Presence Of C2 Research Articles

Inhibition of staphylococcal nuclease by benzimidazole-based Ligand: Implications in DNA-Mediated entrapment and uptake of MRSA by Macrophage-like cells

The staphylococcal nuclease also referred as micrococcal nuclease (MNase) is a key drug target as the enzyme degrades the neutrophil extracellular trap (NET) and empowers the pathogen to subvert the host innate immune system. To this end, the current study presents a critical evaluation of MNase inhibition rendered by benzimidazole-based ligands (C1 and C2) and probes its therapeutic implications. A nuclease assay indicated that MNase inhibition rendered by C1 and C2 was ∼ 55 % and ∼ 72 %, respectively, at the highest tested concentration of 10 µM. Studies on enzyme kinetics revealed that C2 rendered non-competitive inhibition and significantly reduced MNase turnover number (Kcat) and catalytic efficiency (Kcat/Km) with an IC50 value of ∼ 1122 nM. In CD spectroscopy, a notable perturbation in the β-sheet content of MNase was observed in presence of C2. Fluorescence-microscope analysis indicated that MNase inhibition by C2 could restore entrapment of methicillin-resistant Staphylococcus aureus (MRSA) in calf-thymus DNA (CT-DNA). Flow cytometry and confocal microscope analysis revealed that uptake of DNA-entrapped MRSA by activated THP-1 cells was reinstated by MNase inhibition rendered by C2. Inhibition of nuclease by the non-toxic ligand C2 holds therapeutic prospect as it has the potential to bolster the DNA-mediated entrapment machinery and mitigate MRSA infections.

Determination of the pressure and composition of wet gas fluid inclusions: An in situ Raman spectroscopic approach

Carbonaceous fluid within mineral-hosted inclusions provides important information for carbon cycle in deep Earth. In addition to CH4 and CO2, heavy hydrocarbons (e.g., C2H6 and C3H8) are frequently observed in carbonaceous fluid inclusions (i.e, wet gas inclusions with C1/∑Ci < 0.95). However, determination of the composition of such complex volatiles is difficult based on traditional microthermometric measurements. Here we carried out experimental calibrations on Raman spectroscopic measurements of the pressure (P) and composition of the CH4 ± C2H6 ± C3H8 ± H2S system at room temperature and 0.1–130 MPa. We confirmed that the C–H symmetric stretching vibration band of CH4 [ν1(CH4), ∼2917 cm−1] shifted to lower wavenumber with rising pressure, thus the P-ν1(CH4) relationship could be applied to calculate the pressure of wet gas. It should be noted that the presence of C2+ and/or H2S will shift the [ν1(CH4)] to lower wavenumber at constant pressure (with the order of C3H8 ≥ H2S > C2H6). Obviously, the P-ν1(CH4) relationship derived from pure CH4 system could not be simply applied to wet gas inclusion, otherwise the pressure would be overestimated. To avoid the overlap of the C–H vibrations of CH4, C2H6 and C3H8, the peak areas and peak heights of the overtone vibration of CH4 [2ν4(CH4), ∼2580 cm−1], C–C symmetric stretching vibrations of C2H6 [ν3(C2H6), ∼995 cm−1] and C3H8 [ν8(C3H8), ∼868 cm−1], and S–H symmetric stretching vibration of H2S [ν1(H2S), ∼2612 cm−1] were fitted using Gaussian + Lorentz functions. The obtained peak areas and peak heights were then used to calculate the Raman quantification factors (F factor and G factor, respectively) of C2H6, C3H8 and H2S relative to CH4, respectively. Both the F factor and G factor increased with rising pressure, whereas the FC2H6, FC3H8 and GH2S kept nearly constant at ∼5.69, 6.39 and 153.8, respectively in high pressure gas mixtures (e.g., >30 MPa). Therefore, for inclusions with higher internal pressure, the molar ratio of CH4, C2H6, C3H8 and H2S could be determined by the aforementioned F and G factors. This method was applied to the calcite-hosted single-phase gas inclusions in the Upper Permian Changxing Formation carbonate reservoir from the eastern Sichuan Basin (South China). Our results indicated that the trapping pressure would be obviously overestimated if the presence of heavy hydrocarbons was not taken into account.

