Showing papers by "University of Duisburg-Essen published in 1987"

Two homologous protein components of hepatic gap junctions

Abstract: Gap junctions consist of closely packed pairs of transmembrane channels, the connexons, through which materials of low relative molecular mass diffuse from the cell to neighbouring cells. In liver, connexons consist of six protein summits1,2 which, until now, were believed to be identical3. However, besides the major polypeptide of relative molecular mass (Mr) 28,000 (and see refs 4 and 6), a component of Mr 21,000 (21K) has been repeatedly observed3–5 in liver. The amino-terminal sequence (18 residues) of this less abundant protein shows that it is related to, but distinct from, the Mr 28K protein. Immuno-staining and immuno-precipitation show both proteins to be in the same gap junctional plaques. Thus, it seems that hepatic gap junction channels (and by extension possibly others) are composed of two (or more) homologous proteins.

Cluster Glass and Domain State Properties of KTaO3 Li

Abstract: The phase boundary between low-temperature dipole glass and ferroelectric states of K1-xLixTaO3 is proposed to lie within 0.016 40 K. The crossover concentration xc ~ 0.022 is extrapolated from the condition Tg(xc) = Tc(xc) ~ 41.5 K.

N-Substituierte 4,5-Diethyl-2,5-dihydro-2,2,3-trimethyl-1,2,5-azasilaborole-Herstellung und Charakterisierung

Abstract: Das aus Natrium-triethyl-1-propinylborat (A) und Chlortrimethylsilan zugangliche (Z)-3-(Diethylboryl)-2-(trimethylsilyl)-2-penten (B) reagiert mit Alkalimetallamiden MNH2 (MNa, K) unter Methan-Abspaltung zu Alkalimetall-4,5,5-triethyl-2,5-dihydro-2,2,3-trimethyl-1,2,5-azoniasilaboratolen C1 und C2, aus denen beim Erwarmen unter Freisetzen von Ethan 1-Alkalimetall-4,5-diethyl-2,5-dihydro-2,2,3-trimethyl-1,2,5-azasilaborole [AlkalimetallNa (1a), K (1b)] gewonnen werden. Aus 1a werden mit HCI/Ether die NH-Verbindung 2a und mit CH3I die N-Methyl-Verbindung 2b hergestellt. Mit den Chloriden (CH3)3SiCl, (CH3)2SiCl2, CH3SiCl3, SiCl4, (CH3)3GeCl, (C6H5)3GeCl, (CH3)3SnCl, (C6H5)2PCI, (C6H5)2AsCl, (C2H5)2BCl, C8H14BCI, AlCl3,(C2H5)2AlCl, FeCl2 oder CoCl2 erhalt man aus 1a die N-Heteroatom-substituierten Heterocyclen [4a: RSi(CH3)3; 5a: RGe(CH3)3, 5b: R=Ge-(C6H5)3; 6: R=Sn(CH3); 7a: R=NHCH3, 7b: R=NHC6H5; 8: R=P(C6H5)2; 9: R=As(C6H5)2; 10a: R=B(C2H5)2, 10b: R=BC8H14; 11a: R=AlCl2(11b)2: R=Al(C2H5)2], [4a-4a: R = Si(CH3)2; (12)2: R′ = Fe; (13)2: R′ = Co] und [4a-4a-4a: R = SiCH3, 4b−4b−4b: R′ = SiCl] 2b reagiert mit primaren aliphatischen oder aromatischen Aminen H2NR [RC8H17, CH2C6H5, C6H5] und Diaminen H2N-R′-NH2 (R′=-[CH2]2, -[CH2]6-, -1,4-C6H4-, 2-H2NC6H4-) unter Transaminierung zu den N-substituierten Heterocyclen mit RC8H17 (2d), CH2C6H5 (2e), C6H5 (3a), 2-H2NC6H4 (3b) bzw. mit R′=-[CH2]2- (2a-2a), -[CH2]6- (2c-2c) und-1,4-C6H4 (3a-3a). Mit Monoorganohydrazinen H2N-NHR (RCH3, C6H5) bilden sich aus 2b unter Transaminierung Gemische von 7a bzw. b und den isomeren 5,6-Diethyl-1(2)-organo–1,2,3,6-tetrahydro-3,3,4-trimethyl-1,2,3,6-diazasilaborinen 14a, 14′a bzw. 14b. Die Struktur von 122 wird durch Rontgenstrahlbeugung ermittelt. (Z)-3-(Diethylboryl)-2-(trimethylsilyl)-2-pentene (B), obtainable from sodium triethyl-1-propynylborate (A) and chlorotrimethylsilane reacts with alkaline metal amides MNH2 (MNa, K) under elimination of methane to give the alkaline metal 4,5,5-triethyl-2,5-dihydro-2,2,3-trimethyl1,2,5-azoniasilaboratoles C1 and C2. On warming, C1 and C2 eliminate ethane to form 1-alkaline metal-4,5–diethyl-2,5-dihydro-2,2,3-trimethyl-1,2,5-azasilaboroles [alkaline metalNa (1a); K(1b)]. From 1a the NH compounds 2a are obtained with HCl/ether and the NCH3 compound 2b with CH3l. 1a reacts with the chlorides (CH3)3SiCl, (CH3)2SiCl2, CH3SiCl3, SiCl4, (CH3)3GeCl, (C6H5)3GeCl, (CH3)3SnCl, (C6H5)2PCI, (C6H5)2AsCl, (C2H5)2BCl, C8H14BCI, AlCl3,(C2H5)2AlCl, FeCl2 oder CoCl2 to give the N-heteroatomsubstituted heterocycles [4a: RSi(CH3)3; 5a: RGe(CH3)3, 5b: R=Ge-(C6H5)3; 6: R=Sn(CH3); 7a: R=NHCH3, 7b: R=NHC6H5; 8: R=P(C6H5)2; 9: R=As(C6H5)2; 10a: R=B(C2H5)2, 10b: R=BC8H14; 11a: R=AlCl2 (11b)2: R=Al(C2H5)2], R′[NSi(CH3)2C(CH3)=C(C2H5)2[4a-4a: und R″[NSi(CH3)2C(CH3)=C(C2H5)B(C2H5)B(C2H5)]3 [4a-4a-4a: R = Si(CH3)2; (12)2: R′ = Fe; (13)2: R′ = Co], and [4a-4a-4a: R = SiCH3, 4b−4b−4b: R′ = SiCl]. From 2b and primary aliphatic or aromatic amines H2NR [RC8H17, CH2C6H5, C6H5] und Diaminen H2N-R′-NH2 (R′=-[CH2]2, -[CH2]6-, -1,4-C6H4-, 2-H2NC6H4-) are obtained the corresponding N-substituted heterocycles with RC8H17 (2d), CH2C6H5 (2e), C6H5 (3a), 2-H2NC6H4 (3b) bzw. mit R′=-[CH2]2- (2a-2a), -[CH2]6- (2c-2c) und-1,4-C6H4 (3a-3a) under transamination. 2b and monoorganohydrazines H2N-NHR (RCH3, C6H5) react under transamination to give mixtures of 7a or b together with the isomeric 5,6-diethyl-1(2)-organo-1,2,3,6-tetrahydro-3,3,4-trimethyl-1,2,3,6-diazasilaborines 14a, 14′a and 14b. The structure of (122 is determined by an X-ray analysis.

