Direct Blue Light-Induced Autocatalytic Oxidation of o-Phenylenediamine for Highly Sensitive Visual Detection of Triaminotrinitrobenzene.

o-Phenylenediamine (OPD)-based chromogenic reactions are worthy tools for the development of visual colorimetric assays. The chromogenic reactions are usually triggered by various oxidants, which is not easily tunable and incompatible with some analytes. Herein, we report that direct blue light irradiation can induce the autocatalytic oxidation of OPD to generate 2,3-diaminophenazine (oxidized-state OPD, oxOPD). The autocatalytic photo-oxidation reaction mechanism of OPD is mainly ascribed to the resonant energy transfer between ectronically excited oxOPD and dissolved oxygen to form singlet state oxygen with a high oxidation capacity, which accelerates the oxidation of OPD. We demonstrate that under neutral and alkaline environment, the photoinduced autocatalytic oxidation of OPD is able to be further enhanced by triaminotrinitrobenzene (TATB) explosive because of its inhibition effect on the aggregation caused quenching phenomenon of oxOPD. On this basis, a straightforward visual colorimetric assay for TATB with a tunable dynamic range is developed. This assay is capable of detecting TATB explosive concentrations as low as 2.7 nM. Notably, the obvious color change after addition of TATB enables a naked-eye readout with the lowest detectable TATB concentrations of 60 nM.

Chiral porphyrin dimer with a macrocyclic cavity for intercalation of aromatic guests.

Chiral diporphyrin receptor 1, which has a macrocyclic cavity to sandwich aromatic guest molecules via double π-π stacking interactions, enabled the naked-eye detection of an aromatic explosive as well as chiral discrimination in NMR.

Water-stable organic transistors and their application in chemical and biological sensors.

The development of low-cost, reliable sensors will rely on devices capable of converting an analyte binding event to an easily read electrical signal. Organic thin-film transistors (OTFTs) are ideal for inexpensive, single-use chemical or biological sensors because of their compatibility with flexible, large-area substrates, simple processing, and highly tunable active layer materials. We have fabricated low-operating voltage OTFTs with a cross-linked polymer gate dielectric, which display stable operation under aqueous conditions over >10(4) electrical cycles using the p-channel semiconductor 5,5'-bis-(7-dodecyl-9H-fluoren-2-yl)-2,2'-bithiophene (DDFTTF). OTFT sensors were demonstrated in aqueous solutions with concentrations as low as parts per billion for trinitrobenzene, methylphosphonic acid, cysteine, and glucose. This work demonstrates of reliable OTFT operation in aqueous media, hence opening new possibilities of chemical and biological sensing with OTFTs.

Environmental process descriptors for TNT, TNT-related compounds and picric acid in marine sediment slurries.

Process descriptors were determined for picric acid, TNT, and the TNT-related compounds 2,4DNT, 2,6DNT, 2ADNT, 4ADNT, 2,4DANT, 2,6DANT, TNB and DNB in marine sediment slurries. Three marine sediments of various physical characteristics (particle size ranging from 15 to >90% fines and total organic carbon ranging from <0.10 to 3.60%) were kept in suspension with 20ppt saline water. Concentrations of TNT and its related compounds decreased immediately upon contact with the marine sediment slurries, with aqueous concentrations slowly declining throughout the remaining test period. Sediment-water partition coefficients could not be determined for these compounds since solution phase concentrations were unstable. Kinetic rates and half-lives were influenced by the sediment properties, with the finer grained, higher organic carbon sediment being the most reactive. Aqueous concentrations of picric acid were very stable, demonstrating little partitioning to the sediments. Degradation to picramic acid was minimal, exhibiting concentrations at or just above the detection limit.

An enzyme-labeled protein polymer bearing pendent haptens.

A new methodology for the preparation of enzyme-labeled protein polymers bearing pendent haptens was developed through the combination of chemical modification and posttranslational protein modification catalyzed by microbial transglutaminase (MTG). As a model hapten, trinitrobenzene (TNB) was chosen and chemically conjugated with the accessible Lys residues of beta-casein. The resultant trinitrophenylated beta-casein was further modified with formaldehyde to render the residual Lys residues inert toward self-cross-linking by MTG. Escherichia coli alkaline phosphatase (AP), comprising a specific peptide tag carrying a MTG-reactive Lys residue, was then conjugated to the Gln residues in beta-casein-TNB conjugates. The resultant AP-labeled beta-casein-bearing pendent TNB moieties (AP-betaCT) showed comparable specific activity with native AP. It was found that only the AP-betaCT with a sufficient number of pendent TNBs are capable of binding to a surface adsorbed with anti-TNP and anti-TNT antibodies, indicating the presence of polyvalent interactions. The utility of AP-betaCT was demonstrated by competitive immunoassays for trinitrophenol (TNP) and trinitrotoluene (TNT), with detection limits of 0.99 microg/L and 0.18 microg/L, respectively. The present study demonstrates the potential of dual labeling of protein scaffolds by chemical and enzymatic protein manipulation to create a new proteinaceous architecture.

