氧气常压介质阻挡放电的发射光谱及能量传递机理

为研究氧气常压介质阻挡放电中的物理化学行为, 以纯氧作为放电体系, 用发射光谱(optical emission spectroscopy)诊断技术分析了等离子体中可能存在的化学活性物种. 利用在500-950 nm范围的氧原子发射光谱计算出等离子体中的电子温度为(1.02±0.03) eV; 观测了760 nm处的具有清晰转动结构的氧气A带(atmospheric band)O2(b1∑+g-X3∑-g), 并用其转动结构计算了转动温度(气体温度)为(650±20) K; 在500-700 nm范围观测了氧气的第一负带系(first negative system) O+2(b4∑-g-a4∏u), 在190-240 nm范围观测了微弱但特征清晰的氧气的Hopfield带系O+2(c4∑+u-b4∑-g). 研究发现, 在氧气常压介质阻挡放电等离子体中存在多种激发态氧原子、激发态氧气分子、基态和激发态氧气分子离子等反应活性物种, 这些活性物种的形成涉及氧气分子的激发、解离和电离等多种过程, 每个过程都包含多个能量传递步骤, 氧分子解离产生的氧原子是导致一系列高激发态氧原子生成和氧气电离激发的主要因素.     

Subcellular, time-resolved studies of singlet oxygen in single cells

In time-resolved and spatially resolved experiments, singlet molecular oxygen, O2(a1Deltag), was created in a single nerve cell upon irradiation of a sensitizer incorporated in the cell using a focused laser beam. The singlet oxygen thus produced was detected by its infrared phosphorescence. Data obtained indicate that in both the cytoplasm and the nucleus of the cell, this reactive species is approximately 1-2 orders of magnitude longer-lived than previously believed. The data demonstrate that deactivation of singlet oxygen in the cell is dominated by interactions with the solvent not cellular constituents such as proteins. These results provide a new perspective for mechanistic studies of the role of O2(a1Deltag) in photoinduced cell death and intracellular signaling.     

Generation of singlet oxygen via the composites of water-soluble thiol-capped CdTe quantum dots-sulfonated aluminum phthalocyanines

Singlet oxygen (1O2), one of the reactive oxygen species, plays an important role in many biomedical applications. The various compounds including the phthalocyanines, quantum dots (QDs) and QD complex, which may have potential to produce 1O2, thus received more and more attentions in recent years. By means of the direct detection of near-infrared 1270 nm, we found that the water-soluble thiol-capped CdTe QDs can photoproduce 1O2 in deuterated water with a low quantum yield (QY) of 1%. When sulfonated aluminum phthalocyanines (AlSPc's) were connected to these QDs, forming water-soluble QD-Pc composites, the 1O2 QY of the composites increased to 15% under the excitation of 532 nm, while little 1O2 production can be found for AlSPc alone at the same excitation because of the poor absorption of AlSPc in this region. The results of indirect measurements of 1O2, obtained from the photodegradation of the 1O2 chemical trap anthracene-9,10-diyl-bis-methylmalonate (ADMA), confirmed 1O2 yields in both QD and QD-Pc composite solutions. The QD-Pc composites have the advantage of extending the excitation region to 400-600 nm with remarkably enhanced extinction coefficients as compared with that of AlSPc. Therefore QD-Pc composites can fully utilize visible region light excitation to effectively produce 1O2, which may facilitate the applications of QD-Pc composites in broad areas.     

Antibacterial activity of anthraquinone derivatives from Heterophyllaea pustulata (Rubiaceae)

Photosensitizing anthraquinones isolated from Heterophyllaea pustulata Hook f. (Rubiaceae), namely soranjidiol, rubiadin, damnacanthal and 5,5'-bisoranjidiol, showed antibacterial activity (bacteriostatic/bactericide) on Staphylococcus aureus. The mechanism of action seems to involve an increase in the levels of superoxide anion (O(2)(·-)) and/or singlet molecular oxygen ((1)O(2)). Moreover, the effect of actinic irradiation as a boosting agent for the production of both reactive species of oxygen as well as its influence on antibacterial activity was assessed. The routine susceptibility assay (minimum inhibitory concentration determination) was carried out by means of the broth macrodilution method. Bactericide activity was determined counting the colony-forming units per milliliter (cfu/mL) in plate. The O(2)(·-) production was determined by means of an indirect photobiological assay (Nitroblue Tetrazolium test), and the production of (1)O(2) was followed using an indirect steady-state method, with methionine as the (1)O(2) chemical quencher.     