Übergangsmetall-substituierte Diphosphene, IV .Cyclotriphosphane und Cyclotetraphosphane mit Eisen- und Rutheniumkomplexsubstituenten

Abstract: Die Ubergangsmetall-substituierten Cyclotriphosphane (η5-C5Me5)(CO)2M–P(PR)2 (M = Fe, Ru; R = Mesityl) (3a, b) sind durch Reaktion von (η5-C5Me5)(CO)2M–P(SiMe3)2 (1a, b) mit RPCl2 zuganglich. Daneben entstehen die isomeren Ubergangs-metall-substituierten Cyclotetraphosphane [(η5-C5Me5)(CO)2-M]2R2P4 (4, 5a, b). Von dem Isomeren 4b wurde eine Rontgenstrukturanalyse durchgefuhrt; Strukturaufklarung von 3–5 in Losung erfolgte mittels 31P-NMR-Spektroskopie. Transition Metal-substituted Diphosphenes, IV. -Cyclotriphosphanes and Cyclotetraphosphanes with Iron and Ruthenium complex-Substituents. The transition metal-substituted cyclotriphosphanes (η5-C5Me5)-(CO)2M–P(PR)2 (M = Fe, Ru; R = mesitylene) (3a, b) are obtained from the reaction of (η5-C5Me5)(CO)2M–P(SiMe3)2 (1a, b) with dichloromesitylphosphane. As by-products the transition metal-substituted cyclotetraphosphanes [(η5-C5Me5)(CO)2M]2-R2P2-R2P4 (4, 5a, b) are generated. The molecular structure of the isomer 4b is elucidated by X-ray analysis. Structure elucidation of 3–5 in solution is based on 31P-NMR spectroscopy.

