共查询到20条相似文献,搜索用时 31 毫秒
1.
V. A. Belyaev D. A. Kozlov A. A. Terent’ev A. E. Trenin 《Plasma Physics Reports》2017,43(10):1039-1041
A method for determining the lifetime of unstable ions is described. The method is based on measuring the decrease in the ion beam current onto a fixed detector with increasing path length of the ion beam from the ion source to the detector. The measurements performed for D? 2 and HD? molecular ions have shown that their lifetimes are 3.5 ± 0.1 and 4.4 ± 0.1 μs, respectively. 相似文献
2.
Since its introduction approximately seven years ago, selamectin (Stronghold®/Revolution®, Pfizer Inc.) has been used off-label to treat a number of ecto- and endoparasite conditions in dogs and cats. It has been used as a successful prophylactic against Dirofilaria repens and as a treatment for Aelurostrongylus abstrusus in cats. It has also been used to treat notoedric mange, infestation with the nasal mite Pneumonyssoides caninum, Cheyletiella spp. and Neotrombicula autumnalis infestations and larval Cordylobia anthropophaga infection. However, to date attempts to treat generalised canine demodicosis have not been successful. In all cases, treatment was apparently well tolerated by the host. 相似文献
3.
We present two NMR experiments, (3,2)D HNHA and (3,2)D HNHB, for rapid and accurate measurement of 3J(H N-H alpha) and 3J(N-H beta) coupling constants in polypeptides based on the principle of G-matrix Fourier transform NMR spectroscopy and quantitative J-correlation. These experiments, which facilitate fast acquisition of three-dimensional data with high spectral/digital resolution and chemical shift dispersion, will provide renewed opportunities to utilize them for sequence specific resonance assignments, estimation/characterization of secondary structure with/without prior knowledge of resonance assignments, stereospecific assignment of prochiral groups and 3D structure determination, refinement and validation. Taken together, these experiments have a wide range of applications from structural genomics projects to studying structure and folding in polypeptides. 相似文献
4.
A confined aquifer in the Malm Karst of the Franconian Alb, South Germany was investigated in order to understand the role of the vadose zone in denitrifiaction processes. The concentrations of chemical tracers Sr2+ and Cl– and concentrations of stable isotope 18O were measured in spring water and precipitation during storm events. Based on these measurements a conceptual model for runoff was constructed. The results indicate that pre-event water, already stored in the system at the beginning of the event, flows downslope on vertical and lateral preferential flow paths. Chemical tracers used in a mixing model for hydrograph separation have shown that the pre-event water contribution is up to 30%. Applying this information to a conceptual runoff generation model, the values of 15N and 18O in nitrate could be calculated. Field observations showed the occurence of significant microbial denitrification processes above the soil/bedrock interface before nitrate percolates through to the deeper horizon of the vadose zone. The source of nitrate could be determined and denitrification processes were calculated. Assuming that the nitrate reduction follows a Rayleigh process one could approximate a nitrate input concentration of about 170 mg/l and a residual nitrate concentration of only about 15%. The results of the chemical and isotopic tracers postulate fertilizers as nitrate source with some influence of atmospheric nitrate. The combined application of hydrograph separation and determination of isotope values in 15N and 18O of nitrate lead to an improved understanding of microbial processes (nitrification, denitrification) in dynamic systems. 相似文献
5.
E. Yu. Aleshina N. V. Pyndyk A. A. Moisa M. A. Sanzhakov O. N. Kharybin E. N. Nikolaev E. F. Kolesanova 《Biochemistry (Moscow) Supplemental Series B: Biomedical Chemistry》2008,2(3):288-292
The peptide RHDSGY, a fragment of the human β-amyloid Zn-binding site, and its isomers RH(D-Asp)SGY and RH(β-Asp)SGY have been obtained as amides by means of solid-phase synthesis and analyzed by HPLC and various mass spectrometric methods. The problem of low yield of the RHDSGY peptide and its isomers attributed to 9-fluorenylmethoxycarbonyl (Fmoc)-amino acids and/or formation of such side-products as RH(β-Asp)SGY (or RHDSGY during synthesis of RH(β-Asp)SGY) and RH(Asp-imide) SGY was solved via selection of individual reagents for removal of Fmoc groups from α-amino groups of the growing peptide chain. 相似文献
6.
