Presence Of Diphenylamine Research Articles

New insights on the photocomplex of Roseiflexus castenholzii revealed from comparisons of native and carotenoid-depleted complexes

In wild-type phototrophic organisms, carotenoids (Crts) are primarily packed into specific pigment-protein complexes along with (Bacterio)chlorophylls and play important roles in the photosynthesis. Diphenylamine (DPA) inhibits carotenogenesis but not phototrophic growth of anoxygenic phototrophs and eliminates virtually all Crts from photocomplexes. To investigate the effect of Crts on assembly of the reaction center-light-harvesting (RC-LH) complex from the filamentous anoxygenic phototroph Roseiflexus (Rfl.) castenholzii, we generated carotenoidless (Crt-less) RC-LH complexes by growing cells in the presence of DPA. Here, we present cryo-EM structures of the Rfl. castenholzii native and Crt-less RC-LH complexes with resolutions of 2.86Å and 2.85Å, respectively. From the high-quality map obtained, several important but previously unresolved details in the Rfl. castenholzii RC-LH structure were determined unambiguously including the assignment and likely function of three small polypeptides, and the content and spatial arrangement of Crts with bacteriochlorophyll molecules. The overall structures of Crt-containing and Crt-less complexes are similar. However, structural comparisons showed that only five Crts remain in complexes from DPA-treated cells and that the subunit X (TMx) flanked on the N-terminal helix of the Cyt-subunit is missing. Based on these results, the function of Crts in the assembly of the Rfl. castenholzii RC-LH complex and the molecular mechanism of quinone exchange is discussed. These structural details provide a fresh look at the photosynthetic apparatus of an evolutionary ancient phototroph as well as new insights into the importance of Crts for proper assembly and functioning of the RC-LH complex.

The Photoluminescence and Vibrational Properties of Black Phosphorous Sheets Chemically/Electrochemically Functionalized in the Presence of Diphenylamine.

In this work, new information concerning the optical properties of black phosphorus (BP) sheets chemically/electrochemically functionalized with diphenyl amine (DPA) and its macromolecular compound (poly(diphenylamine) (PDPA)) in the absence/presence of phosphotungstic acid (PTA) is reported. Raman scattering and FTIR spectroscopy studies indicate that the interaction of BP with PTA leads to the elimination of the PxOy layer onto the surface of the BP sheets. In the case of the chemical interaction of BP with DPA, the reaction product corresponds to DPA chemically functionalized BP sheets having an imino-phosphorane (IP) structure. The electrochemical oxidation of BP sheets chemically functionalized with DPA in the presence of PTA leads to an increase in the weight of P-N bonds as a consequence of the generation of PDPA doped with the PTA heteropolyanions, as shown by FTIR spectroscopy and Raman scattering. This process is evidenced by a shift of the Raman line from 362 cm-1 to 378 cm-1, assigned to the A1g mode. This change was explained by taking into account the compression of the layers containing P atoms, which is induced by PDPA macromolecular chains. The decrease in the intensity of the PL spectra of DPA as well as PDPA, in the presence of BP, indicates that BP acts as a PL quenching agent for these compounds. A preferential orientation of the PDPA doped with the PTA heteropolyanions on the surface of BP sheets is highlighted by the variation of the binding angle of the PDPA on the surface of BP sheets from 44.7° to 39.9°.

A simple and safe approach for simultaneous spectrophotometric determination of nitroglycerin and nitrocellulose in double base solid propellants.