ACOX1-mediated peroxisomal fatty acid oxidation contributes to metabolic reprogramming and survival in chronic lymphocytic leukemia.

Chronic lymphocytic leukemia (CLL) is still an incurable disease, with many patients developing resistance to conventional and targeted therapies. To better understand the physiology of CLL and facilitate the development of innovative treatment options, we examined specific metabolic features in the tumor CLL B-lymphocytes. We observed metabolic reprogramming, characterized by a high level of mitochondrial oxidative phosphorylation activity, a low glycolytic rate, and the presence of C2- to C6-carnitine end-products revealing an unexpected, essential role for peroxisomal fatty acid beta-oxidation (pFAO). Accordingly, downmodulation of ACOX1 (a rate-limiting pFAO enzyme overexpressed in CLL cells) was enough to shift the CLL cells' metabolism from lipids to a carbon- and amino-acid-based phenotype. Complete blockade of ACOX1 resulted in lipid droplet accumulation and caspase-dependent death in CLL cells, including those from individuals with poor cytogenetic and clinical prognostic factors. In a therapeutic translational approach, ACOX1 inhibition spared non-tumor blood cells from CLL patients but led to the death of circulating, BCR-stimulated CLL B-lymphocytes and CLL B-cells receiving pro-survival stromal signals. Furthermore, a combination of ACOX1 and BTK inhibitors had a synergistic killing effect. Overall, our results highlight a less-studied but essential metabolic pathway in CLL and pave the way towards the development of new, metabolism-based treatment options.

Palladium(II) and platinum(II) based S^N^S and Se^N^Se pincer complexes as catalysts for CO2 hydrogenation and N-formylation of diethylamine to diethylformamide

In this study, we report newly synthesized S^N^S and Se^N^Se tridentate platinum(II) and palladium(II) pincer complexes. These complexes have been evaluated as pre-catalysts in the hydrogenation of carbon dioxide to formate under basic conditions. These new molecular catalysts proved to be active in forming industrially valuable chemical intermediates like formate and diethylformamide from CO2. The complexes are soluble in THF and insoluble in water enabling easy catalyst recovery from a biphasic mixture of THF/water solvent system after catalysis. The pincer ligands provide a robust framework for stabilizing the active centers through various catalytic cycle steps. Palladium(II) catalysts yielded formate with TONs as high as 1881, while Se^N^Se platinum(II)-based catalysts (C1, C2, and C3) catalyzed the hydrogenation of CO2 to formate at TONs of 550, 421, and 1254, respectively, after 24 h. Similarly, the N-formylation of diethylamine using CO2 and H2 in the presence of C2 is effective with yields up to 71 %.

Three cytosolic NAD-malate dehydrogenase isoforms of Arabidopsis thaliana: on the crossroad between energy fluxes and redox signaling.

In yeast and animal cells, mitochondrial disturbances resulting from imbalances in the respiratory chain require malate dehydrogenase (MDH) activities for re-directing fluxes of reducing equivalents. In plants, in addition to mitochondria, plastids use malate valves to counterbalance and maintain redox-homeostasis. Arabidopsis expresses three cytosolic MDH isoforms, namely cyMDH1, cyMDH2, and cyMDH3, the latter possessing an N-terminal extension carrying a unique cysteine residue C2. In this study, redox-effects on activity and structure of all three cyMDH isoforms were analyzed in vitro. cyMDH1 and cyMDH2 were reversibly inactivated by diamide treatment, accompanied by dimerization via disulfide-bridge formation. In contrast, cyMDH3 forms dimers and higher oligomers upon oxidation, but its low specific activity is redox-independent. In the presence of glutathione, cyMDH1 and cyMDH2 are protected from dimerization and inactivation. In contrast, cyMDH3 still dimerizes but does not form oligomers any longer. From analyses of single and double cysteine mutants and structural modeling of cyMDH3, we conclude that the presence of C2 and C336 allows for multiple cross-links in the higher molecular mass complexes comprising disulfides within the dimer as well as between monomers of two different dimers. Furthermore, nuclear localization of cyMDH isoforms was significantly increased under oxidizing conditions in isolated Arabidopsis protoplasts, in particular of isoform cyMDH3. The unique cyMDH3 C2–C2-linked dimer is, therefore, a good candidate as a redox-sensor taking over moonlighting functions upon disturbances of energy metabolism, as shown previously for the glycolytic enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH) where oxidative modification of the sensitive catalytic cysteine residues induces nuclear translocation.

