Specific Quencher Research Articles

Sulfadiazine degradation by hydroxyl radical and direct electron transfer pathways in the self-prepared boron doped diamond electrochemical process

Sulfonamide antibiotics are frequently detected in livestock wastewater, seriously harming the ecological environment and human health. Boron-doped diamond (BDD) electrochemical process has prominent potential in degrading organic pollutants from special industrial wastewater. In this work, the degradation efficiency and mechanism for sulfadiazine (SDZ) with the prepared BDD electrode were investigated. Scanning electron microscopy (SEM) and Raman spectroscopy revealed a 2 μm thick, compact, and crack-free BDD film on silicon. The BDD's oxygen evolution potential was 1.47 V. About 93.3 % of SDZ in the synthetic wastewater was removed under the conditions of a current density of 40 mA/cm2, electrode spacing of 20 mm, electrolyte concentration of 40 mM, and an initial pH of 8. Hydroxyl radical and direct electron transfer (DET) mainly contributed to SDZ degradation based on specific quencher tests and electrochemical analysis. The possible transformation pathways of SDZ were proposed according to the detected oxidation products and DFT calculation, mainly including amino hydroxylation, sulfur dioxide extrusion, and pyrimidine heterocyclic ring opening. Furthermore, the toxicity of intermediates products markedly weakened compared to that of SDZ. The presence of ion chloride could slightly improve the removal of SDZ, while bicarbonate and phosphate inhibited the SDZ degradation. In addition, the efficient removal of chemical oxygen demand and SDZ in the effluent of aerobic biological treatment effluent of actual livestock wastewater was confirmed. To sum up, BDD electrochemical oxidation is a viable approach for the advanced treatment of livestock wastewater.

Fluorescent Probes and Quenchers in Studies of Protein Folding and Protein-Lipid Interactions.

Fluorescence spectroscopy provides numerous methodological tools for structural and functional studies of biological macromolecules and their complexes. All fluorescence-based approaches require either existence of an intrinsic probe or an introduction of an extrinsic one. Moreover, studies of complex systems often require an additional introduction of a specific quencher molecule acting in combination with a fluorophore to provide structural or thermodynamic information. Here, we review the fundamentals and summarize the latest progress in applications of different classes of fluorescent probes and their specific quenchers, aimed at studies of protein folding and protein-membrane interactions. Specifically, we discuss various environment-sensitive dyes, FRET probes, probes for short-distance measurements, and several probe-quencher pairs for studies of membrane penetration of proteins and peptides. The goals of this review are: (a) to familiarize the readership with the general concept that complex biological systems often require both a probe and a quencher to decipher mechanistic details of functioning and (b) to provide example of the immediate applications of the described methods.

Acid-induced improvement of photosensitizing efficiency of porphyrins under heterogeneous aqueous conditions: High photosensitizing activity, dissociative stability and photooxidative durability

Meso-tetrakis(N-methylpyridinium-3-yl)porphyrin (H2TMPyP), electrostatically supported on the sodium salt of amberlyst 15 nanoparticles (nanoAmbSO3Na) was protonated with very weak (CH3COOH), weak (CH2ClCOOH, CHCl2COOH) and strong (CF3COOH) carboxylic acids and H2SO4 to prepare a series of new photosensitizers. NanoAmbSO3@H2TMPyP(HA)2 compounds were quite stable after separation from the aqueous solution and drying, even in the case of nanoAmbSO3@H2TMPyP(CH3COOH)2. The diacids were characterized by DR-UV–vis, AFM, TGA and DLS and used as photosensitizers in aerobic photooxidation of 1,5-dihydroxynaphthalene (DHN) and methyl phenyl sulfide. Almost no catalyst degradation was observed for the diacids in the oxidation of DHN after five successive runs. Also, the catalyst degradation was in the range of 0–68% in the oxidation of methyl phenyl sulfide at the end of the 5th run. The catalyst stability decreased as nanoAmbSO3@H2TMPyP(CF3COOH)2 >> nanoAmbSO3@H2TMPyP(CHCl2COOH)2 > nanoAmbSO3@H2TMPyP(H2SO4)2 > nanoAmbSO3@H2TMPyP(CH3COOH)2 > nanoAmbSO3@H2TMPyP(CH2ClCOOH)2. It is noteworthy that under the same conditions, ca. 50% of the non-protonated porphyrin, nanoAmbSO3@H2TMPyP, was degraded after 2 h, at the end of the first run. In other words, the formation of nanoAmbSO3@H2TMPyP(HA)2 species was associated with a significant increase in both the photocatalytic activity and oxidative stability of nanoAmbSO3@H2TMPyP, regardless of the type and strength of the acid used for diprotonation of the porphyrin. In the oxidation of methyl phenyl sulfide, nanoAmbSO3@H2TMPyP(CF3COOH)2 and nanoAmbSO3@H2TMPyP(CH2ClCOOH)2 were the most efficient catalysts of the series. The singlet oxygen quantum yields (ϕΔ), determined chemically by using 1,3-diphenylisobenzofuran as a specific quencher of singlet oxygen showed ϕΔ in the range of 0.51–0.98 for nanoAmbSO3@H2TMPyP(HA)2 and 0.66 for nanoAmbSO3@H2TMPyP.

