CO Saturation Research Articles

Carbonic Anhydrase-Dependent Inorganic Carbon Uptake by the Red Macroalga, Chondrus crispus

The rate of photosynthetic carbon uptake of Chondrus crispus Stack-house plants, at various CO(2) concentrations and pretreated with carbonic anhydrase (CA) inhibitors, was determined using an air-suspension, differential infra-red gas analyzer technique. It was found that the CA inhibitors, acetazolamide, dextran-bound acetazolamide (DBI, which does not permeate cell membranes), and subtilisin (a protease that attacks the cell surface) inhibit photosynthetic carbon uptake in C. crispus. Inhibition was greatest at low CO(2) concentrations, and decreased at CO(2) saturation. Acetazolamide inhibited carbon uptake to a greater extent than DBI. The data support the conclusion that C. crispus plants utilize HCO(3) (-) for photosynthesis, and that both cell-surface and internal CA are involved in the photosynthetic uptake of inorganic carbon.

Stabilization of C 2D x fragments by CO on Ni(100)

The interactions of CO with C 2D 4, C 2D x (vinyl D 2CCD, acetylinic/vinylidene C 2D 2, acetylide C 2D) and CD fragments were investigated on Ni(100) using temperature programmed desorption (TPD), Auger electron spectroscopy (AES), X-ray and UV photoelectron spectroscopies (XPS, UPS) and work function (Δφ) measurements. On clean Ni(100), the C 2D x species decomposed between 190 and 300 K (at low coverage). In the presence of saturation CO, each of these fragments was stable to 375 K ( ∼ 27 kcal mol ) where decomposition produced simultaneous desorption of D 2 and CO. About two CO molecules stabilized each C 2D x fragment. No evidence for direct chemical bonding between C 2D x and CO was found. Based on the XPS and TPD data, the stabilization is attributed to (i) blocking of dissociation sites by CO in the immediate neighborhood of the C 2D x fragment and (ii) repulsion between CO and C 2D x which reduced the C 2D x Ni binding strength. These results are compared with observations during Fisher-Tropsch synthesis on supported metal catalysts.

Cyanide in blood by gas chromatography with NP detector and acetonitrile as internal standard. Application on air accident fire victims.

An improved gas chromatographic method for HCN in blood with acetonitrile as an internal standard has been developed. The necessity to test for cyanide on samples from air accident fire victims is discussed in view of the fact that carbon monoxide measurements usually do not correlate with cyanide findings. Nine cases (out of 67), with blood CO saturation of less than 20% and cyanide concentration over 2 mg/L, are described.

Photosynthesis and Growth of Water Hyacinth under CO2 Enrichment

Water hyacinth (Eichhornia crassipes [Mart.] Solms) plants were grown in environmental chambers at ambient and enriched CO(2) levels (330 and 600 microliters CO(2) per liter). Daughter plants (ramets) produced in the enriched CO(2) gained 39% greater dry weight than those at ambient CO(2), but the original mother plants did not. The CO(2) enrichment increased the number of leaves per ramet and leaf area index, but did not significantly increase leaf size or the number of ramets formed. Flower production was increased 147%. The elevated CO(2) increased the net photosynthetic rate of the mother plants by 40%, but this was not maintained as the plants acclimated to the higher CO(2) level. After 14 days at the elevated CO(2), leaf resistance increased and transpiration decreased, especially from the adaxial leaf surface. After 4 weeks in elevated as compared to ambient CO(2), ribulose bisphosphate carboxylase activity was 40% less, soluble protein content 49% less, and chlorophyll content 26% less; whereas starch content was 40% greater. Although at a given CO(2) level the enriched CO(2) plants had only half the net photosynthetic rate of their counterparts grown at ambient CO(2), they showed similar internal CO(2) concentrations. This suggested that the decreased supply of CO(2) to the mesophyll, as a result of the increased stomatal resistance, was counterbalanced by a decreased utilization of CO(2). Photorespiration and dark respiration were lower, such that the CO(2) compensation point was not altered. The photosynthetic light and CO(2) saturation points were not greatly changed, nor was the O(2) inhibition of photosynthesis (measured at 330 microliters CO(2) per liter). It appears that with CO(2) enrichment the temporary increase in net photosynthesis produced larger ramets. After acclimation, the greater total ramet leaf area more than compensated for the lower net photosynthetic rate on a unit leaf area basis, and resulted in a sustained improvement in dry weight gain.

