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PubMed1998

Singlet molecular oxygen in photobiochemical systems: IR phosphorescence studies.

Singlet molecular oxygen (1O2) is one of the most active intermediates involved in photosensitized oxygenation reactions in chemical and biological systems. Deactivation of singlet oxygen is accompanied by infrared phosphorescence (1270 nm) which is widely employed for 1O2 detection and study. This review considers techniques for phosphorescence detection, phosphorescence spectra, quantum yields and kinetics under laser excitation, the radiative and real 1O2 lifetimes in organic solvents and water, 1O2 quenching by biomolecules, and estimation of singlet oxygen lifetimes, diffusion lengths and phosphorescence quantum yields in blood plasma, cell cytoplasm, erythrocyte ghosts, retinal rod outer segments and chloroplast thylakoids. The experiments devoted to 1O2 phosphorescence detection in photosensitizer-containing living cells are discussed in detail. Information reviewed is important for understanding the mechanisms of photodestruction in biological systems and various applied problems of photobiology and photomedicine.

Humans↗
PubMed2002

Biological significance of singlet oxygen.

The biological significance of singlet oxygen (1O2), an electronically excited species of oxygen, has been realized only in the last two decades. This was mainly due to the lack of proper methodology to generate this reactive oxygen species (ROS) in pure form and its reactions with biological molecules. Recent studies, using newly developed detection methods, show that 1O2 being generated in many biological systems, can significantly and quite often adversely alter several crucial biomolecules including DNA, proteins and lipids with undesirable consequences including cytotoxicity and/or disesase development. The reactions of 1O2 with the biological molecules are rather specific, as compared to other ROS. There are various compounds, mainly derived from natural sources that offer protection against damage induced by 1O2. Among the antioxidants carotenoids are the most effective singlet oxygen quenchers followed by tocopherols and others. The same reactive species if generated specifically in diseased states such as cancer can lead to the cure of the disease, and this principle is utilized in the newly developing modality of cancer treatment namely photodynamic therapy. Singlet oxygen, in low concentrations can also act as signaling molecule with several biological implications. This review clearly brings out the biological significance of 1O2.

Animals↗
PubMedDate not supplied

[Photodynamic activity and singlet oxygen].

The primary mechanisms for the photodynamic action of pigments and dyes, the principles of their division into mechanisms of type I and type II, and the role of these processes in biological systems are reviewed. Singlet oxygen is considered to be an indicator of the mechanisms of photodynamic reactions. The methods of its detection are described, which are based on the use of chemical traps, measurements of infrared phosphorescance at 1270 nm, and the registration singlet oxygen-sensitized delayed fluorescence caused by the summation of the energy of two singlet oxygen molecules by one dye molecule.

Animals↗
PubMed1984

Singlet oxygen production by chloroperoxidase-hydrogen peroxide-halide systems.

Singlet oxygen production in the chloroperoxidase-hydrogen peroxide-halide system was studied using 1268 nm chemiluminescence. With chloride or bromide ions, singlet oxygen is produced by the mechanism (formula; see text) (formula; see text) where X- is chloride or bromide ion. Under conditions where there is high enzyme activity and when Reaction B is fast relative to Reaction A, singlet oxygen is produced in near stoichiometric amounts. In contrast, when Reaction A is fast relative to Reaction B, oxidized halogen species (chlorine and hypochlorous acid for chloride ion; bromide, tribromide ion, and hypobromous acid for bromide ion) are the principle reaction products. With iodide ion, no 1268 nm chemiluminescence was detected. Past studies have shown that iodine and iodate ion are the major end products of this system.

Bromides↗
PubMed1995

Increase of singlet oxygen protection of erythrocytes by vitamin E, vitamin C, and beta carotene intakes.

