Application of solvent extraction and synchronous spectrofluorimetry to the determination of the formation constant for a 1:1 complex of carbazole withβ-cyclodextrin in water-dimethyl sulfoxide medium

Extraction of carbazole in heptane was performed at 25±1°C with an aqueous dimethyl sulfoxide (DMSO) medium containing w41pr63p0g110850/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin (w41pr63p0g110850/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">CD) at consecutive concentrations in the range of 0–10 mM. The fluorescence intensity of carbazole remaining in the heptane phase was measured by synchronous scanning fluorimetry. The apparent formation constant (K _f) for a 1:1 carbazole: w41pr63p0g110850/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">CD inclusion complex in water-DMSO medium was determined by using a linear plot of the distribution ratio calculated from the fluorescence intensities vs. the w41pr63p0g110850/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-CD concentration. The values thus obtained ranged from 477 M^–1 in a 10% v/v DMSO medium to 12.1 M^–1 in a 60% v/v medium. Good linear relationships were observed between logK _f and the DMSO concentration ([DMSO]), and also between logK _f and the logarithm of the distribution coefficient (K _d) for carbazole. The formation constant in 100% water was estimated to be approximately 1.0×10³ M^–1 on the basis of the logK _f vs. [DMSO] and the logK _f vs. logK _d correlations.     

Mixed strategy solutions forN-person quadratic games

Mixed strategy w8k/xxlarge8712.gif" alt="isin" align="MIDDLE" BORDER="0">-equilibrium points are given forN-person games with cost functions consisting of quadratic, bilinear, and linear terms and strategy spaces consisting of closed balls in Hilbert spaces. The results are applied to linear-quadratic differential games with no information and quadratic integral constraints on the control functions.This work was supported by a Commonwealth of Australia, Postgraduate Research Award.     

About a minimax theorem of Matthies,Strang and Christiansen

We give a new minisup theorem for noncompact strategy sets. Our result is of the type of the Matthies-Strang-Christiansen minimax theorem where the hyperplane should be replaced by any closed convex set. As an application, we derive a slight generalization of the Matthies-Strang-Christiansen minimax theorem.     

On the affinity of cytosine towards electrophiles

Ab initio SCF computations on the intrinsic preferences of the H⁺, CH ₃ ⁺ and C₂H ₅ ⁺ cations towards the two principal sites of protonation or alkylation on cytosine, N₃ or O₂, show that this preference undergoes a continuous modification with the increase in size and complexity of the cation. N₃ is the preferred site of fixation of H⁺, O₂ the preferred site of C₂H ₅ ⁺ , while CH ₃ ⁺ has no marked preference. The exchange repulsion term of the binding energy appears responsible for the preference of C₂H ₅ ⁺ for O₂.This work was supported by the Ligue Francaise contre le Cancer and the National Foundation for Cancer Research (USA)     

Atom-surface elastic scattering in the presence of laser radiation

A qualitative discussion on atom-surface elastic scattering taking place in the presence of laser radiation is given. It is suggested that appreciable effects of laser radiation on diffraction patterns may be expected if the laser radiation is capable of inducing electronic transitions in atoms with a large probability.Research sponsored by the Air Force Office of Scientific Research (AFSC), United States Air Force, under Contract No. F49620-78-C-0005, and the National Science Foundation under Grant No. CHE77-27826. The United States Government is authorized to reproduce and distribute reprints for governmental purposes notwithstanding any copyright notation hereon.Alfred P. Sloan Research Fellow, 1976–1980; Camille and Henry Dreyfus Teacher-Scholar, 1975–1980.     

Kinetics and mechanism of the hydrolysis of sodium carboxymethylcellulose (Na-CMC) by a cellulase complex

TheSomogyi-Nelson colorimetric method is applied in a new manner more suitable for evaluating the kinetics of the enzyme hydrolysis of sodium carboxymethylcellulose (Na-CMC) catalyzed by the cellulase complex. By means of selective inhibition of a chosen enzyme from the cellulase complex it became possible to trace the effect of the other enzymes included in its composition.

