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  • 1
    Electronic Resource
    Electronic Resource
    Metal-.pi. complexes of benzene derivatives. 23. The radical anion of bis(.eta.6-benzene)chromium (1984)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 106 (1984), S. 4297-4299 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00327a056
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  • 2
    Electronic Resource
    Electronic Resource
    Differential expression of enzyme activities initiating anoxic metabolism of various aromatic compounds via benzoyl-CoA (1991)
    Springer
    Archives of microbiology 155 (1991), S. 256-262 
    Details
    ISSN: 1432-072X
    Keywords: Aromatic compounds ; Anaerobic aromatic metabolism ; Pseudomonas K 172 ; Phenol ; 4-Hydroxybenzoate ; p-Cresol ; Phenylacetate ; Benzoate ; Coenzyme A thioester
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The regulation of the expression of enzyme activities catalyzing initial reactions in the anoxic metabolism of various aromatic compounds was studied at the whole cell level in the denitrifying Pseudomonas strain K 172. The specific enzyme activities were determined after growth on six different aromatic substrates (phenol, 4-hydroxybenzoate, benzoate, p-cresol, phenylacetate, 4-hydroxyphenylacetate) all being proposed to be metabolized anaerobically via benzoyl-CoA. As a control cells were grown on acetate, or aerobically on benzoate. The expression of the following enzyme activities was determined. “Phenol carboxylase”, as studied by the isotope exchange between 14CO2 and the carboxyl group of 4-hydroxybenzoate; 4-hydroxybenzoyl-CoA reductase (dehydroxylating); p-cresol methylhydroxylase; 4-hydroxybenzyl alcohol dehydrogenase; 4-hydroxybenzaldehyde dehydrogenase; coenzymeA ligases for the aromatic acids benzoate, 4-hydroxybenzoate, phenylacetate, and 4-hydroxyphenylacetate; phenylglyoxylate: acceptor oxidoreductase and 4-hydroxyphenylglyoxylate: acceptor oxidoreductase; aromatic alcohol and aldehyde dehydrogenases. The formation of most active enzymes is strictly regulated; they were only induced when required, the basic activities being almost zero. The observed whole cell regulation pattern supports the postulate that the enzyme activities play a role in anoxic aromatic metabolism and that the compounds are degraded via the following intermediates: Phenol → 4-hydroxybenzoate → 4-hydroxybenzoyl-CoA → benzoyl-CoA; 4-hydroxybenzoate → 4-hydroxybenzoyl-CoA → benzoyl-CoA; benzoate → benzoyl-CoA; p-cresol → 4-hydroxybenzaldehyde → 4-hydroxybenzoate → 4-hydroxybenzoyl-CoA → benzoyl-CoA; phenylacetate → phenylacetyl-CoA → phenylglyoxylate → benzoyl-CoA plus CO2; 4-hydroxyphenylacetate → 4-hydroxyphenylacetyl-CoA → 4-hydroxyphenylglyoxylate → 4-hydroxybenzoyl-CoA plus CO2 → benzoyl-CoA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00252209
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  • 3
    Electronic Resource
    Electronic Resource
    Purification of glutaryl-CoA dehydrogenase from Pseudomonas sp., an enzyme involved in the anaerobic degradation of benzoate (1993)
    Springer
    Archives of microbiology 159 (1993), S. 174-181 
    Details
    ISSN: 1432-072X
    Keywords: Glutaryl-CoA dehydrogenase ; Glutaconyl-CoA decarboxylase ; Pseudomonas sp. ; Phototrophic proteobacteria ; Anaerobic degradation of benzoate ; FAD ; Ferricenium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cell-free extracts of Pseudomonas sp. strains KB 740 and K 172 both contained high levels of glutaryl-CoA dehydrogenase when grown anaerobically on benzoate or other aromatic compounds and with nitrate as electron acceptor. These aromatic compounds have in common benzoyl-CoA as the central aromatic intermediate of anerobic metabolism. The enzymatic activity was almost absent in cells grown aerobically on benzoate regardless whether nitrate was present. Glutaryl-CoA dehydrogenase activity was also detected in cell-free extracts of Rhodopseudomonas, Rhodomicrobium and Rhodocyclus after phototrophic growth on