Oxygen Dissociation Research Articles

Remote ischemic conditioning enhances oxygen supply to ischemic brain tissue in a mouse model of stroke: Role of elevated 2,3-biphosphoglycerate in erythrocytes

Oxygen supply for ischemic brain tissue during stroke is critical to neuroprotection. Remote ischemic conditioning (RIC) treatment is effective for stroke. However, it is not known whether RIC can improve brain tissue oxygen supply. In current study, we employed a mouse model of stroke created by middle cerebral artery occlusion (MCAO) to investigate the effect of RIC on oxygen supply to the ischemic brain tissue using a hypoxyprobe system. Erythrocyte oxygen-carrying capacity and tissue oxygen exchange were assessed by measuring oxygenated hemoglobin and oxygen dissociation curve. We found that RIC significantly mitigated hypoxic signals and decreased neural cell death, thereby preserving neurological functions. The tissue oxygen exchange was markedly enhanced, along with the elevated hemoglobin P50 and right-shifted oxygen dissociation curve. Intriguingly, RIC markedly elevated 2,3-biphosphoglycerate (2,3-BPG) levels in erythrocyte, and the erythrocyte 2,3-BPG levels were highly negatively correlated with the hypoxia in the ischemic brain tissue. Further, adoptive transfusion of 2,3-BPG-rich erythrocytes prepared from RIC-treated mice significantly enhanced the oxygen supply to the ischemic tissue in MCAO mouse model. Collectively, RIC protects against ischemic stroke through improving oxygen supply to the ischemic brain tissue where the enhanced tissue oxygen delivery and exchange by RIC-induced 2,3-BPG-rich erythrocytes may play a role.

Photoacoustics resolves species-specific differences in hemoglobin concentration and oxygenation.

.Significance: Photoacoustic imaging (PAI) enables the detection of blood hemoglobin (HB) concentration and oxygenation () with high contrast and resolution. Despite the heavy use of photoacoustically determined total hemoglobin () and oxygenation () biomarkers in PAI research, their relationship with underlying biochemical blood parameters and the impact of intra- and interspecies genetic variability have yet to be established.Aim: To explore the relationship between THb and photoacoustic biomarkers and the underlying biochemical blood parameters in a species-specific manner.Approach: Experiments were performed on blood in vitro using tissue-mimicking agar phantoms. Blood was extracted from mouse, rat, human, and naked mole-rat (Heterocephalus glaber), anticoagulated in ethylenediaminetetraacetic acid, and measured within 48 h. THb and were measured using a commercial photoacoustic tomography system (InVision 128, iThera Medical GmBH). Biochemical blood parameters such as HB concentration (g/dL), hematocrit (HCT, %), and red blood cell (RBC) count () were assessed using a hematology analyzer (Mythic 18 Vet, Woodley Equipment).Results: A significant correlation was observed between THb and biochemical HB, HCT, and RBC in mouse and rat blood. Moreover, PAI accurately recapitulated interspecies variations in HB and HCT between mouse and rat blood and resolved differences in the oxygen dissociation curves measured using between human, mouse, and rat. With these validation data in hand, we applied PAI to studies of blood obtained from naked mole-rats and could confirm the high oxygen affinity of this species in comparison to other rodents of similar size.Conclusions: Our results demonstrate the high sensitivity of photoacoustically determined hemoglobin biomarkers toward species-specific variations in vitro.

Numerical analysis of the influence of RBCs on oxygen transport within a tissue with an embedded capillary network

In this paper, the oxygen transport in a capillary network and the surrounding tissue was simulated by considering the influence of red blood cells (RBCs). To simplify this problem, the erythrocytes as the oxygen carriers were modelled as one-dimensional (1 D) spheres, and oxygen and haemoglobin diffusion took place only in the radial direction. The direction of movement of the RBCs at the network bifurcations was determined by a probability function related to the ratio of the flow rate in the mother vessel to that in a daughter vessel. The capillaries were reduced to a skeleton structure that included vessels with different radii, lengths, and three-dimensional (3 D) coordinates. The capillary network was embedded in a 3 D tissue, which was considered as a homogeneous porous medium. The interactions between the capillary network and the surrounding tissue were solved by the immersed boundary method. The influence of RBC rheological behaviours, such as deformation capacity and flux, on oxygen transport were analysed. The oxygen dissociation capacity of the RBCs was also investigated. The results showed that when the RBCs’ deformation capacity was weakened, the probability of RBCs choosing large-flow daughter vessel at the bifurcation increased considerably, leading to a highly non-uniform distribution of RBCs in the network. The non-uniformity of the RBCs further led to partial hypoxia in regions through which no RBCs passed. In contrast, a lower haematocrit and weakening of the oxygen release capability led to the overall decline of oxygen partial pressure in the whole region.

