Capillary electrophoretic separation of enantiomers in a high-pH background electrolyte by means of the single-isomer chiral resolving agent octa(6-O-sulfo)-gamma-cyclodextrin

The new, alkali-stable, single-isomer, sulfated gamma-cyclodextrin, the sodium salt of octa(6-O-sulfo)-gamma-cyclodextrin (OS) was used for the first time to separate the enantiomers of non-ionic, acidic, basic and ampholytic analytes by capillary electrophoresis in high-pH aqueous background electrolytes. The effective mobilities and separation selectivities were found to follow trends similar to those observed earlier in acidic aqueous background electrolytes. OS proved to be a broadly applicable chiral resolving agent and afforded adequate peak resolution values with short separation times for a number of non-ionic, weak acid, weak base and ampholytic analytes.     

Isoelectric buffers, part 3: determination of pKa and pI values of diamino sulfate carrier ampholytes by indirect UV-detection capillary electrophoresis

Ampholytes with close pK(a) values (i.e., good carrier ampholytes (CAs)) are needed as buffers in pH-biased isoelectric trapping (IET) separations. The syntheses of two families of such good CAs were reported recently. Members of the family of diamino sulfate ampholytes (first series) had pI values in the 5.7 < pI < 9.0 range. Members of the family of quaternary ammonium dicarboxylic acid ampholytes (second series) had pI values in the pI < 4.3 range. To further characterize the diamino sulfate ampholytes, their effective mobilities were measured by indirect UV-absorbance detection capillary electrophoresis in a series of background electrolytes (BGEs) with different pH values. The pK(a) and limiting ionic mobility values of the CAs were obtained by fitting these mobility values, as a function of the pH and the ionic strength of the BGEs, to the theoretical mobility expression. These diamino sulfates complete the list of CAs suitable for IET separations.     

Preparative-scale isoelectric trapping enantiomer separations

The new Gradiflow BF200 IET unit, developed for isoelectric trapping protein separations has been modified and used to carry out preparative-scale enantiomer separations. Hydroxypropyl beta-cyclodextrin was used as the chiral resolving agent to induce an isoelectric point difference between the enantiomers. Three isoelectric membranes with isoelectric points below, in between and above the isoelectric points of the complexed enantiomers were used to trap the separated enantiomers in the anodic and cathodic separation compartments of the Gradiflow BF200 IET apparatus, respectively. The production rates were about 15 times higher than those previously obtained with another isoelectric trapping device and about 30% higher than those obtained in a continuous free-flow electrophoretic device operated in the isoelectric focusing mode. The remarkable separation speed observed in the modified Gradiflow BF200 IET unit is attributed to the favorable interplay of the short electrophoretic transfer distance, the high electric field strength and the large effective surface areas of the isoelectric membranes.     

Isomerisierung von (all-E)-Cycloviolaxanthin Herstellung und Charakterisierung von (9Z)-und (13Z)-Cycloviolaxanthin

Isomerization of (all-E)-Cycloviolaxanthin. Preparation and Characterization of (9Z)- and (13Z)-Cycloviolaxanthin From (all-E)-cycloviolaxanthin (ex Capsicum annuum), (9Z)- and (13Z)-cycloviolaxanthin were prepared in a highly pure state. The configuration of both isomers was determined by means of UV/VIS, NMR, and CD spectroscopy.     

A Thermally Induced Low-temperature Intramolecular Redox Reaction of bis(pyridine)silver(I) Permanganate and its hemipyridine Solvate

Among the known three pyridine complexes of silver permanganate, i.e. [Agpy₂]MnO₄ (1), [Agpy_2.25]MnO₄ or 7[Agpy₂]MnO₄[Agpy₄]MnO₄ (2) and [Agpy₂]MnO₄0.5py (3), compounds (1) and (2) were studied by means of thermal analysis and TG-MS methods. Presuming identical structural motifs for the Agpy₂MnO₄ blocks in (1) as it has been found in its solvate (3) by single-crystal diffraction, α-C–H...O–Mn H-bonded structures are responsible for a thermally induced low-temperature intramolecular redox reaction observed for the first time between the [Agpy₂]⁺ cation and permanganate anion.     

Quantum algebraic–combinatoric study of the conformational properties of n‐alkanes. I

Based on quantum chemical calculation results, four rules were previously derived for the numbers and the sequences of the conformers of free alkane molecules. This paper builds up first an algebra to handle the conformational problem of alkanes. Partitioning the set of all sequences, the whole problem is then subdivided into three independent subcases. With the help of an equivalence relation, the sequences can be classified. According to the quantum chemical rules, certain equivalence classes do not represent conformers. A welldefined subcase of the whole problem is solved.     

Moment Formulas for Multitype Continuous State and Continuous Time Branching Process with Immigration

Recursions for moments of multitype continuous state and continuous time branching process with immigration are derived. It turns out that the \(k\)th (mixed) moments and the \(k\)th (mixed) central moments are polynomials of the initial value of the process, and their degree is at most \(k\) and \(\lfloor k/2 \rfloor \), respectively.     

Natural and anthropogenic radionuclides in the rivers of Azerbaijan

In the frame of an International Atomic Energy Agency Technical Cooperation project, a radiological survey was performed in the Araks and Kura Rivers (Azerbaijan). Sediment samples, and where available, aquatic plants were collected along these two rivers and their inflow and tributary rivers. ¹³⁷Cs, ²³⁸U, ²³⁴U, ^239+240Pu, ²³⁸Pu, ⁹⁰Sr and ²⁴¹Am activity concentrations were measured. The radionuclide levels measured were relatively low, and in most cases below the detection limit, as compared with those from other areas of the world which have been directly affected by effluents from nuclear installations or influenced by the Chernobyl accident. The results indicated that the radionuclides are of natural origin or attributable to the atmospheric fallout from nuclear weapons tests or to the Chernobyl-derived deposition.     

On discretizations of invariant foliations over inertial manifolds

Invariant foliations over inertial manifolds of partial differential equations under numerical discretizations are studied. It is proved that the numerical method considered as a discrete dynamical system has C¹-close invariant foliations. The rate of the C¹-convergence is estimated as well.     

Temperature compensation in the oscillatory bray reaction

The influence of temperature on the oscillatory frequency of the hydrogen peroxide-iodate ion reaction is found to be two-sided: (i) the period length decreases with increasing temperature in most of the instances studied, (ii) or in some cases an opposite change is observed. A temperature-independent period length (temperature compensation) is also discovered experimentally in a rather wide temperature interval at a narrow concentration range of reactants both in a batch configuration and under flow conditions. A simple model was considered to simulate this behavior. Opposing effects of the composite reactions of the model on the calculated period length with changing temperature are shown to be responsible for temperature compensation or overcompensation.