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Biomedical subjects

E Lengfelder

Publications and source records attributed to E Lengfelder.

81 records · Page 5Linked to original sources
PubMed1975

Pulse-radiolytic investigations of catechols and catecholamines. I. Adrenaline and adrenochrome.

Adrenaline (epinephrine), adrenochrome and C4-substituted catechol model compounds were pulse-irradiated in aqueous neutral and alkaline solutions. Transient spectra are reported after oxidizing adrenaline and reducing adrenochrome. All species appearing during 20 msec interval after the pulse have been identified: the OH adduct with an absorption maximum at 300-310 nm, the semiquinone (at 245 nm), and adrenaline quinone (at 340 nm). The reaction of superoxide anions (O2-) with adrenaline was less efficient, compared with OH radicals. A novel oxidation product, derived from the semiquinone and O2-, has been identified as the 4-hydroxy-3,6-dioxo derivate. The pulse-radiolytic reduction of adrenochrome by hydrated electrons (eaq-) yielded the semiquinone of adrenochrome (absorbing at 470 nm), which subsequently decays by a second-order process. The dismutation products leuco-adrenochrome (absorbing at 300 nm, pH 9-8) and the adrenochrome tautomer (absorbing at 375 nm) are unstable, forming 5,6-dihydro-N-methyl indole and regenerating adrenochrome.

Adrenochrome↗
PubMed1975

Superoxide dismutase activity of Cu(Tyr)2 and Cu, Co-erythrocuprein.

Crystalline Cu(Tyr)2 and homogeneous Cu2Co2-erythrocuprein were prepared. The reactivity of each chelated Cu2 compound with superoxide was studied by pulse radiolysis at pH 7.6 +/- 0.1 and compared with the reactivity of native erythrocuprein (superoxide dismutase). Superoxide anions were generated by a 40-ns pulse of 1.81-MeV electrons. The yield of O2 ranged between 6 - 60 muM. The kinetics of the spontaneous O2 decay were second order; in the presence of Cu2 complexes the reaction was first order with respect to O2. Taking into account the effect of the different Cu2 concentrations on the O2 decay, second-order rate constants for the reaction of chelated Cu2 with O2 were obtained. For an equivalent of Cu2 in either erythrocuprein or Cu, Co-erythrocuprein, a numerical value of 1.3 +/- 0.1 x 10(9) M-1S-1 was calculated. Surprisingly, the same value was obtained employing Cu(Tyr)2. The highest rate constant was measured for the hydrated Cu2 (2.7 x 10(9) M-1S-1). In the presence of a biologically significant chelating agent such as serum albumin, a marked decrease in the Cu2aq-induced superoxide dismutation was observed. This was not the case when the dismutation in the presence of either the Cu2 of native erythrocuprein or Cu, Co-erythrocuprein, or those Cu2 ions chelated with tyrosine or certain di- and tripeptides was measured.

Animals↗
PubMedDate not supplied

Kinetic investigations of the autoxidation of adrenalin.

Generation rates of superoxide anions (O2-) by autoxidizing adrenalin at pH 9.5 were determined in solutions containing either superoxide dismutase (0.85 M-1 S-1) or hydroxylamine (0.0185 M-1 S-1) as competitive scavengers. The rate constants of O2- with adrenalin and hydroxylamine were calculated for neutral and alkaline solutions. The respective values were for adrenalin: 5.6 X 10(4) M-1 S-1, pH 7.8; 7.0 X 10(3) M-1 S-1, pH 9.5--and for hydroxylamine 5.9 X 10(4) M-1 S-1, pH 7.8; 3.4 X 10(4) M-1 S-1, pH 9.5. The effects of various competitors and O2- sources on the rate constants were compared.

Epinephrine↗
PubMedDate not supplied

Cyanide insensitive iron superoxide dismutase in Euglena gracilis. Comparison of the reliabilities of different test systems for superoxide dismutases.

Two proteins (P1 and P2, with weights of 57,500 and 27,500 respectively) were isolated from Euglena gracilis. Both proteins show cyanide-insensitive superoxide dismutase activity in the "classical" superoxide dismutase assay, using xanthine-xanthine oxidase as O2.- generator. If O2.- is generated chemically (autoxidation of reduced anthraquinone), photochemically (illuminated riboflavine) or pulse radiolytically, only protein P1 but not P2 shows SOD activity. Protein P1 contains 1 g atom (determined: 0.82) iron (no Mn or Cu) per mole protein and may thus be defined as iron-superoxide dismutase. Protein P2, showing the spectral properties of a flavoprotein, exhibits the activities of ferredoxin-NADP-oxidoreductase and "diaphorase". The cyanide-insensitive SOD-activity of this Diaphorase" in the xanthine oxidase-assay for superoxide dismutase makes this classical and commonly used test unreliable for assay cyanide insensitive SOD activities. The existence of the "prokaryote-type" of superoxide dismutase (Fe-SOD) in Euglena gracilis is exceptional for an eukaryotic, autotrophically grown organisms.

2,6-Dichloroindophenol↗