxicity evaluation to eukaryotic cells

Microcalorimetry and measurement of culture turbidity using a Bioscreen C Analyzer System were applied to study the toxic effect of phenanthrene on Cunninghamella elegans IM 1785/21Gp spore germination. The results of C. elegans spore incubation in Bioscreen C microbiology reader showed the inhibition of spore germination by 70% (with 25 mg l⁻¹ of phenanthrene) and total inhibition of the fungus growth with a higher content of the xenobiotic (50-100 mg l⁻¹). The microcalorimetric technique showed to be useful for the estimation of metabolic activity of C. elegans spores in growth medium up to xenobiotic concentrations of 90 mg l⁻¹. These data corresponded with the microscopic observations. The obtained results showed that the microcalorimetry method could be a valuable supplement in the study on the mechanism of PAHs detoxification by fungi.     

R12 hydrate formation kinetics based on laser light scattering technique

Gas hydrates are non-stoichiometric crystalline compounds of water with gas at a certain temperature and pressure. Compared to the thermodynamics of hydrate formation, our knowledge on the kinetics aspect is rather immature. It is well known that the kinetics of hydrate formation/dissociation plays an important role in many industrial cases, such as the exploitation of methane hydrate underground, the storage and transportation of natural gas in solid hydrate state, the inhibition of hydrate i…     

N,N-difluorotris(tert-butyl)silylamine-the first organosilyl difluoroamine. Synthesis and computational studies

The synthesis and characterization of the first stable trialkyl(difluoroamino)silane, R3SiNF2, as well as of R3SiNHF and R3SiN(CH3)F in moderate yields are reported. The (difluoroamino)silane has promise as a new synthon for the introduction of the -NF2 group into a variety of electrophilic inorganic and organic substrates. Activation barriers and relative energies were calculated for the unimolecular decompositions of Me3SiCF3 and t-Bu3SiNF2 using density functional theory (B3LYP/6-31G). The calculated activation energies confirm the long-assumed kinetic stability of Me3SiCF3.