Übergangsmetall-substituierte Diphosphene, IX1) Synthese und Struktur von metallierten 1,3-Diphospha-2-propanonen. – Carbonylierung von Diphosphenyl-Komplexen

Abstract: Die Diphosphenyl-Komplexe (η5-C5Me5)(CO)2M–PP–Ar (3) (MFe, Ru, Os; Ar=2,4,6-t-Bu3C6H2) reagieren mit Fe2(CO)9 zu Addukten des Typs (η5-C5Me5)(CO)2M[Fe(CO)4]PP–Ar(4) und den 1,3-Diphospha-2-propanon-Komplexen [(η5-C5Me5)-(CO)2M–P(CO)PAr]Fe2(CO)6 (5). Offensichtlich entsteht 5 aus 3 durch katalytische Carbonylierung der aktivierten PP-Funktion. Von 4a und 5a wurden Rontgenstrukturanalysen durchgefuhrt. Transition Metal-Substituted Diphosphenes, IX1). – Synthesis and Structure of Metalated 1,3-Diphospha-2-propanones. – Carbonylation of Diphosphenyl Complexes The diphosphenyl complexes (η5-C5Me5)(CO)2M–PP–Ar (3) (MFe, Ru, Os; Ar=2,4,6-t-Bu3C6H2) react with Fe2(CO)9 to yield adducts such as (η5-C5Me5)(CO)2M[Fe(CO)4]PP–Ar(4) as well as the 1,3-diphospha-2-propanone complexes [(η5-C5Me5)-(CO)2M–P(CO)PAr]Fe2(CO)6 (5) by catalytic carbonylation of the activated PP double bond. The structures of 4a and 5a are established by X-ray diffraction studies.

Isomeric Borabicyclo[4.3.0]nonanes from Bis(9‐borabicyclo[3.3.1]nonane) by Gas‐Phase Pyrolysis

Abstract: The gas-phase pyrolysis of bis(9-borabicyclo[3.3.1]nonane) (1)2 has been studied in the range of 400 −620°C. At 490°C approximately equal amounts of 1-borabicyclo[4.3.0]nonane (2) and 8-borabicyclo[4.3.0]nonane (3) are formed (yield > 95%). Heating of 3 which persumably exists as the oligomer with mixed 1,1:2,2- and 1,2:1,2-diborane(6) structure 4, in the condensed phase to above 100°C results in the formation of the air and hydrolysis stable 5 with a 1,2:1,2-diborane(6) structure. The structure of 5 has been determined by X-ray analysis. The pyrolysis of 9-alkyl-9-borabicyclo[3.3.1]nonanes 6 [alkylethyl (6a), 1,2-dimethylpropyl (6b), and isopinocampheyl (6c) gives 2 and small amounts of (1)2. The formation of 2 (1)2 as well as 2 and (1)2 from 6 indicate that monomeric 9-borabicyclo[3.3.1]nonane 1 is an intermediate. Die zwischen 400 und 620°C untersuchte Pyrolyse des gasformigen Bis(9-borabicyclo[3.3.1]nonans) (1)2 liefer bei ca. 490°C in hohen Ausbeuten ( > 95%) 1-Borabicyclo[4.3.0]nonan (2) und 8-Borabicyclo[4.3.0]nonan (3), das vermutlich als Dimer (3)2 mit 1,1 2,2-Diboran(6)-Struktur bzw. als Oligomer 4 mit 1,1:2,2- sowie 1,2:1,2-Diboran-Struktur anfallt. (3)2 und 4 isomerisieren in kondensiertem Zustand oberhalb ca. 100°C zu den Luft- und Hydrolyse-resistenten Verbindungen 5 mit ausschlieslich 1,2:1,2-Diboran(6)-Struktur. Von 5 liegt eine Rontgenstrukturanalyse vor. Die Pyrolyse der 9-Alkyl-9-borabicyclo[3.3.1]nonane 6 [AlkylEthyl (6a). 1,2-Dimethylpropyl (6b) und Isopinocampheyl (6c)] liefert 2 sowie kleinere Anteile an (1)2. Sowohl die Bildung von 2 aus (1)2 als auch von 2 und (1)2 aus 6 weisen auf das Auftreten des monomeren 9-Borabicyclo[3.3.1]nonans 1 wahrend der Pyrolyse hin.