Effects of potassium and calcination pretreatment on the adsorption and chemical/physical properties of [formula omitted

Studies of the effects of potassium on CO, CO/sub 2/, and hydrogen adsorptions on iron indicate that potassium promotion increases heats of adsorption of CO and H/sub 2/, enhances the rate of CO dissociation, increases CO saturation coverage, and decreases the CO sticking coefficient. The purpose of this work was to investigate the effects of potassium promoter and calcination of the stoichiometries and kinetics of CO, CO/sub 2/, and H/sub 2/ adsorptions on Fe/SiO/sub 2/ and to relate these effects to changes in the physical and chemical properties of the catalyst. The results reveal important differences in behavior for CO and H/sub 2/ adsorptions on precalcined Fe/SiO/sub 2/ and Fe/K/SiO/sub 2/ compared to the adsorptions on single crystal or polycrystalline iron, which may relate to changes in the surface and bulk properties of iron such as potassium coverage and extent of reduction. 33 references.

Infrared reflectance absorbance spectroscopy of coadsorbed CO and H2O on Pt(111) surfaces

We have used polarization modulated infrared reflectance absorbance spectroscopy (IRRAS) to study the interactions between coadsorbed CO and H2O on Pt(111) surfaces at 150 K. Two types of behavior are observed, depending on CO coverage. For CO coverages greater than θ≊1/2, the vibrational band for linear CO species shifts from 2100 cm−1 for an H2O-free surface to 2095 cm−1 for H2O exposures up to 15 L. For larger H2O exposures a second, broader band appears at around 2080 cm−1. These results indicate that H2O adsorbs in clusters on top of a saturated CO adlayer, without strongly perturbing the CO molecules underneath. In contrast, for CO coverages less than θ≊1/4, adsorption of H2O at 150 K results in the disappearance of the linear CO vibrational band, with its subsequent reappearance upon desorbing the H2O layer. This indicates that for low CO coverages, coadsorbed H2O can displace CO out of its preferred linear coordination mode.

Quantum Yields of CAM Plants Measured by Photosynthetic O2 Exchange

The quantum yield of photosynthetic O(2) exchange was measured in eight species of leaf succulents representative of both malic enzyme type and phosphoenolpyruvate carboxykinase type CAM plants. Measurements were made at 25 degrees C and CO(2) saturation using a leaf disc O(2) electrode system, either during or after deacidification. The mean quantum yield was 0.095 +/- 0.012 (sd) moles O(2) per mole quanta, which compared with 0.094 +/- 0.006 (sd) moles O(2) per mole quanta for spinach leaf discs measured under the same conditions. There were no consistent differences in quantum yield between decarboxylation types or during different phases of CAM metabolism. On the basis of current notions of compartmentation of CAM biochemistry, our observations are interpreted to indicate that CO(2) refixation is energetically independent of gluconeogenesis during deacidification.

A static SIMS/TPD study of the kinetics of methoxy formation and decomposition on O/Pt(111)