7.
Umitsu M Morishita H Murata Y Udaka K Akutsu H Yagi T Ikegami T 《Journal of biomolecular NMR》2005,31(4):365-366
8.
The limits of resolution that can be obtained in 1H–15N 2D NMR spectroscopy of isotopically enriched nanocrystalline proteins are explored. Combinations of frequency switched Lee–Goldburg (FSLG) decoupling, fast magic angle sample spinning (MAS), and isotopic dilution via deuteration are investigated as methods for narrowing the amide 1H resonances. Heteronuclear decoupling of 15N from the 1H resonances is also studied. Using human ubiquitin as a model system, the best resolution is most easily obtained with uniformly 2H and 15N enriched protein where the amides have been exchanged in normal water, MAS at 20 kHz, and WALTZ-16 decoupling of the 15N nuclei. The combination of these techniques results in average 1H lines of only 0.26 ppm full width at half maximum. Techniques for optimizing instrument stability and 15N decoupling are described for achieving the best possible performance in these experiments. 相似文献
9.
In two mountain ecosystems at the Alptal research site in central Switzerland, pulses of 15NO3 and 15NH4 were separately applied to trace deposited inorganic N. One forested and one litter meadow catchment, each approximately
1600 m2, were delimited by trenches in the Gleysols. K15NO3 was applied weekly or fortnightly over one year with a backpack sprayer, thus labelling the atmospheric nitrate deposition.
After the sampling and a one-year break, 15NH4Cl was applied as a second one-year pulse, followed by a second sampling campaign. Trees (needles, branches and bole wood),
ground vegetation, litter layer and soil (LF, A and B horizon) were sampled at the end of each labelling period. Extractable
inorganic N, microbial N, and immobilised soil N were analysed in the LF and A horizons. During the whole labelling period,
the runoff water was sampled as well. Most of the added tracer remained in both ecosystems. More NO3− than NH4+ tracer was retained, especially in the forest. The highest recovery was in the soil, mainly in the organic horizon, and in
the ground vegetation, especially in the mosses. Event-based runoff analyses showed an immediate response of 15NO3− in runoff, with sharp 15N peaks corresponding to discharge peaks. NO3− leaching showed a clear seasonal pattern, being highest in spring during snowmelt. The high capacity of N retention in these
ecosystems leads to the assumption that deposited N accumulates in the soil organic matter, causing a progressive decline
of its C:N ratio. 相似文献
10.
Cui Y Karunasekara Y Harvey PJ Board PG Dulhunty AF Casarotto MG 《Journal of biomolecular NMR》2005,32(1):89-90
11.
Tonelli M Masterson LR Hallenga K Veglia G Markley JL 《Journal of biomolecular NMR》2007,39(3):177-185
We present a highly sensitive pulse sequence, carbonyl carbon label selective 1H–15N HSQC (CCLS-HSQC) for the detection of signals from 1H–15N units involved in 13C′–15N linkages. The CCLS-HSQC pulse sequence utilizes a modified 15N CT evolution period equal to 1/(
) (∼33 ms) to select for 13C′–15N pairs. By collecting CCLS-HSQC and HNCO data for two proteins (8 kDa ubiquitin and 20 kDa HscB) at various temperatures
(5–40°C) in order to vary correlation times, we demonstrate the superiority of the CCLS-HSQC pulse sequence for proteins with
long correlation times (i.e. higher molecular weight). We then show that the CCLS-HSQC experiment yields assignments in the
case of a 41 kDa protein incorporating pairs of 15N- and 13C′-labeled amino acids, where a TROSY 2D-HN(CO) had failed. Although the approach requires that the 1H–15N HSQC cross peaks be observable, it does not require deuteration of the protein. The method is suitable for larger proteins
and is less affected by conformational exchange than HNCO experiments, which require a longer period of transverse 15N magnetization. The method also is tolerant to the partial loss of signal from isotopic dilution (scrambling). This approach
will be applicable to families of proteins that have been resistant to NMR structural and dynamic analysis, such as large
enzymes, and partially folded or unfolded proteins. 相似文献
12.
