Effect of nicotine on the chemiluminescence of lucigenin in model membrane structures

The chemiluminescence of the classical lucigenin light reaction is adversely affected by nicotine in didodecyldimethylammonium bromide bilayer lamelar aggregates. The ratio of chemiluminescence quantum yields in the oriented medium, with and without nicotine, is equal to e^{–0.571[Nicotine]} whereas in the homogenous medium, the same ratio is equal to e^{–0.214[Nicotine]}. Furthermore, the appearance of the primary emitter's (N-methylacridone) emission in the chemiluminescence spectrum, already observed in oriented systems, is strongly supressed by nicotine.

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Der Effekt von Nikotin auf die Chemilumineszenz von Lucigenin in Modellmembranen

Zusammenfassung Die Chemilumineszenz der klassischen Lucigenin-Lichtreaktion wird von Nikotin in Didodecyldimethylammoniumbromid-Lamellaraggregaten geschwächt. Das Verhältnis der Chemilumineszenzquantenausbeuten ist in orientiertem Medium — mit oder ohne Nikotin — e^{–0,571[Nikotin]}, in homogenem Medium jedoch e^{–0,214[Nikotin]}. Außerdem wird die Emission des Primäremitters (N-Methylacridon) im Chemilumineszenzspektrum von Nikotin stark unterdrückt.

     

Chemiluminescence in model membrane structures chemiluminescence of lucigenin in the presence of estrogens

The chemiluminescence quantum yields of the lucigenin light reaction in 10^–2 M didodecyldimethylammonium bromide (DDAB) lamelar aggregates are affected by the presence of estrone and 17 -ethynylestradiol. A rise in quantum yields is observed at ca. 1·10^–4 M estrogen concentration as compared with the homogeneous (aqueous) medium, followed by a dramatic drop as the estrogen concentration increases. Unexpectedly, the smecticity of the lamelar aggregate is destroyed by estrone concentration as low as 10^–3 M and 17 -ethynylestradiol concentrations as low as 2·10^–4 M.

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Chemilumineszenz in Modell-Membranstrukturen Die Chemilumineszenz von Lucigenin in Gegenwart von Estrogenen

Zusammenfassung Die Chemilumineszenzquantenausbeuten der Lucigenin-Lichtreaktion in 10^–2 M Didodecyldimethylammoniumbromid (DDAB)-Lamellaraggregaten wird bei Gegenwart von Estron und 17 -Ethinylestradiol beeinflußt. Es wird eine Erhöhung der Quantenausbeuten bei ca. 1·10^–4 M Estrogengehalt gegenüber einem homogenen (wäßrigen) Medium beobachtet, bei Erhöhung der Estrogenkonzentration erfolgt jedoch eine drastische Erniedrigung der Quantenausbeuten. Die Smektizität der Lamellaraggregate wird bei Estronkonzentrationen von etwa 10^–3 M und 17 -Ethinylestradiolkonzentrationen von etwa 2·10^–4 M unerwarteterweise zerstört.

     

Electrogenerated chemiluminescence of lucigenin in aqueous alkaline solutions at a platinum electrode

Lucigenin is shown to emit light during electrolysis in aqueous alkaline solutions at a platinum electrode. In the mechanism proposed, lucigenin is initially reduced at —0.30 V vs. Ag/AgCl and subsequently the reaction product reacts either with oxygen or a reduction product of oxygen. Previous evidence on this phenomenon is contradictory.     

Determination of phosphate in freshwater samples by flow-injection with lucigenin chemiluminescence

Lucigenin chemiluminescence (CL) in conjunction with flow-injection analysis (FIA) is used for the determination of phosphate in freshwater samples. The procedure is based on the formation of molybdophosphoric heteropoly acid (MoP–HPA) by the reaction of phosphate and ammonium molybdate under acidic conditions. CL emission was observed as a result of oxidation of lucigenin in aqueous sodium hydroxide solution in the presence of MoP–HPA. Calibration was linear up to 500?µg?L^?1 (r ^2?=?0.9998; n?=?8), with a detection limit (S/N?=?3) of 0.95?µg?L^?1. An injection throughput of 120 h^?1, and relative standard deviation (RSD; n?=?4) of 1.3–3.2% were achieved in the concentration range studied. An on-line chelating column was used to remove interfering cations. The method was applied to freshwater samples, and the results (51?±?1.0 – 107?±?2.0?µg?L^?1) did not differ significantly from results obtained using a spectrophotometric method (52.5?±?1.0 – 102?±?2.0?µg?L^?1) at 95% confidence level (t-test).     