The kinetics and mechanism of the decomposition of methanol (CH 3OD) on oxygen-covered Pt(111) were studied using static secondary ion mass spectrometry (SIMS) and temperature programmed desorption (TPD). The initial sticking coefficient and the saturation first layer coverage of CH 3OD are unity and 0.36 ML, respectively. The maximum amounts decomposed in TPD on O/Pt(111) and clean Pt(111) are 0.19 and 0.047 ML, respectively. At low methanol coverages (< 0.05 ML) on O/Pt(111) the only reaction products were CO 2, H 2O and D 2O, whereas at saturation CO, H 2O, D 2O and H 2 were observed. The decomposed amount did not saturate at or before the onset of molecular methanol desorption, but increeased monotonically until saturation of the first layer. No oxygen exchange was observed between CH 3OD and preadsorbed 18O. A decomposition mechanism involving methoxy and hydroxyl type species is proposed. Methanol coverages as low as 0.002 ML could be detected with SIMS. The CH 3 + ion was the most intense ion in the positive SIMS spectrum of both methanol and methoxy. Larger ion clusters such as (CH 3OD) n + ( n = 2, 3) developed successively at specific multilayer coverages. At low coverages on O/Pt(111), methoxy formation occurs above 125 K and its decomposition becomes detectable above 150 K during temperature programming. In the isothermal mode, the SIMS CH 3 + ion was used to follow the kinetics. Over the temperature range 120–145 K, the second order Arrhenius rate parameters for methoxy formation are E = 5.5±0.7 kcal/mol and A = 1.5×10 −7±0.6 cm 2/s·molecule for an initial methanol coverage of 0.05 ML. Methoxy decomposition was studied in the temperature range 150–165 K and at an initial coverage of 0.015 ML. The first order kinetic parameters, E = 11.4±0.5 kcal/mol and A = 5.3×10 13±1 s −1 were derived. Advantages and limitations of using SIMS as a tool for kinetic studies are discussed.

Effect of titania oxidation state on the chemisorptive properties of titania-supported nickel

Temperature-programmed desorption (TPD) under ultrahigh vacuum conditions and transmission electron microscopy (TEM) were used to characterize the adsorption behavior of CO and H 2 on low-surface-area samples prepared by depositing nickel onto titania films. The effect of titania oxidation state on CO adsorption from Ni was probed by studying 0.2-nm Ni overlayers deposited in situ on titania surfaces vacuum-annealed at successively higher temperatures to vary the oxygen-to-titanium ratio from 2 to 1. The CO adsorption strength and saturation coverage on Ni decreased with increased extent of titania reduction. These effects could be attributed to electronic metal-support interaction between Ni and underlying titania in the absence of titania adspecies on the Ni surface. This type of interaction becomes unimportant for Ni overlayers or Ni crystallites thicker than about 3 atomic layers. The strength of CO adsorption was also found to be dependent on the initial nickel overlayer thickness for samples reduced at 650 K in hydrogen at 10 −3 Pa. The desorption peak temperature increased from 360 K for a 0.2-nm Ni overlayer to 420 K for a 2.5-nm Ni overlayer. It is proposed that the thinner nickel overlayers lead to smaller nickel particles during this treatment in hydrogen and that these smaller particles are more completely covered by titania adspecies from the support. Transmission electron micrographs suggested that the supported Ni crystallites develop a raft-like morphology upon reduction. The Ni particles were relatively resistant to sintering. Dissociative CO adsorption on the model nickel/titania surfaces was not observed under any conditions, suggesting that the Ni crystallites adopt flat morphologies and that sites active for CO dissociation under ultrahigh vacuum conditions are not created at nickel/titania interfaces.

Steric and electronic effects of sulfur on CO adsorbed on Pd(100)

The mechanism of sulfur poisoning was studied on the Pd(100) surface using TPD, HREELS, and LEED for sulfur coverages ranging from zero to saturation (0.5 monolayer). A rapid initial decrease in the CO saturation coverage at 80 K was observed up to a sulfur coverage of about 0.1 ML. Coincident with this coverage decrease the formation of high-density CO compression structures is blocked as revealed by LEED. Thereafter the CO coverage declines linearly in a nearly 1:1 ratio with the addition of adsorbed sulfur. For low θ CO the CO stretching frequency increased from 1895 to 1925 cm −1 as the sulfur coverage was increased from zero to saturation. The CO singleton frequency at θ s=0.50 is slightly less than the reported C 12O singleton stretching frequency in the presence of 0.5 monolayer of C 13O, indicating that adsorbed sulfur has less effect on the CO bond than adsorbed CO itself at this coverage. The observed value of the CO stretching frequency at CO saturation coverage decreases with increasing sulfur coverage. This net decrease in ν(CO) with θ s for saturation coverage by CO coincides with the reduction in CO coverage in the presence of adsorbed sulfur. Sulfur does not appear to change the bridge-site preference of adsorbed CO, and the decrease in the saturation coverage for 0< θ s<0.10 is ascribed to disorder in the CO adlayer induced by the preadsorbed sulfur. When compared to the sulfur-free surface at the same CO coverage there is an increase in the CO stretching frequency. This increase in the CO stretching frequency at saturation coverage by CO due to adsorbed sulfur rises rapidly at low sulfur coverage and remains constant above θ s=0.15. This effect appears to be due to COCO coupling transferring the local changes in frequency caused by sulfur to the entire adsorbed layer.

