Diaminonaphthalene Research Articles

Diaminonaphthalene Boronic Acid (DANBA): New Approach for Peroxynitrite Sensing Site

AbstractSelective detection of reactive oxygen species (ROS) is vital for studying their role in brain diseases. Fluorescence probes can distinguish ONOO− species from other ROS; however, their selectivity toward ONOO− species depends on the ONOO− recognition group. Aryl‐boronic acids and esters, which are common ONOO− recognition groups, are not selective for ONOO− over H2O2. In this study, we developed a diaminonaphthalene (DAN)‐protected boronic acid as a new ONOO− recognition group that selectively reacts with ONOO− over H2O2 and other ROS. Three DAN‐protected boronic acid (DANBA)‐based fluorophores that emit fluorescence over visible to near‐infrared (NIR) regions, Cou‐BN, BVP‐BN, and HDM‐BN, and their aryl‐boronic acid‐based counterparts (Cou‐BO, BVP‐BO, and HDM‐BO), were developed. The DANBA‐based probes exhibited enhanced selectivity toward ONOO− over that of their control group, as well as universality in solution assays and in vitro experiments with PC12 cells. The NIR‐emissive HDM‐BN was optimized to delineate in vivo ONOO− levels in mouse brains with Parkinson's disease. This DAN‐protected boronic acid belongs to a new generation of recognition groups for developing ONOO− probes, and this strategy could be extended to other common hydroxyl‐containing dyes to detect ONOO− levels in complex biological systems and processes.

Diaminonaphthalene Boronic Acid (DANBA): New Approach for Peroxynitrite Sensing Site.

Selective detection of reactive oxygen species (ROS) is vital for studying their role in brain diseases. Fluorescence probes can distinguish ONOO- species from other ROS; however, their selectivity toward ONOO- species depends on the ONOO- recognition group. Aryl-boronic acids and esters, which are common ONOO- recognition groups, are not selective for ONOO- over H2O2. In this study, we developed a diaminonaphthalene (DAN)-protected boronic acid as a new ONOO- recognition group that selectively reacts with ONOO- over H2O2 and other ROS. Three DAN-protected boronic acid (DANBA)-based fluorophores that emit fluorescence over visible to near-infrared (NIR) regions, Cou-BN, BVP-BN, and HDM-BN, and their aryl-boronic acid-based counterparts (Cou-BO, BVP-BO, and HDM-BO), were developed. The DANBA-based probes exhibited enhanced selectivity toward ONOO- over that of their control group, as well as universality in solution assays and in vitro experiments with PC12 cells. The NIR-emissive HDM-BN was optimized to delineate in vivo ONOO- levels in mouse brains with Parkinson's disease. This DAN-protected boronic acid belongs to a new generation of recognition groups for developing ONOO- probes, and this strategy could be extended to other common hydroxyl-containing dyes to detect ONOO- levels in complex biological systems and processes.

Charge Polarity Control in Organic Transistors of Mixed and Segregated Complexes Based on Diaminonaphthalene and Pyrene.

Organic cocrystals of diaminonaphthalene (DAN) and diaminopyrene (DAP) with bromanil (BA) and tetracyanoquinodimethane (TCNQ) are an exemplar system for understanding the charge-transport process, where from the viewpoint of partition theory, orbital symmetry plays a crucial role in controlling the carrier charge polarity of transistors. In the mixed-stack complexes of BA and other p-quinone acceptors, a comparatively weak donor, 1,5-DAN, shows p-channel characteristics owing to the counteractive contribution of the next highest occupied molecular orbital for electron transport. This characteristic behavior occurs because the BA molecule, situated on top of the amino group, overlaps with half of the DAN molecule. By contrast, the BA and TCNQ complexes of a stronger donor, 1,6-DAP, exhibit n-channel transport due to the cooperative path and orthogonal orbitals. Similarly, TCNQ complexes of variously substituted DAN show n-channel transport, where the TCNQ molecules are located on top of the DAN molecules. However, when the carbon electrodes of (1,5-DAN)(BA) are replaced by silver, electron transport appears due to the competitive effect of the Schottky barriers. In a highly conducting segregated complex of (1,6-DAP)(TCNQ), ambipolar transistor characteristics are observed without subtracting the bulk current by using carefully prepared thin-film transistors.

