Free Nitrogen Research Articles

Relationships between fresh weight, dry weight, ash free dry weight, carbon and nitrogen content for selected vertebrates

Top predators are relevant indicators of the ecological status of a system and can have a high impact on food webs. But top predators are difficult to include in network analyses because their biomass in ash free dry weight or carbon content is missing. Regression equations were determined for the relationships between fresh weight and dry weight, ash free dry weight, carbon and nitrogen contents respectively for six of the most abundant bird species in the Wadden Sea (Calidris canutus, Limosa lapponica, Haematopus ostralegus, Chroicocephalus ridibundus, Larus canus, Anas penelope) and harbor seals (Phoca vitulina). The relationships for all species were interpreted as linear through the origin. Carbon content vs. fresh weight ratios for birds ranged from 0.16±0.01 to 0.22±0.02. Carbon content vs. fresh weight ratio was 0.17±0.02 on average for harbor seals. This work highlights that the biomass of top predators was often over- or underestimated in previous studies. The determined conversion factors will be useful for future studies to generate more realistic food web models.

Highly Efficient Graphene Supports for Fuel Cell Electrocatalysts

Graphene nanomaterials are increasingly important with their distinct properties such as high electrical conductivity, high contact surface area and enormous stability. Therefore, graphene has been used as promising catalyst support in energy conversion and storage systems. In order to achieve high catalytic activity a specifically guided growth of catalyst on graphene support surface with delicate controllability is highly preferred. Therefore, we modify graphene surface in two different ways such as graphene functionalization with various active functional groups and fabrication of nanocomposites with intrinsically conducting polymers e.g. polypyrrole (PPy). We have successfully modified graphene oxide by the functionalization with free amine groups (GO-NH2), RGD peptide (GO-RGD) and Nitrogen doping (N-GO). Platinum (Pt) catalyst nanoparticles have been deposited on these functionalized GO (f-GO) using ethylene glycol modified method. The dispersion of Pt deposited F-GO has been enhanced and stable optimized dispersions in organic solvents were obtained. The cyclic voltametry (CV) results showed a high electrochemical surface area (ECSA) of 147 m2/g for GO-RGD compared to Pt/carbon black (Pt/C, 80 m2/gPt) and Pt/GO (99 m2/gPt). On the other hand, we also fabricated GO/PPy/CB (carbon black) hybrid nanocomposites as catalyst support and deposited Pt catalyst nanoparticles. The CV results showed a high ECSA of 153 m2/gPt. These modified graphene nanomaterials including Pt/f-GO and hybrid composites have been successfully used in proton exchange membrane fuel cell (PEMFC) electrodes. The Pt nanoparticles distribution on various modified graphene surfaces, which may significantly influence their properties such as electrical conductivity, electrocatalytic activity when they used as catalyst support and fuel cell performance will be discussed more in details.

Etiologies of sperm oxidative stress

Sperm is particularly susceptible to reactive oxygen species (ROS) during critical phases of spermiogenesis. However, the level of seminal ROS is restricted by seminal antioxidants which have beneficial effects on sperm parameters and developmental potentials. Mitochondria and sperm plasma membrane are two major sites of ROS generation in sperm cells. Besides, leukocytes including polymer phonuclear (PMN) leukocytes and macrophages produce broad category of molecules including oxygen free radicals, non-radical species and reactive nitrogen species. Physiological role of ROS increase the intracellular cAMP which then activate protein kinase in male reproductive system. This indicates that spermatozoa need small amounts of ROS to acquire the ability of nuclear maturation regulation and condensation to fertilize the oocyte. There is a long list of intrinsic and extrinsic factors which can induce oxidative stress to interact with lipids, proteins and DNA molecules. As a result, we have lipid peroxidation, DNA fragmentation, axonemal damage, denaturation of the enzymes, over generation of superoxide in the mitochondria, lower antioxidant activity and finally abnormal spermatogenesis. If oxidative stress is considered as one of the main cause of DNA damage in the germ cells, then there should be good reason for antioxidant therapy in these conditions.

