Theoretical study of two states reactivity of methane activation on iron atom and iron dimer

Density functional theory (DFT) calculations have been carried out to explore the catalytic activation of C–H bonds in methane by the iron atom, Fe, and the iron dimer, Fe2. For methane activation on an Fe atom, the calculations suggest that the activation of the first C–H bond is mediated via the triplet excited-state potential energy surface (PES), with initial excitation of Fe to the triplet state being necessary for the reaction to be energetically feasible. Compared with the breaking of the first C–H bond, the cleavage of the second C–H bond is predicted to involve a significantly higher barrier, which could explain experimental observations of the HFeCH3 complex rather than CH2FeH2 in the activation of methane by an Fe atom. For methane activation on an iron dimer, the cleavage of the first C–H bond is quite facile with a barrier only 11.2, 15.8 and 8.4 kcal/mol on the septet state energy surface at the B3LYP/6-311+G(2df,2dp), BPW91/6-311+G(2df,2dp) and M06/B3LYP level, respectively. Cleavage of the second C–H bond from HFe2CH3 involves a barrier calculated respectively as 18.0, 10.7 and 12.4 kcal/mol at the three levels. The results suggest that the elimination of hydrogen from the dihydrogen complex is a rate-determining step. Overall, our results indicate that the iron dimer Fe2 has a stronger catalytic effect on the activation of methane than the iron atom.

Ozone-Induced Dissociation on a Modified Tandem Linear Ion-Trap : Observations of Different Reactivity for Isomeric Lipids

Ozone-induced dissociation (OzID) exploits the gas-phase reaction between mass-selected lipid ions and ozone vapor to determine the position(s) of unsaturation In this contribution, we describe the modification of a tandem linear ion-trap mass spectrometer specifically for OzID analyses wherein ozone vapor is supplied to the collision cell This instrumental configuration provides spatial separation between mass-selection, the ozonolysis reaction, and mass-analysis steps in the OzID process and thus delivers significant enhancements in speed and sensitivity (ca 30-fold) These improvements allow spectra revealing the double-bond position(s) within unsaturated lipids to be acquired within 1 s significantly enhancing the utility of OzID in high-throughput lipidomic protocols The stable ozone concentration afforded by this modified instrument also allows direct comparison of relative reactivity of isomeric lipids and reveals reactivity trends related to (1) double-bond position, (2) substitution position on the glycerol backbone, and (3) stereochemistry For cis- and trans-isomers, differences were also observed in the branching ratio of product ions arising from the gas-phase ozonolysis reaction, suggesting that relative ion abundances could be exploited as markers for double-bond geometry Additional activation energy applied to mass-selected lipid ions during injection into the collision cell (with ozone present) was found to yield spectra containing both OzID and classical-CID fragment ions This combination CID-OzID acquisition on an ostensibly simple monounsaturated phosphatidylcholine within a cow brain lipid extract provided evidence for up to four structurally distinct phospholipids differing in both double-bond position and sn-substitution U Am Soc Mass Spectrom 2010, 21, 1989-1999) (C) 2010 American Society for Mass Spectrometry

Adolescent pedometer protocols : examining reactivity, tampering and participants' perceptions

The aim of this study was to investigate adolescents' potential reactivity and tampering while wearing pedometers by comparing different monitoring protocols to accelerometer output. The sample included adolescents (N=123, age range=14-15 years) from three secondary schools in New South Wales, Australia. Schools were randomised to one of the three pedometer monitoring protocols: (i) daily sealed (DS) pedometer group, (ii) unsealed (US) pedometer group or (iii) weekly sealed (WS) pedometer group. Participants wore pedometers (Yamax Digi-Walker CW700, Yamax Corporation, Kumamoto City, Japan) and accelerometers (Actigraph GT3X+, Pensacola, USA) simultaneously for seven days. Repeated measures analysis of variance was used to examine potential reactivity. Bivariate correlations between step counts and accelerometer output were calculated to explore potential tampering. The correlation between accelerometer output and pedometer steps/day was strongest among participants in the WS group (r=0.82, P <= 0.001), compared to the US (r=0.63, P <= 0.001) and DS (r=0.16, P=0.324) groups. The DS (P <= 0.001) and US (P=0.003), but not the WS (P=0.891), groups showed evidence of reactivity. The results suggest that reactivity and tampering does occur in adolescents and contrary to existing research, pedometer monitoring protocols may influence participant behaviour.