Chemiluminescence in model membrane structures. Chemiluminescence of lucigenin in the presence of Mg(OH)2 and benzyl alcohol. Temperature effects

The quantum yields of the lucigenin light reaction in didodecyldimethylammonium bromide (DDAB) are affected by the presence of Mg(OH)₂; a 35% increase is observed in lamellar and a 65% increase in vesicular aggregates. The system is insensitive to benzyl alcohol. The quantum yields inDDAB versus those in water, as a function of temperature show a slope change in the region of the phase transition in lamelar aggregates. This effect is far less pronounced in vesicular aggregates. In contrast to theDDAB aggregates, anionic sodium dimethyldidodecylphosphate (SDDP) sonicated aggregates are associated with lower quantum yields and no apparent slope change in the region of the phase transition.

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Chemilumineszenz in Modell-Membranstrukturen. Die Chemilumineszenz von Lucigenin in der Gegenwart von Mg(OH)₂ und Benzylalkohol. Temperatureffekte

Zusammenfassung Die Quantenausbeuten der Lichtreaktion von Lucigenin in Didodecyldimethylammoniumbromid (DDAB) werden durch die Gegenwart von Mg(OH)₂ beeinflußt. Es wird 35% Verstärkung in lamellaren und 65% Verstärkung in vesicularen Aggregaten beobachtet. Das System ist Benzylalkohol gegenüber unempflindlich. Eine Gegenüberstellung der Quantenausbeuten inDDAB bzw. in Wasser als eine Funktion der Temperatur zeigt eine Änderung des Anstiegs im Bereich des Phasenüberganges bei lamellaren Aggregaten. Dieser Effekt ist in vesicularen Aggregaten nicht so ausgeprägt. Im Gegensatz zu denDDAB-Aggregaten sind die beschallten anionischen Natriumdimethyldodecylphosphat (SDDP)-Aggregate durch geringere Quantenausbeuten und keine offensichtlichen Anstiegsänderungen im Bereich des Phasenüberganges gekennzeichnet.

     

The electrogenerated chemiluminescent behavior of hemin and its catalytic activity for the electrogenerated chemiluminescence of lucigenin

The electrogenerated chemiluminescent (ECL) behavior of hemin at a platinum electrode in the alkaline solution has been investigated in detail. Under the optimum conditions the linear response range of hemin is 1.0×10⁻⁵–1.0×10⁻⁸ g ml⁻¹, the detection limit was 1.0×10⁻⁸ g ml⁻¹, and the relative standard derivation for 1×10⁻⁷ g ml⁻¹ hemin was 2.8%. It has been also found that hemin would catalyze the ECL of lucigenin at a platinum electrode in a neutral solution in the presence of hydrogen peroxide, the catalytic ECL intensity was linear with the concentration of hemin in the range of 1.0×10⁻¹⁴–1.0×10⁻¹⁰ g ml⁻¹. IgG labeled with hemin was used to examine the ECL catalytic activity of hemin after conjugating to protein, and the results showed that hemin retained ECL catalytic activity when conjugated to protein.     

Theoretical study on structures and stability of C4P isomers

The structures, energetics, spectroscopies, and stabilities of doublet C(4)P isomeric species are explored at the DFT/B3LYP, QCISD, and CCSD(T) (singlet-point) levels. A total of 12 minimum isomers and 27 interconversion transition states are located. At the CCSD(T)/6-311G(2df)//QCISD/6-311G(d)+ZPVE level, the lowest-lying isomer is a floppy CCCCP 1 (0.0 kcal/mol) mainly featuring a cumulenic structure |C=C=C=C=P*|, which differs much from the analogous C4N radical (|*C-C[triple bond]C-C[triple bond]N|). The quasi-linearity and the low bending mode of 1 are in contrast to the previous prediction. The second energetically followed isomer PC-cCCC 3 (14.9 kcal/mol) possesses a CCC ring-bonded to CP. The two low-lying isomers are separated by a high-energy ring-closure/open transition state (26.5 kcal/mol) and thus are very promising candidates for future laboratory and astrophysical detection. Furthermore, four high-energy isomers, that is, two bent isomers CCPCC 2 (68.4 kcal/mol) and CCPCC 2' (68.5 kcal/mol) and two cagelike species 10 (56.0 kcal/mol) and 11 (67.9 kcal/mol), are also stabilized by considerable barriers. The present work is the first detailed potential energy survey of CnP clusters and can provide useful information for the investigation of larger CnP radicals and for understanding the isomerism of P-doped C vaporization processes.     