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Kinetik und Mechanismus der Hydrolyse von Natriumcarboxymethylcellulose (Na-CMC) durch einen Cellulase-Komplex

Zusammenfassung Die kolorimetrische Methode nachSomogyi undNelson wird nach einem neuen Verfahren zur Verfolgung der Kinetik der hydrolytischen Spaltung von Natriumcarboxymethylcellulose (Na-CMC), katalysiert durch den Cellulase-Komplex, angewandt. Durch selektive Inhibierung eines bestimmten Enzyms des Cellulase-Komplexes kann man die Wirkung der anderen zu seiner gesamten Zusammensetzung gehörenden Enzyme verfolgen.

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Symbols Used E enzyme (Ew3508h3735x70768/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">—cellulase;Ew3508h3735x70768/xxlarge8243.gif" alt="Prime" align="MIDDLE" BORDER="0">—exo-cellobiohydrolase;Ew3508h3735x70768/xxlarge8244.gif" alt="tprime" align="MIDDLE" BORDER="0">—w3508h3735x70768/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-glucosidase) - [E] _w weight concentration of enzymeE - S substrate (Na-CMC—sodium carboxymethylcellulose) - [S]₀ weight concentration of substrateS - I inhibitor (Iw3508h3735x70768/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">—lactose;Iw3508h3735x70768/xxlarge8243.gif" alt="Prime" align="MIDDLE" BORDER="0">—calcium chloride;Iw3508h3735x70768/xxlarge8243.gif" alt="Prime" align="MIDDLE" BORDER="0">—condurrite-B-epoxide) - P product (Pw3508h3735x70768/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">—oligosaccharides;Pw3508h3735x70768/xxlarge8243.gif" alt="Prime" align="MIDDLE" BORDER="0">—cellobiose;Pw3508h3735x70768/xxlarge8244.gif" alt="tprime" align="MIDDLE" BORDER="0">—D-glucose) - P _{w3508h3735x70768/xxlarge8733.gif" alt="prop" align="MIDDLE" BORDER="0">} end product (K _{w3508h3735x70768/xxlarge8733.gif" alt="prop" align="MIDDLE" BORDER="0">} ^{w3508h3735x70768/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">} , K _{w3508h3735x70768/xxlarge8733.gif" alt="prop" align="MIDDLE" BORDER="0">} ^{w3508h3735x70768/xxlarge8243.gif" alt="Prime" align="MIDDLE" BORDER="0">} , K _{w3508h3735x70768/xxlarge8733.gif" alt="prop" align="MIDDLE" BORDER="0">} ^{w3508h3735x70768/xxlarge8244.gif" alt="tprime" align="MIDDLE" BORDER="0">} ) - DP degree of polymerization - DS degree of substitution - ES enzyme-substrate complex (Ew3508h3735x70768/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0"> S, Ew3508h3735x70768/xxlarge8243.gif" alt="Prime" align="MIDDLE" BORDER="0"> S, Ew3508h3735x70768/xxlarge8244.gif" alt="tprime" align="MIDDLE" BORDER="0"> S) - EP enzyme-product complex (Ew3508h3735x70768/xxlarge8243.gif" alt="Prime" align="MIDDLE" BORDER="0"> Pw3508h3735x70768/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">, Ew3508h3735x70768/xxlarge8244.gif" alt="tprime" align="MIDDLE" BORDER="0"> Pw3508h3735x70768/xxlarge8243.gif" alt="Prime" align="MIDDLE" BORDER="0">) - EI enzyme-inhibitor complex (Ew3508h3735x70768/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0"> Iw3508h3735x70768/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">, Ew3508h3735x70768/xxlarge8243.gif" alt="Prime" align="MIDDLE" BORDER="0"> Iw3508h3735x70768/xxlarge8243.gif" alt="Prime" align="MIDDLE" BORDER="0">, Ew3508h3735x70768/xxlarge8244.gif" alt="tprime" align="MIDDLE" BORDER="0"> Iw3508h3735x70768/xxlarge8244.gif" alt="tprime" align="MIDDLE" BORDER="0">) - M _s molecular mass of substrateS - K _s substrate constant (K _s ^{w3508h3735x70768/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">} , K _s ^{w3508h3735x70768/xxlarge8243.gif" alt="Prime" align="MIDDLE" BORDER="0">} , K _s ^{w3508h3735x70768/xxlarge8244.gif" alt="tprime" align="MIDDLE" BORDER="0">} ) - K _I inhibitor constant (K _I ^{w3508h3735x70768/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">} , K _I ^{w3508h3735x70768/xxlarge8243.gif" alt="Prime" align="MIDDLE" BORDER="0">} , K _I ^{w3508h3735x70768/xxlarge8244.gif" alt="tprime" align="MIDDLE" BORDER="0">} ) - K _m Michaelis-Menten constant - k ₊₁,k ₊₂ (k ₊₂ ^{w3508h3735x70768/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">} ,k ₊₂ ^{w3508h3735x70768/xxlarge8243.gif" alt="Prime" align="MIDDLE" BORDER="0">} ,k ₊₂ ^{w3508h3735x70768/xxlarge8244.gif" alt="tprime" align="MIDDLE" BORDER="0">} ) forward rate constants - k _–1 reverse rate constant - w3508h3735x70768/xxlarge957.gif" alt="ngr" align="BASELINE" BORDER="0"> ₀ initial rate of reaction - V maximal reaction rate - w3508h3735x70768/xxlarge916.gif" alt="Delta" align="BASELINE" BORDER="0">A change in absorbance - w3508h3735x70768/xxlarge949.gif" alt="epsi" align="BASELINE" BORDER="0"> molar absorption coefficient - w3508h3735x70768/xxlarge955.gif" alt="lambda" align="BASELINE" BORDER="0"> wavelength Herrn Prof. Dr.Hans Tuppy zum 60. Geburtstag herzlichst gewidmet.     

