Cytochrome a3 structure in carbon monoxide-bound cytochrome oxidase

The iron-carbon monoxide stretching mode and the iron-carbon-oxygen bending mode in carbon monoxide-bound cytochrome oxidase have been assigned at 520 and 578 cm-1, respectively. The frequencies, widths, and intensities of these modes show that the Fe-C-O grouping in carbon monoxide-cytochrome a3 is linear but tilted from the normal to the heme plane; that the iron-histidine bond in both five- and six-coordinate cytochrome a3 is strained; and that the carbon monoxide and the proximal histidine each have characteristic, well-defined orientations in all molecules. These data can account for the binding affinities of carbon monoxide and dioxygen under physiological conditions.     

Direct observation of global protein motion in hemoglobin and myoglobin on picosecond time scales

Picosecond phase-grating spectroscopy is highly sensitive to density changes and provides a new holographic approach to the study of protein dynamics. Photodissociation of carbon monoxide from heme proteins induces a well-defined transition from a ligated to a deoxy structure that is important to hemoglobin and myoglobin functionality. Grating spectroscopy was used to observe protein-driven density waves on a picosecond time scale after carbon monoxide dissociation. This result demonstrates that global tertiary structure changes of proteins occur on an extremely fast time scale and provides new insight into the biomechanics of deterministic protein motion.     

Regulation of the erythropoietin gene: evidence that the oxygen sensor is a heme protein

Erythropoietin (Epo), the hormone that stimulates red blood cell production, is synthesized in the kidney and liver in response to hypoxia. The human hepatoma cell line Hep3B regulates its production of Epo in a physiologic manner. Either hypoxia or cobalt chloride markedly increases expression of Epo mRNA as well as production of biologically active and immunologically distinct Epo protein. New protein synthesis is required before the induction of increased levels of hypoxia- or cobalt-induced Epo mRNA. Hypoxia, cobalt chloride, and nickel chloride appear to stimulate Epo production through a common pathway. The inhibition of Epo production at low partial pressures of oxygen by carbon monoxide provides evidence that a heme protein is integrally involved in the oxygen-sensing mechanism. This hypothesis is further supported by the finding that when heme synthesis is blocked, hypoxia-, cobalt-, and nickel-induced Epo production are all markedly inhibited. A model is proposed in which a ligand-dependent conformational change in a heme protein accounts for the mechanism by which hypoxia as well as cobalt and nickel stimulate the production of Epo.     

Soil as a sink for atmospheric carbon monoxide

The rate of carbon monoxide oxidation by soil increased with increasing carbon monoxide concentration in the gas phase, in line with Michaelis-Menten kinetics. Rates of carbon monoxide oxidation were determined for 20 soils at 0 degrees , 10 degrees , 20 degrees , and 30 degrees C. The observed oxidation rates were used to calculate a global soil uptake rate of atmospheric carbon monoxide of 4.1 x 10(14) grams per year, which is slightly less than the amount of carbon monoxide believed to be produced annually as a result of fossil fuel combustion.     

Carbon monoxide balance in nature

Consideration of the steady-state equations for stable carbon monoxide and for radioactive carbon monoxide in the troposphere leads to the conclusion that carbon monoxide is produced at a rate of 5x10(15) grams per year, a value some 25 times greater than the rate of carbon monoxide production from combustion. The concomitant residence time for carbon monoxide is 0.1 year, in agreement with a previous estimate of Weinstock. Hydroxyl radicals are shown to account for both the production of this large amount of carbon monoxide by methane oxidation and for its removal by carbon monoxide oxidation. The average concentration of hydroxyl radicals in the troposphere required to achieve this effect is 2.3x10(6) molecules per cubic centimeter, with a daytime concentration of twice that. Levy and McConnell, McElroy, and Wofsy have deduced concentrations of hydroxyl radicals in the troposphere of the same magnitude from purely photochemical considerations, in support of this model.     