Investigation of the gas phase reactivity of the 1-adamantyl radical using a distonic radical anion approach

The gas phase reactions of the bridgehead 3-carboxylato-1-adamantyl radical anion were observed with a series of neutral reagents using a modified electrospray ionisation linear ion trap mass spectrometer. This distonic radical anion was observed to undergo processes suggestive of radical reactivity including radical-radical combination reactions, substitution reactions and addition to carbon-carbon double bonds. The rate constants for reactions of the 3-carboxylato-1-adamantyl radical anion with the following reagents were measured ( in units 10(-12) cm(3) molecule(-1) s(-1)): O-18(2) ( 85 +/- 4), NO ( 38.4 +/- 0.4), I-2 ( 50 +/- 50), Br-2 ( 8 +/- 2), CH3SSCH3 ( 12 +/- 2), styrene ( 1.20 +/- 0.03), CHCl3 ( H abstraction 0.41 +/- 0.06, Cl abstraction 0.65 +/- 0.1), CDCl3 ( D abstraction 0.035 +/- 0.01, Cl abstraction 0.723 +/- 0.005), allyl bromide (Br abstraction 0.53 +/- 0.04, allylation 0.25 +/- 0.01). Collision rates were calculated and reaction efficiencies are also reported. This study represents the first quantitative measurement of the gas phase reactivity of a bridgehead radical and suggests that distonic radical anions are good models for the study of their elusive uncharged analogues.

Interface control of surface photochemical reactivity in ultrathin epitaxial ferroelectric films

Asymmetrical electrical boundary conditions in (001)-oriented Pb(Zr 0.2TiO0.8)O3 (PZT) epitaxial ultrathin ferroelectric films are exploited to control surface photochemical reactivity determined by the sign of the surface polarization charge. It is shown that the preferential orientation of polarization in the as-grown PZT layer can be manipulated by choosing an appropriate type of bottom electrode material. PZT films deposited on the SrRuO3 electrodes exhibit preferential upward polarization (C) whilst the same films grown on the (La,Sr)CoO 3-electrodes are polarized downward (C-). Photochemical activity of the PZT surfaces with different surface polarization charges has been tested by studying deposition of silver nanoparticles from AgNO3 solution under UV irradiation. PZT surfaces with preferential C orientation possess a more active surface for metal reduction than their C- counterparts, evidenced by large differences in the concentration of deposited silver nanoparticles. This effect is attributed to band bending at the bottom interface which varies depending on the difference in work functions of PZT and electrode materials.

Functional immunoglobulin E cross-reactivity between Pas n 1 of Bahia grass pollen and other group 1 grass pollen allergens

Background Grass pollens are major triggers of allergic rhinitis and asthma, but the immunological relationships between pollen allergens of the subtropical Bahia grass, Paspalum notatum, and temperate grasses are unresolved. Objective To assess serum IgE cross-reactivity between subtropical P. notatum and temperate Lolium perenne (Ryegrass) pollen allergens. Methods Serum IgE reactivities of grass pollen-allergic patients with P. notatum, L. perenne and Cynodon dactylon (Bermuda grass) pollen extracts and their respective purified group 1 allergens, Pas n 1, Lol p 1 and Cyn d 1, were compared by immunoblotting, ELISA and basophil activation. Results In a cohort of 51 patients from a temperate region, a high frequency of IgE reactivity with each grass pollen was detected, but reactivity with L. perenne pollen was substantially greater than with P. notatum and C. dactylon pollen. Similarly, serum IgE reactivity with Lol p 1 was greater than with Pas n 1 or Cyn d 1. For seven of eight sera studied in detail, asymmetric serum IgE cross-reactivity was observed; L. perenne pollen inhibited IgE reactivity with P. notatum pollen but not the converse, and IgE reactivity with Pas n 1 was inhibited by Lol p 1 but IgE reactivity with Lol p 1 was not inhibited by Pas n 1 or Cyn d 1. Importantly, P. notatum pollen and Pas n 1 activated basophils in grass pollen-allergic patients from a temperate region, although stimulation was greater by pollen of L. perenne than P. notatum or C. dactylon, and by Lol p 1 than Pas n 1 or Cyn d 1. In contrast, a cohort of 47 patients from a subtropical region showed similar IgE reactivity with P. notatum and L. perenne pollen, and reciprocal cross-inhibition of IgE reactivity between L. perenne and P. notatum. Conclusions Pollen allergens of the subtropical P. notatum, including Pas n 1, show clinically relevant IgE cross-reactivity with pollen allergens of L. perenne but also species-specific IgE reactivity.