Photochemically induced fluorescence investigation of aβ-cyclodextrin: Azure A inclusion complex and determination of analytical parameters

The photooxidation of Azure A and fluorescence properties of Azure A and its photoproduct have been investigated in aqueous media and in the presence ofw330h5325n6/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin (w330h5325n6/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-CD). The fluorescence intensity of the complex formed between the photoproduct and w330h5325n6/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-CD was found to be three times higher than that of the uncomplexed Azure A photoproduct. A complex formation constant of 110±40 M^–1 was calculated using the Benesi-Hildebrand treatment of the fluorescence emission data. Although the stoichiometry of the Azure A photoproduct: w330h5325n6/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-CD complex was found to be 1: 1, it seems that the Azure A structure is only partially included. Calibration graphs were plotted for the free Azure A photoproduct and the photogenerated product included in w330h5325n6/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-CD. The analytical parameters and quantification limits were determined.     

Structure and conformational features of tetrahydrothienothiepinoisoxazole as a novel heterocyclic system

The crystal and molecular structure of a novel heterocyclic system, 8-methyl-3,3a,4,5-tetrahydrothieno[3w/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">,2:6,7]thiepino[4,5-c]isoxazole, has been determined by X-ray analysis. The seven-membered ring has the boat conformation (B), while the isoxazoline cycle has the flat chair conformation (₃E). There are strong steric strains between the vicinal protons at the C(3a), C(3), and C(4) atoms.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1795–1797, October, 1994.     

Uniform Rice-like CdS Particles Prepared from Water-in-oil Microemulsions

IntroductionNano-sized semiconductors are of great interestdue to their special optical and electronic proper-ties[1,2].As one of the mostimportantⅡ—Ⅵsemicon-ductors,CdS has importantapplications in many fields,such as the solar cell field,non linear o…     

In-capillary micro solid-phase extraction and capillary electrophoresis separation of heterocyclic aromatic amines with nanospray mass spectrometric detection

A miniaturised technique to analyse and detect heterocyclic aromatic amines (HAs) using micro solid-phase extraction (wypv00w/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">SPE) coupled on-line (in-capillary) to capillary electrophoresis (CE) separation with nanospray (nESI) mass spectrometry (MS) detection has been developed. HAs are mutagenic and carcinogenic compounds formed at low levels in protein-rich food during cooking. Due to the low concentrations of HAs and the high complexity of the matrix in which they exist, sensitive and selective analytical methods are required for quantification. wypv00w/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">SPE was performed on a packed bed of C₁₈ particles inside the CE capillary, which minimised the dead volume. The on-line coupling of SPE, CE and nESI-MS reduced the time for extraction and identification to less than half an hour, which will allow for screening of several samples per day. The new technique provides short analysis time, low sample and solvent consumption, and HAs in standard solutions were easily detected at 12–17 fmol injections, and in spiked urine samples at 750–810 fmol injections.