Rate theories and puzzles of hemeprotein kinetics

The binding of dioxygen and carbon monoxide to heme proteins such as myoglobin and hemoglobin has been studied with flash photolysis. At temperatures below 200 K, binding occurs from within the heme pocket and, contrary to expectation, with nearly equal rates for both ligands. This observation has led to a reexamination of the theory of the association reaction taking into account friction, protein structure, and the nature of electronic transitions. The rate coefficients for the limiting cases of large and small friction are found with simple arguments that use characteristic lengths and times. The arguments indicate how transition state theory as well as calculations based on nonadiabatic perturbation theory, which is called the Golden Rule, may fail. For ligand-binding reactions the data suggest the existence of intermediate states not directly observed so far. The general considerations may also apply to other biomolecular processes such as electron transport.     

Carbon monoxide in rainwater

Concentrations of carbon monoxide in rainwater collected at widely diverse locations show up to a 200-fold supersaturation relative to the partial pressure of the gas in the atmosphere. These results indicate the existence of an additional natural source of carbon monoxide not heretofore considered. Production of carbon monoxide in clouds is tentatively attributed to the photochemical oxidation of organic matter or the slight dissociation of carbon dioxide induced by electrical discharges, or both. Methane concentrations measured in the same rainwater show that the partitioning of this gas, unlike that of carbon monoxide, is very close to a state of equilibrium.     

Microwave measurement of mesospheric carbon monoxide

Ground-based observation of atmospheric absorption of solar radiation at a wavelength of 2.6 millimeters has provided the first measurement of mesospheric carbon monoxide. The measurement agrees with photochemical predictions of a carbon monoxide source in the lower thermosphere due to dissociation of carbon dioxide by solar radiation, and has implications for the magnitude of vertical transport in the mesosphere.     

MATLAB在不同烤烟品种间主要烟气成分差异性分析中的应用

运用MATLAB 5.0分析云南地区3个烤烟品种的主要烟气成分,结果表明:在0.05显著性水平下有显著性差异的烟气指标,云系列与K326品种间为总粒相物、烟气水分、焦油量、一氧化碳量;云系列和红大品种间为烟气烟碱量、一氧化碳量;红大和K326品种间为烟气烟碱量、一氧化碳量。     

Carboxyhemoglobin concentrations in blood from donors in Chicago, Milwaukee, New York, and Los Angeles

To determine the carbon monoxide exposure experienced by the residents of Chicago, Los Angeles, Milwaukee, and New York, venous blood samples were obtained from adults at arbitrarily chosen blood bank collection sites in the four cities and analyzed for circulating carbon monoxide, carboxyhemoglobin. For comparative purposes, blood was obtained from volunteers breathing carbon monoxide-free air and was found to contain 0.45 percent carboxyhemoglobin. By contrast a high percentage of all the nonsmoking blood donors breathing city air had carboxyhemoglobin saturations greater than 1.5 percent, which indicated that exposure to carbon monoxide in excess of that permitted by the quality standards of the Clean Air Act of 1971 was widespread and occurring regularly.     

Carbon monoxide: residence time in the atmosphere

A lower limit of 0.1 year for the residence time of carbon monIoxide in the atmosphere is derived from radiocarbon measurements. The action of certain microorganisms and atmospheric photochemical reactions are possible mechanisms for the removal of carbon monoxide. This value can be compared with 2.7 years, a value deduced from estimated rates of carbon monoxide production and global measurements of atmospheric concentrations of carbon monoxide.     

Airborne lead and carbon monoxide at 45th Street, New York City

Daily business-day traffic determines the diurnal lead concentration as well as diurnal carbon monoxide concentration. Daily averages of 7.5 micrograms per cubic meter for lead and 13 parts per million of carbon monoxide were found for the 10-week period of the study. Correlations were demonstrated for lead and traffic and lead and carbon monoxide.     

