A Highly Sensitive and Selective Assay for Cysteine Using the Chemiluminescence Reaction of Luminol and Hydrogen Peroxide

A very simple, highly sensitive and selective chemiluminescence (CL) method was established for the determination of cysteine. This method is based on the fact that the CL reaction of luminol and hydrogen peroxide can be greatly enhanced by cysteine. The CL intensities at maximum light emission were linearly correlated with the concentration of cysteine over the range of 2.0×10^–8–6.0×10^–6molL^–1 with a detection limit of 7.5×10^–9molL^–1. The relative standard deviation was 1.7% for the determination of 1.0×10^–7molL^–1 cysteine (n=9). The feasibility of utilizing the proposed method for the determination of total concentration of cysteine in human serum was examined.     

Kinetic Determination of Microquantities of Rutin by Perturbation of the Bray-Liebhafsky Oscillatory Reaction in an Open System

A kinetic method is described for the microquantitative (microconcentration/microvolume) determination of rutin based on potentiometric monitoring of the concentration perturbations of the Bray-Liebhafsky (BL) oscillatory reaction being in a non-equilibrium stationary state close to a bifurcation point. The experiments are carried out in an open reactor. The response of the matrix system to perturbations by different concentrations of rutin ethanolic solutions is followed by a Pt-electrode. In the concentration range between 7.8×10^–8moldm^–3 and 9.1×10^–6mol dm^–3, we found a linear dependence of the maximal potential shift, E_m, on the logarithm of the rutin concentrations. The unknown concentrations can be determined from the calibration curve up to an accuracy of ±5%. The detection limit is 3.6×10^–8mol dm^–3. The amount of required sample can be as small as 10µL.     

Design of Supramolecular Cyclodextrin Complex Sensors for Ion and Molecule Recognition in Water

The design and function of novel supramolecular fluoroionophore/cyclodextrin (CyD) complex sensors for ion and molecule recognition in water are reviewed. For the crown ether fluoroionophore/-CyD complex, the dimerization of the fluoroionophore inside the -CyD is found to be selectively promoted by alkali metal ion binding, thereby resulting in metal-ion-selective pyrene dimer emission in water. This supramolecular function is successfully utilized in the design of a podand fluoroionophore/-CyD complex for sensing toxic lead ion in water. The boronic acid fluoroionophore/-CyD complex binds sugars and produces increased fluorescence emission in water. The response mechanism appears to be due to the suppression of the photoinduced electron transfer (PET) from pyrene donor to trigonal phenylboronic acid acceptor. This is a novel emission function provided by the boronic acid fluoroionophore/-CyD complex sensors in water.     

Electron transfer coupled with ATP hydrolysis in nitrogenase

Nitrogenase, which is not a membrane protein in vivo, performs energy coupling: the transfer of an electron coupled with ATP hydrolysis from one protein component of nitrogenase, Fe protein (Av2), to another its protein component, MoFe protein (Av1), to form the so-called super-reduced state of the active site responsible for the reduction of the substrates, FeMo cofactor (FeMoco) containing Fe, Mo, S, and homocitrate. The review discusses recent publications on studying the electron transfer coupled with ATP hydrolysis in nitrogenase and evaluates a possible value of the redox potential of the super-reduced FeMoco.     

Chemical Bonding in Thermodynamically Labile Oxyanion Crystals

Crystal valence density and difference density distributions were calculated for NaNO₂, NaNO₃, KClO₃, and NaClO₄ using local density functional theory. Hybridization of the oxygen states is enhanced in compounds with lower symmetry, leading to the formation of oxygen chains in the lattice. Interaction between the oxygen and anion's central atom sublattices gives rise to electron charge maxima in the middle of the A—O bonds and to two terminal oxygen maxima. The complex character of the intraanion electron transfer and the charge transfer between the nonequivalent oxygen sublattices make these compounds susceptible to external energy effects that lead to their solidstate decomposition.     