An accurate, simple and safe method was developed for simultaneous determination of nitroglycerine (NG) and nitrocellulose (NC) in double base solid propellants (DB propellants). The proposed method is based on alkaline hydrolysis of NG and NC, and followed by colored reaction of released nitrite ion with p-nitroaniline in the presence of diphenylamine in acidic media and produce azo dye. The absorbance of the azo dye was measured at 534nm. Two sets of reaction conditions were developed. In the first set, at room temperature, only NG was hydrolyzed and calibration curve obtained. In the second set, at 60℃, NG and NC were hydrolyzed simultaneously. Based on obtained amount for the NG at room temperature, and total amount of NG and NC at 60℃, the amount of NC was determined by using stoichiometric equations. The calibration curve was linear over the concentration ranges of 0.2-5.0, 0.5-10μgmL-1 for NG and NC, respectively. The proposed method was successfully applied for the determination of NG and NC in DB propellants with good recoveries ranged from 99 to 101%, and RSD less than 2.0%. The method statistically compared based on t- and F-tests with those obtained in according to military standard method (MIL-STD-286). The results showed that the proposed method offers an accuracy and reliable approach for the determination of these compounds in DB propellants, and can be suggested as a routine method in military quality control laboratories.

Carotenoids Do Not Protect Bacteriochlorophylls in Isolated Light-Harvesting LH2 Complexes of Photosynthetic Bacteria from Destructive Interactions with Singlet Oxygen.

The effect of singlet oxygen on light-harvesting (LH) complexes has been studied for a number of sulfur (S+) and nonsulfur (S−) photosynthetic bacteria. The visible/near-IR absorption spectra of the standard LH2 complexes (B800-850) of Allochromatium (Alc.) vinosum (S+), Rhodobacter (Rba.) sphaeroides (S−), Rhodoblastus (Rbl.) acidophilus (S−), and Rhodopseudomonas (Rps.) palustris (S−), two types LH2/LH3 (B800-850 and B800-830) of Thiorhodospira (T.) sibirica (S+), and an unusual LH2 complex (B800-827) of Marichromatium (Mch.) purpuratum (S+) or the LH1 complex from Rhodospirillum (Rsp.) rubrum (S−) were measured in aqueous buffer suspensions in the presence of singlet oxygen generated by the illumination of the dye Rose Bengal (RB). The content of carotenoids in the samples was determined using HPLC analysis. The LH2 complex of Alc. vinosum and T. sibirica with a reduced content of carotenoids was obtained from cells grown in the presence of diphenylamine (DPA), and LH complexes were obtained from the carotenoidless mutant of Rba. sphaeroides R26.1 and Rps. rubrum G9. We found that LH2 complexes containing a complete set of carotenoids were quite resistant to the destructive action of singlet oxygen in the case of Rba. sphaeroides and Mch. purpuratum. Complexes of other bacteria were much less stable, which can be judged by a strong irreversible decrease in the bacteriochlorophyll (BChl) absorption bands (at 850 or 830 nm, respectively) for sulfur bacteria and absorption bands (at 850 and 800 nm) for nonsulfur bacteria. Simultaneously, we observe the appearance of the oxidized product 3-acetyl-chlorophyll (AcChl) absorbing near 700 nm. Moreover, a decrease in the amount of carotenoids enhanced the spectral stability to the action of singlet oxygen of the LH2 and LH3 complexes from sulfur bacteria and kept it at the same level as in the control samples for carotenoidless mutants of nonsulfur bacteria. These results are discussed in terms of the current hypothesis on the protective functions of carotenoids in bacterial photosynthesis. We suggest that the ability of carotenoids to quench singlet oxygen (well-established in vitro) is not well realized in photosynthetic bacteria. We compared the oxidation of BChl850 in LH2 complexes of sulfur bacteria under the action of singlet oxygen (in the presence of 50 μM RB) or blue light absorbed by carotenoids. These processes are very similar: {[BChl + (RB or carotenoid) + light] + O2} → AcChl. We speculate that carotenoids are capable of generating singlet oxygen when illuminated. The mechanism of this process is not yet clear.