Effect of Filler Wire Composition on Microstructure and Pitting Corrosion of Nickel Free High Nitrogen Stainless Steel GTA Welds

Nitrogen alloyed austenitic stainless steels are recently developed and are finding applications in defence because of improved mechanical properties and corrosion resistance. Welding is the main fabrication technique to join the structural components. During welding, it may result in porosity, solidification cracking in weld zone, liquation cracking in heat affected zone and inferior properties compared to base metal. Selection of filler wire plays a major role to obtain a sound weld and to have a better mechanical and corrosion resistance. In the present work, gas tungsten arc welding of 5 mm thick nickel free high nitrogen stainless steels were carried out. As no suitable matching filler wires have been developed, commercially available high strength fillers of precipitation hardenable (PH) 13-8Mo filler and nickel based (MDN 250) 18Ni filler were used for welding high nitrogen stainless steel. Microstructural studies were carried out using optical microscopy and field emission scanning electron microscopy (FESEM). Electron back scattered diffraction (EBSD) technique was used to determine the grain size, phase analysis and orientation mapping. Hardness values were recorded using Vickers hardness tester. Results of the present investigation established that the weld zone/fusion zone was observed to have delta-ferrite in the austenite matrix for both the welds. Welds made with (MDN 250) 18Ni filler had an unmixed zone adjacent to the weld zone near fusion boundary. Welds made with (PH) 13-8Mo filler had high hardness which might be attributed to relatively finer grains in the weld zone. Improved pitting corrosion resistance for welds made with (PH) 13-8Mo filler might be attributed to the composition of the filler wire. The presence of chromium and molybdenum helped in enhancing the stable passive film when compared to that of welds made with MDN 250 filler.

Uptake of free, calcium-bound and liposomal encapsulated nitrogen containing bisphosphonates by breast cancer cells

Purpose: We have examined the uptake routes by which breast cancer cells internalize different formulations of nitrogen containing bisphosphonates (N-BPs).Methods: Cell viability was assessed with the tetrazolium colorimetric test (MTT assay) after treatment with different N-BP formulations in the presence or absence of inhibitors for different endocytosis mechanisms. Intracellular formation of isopentenyl pyrophosphate (IPP) and triphosphoric acid 1-adenosin-5′-yl ester 3-(3-methylbut-3-enyl) ester (ApppI), were quantified with mass spectrometry (ES-LTQ-MS) as surrogate markers for N-BP efficacy. Direct quantification intracellular [14C]-labeled zoledronic acid was done with liquid scintillation counting.Results: The main uptake route for all the different formulations of nitrogen containing bisphosphonates was shown to be dynamin dependent endocytosis, which was significantly enhanced with calcium. This uptake mechanism was mostly caveolin and clathrin independent in MCF7 cells, but more clathrin dependent in T47D cells. Liposome encapsulation of the drug shifted the uptake mechanism to be more dependent on caveolin in both the cell lines. The cytotoxicity of N-BPs and the concentrations of formed intracellular ApppI and IPP were significantly increased by calcium chelation and liposome encapsulation, the latter being the most potent formulation.Conclusion: Nitrogen containing bisphosphonates require active endocytosis for cellular uptake and in the breast cancer cells the mechanism is uniformly dynamin dependent for all the formulations tested. This differs e.g. from the previous observations on macrophages, which mostly utilize macropinocytosis. Liposomal formulation was found to prolong the duration of the drug effect in cells.

Enhanced visible light photocatalytic activities of template free mesoporous nitrogen doped reduced graphene oxide/titania composite catalysts

We report a new photocatalytic material to address the twin issues namely recombination of electron/hole pairs and visible light inactivity of the titania based photocatalysts. A template free hydrothermal method was adapted to synthesize mesoporous nitrogen doped reduced graphene oxide/titania composite catalysts (N-[x% rGO-TiO2] where x=2.5, 5, 7.5 and 10%). The detailed physicochemical studies of the catalysts were done and correlated with their photocatalytic activities. Simultaneous nitrogen doping on both reduced graphene oxide and titania was confirmed by X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the synthesized composite catalysts were evaluated towards the photodegradation of organic dyes namely methylene blue and congo red under visible light irradiation. Among them, the composite N-[5% rGO/TiO2] showed the highest photocatalytic activity. Doping of nitrogen makes graphene a better charge transporter whereas nitrogen in TiO2 lattice makes it visible light active (red shift).

