An infrared study of the carbon monoxide complexes of cytochrome P-450 and cytochrome P-420

The infrared stretch vibrations (upsilonCO) of the CO-complexes of cytochrome P-450 and cytochrome P-420 have been determined from infrared difference spectra. The CO-complexes exhibit IR-bands at 1949 cm-1 and 1966 cm-1 with half widths of approximately 17 cm-1 and approximately 20 cm-1 respectively. These results are compared with the CO-stretch frequencies of other haemoproteins and discussed with respect to specific interactions of the CO-ligand with the protein moiety and to the ligand trans to CO of the cytochromes.     

Kinetics of manganese ore reduction by carbon monoxide

A step has been made in the direction of understanding the fundamental chemical processes taking place inside electric are furnaces producing manganese alloys. The reduction of higher manganese oxides to MnO by carbon monoxide has been studied in the temperature range 700 °C to 1100 °C. A topochemical pattern with a single shrinking core inside the ore particles has been observed in most cases. It has been found that the reduction of some manganese silicates (braunite minerals) is influenced by reaction interface kinetics, whereas the reduction rate of manganese oxides (bixbyite and hausmannite) is mostly determined by product shell pore diffusion. Sintering kinetics and the extent of natural porosity determine the product shell pore diffusivity. As the melting point of the reaction product is approached, rapid sintering leads to a decrease in diffusivity.     

Oxytocin release is inhibited by the generation of carbon monoxide from the rat hypothalamus--further evidence for carbon monoxide as a neuromodulator

Recent evidence suggests that the gas nitric oxide can modulate the secretion of a number of hypothalamic hormones, and may be co-localized particularly to oxytocin-containing neurons. Another gas, carbon monoxide (CO), has also been suggested to play a role in neural signaling in the brain, and the synthetic enzyme responsible for the generation of carbon monoxide has been reported to be present in the rat hypothalamus. In this study, we have therefore investigated whether CO has the ability to modify the release of oxytocin from acute rat hypothalamic explants. Hemin, a specific CO precursor through the enzyme heme oxygenase (the enzymatic pathway synthesizing endogenous CO, was found to inhibit KCl-stimulated oxytocin release, with a maximal effect at 10(-5) M, while showing no effect on basal oxytocin secretion. The stimulation of oxytocin by serotonin 10 ng/ml was also significantly antagonized by hemin 10(-7) M. An inhibitor of heme oxygenase, zinc-protoporphyrin-9, had no effect on basal or stimulated oxytocin release. When hemin and zinc-protoporphyrin-9 were given together, the hemin-induced inhibition of oxytocin was completely antagonized by the enzyme inhibitor. Ferrous hemoglobin A0, a substance known to bind CO with high affinity, had no effect on either basal or stimulated oxytocin release, but when hemin and ferrous hemoglobin A0 were given together the hemin-induced inhibition of oxytocin was completely blocked. These findings provide evidence that endogenous CO may play a role in the control of oxytocin release and that, by analogy with nitric oxide, CO may represent a major new neuroendocrine modulator.     

用"CO2-木炭两段炉"制备高纯CO气体

介绍一种制备高纯CO气体方法。其原理是CO2在高温下与木炭反应,再经净化得到CO气体。产气过程中两个还原炉前后串联,具有产气稳定,气量可调,设备简单,CO纯度高等特点。     

Mechanism of carbon monoxide oxidation by the carbon monoxide dehydrogenase/acetyl-CoA synthase from Clostridium thermoaceticum: kinetic characterization of the intermediates