Green-to-blue fluorescence sensor on pesticide starane based on bis-tetraphenylimidazole

The widespread use of pesticide starane calls for the simple, rapid and on-site detection to mitigate its negative impacts on human health and the environment. In this work, a diamino naphthalene Schiff-base bridging bis-tetraphenylimidazole (Bis-TPI, red powder, λabs = 360 nm) prepared by Schiff-base condensation is developed as an effective fluorescence sensor on pesticide starane with very low detection limitation. Bis-TPI in DMSO-H2O with 95% of H2O showed weak green fluorescence but strong blue fluorescence when bound to starane. This binding behavior for starane exhibited good sensing selectivity among various ions and pesticides. The detection limitation was as low as 0.015 μM, which is the smallest value of the fluorescence sensor for starane. The 1:1 binding mechanism is clarified as that starane is bound in the opening cavity of Bis-TPI based on hydrogen bond, π-π stacking and hydrophobic action. Bis-TPI in DMSO-H2O with 95% of H2O is successfully employed to detect starane in various samples including test paper, fresh leaves and real water samples, highlighting its potential as a valuable tool for rapid, simple and on-site examination of starane with high selectivity and sensitivity in agriculture and daily life.

Rapid determination of malondialdehyde in serum samples using a porphyrin-functionalized magnetic graphene oxide electrochemical sensor

An electrochemical sensor based on a screen-printed carbon electrode (SPCE) modified with porphyrin-functionalized magnetic graphene oxide (TCPP-MGO) was developed for the sensitive and selective determination of malondialdehyde (MDA), an important biomarker of oxidative damage, in serum samples. The coupling of TCPP with MGO allows the exploitation of the magnetic properties of the material for separation, preconcentration, and manipulation of analyte, which is selectively captured onto the TCPP-MGO surface. The electron-transfer capability in the SPCE was improved through derivatization of MDA with diaminonaphthalene (DAN) (MDA-DAN). TCPP-MGO-SPCEs have been employed to monitor the differential pulse voltammetry (DVP) levels of the whole material, which is related to the amount of the captured analyte. Under optimum conditions, the nanocomposite-based sensing system has proved to be suitable for the monitoring of MDA, presenting a wide linear range (0.01–100 µM) with a correlation coefficient of 0.9996. The practical limit of quantification (P-LOQ) of the analyte was 0.010 µM, and the relative standard deviation (RSD) was 6.87% for 30 µM MDA concentration. Finally, the developed electrochemical sensor has demonstrated to be adequate for bioanalytical applications, presenting an excellent analytical performance for the routine monitoring of MDA in serum samples.Graphical abstract

Unexpected formation of 2-methyl-1H-naphtho [2, 3-d] imidazole via decarboxylation governed mechanistic pathway

Present work is the outcome of the synthetic strategy for the naphthalene analogue of benzimidazole dimer, 2-methyl-1H-naphtho [2, 3-d] imidazole. It was found that 1H-naphtho [2, 3-d] imidazol-2-yl) methane (2b') was formed instead of respective dimer. Herein, we have reported two synthetic ways for 2b', first conventional refluxing method with 70 % yield and second by using synthesis reactor with 75 % yield. Both the way of synthesis involves the reaction of 2,3- diamino naphthalene and diethyl malonate in acidic medium. This example belongs to C-2(sp2)-C-1(sp3) type decarboxylation. To the best of our knowledge, it is the first-time synthesis of the 2b‘ has been reported via decarboxylation pathway along with crystal structure and DFT studies. Most probable mechanisms for both the compounds have been proposed based on the energy profile diagram and thermodynamic data obtained by DFT calculations [B3LYP/6-311++G (d,p)] in gas phase. Absorption responses showed potential of the naphthaimidazole based molecule 2b‘ as a pH and metal ion sensor of various hazardous metals such as As3+, Cr3+, Hg2+,Cd2+, Pb2+.