Consecutive introduction of Ag(i)to an anionic homoleptic Co(iii) complex: variable Ag(i) coordination mode

Although the pyridine-2,6-diamide ligand is widely reported, coordination chemistry of the analogous pyrazine-2,6-diamide ligand has not been reported to date. To study the complexation behavior, we have synthesized N,N′-dibenzylpyrazine-2,6-dicarboxamide and the heterometallic complexes were in a stepwise manner. After dimerisation with Co(III) complexation, two ring nitrogen atoms are freely available. These two free pyrazine nitrogen atoms were studied for their coordination with Ag(I), resulting in three heterometallic complexes, C40H34AgCoN8O5, C42H38Ag3CoN10O11 and C42H53AgCoN9O13. The mode of coordination could be controlled by varying the metal to ligand ratio and varying the counter anion. Moreover, we found conditions that make the ligand to either coordinate or not coordinate to Ag+. Some of these complexes also display the rare organometallic (C–Ag) bond.

The effect of inoculation with Azotobacter chroococcum on microorganisms in rhizosphere and sugar beet yield in organic farming

The effect on sugar beet yield parameters and microbiological soil status was studied using two techniques of sugar beet inoculation with strains of Azotobacter chroococcum. Cultivar ?Drena? was used in the study, and field trial was set under the conditions of organic farming system in Backi Petrovac. A mixture of three strains of Azotobacter chroococcum was used as microbial fertilizer. Inoculation was performed by: (A) incorporation of strains into soil before sowing; and (B) repeated incorporation of strains into soil two weeks after sowing. PGP characterization of the strains confirmed the ability of producing indole-3-acetic acid (IAA) from 12.63 ?g ml-1 to 14.95 ?g ml-1, nitrogen fixation, and P-solubilization. Positive effects on the number of azotobacter and free nitrogen fixers in rhizosphere were obtained by inoculation, as well as positive effects on the tested sugar beet yield parameters. The largest increase in root yield, yield of crystal sugar, and yield of polarised sugar compared with the control was obtained by repeated soil inoculation, ranging from 22 to 23%.

The Role of Oxidative Stress and Antioxidants in Liver Diseases.

A complex antioxidant system has been developed in mammals to relieve oxidative stress. However, excessive reactive species derived from oxygen and nitrogen may still lead to oxidative damage to tissue and organs. Oxidative stress has been considered as a conjoint pathological mechanism, and it contributes to initiation and progression of liver injury. A lot of risk factors, including alcohol, drugs, environmental pollutants and irradiation, may induce oxidative stress in liver, which in turn results in severe liver diseases, such as alcoholic liver disease and non-alcoholic steatohepatitis. Application of antioxidants signifies a rational curative strategy to prevent and cure liver diseases involving oxidative stress. Although conclusions drawn from clinical studies remain uncertain, animal studies have revealed the promising in vivo therapeutic effect of antioxidants on liver diseases. Natural antioxidants contained in edible or medicinal plants often possess strong antioxidant and free radical scavenging abilities as well as anti-inflammatory action, which are also supposed to be the basis of other bioactivities and health benefits. In this review, PubMed was extensively searched for literature research. The keywords for searching oxidative stress were free radicals, reactive oxygen, nitrogen species, anti-oxidative therapy, Chinese medicines, natural products, antioxidants and liver diseases. The literature, including ours, with studies on oxidative stress and anti-oxidative therapy in liver diseases were the focus. Various factors that cause oxidative stress in liver and effects of antioxidants in the prevention and treatment of liver diseases were summarized, questioned, and discussed.