Substantial evidence supports the theory that free radicals, especially oxygen radicals, are involved in the process of aging. The human organisms have two ways to fight them: an enzymatic way with enzymatic intervention like superoxide dismutase, catalase... and a chemical way with the intervention of scavengers such as vitamins, cysteine, methionine, gluthatione... The aim of this work was to determine that an intakes of vitamins association: vitamin E, vitamin C and beta carotene induce an increase of singlet oxygen protection of erythrocytes' subjects. The method was based on the haemolytic effect of singlet oxygen which is generated by irradiation of hematoporphyrine at 365 nm, in 22 p. cent suspension of erythrocytes' subjects. Results show that a supply of beta carotene (15 or 30 mg/day), vitamin E (15 mg/day) and vitamin C (30 mg/day) involves an increase of singlet oxygen protection of erythrocytes of subjects. This protection appears very quickly after 15 days of treatment.

Administration, Oral↗
PubMed1995

EPR studies on the kinetics of quenching singlet oxygen.

The specific reaction between singlet oxygen (1O2) and 2,2,6,6-tetra-methyl-piperidine (TEMP) was utilized to investigate the kinetics of singlet oxygen quenching. Rose bengal was used for the generation of singlet oxygen (1O2). The deuterium isotope effect (rho) was found to be 22.1. The rate constant (kT) of the reaction of TEMP with 1O2 in H2O, D2O and ethanol were found to be 9.0 x 10(5) M-1s-1, 1.5 x 10(6) M-1s-1 and 7.3 x 10(5) M-1s-1, respectively. The intercept of the plot of [TEMPO]-1 at different H2O/D2O ratios was found to be constant, indicating the lifetime of 3Sens is independent of solvent deuteration. The quenching of 1O2 by azide and the sensitizer itself were confirmed by the constant intercept on the kinetic plots. Thus, the quenching rate constants for azide anion in ethanol solution (96%) and for ground state rose bengal in 0.05 M phosphate buffer (pH 7.4), were found to be 8.36 x 10(8) M-1s-1 and 1.72 x 10(4) M-1s-1, respectively. These studies not only verify the specificity of the reaction between TEMP and 1O2 but also provide a sensitive and specific assay for 1O2.

Cyclic N-Oxides↗
PubMed1997

Toxic and signaling effects of photochemically or chemically generated singlet oxygen in biological systems.

Singlet oxygen, generated photochemically or chemically, has damaging effects on biomolecules and exerts genotoxic, virucidal and cytotoxic effects. This is of relevance for biological systems because singlet oxygen can be produced photochemically as a result of the irradiation of endogenous or exogenously applied photosensitizers with visible or ultraviolet light, or in dark reactions, e.g. by stimulated phagocytes during the so-called oxidative burst. In addition, there is increasing evidence that singlet oxygen has pronounced effects on cellular signaling events leading to the induced expression of a variety of proteins. A novel observation is the activation of transcription factor AP-2 and cellular signaling cascades comprising the activation of c-Jun-N-terminal kinases (JNK/SAPK) and the NF-kappaB system.

Antiviral Agents↗
PubMed2006

A computational study of the lowest singlet and triplet states of neutral and dianionic 1,2-substituted icosahedral and octahedral o-carboranes.

This work introduces a calibrated B3LYP/6-31G(d) study on the electronic structure of singlet and triplet neutral species of 1,2-substituted icosahedral 1,2-R(2)-1,2-C(2)B(10)H(10) and octahedral 1,2-R(2)-1,2-C(2)B(4)H(4) molecules with R = {H, OH, SH, NH(2), PH(2), CH(3), SiH(3)} and their respective dianions formed by proton removal on each R group. A variety of small adiabatic singlet-triplet gaps DeltaE(ST) are obtained from these systems ranging from 2.93 eV (R = NH(2)) <or= DeltaE(ST) <or= 3.98 eV (R = SiH(3)) for the icosahedral neutrals and 1.56 eV (R = NH(2)) <or= DeltaE(ST) <or= 4.13 eV (R = SiH(3)) for the octahedral neutrals, these gaps being globally smaller for the dianionic systems, ranging from 0.94 eV (R(-) = CH(2) (-)) <or= DeltaE(ST) <or= 2.01 (R(-) = e(-)) for the icosahedral dianions 1,2-(R(-))(2)-C(2)B(10)H(10) and 0.91 (R(-) = CH(2) (-)) <or= DeltaE(ST) <or= 2.41 (R = SiH(2) (-)) for the octahedral dianions 1,2-(R(-))(2)--C(2)B(4)H(4) (R(-) = e(-), O(-), S(-), NH(-), PH(-), CH(2) (-), PH(2) (-)). The different gaps lie within or in the neighborhood of the visible region of the electromagetic spectrum. The optimized geometries for the molecular cage remain similar in substituted icosahedral and octahedral singlet states, while a rich variety of different structures can be found for the optimized triplet states.