Synthesis and structures of palladium P,C,P pincer complexes based on ferrocene

Russian Chemical Bulletin -     

Effect of cooling baths on EVOH microporous membrane structures in thermally induced phase separation

The purpose of this work is to investigate the effect of cooling bath on the membrane preparation of crystalline polymer/diluent system via thermally induced phase separation (TIPS), when the cooling bath is compatible with the diluent. In this work, poly(ethylene-co-vinyl alcohol) (EVOH)/PEG300 system with water and methanol as the cooling baths was proposed. Results showed that when water was used as the cooling bath, the membrane presented an asymmetric structure consisting of a porous skin, macrovoids near the top and lacy structures near the bottom. In contrast, when cooled in the bath of methanol, it showed particulate morphology on the top surface and cellular pores near the bottom. The lacy and cellular structures were the typical structures resulted from liquid–liquid thermally induced phase separation, the novel macrovoids and particulate morphology were then supposed to be induced by the mutual diffusion between the diluent and the cooling bath. In the case of water, the diluent's outflow was comparative with the water's inflow into the membrane, so the penetrated water acted as a strong nonsolvent and induced macrovoids near the top. In the bath of methanol, the diluent's outflow was much faster than the methanol's inflow, which changed the solution composition from a liquid–liquid phase separation region to a solid–liquid phase separation region and resulted in particulate morphology near the top.     

Effect of a magnetic field on thermostimulated chemiluminescence

Conclusions Effects, associated with relaxation of the spins and the rates of the electronic transitions as a function of the spin states, which determine the sensitivity of processes to an external magnetic field, can be observed in thermally stimulated chemical reactions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2355–2356, October, 1974.     

A refined numerical model for determining inflation-burst behavior of composite membrane structures

The airship structures made of multi-layer composite fabrics or membranes can offer the platform for earth observations, wireless communications and space research due to light weight and good mechanical performance. The structural safety and serviceability strongly depend on material properties and working conditions. Available studies are limited within service stress limits or are lack of suitable biaxial tensile constitutive models for understanding structural behavior. This paper thus focuses on a refined numerical model for determining inflation-burst behavior of composite airship structures considering new biaxial constitutive equations, novel failure criteria and manufacture factors.The differences between ideal and real forms of airship structures, e.g. volume difference, demonstrate the necessity for incorporating cutting-pattern effects in the initial numerical model. For structural analysis, stress distributions on real structural forms are different from those on ideal forms because of welding parts that can enhance local stiffness. The ultimate pressures are 56.7 kPa and 59.5 kPa for ideal and real structural forms. Structural breaking initiated at the maximum diameter of ideal structural forms propagates fast while welding parts can prevent breaking propagation for real structural forms. Therefore, the refined numerical model can reveal basic structural behavior and safety performance of airship structures in the inflation-burst processes.     

Effect of friction between particles in the dynamic response of model magnetic structures

A simple particle-level simulation model that takes into account interparticle friction forces is developed to describe the dynamic response of magneto-rheological fluids. The results obtained for single-width particle chains are found to be in good agreement with slender body theory predictions [J. de Vicente, M.T. López-López, J.D.G. Durán, G. Bossis, J. Colloid Interface Sci. 282 (2005) 193]. The addition of side chains to a single-width one results in one order of magnitude increase of storage modulus and relaxation. The double logarithmic plot of storage and loss moduli vs frequency gives a limiting slope of one when including friction forces between particles. Simulation results are found to be in agreement with experimental measurements on an iron/kerosene model MR-fluid.     

Effect of iron chelates on luminol chemiluminescence in the presence of xanthine oxidase

Xanthine oxidase, in catalysing the oxidation of hypoxanthine to uric acid, produces hydrogen peroxide. Chemiluminescence is produced by oxidation of luminol by reactive hydroxyl radicals formed from H₂O₂ by Fe-EDTA and similar complexes. The concentrations of the various components in the active reagent are optimized in order to obtain a constant chemiluminescent signal of high intensity. The effect of chelate structure on chemiluminescence generation is studied, and a structure-activity relationship is deduced. The detection limit for xanthine oxidase is 5 pg.     

Voltammetric study of the electrochemical reduction of lucigenin in aqueous medium

The electrochemical reduction of lucigenin (bis-N-methylacridinium nitrate) in aqueous solution was studied by d.c. Tast polarography at a dropping mercury electrode, by cyclic voltammetry at an amalgamated gold electrode and at a hanging mercury drop electrode, and by microcoulometry. The effects of pH, lucigenin concentration and temperature were studied, and special methods were applied to study the suspected adsorption and catalytic (regeneration) currents. A spectrophotometric study is also reported. It was found that lucigenin is reduced in two separate one-electron steps. An adsorption prewave accompanies the first step, while the second, below pH 3.5, is catalytic, owing to the chemical regeneration of the intermediate reduction product at the electrode surface.     

