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  • 1
    Electronic Resource
    Electronic Resource
    Voltage-dependent inhibition of the sodium pump by external sodium: Species differences and possible role of the N-terminus of the α-subunit (1993)
    Springer
    European biophysics journal 21 (1993), S. 433-443 
    Details
    ISSN: 1432-1017
    Keywords: Na-Pump current-voltage relationship ; Na dependence ; Access channel ; N-Terminus truncation ; (Xenopus oocyte)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Currents generated by the Na+/K+ ATPase were measured under voltage clamp in oocytes of Xenopus laevis. The dependence of pump current on external [Na+] was investigated for the endogenous Xenopus pump as well as for wild-type and mutated pumps of electroplax of Torpedo californica expressed in the oocytes. The mutants had α-subunits truncated before position Lys28 (αΔK28) or Thr29 (αΔT29) of the N-terminus. The currents generated by all variants of pump molecules in the presence of 5 mM K+ show voltage-dependent inhibition by external [Na+]. The apparent K1 values increase with membrane depolarisation, and the potential dependence can be described by the movement of effective charges in the electrical potential gradient across the membrane. Taking into account Na+-K+ competition for external binding to the E2P form, apparent K1 values and effective charges for the interaction of the Na+ ions with the E2P form can be estimated. For the Xenopus pump the effective charge amounts to 1.1 of an elementary charge and the K1 value at 0 mV to 44 mM. For the wild-type Torpedo pump, the analysis yields values of 0.73 of an elementary charge and 133 mM, respectively. Truncation at the N-terminus removing a lysinerich cluster of the a-subunit of the Torpedo pump leads to an increase of the effective charge and decrease of the K1 value. For αΔK28, values of 0.83 of an elementary charge and 117 mM are obtained, respectively. If LyS28 is included in the truncation (α·T29), the effective charge increases to 1.5 of an elementary charge and the apparent K1 value is reduced to 107 mM. The K, values for pump inhibition by external Na+, calculated by taking into account Na+-K+ competition, are smaller than the K/12 values determined in the presence of 5 mM [K+]. The difference is more pronounced for those pump variants that have higher Km, values. The variations of the parameters describing inhibition by external [Na+] are qualitatively similar to those described for the stimulation of the pumps by external [K+] in the absence of extracellular [Na+]. The observations may be explained by an acess channel within the membrane dielectric that has to be passed by the external Na+ and K+ ions to reach or leave their binding sites. The potential-dependent access and/or the interaction with the binding sites shows species differences and is affected by cytoplasmic lysine residues in the N-terminus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185871
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  • 2
    Electronic Resource
    Electronic Resource
    1,3-Dialkyldiazetidin-2,4-dione Struktur und Molekülspektren (1977)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 110 (1977), S. 1130-1139 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,3-Dialkyldiazetidin-2,4-diones Structure and Molecular Spectra1,3-Dimethyl- (1) and 1,3-diethyldiazetidin-2,4-dione (2) are prepared by reaction of the corresponding isocyanates with antimony(V) chloride. The vibrational spectra are discussed. The crystal and molecular structure of 1 and the 1H n. m. r. data of 1 and 2 are reported.
    Notes: 1,3-Dimethyl- bzw. 1,3-Diethyldiazetidin-2,4-dion (1) bzw. (2) werden aus den entsprechenden Isocyanaten und Antimon(V)-chlorid dargestellt. Die Schwingungsspektren werden diskutiert, Daten zur Kristall- und Molekülstruktur von 1 sowie die 1H-NMR-Daten von 1 und 2 mitgeteilt.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19771100335
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  • 3
    Electronic Resource
    Electronic Resource
    Dediazoniation of Arenediazonium Ions in Homogeneous Solutions. Part XVI. Kinetics and mechanisms of dediazoniation of p-chlorobenzenediazonium tetrafluoroborate in weakly alkaline aqueous solutions under nitrogen gasPart XV: s. [1]. (1981)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 513-528 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of reactions of p-chlorobenzenediazonium ions in aqueous buffer solutions (pH 9.0-10.6) under N2 (〈 5 ppb of O2) have been measured between 20 and 50°C. The formation of trans-diazotate is first-order with respect to the concentration of hydroxyl ions and to the equilibrium concentration of diazonium ions, if the diazonium ion⇄cis-diazotate equilibrium is considered as a fast prior equilibrium. This indicates that the p-chlorobenzenediazonium ion, in contrast to all previous investigations with the p-nitrobenzenediazonium ion and benzenediazonium ions carrying similar substituents with a -M effect, rearranges from the cis- to the trans-configuration as diazohydroxide and not as diazotate. The formation of trans-diazotate is catalyzed by carbonate and inhibited by hydrogen carbonate ions; mechanisms of these catalyses are discussed, and the solvent isotope effect KH2O/KD2O measured by an 1H-NMR. technique reported. The kinetics of the dediazoniations can be analyzed as a mixture of two reactions, a relatively fast first reaction, reaction A, which is responsible for about 5% of the total reaction, and a second reaction F. Both are first-order with respect to diazonium ion; reaction A is also first-order in hydroxyl ions. There are some indications that reaction A corresponds to the hydrolysis of the diazonium ion to give eventually amine and nitrite ions. Reaction F shows a complex dependence on hydroxyl ions; it is related to the homolytic dediazoniation.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19810640216