Solvent dependence of photophysical and photochemical behaviors of thioxanthen-9-one

The photophysical and photochemical behaviors of thioxanthen-9-one (TX) in different solvents have been studied using nanosecond transient absorption spectroscopy. A unique absorption of the triplet state 3TX* is observed, which involves two components, 3nπ* and 3ππ* states. The 3ππ* component contributes more to the 3TX* when increasing the solvent polarity. The self-quenching rate constant ksq of 3TX* is decreased in the order of CH3CN, CH3CN/CH3OH (1:1), and CH3CN/H2O (1:1), which might be caused by the exciplex formed from hydrogen bond interaction. In the presence of diphenylamine (DPA), the quenching of 3TX* happens efficiently via electron transfer, producing the TX·− anion and DPA·+ cation radicals. Because of insignificant solvent effects on the electron transfer, the electron affinity of the 3nπ* state is proved to be approximately equal to that of the 3ππ* state. However, a solvent dependence is found in the dynamic decay of TX·– anion radical. In the strongly acid aqueous acetonitrile (pH=3.0), a dynamic equilibrium between protonated and unprotonated TX is definitely observed. Once photolysis, 3TXH+* is produced, which contributes to the new band at 520 nm.

Nitroxide-mediated polymerization of 1,3-butadiene in the presence of diphenylamine with hydrogen peroxide as initiator

Living behavior of a nitroxide-mediated polymerization of 1,3-butadiene in the presence of diphenyl nitroxide (DPN) as counter radical and hydrogen peroxide (H2O2) as initiator has been studied to elucidate the bimodal molar mass distribution of the product by four approaches such as hydrolyzation of the oligomeric product, peak separation technique, which defines the oligobutadiene molar mass dependency in relation to α as a ratio of [nitroxide] to [H2O2], variation of hydroxyl value with respect to α, and para-substituted DPN. It is demonstrated that the synthesized DPN shows efficient control of the polymerization of 1,3-butadiene, but because of the formation of difunctional nitroxide during the oxidation process of aromatic diphenylamine, a bimodal distribution in the final product is observed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Effective indirect enrichment and determination of nitrite ion in water and biological samples using ionic liquid-dispersive liquid–liquid microextraction combined with high-performance liquid chromatography

An ionic liquid dispersive liquid–liquid microextraction high-performance liquid chromatography (IL-DLLME-HPLC) method for effective enrichment and determination of nitrite ion in water and biological samples was developed. The method was based on the reaction of nitrite ion with p-nitroaniline in the presence of diphenylamine in acid media and IL-DLLME of azo product. The optimization of reaction and extraction conditions, such as kind and concentration of acid, reaction time, volume of reaction solvent, temperature, kind of extraction and dispersive solvent, volume of extraction and dispersive solvent, addition of salt, extraction and centrifugal time were studied. Under the optimal conditions, 1-octyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide IL-DLLME procedure provided high enrichment factor of 430 and good extraction recovery of 91.7% for nitrite ion. The linearity was observed in the range of 0.4–500.0 μg L −1 with good correlation coefficient ( r 2 = 0.9996). The relative standard deviations (RSDs) for five replicate measurements varied between 1.5% and 4.8%. The limit of detection of the method (S/N = 3) was 0.05 μg L −1. The interference effect of some anions and cations was also tested. The developed method allowed achieving an excellent enrichment factor, yielding a lower LOD in comparison with other methods. Moreover, the proposed method was able to analyze nitrite ion in water and biological samples with satisfactory recovery ranged from 96.5% to 107.3%.

Identification and the developmental formation of carotenoid pigments in the yellow/orange Bacillus spore-formers

Spore-forming Bacillus species capable of synthesising carotenoid pigments have recently been isolated. To date the detailed characterisation of these carotenoids and their formation has not been described. In the present article biochemical analysis on the carotenoids responsible for the yellow/orange pigmentation present in Bacilli has been carried out and the identity of the carotenoids present was elucidated. Chromatographic, UV/Vis and Mass Spectral (MS) data have revealed the exclusive presence of a C 30 carotenoid biosynthetic pathway in Bacillus species. Apophytoene was detected representing the first genuine carotenoid formed by this pathway. Cultivation in the presence of diphenylamine (DPA), a known inhibitor of pathway desaturation resulted in the accumulation of apophytoene along with other intermediates of desaturation (e.g. apophytofluene and apo-ζ-carotene). The most abundant carotenoids present in the Bacillus species were oxygenated derivatives of apolycopene, which have either undergone glycosylation and/or esterification. The presence of fatty acid moieties (C 9 to C 15) attached to the sugar residue via an ester linkage was revealed by saponification and MS/MS analysis. In source fragmentation showed the presence of a hexose sugar associated with apolycopene derivatives. The most abundant apocarotenoids determined were glycosyl-apolycopene and glycosyl-4′-methyl-apolycopenoate esters. Analysis of these carotenoids over the developmental formation of spores revealed that 5-glycosyl-4′-methyl-apolycopenoate was related to sporulation. Potential biosynthetic pathways for the formation of these apocarotenoids in vegetative cells and spores have been reconstructed from intermediates and end-products were elucidated.

