We report that cation-selective transmembrane pores formed by synthetic p-octiphenyl beta barrels with internal aspartate residues can be transformed into anion-permeable metallopores with internal Mg(2+)-aspartate complexes. These metallopores are shown to be useful for fluorimetric sensing of a broad variety of organic anions of biological relevance such as phytate, heparin, thiamine phosphates, and adenosine triphosphate. The negligible flippase activity measurable for Mg(2+)-free pores indicates that transmembrane p-octiphenyl beta barrels do not disturb the lipid bilayer suprastructure, in other words, they form barrel-stave rather than toroidal pores. 相似文献
Qbeta replicase functioning in Escherichia coli is an RNA-dependent RNA polymerase composed of one phage-coded subunit and three host-coded proteins: ribosomal protein S1, and protein elongation factors EF-Tu and EF-Ts. Qbeta replicase lacking ribosomal protein S1 (alpha-less replicase) is capable of replicating some small RNAs. We attempted to create functional alpha-less replicase by co-expression of the mRNAs that code for the subunits of alpha-less replicase in a rabbit reticulocyte cell-free translation system. Replicase activity, however, could not be detected when both EF-Tu and EF-Ts were co-expressed with the phage-coded subunit. On the other hand, active alpha-less replicase was obtained when an EF-Ts-EF-Tu fusion protein was co-expressed with the phage-coded subunit. Consequently, we succeeded in generating genetically engineered active alpha-less Qbeta replicase which functions in a eukaryotic cell-free system. 相似文献
We have produced micrometer-sized calcium alginate beads referred to as "bio-beads" that encapsulate plasmid DNA molecules carrying a reporter gene. In order to evaluate the efficiency of the bio-beads in mediating genetic transfection, protoplasts isolated from cultured tobacco cells (BY-2) were transfected with bio-beads containing a plasmid that carries the modified green fluorescent protein gene CaMV35S-sGFP. With the bio-beads treatment, approximately ten-fold higher GFP expression was observed after 24 h incubation compared to that with the conventional method using a naked plasmid solution. Transfection was up to 0.22% efficient. These results indicate that bio-beads have a possibility for efficient transformation in plants. 相似文献
In recent textured image segmentation, Bayesian approaches capitalizing on computational efficiency of multiresolution representations have received much attention. Most of the previous researches have been based on multiresolution stochastic models which use the Gaussian pyramid image decomposition. In this paper, motivated by nonredundant directional selectivity and highly discriminative nature of the wavelet representation, we present an unsupervised textured image segmentation algorithm based on a multiscale stochastic modeling over the wavelet decomposition of image. The model, using doubly stochastic Markov random fields, captures intrascale statistical dependencies over the wavelet decomposed image and intrascale and interscale dependencies over the corresponding multiresolution region image. 相似文献
In order to determine the ferrous and ferric ion capacities: 3
for an MgO-saturated MgO + CaO + Al2O3 slag, two experiments were carried out at 1873 K: (1) the distribution of iron between FexO dilute slags of the system and Pt + Fe alloys under controlled atmosphere, and (2) the equilibrium among molten iron or
iron alloys, magnesiowustite, and molten slags. Although the activity of iron and the partial pressure of oxygen in each experiment
are remarkably different, the values of the ferrous and ferric ion capacities agree well with each other. The influence of
the MgO:CaO:Al2O3 ratio on the values of
and
was found to be limited within the experimental composition range. Using
and
, the relationship between total iron content, (pct FeT), and partial pressure of oxygen,
, under iron saturation was calculated. The change in log
with respect to the bulk slag composition is less than 0.2 within the range of (pct FeT) < 5. 相似文献
An input system for CAD is developed to construct a part model within a computer from a hand-written sketch. The sketch is drawn based on the technical illustration method. The shape of the input part is constructed by the combination of cuboids and cylinders at present. A coloured illustration is adopted for the ease of the shape recognition and for the input of the technological information.
The illustration is fed into the computer via a black and white ITV. Colours are identified referring to the brightness of the input image. The constitutive bodies, the geometric element with the technological information and the content of the technological information are recognized through image processing such as noise filtering, thinning of the contours, detection of lines and so on. The input system outputs a set of commands to the modelling system. The integrated part model which includes not only the geometrical information but also the technological information of the part is constructed by the connected modelling system CIMS/MODE.
The combination of the input system and the modelling system can support the designer to construct the detailed part model within the computer effectively. It is expected to extend the ability of the input system to identify general hand-written illustrations so that the input method will be more practical and useful. 相似文献
The direct transfer of genetic materials into mammalian cells is an indispensable technique. We have developed calcium alginate (CA) microbeads which can deliver plasmid DNAs and yeast artificial chromosomes into plant and yeast cells. In this paper, we demonstrate the effective transfection of mammalian cells by CA microbeads immobilizing plasmid DNAs. The transfection was performed using the pEGFP-C1 plasmid containing the cytomegalovirus (CMV) promoter and enhanced green fluorescent protein (EGFP) gene. The transient expression of EGFP was observed 24 h after transfection. The expression efficiency was maximum when the concentration of sodium alginate was 1% and the amount of plasmid DNA was increased to 100 microg. The expression efficiency of our method using CA microbeads is 2-10 times higher than that of the polyethylene glycol (PEG) method. Our results suggest that the CA microbead mediated transfection of mammalian cells effectively delivers genetic materials into mammalian suspension cells. 相似文献
When recombinant Chinese hamster ovary cells were treated with pertussis toxin or genistein, not only lysophosphatidic acid (LPA) but also phosphatidic acid (PA) failed to stimulate progression through the cell cycle in serum-free culture, suggesting that PA and LPA induce cell growth through the same signal transduction pathway. Cell cycle analysis also indicates that cell growth promoted by PA results in enhanced protein production. 相似文献
Quasicrystals are solids that exhibit symmetries long thought forbidden in nature. Since their discovery in a rapidly solidified Al-Mn alloy in 1984, the central issue in the field has been to understand why they form. Are they energetically stable compounds or stabilized by entropy? In recent years, major strides have been made in determining atomic structure, largely by direct imaging using advanced electron microscopy. One system is now known to be energetically stabilized, and quasicrystals are therefore firmly established as a new physical state of matter. They represent a unique packing of atomic clusters some tens of atoms in size, with substantial localized fluctuations, referred to as phasons. Understanding phasons may in future allow their unique macroscopic properties to be tailored for useful materials applications. 相似文献
The transient capacitance technique has been used to study the chromium-related levels in the silicon band gap. Chromium was diffused at temperature of 1100 and 1150°C for 0.5 and 3 hr. Five different levels at Ec?0.11 eV, Ec?0.21 eV, Ec?0.28 eV, Ec?0.36 eV and Ec?0.45 eV were obtained from the Arrheniu plots of the electron thermal-emission rates. The number of levels in the upper half of the band gap decreased from five to two with an increase of Cr-diffusion period. Two levels were located at Ec?0.20 eV (donor) and Ec?0.43 eV (acceptor). A donor level was also observed at Ev + 0.25 eV. The donor level was not affected by the diffusion condition. The majority carrier capture cross sections of the three dominant levels have been measured by the transient capacitance technique modified by the pulse transformer. The values were σn = 4.1 × 10?15 cm2 for the upper donor at Ec?0.20 eV, σn = 2.0 × 10?16 cm2 for the acceptor at Ec ?0.43 eV and σp = 9.1 × 10?18 cm2 for the lower donor at Ev + 0.25 eV, and were independent of temperature. The three dominant levels are due to distinct chromium centers. 相似文献