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Oxygenated cytochrome o(s) from Vitreoscilla was photodissociated by a laser flash but the quantum yield was low. The rebinding of oxygen to the ferrous cytochrome proceeded monophasically, and the second order rate constant was 7.8 X 10(7) M-1 s-1, the off rate constant 5.6 X 10(3) s-1, and the calculated dissociation constant for the oxygenated compound 7.2 X 10(-5) M at pH 7.3 and 25 degrees C. Rapid scanning spectroscopy revealed the formation of chytochrome o-O2 directly from ferrous chytochrome o and oxygen without any evidence for an intermediary formation of Compound D, another type of oxygenated chytochrome o. Photodissociation in solution containing CO/O2 mixtures resulted in rapid binding of oxygen followed by slow replacement by CO. This property as well as the photodissociability of chytochrome o-O2 suggests that the heme iron of the compound is in the ferrous state. In addition, the primary oxygen compound was fairly stable and did not decay further in the absence of CO, in marked contrast with that of mammalian cytochrome oxidase primary oxygen compound which rapidly decayed. This result suggests a possible role of this cytochrome as an oxygen carrier or storage.
Three diesel fuels, one oil sand-derived (OSD) diesel serving as base fuel, one cetane-enhanced base fuel, and one oxygenate [diethylene glycol dimethyl ether (DEDM)]-blended base fuel, were tested for their emission characterizations in vehicle exhaust on a light-duty diesel truck that reflects the engine technology of the 1994 North American standard. Both the cetane-enhanced and the oxygenate-blended fuels were able to reduce regulated [CO, particulate matter (PM), total hydrocarbon (THC)] and nonregulated [polyaromatic hydrocarbons (PAHs), carbonyls, and other volatile organic chemicals] emissions, except for nitrogen oxides (NO(x)), compared with the base fuel. Although burning a fuel that contains oxygen could conceivably yield more oxygenated compounds in emissions, the oxygenate-blended diesel fuel resulted in reduced emissions of formaldehyde along with hydrocarbons such as benzene, 1,3-butadiene, and PAHs. Reductions in nitro-PAH emissions have been observed in both the cetane-enhanced and oxygenated fuels. This further demonstrates the benefits of using a cetane enhancer and the oxygenated fuel component.
Tissue oxygenation is one of the key dosimetric factors involved in the application of photodynamic therapy (PDT). However, quantitative studies of oxygenation levels at and surrounding the treatment site have been lacking both before, during and after treatment. With the recent development of sensitive, non-invasive, optical spectroscopic techniques based on oxygen-dependent phosphorescence quenching of probe compounds, oxygenation levels can now be measured quantitatively at selected sites with spatial resolution on the millimeter scale. We present results using the phosphorescent compound, palladium meso-tetra(carboxyphenyl)porphine, for measurement of in vivo microvascular oxygen tensions in rat liver during PDT. Time-resolved phosphorescence detection was carried out using fibre-optic sensoring, and oxygen tensions were determined from the phosphorescence lifetimes using Stern-Volmer analysis. During PDT treatment using 5-aminolaevulinic (ALA) acid-induced protoporphyrin IX (PPIX) with a 50 mg/kg ALA dose, oxygen levels near the irradiation fibre placed on the surface of the liver showed a significant decrease by a factor of ten from 20 to 2 torr after an energy dose of 60 J using 100 mW at 635 nm. Areas farther from the treatment site which were exposed to lower light doses exhibited lower reductions in oxygen levels. This spectroscopic technique is a highly sensitive means of investigating tissue oxygenation during and after treatment, and should help not only to advance the understanding of hypoxia and microvascular damage in the PDT mechanism but also contribute to improving the dosimetry of PDT.
Phagocytic leukocytes generate large amounts of reactive oxygen compounds during and after phagocytosis of micro-organisms. These compounds are essential for the killing of a wide variety of microbes. The enzyme responsible for this process is NADPH:O2 oxidoreductase (NADPH oxidase), which utilizes the reduction equivalents of NADPH to reduce atmospheric oxygen to superoxide (O2-.). Subsequently, superoxide is converted by the leukocytes to other reactive compounds, such as hydrogen peroxide (H2O2), hypochlorous acid (HOCl) and N-chloramines (RNCl). Each of these compounds has potent microbicidal properties. Under resting, non-phagocytizing conditions, phagocytes do not produce reactive oxygen compounds. However, within 15-30 sec after binding of micro-organisms to cell surface receptors, superoxide generation starts. This phenomenon is called the respiratory burst. This phenomenon is called the respiratory burst. The activation of the NADPH oxidase is caused by the assembly of components of this enzyme into an active complex. Under resting conditions, at least three components reside in the cytoplasm and at least two are located in the plasma membrane. Activation of the NADPH oxidase results in translocation of cytosolic components to the plasma membrane and formation of an active enzymatic complex in the plasma membrane.