Über die mit titanchlorid-triäthylaluminium katalysator initiierte propylenvinylchlorid copolymerisation

The copolymerization of propylene and vinylchloride with a TiCl3–Et3Al system is possible in the presence of polar complex-forming additives. The presence of diphenylamine is nessesary but not enough to complete the reaction. If the complex-forming ether-amine mixture has a high mole ratio, the composition of the copolymer can be changed only in a small range. But when the ether-amine mole ratio is low, one can change composition of the copolymer at will. The presence of the complex-forming additives increase the conversion considerably. It is very important that the vinyl chloride be neat. If the vinyl chloride is contaminated with other chlorinated hydrocarbons, the reaction does not take place. If the vinyl chloride has a small acetylene content, it does not disturbe the copolymerization. Several properties of the copolymers change proportional to the composition. The copolymers have lower heat stability than the homopolymers.

Influence of halide ions on the adsorption of diphenylamine on iron in 0.5 M H 2SO 4 solutions

Halide ions are found to enhance the inhibition performance of amines due to enhanced adsorption of amines by the adsorbed halide ions on the metal surface. In this work, the synergistic action of halide ions on the corrosion inhibition of iron in 0.5 M H 2SO 4 by diphenylamine has been found out by electrochemical impedance and polarization methods. Analysis of impedance data has been made with equivalent circuit with constant phase angle element for calculation of double layer capacitance values. Experiments have been carried out in the concentration range of 100–1000 ppm of diphenylamine in the presence of 0.5–1.0 × 10 −3 M of halide ions. Diphenylamine is found to be a cathodic inhibitor and the inhibition efficiency of about 65% is obtained at 1000 ppm. The anodic and cathodic Tafel slopes in the presence of diphenylamine alone and with halide ions are 65 ± 5 and 105 ± 5 mV, respectively. Diphenylamine inhibits corrosion by adsorption and the surface coverage values are increased considerably in the presence of halide ions. In the presence of iodide ions, the inhibition efficiency of diphenylamine at 100 ppm is increased to more than 90%. In the case of other halide ions, the inhibition efficiency of diphenylamine in increased to 80% at 1000 ppm. The order of synergism of halide ions is I − ≫ Br − > Cl −. The highest synergistic effect of iodide ions is due to chemisorption with metal surface due to its larger size and ease of polarizability.

Micell-mediated extraction for the spectrophotometric determination of nitrite in water and biological samples based on its reaction with p-nitroaniline in the presence of diphenylamine

A cloud point extraction process using the nonionic surfactant Triton X-100 to extract nitrite from aqueous solution was investigated. The method is based on the color reaction of nitrite with p-nitroaniline in the presence of diphenylamine in acid media and micell-mediated extraction of an azo product. The optimal extraction and reaction conditions (e.g., acid concentration, reagent concentration, effect of time) were studied, and the analytical characteristics of the method (e.g., limit of detection, linear range, molar absorptivity, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 2–40 ng ml −1 of nitrite ion. The detection limit of the method is 0.87 ng ml −1 of nitrite ion. The interference effect of some anions and cations was also tested. The method was applied to the determination of nitrite in tap water, waste water, and human urine samples.

