Investigation on very high frequency (VHF) plasma and its glow discharge mechanism during the deposition of microcrystalline silicon (μc-Si:H) film have been investigated. In situ optical emission ...spectroscopy (OES) measurements were used to study the influence of deposition conditions on VHF plasma. The study reveals that: the OES intensities of Si*, SiH*, H
α* and H
β* increase significantly with plasma excitation frequency; all the OES intensities increase initially with plasma power and tend to be saturated at working pressure 120 Pa, a maximum can be observed while at 60 Pa; the variation of the intensities with working gas pressure strongly depends on plasma power, and maximum intensity for every peak was observed between 100 and 120 Pa. Based on the analysis of the OES spectra, the glow discharge mechanism and the relationship between the OES spectra and the deposition rates are also discussed.
The uptake of Cd, Se(IV) and Zn by the freshwater alga
Scenedesmus obliquus and the subsequent transfer and release budget in
Daphnia magna were investigated under different nutrient additions and ...cell incubation conditions. An increase in ambient phosphate concentrations from 0.5 μmol l
−1 to 50 μmol l
−1 significantly increased the intracellular accumulation of Cd (by 18×) and Zn (by 5×), but decreased the accumulation of Se (by 126×) in the alga. The percentage of these metals distributing in the intracellular pool of algae also increased substantially with increasing ambient P concentrations. Nitrate addition from 5.0 to 200 μmol l
−1 did not influence the uptake of any of the three metals, although a significant decrease in the intracellular Se distribution was observed. Radiolabeled algae under different nutrient manipulations (semi-continuous culture, starvation, and P-pulse treatments) were used to measure trophic transfer assimilation efficiency (AE) in
Daphnia. When the algal cells were grown in a semi-continuous culture, starved for N and P, or were treated with P-pulse, the AEs of Cd and Zn were generally independent of the nutritional conditions, but the Se AE was significantly affected by different P levels. The efflux rate constants, determined during 10 d depuration following 7 days of dietary uptake, decreased significantly for Cd and Zn, but were relatively constant for Se with increasing P concentration. N-addition caused no effect on the metal efflux rate constants. P- or N-additions did not influence the release budget (including molting, neonates, excretion and feces) for all three elements in
Daphnia. Our study indicated that phosphate enrichment may substantially increase metal uptake in green alga
S. obliquus. Responses of trophic transfer in
Daphnia to nutrient enrichment were metal specific. P-enrichment can possibly lead to considerable decrease on Se transfer from algae to zooplankton.
Phosphorous enrichment influences metal uptake by algae, but not transfer to a zooplankton grazer.
A new metalloproteinase–disintegrin, named Jerdonitin, was purified from
Trimeresurus jerdonii venom with a molecular weight of 36
kDa on SDS–PAGE. It dose-dependently inhibited ADP-induced human ...platelet aggregation with IC
50 of 120
nM. cDNA cloning and sequencing revealed that Jerdonitin belonged to the class II of snake venom metalloproteinases (SVMPs) (P-II class). Different from other P-II class SVMPs, metalloproteinase and disintegrin domains of its natural protein were not separated, confirmed by internal peptide sequencing. Compared to other P-II class SVMPs, Jerdonitin has two additional cysteines (Cys219 and Cys238) located in the spacer domain and disintegrin domain, respectively. They probably form a disulfide bond and therefore the metalloproteinase and disintegrin domains cannot be separated by posttranslationally processing. In summary, comparison of the amino acid sequences of Jerdonitin with those of other P-II class SVMPs by sequence alignment and phylogenetic analysis, in conjunction with natural protein structure data, suggested that it was a new type of P-II class SVMPs.