Graphene Bioelectronic Nose for the Detection of Odorants with Human Olfactory Receptor 2AG1

A real-time sensor for the detection of amyl butyrate (AB) utilising human olfactory receptor 2AG1 (OR2AG1), a G-protein coupled receptor (GPCR) consisting of seven transmembrane domains, immobilized onto a graphene resistor is demonstrated. Using CVD graphene as the sensor platform, allows greater potential for more sensitive detection than similar sensors based on carbon nanotubes, gold or graphene oxide platforms. A specific graphene resistor sensor was fabricated and modified via non-covalent π–π stacking of 1,5 diaminonaphthalene (DAN) onto the graphene channel, and subsequent anchoring of the OR2AG1 receptor to the DAN molecule using glutaraldehyde coupling. Binding between the target odorant, amyl butyrate, and the OR2AG1 receptor protein generated a change in resistance of the graphene resistor sensor. The functionalized graphene resistor sensors exhibited a linear sensor response between 0.1–500 pM and high selectively towards amyl butyrate, with a sensitivity as low as 500 fM, whilst control measurements using non-specific esters, produced a negligible sensor response. The approach described here provides an alternative sensing platform that can be used in bioelectronic nose applications.

Role of diaminonaphthalene based polymers as sensors in detection of biomolecules: A review

The recent advancements in the synthetic polymer chemistry have resulted in synthesis of potentially distinct conducting polymers that have found a wide range of applications from industry to biology. Among various conducting polymers, poly (diaminonaphthalene) (PDAN) and its derivatives have emerged as promising materials in constructing bio/chemical sensors and shown potential in quantitative and qualitative assays of a variety of bioactive molecules. It is, however, surprising that in spite of having unusual physicochemical properties of this typical polymer and its monomers, no comprehensive information about their sensing properties are available in the literature either as review articles or monographs. The present review article highlights a broad scenario of diaminonaphthalene (DAN) and its polymer-based nanostructured bio/chemical sensors providing insights into their functioning, structural composition, fabrication through various polymerization routes, and eventual applications in sensing different type of biochemically active molecules. Moreover, PDAN based Dual Gate Organic Field Effect Transistor has been modeled and substantially reviewed for their applications in sensing the biomolecules. The underlying present challenges in the area of PDAN based biochemical sensors and their future prospects have been critically examined and several issues to be addressed have also been raised.

Diazaboryl-naphthyl-ketone: A New Scaffold with Bright Fluorescence, Aggregation-Induced Emission, and Application in the Quantitation of Trace Boronic Acids in Drug Intermediates.

This study describes the synthesis, structure, and photophysical properties of a new luminescent polyaromatic boronic acid scaffold, diazaboryl-naphthyl-ketones (DNKs). These stable compounds display extremely bright fluorescence, aggregation-induced emission, positive solvatochromism, and solid-state fluorescence. DFT calculations and X-ray crystallographic study revealed notable electronic and structural differences between these compounds and the parent diaminonaphthalene (DAN) adducts. Acylation of the DAN system causes a localization of both HOMO and LUMO onto the DNK unit, which validates the negligible influence of the B-aryl substituent. The LUMO energy is lowered, and its shape significantly altered. Photophysical data in solution and the solid state revealed blue-shifted, narrowed, and intense emissions for DNKs (up to 89 % quantum yield). The potential utility of the fluorogenic DNK system was demonstrated with a proof-of-concept for the determination of trace boronic acid contaminants in solid samples, down to one-ppm level, using HPLC with fluorescence detection. This method could be useful in pharmaceutical development for the quantitation of difficult-to-detect and potentially mutagenic residual boronic acid from late cross-coupling reactions in drug syntheses.