Atmospheric temperature response to variations in CO 2 concentration and the solar-constant

The response of the Earth's global mean vertical atmospheric temperature structure to large increases in the atmospheric CO 2 concentration was examined using a 1-D radiative-convective atmospheric model. It was found that the greenhouse warming of the terrestrial surface can be strongly inhibited by the development of a more isothermal, moister and higher troposphere than at present. The saturation of the strong CO 2 infrared bands for high CO 2 concentrations further inhibits the greenhouse warming to such an extent that a runaway greenhouse fuelled only by a rise in the atmospheric CO 2 is not possible. However, a continuously rising solar-constant does eventually lead to a runaway.

Effects of CO2 and O2 on the Photosynthetic O2 Evolution of Spirodela polyrrhiza Turions

Net photosynthetic rates of Spirodela polyrrhiza turions, at low O(2) levels, were 6.2 and 38.8 micromoles O(2) per gram fresh weight per hour at 1 millimolar HCO(3) (-) and CO(2) saturation, respectively, and much lower in a regular low-pH growth solution. Air equilibration O(2) concentrations decreased rates considerably, except at CO(2) saturation. The surfacing rate of turions in various inorganic carbon surroundings correlated positively with their photosynthetic rates, but were the same at high and low O(2) levels. The relevance of these findings in relation to environmental conditions conductive to germination of autotrophically growing turions is discussed.

The properties of K and coadsorbed Co + K on Ru(001) I. Adsorption, desorption, and structure

Abstract An extensive photoemission and LEED study of K and CO+K on Ru(001) has been carried out. In this paper the LEED and some XPS results together with TPD and HREELS data are presented in terms of adsorption, desorption. and structural properties, and their compatibility is discussed. Potassium forms (2 × 2) and ( 3 × 3 )R30° overlayers below and near monolayer coverage, and multilayer bonding and desorption is similar to that of bulk K. The initial sticking coefficients for CO adsorption on K predosed surfaces are correlated with the initial K structure, and s0 and CO saturation coverages decrease with increasing K coverage. Two well-characterized mixed CO+K layers have been found which are correlated with predosed (2 × 2) K and ( 3 × 3 )R30° K . They have CO to K ratios of 3:2 and 1:1, and lead to LEED patterns with (2 × 2) and (3 × 3) symmetry, respectively. The molecule is believed to be sp2 rehybridized under the influence of coadsorbed K, leading to stronger CO-Ru and weaker C-O bonds as indicated by the TPD and HREELS results, and to stand upright in essentially twofold bridges.

The properties of K and coadsorbed CO + K on Ru(001): I. Adsorption, desorption, and structure

An extensive photoemission and LEED study of K and CO+K on Ru(001) has been carried out. In this paper the LEED and some XPS results together with TPD and HREELS data are presented in terms of adsorption, desorption. and structural properties, and their compatibility is discussed. Potassium forms (2 × 2) and (3 × 3)R30° overlayers below and near monolayer coverage, and multilayer bonding and desorption is similar to that of bulk K. The initial sticking coefficients for CO adsorption on K predosed surfaces are correlated with the initial K structure, and s0 and CO saturation coverages decrease with increasing K coverage. Two well-characterized mixed CO+K layers have been found which are correlated with predosed (2 × 2) K and (3 × 3)R30° K. They have CO to K ratios of 3:2 and 1:1, and lead to LEED patterns with (2 × 2) and (3 × 3) symmetry, respectively. The molecule is believed to be sp2 rehybridized under the influence of coadsorbed K, leading to stronger CO-Ru and weaker C-O bonds as indicated by the TPD and HREELS results, and to stand upright in essentially twofold bridges.