Studying Phase Behavior of Oil/Natural-Gas Systems for Designing Gas-Injection Operations: A Montney Case Study

SummaryAdvances in horizontal drilling and multistage hydraulic fracturing have unlocked tight-oil resources, such as the Montney Formation in the Western Canadian Sedimentary Basin. However, the average oil-recovery factor after primary production is 5 to 10% of the original oil in place. The aims of this study are to investigate phase behavior and to estimate the minimum miscibility pressure (MMP) of the Montney oil/natural-gas systems.First, we measure the MMPs of the oil/gas systems using the vanishing interfacial tension (VIT) technique. The gas samples are methane (C1) and mixtures of methane and ethane (C1/C2). Second, we perform constant-composition-expansion (CCE) tests to study the phase behavior of the oil/gas systems using a pressure/volume/temperature (PVT) cell. To complement the VIT and CCE tests, we perform bulk-phase tests to visualize vaporizing/condensing phenomena at the oil/gas interface using a visualization cell. Finally, we use the measured CCE and MMP data to calibrate the Peng-Robinson (Robinson and Peng 1978) equation of state (PR-EOS) and predict the MMP of the oil/gas systems using ternary diagrams. The results suggest that the dominant mechanism for developing miscibility conditions for oil/C1 and oil/C1/C2 systems is vaporizing and condensing gas drive, respectively. According to the results of the VIT and CCE tests, increasing C2 mole fraction in the gas mixtures significantly reduces MMP of the oil/gas system (from 4,366 psi for oil/C1 to 1,467 psi for oil/C1/C2 with 71.3 mol% C2) and increases the oil-swelling factor (from 1.47 to 1.61 by increasing C2 mol% from 0 to 70 mol%). The results of visualization tests show that the presence of C2 in the injection gas significantly enhances oil swelling compared with the pure-C1 case. We observe vaporizing flows of oil components in all tests and strong condensing flows of C1 and C2 into the oil phase in the C1/C2 test with increasing gas-injection pressure. The MMP values predicted by plotting two-phase equilibrium data on ternary diagrams appear to be in good agreement with the measured ones. The results can be used to optimize the injection-gas composition and operating pressure in the Montney.

Impurity composition of monoisotopic 28SiF4 silicon tetrafluoride

The impurity composition of 28SiF4 has been studied for the first time by gas chromatography/mass spectrometry using gas-adsorption capillary columns. For identification and determination of impurity substances by gas chromatography/mass spectrometry, we have proposed using cryogenic preconcentration of the impurities from 28SiF4. The presence of C2–C4 hydrocarbon impurities and sulfur hexafluoride has been confirmed. We have identified 35 impurity substances in 28SiF4, including linear and branched C5–C8 saturated hydrocarbons, aromatic hydrocarbons, chlorine- and fluorine-containing hydrocarbons, and silicon- and sulfur-containing substances, of which 28 have been detected for the first time.

The refluxing anterior accessory saphenous vein demonstrates similar clinical severity when compared to the refluxing great saphenous vein

To prospectively compare disease severity in subjects with anterior accessory saphenous vein versus great saphenous vein incompetence with an incompetent saphenofemoral junction. Data were^ collected from 241 subjects and 290 limbs over a six-month period. These subjects were categorized into three groups with primary venous reflux disease, namely anterior accessory saphenous vein, great saphenous vein, and control. Statistical methods including descriptive statistics, student t-tests, and log linear modeling were employed to compare groups and determine predictive features out of the 41 demographic and disease-specific variables collected. Subjects in the anterior accessory saphenous vein group and those in the great saphenous vein group demonstrate statistically significant differences as compared to the control group with respect to the following disease-specific features: mean VCSS, presence of C2 and C3 disease. The anterior accessory saphenous vein group also showed statistically significant differences in gender compared to both great saphenous vein and control, as well as mean body mass index compared to the control. Log-linear modeling revealed equivalent disease severity when comparing patients with saphenofemoral junction reflux to the great saphenous vein or anterior accessory saphenous vein. Patterns of reflux from the saphenofemoral junction to either the anterior accessory saphenous vein or great saphenous vein possess similar disease severity and commonly suffer complications of venous stasis.

