Anionic Graft Copolymers. III. Hydrogenation of Polydienes Grafted with Vinylaromatics

A new method is described to prepare graft copolymers of polystyrene and polyvinylcyclohexane on polyethylene and poly (ethylene, butene-1). Hydrogenation of the butadiene moieties of graft copolymers of polystyrene on poly-1, 4-butadiene and high vinyl polybutadiene forms graft copolymers of polystyrene on polyethylene and on poly (ethylene, butene-1). Graft copolymers of polyvinylcyclohexane on polyethylene and on poly (ethylene, butene-1) are prepared by completely hydrogenating graft copolymers of polystyrene on poly-1, 4-butadiene and on high vinyl polybutadiene. The physical properties of these polymer systems depend on composition and graft level, resulting in either tough polymers or elastomers.     

Concerning the Thermal Diastereomerization of the Green Fluorescent Protein Chromophore

Summary. Two model compounds for the green fluorescent protein chromophore were prepared. One of them incorporates the natural 4-hydroxybenzylidene group of the natural tyrosin derived chromophore, the other one bears a methyl group instead of the hydroxy group. Whereas the photochemically prepared (E)-diastereomer of the first compound very effectively reverted thermally (room temperature) to the thermodynamically stable (Z)-diastereomer, the (E)-diastereomer of the second derivative proved to be stable even at elevated temperatures for more than a day. This finding can be rationalized by constructing the appropriate resonance structures showing that only in the first case an effective delocalization enables partial single bond character of the benzylidene double bond. From the standpoint of chemical etiology, only Nature’s choice of the tyrosin derived chromophore of the green fluorescent protein provides an efficient radiationless thermal relaxation channel for the unwanted photo-diastereomerization product formed after excitation besides the dominating fluorescence channel of its chromophore.     

Stable Electroenzymatic Processes by Catalyst Separation

Division of labour : The rapid enzyme inactivation in the electroenzymatic synthesis of chiral alcohols has been the main obstacle for synthetic applications during the last two decades. The reasons for this inactivation have now been elucidated. The development of a water‐soluble polymeric mediator and the spatial separation of enzyme and mediator led to the first stable process and significantly improved catalyst utilisations (see picture).

     

Reconstitution of apomyoglobin with bile pigments

Summary Apomyoglobin was reconstituted with bile pigments of the verdinoid, 2,3-dihydroverdinoid, pterobilinoid, and violinoid type. Absorption and circular dichroism data as well as formation constants of the complexes were measured. From these results it was concluded that chromophore binding and induced chirality of these pigments are mainly governed by a lipophilic region opposite to the propionic side chain(s) and the asymmetric position of the hydrogen bonding acceptors of the propionic acid side chain(s) at the entrance of the protein pocket.Dedicated to Prof. Dr. A. Eschenmoser on occasion of his 65th birthday     

Simultaneous determination of cocaine and its metabolites with caffeine in rat serum microsamples by high-performance liquid chromatography

A single, isocratic high-performance liquid chromatographic method is described for the determination of cocaine and three of its metabolites along with caffeine in serum microsamples (50 microliters). The small sample size permits the tracking of pharmacokinetic data over time in individual, small animals. The method also was used to demonstrate that cocaine, benzoylecgonine and norcocaine in rat serum samples were stable for at least a month without the presence of sodium fluoride.     

Synthesis and properties of an ω,ω′-appended eighteen carbon chains hypericin derivative

Summary An ,-appended eighteen carbon chains hypercin derivative (2) was synthesized starting from emodin. The overall yield of the seven step synthesis was 12%. The¹H and¹³C NMR, absorption, and emission spectroscopic properties were measured;2 can be dissolved even in apolar solvents and polyethylene.

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Synthese und Eigenschaften eines mit C₁₈-Ketten ,-substituierten Hypericinderivats

Zusammenfassung Ein in den Positionen , mit zwei C₁₈-Ketten substituiertes Derivat des Hypericins (2) wurde ausgehend von Emodin synthetisiert. Die Gesamtausbeute der siebenstufigen Synthese betrug 12%. Die¹H- und¹³C-NMR, absorptions- und emissionsspektroskopischen Eigenschaften wurden gemessen;2 kann sogar in apolaren Lösungsmitteln und Polyethylen gelöst werden.

     

Chemistry of polyfunctional molecules-123. Reactions of BiBr3, SbI3 and AsI3 with LiN(PPh2)2; X-ray structure of a cyclophosphazene salt containing arsenic(I)

BiBr₃ or SbI₃ react at 20°C with LiN(PPh₂)₂ (1) to give elementary Bi or Sb and the P---P coupled phosphazene ligand Ph₂P---N=PPh₂---PPh₂=N---PPh₂ (2). The reaction of AsI₃ with 1 at room temperature formed yellow needles of the eight-membered heterocycle (3), whereas AsI₃ interacted at 80°C with 1 in the molar ratio of 1:3 to give elementary arsenic and 2. Treatment of AsI₃ and 1 at 20°C in a 1:2 stoichiometry yielded the seven-membered, cyclic arsenium(I) salt

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I·4THF (5·4THF), which was characterized by elemental analysis, conductivity, mass, IR and NMR spectroscopy and single-crystal X-ray structural analysis.     

Structural aspects and electronic absorption of the hydroxyphenanthroperylene quinones fringelit D,hypericin, and stentorin

Summary PPP type semiempirical quantum chemical calculations of absorption spectra were performed for hypericin, fringelit D, stentorin, and their respective conformers, tautomers, and deprotonated species. The results agree with the experimental absorption spectra of hypericin, stentorin, and fringelit D, their deprotonated species, and the polarized absorption spectra of an ,-long chain appended hypericin derivative embedded in stretched polyethylene.

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Strukturelle Aspekte und elektronische Absorptionseigenschaften der Hydroxyphenanthroperylenchinone Fringelit D, Hypericin und Stentorin

Zusammenfassung Semiempirische quantenchemische Rechnungen (PPP-Typ) der Absorptions-spektren von Hypericin, Fringelit D, Stentorin und ihrer Konformeren, Tautomeren und deren Deprotonierungsprodukten wurden durchgeführt. Die Resultate stehen in Einklang mit den experimentellen Absorptionsspektren von Hypericin, Fringelit D, Stentorin, ihrer Deprotonierungsprodukte und dem polarisierten Absorptionsspektrum eines in gestrecktem Polyethylen eingebetteten ,-substituierten Hypericinderivates.

     

Fast Response Oxygen Micro-Optodes Based on Novel Soluble Ormosil Glasses

 A new type of phenyl substituted ormosils as a matrix for oxygen-sensitive micro-optodes is described. The new ormosils combine features of classical polymers such as solubility in organic solvents and those of sol–gel glasses such as mechanical stability and a porous structure. They make possible a simple and fast fabrication of microsensors with reproducible properties. The influence of the conditions during the polymerisation process (precursor composition and thermal treatment) on the sensing properties has been studied in detail. Oxygen-sensitive films with ruthenium(II)–tris-(4,7-diphenyl-1,10-phenanthroline) and platinum(II)–octaethylporphyrin as indicators were characterised with respect to their mechanical and photophysical properties. Photostability, oxygen sensitivity, response behaviour and signal intensities of the sensing films and the micro-optodes were examined. Micro-optodes based on the new sensing materials are fast responding, photostable and can be produced with a sufficient batch to batch reproducibility. Compared to previously described oxygen micro-optodes, where polystyrene was used as immobilisation matrix, the new sensors can be autoclaved and show favourable properties such as a faster response and a higher sensitivity. They possess many potential applications in medical and biological research. Received June 12, 1998. Revision December 10, 1998.