Detection of nitroaromatic and cyclic nitramine compounds by cyclodextrin assisted capillary electrophoresis quadrupole ion trap mass spectrometry.

An Agilent 3DCE capillary electrophoresis system using sulfobutylether-beta-cyclodextrin (SB-beta-CD)-ammonium acetate separation buffer pH 6.9 was coupled to a Bruker Esquire 3000+ quadrupole ion trap mass detector via a commercially available electrospray ionization interface with acetonitrile sheath flow. The CE-MS system was applied in negative ionization mode for the resolution and detection of nitroaromatic and polar cyclic or caged nitramine energetic materials including TNT [2,4,6-trinitrotoluene, formula mass (FW) 227.13], TNB (1,3,5-trinitrobenzene, FW 213.12), RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine, FW 222.26) HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, FW 296.16), and CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane, FW 438.19). The CE-MS system conformed to the high-performance liquid chromatography with ultraviolet absorbance detection (HPLC-UV) and HPLC-MS reference methods for the identification of energetic contaminants and their degradation products in soil and marine sediment samples.

Mechanisms for the adsorption of substituted nitrobenzenes by smectite clays.

To more fully understand the potential for transport of nitroaromatic compounds in soils and subsoils,the adsorption of a series of para- and meta-substituted nitrobenzenes (SNBs) by K-smectite clay was measured. Adsorption isotherms were fit to the Freundlich equation, and the resultant Freundlich adsorption coefficients (log(Kf) were positively correlated with the Hammett substituent constant (r2 = 0.80). This relationship and a positive reaction constant (p = 1.15) indicate that the adsorption reaction is favored by electron-withdrawing substituents. These results are consistent with an electron donor (smectite)-acceptor (substituted nitrobenzene) mechanism offered previously. However, quantum calculations did not reveal any systematic relationship between the Hammett constant and the electron density on the aromatic ring, which would explain a donor-acceptor relationship. Rather, electron density donated by a second substituent on nitrobenzene appears to be appropriated by the nitro group leaving ring electron density unchanged. Fourier transform infrared spectroscopy revealed shifts in the -NO2 vibrational modes of 1,3,5-trinitrobenzene (TNB) upon adsorption to K+-smectite that were consistent with the complexation of K+ by -NO2 groups. Such TNB vibrational shifts were not observed for SWy-1 saturated with more strongly hydrated cations (i.e., Na+, Mg2+, Ca2+, and Ba2+). The simultaneous interaction of multiple -NO2 groups with exchangeable K+ was indicated by molecular dynamic simulations. Adsorption of SNBs by smectite clays appears to result from the additive interactions of -NO2 groups and secondary substituents with interlayer K+ ions. Adsorption occurs to a greater or lesser extent depending on the abilities of substituents to complex additional interlayer cations and the water solubilities of SNBs. We conclude that the adsorption trends of SNBs on K-SAz-1 can be explained without recourse to hypothetical electron donor-acceptor complexes.

Influence of solvents and gas chromatographic injector conditions on the detectability of nitroaromatic compounds.

We investigated the influence of four common solvents and of several liner packings of a split/splitless injector on the gas chromatographic behavior of trinitrotoluenes and related nitroaromatic compounds. The highest peaks are observed using toluene in combination with an empty liner or with a prepacked CarboFrit liner. In particular, the peaks of trinitrotoluene isomers and 1,3,5-trinitrobenzene significantly decreased or even totally disappeared when using quartz wool or glass wool, even when treated with dimethylchlorosilane. Similiar peak reductions are obtained with methanol or acetonitrile. Effects of decreasing peak are accompanied by the formation of two additional products when using methanol.

Use of a Salmonella microsuspension bioassay to detect the mutagenicity of munitions compounds at low concentrations.