Light effect and reactive oxygen species in the action of ciprofloxacin on Staphylococcus aureus

Oxygen consumption by Staphylococcus aureus ATCC 29213 sensitive to ciprofloxacin was determined with an oxygen selective electrode. Increase in the O(2) consumption was observed with 0.45 micromL(-1) ciprofloxacin while higher concentrations gave rise to a reduction of O(2) consumption. Resistant S. aureus strain did not show increase of O(2) consumption in presence of ciprofloxacin. Nitro Blue Tetrazolium assay showed that production of reactive oxygen species (ROS) increased intracellularly in sensitive bacteria incubated with this antibiotic. The exposition to UV light (360 nm) augmented the intracellular oxidative stress of S. aureus and provoked increment of ROS in extracellular media. Generation of singlet oxygen O(2) ((1)Delta(g)) in S. aureus was measured by means of oxidation of methionine. The absorbance of methionine was monitored at 215 nm and a clear decrease was detected when sensitive S. aureus was stressed with ciprofloxacin. Sodium azide and 2,5-dimethylfuran were used to reinforce the evidence of O(2) ((1)Delta(g)) generation during oxidative stress. Assays with methionine and 2,5-dimethylfuran demonstrated that resistant S. aureus did not increase the production of O(2) ((1)Delta(g)) in the presence of antibiotic. DNA oxidation was investigated in presence of O(2) ((1)Delta(g)) generated by laser excitation of perinaphthenone and subsequent energy transfer. Deactivation of O(2) ((1)Delta(g)) by reaction with DNA of sensitive and resistant bacteria was observed. According to the results obtained, the effect of ciprofloxacin in S. aureus led to an increment of O(2) ((1)Delta(g)) generating oxidative stress in the bacteria.     

Optical detection of singlet oxygen from single cells

The lowest excited electronic state of molecular oxygen, singlet molecular oxygen, O(2)(a (1)Delta(g)), is a reactive species involved in many chemical and biological processes. To better understand the roles played by singlet oxygen in biological systems, particularly at the sub-cellular level, optical tools have been developed to create and directly detect this transient state in time- and spatially-resolved experiments from single cells. Data obtained indicate that, contrary to common perception, this reactive species can be quite long-lived in a cell and, as such, can diffuse over appreciable distances including across the cell membrane into the extracellular environment. On one hand, these results demonstrate that the behavior of singlet oxygen in an intact cell can be significantly different from that inferred from model bulk studies. More generally, these results provide a new perspective for mechanistic studies of intra- and inter-cellular signaling and events that ultimately lead to photo-induced cell death.     

Antibody-catalyzed oxidation of delta(9)-tetrahydrocannabinol

Marijuana abuse continues to plague society and the lack of effective treatments warrants concern. Catalytic antibodies capable of oxidatively degrading the major psychoactive component of marijuana, Delta9-tetrahydrocannabinol (Delta9-THC), are presented. The antibodies generate reactive oxygen species from singlet oxygen (1O2*), using riboflavin (vitamin B2) and visible light as the 1O2* source. Cannabitriol was identified as the major degradation product of this reaction, demonstrating the ability of an antibody to catalyze a complex chemical transformation with therapeutic implications for treating marijuana abuse.     

Oxygen dependence of two-photon activation of zinc and copper phthalocyanine tetrasulfonate in Jurkat cells