Enhancing anaerobic digestion of high-pressure extruded food waste by inoculum optimization

The inoculation for extruded food waste anaerobic digestion (AD) was optimized to improve methane (CH4) yield. The inoculum of acclimated anaerobic sludge resulted in high biodegradability, producing CH4 yields from 580 mLCH4 g−1·VSadded to 605 mLCH4 g−1·VSadded, with corresponding BDCH4 ranging from 90% to 94%. We also investigated inoculum to substrate ratios (ISRs). With regards to digested slurry as inoculum, we found that a decrease in ISR improved CH4 yield, while a lower ISR prolonged the lag time of the initial AD stage due to lipid inhibition caused by excessive food waste. These results demonstrate that minimal inocula are required to start the AD system for high-pressure extruded food waste because it is easily biodegraded. High ammonia concentration had a negative effect on CH4 production (i.e., when free ammonia nitrogen [FAN] increased from 20 to 30 mg L−1 to 120–140 mg L−1, the CH4 yield decreased by 25%), suggesting that FAN was a significant inhibitor in CH4 yield reduction. In terms of CH4 yield and lag time of the AD process, the optimal inoculation of digested slurry for the extruded food waste had an ISR of 0.33 with CH4 yield of 505 mLCH4 g−1VSadded, which was 20% higher than what was found for higher ISR controls of 2, 1 and 0.5.

Sulfonamide and Tertiary Amine as Nucleophiles in Pd(II)-Catalyzed Diamination of Alkynes: Synthesis of Tetracyclic Indolobenzothiazine S,S-Dioxides.

Pd(II)-catalyzed oxidative double cyclization of the 1,2-diarylethynes bearing an N-methyl-N-(2-methoxycarbonyl)ethylamino and an aminosulfonyl group afforded indolobenzothiazine S,S-dioxides in good to excellent yields. The 2-(methoxycarbonyl)ethyl group attached to the indolyl nitrogen is readily removed under basic conditions (DBU, DMF, 120 °C) to provide the corresponding tetracycles with a free indolyl nitrogen in excellent yields.

Microbial population dynamics in response to increasing loadings of pre-hydrolyzed pig manure in an expanded granular sludge bed

In recent years, pig manure (PM) has been regarded as a valuable substrate for energy and resource recovery via bioprocesses such as anaerobic digestion (AD), however, the efficiency of digesting raw PM is limited by the presence of refractory compounds. In this study, we applied a series of pretreatment on raw PM, consisting of subsequent thermochemical pretreatment, enzymatic hydrolysis, tyndallization and filtration. The liquid PM hydrolysates were fed to an expanded granular sludge bed (EGSB) for the production of biogas. The general performance and population dynamics of the EGSB reactor were assessed during an extended operational period of 339 days. An efficient and stable digestion process was achieved under high organic loading rates (OLRs) up to 21 kg-COD/(m3·d), agreeing with a sludge loading rate of 0.75 kg-COD/(kg-VSS·d), 1600 mg-NH4+-N/L and 17 mg/L of free ammonia nitrogen. The tyndallization decreased the total amount of active cells from 1 × 108 to 1 × 102 CFU/ml. Hence, bio-augmentation with pigs' intestinal microbiota was absent and the community dynamics were mainly credited to the composition of the substrate (i.e. PM hydrolysates) and the environmental conditions inside the reactor. The results showed the influence of both the seed community and the imposed loading rates on the evolutionary trajectory of the EGSB microbial community. Four bacterial genera (Clostridium, Cytophaga, Bacillus and Bacteroides) and two methanogenic genera (Methanosaeta and Methanobacterium) dominated the communities. An obvious shift from aceticlastic Methanosaeta to hydrogenotrophic Methanobacterium appeared when the OLR was increased to over 10 kg-COD/(m3·d).