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  • 4
    Electronic Resource
    Electronic Resource
    Dediazoniations of Arenediazonium Ions in Homogeneous Solution. Part XIV. 15N-CIDNP. Investigation of the reactions of diazonium ions in weakly alkaline aqueous solutionsPresented at the 5th IUPAC Conference on Physical Organic Chemistry, Santa Cruz (Cal.), August 1980. For part XIII: see [1]. (1981)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 488-503 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 15N-CIDNP. spectra recorded during the reaction of diazonium cations with OH- in weakly alkaline aqueous solutions show that the dediazoniation is at least partially homolytic. The polarizations observed for the diazonium and trans-diazotate ions can be explained by reaction proceeding via a cage involving diazenyl and diazotate radicals using Kaptein's rules and simple intensity considerations.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19810640214
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  • 5
    Electronic Resource
    Electronic Resource
    Dediazoniations of Arenediazonium Ions in Homogeneous Solutions. Part XV. Products of dediazoniation of p-chlorobenzenediazonium tetrafluoroborate in weakly alkaline aqueous solutionsFor part XIV, s. [1]. (1981)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 504-512 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The products of decomposition of solutions of p-chlorobenzenediazonium tetrafluoroborate in aqueous buffer solutions (pH 9.0-10.3; ionic strength 0.1-0.5) at 20.0° have been analyzed quantitatively. Up to eleven low molecular weight compounds could be identified besides the major product, the complex polymeric diazo tar. The distribution of products is influenced by trace amounts of oxygen as well as by p-chlorophenol and the radical trapping reagent iodoacetic acid. Mechanisms of formation of the products are discussed.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19810640215
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  • 6
    Electronic Resource
    Electronic Resource
    Über die Synthese von 1,1′-Bicyclobutyl- und 1,1′-Bicyclohexyl-Derivaten (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 2554-2563 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of 1,1′-Bicyclobutyl and 1,1′-Bicyclohexyl DerivativesDimeric glycols (2, 3 and 20, 24) are prepared from ethyl 3-oxocyclobutanecarboxylate (1) and 4-substituted cyclohexanone derivatives 9, 10, 23 by low valent titanium reagents. Dimeric olefins (17, 18) were obtained from the cyclohexanones by Barton's thiadiazoline method. Some experiences with cis-protecting groups for the 1,1′-dihydroxy dimers are presented.
    Notes: Aus dem 3-Oxocyclobutancarbonsäure-ethylester (1) und 4-substituierten Cyclohexanonen 9, 10, 23 werden mit niederwertigem Titan die dimeren Glycole 2, 3 bzw. 20, 24 hergestellt, aus den Cyclonexanonen mit Bartons Thiadiazolin-Methode auch die dimeren Olefine 17, 18. Einige Erfahrungen mit den Schutzgruppen zur cis-Fixierung der 1,1′-Dihydroxy-Dimeren werden mitgeteilt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160714
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis and Characterization of Substituted Benzyl Zinc Derivatives - Molecular Structures of (tmeda) Li-CH (GeMe3)Ph, (tmeda)Zn(CH2Ph)2, (tmeda)Zn[CH(SiMe3)Ph]2, and (tmeda)Zn[CH(SiMe3)Ph]N(H)Si(SiMe3)3Dedicated to Professor Manfred Weidenbruch on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1499-1505 
    Details
    ISSN: 0009-2940
    Keywords: Lithium ; Zine ; Dibenzylzinc ; Tmeda complexes ; Heteroleptic alkylzinc amide ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of lithium phenyl(trimethylsilyl)methanide with phenyl(trimethylsilyl)methylzinc chloride-tmeda in the presence of tmeda yields the addition product, a bis(tmeda)-lithium dialkylchlorozincate. The elimination of lithium chloride leads to the formation of a tmeda adduct of bis[phenyl-(trimethylsilyl)methyl]zinc. The metathesis reaction of phenyl(trimethylsilyl)methylzinc chloride-tmeda with lithium tris(trimethylsilyl)silylamide allows the isolation of the corresponding heteroleptic tmeda complex of an alkylzinc amide. The metalation of phenyl(trimethylstannyl)methane with butyllithium yields the transmetalation product benzyllithium. From the metathesis reaction of this lithium base with anhydrous zinc(II) chloride in the presence of tmeda, the tmeda adduct of dibenzylzinc crystallizes. The molecular structures of (tmeda)Li—CH(GeMe3)Ph, (tmeda)Zn(CH2Ph)2, (tmeda)Zn[CH(SiMe3)Ph]2, and (tmeda)Zn[CH(SiMe3)-Ph[N(H)Si(SiMe3)3 are reported. Whereas lithium bonds in an η3-fashion, the zinc atom forms a σ(Zn—C) bond. The extremely wide Zn—N—Si angle in (tmeda)Zn[CH(SiMe3)-Ph[N(H)Si(SiMe3)3 of 157° is remarkable.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301024
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  • 8
    Electronic Resource
    Electronic Resource
    Hydrogenolyse kleiner Kohlenstoffringe, XV über die Hydrierung von Dispiro[2.2.2.2]deca-4,9-dien (1987)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 435-438 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On hydrogenation of the title compound 1 with Pd/C 1,4-diethylbenzene (2) is formed in 95% yield, furthermore 1% of cis- and 2% of trans-1,4-diethylcyclohexane (3 und 4) as well as 2% of 6-ethylspiro[2.5]octane (15) are found. With Pt/C the intermediates 7, 12, 13, and 14 and up to 45% of dispiro[2.2.2.2]decane (17) are identified. 17 is hydrogenated with PtO2 in acetic acid to form 1,1,4,4-tetramethylcyclohexane (19).