Spectrophotometric Determination of Nitrite Based on Its Reaction with p-Nitroaniline in the Presence of Diphenylamine in Micellar Media

In the present work a very simple, sensitive and selective spectrophotometric method for the determination of nitrite in micellar media is described. The method is based on the color reaction of nitrite with p-nitroaniline in the presence of diphenylamine in acid media. In order to remove the extraction step, Triton X-100, a non-ionic surfactant was used as micellar media. The optimum reaction conditions such as acid concentration, reagents concentration and effect of time have been studied and the analytical characteristics of the method such as limit of detection, linear range and molar absorptivity have been obtained. The interference of some anions and cations was also tested. The method was applied to the determination of nitrite in real samples.

3-Hydroxy-2-(2' -thienyl)-4H-chromen-4-one as an analytical reagent for the trace determination of cerium

A simple and rapid method for the direct spectrophotometric determination of trace amounts of cerium(III) has been worked out using 3-hydroxy-2-(2'-thienyl)-4H-chromen-4-one (HTC) as a complexing agent in presence of diphenylamine with λ m a x at 430 nm. Several analytically important ions do not cause interference in the procedure. The method has good reproducibility and can be satisfactorily applied for the analysis of cerium containing samples.

Adsorption behaviour of some aromatic amines on pyrolusite and activated carbon and recovery of beta napthylamine from water sample.

The adsorption behaviour of Diphenylamine (DPAM), beta napthylamine (beta NAM), alpha napthylamine (alpha NAM) and aniline on pyrolusite and activated carbon has been studied. Pyrolusite shows remarkable sorption capacity for DPAM and beta NAM as compared to aniline; (the adsorption followed the order: Activated Carbon:--> DPAM = beta NAM > alpha Aniline; Pyrolusite: DPAM: --> beta NAM > alpha NAM > Aniline) The maximum adsorption of beta NAM occurred in the concentration range 4-20 microg mL(-1) on pyrolusite (95%) and 4-50 microg mL(-1) on activated carbon (100%). The effect of various doses of activated carbon on the adsorption of beta NAM confirm Langmuir and Freundlich isotherms where as Freundlich isotherm is obeyed by pyrolusite. The adsorption of beta NAM on both the absorbents is not affected in presence of DPAM over a wide range of their initial concentrations (20-60 microg mL(-1)). The desorption studies of beta NAM on pyrolusite was carried out by batch as well as column processes. Excellent results were obtained when a mixture of n-hexane and isopropanol (91:1) was used as eluent.

Effect of diphenylamine on photodissociation of aryl azides

The charge-transfer complexes of aromatic azides with diphenylamine (DPA) were studied. Irradiation of 4-nitrophenyl azide in the presence of DPA was found not to give rise to the dissociation of the azido group in the azide radical anionvia intracomplex electron transfer. The photodissociation slows down due to both the static (the formation of a photostable complex with diphenylamine) and dynamic quenching. When 4-azidoacetophenone is irradiated in the presence of DPA, the amine-sensitized decomposition of azide and the photodecomposition of the azide—DPA complex occur along with the direct photolysis of azide, which results in acceleration of the photodissociation due to an increase in the efficiency of the light absorption by the reaction system. A possible sensitization of photodecomposition of aromatic azidesvia an electron transfer mechanism by irradiation of the azide-donor complex is shown.

Generation of N-tert-butyl-α-phenylnitrone radical adducts in iron breakdown of tert-butyl-hydroperoxide

ESR spectroscopy coupled to the spin trapping technique was used to evaluate the generation of radical species arising from the ferrous ion induced decomposition of tert-butyl hydroperoxide (’BuOOH) in methylene chloride. We report here that N-tert-butyl-α-phenylinitrone (PBN) can trap peroxyl radicals generated in the ferrous ion induced breakdown of high concentration of ’BuOOH (IM) at room temperature, the radical adduct being stable under the light. The peroxyl radical formation was demonstrated by direct ESR measurements at 77K. In contrast, alkoxyl and methyl radicals were trapped only in the presence of low hydroperoxide concentration (ImM). In order to measure the hyperfine splitting constants (hfsc) of the PBN-methyl adduct spectra were obtained in the presence of diphenylamine (DPA) or 2,6-di-tert-butyl-4-methylphenol (BHT), which quenched the alkoxyl radical. For this latter radical, the hfsc were calculated by computer simulation. A mechanism for a direct interaction between DPA and the alkoxyl radical is presented. DPA quenched the peroxyl radical in the reaction of high hydroperoxide concentrations, with the concomitant generation of a DPA nitrogen-based radical.