Imidazolio-substituted secondary phosphine oxides as potential carbene reagents

New pre-ligands of 1-aryl-1H-imidazol-2-yl substituted secondary phosphine oxides (HRP(O)-Im:SPO-Im) were prepared and characterized by spectroscopic means. The SPO-Im pre-ligands are able to tautomerize to their corresponding genuine ligands, the 1-aryl-1H-imidazol-2-yl substituted phosphinous acids ((HO)RP-Im:PA–Im) while the condition permitted. Further reactions of selected SPO-Im pre-ligands toward Pd(COD)Cl2 or PdBr yielded bis-(PA–Im)-coordinated cis-palladium dichloride or dibromide complexes, respectively. These cis-palladium dihalide complexes are all having an intramolecular hydrogen bond between two coordinated PA–Im ligands (R(Im(H)+)P–O−⋯HO–PRIm) by transferring a proton from one of the two P–OH groups to its free nitrogen site of imidazolyl substituents; and, therefore, imposes the formation of zwitterionic cis-form palladium complexes. Three crystal structures of these square–planar zwitterionic palladium complexes were determined by the X-ray diffraction methods. Additionally, two novel NHC carbene coordinated palladium complexes were obtained from the crystal-growing process of the above-mentioned zwitterionic cis-palladium dihalide complexes. The crystal structures of two NHC carbene coordinated palladium complexes were also successfully determined. Density-functional theory (DFT) calculations were carried out to substantiate the feasibility of the proposed reaction pathways for the formation of NHC carbene coordinated palladium complexes. Finally, applying selected SPO-Im pre-ligands to Heck reactions with pre-optimized reaction conditions exhibited satisfactory performances.

Evaluation of the modified HTK solution in pancreas transplantation—An experimental model

One of the great challenges in pancreas transplantation is the ischemia reperfusion injury. It is mentioned that free oxygen and/or nitrogen radicals play a prominent role in this phase. To minimize this problem, a modified histidine-tryptophan-ketoglutarate (HTK) solution that contains modified antioxidants has been developed. Our aim was to evaluate this solution in improving the viability of the pancreas in comparison with standard HTK and University of Wisconsin (UW) solutions in a porcine model of pancreas transplantation. Twenty-three Landrace pigs were divided into three identical groups. After a 10-hour preservation time at 4°C, the pancreas was implanted in the organs of the recipients in a standardized manner. Serum parameters were assessed prior to and after implantation on the 1(st) postoperative day, 3(rd) postoperative day, and 7(th) postoperative day. Furthermore, three biopsies were taken: prior to and after reperfusion, and on Day 7 to assess the grafts. An analysis of serum glucose among the three groups showed no significant differences. Evaluation of the insulin levels showed no significant difference between the modified and standard HTK groups; however, differences between HTK and UW were significant (p=0.004 in favor of UW solutions). The histopathological results showed a trend of a higher grade of rejection of pancreas tissue in the UW group compared to both HTK groups. The modified HTK solution could preserve the pancreas for the preservation of the graft with similar results to those observed for standard solutions without any significant difference. The trend showed that the pathological finding in the UW group was not as good as that in the modified HTK and standard HTK groups.

Nitric oxide maintains cell survival of Trichomonas vaginalis upon iron depletion.

