Existence Of Oxygen Atoms Research Articles

First report on chemometrics-driven multilayered lead prioritization in addressing oxysterol-mediated overexpression of G protein-coupled receptor 183.

Contemporary research has convincingly demonstrated that upregulation of G protein-coupled receptor 183 (GPR183), orchestrated by its endogenous agonist, 7α,25-dihydroxyxcholesterol (7α,25-OHC), leads to the development of cancer, diabetes, multiple sclerosis, infectious, and inflammatory diseases. A recent study unveiled the cryo-EM structure of 7α,25-OHC bound GPR183 complex, presenting an untapped opportunity for computational exploration of potential GPR183 inhibitors, which served as our inspiration for the current work. A predictive and validated two-dimensional QSAR model using genetic algorithm (GA) and multiple linear regression (MLR) on experimental GPR183 inhibition data was developed. QSAR study highlighted that structural features like dissimilar electronegative atoms, quaternary carbon atoms, and CH2RX fragment (X: heteroatoms) influence positively, while the existence of oxygen atoms with a topological separation of 3, negatively affects GPR183 inhibitory activity. Post assessment of true external set prediction capability, the MLR model was deployed to screen 12,449 DrugBank compounds, followed by a screening pipeline involving molecular docking, druglikeness, ADMET, protein-ligand stability assessment using deep learning algorithm, molecular dynamics, and molecular mechanics. The current findings strongly evidenced DB05790 as a potential lead for prospective interference of oxysterol-mediated GPR183 overexpression, warranting further in vitro and in vivo validation.

Atomistic study of adhesion of PU/PTFE coating on aluminium oxide surface

ABSTRACT The effectiveness of coatings depends upon various factors and adhesion of the coating to a metallic surface is one of them. Polyurethane (PU) and polytetrafluoroethylene (PTFE) are widely used polymeric coatings for the protection of metallic surfaces. The adhesion of PU and PTFE films on the aluminium oxide substrate is investigated by employing MD simulations. The effect of temperature variation on both the polymeric films has been also studied. Results depict that as the temperature increases the adhesion energy of both the polymers increases in the range from 273.15 K to 298 K. However, there is no such applications of these polymeric coatings at higher temperature like 548 K, the interaction energy is also calculated at 548 K to predict the behaviour of these polymers at elevated temperatures. PU was found to be more thermally stable compared to PTFE. Moreover, PU adhesion with the aluminium oxide surface was much greater when compared to PTFE which possibly resulted from the existence of oxygen atoms in PU which are responsible for greater adhesion between polymer and metal surface.

Unraveling the unique role of brown graphitic carbon nitride in robust CO2 photoreduction

Photocatalytic CO2 reduction is one of the important means to alleviate the energy crisis. In this work, an oxygen-linked and brown graphitic carbon nitride (GACN) was successfully prepared by thermal polymerization after oil bath method. GACN introduced oxygen atoms on surface of BulkCN. Various characterizations of the material show that the prepared GACN has a different structure and higher photoelectronic activity compared to BulkCN. GACN possessed strong photocatalytic CO2 reduction capacity, and the photocatalytic activity was significantly improved compared with BulkCN. In view of density functional theory calculations, it is proved that the oxygen atoms introduced by GACN increase CO2 photoreaction reactivity, enhance electronic activity and reduce the reaction energy barrier. This work can have a positive effect on the photocatalytic application of g-C3N4 with the existence of oxygen atoms.

Adsorption of a Pt13 Cluster on Graphene Oxides at Varied Ratios of Oxygen to Carbon and Its Catalytic Reactions for CO Removal Investigated with Quantum-Chemical Calculations

We applied periodic density-functional theory to investigate the interaction of a Pt13 cluster on graphene oxide (GO) sheets at varied ratios of oxygen to carbon and on a pristine graphene sheet. Relative to a pristine graphene sheet, the existence of oxygen atoms in an appropriate proportion in the formation of graphene oxide enhanced the adsorption capability of a Pt13 cluster. The O/C ratio of GO sheets had the following influences on the Pt13 cluster adsorption behavior: (i) for O/C ratio < 0.125, the Pt13 cluster abstracted the neighboring oxygen atom from a GO sheet to form Pt13O, or aggregated with an adjacent cluster to form a larger cluster; (ii) for O/C ratio ≥ 0.125, the Pt13 cluster was stabilized and dispersed on the GO sheet. We calculated also the adsorption behavior of carbon monoxide on a Pt13/GO sheet; a strong interaction between the Pt13 cluster and the GO sheet modulated the electronic structure of the Pt13 cluster, thus decreasing the CO adsorption energy, which in turn decreased the combined barriers, CO + O and CO + OH, in the water-gas shift reaction (WGSR) and improved the CO tolerance of the Pt catalyst.