Past production and handling of munitions has resulted in soil contamination at various military facilities. Depending on the concentrations present, these soils pose both a reactivity and toxicity hazard and the potential for groundwater contamination. Many munitions-related chemicals have been examined for mutagenicity in the Ames test, but because the metabolites may be present in low environmental concentrations, a more sensitive method is needed to elucidate the associated mutagenicity. RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), TNT (2,4,6-trinitrotoluene), tetryl (N-methyl-N-2,4,6-tetranitroaniline), TNB (1,3,5-trinitrobenzene) and metabolites were examined for mutagenicity in a microsuspension modification of the Salmonella histidine reversion assay with and without metabolic activation. TNB and tetryl were positive in TA98 (32.5, 5.2revertants/nmole) and TA100 (7.4, 9.5revertants/nmole) without metabolic activation and were more potent than TNT (TA98, 0.3revertants/nmole; TA100, 2.4revertants/nmole). With the exception of the tetranitroazoxytoluene derivatives, TNT metabolites were less mutagenic than TNT. RDX and two metabolites were negative in both strains, however, hexahydro-1,3,5-trinitroso-1,3,5-triazine was positive in TA100 with and without S9. Microsuspension bioassay results tend to correlate well with published Ames test data, however, there are discrepancies among the published data sets and the microsuspension assay results.

Determination of explosives in soil and ground water by liquid chromatography-amperometric detection.

Electrochemical reduction of trinitrotoluene (TNT) and several nitroaromatics has been exploited toward the development of an amperometric detector for liquid chromatography (LC). Up to a ten-fold increase in sensitivity was accomplished for the explosives using amperometric detection instead of conventional UV measurement. A working glassy carbon electrode (poised at -0.80 V vs. Ag/AgCl) offered a detection limit of 9, 44 and 550 nM for trinitrobenzene, TNT and 1,4-dinitrobenzene, respectively. Separation of eleven TNT-related compounds in a mixture was achieved within 15 min using a C18 column and a mobile phase consisting of acetonitrile-50 mM phosphate buffer pH 5 (1:2, v/v) and 18 mM sodium dodecylsulfate. The LC-amperometric detection system was applicable for analyzing soil extracts and ground water and the results obtained agreed well with that of the US Environmental Protection Agency recommended procedure. Extension to analysis of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) and RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) was accomplished with a silver working electrode instead of a glassy carbon electrode installed in a thin channel cell.

The quantification of protein amino groups by the trinitrobenzenesulfonic acid method: a reexamination.

Trinitrobenzenesulfonic acid (TNBSA) is the reagent in a well-known method for quantification of primary amino groups, but even at room temperature, N-trinitrophenylation of primary amines is concomitant with hydrolysis of the reagent. The production of picric acid, the product of TNBSA hydrolysis, lowers the sensitivity of the method. Heating accelerates hydrolysis more than condensation on amino groups. The optimal pH range is centered on the value 10. The optical density is generally evaluated at 340 or 420 nm. The former value corresponds to the maximal absorption of the final product, N-trinitrophenylamines. The latter value is relative to the Mesenheimer pi-complex, the well-known intermediate of the overall reaction. Both wavelengths are suitable for quantification of amines, but 420 nm seems to be the best. Further addition of sulfite is not necessary. The quantification of amines is somewhat hampered by compounds such as area and sodium dodecyl anions. The relative rates of reaction of diaminoacyl groups of protein with TNBSA differ depending on the substitution degree of the neighboring groups. Some of them do not react. The trinitrophenylation kinetic seems to be more dependent on protein structure than reactivity. In evaluation of the available lysine in glycated proteins, the distinction between reductive alkylation and Maillard-type condensation necessitates quantitative evaluation of nonalkylated lysine in protein hydrolysate, compared to results with the TNBSA method. Our results are confirmed by complete guanidization of the protein and subsequent determination of homoarginine in hydrolysates.

A microcosm study on remediation of explosives-contaminated groundwater using constructed wetlands.

Anaerobic degradation of TNT and TNB in gravel systems was rapid and similar to removal rates in parrot feather lagoons. Planted and unplanted anaerobic gravel systems were the only treatments that provided significant reduction of RDX and HMX. Planted systems with parrot feather had no effect on removal rates of explosives in anaerobic gravel systems. Reciprocating wetlands were not effective in biodegrading RDX or HMX, but were very efficient at removing COD. A scaled-up concept for bioremediating contaminated groundwater can be envisioned with the data obtained in the current study. The effectiveness of anaerobic gravel systems indicate an anaerobic subsurface-flow constructed wetland can be established as the primary treatment for remediation with C added to the influent or step fed down the length of the wetland. Another option would be to add compost as a more permanent source of C to the gravel substrate. With time, the need for C supplementation may be reduced with the C exudates and redox lowering potential of certain plants like canarygrass (Phalaris arundinacea). As a secondary treatment, a reciprocating wetland would appear to be a logical choice to quickly remove C released in effluent waters of the anaerobic wetland.

