Unique emission from norbornene derived terpyridine--a selective chemodosimeter for G-type nerve agent surrogates

A new chemodosimeter for a G-type agent that exploits norbornene derived terpyridine (NDT)-lanthanide unique emission is reported. The unusual emission between terpyridine and norbornene motifs of NDT is attributed to the significant difference in the position of the HOMO and LUMO wave functions that prevents the non-radiative relaxation pathway. An interesting magenta emission from NDT along with Eu(III) is utilized as a new fluorometric chemodosimeter that selectively detects (by changing the observed magenta emission to blue) G-type agent surrogates. A detection limit of 40 ppb is obtained and the selectivity for reactive surrogates over a variety of other close chemical analogs is demonstrated.     

Repeated dose 28-days oral toxicity study of Carica papaya L. leaf extract in Sprague Dawley rats

Carica papaya L. leaves have been used in ethnomedicine for the treatment of fevers and cancers. Despite its benefits, very few studies on their potential toxicity have been described. The aim of the present study was to characterize the chemical composition of the leaf extract from 'Sekaki' C. papaya cultivar by UPLC-TripleTOF-ESI-MS and to investigate the sub-acute oral toxicity in Sprague Dawley rats at doses of 0.01, 0.14 and 2 g/kg by examining the general behavior, clinical signs, hematological parameters, serum biochemistry and histopathology changes. A total of twelve compounds consisting of one piperidine alkaloid, two organic acids, six malic acid derivatives, and four flavonol glycosides were characterized or tentatively identified in the C. papaya leaf extract. In the sub-acute study, the C. papaya extract did not cause mortality nor were treatment-related changes in body weight, food intake, water level, and hematological parameters observed between treatment and control groups. Some biochemical parameters such as the total protein, HDL-cholesterol, AST, ALT and ALP were elevated in a non-dose dependent manner. Histopathological examination of all organs including liver did not reveal morphological alteration. Other parameters showed non-significant differences between treatment and control groups. The present results suggest that C. papaya leaf extract at a dose up to fourteen times the levels employed in practical use in traditional medicine in Malaysia could be considered safe as a medicinal agent.     

A HYSCORE investigation of bimetallic titanium-vanadium microporous catalysts: elucidating the nature of the active sites

Vanadium and titanium bimetallic AlPO-5 molecular sieves have been synthesized and characterized by means of Electron Spin Echo detected EPR and Hyperfine Sublevel Correlation (HYSCORE) spectroscopy. Direct evidence for framework substitution of redox-active Ti ions and VO(2+) units at Al sites is provided through the detection of large (31)P hyperfine couplings.     

Ru(x)Pt(y)Sn(z) cluster-derived nanoparticle catalysts: spectroscopic investigation into the nature of active multinuclear single sites

Cluster-derived Ru(x)Pt(y)Sn(z) nanoparticles are active catalysts in the hydrogenation of nitrobenzene. The nature of the active sites has been elucidated by FTIR spectroscopy using CO and NO as probe molecules. A new metal carbonyl cluster precursor, Pt(2)Ru(2)(SnBu(t)(3))(2)(CO)(9)(μ-H)(2), has been synthesized to obtain a Ru(2)Pt(2)Sn(2)/SiO(2) catalyst, that displayed remarkably high levels of conversion and selectivities compared to other bi-and monometallic analogues. Spectroscopic comparisons with Ru(5)PtSn/SiO(2) indicate that both the nature and the stoichiometry of the metals play a key role in modulating the catalytic activities and selectivities. A multinuclear single-site containing Pt centers, which facilitate the hydrogen activation, coupled with a highly reactive Ru site, possibly involved in the nitrobenzene activation, can be hypothesized. The oxophilicity of tin helps with the anchoring of the nanoparticles, aids the dispersion of the other metals, and can play an important role in influencing the selectivity to aniline.     

Capture of sunflower seedlings lipase using polyclonal antibodies

True lipolytic activity is observed in different subcellular fractions of germinating sunflower seedlings (Helianthus annuus L.) in delipidated oleosomes and microsomes. Triacylglycerol lipase (EC. 3.1.1.3) catalyses the first catabolic step of lipolysis. To our knowledge, this plant lipase has not yet been identified. Our aim was to develop a method to collect the lipase for further studies. An immunological method was used to capture sunflower seedling lipase from oleosomes and microsomes. This method uses an immunoaffinity column prepared with polyclonal antibodies (anti-P-61) directed against oleosomal activity. Our results verify that we have successfully adapted a purification procedure of plant lipase using anti-P-61. Since the eluted lipolytic activity is distributed among diverse proteic peaks, we changed the elution procedure: the introduction of CHAPS, a zwitterionic detergent, allowed us to recover all the lipolytic activity in a single proteic peak. This may help us to characterise the studied lipase.     