The kinetics of dissociation and reassociation of the oxygenated species of Escherichia coli flavohaemoglobin (Hmp) were studied using stopped-flow rapid-scan and flash photolysis spectrophotometry at 25 degrees C. The oxygenated compound(s) form rapidly on mixing oxygen with the NADH-reduced flavohaemoglobin. On exhaustion of NADH, with residual oxygen, decay occurs in two phases to give a form in which haem b and flavin are oxidized. Spectral changes during this process suggest a direct release of O2- from the oxy form. Photodissociation of the oxygenated species generates the unliganded protein, which recombines with oxygen to give two spectrally and kinetically distinct forms. The reversibility of the oxygen reaction and the rapid reassociation kinetics after photodissociation confirm the haemoglobin-like features of this protein.
Density functional theory is employed to determine the reaction thermodynamics of a group of chemical and electrochemical reactions chosen to investigate the dissolution of metal atoms from oxygen reduction reaction catalysts in an acid medium. Once a set of thermodynamically allowed reactions is established, those reactions are selected to investigate the relative stabilities of Pt atoms and of other transition metal atoms (Ir, Pd, Rh, Ni, and Co) toward the dissolution reactions. The dissolution reactions that are found thermodynamically favorable are electrochemical and involve adsorbed oxygenated compounds that are intermediate species of the oxygen reduction reaction. Iridium is found to be the most stable among the various pure metals in comparison to Pt. Most of the metals alloyed with Pt cause a decrease of the Pt stability against dissolution, except for Ni, which does not affect it. On the other hand, the influence of Pt on the stability of the second metal in the alloy follows the same trend as in pure metal catalysts, with Ir being the most stable. When both atoms in a PtM alloy are involved in dissolution reactions, alloyed Ir is also found more stable than Pt in a given dissolution reaction, and the same behavior is found in alloyed Co for most of the reactions studied.
The residual fractions remaining after microbial degradation of diesel fuel, different deparaffinized raffinates and extracts from long-term contaminated soils were analyzed by liquid chromatography, gas chromatography, infrared spectrometry and mass spectrometry. The quantity of saturated hydrocarbons decreased after the microbial treatment, whereas the portion of polar compounds increased. The total content of aromatics changed only insignificantly. n-Paraffins < C26 were found to be no longer present in mineral oils degraded to exhaustion. Infrared spectrometry revealed oxygen compounds in the residues, mainly ketones, fatty acids and esters. Elementary analysis confirms the presence of nitrogen, oxygen and sulphur compounds in the degraded products. The gas chromatograms of high boiling oils, as well as of residues and extracts, consist mainly of a large base "envelope" (about 95% of the total area); thus gc/ms coupling reaches the limits of its applicability. However, mass spectrometry with direct inlet gives valuable information regarding hydrocarbon type analysis. The results revealed the preferable degradation of alkanes, 1-ring aliphatics and benzenes and an enrichment of condensed cycloaliphatics and aromatics. The latter compounds are known to be resistant to microbial attack.
Quantification and transformation of organic compounds are pivotal in understanding atmospheric processes, because such compounds contribute to the oxidative capacity of the atmosphere and drive climate change. It has recently been recognized that chemical reactions in snow play a role in the production or destruction of photolabile volatile organic compounds (VOC). We present an environmentally friendly method for determination of VOC and semi-VOC in snow collected at three sites-remote, urban, and (sub-)arctic. A solid-phase micro-extraction (SPME) procedure was developed and (semi-)VOC were identified by gas chromatography with mass spectrometric detection (GC-MS). A broad spectrum of (semi-)VOC was found in snow samples, including aldehydes, and aromatic and halogenated compounds. Quantification was performed for 12 aromatic and/or oxygenated compounds frequently observed in snow by use of neat standard solutions. The concentrations detected were between 0.12 (styrene and ethylbenzene) and 316 microg L(-1) (toluene) and limits of detection varied between 0.11 (styrene) and 1.93 microg L(-1) (benzaldehyde). These results indicate that the SPME technique presented is a broad but selective, versatile, solvent-free, ecological, economical, and facile method of analysis for (semi-)VOC in natural snow samples.
Curcumin, the yellow color pigment of turmeric, is produced industrially from turmeric oleoresin. The mother liquor after isolation of curcumin from oleoresin contains approximately 40% oil. The oil was extracted from the mother liquor using hexane at 60 degrees C, and the hexane extract was separated into three fractions using silica gel column chromatography. These fractions were tested for antibacterial activity by pour plate method against Bacillus cereus, Bacillus coagulans, Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Fraction II eluted with 5% ethyl acetate in hexane was found to be most active fraction. The turmeric oil, fraction I, and fraction II were analyzed by GC and GC-MS. ar-Turmerone, turmerone, and curlone were found to be the major compounds present in these fractions along with other oxygenated compounds.