BackgroundIron plays a pivotal role in the pathogenesis of Trichomonas vaginalis, the causative agent of highly prevalent human trichomoniasis. T. vaginalis resides in the vaginal region, where the iron concentration is constantly changing. Hence, T. vaginalis must adapt to variations in iron availability to establish and maintain an infection. The free radical signaling molecules reactive oxygen species (ROS) and reactive nitrogen species (RNS) have been proven to participate in iron deficiency in eukaryotes. However, little is known about the roles of these molecules in iron-deficient T. vaginalis.MethodsT. vaginalis cultured in iron-rich and -deficient conditions were collected for all experiments in this study. Next generation RNA sequencing was conducted to investigate the impact of iron on transcriptome of T. vaginalis. The cell viabilities were monitored after the trophozoites treated with the inhibitors of nitric oxide (NO) synthase (L-NG-monomethyl arginine, L-NMMA) and proteasome (MG132). Hydrogenosomal membrane potential was measured using JC-1 staining.ResultsWe demonstrated that NO rather than ROS accumulates in iron-deficient T. vaginalis. The level of NO was blocked by MG132 and L-NMMA, indicating that NO production is through a proteasome and arginine dependent pathway. We found that the inhibition of proteasome activity shortened the survival of iron-deficient cells compared with untreated iron-deficient cells. Surprisingly, the addition of arginine restored both NO level and the survival of proteasome-inhibited cells, suggesting that proteasome-derived NO is crucial for cell survival under iron-limited conditions. Additionally, NO maintains the hydrogenosomal membrane potential, a determinant for cell survival, emphasizing the cytoprotective effect of NO on iron-deficient T. vaginalis. Collectively, we determined that NO produced by the proteasome prolonged the survival of iron-deficient T. vaginalis via maintenance of the hydrogenosomal functions.ConclusionThe findings in this study provide a novel role of NO in adaptation to iron-deficient stress in T. vaginalis and shed light on a potential therapeutic strategy for trichomoniasis.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-015-1000-5) contains supplementary material, which is available to authorized users.

Influencing mechanism of high solid concentration on anaerobic mono-digestion of sewage sludge without agitation

High-solids anaerobic digestion of sewage sludge was a promising process, but high solid concentration negatively influenced methane production. The influencing mechanism was systematically analyzed in this study through a series of static anaerobic digestion experiments at total solids (TS) contents of 3%–15%. The results showed that TS 6% was the boundary between lowsolids and high-solids anaerobic digestion, and the accumulative methane yield decreased exponentially when TS increased from 6% to 15%. The performance of anaerobic digestion was directly determined by the efficiency of mass transfer, and the relation between methane yield and sludge diffusive coefficients was well described by a power function. Thus, the increasing TS resulted in an exponential increase in sludge viscosity but an exponential decrease in diffusive coefficient. The blocked mass transfer led to the accumulation of volatile fatty acids (VFAs) and free ammonia. Acetic metabolism was the main process, whereas butyric and propionic metabolisms occurred at the initial stage of high-solids anaerobic digestion. The concentration of VFAs reached the maximum at the initial stage, which were still lower than the threshold influencing methanogens. The concentration of free ammonia increased gradually, and the methanogenesis was inhibited when free ammonia nitrogen exceeded 50 mg·L–1. Consequently, the deterioration of high-solids anaerobic digestion was related to the blocked mass transfer and the resulting ammonia accumulation.

Effect of high temperature ageing on microstructure and mechanical properties of a nickel-free high nitrogen austenitic stainless steel

The effect of ageing and oxidation at 850°C for different durations viz., 1, 10, 100 and 200h on microstructure and mechanical properties of a nickel free high nitrogen steel (Fe–Cr–Mn–N) was investigated. The microstructure of the alloy in as-received condition essentially consists of fine equi-axed austenite grains with annealing twins. However, ageing at 850°C has resulted in the formation of very fine, globular and discrete Cr2N precipitates initially at grain boundaries for an ageing time of 1h and subsequently within the grains with increasing ageing time beyond 1h. The size of these precipitates has progressively increased with further ageing. In addition, coarse intermetallic precipitates of (Fe,Mn)Cr type with body centred tetragonal structure were observed in the samples aged for ≥100h at 850°C. The effect of these precipitates on mechanical properties of the alloy was studied. It was noticed that the mechanical properties deteriorated on ageing, which has been attributed to the depletion of solid solution strengthening elements like nitrogen, chromium and manganese from the matrix to form nitrides and intermetallic precipitates. Moreover the alloy aged in air (i.e., oxidised) exhibits marginally inferior tensile properties as compared to unoxidised alloy.

Modeling of Anaerobic Digestion with a Focus on Estimation of Hydrolysis Constants at 35, 55, and 60 °C.