Ultrasound/chlorine sono-hybrid-advanced oxidation process: Impact of dissolved organic matter and mineral constituents

In this work, after exploring the first report on the synergism of combining ultrasound (US: 600 kHz) and chlorine toward the degradation of Allura Red AC (ARAC) textile dye, as a contaminant model, the impact of various mineral water constituents (Cl−, SO42−, NO3−, HCO3− and NO2−) and natural organic matter, i.e., humic acid (HA), on the performance of the US/chlorine sono-hybrid process was assessed for the first time. Additionally, the process effectiveness was evaluated in a real natural mineral water (NMW) of a known composition. Firstly, it was found that the combination of ultrasound and chlorine (0.25 mM) at pH 5.5 in cylindrical standing wave ultrasonic reactor (f = 600 kHz and Pe = 120 W, equivalent to PA ∼ 2.3 atm) enhanced in a drastic manner the degradation rate of ARAC; the removal rate being 320% much higher than the arithmetic sum of the two separated processes. The source of the synergistic effect was attributed to the effective implication of reactive chlorine species (RCS: Cl, ClO and Cl2−) in the degradation process. Radical probe technique using nitrobenzene (NB) as a specific quencher of the acoustically generated hydroxyl radical confirmed the dominant implication of RCS in the overall degradation rate of ARAC by US/chlorine system. Overall, the presence of humic acid and mineral anions decreased the efficiency of the sono-hybrid process; however, the inhibition degrees depend on the type and the concentration of the selected additives. The reaction of these additives with the generated RCS is presumably the reason for the finding results. The inhibiting effect of Cl−, SO42−, NO3− and NO2− was more pronounced in US/chlorine process as compared to US alone, whereas the inverse scenario was remarked for the effect of HA. These outcomes were associated to the difference in the reactivity of HA and mineral anions toward RCS and OH oxidizing species, in addition to the more selective character of RCS than hydroxyl radical. The displacement of the reaction zone with increasing the additive concentration may also be another influencing factor that favors competition reactions, which subsequently reduce the available reactive species in the reacting medium. The NMW exerted reductions of 43% and 10% in the process efficiency at pH 5.5 and 8, respectively, thereby confirming the RCS-quenching mechanism by the water matrix constituents. Hence, this work provided a precise understanding of the overall mechanism of chlorine activation by ultrasound to promote organic compounds degradation in water.

Effect of Quencher, Geometry, and Light Outcoupling on the Determination of Exciton Diffusion Length in Nonfullerene Acceptors

The correct determination of the exciton diffusion length (LD) in novel organic photovoltaics (OPV) materials is an important, albeit challenging, task required to understand these systems. Herein, a high‐throughput approach to probe LD in nonfullerene acceptors (NFAs) is reported, that builds upon the conventional photoluminescence (PL) surface quenching method using NFA layers with a graded thickness variation in combination with spectroscopic PL mapping. The method is explored for two archetypal NFAs, namely, ITIC and IT‐4F, using PEDOT:PSS and the donor polymer PM6 as two distinct and practically relevant quencher materials. Interestingly, conventional analysis of quenching efficiency as a function of acceptor layer thickness results in a threefold difference in LD values depending on the specific quencher. This discrepancy can be reconciled by accounting for the differences in light in‐ and outcoupling efficiency for different multilayer architectures. In particular, it is shown that the analysis of glass/acceptor/PM6 structures results in a major overestimation of LD, whereas glass/acceptor/PEDOT:PSS structures give no significant contribution to outcoupling, yielding LD values of 6−12 and 8−18 nm for ITIC and IT‐4F, respectively. Hence, practical guidelines for quencher choice, sample geometries, and analysis approach for the accurate assessment of LD are provided.

