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Excitation of CO molecules into the lowest vibrational level of the B1Σ+ electronic state by absorption of the (B 1Σ+υ′=0 →X 1Σ+ ,υ′′=0) resonance band at 1150 Å has been studied under various experimental conditions by observing the steady state fluorescence of the (B 1Σ+→A1Π) Angstrom bands. Stern-Volmer plots of the fluorescence intensities at the addition of various foreign gases yielded straight lines whose slopes k̃qм = kqм · τeff were strongly dependent on the CO sample pressure. This effect was found to be due to changes of the effective radiative lifetime of the B 1Σ+υ′=0 because of resonance trapping of the (0,0) band of the (B → X) fluorescence. The CO(B 1Σ+υ′=0) molecules are found to be quenched by He, Ne, Ar, H2 and D2 with effective collision cross sections of 0.23, 0.48, 22.4, 10.7, and 11.4 Å2, respectively, at 298 °K. In addition, an approximate value for the ratio ABA/ (ABA+ABX)of the radiative transition probabilities of the (B → A) and (B → X) transitions could be derived from the measurements.
The solvent dependence of the photooxidation of tryptophan and 3,4-benzopyrene in aqueous solutions was studied by quantum yield measurements. When the hydrocarbon is dissolved in aqueous solution of caffeine, the quantum yields indicate a 3,4-benzopyrene photosensitized tryptophan oxidation instead of a photocooxidation, which is indicated in aqueous solution of sodium dodecylsulfate. The same photosensitized oxidation as in caffeine solution is observed, when urea ( 6 m) is added to the soap solution, while the fluorescence and absorption spectra indicate no change in the solvation state of the hydrocarbon, comparable to the change from hydrophobic solubilization by the detergent to dipole — induced dipole complex solubilization by caffeine. It is concluded that the difference in the reaction pathways is caused by different solvation states of the excited or reacting oxygen. In the discussion of the results it is referred to reactions of inhibitors.
The cooperative problem for a lattice gas on a plane, square lattice and on a simple cubic lattice is solved by a system of two coupled, transcendental equations, derived by a combinatorial method, which describes a homogeneous or periodical particle density on the lattice as a function of the temperature and the chemical potential of the lattice-gas.
For the particle interaction a Hard-Core potential (nearest neighbour exclusion) with a soft long-range tail is assumed. The zero-component of the Fourier-transform of this long-range interaction part can be positive or negative.
The system of transcendental equations is solved by a graphic method. As a result, the complete pressure-density state diagram and the pressure-temperature phase diagram can be drawn.
The lattice-gas exists in three stable phases: gas, liquid and solid. Three phase changes are possible: condensation, crystallization and sublimation.
Critical points of condensation and freezing are examined. The number of possible phases and phase changes at a fixed temperature depends on the geometric structure of the particle interaction.
Spectrophotometric investigation of the kinetics of the spontaneous reduction of the central metal ion in K2[Mn (IV)-2-α-hydroxyethyl-isochlorine e4] acetate in aqueous alkaline solution in the absence of any reducing agent reveals that it is a pseudo-first order reaction which is specifically hydroxide ion catalyzed. The pKα-value of the acid-base equilibrium has been estimated to be 14.4.
Electron transfer to the central metal ion is the rate limiting step. The measurements of its temperature dependence yields an activation enthalpy of ∆H‡ = 12 kcal/mol and an entropy of activation ∆S‡ = - 30 e.u. thus indicating that the electron transfer step is a bimolecular reaction. The most likely reactant is water. The reduction reaction does not take place with appreciable reaction rates at physiological pH. Thus, when bound to a suitable ligand of the chlorin type, Mn (IV)-compounds are sufficiently stable with respect to autoxidation to play some role in biological redox reactions as postulated recently for the photoreactivation process of the water splitting system in photosynthesis.