Antifouling and antipredatory activity of natural products of the seaweeds Dictyota dichotoma and Chaetomorpha linoides

The seaweeds Dictyota dichotoma and Chaetomorpha linoides from the southeast coast of India were screened for anti-microfouling activity against biofilm bacteria, anti-macrofouling activity against brown mussels and feeding deterrence activity against the sea angel Monodactylus kottelati. The surface associated epiphytic bacteria were also isolated from seaweeds and screened for activity against biofilm bacteria. The acetone extracts showed a wide spectrum activity against biofilm bacteria and the algal metabolite was surface concentrated and non-polar in nature. The seaweeds also inhibited byssus production and attachment in brown mussels, and deterred feeding in the sea angel. The lower epiphytic bacterial number on the seaweed's surface compared to the surrounding seawater medium indicated selective inhibition or surface mediation. The epiphytic bacteria, which showed activity against biofilm bacteria, might also possibly play a role in seaweed defence strategies. The 50% deterrence of feeding activity at lower concentrations was not proportionate to the 100% inhibition concentration, which could be attributed to the adaptability of the fishes, an indication that the active substances are inhibitory in nature. This was further substantiated with the 100% recovery of mussels in a toxicity assay and the lower EC(50) values than LC(50) values in the mussel bioassay. The study indicates that the metabolites of both seaweeds have ecological significance and could possibly play a multifunctional role.     

Up-conversion enhancement in Er3 +-Ag co-doped zinc tellurite glass: Effect of heat treatment

The melt quenching method was used to synthesize the Ag⁰ nanoparticles and Er^3 + ions co-doped zinc tellurite glass. The glasses were characterized by differential thermal analyzer, UV–VIS-IR absorption, photoluminescence spectroscopy and TEM imaging. Heat treatment at different annealing time intervals above the glass transition temperature was applied to reduce the Ag⁺ ions to Ag⁰ NPs. The influence of heat treatment on structural and optical properties is examined. Intense and broad up-conversion emissions of silver are recorded in the visible region. Up-conversion luminescence spectra revealed three major emission peaks at 520, 550 and 650 nm originating from ²H_11/2, ⁴S_3/2 and ⁴F_9/2 levels, respectively. An efficient enhancement in visible region is observed for samples containing silver NPs. The absorption plasmon peaks are evidenced around 560 and 594 nm. The effect of localized surface plasmon resonance and the energy transfer from the surface of silver NP to trivalent erbium ions are described as the sources of enhancement.     

Electrode reactions during electrolytic preparation of nickel hydroxide

We investigate the electrode reactions involved in the electrolytic precipitation of nickel hydroxide from nickel nitrate through quantitative assessment of the reaction products using stainless steel cathode with Ti and Ni anodes. The nitrate ion is reduced at the cathode to form nitrite and ammonium ion, the later being the major product. The production of ammonium ion followed either directly via reduction of nitrate to ammonium ion or in steps via nitrate reduction to nitrite which further reduced to ammonium ion. Finally, we report XRD measurements, tap density, and the discharge capacity performed on the electrolytically precipitated Ni(OH)₂.     

Synthesis, optical, electrochemical, and thermal studies on triazole-based dendrimers with diphenylamine as surface group

Fréchet-type dendrimers with hole-transporting diphenylamine as surface group and electron-transporting triazole moiety as building block have been synthesized by convergent synthetic strategy through ‘click chemistry’ methodology. First generation dendrimer exhibits longer relaxation time, higher quantum yield in the fluorescence spectrum, and better thermal stability than the zero and second generation dendrimers. CV studies showed irreversible reduction potential and the formation of radical cation due to diphenylamine moiety.     

Determination of Toxic Elements in Muscle Tissues of Five Fish Species Using Ultrasound‐Assisted Pseudodigestion by Electrothermal Atomic Absorption Spectrophotometry: Optimization Study

A simple and rapid method is described for the determination of As, Cd, and Pb in muscle tissue of five freshwater fish species by ultrasound‐assisted pseudodigestion (USD). A Plackett‐Burman experimental design was used as a multivariate strategy for the evaluation of the effects of varying several variables at once. The variables such as sonication time (ST), sample mass of muscle tissues (SM), temperature of ultrasonic bath (T), nitric acid (A1), and mixture of acid and oxidant (A2) have been studied. From these studies, some variables showed significant effect on % recovery, and they were further optimized by a 2³+star central composite design, which involved 16 experiments. Optimum values of the variables were selected for the development of USD to determine the contents of As, Cd, and Pb in muscle tissue of five fish species, used as bioindicators for Lake Manchar (Sindh, Pakistan) to know whether consumption of these fishes threatens human health. The determination of three toxic elements under study was carried out by electrothermal atomic absorption spectrometry (ETAAS). The accuracy of the optimized procedure was evaluated by analysis of certified reference materials DORM‐2 (Dogfish Muscle Certified Reference Material for Trace Elements) and by comparison with conventional wet acid digestion methodology. No significant differences were observed for p=0.05 when comparing the values obtained by the proposed USD method and conventional digestion method (CDM) (paired t‐test). The average relative standard deviation of the USD method varied between 4.05%, 7.53%, and 4.55% for As, Cd, and Pb, respectively (n=10).