benzoate. Parallel to the induction of glutaryl-CoA dehydrogenase as measured with ferricenium ion as electron acceptor, an about equally high glutaconyl-CoA decarboxylase activity was detected in cell-free extracts. The latter activity was measured with the NAD-dependent assay, as described for the biotin-containing sodium ion pump glutaconyl-CoA decarboxylase from glutamate fermenting bacteria. Glutaryl-CoA dehydrogenase was purified to homogeneity from both Pseudomonas strains. The enzymes catalyse the decarboxylation of glutaconyl-CoA at about the same rate as the oxidative decarboxylation of glutaryl-CoA. The green enzymes are homotetramers (m=170 kDa) and contain 1 mol FAD per subunit. No inhibition was observed with avidin indicating the absence of biotin. The N-terminal sequences of the enzymes from both strains are similar (65%).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00250279
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  • 4
    Electronic Resource
    Electronic Resource
    Two N 5, N 10-methylenetetrahydromethanopterin dehydrogenases in the extreme thermophile Methanopyrus kandleri: characterization of the coenzyme F420-dependent enzyme (1993)
    Springer
    Archives of microbiology 160 (1993), S. 186-192 
    Details
    ISSN: 1432-072X
    Keywords: Coenzyme F420 ; Tetrahydromethanopterin ; Hydrogenase ; H2-forming methylenetrahydromethanopterin dehydrogenase ; Methanobacterium thermoautotrophicum ; Methanosarcina barkeri ; Archaeoglobus fulgidus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It was recently reported that the extreme thermophile Methanopyrus kandleri contains only a H2-forming N 5, N 10-methylenetetrahydromethanopterin dehydrogenase which uses protons as electron acceptor. We describe here the presence in this Archaeon of a second N 5,N 10-methylenetetrahydromethanopterin dehydrogenase which is coenzyme F420-dependent. This enzyme was purified and characterized. The enzyme was colourless, had an apparent molecular mass of 300 kDa, an isoelectric point of 3.7±0.2 and was composed of only one type of subunit of apparent molecular mass of 36 kDa. The enzyme activity increased to an optimum with increasing salt concentrations. Optimal salt concentrations were e.g. 2 M (NH4)2SO4, 2 M Na2HPO4, 1.5 M K2HPO4, and 2 M NaCl. In the absence of salts the enzyme exhibited almost no activity. The salts affected mainly the V max rather than the K m of the enzyme. The catalytic mechanism of the dehydrogenase was determined to be of the ternary complex type, in agreement with the finding that the enzyme lacked a chromophoric prosthetic group. In the presence of M (NH4)2SO4 the V max was 4000 U/mg (k cat=2400 s-1) and the K m for N 5,N 10-methylenetetrahydromethanopterin and for coenzyme F420 were 80 μM and 20 μM, respectively. The enzyme was relatively heat-stable and lost no activity when incubated anaerobically in 50 mM K2HPO4 at 90°C for one hour. The N-terminal amino acid sequence was found to be similar to that of the F420-dependent N 5, N 10-methylenetetrahydromethanopterin dehydrogenase from Methanobacterium thermoautotrophicum, Methanosarcina barkeri, and Archaeoglobus fulgidus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249123
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  • 5
    Electronic Resource
    Electronic Resource
    Migration von Zinnstabilisatoren aus PVC-Flaschen in Bier (1971)
    Springer
    European food research and technology 147 (1971), S. 8-10 
    Details
    ISSN: 1438-2385
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Description / Table of Contents: Zusammenfassung Das Ausmaß der Migration von Organozinnverbindungen aus PVC-Flaschen, die mit 1,13% Di-n-octylzinn-bis(thioglykolsäure-2-äthylhexylester) stabilisiert waren, in Bier wurde untersucht. Nach achtwöchiger Lagerung bei 20°C enthielt das Bier 0,0017 mg/l Zinn (entsprechend 0,01 mg/l des verwendeten Stabilisators) und lag damit weit unter dem von der American Food und Drug Administration gesetzten Limit von 1 mg/l Stabilisator (entsprechend 0,16 mg/l Zinn).