Hydrolysis constants of mixed sludge at 35, 55, and 60 °C were found to be 0.32, 0.44, and 0.50 1/d, respectively, in pilot-scale, semicontinuously operated anaerobic digesters. The hydrolysis constants and estimated chemical oxygen demand fractions in the feed were introduced to a mathematical model for anaerobic digestion published by Siegrist et al. (2002), which is similar to Anaerobic Digestion Model No. 1. First-order and Monod-type kinetics were tested for estimation of hydrolysis constants. The applied kinetics were found to affect the outcome of the regression study. Moreover, the free ammonia inhibition model was excluded for both propionate oxidation and acetate conversion, thanks to the apparent acclimatized biomass. No substantial accumulation of volatile fatty acids was observed in the reactors at 35, 55, and 60 °C, corresponding to free ammonia nitrogen concentrations of about 20, 110, and 130 g N/m³, respectively.

Highly Selective and Sensitive Luminescence Turn-On-Based Sensing of Al(3+) Ions in Aqueous Medium Using a MOF with Free Functional Sites.

A new metal-organic framework [Co(OBA)(DATZ)0.5(H2O)] {OBA = 4,4'-oxybis(benzoic acid) and DATZ = 3,5-diamino-1,2,4-triazole}, 1, was synthesized by hydrothermal reaction. Single-crystal X-ray data of 1 confirmed two-dimensional rhombus grid network topology with a free nitrogen site of triazole ring and two amine groups of each DATZ. Photoluminescence study of 1 in aqueous medium shows blue emission at 407 nm upon excitation at 283 nm. This emissive property was used for the sensing of Al(3+) ions in aqueous medium through very high luminescence turn-on (6.3-fold) along with the blue shifting (∼24 nm) of the emission peak. However, luminescence studies in the presence of other common metal ions such as Mg(2+), Zn(2+), Ni(2+), Co(2+), Mn(2+), K(+), Na(+), Ca(2+), Cd(2+), Hg(2+), Cu(2+), Fe(2+), Fe(3+), and Cr(3+) in aqueous medium shows luminescence quenching in varying extent. Interestingly, the luminescence turn-on-based selectivity of Al(3+) ions in aqueous medium was achieved even in the presence of the highest quenchable metal ion, Fe(3+). Furthermore, very high sensitivity was observed in the case of Al(3+) ions with a limit of detection of Al(3+) of 57.5 ppb, which is significantly lower than the higher limit of U.S. Environmental Protection Agency recommendation of Al(3+) ion for drinking water (200 ppb).

UV-Induced DNA Interstrand Cross-Linking and Direct Strand Breaks from a New Type of Binitroimidazole Analogue.

Four novel photoactivated binitroimidazole prodrugs were synthesized. These agents produced DNA interstrand cross-links (ICLs) and direct strand breaks (DSB) upon UV irradiation, whereas no or very few DNA ICLs and DSBs were observed without UV treatment. Although these four molecules (1-4) contain the same binitroimidazole moiety, they bear four different leaving groups, which resulted in their producing different yields of DNA damage. Compound 4, with nitrogen mustard as a leaving group, showed the highest ICL yield. Surprisingly, compounds 1-3, without any alkylating functional group, also induced DNA ICL formation, although they did so with lower yields, which suggested that the binitroimidazole moiety released from UV irradiation of 1-3 is capable of cross-linking DNA. The DNA cross-linked products induced by these compounds were completely destroyed upon 1.0 M piperidine treatment at 90 °C (leading to cleavage at dG sites), which revealed that DNA cross-linking mainly occurred via alkylation of dGs. We proposed a possible mechanism by which alkylating agents were released from these compounds. HRMS and NMR analysis confirmed that free nitrogen mustards were generated by UV irradiation of 4. Suppression of DNA ICL and DSB formation by a radical trap, TEMPO, indicated the involvement of free radicals in the photo reactions of 3 and 4 with DNA. On the basis of these data, we propose that UV irradiation of compounds 1-4 generated a binitroimidazole intermediate that cross-links DNA. The higher ICL yield observed with 4 resulted from the amine effector nitrogen mustard released from UV irradiation.