A facile approach for constructing nitrogen-doped carbon layers over carbon nanotube surface for oxygen reduction reaction

Fabricating nitrogen-doped carbon layers over the conductive substrate is a cost-effective and efficient approach to develop practical oxygen reduction reaction (ORR) catalyst. In the current work, relying on the commercially available carbon nanotube (CNT), nitrogen-doped carbon layers over CNT is constructed by annealing the in situ formed complex over the CNT surface derived from iron ion inducing diaminonaphthalene (DAN) polymerization and DAN self-polymerization. Physical and electrochemical characterizations are carefully conducted to comparatively analyze the structure and activity relationship. The significance of iron in constructing nitrogen-doped carbon layers and tuning active sites of N types over multiwall carbon nanotube for ORR is demonstrated by X-ray photoelectron spectroscopy and Raman scattering spectrum. The excellent performance of nitrogen-doped carbon layers over CNT (catalyzed by iron) towards ORR is displayed by rotating ring-disk electrode. Specifically, the onset potential, half-wave potential, and limiting current density are 0.961 V, 0.831 V, and 5.20 mA cm−2 respectively, very close to the state-of-the-art commercial Pt/C catalyst. Both high surface area and efficient N active sites should be considered in the nitrogen-doped carbon materials design and fabrication for ORR. Considering the large-scale availability, it has significant value in fuel cells commercial applications.

Abstract 4497: Delineating the effects of different levels of nitric oxide produced by "M1" stimulated macrophages on tumor rejection and response to therapy

Abstract Nitric Oxide (NO) was historically known to be immunosuppressive in cancers by inhibiting T-cell function and endothelial activation. This is relevant however only in the aberrant, dysfunctional tumor vasculature. Recently, local low dose irradiation was found to cause the differentiation of NOS2+ macrophages in the tumor microenvironment, that then normalized the vasculature and allowed T-cell infiltration, subsequent tumor rejection and prolonged survival in mouse models of pancreatic cancer (Klug et al., 2013). It was later shown that high doses of NO inhibited normal vascularization while at low doses, NO induced the expression of endothelial cell adhesion molecules and favored T-cell infiltration (Sektioglu et al., 2016). Previously, we found that murine macrophages can be activated by different cytokines/LPS to produce different levels of NO in the extracellular space (Espey et al., 2000). In the current study, we used these cytokine/LPS combinations to stimulate macrophages to produce distinct NO levels and delineate their intracellular effects. The levels of NO in bulk solution in vitro was determined using various methods for measuring NOS2 protein and various products of the NO/O2 reaction using Griess assay and nitrosation of fluorescent dyes like diamino fluorescein (DAF) and diamino naphthalene (DAN). At the single cell level, microscopy and flowcytometry were employed to assess NOS2 protein levels. Status of oxidative phosphorylation (OxPhos) and glycolytic commitment in the stimulated macrophages was studied using the Seahorse bioanalyzer. The high NOS2 induction by IFNγ/LPS followed by IFNγ/TNFα and then IFNγ/IL1β as seen in the bulk environment was spatially and temporally regulated with IFNγ/LPS inducing NOS2 in as early as 4h earlier and in more number of cells while IFNγ/TNFα starts inducing NOS2 at 8h, in fewer cells and IFNγ/IL1β only induces very low NOS2 although in all the cells. These fluxes could be directly correlated to changes in bioenergetics with IFNγ/IL1β activating OxPhos above resting macrophages while IFNγ/LPS causes glycolytic commitment. The NO levels also regulate expression of cell adhesion molecules on endothelial cells. The NOS2 induction is spatially and temporally regulated and NO fluxes were also cell type and species specific although the trend of IFNγ/LPS > IFNγ/TNFα > IFNγ/IL1β is maintained across the macrophage types analyzed. We find that these different levels have distinct effects on macrophage metabolism and endothelial activation. Hence, we now have insights into which NO flux can help improve response to cancer immunotherapy versus cause immunosuppression. Citation Format: Veena Somasundaram, Debashree Basudhar, Erika M. Palmieri, Robert Y. Cheng, Lisa A. Ridnour, Daniel W. McVicar, David A. Wink. Delineating the effects of different levels of nitric oxide produced by "M1" stimulated macrophages on tumor rejection and response to therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4497.