A new NAD⊕-isomer was prepared, in which the ᴅ-ribose of the adenosine moiety was sub stituted by the enantiomeric ʟ-ribose. As compared to nicotinamide-adenine-dinucleotide (NAD⊕) and NADH the coenzyme isomer (ᴅ,ʟ)-NAD⊕ and its dihydroform (ᴅ,ʟ)-NADH are far less tightly bound to lactate dehydrogenase and alcohol dehydrogenase from horse liver. In the presence of the second substrate (ᴅ,ʟ)-NAD⊕ and (ᴅ,ʟ)-NADH act as hydrogen acceptor and hydrogen donator, respectively, with lactate dehydrogenase and alcohol dehydrogenases from horse liver and yeast. Compared to NAD⊕ and NADH the Michaelis constants are always increased, the catalytic constants (V/Et) were found to be decreased except for the dihydroform reacting with alcohol dehydrogenase from liver.
Sulfhydryl Groups, Methylmercury Containing Inactivator, Coenzyme Analogue Nicotinamide-(S-methylmercury-thioinosine) dinucleotide was formed by reaction of nicotin amide-(6-thiopurine) dinucleotide with methylmercury chloride. The compound exhibits coenzyme properties in the test with LDH (Km=1.5 × 10-4 м , Vmax=12500) and LADH (Km=1.7 × 10-4 м, Vmax=27) and inactivates YADH and GAPDH. From incubations with LDH and LADH the mercury containing coenzyme could be regained by column chromatography. The compound seems to be qualified for the X-ray structure analysis of the coenzyme-enzyme complex for some dehyrogenases based on the proportion of the heavy metal.
The mass spectrum and the ion molecule reactions of phosphirane and of mixtures of phosphirane with NH3 , NH2D, NHD2 and ND3 have been studied by ion cyclotron resonance spectrometry. Almost all important product ions are formed by PH-group transfer reactions, where ethene is generated as the neutral particle. Only two of the more abundant ions, the protonated molecule, H2P(CH2)2+ and the ion m/e=63, P2H+, are formed via other reaction pathways. Secondary, tertiary and quarternary product ions with the general formula R(PH)n+ (R: phosphirane fragment, n-1, 2, 3) have been detected.
The molecular ion is proved to have a cyclic structure. Two possible structures of the product ions with two and three phosphorus atoms are discussed: a structure with an open phosphorus chain, leaving the phosphirane ring intact and a ring extended structure, produced by a ring extension reaction of the PH-group.
Several rate constants of the ion molecule reactions of the phosphirane molecular ion are given.
Photoelectron (PE) spectra of ethylene and vinylene carbonates and thiocarbonates as well as of methylene trithiocarbonate and some open-chain derivatives are reported.
The low energy bands, well separated in the unsaturated compounds, are assigned to lone pair and π type ionizations. The assignment is based on comparison of PE spectra, modified CNDO calculations, and sulfur Κβ emission spectra. The pronounced substituent effects due to which the first ionization potential varies from 8.4 eV to 11.1 eV are discussed.
The low temperature IR stretching vibrations of difluorodisulfane (FSSF) and thiothionylfluoride (SSF2), in the solid phase and in a cyclohexane matrix, of the mixtures FSSF -SSF2, FSSF-OSF2 and SSF, -OSF2, and of solid difluorotrisulfane (FS3F) have been investigated. While SSF, forms no distinct oligomers, a dimer with absorption bands at 635 and 682 cm-1 has been detected in the case of FSSF. These differences between FSSF and SSF, are rationalized by the different S-F bond lengths. A structure of the FSSF dimer similar to that of the sulfur tetrafluoride dimer is proposed. The low temperature spectrum of FS3F shows 3 bands in the frequency range between 460 and 1000 cm-1: 590, 605 and 680 cm-1, due to associated molecules. FS3F decomposes on warming. The main decomposition products containing fluorine are FSSF and SSF2. Mechanisms for the rearrangement and decomposition of the three compounds studied are discussed.