Abstract Photodynamic therapy (PDT), the use of light-activated drugs, is a promising treatment of cancer as well as several nonmalignant conditions. However, the efficacy of one-photon (1-gamma) PDT is limited by hypoxia, which can prevent the production of the cytotoxic singlet oxygen ((1)O(2)) species, leading to tumor resistance to PDT. To solve this problem, we propose an irradiation protocol based on a simultaneous, two-photon (2-gamma) excitation of the photosensitizer (Ps). Excitation of the Ps triplet state leads to an upper excited triplet state T(n) with distinct photochemical properties, which could inflict biologic damage independent of the presence of molecular oxygen. To determine the potential of a 2-gamma excitation process, Jurkat cells were incubated with zinc or copper phthalocyanine tetrasulfonate (ZnPcS(4) or CuPcS(4)). ZnPcS(4) is a potent (1)O(2) generator in 1-gamma PDT, while CuPcS(4) is inactive under these conditions. Jurkat cells incubated with either ZnPcS(4) or CuPcS(4) were exposed to a 670 nm continuous laser (1-gamma PDT), 532 nm pulsed-laser light (2-gamma PDT), or a combination of 532 and 670 nm (2-gamma PDT). The efficacy of ZnPcS(4) to photoinactivate the Jurkat cells decreased as the concentration of oxygen decreased for both the 1-gamma and 2-gamma protocols. In the case of CuPcS(4), cell phototoxicity was measured only following 2-gamma irradiation, and its efficacy also decreased at a lower oxygen concentration. Our results suggest that for CuPcS(4) the T(n) excited state can be populated after 2-gamma irradiation at 532 nm or the combination of 532 and 670 nm light. Dependency of phototoxicity upon aerobic conditions for both 1-gamma and 2-gamma PDT suggests that reactive oxygen species play an important role in 1-gamma and 2-gamma PDT.     

Singlet oxygen-induced activation of Akt/protein kinase B is independent of growth factor receptors

Singlet oxygen (1O2)-induced cytotoxicity is believed to be responsible for responses to photodynamic therapy and for apoptosis of T helper cells after UV-A treatment. Other cytotoxic oxidants, such as hydrogen peroxide and peroxynitrite have been shown to stimulate cell survival signaling pathways in addition to causing cell death. Both these oxidants stimulate the Akt/protein kinase B survival signaling pathway through activation of membrane tyrosine kinase growth factor receptors. We evaluated the ability of 1O2 to activate the Akt/protein kinase B pathway in NIH 3T3 cells and examined potential activation pathways. Exposure of fibroblasts to 1O2 elicited a strong and sustained phosphorylation of Akt, which occurred concurrently with phosphorylation of p38 kinase, a proapoptotic signal. Inhibition of phosphatidylinositol-3-OH kinase (PI3-K) completely blocked Akt phosphorylation. Significantly, cell death induced by 1O2 was enhanced by inhibition of PI3-K, suggesting that activation of Akt by 1O2 may contribute to fibroblast survival under this form of oxidative stress. 1O2 treatment did not induce phosphorylation of platelet-derived growth factor receptor (PDGFR) or activate SH-PTP2, a substrate of growth factor receptors, suggesting that PDGFR was not activated. In addition, specific inhibition of PDGFR did not affect Akt phosphorylation elicited by 1O2. Activation of neither focal adhesion kinase (FAK) nor Ras protein, both of which mediate responses to reactive oxygen species, appeared to be pathways for the 1O2-induced activation of the PI3-K-Akt survival pathway. Thus, activation of Akt by 1O2 is mediated by PI3-K and contributes to a survival response that counteracts cell death after 1O2-induced injury. However, unlike the response to other oxidants, activation of the PI3-K-Akt by 1O2 does not involve activation of growth factor receptors, FAK or Ras protein.     

Core excitation in O3 localized to one of two symmetry-equivalent chemical bonds: molecular alignment through vibronic coupling

Core excitation from terminal oxygen OT in O3 is shown to be an excitation from a localized core orbital to a localized valence orbital. The valence orbital is localized to one of the two equivalent chemical bonds. We experimentally demonstrate this with the Auger-Doppler effect which is observable when O3 is core excited to the highly dissociative OT1s(-1)7a1 1 state. Auger electrons emitted from the atomic oxygen fragment carry information about the molecular orientation relative to the electromagnetic-field vector at the moment of excitation. The data together with analytical functions for the electron-peak profiles give clear evidence that the preferred molecular orientation for excitation only depends on the orientation of one bond, not on the total molecular orientation. The localization of the valence orbital "7a1" is caused by mixing of the valence orbital "5b2" through vibronic coupling of antisymmetric stretching mode with b2 symmetry. To the best of our knowledge, it is the first discussion of the localization of a core excitation of O3. This result explains the success of the widely used assumption of localized core excitation in adsorbates and large molecules.     

Direct 1270 nm irradiation as an alternative to photosensitized generation of singlet oxygen to induce cell death

This article is a highlight of the paper by Anquez et al. in this issue of Photochemistry and Photobiology and describes the potential benefits of direct excitation of molecular oxygen to produce singlet oxygen ((1)O(2)) rather than using a photosensitizer. Due to its simplicity, the direct excitation of molecular oxygen can potentially overcome problems associated with systemic administration of dyes, such as skin photosensitivity and the clearance of free sensitizer from the body. However, concerns associated with the technique include indiscriminate generation of extracellular and intracellular (1)O(2), the difficulty of controlling necrotic vs apoptotic cell death and the possible consequences of thermal effects.     