    Notes: Summary The extent of migration of organotin compounds from PVC-bottles into beer was determined. Beer which had been stored at 20° C for 8 weeks in bottles stabilized with 1.13% di-n-octyltin-bis(2-ethyl hexyl thioglycolate) showed to contain 0.0017 mg/l of tin which equals 0.01 mg/l of the used stabilizer. This is far below the limit of 1 mg/l of stabilizer (0.16 mg/l of tin) permitted by the American Food and Drug Administration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01454290
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  • 6
    Electronic Resource
    Electronic Resource
    Expression of tenascin and fibronectin in the rabbit cornea after excimer laser surgery (1992)
    Springer
    Graefe's archive for clinical and experimental ophthalmology 230 (1992), S. 178-183 
    Details
    ISSN: 1435-702X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to investigate the effects of excimer laser surgery on corneal wound healing, 25 rabbits underwent anterior keratectomy at a depth of 100 or 300 μm with a Meditec MEL 50 excimer laser. After various intervals the animals were killed and the cornea excised and investigated immunohistochemically for the expression of extracellular matrix (ECM) proteins, fibronectin and tenascin. Fibronectin was shown to occur earlier than tenascin, and the two also had different distribution patterns. Wound depth showed no clear effect on the localization and time of ECM protein expression. This study indicates that corneal wounds caused by excimer laser radiation and those caused by mechanical surgery differ as to healing mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00164660
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  • 7
    Electronic Resource
    Electronic Resource
    Alkoxygermanate(II), -stannate(II) und -plumbate(II) zweiwertiger Metall-Ionen, II. Verbindungen des Formeltyps M2El2(OtBu)8 (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1033-1042 
    Details
    ISSN: 0009-2940
    Keywords: Germanium compounds ; Tin compounds ; Lead compounds ; Transition-metal complexes ; Paramagnetism ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkoxygermanates(II), -stannates(II), and -plumbates(II) of Divalent Metal Ions, II[1]. - Compounds of the Formula M2El2(OtBu)8By simple salt-exchange processes the starting materials Na2El2(OtBu)6 (El = Ge, Sn, Pb) can be transformed to germanates, stannates and plumbates of divalent magnesium and divalent transition metals. Two types of compounds are formed in these reactions: MEl2(OtBu)6 [El = Ge, M = Mg (1A), Cr (1B), Mn (1C), Zn (1F); El = Pb, M = Mn (3C), M = Zn (3F)] and M2El2(OtBu)8 [El = Ge, M = Co (1d), Ni (1e); El = Sn, M = Mg (2a), Cr (2b), Mn (2c), Co (2d), Ni (2e); El = Pb, M = Co (3d)]. Single-crystal X-ray diffraction studies have been performed on 1C, 1d, 2a, 2b, 2c, 2d, and 2e, and the structures have been solved. In 1C the Mn atom occupies the center of an elongated O6 octahedron, the germanium(II) atoms displaying pyramidal coordination by three oxygen atoms. The central molecular cage can be described as two MnO3Ge trigonal bipyramids sharing the common central Mn atom and being wrapped by tert-butyl groups linked to the oxygen atoms. The other compounds of the MEl2(OtBu)6 formula seem to be isostructural with the exception of 3F, which displays a 1H-NMR spectrum which is not compatible with this structure. All X-ray structures of the compounds M2El2(OtBu)8 show the same feature: to a central M2(OtBu)2 four-membered ring are spirocyclically connected two M(OtBu)2El rings through the common metal atoms M. The structure is completed by the coordination of an exocyclic tert-butoxy group to the terminal El atoms. The metal atoms M are therefore quasi tetrahedrally coordinated while the Ge and Sn atoms are in pyramidal threefold oxygen atom environments. All molecules display an El⃛M⃛M⃛El one-dimensional arrangement. From susceptibility measurements it is apparent, that in the compounds MEl2(OtBu)6 and M2El2(OtBu)8 the transition metal atoms are in high-spin configurations, which is also supported by the UV spectra. Analysis of the structural data of the series 2a-2e reveal important contributions of the electronic environments of the transition metal atoms to the M⃛M and M⃛Sn distances. A qualitative MO description is used to explain these features. Again it has been shown that the, „geometrical softness“ of Ge(OtBu)3 and Pb(OtBu)3 is greater than of Sn(OtBu)3, as the former two can accomodate Cr2+ and Mn2+ in a sixfold coordination site by two units, while Sn(OtBu)3 coordinates Cr2+ and Mn2+ with only two alkoxy groups. When 1C and 2d are allowed to react with nonacarbonyldiiron Mn-Ge2(OtBu)6 · 2 Fe(CO)4 (4) and Co2Sn2(OtBu)8 · 2 Fe(CO)4 (5), respectively, are formed. Compound 4 displays presumably five metal atoms in a linear arrangement while 5 has six metallic elements arranged in one dimension. The latter fact has been unambigously proved by an X-ray structure determination.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250509
