Complexation of well-controlled low-molecular weight polyelectrolytes with antisense oligonucleotides

The influences of polymer-related properties such as molecular weight, charge density, counter ion, and hydrophilic block on the complexation of polyelectrolytes and a fluorescein-labeled oligonucleotide (ON) were investigated. A series of well-defined and well-controlled 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) polymers and block copolymers were prepared using living anionic and radical polymerization methods. Fluorescence measurement was used to reveal the effects of polymer molecular weight, charge density, and counter ion type on the complexation. PolyDMAEMA samples having double molecular weights of the chosen oligonucleotide gave the optimal complexation performance. Kinetic studies showed that high-molecular weight/high-charge density polymer samples produced very stable complexes. The fully charged polyDMAEMA displayed the strongest binding with the ON. These complexes were therefore less sensitive to the changes in the environment. PolyDMAEMA–DMSQ samples had slightly higher complexation ability than polyDMAEMA–MCQ (DMSQ: dimethylsulfate quat; MCQ: methylchloride quat). Both poly(DMAEMA-b-HEMA) and poly(DMAEMA–MCQ-b-PEG) block copolymers showed good complexation ability and steric stability [HEMA: 2-hydroxyethyl methacrylate; PEG: poly(ethylene glycol)]. PEG, but not HEMA block, enhanced the effectiveness of polyDMAEMA–MCQ binding with the ON.     

Copper(I) hexafluoroantimonate - an example of a compound with Cu in a solely fluorine environment

Yellow-orange single crystals of CuSbF₆, were prepared by reacting Cu wire (∼10 mmol) with SbF₅ (∼3 mmol) in liquid anhydrous hydrogen fluoride (aHF) and by reduction of Cu(SbF₆)₂ with Cu metal in aHF. CuSbF₆ crystallizes rhombohedral at 296 K with the LiSbF₆ structure type, with a = 530.4(4) pm, c = 1453(1) pm and Z = 3, space group R (no. 148). The structure is dominated by isolated layers of regular [SbF₆]⁻ octahedra and Cu⁺ cations.An attempt to prepare CuF by reaction between CuSbF₆ and CsF in aHF at ∼190 K failed. Instead of CuF, a mixture of Cu and CuF₂ was obtained.     

Nanostructure evolution studies of bulk polymer materials with synchrotron radiation: progress in method development

The prospects of a modern analysis of nanostructure evolution during the processing of polymer materials by means of scattering from synchrotron radiation are demonstrated in examples. The beam sources have gained stability, shortages are located in beamline setups and in method development for the quantitative analysis of voluminous data sets.By using the proposed multidimensional chord distribution function (CDF) analysis method, nanostructure information from small-angle X-ray scattering (SAXS) data are extracted and visualised. The method can be automated if the beamline setup is able to deliver a full data set with simple constraints. In this case even a simultaneous data evaluation is possible (while one pattern is accumulated, the previous one is analysed). The advantages of the method are demonstrated in a study of the straining of a thermoplastic elastomer. The possibilities of an automated analysis are demonstrated in an investigation of the crystallisation behaviour of high-pressure injection-moulded polyethylene (HPIM-PE). The achievable results of nanostructure analysis of polymer materials are discussed. It is shown that the time-resolved SAXS of polymer materials studied during a transformation and analysed by the CDF method is not just a powerful tool to investigate the relationship between structure and properties of materials; the information that can be gained concerning the processes that control nanostructure evolution is equally important. In the future the enlightenment of such relationships may help to tailor polymer materials with respect to their properties and, beyond that, to improve assessments concerning their aging.     

Development and validation of an analytical method for detection of estrogens in water

An analytical procedure enabling routine analysis of four environmental estrogens at concentrations below 1 ng L^–1 in estuarine water samples has been developed and validated. The method includes extraction of water samples using solid-phase extraction discs and detection by gas chromatography (GC) with tandem mass spectrometry (MS–MS) in electron-impact (EI) mode. The targeted estrogens included 17- and 17-estradiol (aE2, bE2), estrone (E1), and 17-ethinylestradiol (EE2), all known environmental endocrine disruptors. Method performance characteristics, for example trueness, recovery, calibration, precision, accuracy, limit of quantification (LOQ), and the stability of the compounds are presented for each of the selected estrogens. Application of the procedure to water samples from the Scheldt estuary (Belgium – The Netherlands), a polluted estuary with reported incidences of environmental endocrine disruption, revealed that E1 was detected most frequently at concentrations up to 7 ng L^–1. aE2 was detected once only and concentrations of bE2 and EE2 were below the LOQ.Presented at the 9th FECS Conference on Chemistry and the Environment, Bordeaux, France, 29 August–1 September 2004     