Spectral Studies on the Cyclodextrin Inclusion Complexes of Toluidine Blue O and Meldola's Blue in Aqueous Solution

The absorption and emission spectral properties of toluidine blue O (TBO) and Meldola's blue (MDB) in the presence of cyclodextrins (CDs) were studied. Formation of 1 : 1 and 1 : 2 (CD-Dye) inclusion complexes were observed with -CD and -CD, respectively. An increase in the emission intensity was noticed in the presence of -CD due to the formation of 1 : 1 (CD-Dye) inclusion complexes. However, a decrease in the emission intensity was observed in the presence of -CD due to the formation of 1 : 2 (CD-Dye) inclusion complexes. Dimerization of dye molecules in the presence of -CD lead to a decrease in the emission intensity. The formation constants for the 1 : 1 and 1 : 2 (CD-Dye) inclusion complexes were calculated.     

Temperature Dependence of Transport Properties and Ion–Molecular Forms of LiAsF6 in γ-Butyrolactone

The solvation and association electrolyte interactions are analyzed in the concentration range of 0–2 m at temperatures of 253.15–313.15 K using measurements of the conductivity and viscosity of LiAsF₆ solutions in -butyrolactone (-BL). Concentrated LiAsF₆ solutions in -BL are considered as molten electrolytic solvates, whose transport processes are considerably influenced by a cooperative restructuring of the system. The concentration dependence of the molar conductivity is linear in the vs. c^1/3 coordinates, which agrees with a theory of quasi-crystalline electrolyte lattice in solution. The Lee–Wheaton model is used to determine the limiting molar conductivities, distance parameters, and association constants and their temperature dependences. The size of solvate spheres increases with decreasing temperature and their overlapping occurs at lower concentrations.     

Electron Excited M X-Ray Spectra of the Elements 55≤Z≤58

The M emission spectra of the elements 55 Cs, 56 Ba, 57 La, and 58 Ce were measured using wavelength dispersive X-ray spectrometry with a TAP crystal as the dispersing element. In total, 34M lines were observed, of which only 13 are contained in the compilation of Bearden. M and M of 56 Ba are among the new lines. They have their origin in a similar process to one that is known for 57 La. The interpretation of these spectra is complicated by the strong overlap of some emission lines with the M_IV,V absorption structures, which may lead to anomalous self-absorption effects. Therefore, we have concentrated on spectra taken at a low energy of the exciting electrons, E₀=2.5keV. However, in order to illustrate the anomalous self-absorption effects parts of the 2.5keV spectra, of Ba and La, are shown in comparison with the 10keV spectra.     

Determination of Iodine in Enriched Chlorella by ICP-OES in the VUV Region

A method of determining iodine in the vacuum ultraviolet region by inductively coupled plasma optical emission spectrometry in enriched Chlorella is established and evaluated. Alga Chlorella samples enriched with iodine were solubilized with tetramethylammonium hydroxide. The iodine content was quantified by inductively coupled plasma optical emission spectrometry using the 182.980nm emission line of iodine to avoid the spectral interference from phosphorus which occurs in Chlorella at the 178.218nm emission line of iodine. The methods accuracy was confirmed by a modified Sandell and Kolthoff spectrophotometric method (As³⁺, Ce⁴⁺ and brucine) after alkaline ashing, and the agreement between the methods was about 96%. The limit of detection in real samples was 3mgkg^–1 for enriched Chlorella, and the iodine content in the samples varied between 100 and 1300mgkg^–1.     

Topological complexity of potential surfaces and application to C2H2 molecule

Summary In this work, we search for the simplest complete surfaces of systems with three and four atoms, i.e. the minimal sets of critical points with their index, which are topologically consistent in the whole configuration space. Then we show the smallest change in the A₂B₂ system by requiring at least one stable acetylene configuration and one stable vinylidene configuration, like on the C₂H₂ surface. Finally, we give complete sets of minima, saddle points and maxima obtained for C₂H₂ with analytical potentials proposed in the literature and with a semi-empirical method at the CAS-CI level.     

Study of internal rotation of the vinyl group in 1-, vinylpyridones by the AM-1 method

By the AM-1 method in the semirigid model approximation, the potential energy of internal rotation of the vinyl group has been calculated for 1-vinyl-2-pyridone, 1-vinyl-6-methyl-2-pyridone, and 1-vinyl-4-pyridone. The potential energy of internal rotation in the first and third of these molecules has two minima corresponding to torsion angles around the N-C bond approximately 0 and 180°, separated by barriers to internal rotation 3.99 and 2.94 kcal/mole, respectively. For the 1-vinyl-2-pyridone, the energy minimum at =180°, the s-cis(O) conformation, is 1.83 kcal/mole above the first minimum. For the 1-vinyl-6-methyl-2-pyridone, the torsion angles 0 and 180° correspond to energy maxima; the energy minima occur at 35° and 140°. In the harmonic oscillator approximation, the intervals of torsional vibrations of the vinyl group in these comopunds have been estimated. Data from the AM-1 calculation are in qualitative agreement with the available¹H and¹³C NMR data on the structure of 1-vinyl-2-pyridone, 1-vinyl-5-methyl-2-pyridone, and 1-vinyl-4-pyridone.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1367–1372, June, 1991.     