Vitamin K5 Is an Efficient Photosensitizer for Ultraviolet a Light Inactivation of Bacteria

Photodynamic inactivation of bacteria has been proven as an effective method to inactivate pathogenic bacteria. This study identified vitamin K5 (VK5) as an efficient photosensitizer for ultraviolet light A (UVA) induced bacterial inactivation.Six species of bacteria, including Bacillus cereus (vegetative form), Escherichia coli , Pseudomonas aeruginosa, Staphylococcus aureus , Staphylococcus epidermidis , Klebsiella pneumoniae , and two species of antibiotic-resistant bacteria, Pseudomonas aeruginosa and Staphylococcus aureus, were grown and mixed with VK5 and irradiated with UVA in phosphate buffered saline (PBS) in 6-well plates following our previous procedures (Xu & Vostal, 2014). A representative figure of bacterial reduction of VK5 and UVA irradiation treated E. coli , as determined by a colony forming unit (CFU) count, is shown in Figure 1. Increasing concentrations of VK5 from 0 to 1600 µmol l-1 with fixed UVA irradiation doses produce a concentration-depended reduction of bacteria. Similarly, a UVA dose response for bacterial reduction is evident with fixed VK5 concentrations. As shown in Table 1, UVA irradiation (5.8 J cm-2) with vitamin K5 (1600 µmol l-1) reduced the CFU of bacteria by three to seven logs. Antibiotic resistant bacteria (Pseudomonas A. and Staphylococcus A ) did not exhibit resistance to the bactericidal effects of UVA and vitamin K5 combination treatment.Efficacy of VK5 and UVA for bacterial reduction was also evident in plasma although higher concentrations of VK5 and UVA doses were required. VK5 (500 or 2000 µ mol l-1 ) in 35% or 50% bacteria spiked plasma diluted with Platelet Additive Solutions was exposed to UVA irradiation at 6 and 30 J cm-2. This treatment reduced Escherichia coli and Staphylococcus aureus CFU by up to seven logs as shown in Figures 2a and 2b, respectively.Reactive oxygen species, hydroxyl radicals (˙OH) and superoxide anion radicals (O2˙−), were found generated in vitamin K5 aqueous solution after UVA irradiation, suggesting these oxygen species may mediate the inactivation of the bacteria. The O2˙−was generated in UVA-irradiated-VK5 PBS solution. At a fixed UVA dose of 2.9 J cm-2, the generation of O2˙− coincided with an increase in VK5 concentration from 0 to 1000 µ mol l-1 (Figure 3a). The generation of O2˙− was further confirmed by carrying out quenching study with superoxide dismutase (SOD) as specific quenchers. The production of O2˙− was reduced as the SOD concentration was increased from 0 to 640 units ml-1 in a 500 µ mol l-1 VK5 solution irradiated with a UVA (2.9 J cm-2 ) (Figure 3b). VK5 and UVA light combination also caused the release of ˙OH as the VK5 concentrations increased from 0 to 1000 µ mol l-1 with a fixed UVA dose of 2.9 J cm-2 The generation of ˙OH was further confirmed by mannitol, a specific quencher for ˙OH. Less ˙OH was produced when mannitol concentration was increased from 0 to 1 mol l-1, in the presence of a fixed VK5 concentration of 500 µ mol l-1 and a UVA dose of 2.9 J cm-2.Vitamin K5 and UVA light treatment is an effective method for reduction of bacteria in solutions including plasma and may be an effective way to reduce transfusion transmitted septic reactions from contaminated plasma products. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Commentary: Chemiexcitation of melanin derivatives induces DNA photoproducts long after UV exposure.

Commentary: Chemiexcitation of melanin derivatives induces DNA photoproducts long after UV exposure.

Quenchers and inhibitors of chemiluminescence in the reduction reactions of Mn3+

The effect of NaF and CH3CN on the chemiluminescent reactions of Mn(III) reduction in solutions of sulfuric acid is studied. It is established that NaF is an inhibitor of these reactions, and the quenching of chemiluminescence under the effect of NaF is nominal. Acetonitrile does not affect the kinetics of reactions under similar conditions and acts as a specific quencher of the chemiexcited emitter. The Stern-Volmer quenching constant is 52 ± 11 M−1.

