Pulse radiolysis studies on hydroxyl (*OH) radical reactions of selenomethionine (SeM), a selenium analogue of methionine, were carried out, and the resultant transient radical cations and their subsequent reactions have been reported. At pH<3, the >Se*-OH radical adducts produced on reaction of SeM with *OH radical were converted to selenium centered radical cations (Se*+M), which react with another molecule of SeM to form dimer radical cation M(Se therefore Se)M+. At pH 7, the >Se*-OH radical adducts were converted to a monomer radical of the type (Se therefore N)M+ that acquires intramolecular stability through interaction with the lone pair of the N atom and this radical is denoted as SeM*+. SeM*+ decayed by first order kinetics, and the reduction potential of the couple SeM*+/SeM was determined to be 1.21+/-0.05 V vs NHE at pH 7. SeM*+ oxidized ABTS2- and TMPD with rate constants of (2.5+/-0.1)x10(8) and (6.1+/-0.2)x10(8) M(-1) s(-1), respectively, and reacted with hydroxide ion with a rate constant of (3.8+/-0.9)x10(5) M(-1) s(-1). SeM*+ reacts with molecular oxygen, and the rate constant for this reaction was determined to be (4.3+/-0.2)x10(8) M(-1) s(-1); similar reaction with methionine could not be observed experimentally. Like methionine radical cations, SeM*+ undergoes decarboxylation, although with lesser yield, to produce reducing 3-methyl-selenopropyl amino radicals (referred as alpha-amino radicals). The formation of these radicals was confirmed both by the estimation of the liberated CO2 and by one-electron reduction of MV2+, thionine, and PNAP. These results have been supported by quantum chemical calculations. Implications of these results in the biological role of SeM have also been briefly discussed.

The present study investigated the comprehensive chemical composition [organic carbon (OC), elemental carbon (EC), water-soluble inorganic ionic components (WSICs), and major & trace elements] of particulate matter (PM) and scrutinized their emission sources for urban region of Delhi. The 135 PM samples were collected from January 2013 to December 2014 and analyzed for chemical constituents for source apportionment study. The average concentration of PM was recorded as 121.9 ± 93.2 μg m (range 25.1-429.8 μg m), whereas the total concentration of trace elements (Na, Ca, Mg, Al, S, Cl, K, Cr, Si, Ti, As, Br, Pb, Fe, Zn, and Mn) was accounted for ∼17% of PM. Strong seasonal variation was observed in PM mass concentration and its chemical composition with maxima during winter and minima during monsoon seasons. The chemical composition of the PM was reconstructed using IMPROVE equation, which was observed to be in good agreement with the gravimetric mass. Source apportionment of PM was carried out using the following three different receptor models: principal component analysis with absolute principal component scores (PCA/APCS), which identified five major sources; UNMIX which identified four major sources; and positive matrix factorization (PMF), which explored seven major sources. The applied models were able to identify the major sources contributing to the PM and re-confirmed that secondary aerosols (SAs), soil/road dust (SD), vehicular emissions (VEs), biomass burning (BB), fossil fuel combustion (FFC), and industrial emission (IE) were dominant contributors to PM in Delhi. The influences of local and regional sources were also explored using 5-day backward air mass trajectory analysis, cluster analysis, and potential source contribution function (PSCF). Cluster and PSCF results indicated that local as well as long-transported PM from the north-west India and Pakistan were mostly pertinent.

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Pseudomonas exotoxin (PE)-based immunotoxins (antibody-toxin fusion proteins) have achieved frequent complete remissions in patients with hairy cell leukemia but far fewer objective responses in other cancers. To address possible mechanisms of resistance, we investigated immunotoxin activity in a model system using the colon cancer cell line, DLD1. Despite causing complete inhibition of protein synthesis, there was no evidence that an immunotoxin targeted to the transferrin receptor caused apoptosis in these cells. To address a possible protective role of prosurvival Bcl-2 proteins, the BH3-only mimetic, ABT-737, was tested alone or in combination with immunotoxins. Neither the immunotoxin nor ABT-737 alone activated caspase 3, whereas the combination exhibited substantial activation. In other epithelial cell lines, ABT-737 enhanced the cytotoxicity of PE-related immunotoxins by as much as 20-fold, but did not enhance diphtheria toxin or cycloheximide. Because PE translocates to the cytosol via the endoplasmic reticulum (ER) and the other toxins do not, ABT-737-mediated effects on the ER were investigated. ABT-737 treatment stimulated increased levels of ER stress response factor, ATF4. Because of its activity in the ER, ABT-737 might be particularly well suited for enhancing the activity of immunotoxins that translocate from the ER to the cell cytosol.