Light Emission Resulting from Hydroxylamine-Induced Singlet Oxygen Formation of Oxidizing LDL Particles

Abstract— Oxidation of low-density lipoprotein (LDL) by low amounts of cupric ions resulted in the formation of singlet oxygen (₁O₂, ₁DL_g) when hydroxylamine (NH2OH) was added. Direct evidence on this excited species came from partial spectral resolution of the emitted light in the red spectral region (634 nm and 703 nm), which can be attributed to the dimol decay of singlet oxygen. Additional evidence for the existence of singlet oxygen came from the enhancing effect of deuterium oxide buffer (D20) on chemiluminescence intensity and the quenching effect of sodium azide. A linear correlation between NH2OH-de-pendent chemiluminescence intensity and the amount of diene conjugates (DC) formed in this reaction was observed. Removal of adventitious transition metals by adequate chelators prevented chemiluminescence in this system; NH2OH was also found to efficiently decrease metabolites of lipid peroxidation (LPO). Our findings are consistent with a sequence of reactions in which NH2OH first converts transition metals to their reduced state, thereby stimulating the formation of alkoxy- and peroxy-radicals. Peroxyradicals decompose in a bimolecular Russel reaction to hydroxyl compounds and singlet oxygen while the majority of alkoxy radicals are eliminated by a secondary reaction with NH2OH. Identical effects were observed when reducing antioxidants such as ascorbic acid or trolox C were used instead of hydroxylamine.     

INVESTIGATIONS ON THE LIGHT-EMITTING SPECIES IN THE REACTION OF METMYOGLOBIN AND METHEMOGLOBIN WITH HYDROGEN PEROXIDE

Abstract The formation of a compound I type ferryl complex in the reaction of methemoglobin (MetHb) and metmyoglobin (MetMyo) with hydrogen peroxide is accompanied by strong chemiluminescence. An approach to identify the nature of the light-emitting species was made by the use of quenchers and sensitizers reacting with singlet oxygen and compounds interfering in the formation and reactivity of other reactive oxygen species. Singlet oxygen is not the source of light emission. This could be concluded from the results obtained using the specific singlet oxygen trap 9,10-anthracenedipropionic acid (ADPA) in combination with high-performance liquid chromatography (HPLC) analysis. The singlet oxygen adduct of ADPA was not formed in the incubation systems (MetHb or MetMyo/H₂O₂). Instead, ADPA was oxidized by the ferryl ion to a different oxidation product, which was characterized by HPLC and IR spectroscopy. In the case of MetHb-related chemiluminescence, light emission does not result from a single source. Both, SH-groups and O₂^.¯ radicals are involved because blocking of thiol-groups with N-ethylmaleimide (NEM) and scavenging of O₂^.¯(by superoxide dismutase) suppressed chemiluminescence by 50% and 30%, respectively. Development of MetMyo-related chemiluminescence is not dependent on thiol groups (which are not present in the globin moiety) and also 0₂^.¯is not involved. Although generation of chemiluminescence in MetHb and MetMyo seems to follow different mechanisms, both types of light-emitting species are sensitive to antioxidants, such as uric acid and ascorbate. The detection of the respective free radicals by means of ESR demonstrates that both MetHb- and MetMyo-mediated chemiluminescence is associated with a strong one-electron oxidizing species, which seems to be identical with the light-emitting source itself. Also desferal, which was originally used to exclude the involvement of a Fenton-type reaction, was readily oxidized to the nitroxide free radical associated with a strong decrease of chemiluminescence. This quenching effect was not dependent on iron complexation because the addition of iron was ineffective. In summary, chemiluminescence is not restricted to a single chemical process but is related to different one-electron transfer reactions from globin residues to the oxo-heme center.     

On the properties of 2HNbSe2

The dHvA-effect for 2HNbSe₂ is calculated for different directions of the external field. We also calculate the coexistence region of superconductivity and magnetic ordering using a two-band model.     

CHEMILUMINESCENCE and EPR STUDIES ON THE EXCITATION SITE OF FERRIC-HEME-OXO COMPLEXES OF NATURAL and MODEL HEME SYSTEMS

Chemiluminescence was detected both in the reaction system of H₂O₂ plus heme proteins such as methemo- and metmyoglobin and ferric-protoheme complexes used as a model system. The intensity of chemiluminescence was found to be mediated by ligand binding to the sixth coordination site of the ferric-protoheme compounds, e.g. chemiluminescence was not observed with the bisimidazole ferric-protoheme complex. On the other hand the pentacoordinated histidine ferric-protoheme complex exhibited strong light emission. Comparative studies with various ligand-heme compounds elucidated that light emission was inversely correlated with the binding strength of the respective ligand at the sixth coordination site. The basic reaction mechanism causing the establishment of an excited state was studied by monitoring chemiluminescence and EPR signal formation of ligand-modified heme proteins in the presence of different electron donors. External electron donors such as Trolox C, TMPD and ascorbic acid affected a strong reduction in the development of chemiluminescence suggesting the essential involvement of an inner-molecular electron transfer process. Our results allow the conclusion that chemiluminescence is generated from the decay of an excited state of oxo-heme compounds established as a result of a one electron transfer step from a ligand group to heme iron.     

Semiclassical quantization of the nonlinear Schrödinger equation

Using the functional integral technique of Dashen, Hasslacher, and Neveu, we perform a semiclassical quantization of the nonlinear Schrödinger equation, which reproduces McGuire's exact result for the energy levels of the theory's bound states. We show that the stability angle formalism leads to the one-loop normal ordering and self-energy renormalization expected from perturbation theory and demonstrate that taking into account center-of-mass motion gives the correct nonrelativistic energymomentum relation. We interpret the classical solution in the context of the quantum theory, relating it to the matrix element of the field operator between adjacent bound states in the limit of large quantum numbers. Finally, we quantize the NLSE as a theory of N component fermion fields and show that the semiclassical method yields the exact energy levels and correct degeneracies.     

Kosmologische Lösungen eines homogenen Wirkungsprinzips

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