Algorithms↗
PubMed2000

Effects of singlet oxygen on the extracellular matrix protein collagen: oxidation of the collagen crosslink histidinohydroxylysinonorleucine and histidine.

The reaction of singlet oxygen, a putative agent of skin photodamage, with the dermal collagen crosslink histidinohydroxylysinonorleucine (HHL) and its precursor histidine is reported. Reaction studies were performed with both purified HHL and bovine dermal tissue. We demonstrate that singlet oxygen can selectively oxidize HHL and histidine amino acid residues in dermal tissue and that intermediate oxidation products of histidine lead to new crosslink products. A novel mechanism for crosslink formation was proposed to involve nucleophilic addition to a transient imidazolone intermediate formed from singlet oxygen oxidation of the histidine imidazole moiety. The implication for such adduct formation and histidine oxidation in collagen proteins is the expression of aberrant collagen crosslinks, perturbation of the dermal collagen function, and hence an altered dermal state.

Animals↗
PubMed2000

Peridinin as the major biological carotenoid quencher of singlet oxygen in marine algae Gonyaulax polyedra.

Carotenoids in light-harvesting proteins and reaction centers increase the overall efficiency of photosynthesis by transferring absorbed light energy to chlorophylls. Peridinin and beta-carotene were isolated from Gonyaulax polyedra in a one-step purification protocol using the preparative circular chromatography (Chromatotron), performed on silica gel under N(2) atmosphere and n-hexane/acetone 8:2 as mobile phase and characterized by extensive (1)H NMR, infrared, and electrospray ionization mass spectrometry analyses. The quenching of singlet molecular oxygen [O(2) ((1)Delta(g))] was evaluated by NIR-emission assays using singlet oxygen generated by sensitization of either perinaphthenone or methylene blue. The NIR-emission assay showed that peridinin quench as singlet oxygen (k(q) = 9.5 x 10(8) M(-1) s(-1)) 5-fold less efficiently than beta-carotene (52 x 10(8) M(-1) s(-1)). A method, based on the use of high-performance liquid chromatography with UV-VIS detection, was then developed for the sensitive quantification of peridinin (55% of total carotenoids) and beta-carotene (4.1% of total carotenoids). Thus, since peridinin is 10-fold more abundant than beta-carotene, it is expected to be the major protector against the deleterious effects of O(2) ((1)Delta(g)) in Gonyaulax polyedra.

Animals↗
PubMed1989

Lycopene as the most efficient biological carotenoid singlet oxygen quencher.

Lycopene, a biologically occurring carotenoid, exhibits the highest physical quenching rate constant with singlet oxygen (kq = 31 X 10(9) M-1 s-1), and its plasma level is slightly higher than that of beta-carotene (kq = 14 X 10(9) M-1 s-1). This is of considerable general interest, since nutritional carotenoids, particularly beta-carotene, and other antioxidants such as alpha-tocopherol (kq = 0.3 X 10(9) M-1 s-1) have been implicated in the defense against prooxidant states; epidemiological evidence reveals that such compounds exert a protective action against certain types of cancer. Also, albumin-bound bilirubin is a known singlet oxygen quencher (kq = 3.2 X 10(9) M-1 s-1). Interestingly, those compounds with low kq values occur at higher plasma levels. When these differences are taken into account, the singlet oxygen quenching capacities of lycopene (0.7 microM in plasma), beta-carotene (0.5 microM in plasma), albumin-bound bilirubin (15 microM in plasma), and alpha-tocopherol (22 microM in plasma) are of comparable magnitude.

