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1.
Herv Canut Johann Bauer Gerhard Weber 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1999,722(1-2)
The review focuses on the multiple separating regimes that offers the free flow electrophoresis technique: free flow zone electrophoresis, isoelectric focusing, isotachophoresis, free flow step electrophoresis. Also, the feasibility to apply either interval or continuous flow electrophoresis is evaluated. The free flow zone electrophoresis regime is generally selected for the separation of cells, organelles and membranes while the other regimes find their largest fields of applications in the purification of proteins and peptides. The latter regimes present the highest resolution efficiency. Therefore, a large part of this review is devoted to the applicabilities of these different regimes to the purification of organelles and membrane vesicles at the preparative scale. Recent developments, both in instrumentation and procedures, are described. The major achievements in plant membrane fractionation obtained with free flow electrophoresis are outlined. The related procedures are both analytical and preparative: they separate tonoplast and plasma membrane simultaneously from the same homogenate, they discriminate for one type of membrane vesicles of opposite orientation, and process large quantities of membrane material by reason of the continuous flow mode. Recent advances using electromigration techniques that permit confirmation of the dynamic state of membranes, characterisation of complex membrane-dependent functions and discovery of new membrane-localised activities are presented. 相似文献
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The nucleotide sequence of a Sau3A1 restriction nuclease fragment that complemented an Escherichia coli chlD::Mu cts mutant strain was determined. DNA and deduced amino acid sequence analysis revealed two open reading frames (ORFs) that potentially codes for proteins with amino acid sequence homology with binding protein-dependent transport systems. One of the ORFs showed a sequence that encoded a protein with properties that were characteristic of a hydrophobic inner membrane protein. The other ORF, which was responsible for complementing a chlD mutant, encoded a protein with conserved sequences in nucleotide-binding proteins and hydrophilic inner membrane proteins in active transport systems. A proposal that the chlD locus is the molybdate transport operon is discussed in terms of the chlD phenotype. 相似文献
4.
Substrate specifity of the proton-driven hexose cotransport carrier in the plasmalemma of photoautotrophic suspension cells of Chenopodium rubrum L. has been studies through the short-term perturbation of 14C-labelled efflux of 3-O-methyl-d-glucose. Efflux, occurring exclusively via carrier-mediated exchange diffusion, is trans-stimulated by the substrate and trans-inhibited by the glucose-transport inhibitors phlorizin (K 1/2=7.9 mM) and its aglucon phloretin (K 1/2=84 μM); with both inhibitors, 3-O-methyl-d-glucose efflux may be blocked completely. Trans-stimulation of efflux (up to fourfold) by a variety of the d-enantiomers of neutral hexoses, including glucose (K 1/2=48 μM), 3-O-methyl-d-glucose (K 1/2=139 μM), and fructose (K 1/2=730 μM), but not by, for instance, d-allose, and l-sorbose, shows that carrier-substrate interaction critically involves the axial position at C-1 and C-3, respectively. We suggest that substrate binding by the Chenopodium hexose carrier involves both hydrophobic interaction with the pyran-ring and hydrogen-ion bonding at C-1 and C-3 of the d-glucose conformation. 相似文献
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Calli of P. argentatum were grown on a newly designed liquid nutrient flow-through system which facilitated the subculturing of calli and delayed
browning for 6 weeks. Friable calli were obtained on half-strength Gamborg B5-medium supplemented with 0.05 mgl−1 2,4-dichlorophenoxyacetic acid. Shoots developed on media supplemented with 0.2 mgl−1 benzylaminopurine but lacking 2,4-dichlorophenocyacetic acid. 相似文献
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M Juricek P Gruz J Veleminsky J Stanek K Kefurt J Moravcova J Jary 《Mutation research》1991,251(1):13-20