Das polarographische Verhalten von Chloriden der Lanthanoide in Dimethylsulfoxid und Dimethylformamid

Zusammenfassung Es werden die Halbwellenpotentiale der Chloride der Lanthanoide in Dimethylsulfoxid und Dimethylformamid gegen die gesättigte, wäßrige Kalomelelektrode angegeben. La, Ce, Pr, Nd, Gd, Tb, Dy, Ho und Er geben eine, Sm, Eu und Yb zwei Wellen, alle mit diffusionsbedingten Grenzströmen ohne Maxima. Die unterschiedlichen Reduktionsbereiche der Cerit- und Ytter-erden in Dimethylformamid gestatten ihre polarographische Trennung. Der Einfluß von Wasserspuren ist gering.

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The half wave potentials of chlorides of lanthanoides have been measured in dimethylsulfoxide and in dimethylformamide vs. an aqueous saturated calomel electrode. La, Ce, Pr, Nd, Gd, Tb, Dy, Ho and Er give one, Sm, Eu and Yb two waves all with limiting currents due to diffusion without maxima. The differences in half wave potentials of cerite earths and ytter earths in dimethylformamide allow their polarographic separation. The influence of traces of water is neglegibly small.

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Mit 1 Abbildung     

Biscyanines from isomeric benzodipyrrolenines

Biscyanines and their corresponding mother monocyanines were obtained from the three isomeric benzodipyrrolenines. Splitting of the absorption band of the mother monocyanine into two new bands, viz., a long-wave and a short-wave band, is observed for the biscyanines. The degree of splitting of the maxima for a para orientation of the chromophores in the benzene ring is about twice that for the meta position.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 618–620, May, 1971.     

Energy Transfer Electrogenerated Chemiluminescence for the Determination of Sulfite

A simple and novel electrogenerated chemiluminescence (ECL) method for the determination of sulfite has been developed based on the energy transfer ECL process. It was found that a weak ECL signal of sulfite was electrochemically generated on a platinum electrode in neutral aqueous solution. The signal was strongly enhanced by rhodamine B as an energy receptor and further enhanced by the neutral surfactant Tween 80. In 0.10M phosphate buffer solution (pH=7.5) containing 2.0×10^–6gmL^–1 rhodamine B and 0.4% (v/v) Tween 80, the ECL response to the concentration of sulfite at a potential of 0.82V was linear over a range of 1.0×10^–7gmL^–1 to 8.0×10^–6gmL^–1, and the detection limit was 5×10^–8gmL^–1. The relative standard deviation (n=11, 1.0×10^–6gmL^–1) was 3.8%. The proposed method has been successfully applied to the determination of sulfite in pharmaceutical injections and white sugar samples.     

Flow Injection Spectrofluorimetric Method for the Determination of Cadmium

A novel fluorescent reagent, o-vanillin furoylhydrazone (OVFH), was synthesized, and its infrared spectrum, elemental analysis and dissociation constant are reported. The reaction between Cd²⁺ and OVFH produces an intensely fluorescent complex in ethanol-water medium of pH 10.00, and this finding has led to a simple, rapid, and sensitive flow injection (FI) spectrofluorimetric method for on-line determination of Cd²⁺. Under the optimum experimental conditions, the fluorescent complex had excitation and emission maxima at 393 and 494nm, respectively. The linear range is from 0.025 to 8.0µgmL^–1 of Cd²⁺, the detection limit is 7.6µgL^–1 and the maximum sampling rate is 80h^–1. The effect of interferences was studied. The method was successfully applied to the determination of cadmium in environmental samples.     