Ferromagnetic metal conversion directly from two-dimensional nickel hydroxide

We have demonstrated a direct metallic conversion from nickel hydroxide nanosheets to nickel metal nanostructures by thermal annealing in vacuum. The metal transition of the single-layer nanosheets deposited on a Si substrate was revealed by x-ray absorption near edge structure (XANES) measurements. The XANES signal significantly changed at annealing temperatures above 250 °C. The metal transition temperature coincides with the reported temperatures at which layered nickel hydroxide nanosheets are converted to nickel oxide nanosheets by calcination in air. Auger measurements confirmed that a dissociation of oxygen from the hydroxide nanosheet induces the metallic conversion. The converted nickel metallic structures exhibit ferromagnetic behavior revealed by x-ray magnetic circular dichroism (XMCD) measurement. Atomic force microscopy measurements indicate that diffusions of nickel atoms on the substrates leads to a structural change from a 2D-like structure to a particle-like structure.

Templated synthesis of cobalt subnanoclusters dispersed N/C nanocages from COFs for highly-efficient oxygen reduction reaction

Development of nonprecious metal-based electrocatalysts with highly efficient oxygen reduction reaction (ORR) has increasingly attracted wide attention in energy conversion and storage systems. In this work, we stepwise grow cobalt chelated COF TpBpy (Co-TpBpy) on silica nanospheres to form core–shell SiO2@Co-TpBpy nanospheres. After calcination high temperatures and removing silica template, cobalt subnanoclusters dispersed in N-doped carbon (N/C) nanocages are obtained for ORR. As a result, the Co-TpBpy-800 nanocages exhibit highly efficient activity on electrocatalytic ORR with 0.831 V of half-wave potential and high stability. Moreover, DFT calculation verifies the resulting unique nanocages reveal an unconventional five-step ORR process in which it skips the intermediate OOH* because the oxygen dissociation and adsorption directly occur on the catalyst surface. The present work will help the development of highly-efficient nonprecious metal-based catalysts for various energy applications.

The Effect Of Elevation Training Mask On Skeletal Muscle Oxygenation During Walking

Elevation training masks are commonly used to enhance training and performance. While these masks do not generate a hypoxic environment, they are used to train the respiratory system, a common limiting factor in performance in both trained and sedentary individuals. There is limited evidence as to how these masks affect respiration or skeletal muscle oxygenation. PURPOSE: The purpose of this study was to determine how resisted inspiration affects respiration and muscle oxygenation during walking. METHODS: 8 subjects between 18-35 years of age were recruited to walk at 1.6 m/s for 10 minutes with (RI) and without (CON) resisted inspiration. Masks were connected to the metabolic cart and a Moxy monitor was placed on the lateral head of the gastrocnemius to measure muscle oxygenation (SmO) throughout the duration of walking trials. The last 5 minutes of each condition were analyzed and presented as mean ± SD. Student t-test was used to determine significance at p<0.05. RESULTS: RI had no effect on VO2 (CON: 14.17±0.96 RI: 14.23±2.94, p=0.95) or VCO2 (CON: 13.02±0.89 RI: 13.18±2.61, p=0.89). RI caused an average increase of 4.9% in subjects heart rate and induced a significant decrease in respiration rate (CON: 25.93±1.59 RI: 18.63±3.84, p=0.0006). This coincided with no change in total hemoglobin (ThB) in the skeletal muscle (CON: 12.58±0.61 RI: 12.57±0.60, p=0.98) and an increase in 7 out of 8 subject’s SmO with restricted breathing (CON: 41.94±20.15 RI: 48.52±23.08). Despite increased SmO, subjects reported a higher RPE in the RI condition. CONCLUSIONS: During walking, elevation training masks increase skeletal muscle oxygenation. This could be in part due to a longer inspiration allowing for improved blood oxygen saturated. An increased heart rate across most subjects despite no change in ThB could suggest a shift in the hemoglobin dissociation curve allowing more oxygen dissociation in the muscles. Future studies should examine the effect of elevation training masks on muscle oxygenation during higher intensity exercises.