Third harmonic generation in air ambient and laser ablated carbon plasma

We report the third harmonic generation of a nanosecond laser pulse (1.06 μm) in air ambient and in the presence of nanoparticles from laser ablated carbon plasma. Significant decrease in the threshold of third harmonic generation and multi-fold increment in the intensity of generated third harmonic is observed in presence of carbon plasma. The third harmonic in air is due to the quasi-resonant four photon process involving vibrationally excited states of molecular ion of nitrogen due to electron impact ionization and laser pulse. Following optical emission spectroscopic observations we conclude that the presence of C2 and CN in the ablated plume play a vital role in the observed third harmonic signals.

Killer immunoglobulin receptor genes and their HLA-C ligand are associated with Type 1 diabetes in an Eastern Indian population.

Killer immunoglobulin-like receptors (KIRs) and their interaction with HLA class I ligands have been shown to be associated with Type 1 diabetes mellitus. The aim of our study was to investigate the influence of KIR genes and their HLA-C ligands for susceptibility to Type 1 diabetes in patients from Eastern India. A total of 135 patients with Type 1 diabetes and 98 healthy subjects from Eastern India were typed for KIR genes and HLA-C ligands using PCR-based genotyping. The frequencies of these genes were compared between patients and controls. Comparison of KIR genes between Type 1 diabetes patients and healthy subjects revealed significantly different frequencies of KIRs 2DL2 and 2DS4. The presence of HLA-C1 was negatively associated with disease. The presence of both HLA-C1 and -C2 showed a negative association with Type 1 diabetes, whereas the absence of C1 and presence of C2 was positively associated with disease. Stratification analysis of HLA-C ligands and KIRs showed significant associations between Type 1 diabetes and 2DL2+/C1-, 2DL2-/C1+, 2DL3+/C1+, 2DL3+/C1- and 2DS2+/C1-. Our results suggest that the interaction of KIRs with HLA-C ligands are significant and certain combinations contribute to susceptibility to and protection against Type 1 diabetes.

Monitoring light hydrocarbons in Brazilian coal mines and in confined coal samples

Abstract Monitoring light hydrocarbons (LHCs) in coal mines, particularly methane, is important not only because of their implications for global climate change but also for economic and safety reasons. Furthermore, the identification and quantification of LHCs in coal mine air samples and desorbed from confined coal may contribute to a better understanding of coal seam characteristics. The paucity of information about the levels of methane in Brazilian underground coal mines can be attributed to their difficult access and a lack of adequate procedures for correct gas sampling. The aim of this study is to optimize and apply standard gas chromatography procedures to determine LHC levels in the air of coal mines and in confined coal from five mines under operation, three underground (A, B, C) and two surface (D, E) mines, in southern Brazil. The results indicate methane (C1) levels varying from 3 ppm to 27% in the atmosphere of the underground mines. Mine A presented high levels of all LHCs analyzed (C1 to C5), while only C1 and C2 were detected in mine B, and hydrocarbons ranging from C1 to C4 were found in mine C. On the other hand, surface mines presented narrow concentration range for C1 (3 ppm to 470 ppm) and C2–C3, with higher levels observed for puncture explosive points. Among LHCs, methane is desorbed in higher concentrations from confined coals and the presence of C2 was detected in all samples while C3–C5 were only observed in coals from underground mines. These data are consistent with those obtained from the air gas samples collected in the mines under study. Geological events such as faulting and intrusions can accelerate the release of gas or the trapping of large amounts of previously released methane. The LHC emissions from coal mines were found to be highly variable, indicating the need for a comprehensive survey of Brazilian coal mine emissions.

Does the KIR2DS5 Gene Protect from Some Human Diseases?