Mechanism of ammonia decomposition on clean and oxygen-covered Cu (1 1 1) surface: A DFT study

Employing density functional theory (DFT), the adsorption and dehydrogenation mechanism of ammonia on clean and O-covered Cu (111) surfaces have been studied systematically. Different adsorption geometries were investigated for NH3 and related intermediates. In addition, the stable co-adsorption configurations for the relevant co-adsorption groups were identified. The projected density of states (DOS) were calculated to understand the interaction between NHx (x=1, 3) species and Cu (111) surface and investigate the effect of oxygen atom on adsorption. Finally, transition states, energy barriers and reaction energies were determined to confirm the mechanism of dehydrogenation of NH3 on clean and oxygen-covered Cu (111) surfaces. It was shown that NH is the most abundant intermediate on clean and O-covered Cu (111) surface due to the highest energy barrier, suggesting the dehydrogenation of NH group is the rate-determining step in the overall reaction. Furthermore, the existence of oxygen atom can reduce the energy barriers drastically and promote the decomposition of NHx (x=1–3), indicating that ammonia decomposition is more favorable on oxygen-covered Cu (111) surface.

Pyrolysis behaviors of two coal-related model compounds on a fixed-bed reactor

The bibenzyl (BB) and benzyloxybenzene (BOB) were selected as coal-related model compounds, and their pyrolysis behaviors between 500°C and 700°C were investigated on a fixed-bed reactor. The pyrolysis products were analyzed by gas chromatography–mass spectrometer (GC–MS) and gas chromatography (GC), and the bond dissociation energy (BDE) was calculated with density functional theory (DFT) methods at B3LYP/6-31G (d) level. The results showed that the conversion in pyrolysis of BOB was higher than that of BB. The pyrolysis product distributions and BDE calculation indicate that Caliphatic–Caliphatic bond dissociation is the primary step for BB pyrolysis, while Caliphatic–O bond dissociation is the primary step for BOB pyrolysis. The differences in pyrolysis behaviors between BB and BOB indicate that the existence of oxygen atom will reduce the BDE thus being preferentially dissociated under pyrolysis. The initial radicals should be stabilized by some more reactive radicals, which lead to higher liquid yield.

Fabricating and improving properties of copper matrix nanocomposites by electroless copper-coated MWCNTs

In this study, copper (Cu) nanocomposites reinforced by coated multiwall carbon nanotubes (MWCNTs) have been fabricated with different weight fractions of MWCNT. In the first step, the as-received MWCNTs were coated with Cu using electroless deposition process. In the next step, combination of sonication and ball milling (with two milling time of 1.5 and 3 h) was used for preparing MWCNT/Cu composite powders. Finally, the disk-shaped specimens were sintered by hot-press sintering machine. Characterization of sintered nanocomposites revealed that increasing milling time led to improved mechanical properties, but higher defect density on the MWCNT sidewalls is obtained which is especially undesirable for electrical properties of nanocomposite. Our results indicated that simultaneous improvements of interface reactions and distribution uniformity of MWCNTs and Cu are key factors for obtaining enhanced mechanical properties. Accordingly, enhancement of up to ~150 and ~86 % in microhardness compared to pure Cu and 1 wt% as-received MWCNT/Cu was achieved by addition of 1 wt% Cu-coated MWCNT. On the contrary, existence of oxygen atoms in the Cu and coated MWCNT interface (from functional groups and deposited copper oxide) obstructs considerable improvement of electrical resistivity compared to as-received MWCNT/Cu nanocomposites.

