Georg Tomaschewski

Immobilization of enzymes in photochemically cross-linked polyvinyl alcohol.

Invertase and amyloglucosidase were entrapped in polyvinyl alc. membranes through UV irradn. of pendent styrylpyridinium groups. The influence of crosslinking on immobilization efficiency was studied using prepolymers with varied cross-linker d., the above mentioned enzymes of different mol. wt., and various substrates. It was found that the larger enzyme invertase is effectively immobilized even in polymers with very low contents of the crosslinking component. In contrast for an effective immobilization of amyloglucosidase, a higher degree of crosslinking is necessary. Although there is only a slight loss in amyloglucosidase activity, the apparent activity, esp. for the macromol. substrate starch, is low. This is contributed to a hindered diffusion of the substrates in the swollen hydrogel matrix. The influence of the diffusion is also reflected in the kinetic parameters Km and Vmax. The pH and temp. optima of entrapped amyloglucosidase are similar to those of the native enzyme in soln.

Synthesis, photomodification and characterization of homo- and copolymers with 2,5-bisaryltetrazolyl pendant groups

Abstract The homopolymer of 2-(4-ethenyl)phenyl-5-phenyl-2 H -tetrazole and its copolymers with styrene and acgylonitrile were prepared and characterized by thermoanalytic and spectroscopic methods. Photochemically induced crosslitking and modification of these polymers with vinylic agents such as acrylic acid, methacrylic acid and its derivatives through 1,3-dipolar cycloaddition was investigated in solution and thin solid films. It was proved by UV- and ATR/FfIR-spectroscopy that the reaction of the polymers with the modifiers leads to the formation of heterocyclic structures.

Photoinduzierte bildung von 8bH-3,4-dihydro-1-(4-methylphenyl)-diazirino[3,1-a]isochinolin

Abstract Photolysis of 3,4-Dihydro-isoquinolinium-2-(4-methylphenylimide) 2 gives under valence tautomerism the relevant aryl-substituted condensed diaziridin 3 . The process is thermally reversible.

Synthesis of a hydrophobised and photocrosslinkable prepolymer based on poly(vinyl alcohol)

Abstract The aim of the investigations was to synthesise photocrosslinkable hydrophobic prepolymers based on polyvinyl alcohol) for the use in enzyme entrapment. Therefore, the influence of the sequence of acetalisation of poly(vinyl alcohol) with a photocrosslinkable aldehyde 1-methyl-4-[2-(4-formylphenyl)-ethenyl]-pyridinium-methosulphate (SbQ-4) and propionaldehyde was examined to find out the reaction conditions yielding prepolymers with similar content of photocrosslinkable component but different amounts of propionaldehyde acetals. Data obtained from quantitative 13C-NMR spectroscopy and UV spectrophotometry proved that a stepwise acetalisation first with SbQ-4 leads to the desired prepolymers. In contrast, during simultaneous acetalisation competition of both aldehydes yields prepolymers with a content of photocrosslinkable group that depends on the degree of acetalisation with propionaldehyde.

Synthesis of a new photocrosslinkable prepolymer, based on poly(styrene-co-maleic anhydride)

Abstract Photocrosslinkable prepolymers were synthesized by using poly(styrene- co -maleic anhydride) as the polymeric backbone and 4-[2-(4-[aminomethyl]phenyl)ethenyl]pyridine as the crosslinking agent. The photochemical [2+2] cycloaddition of the ethylene double-bond is utilized as the crosslinking principle. Using prepolymers, substituted with more than 2 mol% crosslinker, UV irradiation yields insoluble networks. The network density can be easily adjusted by variation of the crosslinker content.

Photochemistry of arylsydnones part VI. Peculiarities of the photolysis of N-phenylsydnones☆

Abstract The photolysis of sydnones and glycines with appropriate 15 N and/or D labelling was investigated in situ using electron spin resonance (ESR) spectroscopy in fluid solution. In contrast with other sydnones, e . g . 3,4-diphenylsydnone, radical intermediates were observed and identified as PhNCHNO CHNPh. The proposed radical structure was confirmed by analysis of the spectral pattern of the isotopically labelled radicals produced by photolysis of the corresponding starting materials. Mechanistically these radicals are of importance in the photolysis of N -arylsydnones. This is supported by the fact that it has so far been impossible to detect nitrile imines, reflecting the peculiarities of the photolysis of N -arylsydnones. Bearing in mind the experimental conditions for the registration of the ESR spectra, it is not possible to give an exact number of radicals (PhNCHNO CH=NPh) generated in the photochemical process. Therefore we cannot rule out the formation of nitrile imine intermediates.

Pyrazolonderivate IX@@@Pyrazolone derivatives, IX. EPR-investigations of Cu(II)-complexes of 4-amino-methylene-Δ2-pyrazolinones-(5): EPR-Spektroskopische Untersuchungen an Kupfer(II)-Komplexen mit Liganden vom 4-Amino-methylen-Δ2-pyrazolinon-(5)-Typ

AbstractThe EPR spectra of Cu(II)-complexes of substituted 4-R-phenyl-aminomethylene-Δ2-pyrazolinones-(5) [R = N(CH3)2,p-OCH3, H,p-Cl,p-NO2] were obtained using polycrystalline samples and solutions. The spin-Hamiltonian parameters

EPR-Untersuchungen an Radikalen und Triplettzuständen von Fluorenderivaten

\tilde g, \tilde A, \tilde D