IgE cross-reactivity between Pas n 1 of Bahia grass pollen and other group 1 grass pollen allergens

Background The subtropical Bahia grass (Paspalum notatum) is an important source of pollen allergens with an extended season of pollination and wide distribution in warmer climates. The immunological relationship between pollen allergens of Bahia grass and temperate grasses is unresolved. Methods Serum IgE reactivity of grass pollen-allergic patients with Bahia, Ryegrass and Bermuda grass pollen extracts and their purified group 1 allergens, Pas n 1, Lol p 1 and Cyn d 1, were compared by immunoblotting, ELISA, inhibition ELISA, basophil activation by flow cytometry and molecular modeling. Results Differences in antibody recognition of allergenic components between Bahia grass and Ryegrass pollen were observed by immunoblotting. Eight grass pollen-allergic patients from a temperate region showed greater serum IgE reactivity with Ryegrass pollen than Bahia grass by ELISA. For seven of these sera, Ryegrass pollen inhibited IgE reactivity with Bahia grass pollen but not the converse. For 51 sera from grass pollen-allergic patients in this temperate region, IgE reactivity with Lol p 1 was greater than Pas n 1 or Cyn d 1. IgE reactivity with Lol p 1 was not inhibited by Pas n 1 or Cyn d 1, but Pas n 1 IgE reactivity was inhibited by Lol p 1. Two group 1 grass pollen allergen-specific mAb distinguished between temperate and subtropical grass pollens. Basophil activation for three patients tested was greater by Ryegrass pollen than Bahia or Bermuda grass, and by Lol p 1 than Pas n 1 or Cyn d 1. In contrast, two patients from a subtropical region had higher serum IgE reactivity with Bahia grass pollen than Ryegrass and Bahia grass pollen inhibited IgE reactivity with Ryegrass. A structural model of Pas n 1 showed amino acids implicated in IgE epitopes of other group 1 allergens were juxtaposed on the surface. Conclusion Allergens from subtropical Bahia grass pollen, including Pas n 1, share antigenic determinants with temperate grass pollen allergens, but patients exhibit higher serum IgE reactivity to their locally predominant grass pollen. Basophil activation by Bahia grass pollen and Pas n 1 in patients from a temperate climate indicates clinically relevant cross-sensitization between temperate and subtropical grass pollens.

Bahia grass pollen specific IgE is common in seasonal rhinitis patients but has limited cross-reactivity with Ryegrass

Background: Perennial Ryegrass is a major cause of rhinitis in spring and early summer. Bahia grass, Paspalum notatum, flowers late into summer and could account for allergic rhinitis at this time. We determined the frequency of serum immunoglobulin (Ig)E reactivity with Bahia grass in Ryegrass pollen allergic patients and investigated IgE cross-reactivity between Bahia and Ryegrass. Methods: Serum from 33 Ryegrass pollen allergic patients and 12 nonatopic donors were tested for IgE reactivity with Bahia and Ryegrass pollen extracts (PE) by enzyme-linked immunosorbent assay (ELISA), western blotting and inhibition ELISA. Allergen-specific antibodies from a pool of sera from allergic donors were affinity purified and tested for IgE cross-reactivity. Results: Seventy-eight per cent of the sera had IgE reactivity with Bahia grass, but more weakly than with Ryegrass. Antibodies eluted from the major Ryegrass pollen allergens, Lol p 1 and Lol p 5, showed IgE reactivity with allergens of Ryegrass and Canary but not Bahia or Bermuda grasses. Timothy, Canary and Ryegrass inhibited IgE reactivity with Ryegrass and Bahia grass, whereas Bahia, Johnson and Bermuda grass did not inhibit IgE reactivity with Ryegrass. Conclusions: The majority of Ryegrass allergic patients also showed serum IgE reactivity with Bahia grass PE. However, Bahia grass and Ryegrass had only limited IgE cross-reactivity indicating that Bahia grass should be considered in diagnosis and treatment of patients with hay fever late in' the grass pollen season.