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  • 8
    Electronic Resource
    Electronic Resource
    Metall-π-Komplexe von Benzolderivaten, 50Part 49: Ref.‘1’.. Arylborane als Sandwichliganden: Darstellung von [(iPrO)2B(η6-Ph)]2M und [Mes2B(η6-Ph)]2M (M = V, Cr). Redoxeigenschaften und EPR Untersuchung M(d5)-konfigurierter Neutralkomplexe sowie Bor-zentrierter Radikalanionen (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 871-878 
    Details
    ISSN: 0009-2940
    Keywords: Bis(arene)metal complexes ; Borane, dimesitylphenyl- ; Borane, diisopropylphenyl- ; Cyclic voltammetry ; EPR spectroscopy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metal π Complexes of Benzene Derivatives, 50. - Arylboranes as Sandwich Ligands: Preparation of [(iPrO)2B(η6-Ph)]2M and [Mes2B(η6-Ph)]2M (M = V, Cr). Redox Properties and EPR Study of M(d5) Neutral Complexes and Boron-Centered Radical AnionsBis(η6-arene)metal complexes bearing peripheral boryl substituents have been prepared by means of metal-atom ligand-vapor cocondensation leading to [(iPrO)2B-η6-C6H5]2Cr (7) and [(iPrO)2B-η6-C6H5]2V (8) as well as by lithiation and subsequent reaction with Mes2BF with formation of [Mes2B-η6-C6H5]2Cr (11) and [Mes2B-η6-C6H5]2V (12). According to the NMR spectra, rotation about the η-C-BR2 bonds in 7 and 11 is free at 25°C, restrictions setting in at -85°C. The neutral radicals 8• and 12• have been studied by EPR spectroscopy: despite of the profound difference in the electron-accepting properties of the groups (iPrO)2B- and Mes2B, the hyperfine coupling constants a(51V) differ by 5% only; the extent of perturbation of the electronic structure manifests itself more clearly in the g tensor, which is tetragonal for 8 but orthorhombic for 12, the degeneracy of the LUMO's e1g being raised in the latter. Cyclovoltammetry on 11 exhibits reversible oxidation as well as reduction processes. Reduction which, according to EPR, is ligand-centered, occurs in two steps which are separated by the redox splitting ΔE1/2 = 570 mV. This value, which is a measure of electronic communication between the two Mes2B groups, lies between those of 1,4-bis(dimesitylboryl)benzene (δE1/2 = 690 mV) and 4,4′-bis(dimesitylboryl)biphenyl (ΔE1/2 = 270 mV). The EPR spectrum of the radical anion 11-• reveals hyperfine coupling to one boron nucleus of a magnitude very similar to that of the free ligand radical anion Mes2BC6H5-•. Therefore, reduction of 11 is ligand-centered, and an intramolecular electron exchange between the boron centers is slow on the EPR time scale. As inferred from the observation of the hyperfine interactions a(53Cr) and a(1H), oxidation of 11 is metal-centered; relative to parent bis(η6-benzene)chromium (9), the two Mes2B groups cause an anodic shift of 290 mV for the couple 11+/0. The radical cations 11+• are prone to protodeborylation, in this aspect resembling the respective silyl derivatives.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961290721
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  • 9
    Electronic Resource
    Electronic Resource
    Polymeres (Dihydrodibenzo[b,i]-1,4,8,11-tetraaza-[14]annulen)eisen(II) mit Pyrazin-Brücken (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 2109-2114 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Polymeric (Dihydrodibenzo[b,i]-1,4,8,11-tetraazal[14]annulene)iron(II) with Pyrazine Bridges5,14-Dihydrodibenzo[b,i][1,4,8,11]tetraazacyclotetradecin (H2taa) (3) and ferrous acetate reacts in the presence of pyridine via the pyridine complex 4 to form Fetaa (5). If 5 is reacted with pyrazine under various conditions, the pyrazine bridged polymer 6 is formed as the only product. The instable monomer 7 could not be isolated. The polymer 6 shows a conductivity of 1·10-5 S·cm-1 at room temperature which is 107 times higher than that of 5.
