Refine
Year of publication
- 1973 (62) (remove)
Document Type
- Article (36)
- Part of Periodical (20)
- Review (2)
- Book (1)
- Part of a Book (1)
- Periodical (1)
- Working Paper (1)
Keywords
- Frankfurt <Main> / Universität (3)
- Hochschullehrer (2)
- Verzeichnis (2)
- Vorlesungsverzeichnis (2)
- 3,4-Benzopyrene (1)
- Bauer (1)
- Chlorophyll-a (1)
- Closener (1)
- Codex 250 (1)
- Coenzyme analogues (1)
Institute
The spectral properties of binary complexes of NAD-analogues and fragments therefrom with I.DH from pig heart or ADH from liver and yeast have been investigated. The NADH-analogues were modified by replacing adenine through benzimidazole, benzene or dihydronicotinamide. Additionally adenosine diphosphate ribose, dihydronicotinamide and dihydronicotinamide- ribose pyrophosphate-5"-ribose have been studied.
It has been shown by means of difference spectra that complexes between ADH from horse liver and analogues cause spectral changes in the region of aromatic absorption at 280 nm even when adenine is absent in the analogues. Spectral changes in the other enzymes mentioned are probably due to changes of the n-π* absorption of the adenine ring. The spectral changes upon complexing indicate hydrophobic interaction of the adenine with the enzyme protein. Fluorescence spectra vary in the intensity of the energy transfer band as well as in coenzyme emission depending on variation of the coenzym analogue. Changing of complex formation between protein and analogues at different pH-values are investigated. ADH from yeast, especially, shows a pK around 6 which suggests interaction with histidine imidazole.
Singlet oxygen (1Δg) was generated by a microwave discharge and bubbled through a solution of chlorophyll-a in dibutylphtalate at approximately 10-20 torr. It not only excited the dye to its first singlet state but also produced oxidized species which generated a very long lasting weak chemiluminescence. From quenching experiments for the generation of the excited species could computer simulation.
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 preparation of (CH3)3SnSPSFC2H5, Pb(SPSFCH3)2, Pb(SPSFC2H5)2 and CH3HgSPSFCH3 is described. On the basis of NMR the structure was formulated as ... All the complexes are colourless and monomeric in solution. The magnetic and reflectance spectra of Cr(S2PFCH3)3, Mn(S2PFC2H5)2, Co(S2PFCH3)2, Ni(S2PFCH3)2 and Ni(S2PFC2H5)2 are reported and interpreted.
R-P(Se)F2- (R = CH3, C2H5, C3H11, C6H5, N(CH3)2, N(C2H5)2, NHSi(CH3)3) and R-P(Se)FCl-compounds (R = CH3, C2H5) can be prepared by reaction of R-P(Se)Cl2-derivatives with antimony(III)fluoride under reduced pressure. In some cases the oxidation of fluorophophines with elemental selenium is successful. The isolated compounds are colourless volatile liquids which are sensitive to air and moisture. The chemical properties are described.
1H-, 19F-, 31P-NMR-, IR- and Raman-spectroscopic data are given. Main stretching frequencies are discussed by comparison with similar oxygen- and sulphur-compounds.
The photoelectron (PE) spectra of dicyano methane and of its dimethyl derivative are tentatively assigned on the basis of a simple MO model. The interactions defined therein between the two cyano groups as well as with the R2C-framework can be parametrized using the PE data. Thus the hyperconjugation πCN/πCR₂ is estimated to amount to 1.7 eV in both compounds. Hyperconjugative effects in methane derivatives H3CX and H2CX2 with X = Br, Cl and CN are compared.
This paper contains further applications on symmetrical liquid mixtures of the molecular thermodynamic theory which has been developped in part I of this series. The essential feature of this theory is the superposition of "chemical" and “random” exchange equilibria between “complexes” formed by a given molecule and its z nearest neighbours, thus allowing a unified treatment of the thermodynamic phenomena in binary liquid mixtures using the equilibrium constant K of the ideal law of mass action and the energy w of pair interactions as parameters.
The temperature and pressure dependences of K and the evaluation of experimental excess enthalpy and excess volume data are treated. Formulas and examples for the calculation of K and w from isothermal and non-isothermal vapour-liquid equilibrium data are given. The conditions for azeotropy with minimum or maximum vapour pressure, resp., are derived. Melting curves for a symmetric eutectic system with superposed miscibility gap are discussed. Further models for partially miscible liquids with competing self-association and complex-formation are treated showing the phenomenon of two separated miscibility gaps.
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.