Dihydroazaborolyl-Komplexe, XXII Zur Chemie des (Dihydroazaborolyl)eisen-Kations

Abstract: Der p-Xylol-Ligand in (1-tert-Butyldihydro-2-methyl-η5-1H-1,2-azaborolyl)(p-xylol)eisen-hexafluorophosphat, [AbFe(p-xylol)]-PF6 (1), last sich durch verschiedene Substituenten verdrangen: [AbFe[P(OMe)3]3]PF6 (2), [AbFe(PMe3)3]PF6 (3) und [AbFe(CH3CN)(PMe3)2]PF6 (4) bilden sich leicht unter Photolysebedingungen. In 4 kann CH3CN durch CO verdrangt werden zu [AbFe(CO)(PMe3)2]PF6 (7). Der Tricarbonylkomplex [AbFe(CO)3]-BF4 (8) ist nur aus AbFe(CO)2I, CO und AgBF4 zuganglich. 1 addiert H− und D− an den p-Xylol-Ring in exo-Stellung, wobei sich die Cylcohexadienylkomplexe AbFe(1,4-dimethylcyclohexadienyl) (5) und AbFe(exo-6-deuterio-1,4-dimethylcyclohexadienyl) (6) bilden, die als Diastereomerengemische anfallen. Auch der entsprechende Mesitylenkomplex reagiert in analoger Weise und fuhrt mit H− zu AbFe(1,3,5-trimethylcyclohexadienyl), mit D− zu AbFe(exo-6-deuterio-1,3,5-trimethylcyclohexadienyl), 1H-, 11B, 13C-, 31P-, IR- und Massenspektren charakterisieren Struktur- und Bindungsverhaltnisse. The p-xylene ligand in (1-tert-butyldihydro-2-methyl-η5-1H-1,2-azaborolyl)(p-xylene)iron hexafluorophosphate, [AbFe(p-xylene)]PF6 (1) can be substituted by different substituents: [AbFe[P(OMe)3]3PF6 (2), [AbFe(PMe3)3]PF6 (3), and [AbFe(CH3CN)-(PMe3)2]PF6 (4) are easily formed under photolysis conditions. In 4 CH3CN can be substituted by CO to give [AbFe(CO)(PMe3)2]-PF6 (7). The tricarbonyl complex [AbFe(CO)3]BF4 (8) is only available from AbFe(CO)2I, CO, and AgBF4. 1 adds H− and D− to the p-xylene ring in exo position to form the cyclohexadienyl complexes AbFe(1,4-dimethylcyclohexadienyl) (5), and AbFe(exo-6-deuterio-1,4-dimethylcyclohexadienyl) (6) which are obtained as mixtures of diastereomers. Also the corresponding mesitylene complex reacts in an analogous manner and leads to AbFe(1,3,5-trimethylcyclohexadienyl) with H− and to AbFe(exo-6-deuterio-1,3,5-trimethylcyclohexadienyl) with D−. 1H, 11B, 13C, 31P, IR, and mass spectra characterize the structure and bonding relationships.

Structure–reactivity correlation of photochemical reactions in organic crystals: intramolecular hydrogen abstraction in an aromatic nitro compound

Abstract: The molecular structure of 1,4-bis-(2-chloro-1,1-dimethylethyl)-2-nitrobenzene has been determined by X-ray crystallography. The single-crystal X-ray investigation, R= 0.067, showed the compound to be monoclinic, space group P21, a= 6.388(2), b= 13.848(4), c= 8.578(3)A, β= 94.05(3)°. Structural analysis of 2-nitro-t-butylbenzenes which undergo intramolecular hydrogen abstraction in the solid state upon irradiation by u.v. light was carried out in connection with structure–reactivity correlation studies and X-ray crystallographic investigations. On the basis of intramolecular geometry and molecular packing considerations, it has been possible to identify the hydrogen atom abstracted preferentially in crystals of this compound. The benzene ring is found to exist in the boat conformation.

[1+4]‐Cycloaddition eines Diphosphens an Acrolein; Synthese und Struktur eines Dihydro‐1,2λ5‐oxaphosphols mit exocyclischer PP‐Bindung

Abstract: Reaction of diphospheneiron, Cp(CO)2FeP:PR [Cp = pentamethylcyclopentadienyl, R = 2,4,6-(Me3C)3C6H2] with acrolein gave oxaphosphole iron carbonyl complex I, contg. an exocyclic P:P double bond. Crystal structure of I was detd.

Comparison principles for strongly coupled reaction-diffusion equations

Abstract: On considere les principes de comparaison pour les systemes de reaction-diffusion couples par les termes de reaction et de diffusion. On donne des applications aux equations de Fitz Hugh-Nagumo et aux modeles de fibres nerveuses couplees

The Microstrip Step Discontinuity: A Revised Description (Correction)

Abstract: In the above paper, three additional references were included during the revision procedure. However, the changes were not reflected in the numbers of the references given in the figures. In Figs. 3-8, reference numbers [34] and/or [35] should have been, respectively, [37] and/or [38]. In addition, the date of receipt of the manuscript should have been November 28, 1984.