    Notes: 5,14-Dihydrodibenzo[b,i][1,4,8,11]tetraazacyclotetradecin (H2taa) (3) reagiert mit Eisen(II)-acetat in Gegenwart von Pyridin über den Pyridinkomplex 4 zu Fetaa (5). Mit Pyrazin entsteht aus 5 unter verschiedenen Bedingungen nur das Pyrazin-überbrückte Polymere 6, während das instabile Monomere 7 nicht isoliert werden kann. Gegenüber 5 zeigt das Polymere 6 mit 1·10-5 S·cm-1 eine um 107 erhöhte Dunkelleitfähigkeit bei Raumtemperatur.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160607
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  • 10
    Electronic Resource
    Electronic Resource
    Monomere und überbrückte (2,3,9,10- Tetramethyl- 1,4,8,11-tetraaza-1,3,8,10-cyclotetradecatetraen)eisen(II)-Komplexe mit diaxialen Liganden (1987)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1853-1862 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Monomeric and Bridged (2,3,9,10-Tetramethyl-1,4,8,11-tetraaza-1,3,8,10-cyclotetradecatetraen)iron(II) Complexes with Diaxial LigandsThe reaction of [FeTIM(CH3CN)2](PF6)2 (5) with mono- and bidentate ligands L, e. g. pyridine (py), substituted pyridines, 4,4′-bipyridine (bpy), 1,4-diisocyanobenzene (dib), pyrazine (pyz), 4-cyanopyridine (4-pyCN), imidazole (imH), 1,2,4-triazole (triH), yields the iron(II) complexes of 2,3,9,10-tetramethyl-1,4,8,11-tetraaza-1,3,8,10-cyclotetradecatetraene (TIM) [FeTIM(L)2](PF6)2 (6a-u). The bridged complexes 8a-e (e. g. [FeTIM(μ-pyz)- (H2O)]n(PF6)2n (8a)) were obtained with the ligands pyz, bpy, dib, 4-pyCN and 4-isocyanopyridine (pyNC). Similarly, with L = imH, triH, and tetrazole (tetH), the bridged complexes 10a-c, e. g. [FeTIM(μ-im)]n(PF6)n (10a), were formed.
    Notes: Durch Umsetzung von [FeTIM(CH3CN)2](PF6)2 (5) mit ein- und zweizähnigen Liganden L, z. B. Pyridin (py), substituierte Pyridine, 4,4′-Bipyridin (bpy), 1,4-Diisocyanbenzol (dib), Pyrazin (pyz), 4-Cyanpyridin (4-pyCN), Imidazol (imH), 1,2,4-Triazol (triH), wurden die monomeren Eisen(II)-Komplexe von 2,3,9,10-Tetramethyl-1,4,8,11-tetraaza-1,3,8,10-cyclotetradecatetraen (TIM) [FeTIM(L)2](PF6)2 (6a-u) erhalten. Mit den Liganden pyz, bpy, dib, 4-pyCN, 4-Isocyanpyridin (pyNC) konnten auch die verbrückten Komplexe 8a-e (z. B. [FeTIM(μ-pyz)- (H2O)]n(PF6)2n (8a)) gewonnen werden. Mit L = imH, triH und Tetrazol (tetH) wurden die verbrückten Verbindungen 10a-c, z. B. [FeTIM(μ-im)]n(PF6)n (10a) erhalten.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19871201113
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