Background KIR2DS5 gene encodes an activating natural killer cell receptor whose ligand is not known. It was recently reported to affect the outcome of hematopoietic stem cell transplantation.Methodology/Principal FindingsIn our studies on KIR2DS5 gene associations with human diseases, we compared the frequencies of this gene in patients and relevant controls. Typing for KIR2DS5 gene was performed by either individual or multiplex polymerase chain reactions which, when compared in the same samples, gave concordant results. We noted an apparently protective effect of KIR2DS5 gene presence in several clinical conditions, but not in others. Namely, this effect was observed in ankylosing spondylitis (p = 0.003, odds ratio [OR] = 0.47, confidence interval [CI] = 0.28–0.79), endometriosis (p = 0.03, OR = 0.25, CI = 0.07–0.82) and acute rejection of kidney graft (p = 0.0056, OR = 0.44, CI = 0.24–0.80), but not in non-small-cell lung carcinoma, rheumatoid arthritis, spontaneous abortion, or leukemia (all p>0.05). In addition, the simultaneous presence of KIR2DS5 gene and HLA-C C1 allotype exhibited an even stronger protective effect on ankylosing spondylitis (p = 0.0003, OR = 0.35, CI = 0.19–0.65), whereas a lack of KIR2DS5 and the presence of the HLA-C C2 allotype was associated with ankylosing spondylitis (p = 0.0017, OR = 1.92, CI = 1.28–2.89), whereas a lack of KIR2DS5 and presence of C1 allotype was associated with rheumatoid arthritis (p = 0.005, OR = 1.47, CI = 1.13–1.92). The presence of both KIR2DS5 and C1 seemed to protect from acute kidney graft rejection (p = 0.017, OR = 0.47, CI = 0.25–0.89), whereas lack of KIR2DS5 and presence of C2 seemed to favor rejection (p = 0.0015, OR = 2.13, CI = 1.34–3.37).Conclusions/SignificanceOur results suggest that KIR2DS5 may protect from endometriosis, ankylosing spondylitis, and acute rejection of kidney graft.

Effects of training history on resurgence in humans

This experiment assessed the effects of training history on resurgence in three college students. Four-choice arbitrary-matching-to-sample trials occurred in two components of a multiple schedule. An A1 or A2 sample stimulus and four (B) comparison stimuli occurred on AB trials, and a C1 or C2 sample stimulus and four (D) comparison stimuli occurred on CD trials. By the end of training, accuracy and latency measures were comparable across separate discriminations, selecting B2 in the presence of A2 and selecting D2 in the presence of C2, despite a lengthier training correlated with the former discrimination. Next, in the presence of A2 and C2, respectively, responses to B2 and D2 were extinguished and responses to B3 and D3 were reinforced. These responses to B3 and D3 then were extinguished in a final condition. In this final condition, resurgence to B2 occurred for each participant, whereas resurgence to D2 occurred for only one participant. Thus, there was greater resurgence of the discrimination with the lengthier training history, despite the discriminations being similar in terms of accuracy and latency before extinction. This result, therefore, can be classified as a latent, or remote, behavioral history effect.

Soluble triggering receptor expressed on myeloid cells-1 and diagnosis of ventilator-associated pneumonia

Dear Sir: The quest for a reliable diagnostic marker of ventilator-associated pneumonia (VAP) is still ongoing and whether determination of the alveolar concentration of the soluble form of the triggering receptor expressed on myeloid cells (TREM)-1 could be a valuable candidate is debated. Unfortunately, the study reported in this issue of Intensive Care Medicine will just generate further perplexity [1]. First, the presented work is the result of an ancillary study originating from the series reported last year in this same journal [2], which the authors should have clearly acknowledged. This fact raises concerns regarding the quality of the samples’ conservation (since 2001) especially if they have been subject to freeze/thaw cycles that rapidly degrade sTREM-1. Because alveolar sampling was initially not dedicated to sTREM-1 measurement, bronchoalveolar lavage (BAL) fluid was centrifuged at 250g for 10 min, a procedure largely insufficient to eliminate cell particulates that express membranebound TREM-1 (alveolar macrophages or neutrophils): this may have led to artificially increased sTREM-1 concentrations. Second, the effects of previous antibiotherapy of the diagnosis of VAP are not discussed. VAP was diagnosed by the presence of C2% cells containing intracellular organisms (ICO) or quantitative culture of C10 cfu/ml. Although previous antibiotics do not seem to interfere with ICO percentage [2], this is obviously not the case for quantitative cultures. Unfortunately, no data are presented on the number of VAP diagnosed by ICO percentage or quantitative culture: a subset of patients may have been classified as no VAP just because \2% ICO and \10 cfu/ml were observed while antibiotics were given. By the way, we have no idea on the final diagnosis that was retained in the no-VAP patients. Despite the fact that all these limitations by themselves preclude the drawing of any conclusion, another problematic issue must be pointed out. The authors used a commercially available assay, namely the human TREM-1 Quantikine assay from RnD Systems (Minneapolis, USA), to measure sTREM-1 concentrations. It happens that this assay was recalled by RnD systems during the early summer of 2008 because of its inability to properly measure soluble TREM-1 concentration. I want to believe that the authors were not aware of that. Of note, the three studies [3–5] reporting good performances of BAL sTREM-1 measurement in diagnosing VAP used an ELISA technique (Duoset, RnD Systems) different from the one employed in the two studies [1, 6] showing limited sTREM-1 usefulness (Quantikine). It may well be that sTREM-1 measurement will finally prove to be disappointing in diagnosing VAP, but the current study is just not interpretable.