A model of the HK2a subunit of the rabbit colonic H+, K+
ATPase has been generated using the crystal structure of the Ca+2 ATPase as a template. A pairwise sequence alignment of the deduced primary sequences of the two proteins demonstrated that they share 29% amino acid sequence identity and 47% similarity. Using O (version 7) the model of HK2a was constructed by interactively mutating, deleting, and inserting the amino acids that differed between the pairwise sequence alignment of the Ca+2 ATPase and HK2a. Insertions and deletions in the HK2a sequence occur in apparent extra-membraneous loop regions. The HK2a model was energy minimized and globally refined to a level comparable to that of the Ca+2 ATPase structure using CNS. The charge distribution over the surface of HK2a was evaluated in GRASP and possible secondary structure elements of HK2a were visualized in BOBSCRIPT. Conservation and placement of residues that may be involved in ouabain binding by the H+, K+
ATPase were considered and a putative location for the subunit was postulated within the structure.Figure Possible architecture of the HK2a subunit. The residue in green is the lysine (position 517, Fig. 1) that lies in the nucleotide binding pocket and the residue in red is the aspartic acid at the phosphorylation site (position 385). Based on an alignment with the Ca+2 ATPase, ten transmembrane helices were modeled into HK2a. The ten transmembrane helices are drawn as rods and shown in different colors for clarity. From left to right, the transmembrane helix designations are M10 (blue), M7 (gray), M8 (purple), M9 (orange), M5 (pink), M6 (green), M3 (brown), M4 (cyan), M2 (teal), and M1 (almond). 相似文献
13.
Tropical small mountainous rivers deliver a poorly quantified, but potentially significant, amount of carbon to the world’s
oceans. However, few historical records of land–ocean carbon transfer exist for any region on Earth. Corals have the potential
to provide such records, because they draw on dissolved inorganic carbon (DIC) for calcification. In temperate systems, the
stable- (δ13C) and radiocarbon (Δ14C) isotopes of coastal DIC are influenced by the δ13C and Δ14C of the DIC transported from adjacent rivers. A similar pattern should exist in tropical coastal DIC and hence coral skeletons.
Here, δ13C and Δ14C measurements were made in a 56-year-old Montastraea faveolata coral growing ~1 km from the mouth of the Rio Fajardo in eastern Puerto Rico. Additionally, the δ13C and Δ14C values of the DIC of the Rio Fajardo and its adjacent coastal waters were measured during two wet and dry seasons. Three
major findings were observed: (1) synchronous depletions of both δ13C and Δ14C in the coral skeleton are annually coherent with the timing of peak river discharge, (2) riverine DIC was always more depleted
in δ13C and Δ14C than seawater DIC, and (3) the correlation of δ13C and Δ14C was the same in both coral skeleton and the DIC of the river and coastal waters. These results indicate that coral skeletal
δ13C and Δ14C are recording the delivery of riverine DIC to the coastal ocean. Thus, coral records could be used to develop proxies of
historical land–ocean carbon flux for many tropical regions. Such information could be invaluable for understanding the role
of tropical land–ocean carbon flux in the context of land-use change and global climate change. 相似文献
14.
The molecular weight and subunit composition of Cl-,HCO3(-)- and picrotoxin-stimulated Mg2+-ATPase from rat brain plasma membrane solubilized in sodium deoxycholate were studied by gel filtration chromatography. The enzyme activity eluted from a Sephacryl S-300 column in a single peak associated with a protein of molecular weight approximately 300 kD and a Stokes radius of 5.4 nm. The enzyme-enriched fraction, concentrated and denatured by SDS, migrated through a Sephacryl S-200 column as three peaks with molecular weights of approximately 57, 53, and 45 kD. SDS-PAGE also showed three major protein bands with molecular weights of about 57, 53, and 48 kD. The molecular weight and subunit composition of the Cl- and HCO3(-)-stimulated Mg2+-ATPase from neuronal membrane of rat brain are similar with the molecular properties of GABA(A)-benzodiazepine receptor complex from mammalian brain but are different from those of P-type transport ATPases. 相似文献
15.
16.