Synthesis of a piperidone model compound and revision of the structures of jenamidines A to C

Reaction of 2,3-dihydro-4-pyridone (4) with isatoic anhydride (5) provided the unstable product 6, for which the NMR spectral data are quite different from those reported for the ring system of jenamidine A. This suggests that the proposed structures 1 to 3 of jenamidines A to C should be revised to 8 to 10.     

Effect of mixing modes on chemiluminescent detection of epinephrine with lucigenin by an FIA system fabricated on a microchip.

The chemiluminescent (CL) detection of epinephrine (EP) with lucigenin (Luc) was performed using a micro flow cell fabricated on a silicon chip. A solution of EP was injected into the Luc carrier stream. The Luc solution containing EP and an alkaline solution were successively poured into the flow cell by a pressure-driven flow system. Two types of flow cells were fabricated for estimating the effect of the mixing modes in the flow cells on the intensity of light emission. In flow cell 1, two streams entered through separate inlet ports and merged to flow adjacently. In flow cell 2, a Luc solution containing EP was split up to 36 partial flows by passage through the nozzles, and was injected into the alkaline solution. The intensity of light emission in flow cell 2 increased markedly compared to that in flow cell 1. The detection limit of 8.0 x 10(-7) M for EP in flow cell 2 was a factor of six-times better than that in flow cell 1. The improvement in the sensitivity for EP could be explained in terms of the distortion of laminar flow in flow cell 2.     

Effect of surfactants on the chemiluminescence of acridinium dimethylphenyl ester labels and their conjugates

Chemiluminescent acridinium dimethylphenyl esters, containing two methyl groups flanking the phenolic ester bond, display excellent chemiluminescence stability and are used as labels in automated immunoassays for clinical diagnostics. Light emission from these labels is triggered with alkaline peroxide in the presence of the cationic surfactant cetyltrimethylammonium chloride. Under these conditions, light emission is rapid and is complete in <5 s. In the present study we examined the effect of various surfactants on light emission from acridinium dimethylphenyl ester labels and their conjugates containing hydrophilic linkers derived either from hexa(ethylene)glycol or a sulfobetaine zwitterion. Sulfobetaine zwitterions are very polar and incorporation of these functional groups in acridinium dimethyphenyl esters and their conjugates represents a new approach to improving the aqueous solubility of these chemiluminescent labels. Our results indicate that in general, surfactants affect light emission from these labels and their conjugates by two discrete mechanisms. Cationic surfactants, but not anionic or non-ionic surfactants, accelerate overall light emission kinetics and a more modest effect is observed with zwitterionic surfactants. Surfactants also enhance total light output and the magnitude of this enhancement is maximal for cationic surfactants and a sulfobetaine zwitterionic surfactant. These observations are the first to clearly delineate the role of the surfactant on the chemiluminescence reaction pathway of acridinium esters and can be rationalized based on known effects of surfactant aggregates on bimolecular and unimolecular reactions.     

Effect of eluant composition on the retention of water-soluble vitamins in reversed-phase high-performance liquid chromatography

The effects of the quantitative composition and pH of water-acetonitrile eluants and temperature on the retention of water-soluble vitamins in reversed-phase high-performance liquid chromatography were studied. The retention parameters of the analytes were calculated and the limits of the applicability of the main adsorption models of retention to the test chromatographic system were discussed.     

Alkaline phosphatase-labeled macromolecular probe for sensitive chemiluminescence detection of proteins on a solid-phase membrane

In the present study, we synthesized dextran (MW = ca. 2,000 kDa)-based macromolecular probes containing multiple molecules of alkaline phosphatase (ALP) as a signal-trigger enzyme and of biotin as an assembly mediator. The ALP and biotin molecules were covalently attached into the dextran backbone after the formation of aldehyde groups into the macromolecule by periodate oxidation. The synthesized probes contained 27–31 molecules of ALP in their macromolecules when 50-fold molar ratio of ALP to the dextran was used for the synthesis. These probes provided 14–20 times stronger chemiluminescence (CL) than that of the equimolar free ALP adsorbed on a nylon membrane. The velocity of the CL reaction of ALP-catalyzed adamantlyl-1,2-dioxetane substrate was improved from a slower emission (glow type) of CL to a faster one (flash type). The CL signal integrated for 2 min under strongly alkaline conditions (pH 13.0) was about ten times greater than that obtained by the conventional conditions (pH 9.5). Therefore, the synthesized macromolecular probe could be successfully utilized for the high-throughput CL detection of biotin-conjugated anti-rabbit IgG antibody with a lower detection limit of 880 amol per spot on the nylon membrane. This study provides analytical strategy for the rapid, convenient, and sensitive detection of target proteins in immunoassays.