Electron transport and electrochemistry of mesomorphic fullerenes with long-range ordered lamellae

Fullerenes, C60, modified with long alkyl chains form long-range ordered lamellar mesophases permitting a high C60 content. The mesomorphic fullerenes feature reversible electrochemistry and a comparably high electron carrier mobility making them attractive components for fullerene-based soft materials.     

The dianion Claisen rearrangement of β-hydroxy esters

Claisen rearrangement of β-hydroxy allylic ester dianions provides stereocontrolled access to three contiguous chiral centers on an acyclic framework; an unambiguous method has been developed for assessing diastereoselectivity.     

Versatile "traceless" sulfone linker for SPOS: preparation of isoxazolinopyrrole 2-carboxylates

A five-step solid-phase synthesis of isoxazolinopyrrole-2-carboxylates (6) that employs a traceless sulfone linker strategy is reported. Resin-bound diene 4, obtained by acetylation and concomitant beta-elimination of acetate from resin-bound allylic alcohol 3, underwent regioselective 1,3-dipolar cycloadditons with nitrile oxides. Formation of the pyrrole products in a resin-releasing strategy was performed by pyrrole annulation with alkyl isocyanoacetates, which react with the vinyl sulfone moiety to generate the target isoxazolinopyrrole-2-carboxylates (6). Use of this chemistry afforded eight isoxazolinopyrrole-2-carboxylates in 6-24% overall yields from polystyrene/divinylbenzene sulfinate 1.     

The effect of transformation-defective avian oncornavirus mutants on tumor antigen expression.

The recent isolation of conditional (temperature sensitive) and nonconditional transformation-defective mutants of avian sarcoma virus strains has facilitated the investigation of the effect of virus transformation on the cell's phenotype, e.g., with respect to morphology, growth pattern, or cell surface antigenicity. Special emphasis was laid on elucidating the correlation between transformed phenotype and tumor antigen expression. All of the tested nontransforming deletion mutants and the majority of the temperature-sensitive mutants were unable to induce tumor antigens in phenotypically untransformed cells. However, 3 temperature-sensitive mutants were found which were able to support the expression of tumor specific surface antigens even at restrictive temperature, when cells otherwise exhibited a normal phenotype. The theoretical and practical implications of this association between normal phenotype and tumor antigen expression are discussed.     

Über Fermentmodelle der Atmungskette (1)

Zusammenfassung Von den mit Wirkungsgruppen aus der Hämin- und Chlorophyllreihe substituierten makromolekularen Verbindungen führt nur die Peptidkette als makromolekularer Träger zu einer Aktivierung der Wirkungsgruppe. Löslichkeit und Hydrophilie des Oxydase- bzw. des Cytochrom-Modelles, Bindungsart der prosthetischen Gruppe sowie das Verhalten des Substrates spielen eine Rolle, wie mit Hilfe von manometrischen Messungen, sowie durch Ermittlung der relativen Reaktionsgeschwindigkeitskonstanten (polarographisch) gezeigt wird. Zur Deutung werden Energiefortleitung durch die Peptidkette und Zwischenstoffwirkungen derselben diskutiert.Bei der photochemischen Spaltung der Kohlenoxydverbindungen der Mesohämin- bzw. der Cytohämin-Poly-(phenylalanin-glutaminsäure) wurde sowohl für die Einstrahlung in die Blaubande der Wirkungsgruppe wie auch in die Phenylalaninbande der Polypeptidkette eine Quantenausbeute von 1 gefunden. Dies beweist eine Beteiligung der Peptidkette am Energietransport zur Wirkungsgruppe.Es werden 3 Typen von makromolekularen Einschlußsystemen besprochen, es wird gezeigt (optisch, polarographisch, Verhalten im Zentrifugalfeld), daß kanzerogene Verbindungen Einschlußsysteme liefern.Schließlich wird über Teilsynthesen von Fermentmodellen berichtet, die nach dem Prinzip Polypeptidkette — Einschlußbereich — Wirkungsgruppe aufgebaut sind. Von den in Arbeit befindlichen Synthesen der 20-bis-29 gliedrigen cyclischen Disulfide wird die Synthese des L-Cysteinyl-tetraglycyl-L-cystein-disulfids besprochen, ferner die zur Verknüpfung mit dem Einschlußbereich erforderlichen Porphyrin- und Phorbin-(N)- und (C)-Aminosäurepeptide der Hämin- und Chlorophyll-a-Reihe mit optisch aktiven und inaktiven Wirkungsgruppen.     