The mass spectra and the ion molecule reactions of methylphosphine, dimethylphosphine and dimethyldeuterophosphine have been studied by ion cyclotron resonance spectrometry. About 50 ion molecule reaction are observed for each compound. The product ions can be classified as ions with two phosphorus atoms: P2R5+, P2R3+, P2R2+ and P2R+ (R = CH3 or H), as phosphonium and phosphinium ions and ions resulting from collision dissociations and charge exchange reactions. Tertiary ions with three phosphorus atoms like CH3P3H2+ (from CH3PH2) and (CH3)4P3H2 (from (CH3)2PH) have also been detected. The mechanisms of the ion molecule reactions, rearrangements, P -H- and C-H-reactivities and product ion structures are discussed, using in the case of dimethylphosphine the results obtained with the deuterated compound. Rate constants of formation of the more abundant product ions from the molecular ion and the CH3P+ ion, both odd electron particles, have been determined. The reactions with dimethylphosphine have much smaller rate constants than the reactions with methylphosphine.
Testosterone, Androst-4-en-3,17-dione, Enzyme Induction, S trep to m yces hydrogenans After cultivation of S trep to m yces hydrogenan s in the presence of 3H-labelled testosterone, radio active steroids were extracted separately from the cytosolic, ribosomal and cell wall-membrane fraction of the cells and from the culture medium, respectively.. The separation of the steroids was performed by one-and two-dimensional thin layer chromatography (TLC). The identification of the main metabolites was achieved by crystallization to constant specific radioactivity, specific staining procedures and acetylation. The oxidation of testosterone to androst-4-en-3,17-dione is by far the predominating reaction, which is almost finished after 3 h cultivation. Androst-4-en-3,17-dione is mainly transferred into the culture medium and partly accumulated within the cell wall-membrane fraction. High polar steroid metabolites and androstane derivatives are present in very small amounts only.
The kinetics of the photodynamic desactivation of lysozyme in presence of acridine orange as the sensitizer have been investigated in detail varying oxygen, protein, dye concentration, ionic strength and pH value. The kinetics can be approximately described as an over all pseudo-first- order rate process. Changing the solvent from water to D2O or by quenching experiments in presence of azide ions it could be shown that the desactivation of lysozyme is caused exclusively by singlet oxygen. The excited oxygen occurs via the triplet state of the dye with a rate constant considerably lower than that to be expected for a diffusionally controlled reaction. Singlet oxygen reacts chemically (desactivation, k=2.9 × 107 ᴍ-1 sec-1) and physically (quenching process, k = 4.1 × 108 ᴍ-1sec-1) with the enzyme. The kinetical analysis shows that additional chemical reactions between singlet oxygen and lysozyme would have only little influence on the kinetics of the desactivation as long as their products would be enzymatically active and their kinetical constants would be less than about 1 × 108 ᴍ-1 sec-1.
Two routes for the preparation of (CH3)2SnS2N2 are given, which are kinetically controlled reactions. The molecule (CH3)2SnS2N2 was characterized by X-ray analysis. It is an interesting starting material for the preparation of S2N2CO and S3N2O. The latter reacts with iminosulfur oxides and isocyanates under the formation of S3N3SO2F and S3N3SO2CF3. The structure of S3N3SO2F was established by X-ray analysis. The bonding properties are discussed.
The cleavage of thin-nitrogen derivatives with S3N2Cl2 yields also five membered sulfurnitrogen rings. The structure and properties of P3N3F5NS3N2 and C3N3F2NS3N2 are reported. Six, eight and ten membered rings are formed by the reactions of (CH3)3Si–N = S = N–Si (CH3)3 with FSO2–N=S=O, these are S4N4O2 and S5N5+S3N3O4, respectively. The cation S5N5+ is a planar molecule, while the oxygen containing species are puckered. In S4N4O2 the oxygens are attached to one sulfur atom, which has a tetrahedral configuration.
The structure of the silicon containing cyclic and bicyclic rings (CH3)2Si(NSN)2Si(CH3)2 and CH3Si(NSN)3SiCH3 were determined.