TRANSFORMATION OF AVOIDANCE RESPONSE FUNCTIONS IN ACCORDANCE WITH SAME AND OPPOSITE RELATIONAL FRAMES

Research on the emergence of human avoidance behavior in the absence of direct contact with an aversive event is somewhat limited. Consistent with work on derived relational responding, the present study sought to investigate the transformation of avoidance response functions in accordance with the relational frames of Same and Opposite. Participants were first exposed to nonarbitrary and arbitrary relational training and testing in order to establish Same and Opposite relations among arbitrary stimuli. The training tasks were; Same-A1-B1, Same-A1-C1, Opposite-A1-B2, Opposite-A1-C2. Next, all possible combinatorially entailed (i.e., B-C and C-B) relations were tested. During the avoidance-conditioning phase, one stimulus (B1) from the relational network signaled a simple avoidance response that cancelled a scheduled presentation of an aversive image and sound. All but one of the participants who met the criteria for conditioned avoidance also demonstrated derived avoidance by emitting the avoidance response in the presence of C1 and the nonavoidance response in the presence of C2. Control participants who were not exposed to relational training and testing did not show derived avoidance. Implications of the findings for understanding clinically significant avoidance behavior are discussed.

Protein Phosphatase 2A Enhances the Proapoptotic Function of Bax through Dephosphorylation

Bax is a major proapoptotic member of the Bcl2 family that is required for apoptotic cell death. We have recently discovered that Bax phosphorylation at serine 184 induced by nicotine through activation of protein kinase AKT abolishes its proapoptotic function in human lung cancer cells. Here we found that either treatment of cells with the protein phosphatase 2A (PP2A) inhibitor okadaic acid or specific disruption of PP2A activity by expression of SV40 small tumor antigen enhanced Bax phosphorylation, whereas C(2)-ceramide, a potent PP2A activator, reduced nicotine-induced Bax phosphorylation, suggesting that PP2A may function as a physiological Bax phosphatase. PP2A co-localized and interacted with Bax. Purified, active PP2A directly dephosphorylated Bax in vitro. Overexpression of the PP2A catalytic subunit (PP2A/C) suppressed nicotine-stimulated Bax phosphorylation in association with increased apoptotic cell death. By contrast, depletion of PP2A/C by RNA interference enhanced Bax phosphorylation and prolonged cell survival. Mechanistically C(2)-ceramide-induced Bax dephosphorylation caused a conformational change by exposure of the 6A7 epitope (amino acids 13-19) that is normally hidden at its N terminus that promoted the insertion of Bax into mitochondrial membranes and formation of Bax oligomers leading to cytochrome c release and apoptosis. In addition, PP2A directly disrupted the Bcl2/Bax association to liberate Bax from the heterodimer complex. Thus, PP2A may function as a physiological Bax regulatory phosphatase that not only dephosphorylates Bax but also activates its proapoptotic function.

