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排序方式: 共有157条查询结果,搜索用时 843 毫秒
31.
E. Morelos-López A. Cabral-Prieto N. Nava F. García-Santibañez C. Nosetti 《Hyperfine Interactions》2014,226(1-3):737-746
Heat induced surface changes on A533B stainless steel were followed by XRD and CXMS techniques. Whereas the XRD patterns of the studied A533B samples were characteristic of α-Fe phase only, the surface Mössbauer spectrum showed a broad sextet, being fitted with two magnetic patterns whose hyperfine magnetic fields were 33 and 31 T associated with a pure and perturbed α-Fe phase, respectively and a broad singlet with an isomer shift δ A533B = ?0.115(4) mms $^{-1}/\alpha $ -Fe, characteristic of the γ-Fe phase. This singlet, probably, arising from the samples’ surface only was further analyzed by using a singlet and a quadrupole doublet. From hyperfine distribution and discrete value calculations of their corresponding hyperfine parameters, the quadrupole interaction was the most affected by thermal treatments ranging from 300° to 700 °C showing a slight decrease at 600 °C. The average values of the hyperfine parameters were δ 1 = ? 0.110(6) mms $^{-1}/\alpha $ -Fe for the singlet, and δ 2 = ?0.081 (6) mms $^{-1}/\alpha $ -Fe and Δ2 = 0.143(7) mm/s) for the quadrupole doublet, respectively. In spite of the temperature dependence of the quadrupole splitting on the doublet, which was higher than that of the isomer shifts of both patterns, only a single defect type was suggested, being associated with monovacancias near the 57Fe sites. 相似文献
32.
Nava?Chapnik Anat?Levit Masha?Y.?Niv Oren?FroyEmail author 《Applied biochemistry and biotechnology》2012,166(7):1703-1710
The innate immunity utilizes a battery of broad-spectrum antibacterial cationic polypeptides (3–5 kDa), among them defensins.
In humans, defensins are the first line of defense against pathogens and their expression has been implicated in several diseases.
The antibacterial activity of defensins is generally ascribed to their overall positive charge, which enables them to disrupt
bacterial membrane integrity and function, but their active surface has not been fully elucidated. To perform structural and
functional assays, an efficient, high-yield, easy-to-use expression and purification system must be established. Up to now,
most efforts to obtain larger quantities of active recombinant defensins have been only moderately successful. Herein, we
report the establishment of an efficient, high-yield expression and purification system for human defensin 5 (HD-5). Using
site-directed mutagenesis, we pinpoint several arginine residues and Y27 as important for HD-5 antibacterial activity. Our
expression and purification system can be harnessed for structure/activity relationship studies of defensins in particular
and small polypeptides in general. 相似文献
33.
Stolichnov I Maksymovych P Mikheev E Kalinin SV Tagantsev AK Setter N 《Physical review letters》2012,108(2):027603
Polarization reversal in ferroelectric nanomesas of polyvinylidene fluoride with trifluoroethylene has been probed by ultrahigh vacuum piezoresponse force microscopy in a wide temperature range from 89 to 326 K. In dramatic contrast to the macroscopic data, the piezoresponse force microscopy local switching was nonthermally activated and, at the same time, occurring at electric fields significantly lower than the intrinsic switching threshold. A "cold-field" defect-mediated extrinsic switching is shown to be an adequate scenario describing this peculiar switching behavior. The extrinsic character of the observed polarization reversal suggests that there is no fundamental bar for lowering the coercive field in ferroelectric polymer nanostructures, which is of importance for their applications in functional electronics. 相似文献
34.