Antiserum against crystallized 20β-hydroxysteroid dehydrogenase from Streptomyces hydrogenans was used for different immunodiffusion and immunoprecipitation tests to quantify the bacterial enzyme in cell-free supernatants of the microorganism. After immunoprecipitation and gel electrophoresis the molecular weight of the subunits of 20β-hydroxysteroid dehydrogenase was calculated to be 27 300 ± 700.
The photodynamic deactivation of lysozyme in presence of acridine orange is caused by a reaction between singlet oxygen formed via the dye triplet state and the protein. In order to identify the region where the singlet oxygen reacts with the protein we have investigated the kinetics of the deactivation in presence ofthe inhibitor of the enzymatic reaction N-acetylglucosamine (GlcNAc). The overall experimental rate constant becomes slower with increasing saccharide concentrations. As we can exclude experimentally that this kinetical effect is caused in presence of the saccharide by a physical quenching of singlet oxygen or of the dye triplet state it has to be assumed that GlcNAc protects the surrounding of its bindings place at subsite C of the enzymatic center sterically against an attack of singlet oxygen. In this region three tryptophan residues are located, which could be sensitive against singlet oxygen. Surprisingly, however, it has been found that only those species are protected, in which a second saccharide molecule is bound to the protein, probably at subsite E at the enzymatic center, where no sensitive amino acid side chains are located.
The hypothesis of GLIKMAN and ZABRODA (Biochemistry [USSR] 84,, 239 [1969]) that the primary electron donor during photoreduction of manganese(III) in Mn(III)-hydroxychlorin compounds in oxygen free aqueous alkaline solutions is the axially bound OH- ion was tested with Mn(III)-2-a-hydroxyethyl-isochlorin e4. It has been shown that
1) the primary generation of OH radicals upon irradiation of the complex is highly improbable,
2) light is not essential for the reduction reaction,
3) the kinetics of photoreduction of the Mn(III)-compound in 2 N NaOH clearly is not compatible with OH radical formation.
In this paper equilibrium models for the calculation of the excess Gibbs free energy of binary liquid mixtures are developed, the component A of which undergoes chain-forming self-association whilst the component B acts as an 'inert' solvent. It is shown that the extension of the well-known chain-association model of Mecke and Kempter, in which the probability of chain prolongation is assumed to be independent of chain length, is unable to establish satisfactory results because it does not exhibit sufficient unsymmetry. Reduction of the probability of chain growth with in-creasing chain length leads to an improved model with the geometric series replaced by the exponential series. This model, in which only two parameters are used, i. e. the equilibrium constants K for mutual solvation of A and B, and ρ for self-association of A, allows fitting of isothermal experimental GE /R T literature data on cycloalkanol-cycloalkane, alkanol-alkane, and NMF -CCl4 systems within the limits of experimental error. Compared with the two-parameter Wilson equation which gives equally small standard deviations, our equilibrium model has the advantage of allowing passage from GE to HE data and of being applicable to liquid-liquid equilibria.
The gas phase ion chemistry of the simplest known phosphorus ylide, trimethylmethylenephosphorane, has been studied in the mass range m/e=2 - 186 and the pressure range 10-7-10-4 Torr. The most abundant product ion, m/e = 104, (CH3)2C2H5PCH2'+ is formed by a methylene group transfer reaction of the molecular ion. Almost all of the other product ions formed from the molecular ion can be subsumed under the general formula (CH3)3PCHPRn+ (R = H, CH3; n=1,2,3). The reactions indicate that the molecular ion has lost its ylide character almost completely. The protonated molecule is formed almost exclusively by a reaction of the fragment ion m/e = 75. This reaction and the CH3PH group transfer reaction indicate a cyclic structure (CH3) HP(CH2)2+ for this ion. A cyclic structure is also assumed for the ion m/e = 73, PC3H6+, which undergoes P and PH transfer reactions. The reactions of the ion m/e = 47 are consistent with the structure CH3PH+. The ICR and mass spectra are given, some metastable decompositions are discussed.