Singlet oxygen mediated DNA damage induced phototoxicity by ketoprofen resulting in mitochondrial depolarization and lysosomal destabilization

Ketoprofen (KP) is a widely used nonsteroidal anti-inflammatory drug for the treatment of osteoarthritis and various rheumatic diseases. Currently, KP is applied topically on skin as gel to treat symptoms of pain and inflammation. We have studied the photomodification of KP under natural environmental conditions. KP generates reactive oxygen species (ROS) like 1O2 through Type-II photodynamic reaction. 1O2 mediated 2′-dGuO photodegradation, single and double strand breakage were significantly induced by photosensitized KP under sunlight/UV-R exposure. Significant intracellular ROS generation was measured through DCF-DA fluorescence. Linoleic acid photoperoxidation and role of 1O2 were substantiated by using specific quencher like sodium azide. KP induced cell cycle arrest in G2/M phase and cell death through MTT assay. We found apoptosis as the pattern of cell death which was confirmed through caspase-3 activation, cytochrome-c release from mitochondria, up-regulation of Bax protein and phosphatidylserine translocation. Our RT-PCR result strongly supports our view point of apoptotic cell death through up-regulation of p21 and pro-apoptotic Bax genes expression. Mitochondrial depolarization and lysosomal destabilization were also parallel to apoptotic process. Therefore, much attention should be paid to the topical application of KP and sunlight exposure in the light of skin related photosensitivity and cancers.

Role of type-II pathway in apoptotic cell death induction by photosensitized CDRI-97/78 under ambient exposure of UV-B

Novel trioxane 97/78, developed by Central Drug Research Institute (CDRI), Lucknow has shown promising antimalarial activity. Clinical experience of anti-malarial drugs registered the occurrence of phototoxicity in patients exposed with sunlight subsequent to medication. Photodegradation study has identified one photo-product up to 4h under UV-B/Sunlight by LC–MS/MS. UV-B irradiated 97/78 compound produced 1O2 via type-II dependent reaction mechanism, corroborated by its specific quencher. 2′-dGuO degradation and % tail development in photochemical as well as comet test, advocated the genotoxic potential of 97/78. The photocytotoxicity assays (MTT and NRU) on HaCaT cell line revealed the considerable decline in cell viability by 97/78. Cell cycle and Annexin V/PI double stain along with AO/EB demonstrated the G2/M phase arrest and apoptosis. Significant caspase-3 activity was measured in photoexcited 97/78 by colorimetric assay. Fluorescence stain with AO/JC-1 confirmed the lysosomal disruption and mitochondrial membrane destabilization by UV-B irradiated 97/78. Gene expression by RT-PCR showed significant upregulation of p21 and pro-apoptotic Bax, but no change observed in Bcl-2. In conclusion, the study highlights ROS mediated DNA damage, lysosomal and mitochondrial destabilization via upregulation of Bax and activation of caspase-3 which further leads to apoptosis.

P27: Significance of AMPK–eNOS pathway in renal protective effects of nitrite

Background Our daily meals contain significant amount of nitrate and nitrite, especially in vegetables. Recent studies have demonstrated beneficial effects of dietary nitrite in the treatment of cardiovascular related disease and hypertension. Nitrite has been believed to a waste form of nitric oxide (NO) though, nitrite could be a source of NO independently of conventional NO synthase (NOS) especially under hypoxic conditions. We have previously shown blood pressure lowering effect and glomerular protective effects of dietary nitrite administration in l -NAME, a NOS inhibitor, -treated animals, and concluded these phenomena were responsible for nitrite derived NO. NOS is still a dominant enzyme leading to NO production under normoxic conditions though, there are few reports whether nitrite affects NOS activity or not. Therefore we here revisited the function of nitrite in endotherial NOS (eNOS) action to clarify whether NOS plays a significant role in the renal protective effects of nitrite. Method and results We used human glomerular endotherial cells (HGEC) and explored eNOS-related molecules mainly by western blotting in this study. Nitrite stimulation increased phosphorylation of eNOS in HGEC in a dose-responsive manner, suggesting its activation by nitrite. Stimulation by nitrate did not cause eNOS phosphorylation. We then studied eNOS-phosphorylating molecules and found that nitrite stimulation led to phosphorylation of a catalytic subunit of 5′ AMP-activated protein kinase (AMPK), also suggesting its activation by nitrite. Phosphorylation of acetyl-CoA carboxylase, a typical substrate of AMPK, was also enhanced in the nitrite-stimulated HGEC. The phosphorylation of eNOS was curtailed by a specific inhibitor of AMPK, BML-275, while carboxy-PTIO, a specific quencher of NO, did not inhibit the AMPK phosphorylation by nitrite. Intracellular ATP levels were unchanged by nitrite stimulation. Conclusion Our data suggest that nitrite stimulation should lead to AMPK activation in normoxic endothelial cells without affecting intracellular energy levels, and it should be independent of NO. The activated AMPK should phosphorylate the downstream eNOS, leading to enhancement of NO production by the eNOS activation. In conclusion, we found that nitrite activates AMPK–eNOS pathway in HGEC. The activation of AMPK–eNOS pathway in endotherial cells is supposed to play a significant renal protective role in the nitrite action in addition to the NOS-independent NO production by nitrite. Disclosure Supported by Ministry of Education, Culture, Sports, Science and Technology.