Carbon monoxide dehydrogenase/acetyl-CoA synthase (CODH/ACS) from Clostridium thermoaceticum catalyzes (i) the synthesis of acetyl-CoA from a methylated corrinoid protein, CO, and coenzyme A and (ii) the oxidation of CO to CO2. CO oxidation occurs at a Ni- and FeS-containing center known as cluster C. Electrons are transferred from cluster C to a separate metal center, cluster B, to external acceptors like ferredoxin. In the work described here, we performed reductive titrations of CODH/ACS with CO and sodium dithionite and monitored the reaction by electron paramagnetic resonance (EPR) spectroscopy. We also performed pre-steady-state kinetic studies by rapid freeze-quench EPR spectroscopy (FQ-EPR) and stopped-flow kinetics. Redox titrations of CODH/ACS revealed the existence of a UV-visible and EPR-silent electron acceptor denoted center S that does not appear to be associated with any of the other metal centers in the protein. Our results support the previous proposals [Anderson, M. E., & Lindahl, P. A. (1994) Biochemistry 33, 8702-8711; Anderson, M. E., & Lindahl, P. A. (1996) Biochemistry 35, 8371-8380] that the Cred2 form of cluster C is two electrons more reduced than the Cred1 form. The combined results from titrations and pre-steady-state studies were used to formulate a mechanism for CO oxidation, composed of the following steps: (i) CO binding to the [Cred1,Box, Xox] state to yield a Cred1-CO complex; (ii) two-electron reduction of Cred1 to Cred2 concerted with CO2 release; (iii) binding of a second CO molecule to the [Cred2,Box,Xox] state to form a Cred2-CO complex; (iv) electron transfer from Cred2-CO to cluster B to form [Cred2,Bred,Xred] with concerted release of the second CO2. Step iii competes with internal electron transfer from Cred2 to Box and Xox. At high CO concentrations, step iii is favored, whereas at low concentrations, only one CO molecule per turnover binds and undergoes oxidation. Closure of the catalytic cycle involves electron transfer from reduced enzyme to an electron acceptor protein, like ferredoxin. Xox is a yet-uncharacterized electron acceptor that may be an intermediate in the reduction of center S. The Cred2 state appears to be the predominant state of cluster C during steady-state turnover. The rate-determining step for the first half-reaction is step iv, while during steady-state turnover, it appears to be electron transfer to external electron acceptors.     

The use of exhaled carbon monoxide for the diagnosis of carbon monoxide poisoning. A case report

Antigliadin antibodies (AGA) mark celiac disease, but AGA are also encountered in IgA-nephritis, psoriasis, sickle-cell anemia, hepatic disorders, juvenile rheumatoid arthritis, autoimmune thyroidism and in persons who occupationally contact great amounts of wheat. AGA IgA and/or IgG were registered in 19 of 60 subjects (51 adults and 9 children) with various immunomediated diseases without symptoms of celiac disease: in 4 cases of chronic active hepatitis, in 2 of 4 cases of chronic persistent hepatitis, in 4 of 16 cases of rheumatoid arthritis, in 3 of 19 cases of IgA-deficiency, in 1 of 8 cases of SLE, in 2 cases of postvaccine reaction, in all the single cases of juvenile rheumatoid arthritis, focal scleroderma, macroglobulinemia. IgA only occurred in in 6 patients, IgG- in 6 patients, both IgA and IgG in 7 patients. The most pronounced positive reaction to AGA was recorded in 8-year-old girl with juvenile rheumatoid arthritis. The emergence of AGA in immunomediated diseases may be attributed to the response to food protein in pathological conditions and is often unrelated closely with celiac disease.     

Reduction kinetics of liquid iron oxide-containing slags by carbon monoxide

The reduction of iron oxides from liquid slags is important in the nonferrous as well as the ferrous industry. In the primary smelting of copper, the trend is to produce copper mattes with increasing contents of copper. This is accomplished by increasing the degree of oxidation, leading to more oxidized slags with higher copper contents. To recover this copper, the high magnetite content of these slags has to be reduced in a separate slag cleaning process. Laboratory reduction experiments on commercial copper slags using carbon monoxide-containing gases show that the reduction rate increases with increasing injection depth and slag temperature. The reduction rate was found to follow the relationship $$Rate(\frac{{molO}}{{m^2 \cdot s}}) = 7.9 \cdot 10^5 \cdot e^{\frac{{ - 43,300}}{{T(K)}}} \cdot p_{CO} (Pa)$$ with an activation energy of 360±20 kJ/mol.     

Mechanism of the toxic action of carbon monoxide

Our studies indicate that a high concentration of carboxyhemoglobin (COHb) does not interfere with the O2--carrying capacity of the blood. In dogs, both the transfusion of erythrocytes containing 80 percent COHb and the i.p. injection of carbon monoxide (CO) gas do not produce CO toxicity even though the COHb is above 50 percent. Dogs inhaling CO (13 percent in air) for 15 minutes died within 15 minutes to 65 minutes with an average COHb level of 65 percent. The probable toxic action of CO is on the cellular respiration taking place in the mitochondria when CO competes with O2 for cytochrome a3. The presence of dissolved CO in plasma, which is necessary for CO to enter the tissue, probably occurs when the exchange takes place between alveolar air and the blood in the lungs. When air containing CO is inhaled, there will be a significant CO tension in the blood when it leaves the lungs and when it reaches the organs especially the heart and brain. While COHb level is useful as a clinical measure of CO exposure, the most important mechanism by which CO causes toxicity is its combination with cytochrome oxidase.     