Reactivity of V2O3(0001) surfaces: molecular vs dissociative adsorption of water

The adsorption of water on V2O3(0001) surfaces has been investigated by thermal desorption spectroscopy, high-resolution electron energy loss spectroscopy, and X-ray photoelectron spectroscopy with use of synchrotron radiation. The V2O3(0001) surfaces have been generated in epitaxial thin film form on a Rh(111) substrate with three different surface terminations according to the particular preparation conditions. The stable surface in thermodynamic equilibrium with the bulk is formed by a vanadyl (VO) (1x1) surface layer, but an oxygen-rich (radical3xradical3)R30 degrees reconstruction can be prepared under a higher chemical potential of oxygen (microO), whereas a V-terminated surface consisting of a vanadium surface layer requires a low microO, which can be achieved experimentally by the deposition of V atoms onto the (1x1) VO surface. The latter two surfaces have been used to model, in a controlled way, oxygen and vanadium containing defect centres on V2O3. On the (1x1) V=O and (radical3xradical3)R30 degrees surfaces, which expose only oxygen surface sites, the experimental results indicate consistently that the molecular adsorption of water provides the predominant adsorption channel. In contrast, on the V-terminated (1/radical3x1/radical3)R30 degrees surface the dissociation of water and the formation of surface hydroxyl species at 100 K is readily observed. Besides the dissociative adsorption a molecular adsorption channel exists also on the V-terminated V2O3(0001) surface, so that the water monolayer consists of both OH and molecular H2O species. The V surface layer on V2O3 is very reactive and is reoxidised by adsorbed water at 250 K, yielding surface vanadyl species. The results of this study indicate that V surface centres are necessary for the dissociation of water on V2O3 surfaces.     

Skin photosensitizing agents and the role of reactive oxygen species in photoaging.

In this paper, the role of reactive oxygen species in photoaging is presented. Many photosensitizing agents are known to generate reactive oxygen species (singlet oxygen (1O2), superoxide anion (O2.-) and .OH radicals). Although photoaging (dermatoheliosis) of human skin is caused by UVB and UVA radiation, the hypothesis tested here in the pathogenesis of photoaging of human skin is the free radical theory involving the generation of reactive oxygen species by UVA (320-400 nm) radiation and their damaging oxidative effects on cutaneous collagen and other model proteins. The UVA-generated reactive oxygen species cause cross-linking of proteins (e.g. collagen), oxidation of sulfydryl groups causing disulfide cross-links, oxidative inactivation of certain enzymes causing functional impairment of cells (fibroblasts, keratinocytes, melanocytes, Langerhans cells) and liberation of proteases, collagenase and elastase. The skin-damaging effects of UVA appear to result from type II, oxygen-mediated photodynamic reactions in which UVA or near-UV radiation in the presence of certain photosensitizing chromophores (e.g., riboflavin, porphyrins, nicotinamide adenine dinucleotide phosphate (NADPH), etc.) leads to the formation of reactive oxygen species (1O2, O2.-, .OH). Four specific observations are presented to illustrate the concept: (1) the production of 1O2 and O2.- by UVB, UVA and UVA plus photosensitizing agents (such as riboflavin, porphyrin and 3-carbethoxypsoralens) as a function of UV exposure dose, the sensitizer concentration and the pH of the irradiated solution; (2) the formation of protein cross-links in collagen, catalase and superoxide dismutase by 1O2 and O2.- (.OH) and the resulting denaturation of proteins and enzyme activities as a function of UVA exposure dose; (3) the protective role of selective quenchers of 1O2 and O2.- (e.g. alpha-tocopherol acetate, beta-carotene, sodium azide, ascorbic acid, etc.) against the photoinactivation of enzymes and the prevention of the protein cross-linking reaction; (4) the possible usefulness of certain antioxidants or quenchers that interact with the UVA-induced generation of reactive oxygen species in the amelioration of the process of photoaging.     