    Notes: Bei der Hydrierung der Titelverbindung 1 mit Pd/C entsteht zu 95% 1,4-Diethylbenzol (2), daneben noch ca. 1% cis- und 2% trans-1,4-Diethylcyclohexan (3 und 4) sowie 2% 6-Ethylspiro-[2.5]octan (15). Mit Pt/C wird zusätzlich (bis zu 45%) Dispiro[2.2.2.2]decan (17) gebildet, und man erkennt die Zwischenstufen 7, 12, 13 und 14. Mit PtO2 in Eisessig wird 17 weiter zu 1,1,4,4-Tetramethylcyclohexan (19) hydriert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19871200330
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis and Dynamic Behavior of the Dimeric, Monocyclic Barium Bis[bis(isopropyldimethylsilyl)phosphanide] - Molecular Structures of P(SiMe2Ph)3, of Monomeric (thf)4Ba[P(SiMe2iPr)2]2 and of the Dimer {(thf)2Ba[P(SiMe2iPr]2]2}2 (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1035-1040 
    Details
    ISSN: 0009-2940
    Keywords: Phosphanes ; Bis(silyl)phosphanes ; Tris(silyl)phosphanes ; Phosphanides ; Barium bis(phosphanide) ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Barium bis[bis(trimethylsily)amide] metalates bis(isopropyldimethylsilyl)phosphane (1) to yield nearly quantitatively the corresponding barium bis[bis(isopropyldimethylsilyl)phosphanide] (3). This compound shows a temperature-dependent monomer-dimer equilibrium in toluene solution. Both the isomers were characterized by X-ray crystal structure analyses. The monomeric derivatives precipitate as a tetrakis(tetrahydrofuran) complex with a P-Ba-P bond angle of 139.9°. The barium atoms of the monocyclic, centrosymmetric dimer are pentacoordinated by two tetrahydrofuran molecules, one terminal and two bridging phosphanide ligands. The endo- and exocyclic Ba-P distances with values of 332 and 316 pm, respectively, lie within the characteristic range.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961290910
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  • 10
    Electronic Resource
    Electronic Resource
    Photoelektronenspektroskopische Untersuchungen an Divinylcyclobutanen (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 994-1003 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Photoelectron Spectroscopic Investigations on DivinylcyclobutanesThe He(I) photoelectron (PE) spectra of cis/trans-1,3-divinylcyclobutane (1,2), cis/trans-1,2-divinylcyclobutanes (3,4), as well as the alkyl-substituted 1,2-divinylcyclobutanes 5-7 have been recorded. The interpretation is based on semiempirical calculations (MINDO/3, MNDO) and calculations using a ZDO-model. In case of 1-4 we determined the conformation of lowest energy by optimization of all geometrical parameters. The orbital energies calculated for this conformation agree very well with the measured vertical ionization potentials.
    Notes: Die He(I)-Photoelektronen (PE)-Spektren von cis/trans-1,3-Divinylcyclobutan (1,2), cis/trans-1,2-Divinylcyclobutan (3,4) sowie der alkylsubstituierten 1,2-Divinylcyclobutane 5-7 werden mit Hilfe semiempirischer Rechnungen (MINDO/3, MNDO) und eines ZDO-Modells interpretiert. Bei 1-4 wurde durch Geometrieoptimierung die anti-bisektierte Konformation in jedem Falle als die mit niedrigster Energie bestimmt. Die Orbitalenergien, die für diese Konformation berechnet werden, ergeben eine gute Übereinstimmung mit den gemessenen vertikalen Ionisationspotentialen.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19811140318
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