Jennifer C. Rea G. Tony Moreno Lisa Vampola Yun Lou Bjorn van Haan Guillaume Tremintin Laura Simmons Adrian Nava Yajun Jennifer Wang Dell Farnan 《Journal of chromatography. A》2012
Size exclusion chromatography (SEC) is widely used in the characterization and quality control of therapeutic proteins to detect aggregates. Aggregation is a carefully monitored quality attribute from the earliest stages of clinical development owing to the possibility of eliciting an immunogenic response in the patient. During early stage molecule assessment for cell culture production, small-scale screening experiments are performed to permit rapid turn-around of results so as to not delay timelines. We report the development of a capillary SEC methodology for preliminary molecule assessment to support the evaluation of therapeutic candidates at an early stage of development. By making several key modifications to a commercially available liquid chromatography system, we demonstrate a platform process to perform capillary SEC with excellent precision, picogram sensitivity and good ruggedness. The limit of quantitation was determined to be approximately 15 pg; picogram sensitivity for SEC analysis of monoclonal antibodies had not been achieved prior to this work. In addition, we have developed a method to capture low levels of antibody (1 μg/mL) from harvested cell culture fluid (HCCF) for capillary SEC analysis. Up to 40% recovery efficiency was achieved using this micro-recovery method on 3 mL HCCF samples. Using early stage cell culture transient transfection samples, which typically have much lower titers than stable cell line samples, we demonstrate a consistent method for analyzing aggregates in low protein concentration HCCF samples for molecule assessment and early stage candidate screening. 相似文献
35.
The relative reaction rates of several silatranes (derivatives of 2,8.9-trioxa-5-aza- 1-silatricyclo[3.3.3.01,5]undecane) and HgCl2 in acetone-d6to yield the corresponding organomercury compound are of the order of e.g., 5 × 10?1 1 mol?1 sec?1 or slightly less, a rate that is unexpectedly high compared to the essentially inert parent organotrialkoxysilanes. Thus, the apical Si&.zsbnd;C bond of the silatrane is extraordinarily susceptible to direct electrophilic attack by mercury(II). The rates decrease in the order CH2CH, C6H5, p-ClC6H4 > CH3 > CH3CH2, CH3CH2CH2 > C6H11, ClCH2, Cl2CH, CH3CH2O. The effects of varying the solvent and the counterions are noted, and the probable mechanism is discussed. 相似文献
36.
The 1H, 13C and 29Si nuclear magnetic resonance spectra of the parent compound and twelve derivatives of 2,8,9-trioxa-5-aza-1-silatricyclo[3.3.3.01,5]undecane (silatrane) are discussed. Effective Taft polarity constants for the silatrane substituents are proposed. An equation is developed to correlate the 29Si NMR chemical shifts of the silatranes with the corresponding organo-triethoxysilanes. 相似文献
37.
A. Bösch H. Müller-Krumbhaar O. Shochet 《Zeitschrift für Physik B Condensed Matter》1995,97(2):367-377
We introduce a variant of a recently proposed method of rotated lattices for numerical treatment of moving boundary problems. The usual lattice introduced for numerical computation of phase-field models gives rise to unphysical metastable states and anisotropy. In the present case we rotate and shift the lattice by random angles and fractions of a lattice constant. We show that a twelve point interpolation formula is adequate to keep numerical interpolation errors sufficiently localized. This removes the unphysical metastabilities and makes the model fully isotropic. This is demonstrated by a few example-calculations for dendritic pattern formation. 相似文献
38.
39.
With a polarized double‐zeta basis set, we carried out MP2 and density functional theory geometry optimization of bis(2,2′‐bipyridine) interacting either with Cu(I) or Ag(I). The computed gas‐phase geometries of both Cu and Ag complexes present tetrahedral distortions around the ions. However, geometry optimization on Cu or Ag ions complexing with ammonia molecules yield perfect tetrahedral coordination and interaction energies comparable to those of the bis(2,2′‐bipyridine) complexes. Solid‐state laboratory studies on complexes of the same metal ions with substituted bis(2,2′‐bipyridine) revealed tetrahedral distortions around the ions, even stronger than those computed in the gas phase. From our analysis of the potential interaction energies we conclude that the origin of the larger distortions in the solid state result from stacking interactions. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 395–404, 2003 相似文献
40.