Nitrate and nitrite exposure affect cognitive behavior and oxygen consumption during exercise in zebrafish

Humans concentrate nitrate from dietary or endogenous sources in the salivary glands, which is then reduced to nitrite, swallowed, and absorbed. Circulating nitrite acts as a reservoir for nitric oxide (NO) with its reduction to NO potentiated in acidic or hypoxic areas, such as contracting skeletal muscle. NO is an important signaling molecule with a short half‐life that regulates cardiovascular function, cellular energetics, and neurotransmission among other things. In humans, consumption of supplemental nitrate reduces blood pressure and decreases the oxygen cost of exercise, but we do not have a complete understanding of how dietary nitrate or nitrite is metabolized particularly in the presence of exercise. We used a stable isotope‐assisted metabolomics approach to assess nitrate and nitrite metabolism with and without exercise, and tested the hypothesis that nitrate and nitrite exposure reduces the cost of exercise and improves cognitive function in a zebrafish model.Adult zebrafish were exposed to either sodium nitrate (606.9 mg/L), sodium nitrite (19.5 mg/L), or control water for 21 days (n=60–66). A subset of the fish were switched to 100% 15N‐nitrite or 15N‐nitrate for the final 3 days of the exposure. Tissue nitrite and nitrate were quantified using diaminonaphthalene (DAN) derivatization and subsequently analyzed on a 3200 ABSciex QTRAP. Nitrite and nitrate exposure increased tissue nitrite (230% and 340%, respectively) and tissue nitrate (150% and 250%, respectively), and significant increases in nitrate and nitrite in blood were also observed. Nitrate exposure significantly decreased oxygen consumption during exercise in the AutoResp exercise assay. Nitrite treatment increased oxygen consumption with exercise but pathological examination indicated nitrite exposure caused mild gill damage. Metabolomics showed that up to 90% of the tissue nitrite and nitrate can be derived from exogenous sources. The data supports existing data that a feedback mechanism that inhibits endogenous NO production when high levels of nitrite or nitrate are consumed. Nitrite was depleted during exercise in all treatment groups, indicating potential increased utilization of nitrite as a substrate for NO production in hypoxia.In a free swim test nitrate and nitrite treatment significantly increased the duration of time spent in the bottom of the tank which is a possible indicator of anxiety. Nitrate treated fish also had a significant decline in movement following a startle but this was not detected in nitrite treated fish. In a negative conditioning‐learning assay nitrate treatment significantly impaired decision making time, and caused a 3‐fold increase in the period of time the fish experienced a mild shock. Nitrite treated caused a 2‐fold increase in the period of shock at the beginning of the assay, but the fish were able to learn with time. Taken together the behavioral assays demonstrate that both nitrate and nitrate treatments altered cognitive function in zebrafish and metabolomics on brains is being undertaken to understand the mechanisms contributing to these phenotypes.Support or Funding InformationOregon Agricultural Experiment Station, Endowment for the Celia Strickland and G. Kenneth Austin III Endowed Professor of Public Health

Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) enabled analysis of inter-polymer phases formation in poly (diaminonaphthalene) doped conducting poly (vinyl alcohol) films

In the present work, polymerization of monomer diaminonaphthalene (DAN) was carried out inside the poly (vinyl alcohol) (PVA) film that resulted in the formation of multi inter-phases of the two polymers. The presence of functional groups of the PVA and PDAN in the blend film was confirmed by the FTIR spectra. The formation of multi-interphases was further confirmed by the ToF-SIMS technique. The positive ion beam spectra of the prepared polymer matrix provided insights about the morphology of the top most layer and the interphases layers developed within the polymer blend film. The formation of multi inter-phases offered potential in designing bulk hetero-junction semiconductor structures.

Atomic force microscopy enabled roughness analysis of nanostructured poly (diaminonaphthalene) doped poly (vinyl alcohol) conducting polymer thin films

The Atomic Force Microscopy (AFM) helps in evaluating parameters like amplitude or height parameters, functional or statistical parameters and spatial parameters which describe the surface topography or the roughness. In this paper, we have evaluated the roughness parameters for the native poly (vinyl alcohol) (PVA), monomer diaminonaphthalene (DAN) doped PVA, and poly (diaminonaphthalene) (PDAN) doped PVA films prepared in different solvents. In addition, distribution of heights, skewness and Kurtosis moments which describe surface asymmetry and flatness properties of a film were also determined. At the same time line profiles, 3D and 2D images of the surface structures at different scanning areas i.e. 5×5μm2 and 10×10μm2 were also investigated. From the roughness analysis and the surface skewness and coefficient of Kurtosis parameters, it was concluded that for PVA film the surface contains more peaks than valleys and the PDAN doped PVA film has more valleys than peaks. It was also found that the PDAN doped PVA film with acetonitrile solvent was used for substrate in electronics applications because the film gives less fractal morphology. Thus, the AFM analysis with different parameters suggested that the PDAN doped PVA films are smooth at the sub-nanometer scale.