Bile Pigments↗
PubMed1975

Inactivation of biologically active DNA by gamma-ray-induced superoxide radicals and their dismutation products singlet molecular oxygen and hydrogen peroxide.

Since superoxide radicals are involved in many metabolically important as well as in some other, detrimental cellular processes, the reactivity of gamma-ray-induced superoxide radicals and its dismutation products singlet molecular oxygen and hydrogen peroxide with DNA have been studied. Superoxide dismutase which removes superoxide radicals and inhibits the formation of singlet oxygen in the solution protects the biologically active replicative form of DNA (from bacteriophage theta X174) against inactivation by ionizing radiation. Catalase which removes hydrogen peroxide also protects the DNA. Attempts with various chemical sources of singlet oxygen to determine whether this species inactivates DNA did not give an unequivocal answer. It is concluded from the presented experiments that a combination of the protonated form of the superoxide radical (HO-2) and H2O2 do inactivate DNA.

Binding Sites↗
PubMed1977

Formation of lipid peroxides in isolated rat liver microsomes by singlet molecular oxygen.

Rat liver microsomes were incubated in neutral aqueous solution of potassium peroxychromate, a system which generates singlet molecular oxygen. Such incubation resulted both in a rapid decline in NADPH-cytochrome c reductase activity, and in an increase in formation of lipid peroxides. These reactions were not inhibited by either superoxide dismutase (SOD) or mannitol, nor were they entirely duplicated by incubating microsomes with hydrogen peroxide. However, a high concentration of 1,4-diazabicyclo-[2,2,2]octane (DABCO), a known scavenger of singlet oxygen, prevented both decline in reductase activity and formation of lipid peroxides. These results suggest that the observed effects are, in fact, attributable to singlet oxygen, and not to hydrogen peroxide, superoxide radical, or hydroxyl radical.

Animals↗
PubMed1992

Singlet oxygen-induced inhibition of cardiac sarcolemmal Na+K(+)-ATPase.

We investigated the susceptibility of sarcolemmal Na+K(+)-ATPase to singlet oxygen. The role of this enzyme is regulation of Na+ concentration and thereby membrane potential. Inhibition of Na+ pump would lead to intracellular Ca2+ overload therefore further aggravating the injury caused by free radicals. Incubation of isolated sarcolemmal vesicles with irradiated rose bengal (150 nM) resulted in 86 +/- 1% inhibition of Na+K(+)-ATPase activity and histidine (25-100 mM) protected the enzyme in a dose-dependent fashion whereas SOD, catalase or mannitol (.OH radical scavenger) did not have any effect. Also, the inhibition of Na+K(+)-ATPase activity was dependent on rose bengal concentration, intensity of irradiation, duration of light exposure, showing that inhibition was directly related to amount of singlet oxygen generated. These results show that singlet oxygen may have significant disruptive effects on sarcolemmal function and may represent an important mechanism by which the oxidative injury to the myocardium induces arrhythmogenesis.

Animals↗
PubMed1993

Determination of singlet oxygen quantum yields with 1,3-diphenylisobenzofuran in model membrane systems.

The oxidation of 1,3-diphenylisobenzofuran by singlet oxygen was investigated in methanol and in two different types of liposomes. It was found that at high concentrations of scavenger 1,3-diphenylisobenzofuran, e.g., > 100 microM in methanol, the 1:1 oxidation stoichiometry is lost and more than one scavenger molecule per molecule of singlet oxygen is consumed. In model membrane systems, where local scavenger concentrations are high due to compartmentalization, correct singlet oxygen quantum yields with 1,3-diphenylisobenzofuran are only determined if the increased oxidation is taken into account.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1991

Biological consequences associated with DNA oxidation mediated by singlet oxygen.