EDX depths analysis of MIS-structures

Based on experimental energy transfer distributionsdE/dx including the X-ray depth distribution function (x,E ₀,Z) an effective-layer method has been developed in order to homogenize a multilayer target. Effective layer thicknesses are related to real layer thicknesses by means of equal transmission-energy rates. This method has been proved by EDX measurements of Au-SiO₂-Si structures showing good agreement with the real structures.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Untersuchungen an Röntgenemissionsprofilen von leichten Elementen mit der „Makrosonde”

Zusammenfassung Die Verschiebungen der Lage der Intensitätsmaxima im Röntgenemissionsprofil eines Elementes in verschiedenen Verbindungen werden mit chemischen Parametern in Zusammenhang gebracht, indem die Röntgenemissionsprofile von Sauerstoff in einer Reihe von Oxiden mit der Makrosonde aufgenommen und die Verschiebungen des Intensitätsmaximums im Sauerstoffemissionsprofil ermittelt werden. Dabei zeigt sich, daß die sogenannte Linienverschiebung von Sauerstoff in einem direkten stetigen Zusammenhang mit der Standardbildungsenthalpie der Oxide steht. Bei dem VerbindungstypMe₂O₃ zeigt sich außerdem eine annähernd lineare Abhängigkeit der Energie des Intensitätsmaximums im Sauerstoffemissionsprofil vom Ionencharakter der Metall-Sauerstoffbindung.Die Auswertung der Linienverschiebungen von Kohlenstoff, Stickstoff, Fluor und Chlor nach Literaturdaten zeigt, daß bei allen diesen Systemen ebenfalls ein stetiger Zusammenhang zwischen Linienverschiebung und Bildungsenthalpie besteht. Bei einigen Systemen—wie bei denen von Kohlenstoff und Chlor-besteht auch ein direkter Zusammenhang zwischen der Energie des Intensitätsmaximums im Emissionsprofil und dem Ionencharakter der Metall-Nichtmetallbindung.

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Studies of the X-ray emission profiles of light elements with the primary X-ray analyzer

The shifts of the position of the intensity maxima in the X-ray emission profile of an element in different compounds are correlated with chemical parameters by recording the X-ray emission profiles of oxygen in a series of oxides with the makrosonde and determining the shifts of the intensity maximum in the oxygen emission profile. It can thus be shown that between the so-called line shift of oxygen and the standard enthalpies of formation of the oxides a direct and continuous relationship exists. In compounds of the typeMe ₂O₃ there is in addition an almost linear dependence of the energy of the intensity maximum in the oxygen emission profile from the ionic character of the metal-oxygen bond.Interpretation of the line shifts of carbon, nitrogen, fluorine and chlorine according to literature data shows that in all these systems a continuous relationship between line displacement and enthalpy of formation likewise exists. In a few systems-such as those of carbon and chlorine-there is furthermore a direct relationship between the energy of the intensity maximum in the emission profile and the ionic character of the metal-nonmetal bond.

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Herrn Prof. Dr.H. Nowotny gewidmet.     

A variational coupled cluster theory for closed shells using a propagator modification procedure

A general partial summation method for including arbitrary classes of diagrams to all orders in the coupled cluster based size consistent energy functional for closed shell states is developed. Since the various reduced density matrices which appear in the energy functional are essentially the time-independent analogues of the corresponding many body Green functions, it is possible to derive Dyson-like equations for these quantities. By expanding the associated proper self energy parts in terms of the T-amplitudes, one can carry out partial summations in the reduced density matrices and thus in energy. At a higher level, higher order terms in a proper self energy can also be generated by renormalizing the internal propagators in it, and considering only the irreducible self-energy terms.     

Synthesis of unsaturated diketones and derivatives of Δ 2-pyrazoline based on 1, 4-diacetylbenzene

By means of the crotonic condensation of 1,4-diacetylbenzene with various aromatic and heterocyclic aldehydes, thirteen , -unsaturated diketones (diarylidene-1,4-diacetylbenzenes) were synthesized. The majority of these compounds are characterized by means of their bis(2,4-dinitrophenylhydrazones), the absorption maxima of which were determined in a solution of chloroform. By means of the interaction between diarylidene-1,4-diacetylbenzenes and phenylhydrazine hydrochloride, ten 1,4-bis(1-phenyl-5-R- ²-pyrazolinyl-3) benzenes were obtained which possess a bright green or blue luminescence.