Corrections in the pioneer venus sounder probe gas chromatographic analysis of the lower venus atmosphere

Misidentification of two peaks from the Pioneer Venus sounder probe gas chromatograph (SPGC), also formerly known as the LGC, gave rise to quantitative errors in the abundances of oxygen, argon, and carbon monoxide. The argon abundance is estimated at 67 parts per million and that of carbon monoxide at 20 parts per million. At this time, no estimates for the oxygen abundance can be made.     

Microwave measurements of carbon monoxide on titan

The ratio of the flux density of Titan was measured in two 200-megahertz bands, one centered on the (1-0) rotation line of carbon monoxide at 115.3 gigahertz and the other 2600 megahertz lower. The measurements were made with a complex-correlation technique on the new millimeter-wavelength interferometer at the Owens Valley Radio Observatory, Big Pine, California. The excess flux in the carbon monoxide band is interpreted as a strong detection of carbon monoxide and a mixing ratio, assumed constant, of 6 x 10(-5). The brightness temperature of Titan at 112.6 gigahertz is 69 +/- 10 kelvins, consistent with atmospheric emission from just below the tropopause.     

Soil: a natural sink for carbon monoxide

A potting soil mixture depleted carbon monoxide in a test atmosphere from a concentration of 120 parts per million to near zero within 3 hours. Maximum activity occurred at 30 degrees C. Steam sterilization of the soil, the addition of antibiotics or 10 percent (by weight) saline solution, and anaerobic conditions all prevented carbon monoxide uptake. Sterilized soil inoculated with nonsterile soil acquired activity with time. Samples of various natural soils differed in their ability to remove carbon monoxide from the air. Acidic soils with a high content of organic matter were generally the most active. The soil's ability to remove carbon monoxide from the atmosphere is ascribed to the activity of soil micro-organisms.     

非散射红外法测定卷烟烟气气相中一氧化碳的测量不确定度评定

通过对非散射红外法测定卷烟烟气气相中一氧化碳含量的分析,从测量重复性、一氧化碳示值、抽吸口数、抽吸容量及大气压力和温度等方面计算测定过程的不确定度分量,并计算相对合成标准不确定度和扩展不确定度,达到了对该方法测定一氧化碳的测量不确定度评定的目的,在一定程度上反映了实验室的检测水平。     

Carboxyhemoglobin elevation after exposure to dichloromethane

Inhalation of dichloromethane vapor in concentrations of 500 to 1000 parts per million for 1 to 2 hours promptly initiated the formation of significant quantities of carbon monoxide in human subjects. The evidence suggests that carbon monoxide may be a metabolite of dichloromethane and, that exposure to concentrations of dichloromethane below the industrial threshold limit values may result in the formation of carbon monoxide in amounts that exceed the allowable limits.     

Volcanic gases in the april 1979 soufriere eruption

Six gas samples from the 17 April 1979 Soufriere eruption plume were analyzed for carbonyl sulfide, carbon disulfide, carbon monoxide, carbon dioxide, methane, nitrous oxide, fluorocarbon-11, fluorocarbon-12, methyl chloroform, and carbon tetrachloride. Only carbon monoxide, carbon dioxide, carbonyl sulfide, and carbon disulfide were found to have increased mixing ratios as compared with those in clean tropospheric air, but the increases were not sufficient to contribute greatly to the global budgets of these four components.     

叶片加料回潮工序对卷烟叶组化学成分的影响

运用现代分析技术分析叶片加料回潮工序对卷烟叶组及其制品的化学成分的变化规律。结果表明：叶片加料回潮工序对卷烟叶组的总氮、烟气一氧化碳释放量影响较大,其中总氮含量升高11%,而一氧化碳释放量则降低11%,焦油释放量、烟碱和一氧化碳均与总植物碱的相关性较强,其中焦油释放量与总植物碱呈负相关,烟碱和一氧化碳则与其呈正相关。