Improved Analysis of Ultraviolet Absorption Spectra Under Nonequilibrium Shock Conditions

A landmark set of measurements of high-temperature relaxation under strong shock heating conditions, conducted in 2013 by Ibraguimova et al. (“Investigation of Oxygen Dissociation and Vibrational Relaxation at Temperatures 4000–10800 K,” Journal of Chemical Physics, Vol. 139, No. 3, 2013, Paper 034317) using ultraviolet (UV) absorption converted to time-dependent vibrational temperature profiles, have been receiving considerable attention in the literature as a test of nonequilibrium thermochemical models. A number of attempts by computational fluid dynamics modelers to reproduce the published results were unsuccessful in predicting the peak vibrational temperature, the downstream slope, or both. Our recent analysis has shown that some of the assumptions used in spectra-to-temperature conversions, such as the two-temperature approximation, are violated in the early region of the shock, and a more detailed analysis and direct comparison of UV absorption, and not temperatures, is necessary. This work presents such an analysis where a gas number density, translational temperature, and distribution of rotational and vibrational level populations, obtained using a kinetic gas dynamic approach, are converted into UV in-band absorption for each temporal or spatial location in the shock using a detailed spectroscopic model. The computed UV absorption is then directly compared with the raw measured time-dependent UV absorption curves at several wavelengths. Such a comparison is shown to have more validity than the previous ones.

Studies on effect of Ca-doping on structure and electrochemical properties of garnet-type Y3-xCaxFe5O12-δ

In this study, effect of Ca-doping on electrical and electrochemical properties of garnet structure Y3-xCaxFe5O12-δ (x ​= ​0, 0.05, 0.1, 0.3, 0.5 and 0.7) was investigated. Cubic-phase (Ia-3d) garnet was prepared through sol-gel method and sintered at 1100 ​°C for 2 ​h in air. Highest oxygen non-stoichiometry (δ ​= ​0.19) was found in x ​= ​0.3 member. X-ray absorption spectroscopy (XAS) confirmed the formation of hole carriers (Fe.Fe) due to Ca-substitution for Y in Y3Fe5O12. 4-Probe DC measurements showed that electrical conductivity increased with an increase in Ca amount until x ​= ​0.1 (1.58 ​S/cm at 750 ​°C) and then decreased due to decrease in the concentration of the charge carriers. Lowest area specific resistance (ASR) of 1 Ωcm2 was seen at 750 ​°C in air for the symmetrical cell with x ​= ​0.3 garnet-LSGM composite electrode. Studies on pO2 dependent ASR and impedance spectroscopy genetic programming (ISGP) analysis revealed that oxygen dissociation and partial reduction of adsorbed oxygen molecule co-limit the electrochemical performance for oxygen reduction reaction (ORR).

Role of haemoglobin oxygen affinity for oxygen uptake during exercise

Role of haemoglobin oxygen affinity for oxygen uptake during exercise

Role of Adsorbate Coverage on the Oxygen Dissociation Rate on Sr-Doped LaMnO3 Surfaces in the Presence of H2O and CO2

Sr-doped LaMnO3 (LSM) is a promising oxygen reduction reaction electrocatalyst in solid oxide fuel cells and other electrochemical devices. The presence of CO2 and H2O has been reported to promote the oxygen dissociation reaction on LSM surfaces. Here, we investigate the coadsorption mechanism of O2 with H2O or CO2 by combining first-principles calculations of the (0 0 1) surface containing 25–100% Sr with thermodynamic adsorption models. The molecules were found to chemisorb by formation of charged oxygen, hydroxide, and carbonate species, and the adsorption energies were exothermic up to monolayer coverage. Low concentrations of H2O or CO2 do not compete with O2 for adsorption sites under relevant conditions. However, their presence contributes to the total amount of oxygen-containing species. The increased coverage of oxygen species provides a quantitative explanation for the reported enhancement in oxygen dissociation kinetics in the presence of H2O/CO2. This study thereby provides insights into oxygen exchange mechanisms on LSM surfaces.

Hypoxia and comparative physiology in humans: Diversity in haemoglobin and oxygen dissociation curve shifting

Hypoxia and comparative physiology in humans: Diversity in haemoglobin and oxygen dissociation curve shifting

Effect of point mutation on structure-function correlation of hemoglobin variants, HbE and HbD Punjab.

Hemoglobinopathies are examples of autosomal recessive disorders of human hemoglobin. Hemoglobin E (HbE) and Hemoglobin D Punjab (HbD Punjab) are two of the most common hemoglobin variants geographically spread across Asian continent. These two variants differ from normal human hemoglobin (HbA) at a single amino acid residue caused by the point mutation of β globin gene. The presence of the mutated amino acid residue causes perturbation in the function of both variants. However, the structure-function correlation of these variants has not been established yet. In the present study, we analyzed the conformational changes associated with oxygenation of hemoglobin variants using hydrogen/deuterium exchange-based mass spectrometry of backbone amide hydrogens of α and β globin chains in the tetrameric hemoglobin molecule. We also performed the functional assay of these variants using oxygen dissociation equilibrium curve. Compared toHbA, both variants showed reduced oxygen affinity, as reported earlier. The functional perturbations exhibited by these variants were correlated well with their structural alterations with respect to the reported changes in the residue level interactions upon oxygenation of normal hemoglobin, monitored through the hydrogen/deuterium exchange kinetics of several peptic peptides originated from the isotopically exchanged oxy and deoxy forms of HbE and HbD Punjab.