Singlet oxygen is a major oxidative species that can be generated by numerous biological processes such as photosensitization. This oxidant can react with deoxyguanosine and with guanine in deoxyribonucleic acid (DNA) leading to the induction of at least four different reaction products such as 4,8-dihydro-4-hydroxy-8-oxodeoxyguanosine and 7,8-dihydro-8-oxodeoxyguanosine. The induction of true single-stranded breaks in the oxidated DNA is still a matter of controversy and is not yet clearly established. This paper focuses mainly on several biological consequences which can be associated with the induction of DNA lesions by singlet oxygen. Oxidated DNA loses its transformation efficiency probably because unrepaired lesions can partially inhibit DNA replication. Mutagenesis is one of the main effects induced by guanine oxidation products. Molecular analysis of mutated genes reveals that G to T transversions are the most frequent mutations; these are probably introduced in DNA by misincorporation of deoxyadenosine monophosphate (dAMP) opposite to the lesion. Efficient repair of these oxidated guanine residues can take place via specific glycosylase, endonuclease or the SOS network. However, the data concerning the toxicity of singlet oxygen for eukaryotic cells are not frequent enough in the literature to draw a clear picture of the effects of this activated species in several biologically revelant phenomena.

DNA Damage↗
PubMed1992

Enhancement of carotenoid-to-chlorophyll singlet energy transfer by carotenoid-carotenoid interaction.

The apparent quantum yield of singlet-singlet spirilloxanthin-to-bacteriochlorophyll a energy transfer increases linearly with the residual spirilloxanthin content in Rhodospirillum rubrum membrane vesicles from which this carotenoid has been partially removed. Since it has been previously shown that carotenoid-carotenoid interaction is a linear function of the residual spirilloxanthin level in the major pigment-protein complex of those vesicles (Zurdo, J., R. M. Lozano, C. Fernandez-Cabrera, and J. M. Ramirez. 1991. Biochem. J. 274:881-884), it appears that such degenerate interaction enhances singlet energy transfer. Part of the enhancement may be explained if the energy donor is the spirilloxanthin 1Bu----1Ag (S2----S0) transition, because exciton coupling probably brings its energy closer to that of the Qx (S2----S0) transition of bacteriochlorophyll. In contrast, it seems that the possible stabilization of the spirilloxanthin 2Ag (S1) state would hardly improve energy transfer, because this hidden state probably lies below the S1 bacteriochlorophyll state. In any case, the stabilizing effects of carotenoid-carotenoid interactions seem insufficient to explain the enhancement of energy transfer. Direct or indirect effects of carotenoid dimerization on the three-dimensional structure of the pigment cluster appear to be required to account for such enhancement.

Bacteriochlorophylls↗
PubMed2001

Inactivation of catalase and superoxide dismutase by singlet oxygen derived from photoactivated dye.

Both superoxide dismutase (SOD) and catalase are key enzymes in the antioxidant system of the cells that work to maintain low steady-state concentrations of the reactive oxygen species. When exposed to a singlet oxygen-producing system composed of dye, such as methylene blue or rose bengal, and visible light both SOD and catalase were susceptible to oxidative modification and damage as indicated by the loss of activity, fragmentation and aggregation of peptide as well as by the formation of carbonyl groups. Histidine, a powerful quenching agent for singlet oxygen, and the polyamines, such as spermine and spermidine, were effective at protecting the activity loss mediated by illuminated dye, whereas spin traps were only mildly effective. The structural alterations of modified enzymes were indicated by the increase in susceptibility to proteases, the change in absorption spectra and in fluorescence spectra. The singlet oxygen-mediated damage to SOD and catalase may result in the perturbation of cellular antioxidant defense mechanisms and subsequently lead to a pro-oxidant condition.

Animals↗