Synthesis of tin oxide activated by DAN grafting and Mo nanoparticle insertion for optoelectronic properties improvement

Tin oxide (SnO2) was synthesized via a co-precipitation method and activated by 1,5 diaminonaphthalene (DAN) grafting and molybdenum nanoparticle (Mo-NPs) incorporation for the first time as a new material.

Flower-like Palladium Nanoclusters Decorated Graphene Electrodes for Ultrasensitive and Flexible Hydrogen Gas Sensing.

Flower-like palladium nanoclusters (FPNCs) are electrodeposited onto graphene electrode that are prepared by chemical vapor deposition (CVD). The CVD graphene layer is transferred onto a poly(ethylene naphthalate) (PEN) film to provide a mechanical stability and flexibility. The surface of the CVD graphene is functionalized with diaminonaphthalene (DAN) to form flower shapes. Palladium nanoparticles act as templates to mediate the formation of FPNCs, which increase in size with reaction time. The population of FPNCs can be controlled by adjusting the DAN concentration as functionalization solution. These FPNCs_CG electrodes are sensitive to hydrogen gas at room temperature. The sensitivity and response time as a function of the FPNCs population are investigated, resulted in improved performance with increasing population. Furthermore, the minimum detectable level (MDL) of hydrogen is 0.1 ppm, which is at least 2 orders of magnitude lower than that of chemical sensors based on other Pd-based hybrid materials.

Improved actuated strain of dielectric elastomer through disruption of hydrogen bonds of thermoplastic polyurethane by adding diaminonaphthalene

We used a novel and simple approach to increase the actuated strain at low electric field of thermoplastic polyurethane (TPU) through the disruption of the hydrogen bonds of TPU by adding diaminonaphthalene (DAN) into the matrix. DAN as proton donors disrupted the original N–H/C=O hydrogen bonds between the TPU chains, improving the polarizability of the chains, thus increasing the dielectric constant of TPU. Meanwhile, DAN greatly decreased the elastic modulus of TPU by disrupting the hydrogen bonds of TPU. The simultaneous increase in dielectric constant and decrease in elastic modulus resulted in a 330% increase in electromechanical sensitivity at 103 Hz and a 500% increase in actuated strain at the low electric field of 20 V μm−1, facilitating the application of dielectric elastomers (DEs) in the biological and medical fields, where a low electric field is required. In addition, our DAN/TPU DE exhibited good mechanical strength.

Decolorization of textile azo dye and Congo red by an isolated strain of the dissimilatory manganese-reducing bacterium Shewanella xiamenensis BC01

Shewanella xiamenensis BC01 (SXM) was isolated from sediment collected off Xiamen, China and was identified based on the phylogenetic tree of 16S rRNA sequences and the gyrB gene. This strain showed high activity in the decolorization of textile azo dyes, especially methyl orange, reactive red 198, and recalcitrant dye Congo red, decolorizing at rates of 96.2, 93.0, and 87.5%, respectively. SXM had the best performance for the specific decolorization rate (SDR) of azo dyes compared to Proteus hauseri ZMd44 and Aeromonas hydrophila NIU01 strains and had an SDR similar to Shewanella oneidensis MR-1 in Congo red decolorization. Luria-Bertani medium was the optimal culture medium for SXM, as it reached a density of 4.69 g-DCW L(-1) at 16 h. A mediator (manganese) significantly enhanced the biodegradation and flocculation of Congo red. Further analysis with UV-VIS, Fourier Transform Infrared spectroscopy, and Gas chromatography-mass spectrometry demonstrated that Congo red was cleaved at the azo bond, producing 4,4'-diamino-1,1'-biphenyl and 1,2'-diamino naphthalene 4-sulfonic acid. Finally, SEM results revealed that nanowires exist between the bacteria, indicating that SXM degradation of the azo dyes was coupled with electron transfer through the nanowires. The purpose of this work is to explore the utilization of a novel, dissimilatory manganese-reducing bacterium in the treatment of wastewater containing azo dyes.