Old but new methods in radiation oncology

Shortly after the extraordinary discovery of X-rays by Roentgen in 1895, radiation therapy was introduced [1]. During the early period of radiation treatment the methods were primitive; however, because of the development of unique devices, radiation therapy plays an important role in cancer treatment today. In the long history of radiation therapy, numerous treatment modalities have been proposed and tested; some are used in modern treatments, while others are not. Oxygen plays an important role in cell death by radiation [2]. Radiation biologists demonstrated that the existence of oxygen atoms during photon irradiation was essential to eradicate cells effectively. When the oxygen partial pressure is \2.5 mmHg, it is necessary to increase radiation by at least 2–3 times to achieve the same effects as in sufficiently oxygenated cells. Thomlinson and Gray [3] observed that tumor tissue 70–100 lm from capillaries showed necrosis. They concluded that tumor cells could proliferate only if they were close to a supply of oxygen. Between the actively proliferating cells and necrotic cells, there should be hypoxic but not dead cells; these cells are called chronically or diffusional hypoxic cells. Subsequently, Brown [4] determined that there were also hypoxic cells in actively growing tumors. The bloodstream in tumor vessels is temporarily blocked, because the vessels in such tumors are usually malformed; this phenomenon is called acute or perfusional hypoxia. To overcome the radio-resistance of these hypoxic cells, several methods, including hyperbaric oxygen, normobaric oxygen inhalation and administration of nitroazole hypoxic radiosensitizers, have been proposed. However, none of these methods are used in the clinic in Japan at this time. Many clinical trials to test the effect of these methods have been performed, but only a few showed positive results. Radiation therapy during respiration of hyperbaric oxygen is complicated and dangerous, because oxygen promotes rapid combustion/explosion. Overgaard [5] recently demonstrated in a meta-analysis that all of these 3 treatment modalities were significantly effective in clinical tests and that hyperbaric oxygen treatment was the most efficient among them. Ogawa et al. [6] review the newly developed and promising hyperbaric oxygen therapy in this issue. Their method is simple, safe and effective for overcoming radio-resistance of hypoxic cells. Hyperbaric oxygen therapy is also useful in the treatment of chronic radiation damage, such as osteomyelitis, cystitis, proctitis and central and peripheral nerve injuries. Unfortunately, this noninvasive therapy is not well known in Japan. Ogawa et al. [6] also demonstrate the effect and indications of the treatment in the same review. One of the first systematic and elegant treatment methods in radiation oncology was the mantle and inverted-Y field-radiation therapy for Hodgkin’s lymphoma, which was developed by Kaplan et al. [7]. Hodgkin’s lymphoma was a fatal disease in Europe and the US before the 1950s. In the early 20th century, Peters et al. developed systemic lymph node treatment for this disease and achieved good treatment results. By introducing a newly developed treatment machine, a linear accelerator (LINAC), into this field, Kaplan and colleagues created a systematic radiation technique, and this was a standard treatment for this lifethreatening disease until around 1990. After the discovery of X-rays and radioisotopes, many investigators died of radiation-induced malignancies. The K. Sasai (&) Department of Radiation Oncology, Juntendo University, Hongo 2-1-1, Bunkyo, Tokyo 113-8421, Japan e-mail: ksasai@juntendo.ac.jp

Electronic Structure of Hydrogenated and Surface-Modified GaAs Nanocrystals: Ab Initio Calculations

Two methods are used to simulate electronic structure of gallium arsenide nanocrystals. The cluster full geometrical optimization procedure which is suitable for small nanocrystals and large unit cell that simulates specific parts of larger nanocrystals preferably core part as in the present work. Because of symmetry consideration, large unit cells can reach sizes that are beyond the capabilities of first method. The two methods use ab initio Hartree-Fock and density functional theory, respectively. The results show that both energy gap and lattice constant decrease in their value as the nanocrystals grow in size. The inclusion of surface part in the first method makes valence band width wider than in large unit cell method that simulates the core part only. This is attributed to the broken symmetry and surface passivating atoms that split surface degenerate states and adds new levels inside and around the valence band. Bond length and tetrahedral angle result from full geometrical optimization indicate good convergence to the ideal zincblende structure at the centre of hydrogenated nanocrystal. This convergence supports large unit cell methodology. Existence of oxygen atoms at nanocrystal surface melts down density of states and reduces energy gap.

Propriétés de solvation des solutions concentrées en acide phosphorique

Solvation properties of ions inH2O–H3PO4 media (1–14 M) are characterized with their solvation transfer activity coefficients f. These are calculated from normal potential or solubility values, and indicate an increasing solvation for anions and decreasing solvation for cations in concentrated acid solutions. For each species, the range depends on its number of charges, on the existence of oxygen atoms in its structure, and on its basic properties. The consequences of variation of solvation on oxidation–reduction reactions and solubility properties are studied.

On the New Absorption Bands of the Oxygen Molecule in the Far Ultraviolet Region

The absorption bands of the oxygen molecule in the extreme ultraviolet region were studied using a 3-meter grazing incidence vacuum spectrograph. Two new progressions of bands were found in the region between 1200A and 1290A (one of which is considered to be a member of the Rydberg series converging to the first ionization potential of the oxygen molecule). There were also observed a few short continua near the short wavelength end of the Schumann-Runge absorption continuum. The behavior of three strong and diffuse bands, at 1200∼1290A, were studied at pressures ranging from 0.01 to several mm of Hg. Assuming the diffuseness of these bands as being due to predissociation, the existence of oxygen atoms in 1S metastable states in the upper atmosphere is briefly discussed.