Singlet oxygen mediated apoptosis by anthrone involving lysosomes and mitochondria at ambient UV exposure

Anthrone a tricyclic aromatic hydrocarbon which is toxic environmental pollutant comes in the environment through photooxidation of anthracene. We have studied the photomodification of anthrone under environmental conditions. Anthrone generates reactive oxygen species (ROS) like 1O2 through Type-II photodynamic reaction. Significant intracellular ROS generation was measured through dichlorohydrofluorescein fluorescence intensity. The generation of 1O2 was further substantiated by using specific quencher like sodium azide. UV induced photodegradation of 2-deoxyguanosine and photoperoxidation of linoleic acid accorded the involvement of 1O2 in the manifestation of anthrone phototoxicity. Phototoxicity of anthrone was done on human keratinocytes (HaCaT) through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and neutral red uptake assays. Anthrone induced cell cycle arrest (G2/M-phase) and DNA damage in a concentration dependent manner. We found apoptosis as a pattern of cell death which was confirmed through sub-G1 fraction, morphological changes, caspase-3 activation, acridine orange/ethidium bromide staining and phosphatidylserine translocation. Mitochondrial depolarization and lysosomal destabilization was parallel to apoptotic process. Our RT-PCR results strongly supports our view point of apoptotic cell death through up-regulation of pro-apoptotic genes p21 and Bax, and down regulation of anti-apoptotic gene Bcl2. Therefore, much attention should be paid to concomitant exposure of anthrone and UV-R for its total environmental impact.

Sodium azide as a specific quencher of singlet oxygen during chemiluminescent detection by luminol andCypridinaluciferin analogues

Reactive oxygen species (ROS) are presently thought to play important role in an increasing number of the physiological and pathological processes in living organisms. Various chemiluminescent (CL) compounds have been studied in order to find suitable and specific probes for the detection of particular ROS species. The CL of luminol is known to be non-specific and can be induced by various oxidants. Two Cypridina luciferin analogues, CLA and MCLA, have been used for the detection of ROS in vivo. CLAs are thought to emit light only when reacting with superoxide and singlet oxygen. It is possible to distinguish the particular ROS by using a specific quencher or scavenger, e.g. superoxide dismutase (SOD) or sodium azide (NaN(3)). The CL reactions of luminol (3-aminophthalhydrazide), CLA [2-methyl-6-phenyl-3,7-dihydroimidazo(1,2α) pyrazin-3-one] and MCLA [2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo(1,2α) pyrazin-3-one] were studied in three hydrogen peroxide decomposition systems (H(2)O(2)-HRP; H(2)O(2)-CuSO(4); and H(2)O(2)-NaOCl). The measurements were carried out in phosphate buffer, pH 7.4, at 25°C, using a luminometer (Fluoroskan Ascent FL and Sirius C). NaN(3) was used as the specific quencher of singlet oxygen. The results demonstrate that the proclaimed specificity of the CL of Cypridina luciferin analogues towards singlet oxygen has to be discussed.

Photoreactions of p-Quinones with Dimethyl Sulfide and Dimethyl Sulfoxide in Aqueous Acetonitrile†

The effects of dimethyl sulfide (DMS) and dimethyl sulfoxide (DMSO) on the photoreactions of 1,4-benzoquinone (BQ), 1,4-naphthoquinone (NQ), 9,10-anthraquinone (AQ) and several derivatives in acetonitrile/water were studied. The observed triplet state of the quinones is quenched and the rate constant is close to the diffusion-controlled limit for reactions of most quinones with DMS and lower with DMSO. Semiquinone radical anions (Q*-) produced by electron transfer from sulfur to the triplet quinone were detected. For both DMS and DMSO the yield of Q*- is similar, being generally low for BQ and NQ, substantial for AQ and largest for chloranil. The specific quencher concentrations and the effects of quinone structure and redox potentials on the time-resolved photochemical properties are discussed.