Antibody reactivity to the transmembrane protein of the caprine arthritis encephalitis virus correlates with severity of arthritis: No evidence for the involvement of epitope mimicry

Serum and synovial antibody reactivities of caprine arthritis encephalitis virus (CAEV) infected goats were assessed by Western blotting against purified CAEV antigen and the greatest intensity of reactivity in the serum of arthritic goats was to the gp45 transmembrane protein (TM). The extracytoplasmic domain of the TM gene was cloned into a pGEX vector and expressed in Escherichia coil as a glutathione S transferase fusion protein (GST-TM). This clone was found to be 90.5 and 89.2% homologous to published sequences of CAEV TM gene. Serum of 16 goats naturally infected with CAEV were examined by Western blotting for reactivity to the fusion protein. Antibody reactivity to the GST-TM correlated with clinically detectable arthritis (R = 0.642, P ≤ 0.007). The hypothesis that the immune response to the envelope proteins of the CAEV contributes to the severity of arthritis in goats naturally infected with CAEV via epitope mimicry was tested. Antibodies from 5 CAEV infected goats were affinity purified against the GST-TM fusion protein and tested for cross-reactivity with a series of goat synovial extracts and proteogylcans. No serum antibody response or cross-reactivity of affinity purified antibodies could be detected. Peptides of the CAEV SU that were predicted to be linear epitopes and a similar heat shock protein 83 (HSP) peptide identified by database searching, were synthesized and tested for reactivity in CAEV goats using ELISA, in vitro lymphocyte proliferation and delayed type hypersensitivity (DTH) assays. Peripheral blood lymphocytes from 10 of 17 goats with long term natural CAEV infections proliferated in vitro in response to CAEV and in vivo 3 of 7 CAEV infected goats had a DTH reaction to CAEV antigen. However, none of the peptides elicited significant cell mediated immune responses from CAEV infected goats. No antibody reactivity to the SU peptides or HSP peptide was found. We observed that the antibody reactivity to the CAEV TM protein associated with severity of arthritis however epitope mimicry by the envelope proteins of CAEV is unlikely to be involved.

An experimental study on anisotropic mechanical properties of porcine thoracic aorta

Objective: To study the anisotropic mechanical properties of the thoracic aorta in porcine. Methods: Twenty-one porcine thoracic aortas were collected and categorized into three groups. The aortas were then cut through in their axial directions and expanded into two-dimensional planes. Then, by setting the length direction of the planar aortas (i.e., axial directions of the aortas) as 0°, each planar aorta was counterclockwisely cut into 8 samples with orientation of 30°, 45°, 60°, 90°, 120°, 135°, 150° and 180°, respectively. Finally, the uniaxial tensile tests were applied on three groups of samples at the loading rates of 1, 5 and 10 mm/min, respectively, to obtain the elastic modulus and ultimate stress of the aorta in different directions and at different loading rates. Results: The stress-strain curves exhibited different viscoelastic behaviors. With the increase of sample orientations, the elastic modulus gradually increased from 30°, reached the maximum value at 90°, and then gradually decreased till 180°. The variation trend of ultimate stress was similar to that of elastic modulus. Moreover, different loading rates showed a significant influence on the results of elastic modulus and ultimate stress, but a weak influence on the anisotropic degree. Conclusions: The porcine thoracic aorta is highly anisotropic. This research finding provides parameter references for assignment of material properties in finite element modeling, and is significant for understanding biomechanical properties of the arteries.

Vibrational spectroscopy of intercalated kaolinites. Part I

The industrial application of kaolinite is closely related to its reactivity and surface properties. The reactivity of kaolinite can be tested by intercalation, i.e. via the insertion of low molecular weight organic compounds between the kaolinite layers resulting in the formation of a nano-layered organo-complex. Although intercalation of kaolinite is an old and ongoing research topic, there is a limited knowledge available on the reactivity of different kaolinites, the mechanism of complex formation as well as on the structure of the complexes formed. Grafting and incorporation of exfoliated kaolinite in polymer matrices and other potential applications can open new horizons in the study of kaolinite intercalation. This paper attempts to summarize (without completion) the most recent achievements in the study of kaolinite organo-complexes obtained with the most common intercalating compounds like urea, potassium acetate, dimethyl sulphoxide, formamide and hydrazine using vibrational spectroscopy combined with X-ray powder diffraction and thermal analysis.