Precise determination of the ground state hyperfine structure splitting of43Ca II

Within the framework of systematic hyperfine structure (hfs) investigation of titanium atom the hfs-splittings of 3d ³(² G)4s b ¹ G ₄ levels for two stable isotopes⁴⁷Ti and⁴⁹Ti have been studied. 5 hfs intervals for each isotope have been measured using ABMR-LIRF method (atomic beam magnetic resonance detected by laser induced resonance fluorescence) with an accuracy of about 300 Hz. TheJ-off-diagonal second order perturbation effects have been taken into account in the interpretation. Upper limit of the contributions from octupole and hexadecapole hyperfine structure interaction to hfs intervals of this level have been estimated to be about 400 Hz. However, for most of hfs intervals these contributions are almost within experimental error and in order to study such effects a more precise experimental method should be used.     

Solid-phase synthesis of an isoxazolinopyrrole library

A four-step solid-phase synthesis of isoxazolinopyrroles 8 that employs an acid-labile 2-(4-formyl-3-methoxyphenoxy)ethyl polystyrene HL resin 1 is reported. Resin-bound vinyl sulfone 5 is obtained by DIC coupling with acid 4, which was in turn synthesized in solution phase by a regioselective nitrile oxide 1,3-dipolar cycloaddition. The resin-bound pyrrole 7 was synthesized on solid phase by pyrrole annulation with various isocyano derivatives and potassium t-butoxide in which the sulfone alpha-anion generated by Michael addition gives the desired pyrrole through internal condensation followed by a sigmatropic [1,5]-hydrogen shift. The resulting isoxazolinopyrroles 8 were released from resin 7 by 10% TFA in moderate to excellent overall yields from 2-(4-formyl-3-methoxyphenoxy)ethyl polystyrene HL resin 1.     

Direct and Cytochrome c Mediated Electrochemistry of Bilirubin Oxidase on Gold

Direct electron transfer (DET) of bilirubin oxidase from Myrothecium verrucaria (BOD) was established on promoter‐modified gold electrodes. The electrochemical behavior of the enzyme in solution was studied by means of cyclic voltammetry evaluating the biocatalytic reduction of dioxygen. The reaction of BOD at Au electrodes was shown to be efficient only at low pH. In addition, a novel interaction between BOD and cytochrome c (cyt.c) was found. It was shown that BOD efficiently accepts cyt.c as an electron donor in both cases when cyt.c is in solution and electrostatically adsorbed. The results suggest that cyt.c can play the role of a mediator facilitating electron transfer in a pH range where no DET could be observed between the enzyme and the electrode. For the interaction between cyt.c and BOD in solution the reaction kinetics has been studied electrochemically and spectrophotometrically.     

Design and synthesis of propeller-shaped dispiroisoxazolinopiperidinochromanones

A library of novel, propeller-shaped dispirotriheterocyclic isoxazolinopiperidinochromanones is reported. Each rigid dispirotriheterocycle was prepared in five linear steps from commercially available tert-butyl 4-oxopiperidine-1-carboxylate and various derivatives of 1-(2-hydroxyphenyl)ethanone, benzaldehyde oxime, and carboxylic acids. Computational chemistry was employed to analyze the three-dimensional geometries of these dispirotriheterocycles, as well as to generate chemoinformatic bioavailability data. X-ray crystallographic structure determination verified the regioselectivity of the nitrile oxide 1,3-dipolar cycloaddition reaction. The resulting library of compounds has been added to the National Institutes of Health repository (approximately 10 mg of each with > or =90% purity) for pilot-scale biomedical studies with bioassay data available at the National Center for Biotechnology Information PubChem database.