Dissociative Oxygen Reduction Reaction Mechanism on the Neighboring Active Sites of a Boron-Doped Pyrolyzed Fe–N–C Catalyst

We study the oxygen reduction reaction (ORR) mechanism on the neighboring active sites of a B-doped pyrolyzed Fe–N–C catalyst using a combination of density functional theory-based calculations and...

Oxidation behavior and microstructure evolution of alumina-forming austenitic & high entropy alloys in steam environment at 1200 °C

Oxidation tests of alumina-forming austenitic (AFA) alloys and high entropy alloys (HEA) have been performed in steam at 1200 °C. AFA alloys with composition formula Fe-3Al-16Cr-(19-21)Ni (wt.%) and HEA with formula Al(7.9-8.9)Cr(21.4-23.2)Ni(34.3-35)Febal (at.%) show low oxidation rate due to the formation of α-Al2O3 scale. By adding yttrium to AFA or niobium to HEA, the samples show no evidence of scale exfoliation. HEA with titanium addition forms a thick oxide layer based on TiO2, Cr2O3 and internal Al oxidation. The growth of oxide scale is discussed based on the oxygen partial pressure of metal oxides and dissociation oxygen pressure of the steam.

Lucina pectinata oxyhemoglobin (II-III) heterodimer pH susceptibility

Lucina pectinata live in high concentrations of hydrogen sulfide (H2S) and contains one hemoglobin, Hemoglobin I (HbI), transporting H2S and two hemoglobins, Hemoglobin II (HbII) and Hemoglobin (HbIII), transferring dioxygen to symbionts. HbII and HbIII contain B10 tyrosine (Tyr) and E7 glutamine (Gln) in the heme pocket generating an efficient hydrogen bonding network with the (HbII-HbIII)-O2 species, leading to very low ligand dissociation rates. The results indicate that the oxy-hemeprotein is susceptible to pH from 4 to 9, at acidic conditions, and as a function of the potassium ferricyanide concentration, 100% of the met-aquo derivative is produced. Without a strong oxidant, pH 5 generates a small concentration of the met-aquo complex. The process is accelerated by the presence of salts, as indicated by the crystallization structures and UV–Vis spectra. The results suggest that acidic pH generates conformational changes associated with B10 and E7 heme pocket amino acids, weakening the (HbII-HbIII)-O2 hydrogen bond network. The observation is supported by X-ray crystallography, since at pH 4 and 5, the heme-Fe tends to oxidize, while at pH 7, the oxy-heterodimer is present. Conformational changes also are observed at higher pH by the presence of a 605 nm transition associated with the iron heme-Tyr interaction. Therefore, pH is one crucial factor regulating the (HbII-HbIII)-O2 complex hydrogen-bonding network. Thus, it can be proposed that the hydrogen bonding adjustments between the heme bound O2 and the Tyr and Gln amino acids contribute to oxygen dissociation from the (HbII-HbIII)-O2 system.

Compression-induced resistance of singlet oxygen dissociation on phosphorene

Owing to its unique material properties, monolayer phosphorene has been previously predicted to be useful in advancing rechargeable battery technology forward. However, practical applications of phosphorene are currently hindered due to its weak ambient stability stemming from oxygen dissociation. In this paper, using density functional theory-based calculations, the authors identified lattice compression as a promising approach towards inhibiting singlet O${}_{2}$ dissociation on phosphorene. This approach has the potential to significantly improve the ambient stability of phosphorene, and realize it as a material for developing green technologies.