Role of low affinity beta1-adrenergic receptors in normal and diseased hearts

ROLE OF LOW AFFINITY β1-ADRENERGIC RECEPTOR IN NORMAL AND DISEASED HEARTS Background: The β1-adrenergic receptor (AR) has at least two binding sites, 1HAR and 1LAR (high and low affinity site of the 1AR respectively) which cause cardiostimulation. Some β-blockers, for example (-)-pindolol and (-)-CGP 12177 can activate β1LAR at higher concentrations than those required to block β1HAR. While β1HAR can be blocked by all clinically used β-blockers, β1LAR is relatively resistant to blockade. Thus, chronic β1LAR activation may occur in the setting of β-blocker therapy, thereby mediating persistent βAR signaling. Thus, it is important to determine the potential significance of β1LAR in vivo, particularly in disease settings. Method and result: C57Bl/6 male mice were used. Chronic (4 weeks) β1LAR activation was achieved by treatment with (-)-CGP12177 via osmotic minipump. Cardiac function was assessed by echocardiography and catheterization. (-)-CGP12177 treatment in healthy mice increased heart rate and left ventricular (LV) contractility without detectable LV remodelling or hypertrophy. In mice subjected to an 8-week period of aorta banding, (-)-CGP12177 treatment given during 4-8 weeks led to a positive inotropic effect. (-)-CGP12177 treatment exacerbated LV remodelling indicated by a worsening of LV hypertrophy by ??% (estimated by weight, wall thickness, cardiomyocyte size) and interstitial/perivascular fibrosis (by histology). Importantly, (-)-CGP12177 treatment to aorta banded mice exacerbated cardiac expression of hypertrophic, fibrogenic and inflammatory genes (all p<0.05 vs. non-treated control with aorta banding).. Conclusion: β1LAR activation provides functional support to the heart, in both normal and diseased (pressure overload) settings. Sustained β1LAR activation in the diseased heart exacerbates LV remodelling and therefore may promote disease progression from compensatory hypertrophy to heart failure. Word count: 270

Modelling photochemical production of fine particulates in a toluene/NOx/water vapour system

This work investigates the computer modelling of the photochemical formation of smog products such as ozone and aerosol, in a system containing toluene, NOx and water vapour. In particular, the problem of modelling this process in the Commonwealth Scientific and Industrial Research Organization (CSIRO) smog chambers, which utilize outdoor exposure, is addressed. The primary requirement for such modelling is a knowledge of the photolytic rate coefficients. Photolytic rate coefficients of species other than N02 are often related to JNo2 (rate coefficient for the photolysis ofN02) by a simple factor, but for outdoor chambers, this method is prone to error as the diurnal profiles may not be similar in shape. Three methods for the calculation of diurnal JNo2 are investigated. The most suitable method for incorporation into a general model, is found to be one which determines the photolytic rate coefficients for N02, as well as several other species, from actinic flux, absorption cross section and quantum yields. A computer model was developed, based on this method, to calculate in-chamber photolysis rate coefficients for the CSIRO smog chambers, in which ex-chamber rate coefficients are adjusted by accounting for variation in light intensity by transmittance through the Teflon walls, albedo from the chamber floor and radiation attenuation due to clouds. The photochemical formation of secondary aerosol is investigated in a series of toluene-NOx experiments, which were performed in the CSIRO smog chambers. Three stages of aerosol formation, in plots of total particulate volume versus time, are identified: a delay period in which no significant mass of aerosol is formed, a regime of rapid aerosol formation (regime 1) and a second regime of slowed aerosol formation (regime 2). Two models are presented which were developed from the experimental data. One model is empirically based on observations of discrete stages of aerosol formation and readily allows aerosol growth profiles to be calculated. The second model is based on an adaptation of published toluene photooxidation mechanisms and provides some chemical information about the oxidation products. Both models compare favorably against the experimental data. The gross effects of precursor concentrations (toluene, NOx and H20) and ambient conditions (temperature, photolysis rate) on the formation of secondary aerosol are also investigated, primarily using the mechanism model. An increase in [NOx]o results in increased delay time, rate of aerosol formation in regime 1 and volume of aerosol formed in regime 1. This is due to increased formation of dinitrocresol and furanone products. An increase in toluene results in a decrease in the delay time and an increase in the rate of aerosol formation in regime 1, due to enhanced reactivity from the toluene products, such as the radicals from the photolysis of benzaldehyde. Water vapor has very little effect on the formation of aerosol volume, except that rates are slightly increased due to more OH radicals from reaction with 0(1D) from ozone photolysis. Increased temperature results in increased volume of aerosol formed in regime 1 (increased dinitrocresol formation), while increased photolysis rate results in increased rate of aerosol formation in regime 1. Both the rate and volume of aerosol formed in regime 2 are increased by increased temperature or photolysis rate. Both models indicate that the yield of secondary particulates from hydrocarbons (mass concentration aerosol formed/mass concentration hydrocarbon precursor) is proportional to the ratio [NOx]0/[hydrocarbon]0