Oxygen precursor to the reactive intermediate in methanol synthesis by Cu-ZSM-5

The reactive oxidizing species in the selective oxidation of methane to methanol in oxygen activated Cu-ZSM-5 was recently defined to be a bent mono(μ-oxo)dicopper(II) species, [Cu(2)O](2+). In this communication we report the formation of an O(2)-precursor of this reactive site with an associated absorption band at 29,000 cm(-1). Laser excitation into this absorption feature yields a resonance Raman (rR) spectrum characterized by (18)O(2) isotope sensitive and insensitive vibrations, νO-O and νCu-Cu, at 736 (Δ(18)O(2) = 41 cm(-1)) and 269 cm(-1), respectively. These define the precursor to be a μ-(η(2):η(2)) peroxo dicopper(II) species, [Cu(2)(O(2))](2+). rR experiments in combination with UV-vis absorption data show that this [Cu(2)(O(2))](2+) species transforms directly into the [Cu(2)O](2+) reactive site. Spectator Cu(+) sites in the zeolite ion-exchange sites provide the two electrons required to break the peroxo bond in the precursor. O(2)-TPD experiments with (18)O(2) show the incorporation of the second (18)O atom into the zeolite lattice in the transformation of [Cu(2)(O(2))](2+) into [Cu(2)O](2+). This study defines the mechanism of oxo-active site formation in Cu-ZSM-5.     

Production of oxygen by electronically induced dissociations in ice

A solid-state chemical model is given for the production of O2 by electronic excitation of ice, a process that occurs on icy bodies in the outer solar system. Based on a review of the relevant available laboratory data, we propose that a trapped oxygen atom-water complex is the principal precursor for the formation of molecular oxygen in low-temperature ice at low fluences. Oxygen formation then occurs through direct excitation of this complex or by its reaction with a freshly produced, nonthermal O from an another excitation event. We describe a model for the latter process that includes competition with precursor destruction and the effect of sample structure. This allows us to put the ultraviolet photon, low-energy electron, and fast-ion experiments on a common footing for the first time. The formation of the trapped oxygen atom precursor is favored by the preferential loss of molecular hydrogen and is quenched by reactions with mobile H. The presence of impurity scavengers can limit the trapping of O, leading to the formation of oxygen-rich molecules in ice. Rate equations that include these reactions are given and integrated to obtain an analytic approximation for describing the experimental results on the production and loss of molecular oxygen from ice samples. In the proposed model, the loss rate varies, roughly, inversely with solid-state defect density at low temperatures, leading to a yield that increases with increasing temperature as observed. Cross sections obtained from fits of the model to laboratory data are evaluated in light of the proposed solid-state chemistry.     

Singlet oxygen in the environmental sciences

This review of the part played by the singlet states of molecular oxygen in the environment deals with atmospheric aspects. There are five bound excited states of molecular oxygen that correlate with two ground state, ³P, oxygen atoms. Of these, three are singlets, although the other two states (triplets) are closely associated with singlet oxygen processes, especially in the mesosphere. A weakly bound quintet state has been invoked, as well, in explaining some aspects of the physical chemistry of the singlet species. Of the three singlet states, the a¹Δ_g is the most familiar. It has a low excitation energy, a long radiative lifetime, and is rather resistant to collisional deactivation in the gas phase. As a consequence, its chemistry has been susceptible to detailed study in the laboratory. These investigations, coupled with estimates of production rates, suggest that O₂(a¹Δ_g) is probably not important in initiating much chemical change in the lower atmosphere, at least in the gas phase; excited molecules dissolved in water droplets may promote chemical change under special circumstances. In the stratosphere and mesosphere, each of the bound excited states gives rise to characteristic emission features of the airglow, both by day and by night. The observational data, obtained from the ground, and from balloons, high-flying aircraft, rockets and satellites is surveyed as a background to examining the chemical and photochemical mechanisms by which the different states become excited. These mechanisms clearly differ by day and by night, and they also depend on the altitude from which the emission comes. The most intense feature of the oxygen dayglow, the Infrared Atmospheric Band, comes from O₂(a¹Δ_g) that is produced in the photolysis of ozone. Because dayglow measurements are sometimes used to derive ozone concentrations and altitude profiles in the atmosphere, the efficiency of production of the species in the photolysis of ozone is examined critically, and some unexpected laboratory findings are reported. The b¹Σ⁺ _g state of oxygen is excited during the day largely by resonance scattering, although some is also populated by energy transfer from O(¹D) to O₂. At night, recombination of O(³P) atoms is the most likely source of excitation of all the states of oxygen. Laboratory experiments that bear on these processes are reviewed, and theoretical estimates of the partitioning of recombination events between the different states are presented. Direct recombination into the a¹Δ_g and b¹Σ⁺ _g states is unlikely to be efficient enough to produce the observed concentrations of these species, and some indirect process is thus implicated. Laser excitation experiments show that quenching of the three higher excited (ungerade) states of oxygen by O₂ and, especially, N₂, can generate O₂(b¹Σ⁺ _g) with high efficiency; similar experiments demonstrate explicitly that the quenching of O₂(b¹Σ⁺ _g) by the atmospheric gases yields O₂(a¹Δ_g). A consistent excitation scheme for the nightglow emissions is presented; this scheme also pays attention to the “auroral green” line produced by the ¹S state of atomic oxygen, the intensities of which in the atmospheres of Earth and Venus provide some clues about the excitation of the molecular states. Finally, the laboratory studies are shown to indicate that the formation of excited molecular oxygen from vibrationally rich hydroxyl (OH) radicals is unlikely to be of major importance in the atmosphere.     