Growth and properties of Cu on Ni(100)

The growth of Cu on Ni(100) at room temperature has been investigated by XPS and is found to be layer-by-layer up to three monolayers coverage. Cu 2p 3 2 binding energy increased with Cu coverage to a plateau at θ Cu=0.3 and increased further to the Cu bulk value with the growth of the second layer. Chemisorption of CO on Cu/Ni(100) surfaces has been investigated at room temperature. The saturation CO uptake decreased linearly with Cu coverage up to θ Cu = 0.3 after which there was a more gradual linear decrease up to one monolayer Cu coverage when the surface did not take up CO to a measurable extent. This behaviour is interpreted in terms of a transition from a c(2 × 2) type Cu structure to (1 × 1).

Bronchial hyperreactivity and arterial carboxyhemoglobin as detectors of air pollution in Milan: a study on normal subjects.

Research has been carried out in the town area of Milan on 275 subjects. For each patient the following data have been measured: ventilatory profile, aspecific bronchial reactivity, arterial concentration in CO and acid-base balance. The results obtained have been divided into four groups, according to the level of SO2 in the area of residence of the subjects, who have also been studied with reference to the habit of smoking. The data obtained have shown (1) an alteration of the ventilatory function, with decrease of oxygen tension in arterial blood in all subjects. (2) Increase of bronchial irritability and CO concentration in arterial blood have been found in these subjects, with rates higher than those established by the WHO (1.5-1.7). (3) The division of our results according to the level of SO2 pollution in the areas of residence of the patients showed the presence, in the most polluted areas of Milan (NE and SW), of higher levels of bronchial irritability and higher CO rates in arterial blood. (4) Cigarette smoking does not seem to play a major role in causing bronchial irritability. It certainly increases CO concentration: smokers have HbCO concentration higher than nonsmokers in all four areas. (5) Air pollution is more important than cigarette smoking in determining CO saturation of blood. Nonsmokers living in the most polluted areas of Milan (NE) show a higher concentration of CO in arterial blood than smokers living in the less polluted areas (SW).

Surface characterization of supported Pt, Rh, and alloy particles by CO chemisorption

Temperature programmed desorption (TPD) of CO is used to determine surface areas, binding states, and changes upon oxidation for 10–1000 Å particles of Pt, Rh, and Pt-Rh alloy on amorphous SiO 2. A low area sample configuration is used to obtain rapid and uniform heating and cooling in an ultra-high vacuum system. It is shown that both metals exhibit a higher CO binding state for small particles, but, as particle size increases, this state disappears and is replaced by a more weakly bound state. These states are suggested to be associated with (111) and higher surface free energy planes on these surfaces, heating Rh above 700 K in O 2 at 10 −6 Torr produces an oxide on which the CO saturation coverage is at least a factor of 10 lower than on the reduced surface. For Pt, oxidation produces only a small decrease in CO coverage, although the binding energy of CO increases on the oxygen treated surface. The difference in desorption temperatures for CO on Pt and Rh is consistent with previous experiments which show that an oxidation-reduction cycle produces a surface layer which is enriched in Rh and that the oxidized alloy contains no Pt atoms.

Infrared studies of CO adsorption on reduced and oxidized [formula omitted

Carbon monoxide adsorption experiments were studied on reduced and oxidized Pt TiO 2 with FT-IR. On reduced samples two kinds of linear CO species were observed and assigned as adsorption on Pt close-packed (terrace) sites (2094 cm −1) and on Pt open (step) sites (2077 cm −1). In addition a bridged CO species was found at 1854 cm −1. Both linear species show increasing frequencies with coverage. Saturation CO uptake decreases with increasing substrate reduction temperature and there is a preferential decrease of linear CO species on terrace sites and the concentration of bridged species lies below detection limits. On oxidized Pt TiO 2 samples, some Pt atoms are covered with oxygen atoms and the density of step sites is enhanced. On these surfaces there are two kinds of linear CO species assigned to terraces (2130 cm −1) and steps (2101 cm −1) and a bridged CO species at 1880 cm −1. In addition, several CO species are found which are also detected on reduced samples. These species show intensity variations during lengthy exposures. Preadsorbed linear CO species (2130, 2094, and 2077 cm −1 bands) on oxidized samples are also sensitive to H 2 exposures.