Increasing age alters transbilayer fluidity and cholesterol asymmetry in synaptic plasma membranes of mice.

Previous studies examining age differences in membrane fluidity and cholesterol content have reported on the average or total change in membrane structure, respectively. However, a membrane consists of an exofacial leaflet and a cytofacial leaflet that differ in fluidity and cholesterol distribution. The purpose of the present experiments was to determine fluidity and cholesterol distribution of the exofacial and cytofacial leaflets of brain synaptic plasma membranes (SPMs) from 3-4-, 14-15-, and 24-25-month old C57BL/6NNIA mice by using trinitrobenzenesulfonic acid (TNBS)-quenching techniques and fluorescent probes. The exofacial leaflet of SPMs from young mice was significantly more fluid compared with the cytofacial leaflet. The large difference in fluidity between the two leaflets was abolished in SPMs of the oldest age group. Total SPM cholesterol and the cholesterol-to-phospholipid molar ratio did not differ among the three different age groups of mice. However, considerable differences were observed in the distribution of cholesterol in the two SPM leaflets. The exofacial leaflet contained substantially less cholesterol than did the cytofacial leaflet (13 vs. 87%, respectively) in SPMs of young mice. This asymmetric distribution of cholesterol was significantly modified with increasing age. There was an approximately twofold increase in exofacial leaflet cholesterol in the oldest group compared with the youngest age group. Transbilayer fluidity and cholesterol asymmetry were altered in SPMs of older mice. This approach is a new and different way of viewing how aging modifies membrane structure. Age differences in SPM leaflet structure may be an important factor regulating activity of certain membrane proteins.

Enhanced transcription in a pre-B-like cell line transformed with cloned antibody genes after antigen-specific stimulation.

The transducing vector, pSV2-neo, carrying the rearranged immunoglobulin (Ig) heavy (mu) and light (kappa) chain genes specific for the hapten 2,4,6-trinitrophenyl (TNP) was introduced into a pre-B cell line. The transformants expressed the TNP-specific IgM receptor on the surface. Furthermore, the addition of TNP-bovine serum albumin (hapten-carrier conjugate) to the culture media activated the expression of the transferred Ig genes and several endogenous genes such as v-abl and beta-tubulin. However, expression of the beta2-microglobulin gene was not affected. The results presented in this paper show that transfection of cloned Ig genes into B cells is a useful system for establishing monoclonal B cell lines expressing functional Ig receptor molecules with defined hapten specificity.

Biochemical characteristics of cardiac myosin: the pH dependence of Ca-ATPase activity, and that of the absorption spectrum of 2,4,6-trinitrophenyl groups attached to myosin.

For both cardiac and skeletal myosin, the Ca-ATPase activity of myosin at acidic pH was shown to be different from that at alkaline pH, in the susceptibility to heat-inactivation, the effects of organic solvents, and the effect of trinitrophenylation of the myosin. It is therefore suggested that there are two different types of Ca-ATPase of both cardiac and skeletal myosin. Differences in the Ca-ATPase activity were also found between cardiac and skeletal myosins. (a) The Ca-ATPase activity of cardiac myosin was more susceptible to heat-inactivation at alkaline pH than at acidic pH. In contrast, the activity of skeletal myosin was more susceptible to heat-inactivation at acidic pH than at alkaline pH. (b) Dioxane weakly stimulated the activity of cardiac myosin at acidic pH, but strongly activated that of skeletal myosin at acidic pH. Acetone very strongly inhibited the activity of cardiac myosin at alkaline pH, but not so strongly that of skeletal myosin at alkaline pH. (c) Trinitrophenylation of the myosin resulted in loss of the activity optimum at acidic pH with skeletal myosin but not with cardiac myosin. As reported by Srivastava et al. (J. Biochem. 86, 725-731, 1979), 1 mol of lysine residue per mol of cardiac myosin quickly reacted with 2,4,6-trinitrobenzene sulfonate (TNBS) either in the absence or presence of inorganic pyrophosphate (PPi). However, trinitrophenyl (TNP) groups bound to cardiac myosin in the presence of PPi were significantly different, in the pH dependence of the absorption spectrum, from those bound (to cardiac myosin) in the absence of PPi.(ABSTRACT TRUNCATED AT 250 WORDS)