A FRET-based approach to ratiometric fluorescence detection of hydrogen peroxide

We report the synthesis, properties, and biological applications of Ratio-Peroxyfluor-1 (RPF1), a new ratiometric fluorescent reporter for hydrogen peroxide. RPF1 is comprised of a two-fluorophore cassette, where the spectral overlap between coumarin donor and fluoran/fluorescein acceptor partners can be controlled by the chemoselective peroxide-mediated deprotection of boronic ester pendants on the acceptor dye. RPF1 features good selectivity for hydrogen peroxide over a variety of reactive oxygen species, including superoxide and nitric oxide, a ca. 8-fold increase in fluorescence intensity ratio (lambda517/lambda464) upon H2O2 reaction, and excitation and emission profiles in the visible region. Experiments with viable yeast mitochondria show that RPF1 can monitor and quantify endogenous production of H2O2, establishing the potential utility of this approach for probing peroxide biology in living systems.     

Lifetime and diffusion of singlet oxygen in a cell

In time- and spatially resolved experiments, singlet molecular oxygen, O(2)(a(1)Delta(g)), was created in a single nerve cell upon irradiation of a sensitizer incorporated in the cell nucleus using a focused laser beam. The singlet oxygen thus produced was detected by its infrared phosphorescence. Data obtained indicate that, contrary to common perception, this reactive species can be quite long-lived in a cell and, as such, can diffuse over appreciable distances including across the cell membrane into the extra-cellular environment. These results provide a new perspective for mechanistic studies of photoinduced cell death and intracellular signaling.     

磷酸化对D1蛋白7900和9300 降解片段的影响

利用Western blotting技术对未磷酸化和磷酸化光合系统Ⅱ(PSⅡ)膜中D1蛋白的7900和9300降解片段进行了检测. 结果表明, 超氧阴离子、 过氧化氢和羟基自由基参与了未磷酸化和磷酸化D1蛋白的7900和9300片段的产生. 磷酸化能够部分抑制D1蛋白7900和9300片段的产生, 从而对D1蛋白起到保护作用.     

Fluorophotometric determination of hydrogen peroxide and other reactive oxygen species with fluorescein hydrazide (FH) and its crystal structure

Methods for the fluorophotometric determination of hydrogen peroxide (H(2)O(2)) and other reactive oxygen species (ROS) were proposed by using the fluorescence reaction between H(2)O(2) or other ROS and fluorescein hydrazide (FH). In the determination of H(2)O(2), the calibration curve exhibited linearity over the H(2)O(2) concentration range of 2.1-460 ng ml(-1) at an emission wavelength of 527 nm with an excitation of 460 nm and with the relative standard deviations (n=6) of 4.06%, 1.78%, and 2.21% for 3.1 ng ml(-1), 30.8 ng ml(-1), and for 308 ng ml(-1) of H(2)O(2), respectively. The detection limit for H(2)O(2) was 0.7 ng ml(-1) due to three blank determinations (rho=3). The calibration curves for ROS-related compounds were also constructed under the optimum conditions. This method was successfully applied in the assay of H(2)O(2) in human urine. In addition, we performed the characterization of FH, and interesting information was obtained with regard to the relationship between the chemical structure and fluorescence.