Adsorption of NO and coadsorption of NO and O2 on H-ZSM-5 have been studied at low and room temperature by means of FTIR spectroscopy. For better interpretation of the spectra, experiments involving isotopic labeled molecules have been performed. Low temperature adsorption of NO on H-ZSM-5 results initially in formation of NO which is H-bonded to the zeolite acidic hydroxyls. A second NO molecule is inserted into the OH-NO species at higher coverages, thus forming OH(NO)2 complexes. Different kinds of NO dimers are also formed. Negligible amounts of oxygenated compounds have been detected. In the presence of oxygen, the (di)nitrosyl species are oxidized very fast even at 100 K to N2O3, NO+, NO2, and N2O4. Different kinds of adsorbed N2O3 species have been evidenced. With increasing temperature, NO+ migrates and occupies cationic positions. The latter species interacts with NO at low temperature to give an [ONNO]+ complex. This reaction is used to prove that the different bands in the 2206-2180 cm(-1) region are also due to NO+ species.
Curcumin, the yellow coloring pigment of turmeric is produced industrially from turmeric oleoresin. The mother liquor after isolation of curcumin from oleoresin known as curcumin removed turmeric oleoresin (CRTO) was extracted three times with n-hexane at room temperature for 30 min to obtain turmeric oil. The turmeric oil was subjected to fractional distillation under vacuum to get two fractions. These fractions were tested for antifugal activity against Aspergillus flavus, A. parasiticus, Fusarium moniliforme and Penicillium digitatum by spore germination method. Fraction II was found to be more active. The chemical constituents of turmeric oil, fraction I and fraction II were determined by GC and identified by GC-MS. Aromatic turmerone, turmerone and curlone were major compounds present in fraction II along with other oxygenated compounds.
Volatile oil was extracted from Cuminum cyminum L. by using steam distillation. More than sixty peaks were separated and 49 compounds were identified by gas chromatography-mass spectrometry (GC-MS). The relative amounts of the components were determined by area normalization method. Among the 49 compounds identified, there were 16 hydrocarbons and 32 oxygenated compounds. The main compnents were cuminal and safranal (accounting for 32.26% and 24.46% respectively in the components identified). The other nine compounds with contents all over 1%, were monterpenes, sesquiterpenes, aromatic aldehydes and aromatic oxides etc. The other components with relatively small amounts were chiefly terpenes, terpenols, terpenals, terpenones, terpene esters and aromatic compounds. It is good to separate polar and apolar components in the volatile oil from Cuminum cyminum L. on the GC capillary column of moderate polarity.
The cosolvent-induced dissolution of polynuclear aromatic hydrocarbons (PAHs) from contaminated soil caused by oxygenated fuel spills was studied. Oxygenated fuel induces a solvent flushing effect on the contaminated soil due to the high content of oxygenated compounds (i.e., methanol, ethanol, and methyl tert butyl ether (MTBE)). The miscible displacement techniques were applied to evaluate the increased potential for secondary contamination in an impacted site. Significant solubility enhancement of the 18 PAHs monitored during fuel spill simulation and cosolvent flushing is clearly evident when compared to normal water dissolution. The breakthrough concentration profile for each PAH constituent was integrated over the cumulative effluent volume (i.e., the zeroth moment) to determine the total PAH mass removed during the experiment. The removal efficiency of PAHs ranges from 46.6% to 99.9% in three oxygenated fuels (i.e., M85, E85, and oxygenated gasoline) during the fuel spill. Several factors including hydrophobicity of compounds, nonequilibrium dissolution due to nonuniform coal tar distribution, and heterogeneous media properties affect the oxygenated compound-induced dissolution process. This study provides a basis to predict the facilitated transport of hydrophobic organic compounds from subsurface environment due to the cosolvent effects of oxygenated fuels.
The evolution of semivolatile and volatile compounds in the combustion of polyethylene (PE) was studied at different operating conditions in a horizontal quartz reactor. Four combustion runs at 500 and 850 degrees C with two different sample mass/air flow ratios and two pyrolytic runs at the same temperatures were carried out. Thermal behavior of different compounds was analyzed and the data obtained were compared with those of literature. It was observed that alpha,omega-olefins, alpha-olefins and n-paraffins were formed from the pyrolytic decomposition at low temperatures. On the other hand, oxygenated compounds such as aldehydes were also formed in the presence of oxygen. High yields were obtained of carbon oxides and light hydrocarbons, too. At high temperatures, the formation of polycyclic aromatic hydrocarbons (PAHs) took place. These compounds are harmful and their presence in the combustion processes is related with the evolution of pyrolytic puffs inside the combustion chamber with a poor mixture of semivolatile compounds evolved with oxygen. Altogether, the yields of more than 200 compounds were determined. The collection of the semivolatile compounds was carried out with XAD-2 adsorbent and were analyzed by GC-MS, whereas volatile compounds and gases were collected in a Tedlar bag and analyzed by GC with thermal conductivity and flame ionization detectors.
Free oxygen radicals are highly active oxygen compounds contributing to several pathological states. A possible source of free oxygen radicals during reversible ischemic heart disease and mechanisms of their toxicity to the myocardium are discussed. Despite controversial results of clinical trials with the use of antioxidants in reducing an area of necrosis in the experimental myocardial infarction, it seems that free oxygen radicals play an important role in ischemic-reperfusion heart disease. Some promising results with the use of antioxidants (significant decrease in dyskinesis of ischemic left ventricular muscle and reduction of cardiac arrhythmias incidence) may be of clinical importance.