In situ oxidation studies of Cu thin films: Growth kinetics and oxide phase evolution

A comprehensive understanding of the oxidation of Cu thin films in the low-temperature regime is of fundamental interest and particularly relevant for applications in the fields of micro- and nanoelectronics, sensors, catalysis, and solar cells. The current study reports on the oxidation kinetics of PVD grown Cu thin films (20–150 nm thick) and the oxide phase evolution from Cu2O to CuO upon thermal oxidation in the temperature range of 100–450 °C. XRD investigations in the laboratory and at the synchrotron show that the oxide phase formation critically depends on the oxidation conditions such as temperature and oxygen partial pressure. The real-time synchrotron XRD measurements reveal that the formation of the CuO phase only starts after complete oxidation of the Cu films to Cu2O films. In situ resistance measurements were performed to follow the oxide growth rate of Cu2O on Cu films in the temperature range of 100–300 °C in air and in 10 mbar pO2. It is found that the oxidation kinetics of Cu films to Cu2O films follows the linear rate law, which is attributed to surface reaction controlled oxidation. The oxygen dissociation rate at the gas–solid interface is the rate-limiting process. A dramatic decrease in the linear oxidation rate is observed at low oxygen partial pressures. The fundamental differences between the oxidation rate-limiting processes of Cu as compared to other transition metal films are discussed.

Should rcpaqap blood gas program include instrument calculated parameters?

A normal term baby girl was found to have low oxygen saturation on pulse oximeter (88–95%) on day 2 and did not respond to oxygen therapy. Cardio-pulmonary workup was uneventful. Arterial blood gas on room air revealed normal pH, pO2, pCO2, bicarbonate and sO2, but a high instrument-calculated p50 of 30–42 mmHg (RR 25–29) suggested a haemoglobin of low oxygen affinity. Haemoglobin HPLC analysis revealed an abnormal peak of 1.6% detected at RT 4.50 min which was shown by alkaline and acid electrophoresis, and subsequent DNA testing to be heterozygous HbA1:c.283G>A in the alpha1-globin gene (haemoglobin Titusville). This is a rare haemoglobinopathy involving a single nucleotide change from G to A at codon 94 of the alpha globin gene, and results in a lower oxygen affinity, indicated by oxygen dissociation curve right shift and high p50.1,2 While RCPAQAP Blood Gas program monitors key analyser measurements, there is no attempt to probe the performance of calculated parameters which may be determined by sophisticated hidden software, e.g., for p50. This case illustrates the importance of looking beyond the basic parameters of pH, pCO2, pO2 and bicarbonate and raises the desirability of RCPAQAP monitoring calculated parameters across various blood gas platforms which may be particularly vulnerable to haemoglobinopathies.3

A procedure for determining subject-specific pulse oxygen saturation response.

The oxyhemoglobin dissociation curve describes the relationship between the partial pressure of oxygen and the percent of hemoglobin saturated with oxygen and varies with chemical and physical factors that differ for every patient. If variability could be determined, patient-specific oxygen therapy could be administered. We have developed a procedure for characterizing variations in the oxygen dissociation curve. The purpose of this study was to validate this procedure in surgical patients. The procedure uses an automated system to alter oxygen therapy during surgery, within safe operational levels, and fit to Hill's equation non-invasive measurements of end-tidal oxygen and peripheral pulse oxygen saturation. The best-fit parameters for the Hill equation, estimated by iterative least squares, provide an apparent dissociation curve, meaningful of the patient-specific pulse oximeter response. Thirty-nine patients participated in this study. Using patient-specific parameter values increases correlation when compared with standard values. The procedure improved the model fit of patient saturation values significantly in 19 patients. This paper has demonstrated a procedure for determining patient-specific pulse oximeter response. This procedure determined best-fit parameters resulting in a significantly improved fit when compared with standard values. These best-fit parameters increased the coefficient of determination R2 in all cases. Graphical Abstract This patient-specific procedure improves fit significantly compared to standard estimates.

High-performance La0.5(Ba0.75Ca0.25)0.5Co0.8Fe0.2O3-δ cathode for proton-conducting solid oxide fuel cells

La0.5(Ba0.75Ca0.25)0.5Co0.8Fe0.2O3-δ, a simple perovskite cathode material with high electrical conductivity (940 S cm−1 at 600 °C) and impressive surface catalytic activity, was prepared and used in proton-conducting solid oxide fuel cells. As its thermal expansion coefficient is higher than that of the electrolyte material BaZr0.1Ce0.7Y0.1Yb0.1O3-δ, they were combined and used as a composite cathode. The crystal structure, chemical compatibility, electrical conductivity, cell performance, and the oxygen reduction reaction of the cathode material were explored, and we found that the single fuel cell developed with the composite cathode achieved excellent electrochemical performance, with both a low polarization resistance and high peak power density (0.044 Ω cm2 and 1102 mW cm−2 at 750 °C, respectively). Outstanding stability was also achieved, as indicated by a long-term 100-h test. Additionally, the rate-limiting steps of the oxygen reduction reaction were the oxygen adsorption, dissociation, and diffusion processes.