6-Azido-6-deoxy (AZd) derivatives of D-glucose, D-mannose, D-altrose, D-allose, L-idose, D-galactose, D-galactonic acid and D-galactitol, 3-azido-1,2-propanediol (azidoglycerol), 3,1-diazido-2-propanol (diazidoglycerol) and (at much higher doses) 2-azidoethanol were mutagenic in Salmonella typhimurium strains TA100 and TA1535. The mutagenic response was similar to that induced by sodium azide, i.e., the azido compounds failed to induce mutations in strain TA98, and mutagenesis was independent of plasmid pKM101, and independent of external activation. The specific mutagenicity (his+ rev/mmole) of AZd-glucose and AZd-galactose was decreased with increasing concentrations of D-glucose or D-galactose in the minimal agar medium and enhanced 100-fold or more when 0.2% citrate rather than 0.2% glucose served as the carbon source in the medium. Similarly, the mutagenic efficiency of azidoglycerol was inhibited by glycerol but not by D-glucose or D-galactose; however, the mutagenicity of sodium azide was not influenced by any of these carbon sources in the medium. The inhibition of the mutagenic action of azido hexoses and azido alcohols by non-azido structural analogs is assumed to reside in competition in transmembrane transport or for the metabolic pathways. 相似文献
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Experimental designs that include repeated measures of binary response variables over time and under different conditions are common in biology. In such settings, it is often desirable to characterize the response pattern over time. When response variables are continuous, this characterization can be made in terms of a growth model such as the Potthoff-Roy growth curve model. We illustrate how a similar growth curve modeling strategy can be implemented using weighted least squares (WLS) methods for binary response data. The growth models are constructed in terms of polynomial functions across marginal response. However, when growth models are fit to repeated binary response, the nonsignificant higher-order polynomial functions are dropped from the model, rather than used as covariates. Dropping the nonsignificant polynomials from the model will reduce the number of response functions, and help avoid small-sample problems that can occur when the number of correlated response functions is large and sample sizes are small. The reduced set of response functions are then modeled using WLS methods. We illustrate such models with an example of binary fly oviposition response (accept or reject) exhibited by two populations of flies at four ages to two types of fruit. 相似文献
9.
Abstract Adaptation may be the result of a change in affinity and/or number of cAMP-binding sites at the cell surface. To test this possibility we used agip 53, a mutant that does not synthesize cAMP in response to cAMP stimulation. cAMP induced a fast decrease in cAMP-binding to aggregation-competent cells, which reached a maximum at 10–20 s and was reversible with a t 0.5 of about 70 s. The decrease in cAMP-binding involved 46000 sites per cell and was mainly due to a reduction in the apparent affinity for cAMP-binding and to a smaller extent to slowly dissociating cAMP. Our results suggest that under these conditions only a fraction of the cAMP-binding sites at the cell surface are involved in transmembrane signalling, which is indeed observed for many of the physiological responses in Dictyostelium discoideum . 相似文献
10.
Zusammenfassung Die Zellkerne vonPseudolysimachion spicatum, Veronica cymbalaria undV. gentianoides enthalten zweierlei Eiweißkörper von je nach dem Entwicklungszustand unterschiedlicher Konsistenz. Bis zum Höhepunkt ihrer Entwicklung liegen sie als anscheinend amorphe flüssige oder gelartige Gebilde vor. Später tritt — mit gewebespezifischen Unterschieden — Verfestigung und Kristallisation ein, und zwar bei beiden nicht gleichzeitig und z. T. auch nur beim großen. Beiderlei Körper unterscheiden sich deutlich in physikalischer und chemischer Hinsicht, außerdem in ihrer Entwicklungsgeschichte und Strukturveränderung. Sie fehlen in den Schließzellen, im Antherentapetum, in den Pollenmutterzellen, Pollenkörnern, im Embryosack, im Endosperm und im Embryo.Die Zellkerne in der Blattepidermis vonPenstemon barbatus enthalten ebenfalls zweierlei Eiweißkörper. Davon liegt einer als kugeliges Gebilde, der andere als Kristallstapel vor.
Summary In the nuclei ofPseudolysimachion spicatum, Veronica cymbalaria, V. gentianoides there occur two different kinds of protein bodies. They clearly differ from one another in physical and chemical regard as well as in their ontogeny. At first they are amorphous, liquid or geluous. As a rule a consolidation or crystallization with differences according to the tissue takes place after the climax of the development, and that not at the same time within both bodies. In the stomata cells, pollen mother cells, in the embryo sac, in the endosperm, in the endothelium and in the embryo both bodies do not occur.The nuclei in the epidermis of the leaves ofPenstemon barbatus also contain two different kinds of protein bodies, one of them appearing as a round body, and the other one as a pile of crystal plates.相似文献