Based on the difference in the CD14 and CD16 expression, two subsets of monocytes were identified in human and other mammalian
blood. These subsets have different patterns of adhesion molecules and chemokine receptors that suggests the different mode
of their interaction with endothelium and tissue traffic. Here, we investigated the ability of CD14+CD16+ and CD14++CD16− monocytes to adhere to endothelial cell monolayer in presence or absence of pro- and anti-inflammatory cytokines. We demonstrated
that CD14+CD16+ monocytes had a higher level of adhesion to intact monolayer of endothelial cells than CD14++CD16− monocytes. Adhesion of CD14++CD16− and CD14+CD16+ monocytes significantly increased in the presence of TNFα or its combination with other cytokines. IFNγ and IL-4 alone did
not affect the adhesion of monocytes. These results show that CD14++CD16− and CD14+CD16+ monocytes can be recruited to the inflamed endothelium, but CD14+CD16+ monocytes adhere to endothelial cells without inflammations twice as strongly as CD14++CD16− monocytes. 相似文献
17.
18.
The cystine/glutamate exchanger (antiporter xc−) is a membrane transporter involved in the uptake of cystine, the rate-limiting amino acid in the synthesis of glutathione.
Recent studies suggest that the antiporter plays a role in the slow oxidative excitotoxity and in the pathological effects
of β-N-oxalylamino-l-alanine, the molecule responsible for neurolathyrism, a neurotoxic upper motor neuron disease. The mouse cystine/glutamate
exchanger has been cloned and showed to be composed of two distinct proteins, one of which being a novel protein, named xCT,
of 502 amino acids and 12 putative trans-membrane domains. We have generated and purified a polyclonal antibody to mouse xCT
and studied its expression in rat brain and in different cultured cells (astrocytes, fibroblasts and neurons) using Western
blot and immunocytochemical techniques. Expression of xCT was also studied in rat brain and muscle at different developmental
stages. Parallel experiments were carried out with antibodies to the heavy chain of 4F2 surface antigen, the non-specific
subunit of the antiporter xc−. xCT antibody detected in all cell and tissue extracts a specific band of about 40 kDa. Subcellular fractionation demonstrated
that xCT is concentrated mainly in the microsomal-mitochondrial fraction, in accord with its structure as transmembrane protein.
Immunocytochemical analysis showed a strong staining in all cells examined, included neurons. Furthermore, both xCT and the
heavy chain of 4F2 surface antigen increased in the brain during development, reaching the highest expression in adulthood.
The study of the expression and developmental profile of xCT represents a first step towards a better characterization of
its biochemical properties and function, which in turn may help to understand the relative contribution of the xc− antiporter in the pathogenesis of certain neurodegenerative diseases. 相似文献
19.
Nishit Goradia Amelie Wißbrock Christoph Wiedemann Frank Bordusa Ramadurai Ramachandran Diana Imhof Oliver Ohlenschläger 《Biomolecular NMR assignments》2016,10(2):329-333
Interleukin-36α (IL-36α) is a recently characterised member of the interleukin-1 superfamily. It is involved in the pathogenesis of inflammatory arthritis in one third of psoriasis patients. By binding of IL-36α to its receptor IL-36R via the NF-κB pathway other cytokines involved in inflammatory and apoptotic cascade are activated. The efficacy of complex formation is controlled by N-terminal processing. To obtain a more detailed view on the structure function relationship we performed a heteronuclear multidimensional NMR investigation and here report the 1H, 13C, and 15N resonance assignments for the backbone and side chain nuclei of the pro-inflammatory cytokine interleukin-36α. 相似文献
20.
Arginine side-chains are often key for enzyme catalysis, protein–ligand and protein–protein interactions. The importance of arginine stems from the ability of the terminal guanidinium group to form many key interactions, such as hydrogen bonds and salt bridges, as well as its perpetual positive charge. We present here an arginine 13Cζ-detected NMR experiment in which a double-quantum coherence involving the two 15Nη nuclei is evolved during the indirect chemical shift evolution period. As the precession frequency of the double-quantum coherence is insensitive to exchange of the two 15Nη; this new approach is shown to eliminate the previously deleterious line broadenings of 15Nη resonances caused by the partially restricted rotation about the Cζ–Nε bond. Consequently, sharp and well-resolved 15Nη resonances can be observed. The utility of the presented method is demonstrated on the L99A mutant of the 19 kDa protein T4 lysozyme, where the measurement of small chemical shift perturbations, such as one-bond deuterium isotope shifts, of the arginine amine 15Nη nuclei becomes possible using the double-quantum experiment. 相似文献