Photoinhibition of CO2-Dependent O2 Evolution by Intact Chloroplasts Isolated from Spinach Leaves

Intact spinach (Spinacia oleracea L.) chloroplasts, when pre-illuminated at 4 millimoles quanta per square meter per second for 8 minutes in a CO(2)-free buffer at 21% O(2), showed a decrease (30-70%) in CO(2)-dependent O(2) evolution and (14)CO(2) uptake. This photoinhibition was observed only when the O(2) concentration and the quantum fluence rate were higher than 4% and 1 millimole per square meter per second, respectively. There was only a small decrease in the extent of photoinhibition when the CO(2) concentration was increased from 0 to 25 micromolar during the treatment, but photoinhibition was abolished when the CO(2) concentration was increased to 30 micromolar. Addition of small quantities of P-glycerate (40-200 micromolar) or glycerate (160 micromolar) was found to prevent photoinhibition. Other intermediates of the Calvin cycle (fructose-6-P, fructose-1,6-P, ribose-5-P, ribulose-5-P) also prevented photoinhibition to various extents. Oxaloacetate was not effective in preventing photoinhibition in these chloroplasts. The amount of O(2) evolved during treatments with 3-P-glycerate or glycerate was no more than 65% of that measured in the presence of low CO(2) concentrations (9-12 micromolar) which did not prevent photoinhibition. In all cases, the extent to which photoinhibition was prevented by these metabolites was not correlated to the amount of O(2) evolved during the photoinhibitory treatment. It is concluded that in these chloroplasts the prevention of the O(2)-dependent photoinhibition of light saturated CO(2) fixation capacity is not linked to the dissipation of excitation energy via the photosynthetic electron transport nor to ATP utilization. The requirement of O(2) for photoinhibition of CO(2) fixation capacity in isolated chloroplasts may be explained by an effect of O(2) in allowing metabolic depletion of Calvin cycle intermediates.

Oxidation of Carbonyl

Oxidation reactions of carbonyl species of hemoglobins A, Zurich, and Osler with ferricyanide to form met‐hemoglobins have been investigated at pH 7.0 and 25°C. The kinetics support a two‐step process in which, first, CO is lost to give the unliganded reduced species (deoxy), followed by oxidation in a one‐electron transfer to ferricyanide ion. On and off rates for CO markedly affect the overall oxidation rate. That α subunits oxidize more rapidly than B subunits was noted by changes in C–O stretch frequency during the course of reactions with Hb A and Hb Zurich. The substitution of Arg for His at β63 in Hb Zurich resulted in a slower overall oxidation rate ascribable to greater affinity for CO. MetHb formation from stripped HbCO A was biphasic with the rate for the final ∼ 50% of the reaction about 30% faster than that for the initial ∼ 50%. Addition of inositol hexakis‐phosphate increased rates several‐fold in both phases and shifted the point of change from slow to fast phase. These effects suggest that inositol hexakisphosphate binds weakly (Kd∼ 30 μM) to Hb4(CO)4 in a high‐affinity state which, after loss of one CO, changes to a low‐affinity state where inositol hexakisphosphate binds more strongly (Kd &lt; 1 μM) for the remainder of the reaction. With Hb Osler, which exhibits very low heme‐heme interaction and reacts poorly with inositol hexakisphosphate, the reaction was monophasic with a rate throughout comparable to the initial rate for stripped HbCO A. The very low level of CO saturation (&lt; 1–6%) usually found in vivo with normal hemoglobin subunits should not greatly affect overall rates of methemoglobin formation from one‐electron electron acceptors. However, with the high levels of CO found bound (20–100% saturation) to the β subunit of hemoglobin Zurich in blood, the exposure to CO (as in smoking) can diminish the extent to which the abnormal Zurich subunit will be oxidized. CO exposure may, therefore, reduce significantly some of the undesired consequences of having hemoglobin Zurich in red blood cells.