Thermostability of landscape phage probes

Immunoassays have traditionally relied on antibodies as diagnostic probes. Their use outside of a laboratory, however, may be problematic because antibodies are often unstable in severe environmental conditions. Environmental monitoring requires thermostable probes, such as landscape phage, that carry thousands of foreign peptides on their surfaces, are superior to antibodies, and can operate in non-controlled conditions. While parent wild-type phage are known to be extremely stable in various media at high temperatures, no work has been done to demonstrate the stability of landscape phage probes. We examined the thermostability of a landscape phage probe and a monoclonal antibody specific for -galactosidase in parallel in an enzyme-linked immunosorbent assay (ELISA) format. They were both stable for greater than six months at room temperature, but at higher temperatures the antibody degraded more rapidly than the phage probe. Phage retained detectable binding ability for more than six weeks at 63 °C, and three days at 76 °C. The activation energy of phage degradation was determined to be 1.34×10⁵ J/mol. These results confirm that phage probes are highly thermostable and can function even after exposure to high temperatures during shipping, storage and operation.     

High-performance liquid chromatographic separation of gangliosides, combined with immunological detection and fast atom bombardment mass spectrometric characterization

A complete strategy for the isolation of individual mono- and disialogangliosides has been elaborated. We have used straight-phase silica gel chromatography or partitioning to obtain a crude ganglioside fraction. This fraction was then peracetylated and run through a second silica gel column. After anion-exchange chromatography the gangliosides were separated by straight-phase high-performance liquid chromatography with chloroform-methanol-water mixtures as eluting solvents. The method is suitable for preparative isolation of gangliosides and subsequent structural characterization by thin-layer chromatography-enzyme-linked immunosorbent assay, fast atom bombardment mass spectrometry and/or gas chromatography-mass spectrometry, which is demonstrated by several examples, including the separation of GalNAc-II3NeuAc-GgOse4Cer from GalNAc-isoII3NeuAc-GgOse4Cer.     

Convenient and High-Yielding Preparations of Mono(5-carboxy-2-ethylpentyl) Phthalate and its Ring-Deuterated Isomer – The “Third” Major Metabolite of Bis(2-ethylhexyl) Phthalate

Summary. The synthesis of an oxidative major metabolite of bis(2-ethylhexyl) phthalate is described. The target molecule and its ring-deuterated isomer were obtained via acylation of the appropriate -hydroxy benzyl ester or the corresponding carboxylate with phthalic anhydride or phthalic anhydride-d₄. All transformation steps proceed with high yields.     

Facts and artifacts about aromatic stability estimation

The stability of a set of 105 five-membered π-electron systems (involving aromatic, non-aromatic and anti-aromatic species) was evaluated using six isodesmic reactions of which two belong to the subclass of homodesmotic reactions, which are based on cyclic and acyclic reference systems. We demonstrate that the ‘Resonance Energies’ derived from isodesmotic schemes have obvious flaws and do not correct or cancel other contributions to the energy, such as the changes of hybridization, homoconjugation of heterosubstituted cyclopentadienes, conjugative interactions of CC or CX (X=N or P) with a π or pseudo π orbital at Y (Y=O, S, NH, PH), strain, etc. as effectively as possible. Likewise, ‘aromatic stabilization energies (ASE)’ derived from homodesmotic schemes based on the acyclic reference compounds do not give satisfactory results. We strongly recommend that only cyclic reference compounds should be used for ASE and other aromaticity evaluations. The analysis is based on ab initio optimized geometries at B3LYP/6-311+G^∗∗.     

Isotachophoretic separation of organic acids in biological fluids

The operating conditions for the isotachophoretic separation of organic acids were evaluated. At pH values ranging from 2.90 to 4.25 both relative step heights and molar flow-rates were determined experimentally for 26 anions. Comparing the observed values with simulated data, highly significant (p = 0.0001) correlation coefficients of 0.993 and 0.920, respectively, were found at pH 3.50. Whereas the concentration of the leading electrolyte did not affect the relative step heights, it increased the molar flow-rates significantly. The same applied to the detection current. The time of analysis was observed to be a function of the concentration of the leading electrolyte. However, the time elapsed between injection of the analyte and its detection depended solely on the volume and not on the amount of analyte injected. In isotachophoresis, incomplete separation of two compounds is indicated by the occurrence of a mixed zone which can hardly be distinguished from a pure zone. Thus, knowledge of the separation capacity is a prime prerequisite in optimizing the system for the analysis of biological fluids. The separability of nine equimolar pairs of anions was determined at pH values ranging from 2.90 to 4.25. Although two ionogenic constituents would separate only when their migration rates in the mixed state were different, no clear correlation was observed between separation capacity and difference in relative mobility. Separability, however, was found to increase with increasing concentration of the leading electrolyte. While the separation capacity was not influenced by the electric current, it was significantly affected by the volume injected. In subsequent analyses of serum, cerebrospinal fluid, seminal plasma and prostatic fluid, a variety of organic acids could be detected. Calibration graphs for the detected anions revealed a detection limit of 1 nmol and linearity over their biological concentration ranges. Further, the isotachophoretic results correlated well with high-performance liquid chromatographic and enzymatic analyses of citric acid and lactic acid in human seminal plasma and cerebrospinal fluid, respectively.