Focusing of nitric oxide mediated nitrosation and oxidative nitrosylation as a consequence of reaction with superoxide.

The impact of nitric oxide (NO) synthesis on different biological cascades can rapidly change dependent on the rate of NO formation and composition of the surrounding milieu. With this perspective, we used diaminonaphthalene (DAN) and diaminofluorescein (DAF) to examine the nitrosative chemistry derived from NO and superoxide (O2-) simultaneously generated at nanomolar to low micromolar per minute rates by spermine/NO decomposition and xanthine oxidase-catalyzed oxidation of hypoxanthine, respectively. Fluorescent triazole product formation from DAN and DAF increased as the ratio of O2- to NO approached equimolar, then decreased precipitously as O2- exceeded NO. This pattern was also evident in DAF-loaded MCF-7 carcinoma cells and when stimulated macrophages were used as the NO source. Cyclic voltammetry analysis and inhibition studies by using the N2O3 scavenger azide indicated that DAN- and DAF-triazole could be derived from both oxidative nitrosylation (e.g., DAF radical + NO) and nitrosation (NO+ addition). The latter mechanism predominated with higher rates of NO formation relative to O2-. The effects of oxymyoglobin, superoxide dismutase, and carbon dioxide were examined as potential modulators of reactant availability for the O2- + NO pathway in vivo. The findings suggest that the outcome of NO biosynthesis in a scavenger milieu can be focused by O2- toward formation of NO adducts on nucleophilic residues (e.g., amines, thiols, hydroxyl) through convergent mechanisms involving the intermediacy of nitrogen dioxide. These modifications may be favored in microenvironments where the rate of O2- production is temporally and spatially contemporaneous with nitric oxide synthase activity, but not in excess of NO generation.

Selenium in soil and endemic diseases in China.

Selenium is an essential element for humans, animals and some species of microorganisms. The biological function of selenium shows dual characteristics. The selenium content range between toxic and deficient concentration is very narrow. The present paper discusses the geographical distribution of two forms (total and water-soluble) of selenium in topsoil (plough layer for cultivated soils, eluvial horizon for natural soils) and evaluates its relationship with some human health problems in China. Topsoil samples, 354 in total, including 156 natural and 198 cultivated soils of 21 main soil types were collected. The total Se concentration in soil samples was determined with DAN (di-aminonaphthalene)-fluorescence spectrophotometer method. Soil water-soluble Se concentration was determined with the same method after extraction with water (water/soil = 5:1). The results showed that the geometric and arithmetic means of total Se concentration in soil, for all samples, were 0.173 mg/kg and 0.239 mg/kg, respectively, with the lowest value being 0.022 mg/kg and the highest being 3.806 mg/kg. For the cultivated soil, the geometric mean of total Se was 0.188 mg/kg, its arithmetic mean was 0.269 mg/kg and higher than those in the natural soil, 0.154 mg/kg and 0.206 mg/kg, respectively. The geometric and arithmetic means of water-soluble Se in soil for all the samples were 4.0 and 6.4 microg/kg, the lowest 0.6 microg/kg and the highest value being 109.4 microg/kg. For the cultivated soils, the average concentration of water-soluble Se was 4.3 microg/kg, similar to that of natural soil, they are and 4.4 microg/kg by geometric mean. Two sequences of the soil types, arranged separately in the concentration of total Se and water-soluble Se, are different and this demonstrates that the proportions of the two forms of selenium existing in various soils are different. The percentages of water-soluble Se to total Se in different types of soils varied from 1.07 to 6.69%. However, generally the laterite and other subtropic soil still have relatively high absolute water-soluble Se contents because of their higher total Se contents. A very significant correlation between total Se and water-soluble Se has been found in cultivated soil with a correlation coefficient of 0.58 (P < 0.01). The relationships between soil Se and human endemic diseases Keshan disease, Kashin-Back diseases and selenosis have been discussed. The reference criteria for evaluating Se deficiency and Se excess in soil were suggested.