The kinetics of deoxidation of copper and copper alloys by carbon monoxide

The kinetics of deoxidation of molten copper, Cu-50 pct Ag and Cu-60 pct Sn alloys were studied. The solid electrolyte EMF technique was used to measure the oxygen content as a function of time. The gas was introduced as bubbles emitted from various-sized orifices placed in the melt. Liquid phase mass transfer control is implied by the results for deoxidation in the range 0.05 pct oxygen down to 0.005 pct, where the chemical reaction rate is inferred to become significant in controlling the overall rate. Hughmark’s mass transfer correlation is tested and found to be useful in predicting the liquid phase mass transfer coefficient. This paper is based on a portion of the Dissertation submitted by C. R. NANDA to the Graduate School of the University of Wisconsin in partial filfillment of the requirements for the Ph.D, degree. The research was conducted while the authors were, respectively, Research Assistant and Associate Professor in the Department of Minerals and Metals Engineering, University of Wisconsin, Madison, Wis.     

Diffusing capacity of the lung for carbon monoxide

A phage-display technology was used to produce a single-chain Fv antibody fragment (scFv) from the 30AA5 hybridoma secreting anti-glycoprotein monoclonal antibody (MAb) that neutralizes rabies virus. ScFv was constructed and then cloned for expression as a protein fusion with the g3p minor coat protein of filamentous phage. The display of antibody fragment on the phage surface allows its selection by affinity using an enzyme-linked immunosorbent assay (ELISA); the selected scFv fragment was produced in a soluble form secreted by E. coli. The DNA fragment was sequenced to define the germline gene family and the amino-acid subgroups of the heavy (VH) and light (VL) chain variable regions. The specificity characteristics and neutralization capacity of phage-displayed and soluble scFv fragments were found to be identical to those of the parental 30AA5 MAb directed against antigenic site II of rabies glycoprotein. Phage-display technology allows the production of new antibody molecule forms able to neutralize the rabies virus specifically. The next step could be to engineer and produce multivalent and multispecific neutralizing antibody fragments. A cocktail of multispecific neutralizing antibodies could contain monovalent, bivalent or tetravalent scFv fragments, for passive immunoglobulin therapy.     

红外吸收法测定煤物质中的碳

利用红外吸收法分析煤物质中的碳,选择合适的称样量、助熔剂以及合理的助熔剂添加顺序,使碳的分析精度和准确度达到化学分析方法的水平.     

The chlorination kinetics of zirconium dioxide in the presence of carbon and carbon monoxide

Chlorination of zirconium dioxide, an important step in the commercial production of reactor grade zirconium metal, has been studied using carbon and carbon monoxide as reductants. Zirconium tetrachloride was produced when the oxide was reacted with chlorine alone above 1000°C; by introducing carbon the reaction temperatures could be lowered 200°C, and when carbon monoxide was used the reaction temperatures necessary for similar rates were even lower. With carbon monoxide the chlorination of zirconium dioxide is described by two regions differentiated by temperature and the dependence of reaction rate upon chlorine and carbon monoxide pressures.     

红外池吸收法测定煤粉、焦碳中硫

研究了红外吸收法快速测定煤样、焦炭中硫的分析方法。采用管式炉高温灼烧试样,利用红外池测定试样中硫含量。探讨了温度、称样量、分析时间等因素的最佳分析条件,建立了不同硫含量范围的工作曲线。本方法快速、操作简单,准确度高,精密度好,完全能够满足生产需要。     

Carbochlorination kinetics of titanium dioxide with carbon and carbon monoxide as reductant

Kinetic study of the chlorination of titanium dioxide (rutile and anatase) was carried out in a fixedbed reactor at temperature ranging from 800 °C to 1000 °C and normal pressure. In our experiment, titanium dioxide powder and gaseous chlorine with carbon or carbon monoxide as reductant were used. The products of the reaction are all in gaseous phase under the temperatures and pressure studied. With CO as reductant, reaction is of noncatalytic gas-solid nature and experimental data fit the shrinking core model. When using C as reductant, solid-solid reaction is involved. Reactivity is highly enhanced by solid carbon and it is concluded that an activated C-TiO₂-Cl complex contributes to the enhanced reactivity. A reaction model based on phase boundary control applies to the experimental data. Thermodynamic analysis supports the experimental observation.     

红外吸收法测定镁碳砖中碳

采用高频红外碳硫仪建立了镁碳砖中碳的测定方法,对测定条件如称样量、助熔剂选择和分析时间等条件进行了探讨,分析结果令人满意.