The tumor suppressor activity of the BRCA1 gene product is due, in part, to functional interactions with other tumor suppressors, including p53 and the retinoblastoma (RB) protein. RB binding sites ...on BRCA1 were identified in the C-terminal BRCT domain (Yarden and Brody, 1999) and in the N-terminus (aa 304-394) (Aprelikova et al., 1999). The N-terminal site contains a consensus RB binding motif, LXCXE (aa 358-362), but the role of this motif in RB binding and BRCA1 functional activity is unclear. In both in vitro and in vivo assays, we found that the BRCA1:RB interaction does not require the BRCA1 LXCXE motif, nor does it require an intact A/B binding pocket of RB. In addition, nuclear co-localization of the endogenous BRCA1 and RB proteins was observed. Over-expression of wild-type BRCA1 (wtBRCA1) did not cause cell cycle arrest but did cause down-regulation of expression of RB, p107, p130, and other proteins (e.g., p300), associated with increased sensitivity to DNA-damaging agents. In contrast, expression of a full-length BRCA1 with an LXCXE inactivating mutation (LXCXE-->RXRXH) failed to down-regulate RB, blocked the down-regulation of RB by wtBRCA1, induced chemoresistance, and abrogated the ability of BRCA1 to mediate tumor growth suppression of DU-145 prostate cancer cells. wtBRCA1-induced chemosensitivity was partially reversed by expression of either Rb or p300 and fully reversed by co-expression of Rb plus p300. Our findings suggest that: (1) disruption of the LXCXE motif within the N-terminal RB binding region alters the biologic function of BRCA1; and (2) over-expression of BRCA1 inhibits the expression of RB and RB family (p107 and p130) proteins.
A novel C-type lectin-like protein, dabocetin, was purified from
Daboia russellii siamensis venom. On SDS-polyacrylamide gel electrophoresis, it showed a single band with an apparent molecular weight ...of 28
kDa and two distinct bands with the apparent molecular weights of 15.0
kDa and 14.5
kDa under non-reducing and reducing conditions, respectively. cDNA clones containing the coding sequences for dabocetin α and β subunits were isolated and sequenced. The deduced protein sequences of both subunits were confirmed by N-terminal amino acid sequencing and trypsin-digested peptide mass fingerprinting. Dabocetin did not induce platelet aggregation in platelet-rich plasma. It also had little effect on the platelet aggregation induced by ADP, TMVA or stejnulxin. Whereas, dabocetin inhibited ristocetin-induced platelet agglutination in platelet-rich plasma in a dose-dependent manner with an IC
50 value of 0.35
μM. Flow cytometry analysis showed that dabocetin significantly inhibited mAb SZ2 binding to platelet membrane glycoprotein Ib alpha, indicating that platelet membrane glycoprotein Ib is involved in the inhibitory effect of dabocetin on ristocetin-induced platelet agglutination.
Stem cells play a critical role in bone regeneration. Multiple populations of skeletal stem cells have been identified in long bone, while their identity and functions in alveolar bone remain ...unclear. Here, we identified a quiescent leptin receptor–expressing (LepR+) cell population that contributed to intramembranous bone formation. Interestingly, these LepR+ cells became activated in response to tooth extraction and generated the majority of the newly formed bone in extraction sockets. In addition, genetic ablation of LepR+ cells attenuated extraction socket healing. The parabiosis experiments revealed that the LepR+ cells in the healing sockets were derived from resident tissue rather than peripheral blood circulation. Further studies on the mechanism suggested that these LepR+ cells were responsive to parathyroid hormone/parathyroid hormone 1 receptor (PTH/PTH1R) signaling. Collectively, we demonstrate that LepR+ cells, a postnatal skeletal stem cell population, are essential for alveolar bone regeneration of extraction sockets.
Abstract
Two-dimensional (2D) materials offer a prospect of membranes that combine negligible gas permeability with high proton conductivity and could outperform the existing proton exchange ...membranes used in various applications including fuel cells. Graphene oxide (GO), a well-known 2D material, facilitates rapid proton transport along its basal plane but proton conductivity across it remains unknown. It is also often presumed that individual GO monolayers contain a large density of nanoscale pinholes that lead to considerable gas leakage across the GO basal plane. Here we show that relatively large, micrometer-scale areas of monolayer GO are impermeable to gases, including helium, while exhibiting proton conductivity through the basal plane which is nearly two orders of magnitude higher than that of graphene. These findings provide insights into the key properties of GO and demonstrate that chemical functionalization of 2D crystals can be utilized to enhance their proton transparency without compromising gas impermeability.
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