Controlling the Energy and Electron Transfer in a Novel Ruthenium Bipyridyl Complex: An ESR Study

A novel ruthenium complex has been synthesized. It is composed of three bipyridyl ligands, one of which is modified and has two hydroxamate groups. Photoexcitation of the complex with blue light (λmax = 477 nm) leads to the formation of a long-lived nitroxyl radical on hydroxamate as was detected and characterized by ESR. In anaerobic conditions, the radical was not formed, suggesting that a reactive oxygen species is required for generating the nitroxyl radical. The quenching of the excited state of ruthenium bipyridyl complexes by molecular oxygen can generate either singlet oxygen via energy transfer or superoxide radical via electron transfer. In this latter case the superoxide radical is confined in a cage complex (vide infra). Singlet oxygen, generated via energy transfer from Ru(II) in its excited state, is the reactive species that is responsible for the oxidation of the hydroxamate group to its corresponding nitroxyl radical. This was confirmed by using a specific quencher (sodium azide) and by following the kinetics of the nitroxyl radical formation in deuterated solvents. Moreover, we can turn on the electron-transfer pathway by liberating superoxide radicals and producing a strong oxidant, Ru(III), from the collision “cage” complex proposed earlier (Zhang, X.; Rodgers, M. A. J. J. Phys. Chem. 1995, 99, 12797−12803.) This was achieved using compounds with either chemical (spin traps) or enzymatic (superoxide dismutase) affinity to superoxide radicals. Thus, the rate and yield of the nitroxyl radical formation in the novel ruthenium complex can be increased by almost thirty times.

Selection for carotenogenesis in the yeast Phaffia rhodozyma by dark-generated singlet oxygen

Selection for carotenogenesis in Phaffia rhodozyma was achieved by exposure of yeast strains to dark chemical reactions that generate singlet oxygen. Incubation of a mixture of P. rhodozyma strains containing varying levels of carotenoids in hypochlorous acid or hydrogen peroxide resulted in weak selection for pigmented strains. However, the combination of hydrogen peroxide and hypochlorous acid was strongly selective for carotenogenesis and gave a monoculture of a carotenoid-hyperproducer. Exposure of the yeast to ozone for 10 to 20 min also selected for a hyperproducing strain. These selections were relieved by 1,4-diazabicyclo[2.2.2]-octane, a specific quencher of singlet oxygen or by l-ascorbic acid. Continuous growth of P. rhodozyma on agar plates in an ozone/air atmosphere for 5 d decreased astaxanthin and total carotenoid levels and increased the levels of carotenoid biosynthetic intermediates. Repeated rounds of random mutagenesis followed by ozone exposure yielded mutant strains with higher pigmentation than control cultures. Our results support the hypothesis that a primary function of carotenoids in P. rhodozyma is to protect against singlet oxygen generated in the natural environment of the yeast and that a practical method for preventing strain degeneration during industrial fermentations may be achieved by generation of singlet oxygen using simple chemical supplements or by bubbling ozone through P. rhodozyma cultures during fermentation.

Role of hypochlorous acid inTrypanosoma musculikilling by phagocytes

Trypanosoma musculi are readily killed when phagocytosed by mononuclear phagocytes but the nature of the mediators of this cytotoxicity is unclear. Among the most potent mediators are oxygen-derived species. The generation of chemiluminescence (CL) by peritoneal macrophages from 12 day T. musculi-infected mice, which phagocytose and kill parasites when opsonizing antibodies are present, was recorded in the presence of antibody-coated trypanosomes. Taurine, a specific quencher of hypochlorous acid (HOCl) inhibited CL production by peritoneal macrophages, showing that HOCl is produced during phagocytosis of T. musculi. In vitro, HOCl alone exerted a powerful trypanocidal activity which was inhibited in the presence of specific quenchers. The role of HOCl generated by phagocytes in trypanosome killing was studied using granulocytes which produce more oxygen-derived species than macrophages when stimulated. Phorbol myristate acetate-triggered granulocytes can destroy T. musculi and trypanosome killing is inhibited in the presence of taurine. These data demonstrate that HOCl produced by phagocytes can effectively destroy T. musculi.

The role of CHCl 3 as a quencher for γ and UV excited organic solutions

CHCl 3 dissolved in aromatic hydrocarbon solutions of fluorescent solutes is a specific quencher of fluorescence resulting from γ-ray or UV excited upper electronic states of the solvent, CHCl 3 shows long-range electron-scavenging and short-range contact quenching properties.