Roles of bacteriochlorophyll and carotenoid synthesis in formation of intracytoplasmic membrane systems and pigment-protein complexes in an aerobic photosynthetic bacterium, Erythrobacter sp. strain OCh114.

Synthesis of bacteriochlorophyll and carotenoids was inhibited in an aerobic photosynthetic bacterium, Erythrobacter sp. strain OCh114, by alpha, alpha'-dipyridyl and diphenylamine. Formation of two pigment-protein complexes, reaction center-B870 (RC-B870) and B806, and development of the intracytoplasmic membranes of the cells were studied by spectral analysis and electron microscopy. Inhibition of bacteriochlorophyll synthesis by alpha, alpha'-dipyridyl, which was accompanied by a decrease in carotenoid synthesis, suppressed formation of intracytoplasmic membranes in the cells. Growth under illumination had a similar effect on formation of pigments and membranes. On the other hand, inhibition of carotenoid synthesis by diphenylamine did not suppress either development of the membrane system or bacteriochlorophyll synthesis. Formation of RC-B870 and B806 complexes, however, was differentially affected by blockage of carotenoid synthesis. In the presence of diphenylamine, the B806 complex was formed in a much smaller amount than the RC-B870 complex. These results suggest that, in Erythrobacter sp. strain OCh114, bacteriochlorophyll plays an essential role in intracytoplasmic membrane development, and carotenoids are important for assembly of pigment-protein complexes.

Decreased lipopolysaccharide Content and Enhanced Susceptibility of Leptospiras to Serum Leptospiricidal Action and Phagocytosis After Treatment with Diphenylamine

Growth of leptospiras in the presence of diphenylamine (DPA) caused a decrease in the content of leptospiral lipopolysaccharide (LPS). In association with this decrease of LPS, leptospiras became susceptible to anti-leptospiral action of normal rabbit serum (NRS), leptospiricidal action of antibody and complement, and killing by phagocytes. DPA-treated leptospiras were eliminated rapidly from the blood of infected mice and could not grow in the animals.

Crystal structure of 2-tert-butyldiphenylamine

During UV irradiation of benzoquinones and diphenoquinones in the presence of diphenylamine (DPA) or its tert-butyl deriatives there is a photoreduction of the carbonyl group. As a result of transfer of an H atom there are formed neutral radicals, stable under low-temperature photolysis, which join into radical pairs of various types [i, 2], the structure of which is assumed to be identical with the structure of the corresponding molecular complexes. Conclusions on the structure of the radicals and supposed complexes are based purely on ESR, and there are no x-ray structural data for these complexes and their donor components tertbutyl-substituted DPA. We have therefore made an x-ray structural investigation of 2-tertbutyldiphenylamine (I).

The effect of diphenylamine on carotenogenesis in Phycomyces blakesleeanus

Abstract The presence of diphenylamine (DPA) during growth of mutant strains of Phycomyces blakesleeanus caused the expected inhibition of the formation of unsaturated carotenes, and the accumulation of phytoene in all cases. Cell extracts from DPA-grown cultures incubated with [2- 14 C]mevalonic acid, also exhibited these effects. Inhibition of in vitro carotenogenesis was similarly shown by extracts from normally-grown mycelia, incubated with DPA. Removal of DPA from mycelia or from cell extracts, resulted in the formation of unsaturated carotenes. The ratio of 15- cis -all- trans -phytoenes from mycelia grown ± DPA was only marginally altered, but, in vitro , the presence of DPA caused a significant increase in the formation of the all- trans isomer in the C5 strain. These results indicate that DPA acts by post-translational regulation of enzymic activities.