Polymerizations of vinyl-cyclohexane in the presence of C2, C2 v, and Cs zirconocene-based catalysts

Polymerizations of vinyl-cyclohexane (VCH) in the presence of catalytic systems based on zirconocenes belonging to C 2, C 2 v or C s symmetry group were performed. All polymers were analyzed by 13C NMR spectroscopy and show isotactic microstructure. A steric control mechanism, involving a like 1,3-asymmetric induction of the chiral carbon of the last inserted unit on the chirality of the incoming monomer coordination, is proposed. This would be the only stereocontrol mechanism in the presence of a C 2 v -symmetry catalyst, and it would enforce or overcome site control in case of active species with C 2 and C s -symmetry, respectively.

Evolution of Laser Plume upon Graphite Ablation in Vacuum and Nitrogen

The propagation of carbon laser plasma during its expansion in vacuum and in a nitrogen atmosphere was studied with the use of an Nd : YAG laser (λ = 532 nm, τ = 15 ns). The presence of C2, C3, and CN molecules was detected in emission spectra, and the space and time characteristics of their propagation were determined. The vibrational temperatures of C2 and CN molecules were calculated.

The complement inhibitor, CRIT, undergoes clathrin-dependent endocytosis

Complement C2 receptor inhibitor trispanning (CRIT) is a receptor for the second component of complement and is found in various tissues and hemopoietic cells. On binding to CRIT, C2 cannot be activated to potentially form a variant-C3 convertase as it is rendered non-cleavable by C1s. CRIT thus limits the amount of C3 convertase formed on the cell surface. In this study we have shown, using flow cytometry and immunofluorescence microscopy, that human CRIT undergoes endocytosis from the plasma membrane. The endocytosis, possibly ligand mediated, occurs via clathrin-coated pits as it can be inhibited by prior incubation of cells in hypertonic medium or with chlorpromazine, at 37 degrees C. However, inhibition of endocytosis was not possible after treatment with nystatin, or filipin, inhibitors of caveolae/raft-dependent endocytosis. In the presence of C2 alone, CRIT associates with the adapter protein, beta-arrestin-2, and whether in association with C2 or not, then appears in the perinuclear region, but does not appear to be translocated into the nucleus. Apart from the C3aR and C5aR that internalize the anaphylatoxic peptides, this is the first report of the internalization via the clathrin pathway of a receptor for a complement serum protein.

Growth and structure of fullerene-like CNx thin films produced by pulsed laser ablation of graphite in nitrogen

The growth and structure of fullerene-like CNx films produced by laser ablation of graphite in low pressure nitrogen were investigated. Deposition conditions were selected based on investigations of CN and C2 concentration at the condensation surface, vibrational temperature of CN radicals, and kinetic energies of atomic and molecular species. Films were characterized with x-ray photoelectron spectroscopy, Raman spectroscopy, high-resolution transmission electron microscopy, nanoindentation, and stress analyses. The nitrogen content in CNx films directly depended on the concentration of CN radicals at the condensation surface. Formation of fullerene-like structures required a high vibrational temperature of these radicals, which was maximized at about 4 eV for depositions at 10 mTorr N2 and laser fluences of ∼7 J/cm2. The presence of C2 had only a minor effect on film composition and structure. Optimization of plasma characteristics and a substrate temperature of 300 °C helped to produce about 1-μm-thick solid films of CNx (N/C ratio≈0.2–0.3) and pure carbon consisting of fullerene-like fragments and packages. In contrast to carbon films, fullerene-like CNx films exhibited a high elastic recovery of about 80% in using a Berkovich tip at 5 mN load and indentation depths up to 150 nm. Their elastic modulus was about 160 GPa measured from the unloading portion of an indentation curve, and about 250 GPa measured with a 40 Hz tip oscillation during nanoindentation tests. The difference was related to time dependent processes of shape restoration of fullerene-like fragments, and an analogy was made to the behavior of elastomer polymers. However, unlike elastomers, CNx film hardness was as high as 30 GPa, which was twice that of fullerene-like carbon films. The unusual combination of high elasticity and hardness of CNx films was explained by crosslinking of fullerene fragments induced by the incorporated nitrogen and stored compressive stress. The study demonstrated laser ablation as a viable technique for the growth of fullerene-like CNx films, which may be used as hard protective coatings resisting brittle fracture at high loads and extensive substrate deformations.