全文获取类型
收费全文 | 85篇 |
免费 | 1篇 |
专业分类
86篇 |
出版年
2015年 | 1篇 |
2013年 | 3篇 |
2012年 | 3篇 |
2010年 | 2篇 |
2009年 | 1篇 |
2008年 | 4篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 8篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 6篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有86条查询结果,搜索用时 15 毫秒
1.
A new chromatographic material based on beads of macroporous crosslinked agarose containing ferric oxide particles was used for enrichment of gp70--the envelope glycoprotein of feline leukemia virus (FeLV). Free gp70 was purified from cell culture fluid in one step with a recovery of 50 to 60% and a purification of about 60 times. The described procedure is a suitable first step for the purification of gp70 from large volumes of cell culture fluid. 相似文献
2.
Some observations on the choice of detergent for solubilization of the human erythrocyte membrane. 总被引:1,自引:0,他引:1 下载免费PDF全文
Solubilization of the human erythrocyte membrane by seven detergents is described. Components released into the supernatant or retained in the residue were identified by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Two non-ionic detergents exhibiting little u.v. absorption were more efficient than u.v.-absorbing Triton X-100. Evidence is presented of an interchange between protein PAS 1 and protein PAS 2. 相似文献
3.
This paper describes the separation of proteins by displacement electrophoresis on columns packed with cellulose powder as a stabilizing medium. Cellulose has virtually no molecular sieving properties and thus differs from dextran, polyacrylamide, and agarose in this respect. Therefore, without the risk of unstacking, columns packed with cellulose permit conventional elution of the protein zones and the use of a counter flow (to increase the effective length of the bed). For the same reason, electroosmotic flow is less disturbing. A continuous elution-migration technique adapted to suit the special requirements of displacement electrophoresis gave better separation than was obtainable by conventional elution. Normal human serum and a fresh hemolysate from human erythrocytes were used as samples. An expression for the volume velocity of the boundaries is derived. This parameter can be used to determine the maximum duration of a run and a suitable pump speed when continuous elution or a counter flow is employed. The special advantages of displacement electrophoresis in cellulose beds are discussed as well as general disadvantages of the displacement technique, including the risk that proteins precipitate during a run. 相似文献
4.
Biomanipulation as an Application of Food-Chain Theory: Constraints, Synthesis, and Recommendations for Temperate Lakes 总被引:23,自引:2,他引:23
Lars-Anders Hansson Helene Annadotter Eva Bergman Stellan F. Hamrin Erik Jeppesen Timo Kairesalo Eira Luokkanen Per-Åke Nilsson Martin Søndergaard John Strand 《Ecosystems》1998,1(6):558-574
The aim of this review is to identify problems, find general patterns, and extract recommendations for successful biomanipulation.
An important conclusion is that the pelagic food chain from fish to algae may not be the only process affected by a biomanipulation.
Instead, this process should be viewed as the “trigger” for secondary processes, such as establishment of submerged macrophytes,
reduced internal loading of nutrients, and reduced resuspension of particles from the sediment. However, fish reduction also
leads to a high recruitment of young-of-the-year (YOY) fish, which feed extensively on zooplankton. This expansion of YOY
the first years after fish reduction is probably a major reason for less successful biomanipulations. Recent, large-scale
biomanipulations have made it possible to update earlier recommendations regarding when, where, and how biomanipulation should
be performed. More applicable recommendations include (1) the reduction in the biomass of planktivorous fish should be 75%
or more; (2) the fish reduction should be performed efficiently and rapidly (within 1–3 years); (3) efforts should be made
to reduce the number of benthic feeding fish; (4) the recruitment of YOY fish should be reduced; (5) the conditions for establishment
of submerged macrophytes should be improved; and (6) the external input of nutrients (phosphorus and nitrogen) should be reduced
as much as possible before the biomanipulation. Recent biomanipulations have shown that, correctly performed, the method also
achieves results in large, relatively deep and eutrophic lakes, at least in a 5-year perspective. Although repeated measures
may be necessary, the general conclusion is that biomanipulation is not only possible, but also a relatively inexpensive and
attractive method for management of eutrophic lakes, and in particular as a follow-up measure to reduced nutrient load.
Received 14 April 1998; accepted 31 August 1998 相似文献
5.
Four of the membrane proteins from Acholeplasma laidlawii that are soluble in the nonionic detergent Tween 20 have been purified by preparative electrophoretic techniques utilizing different supporting media. The last purification step for two of the major proteins was a preparative polyacrylamide gel electrophoresis performed in the absence of any detergent. The proteins were recovered by continuous elution. The purity of the fractions was examined by analytical polyacrylamide gel electrophoresis and crossed immunoelectrophoresis. Two of the minor proteins were purified by dextran gel electrophoresis as the final step, which was also performed in a detergent-free buffer. The separation was followed by scanning the dextran gel in ultraviolet light. The proteins were recovered by slicing the gel and degrading the gel slices with dextranase. The homogeneity of the fractions was checked by electroimmunoassay. 相似文献
6.
K.-E. Johansson H. Pertoff S. Hjertén 《International journal of biological macromolecules》1979,1(3):111-118
Methods for the purification of the four major proteins and two of the minor proteins in the Tween 20-soluble extract of A. laidlawii membranes have previously been described. The last step in the purification procedure involved an electrophoresis in a detergent-free buffer, where the concentration of Tween could be reduced by up to 2000 times. The purified proteins were found to remain soluble after removal of the bulk of the detergent. Solutions of the different protein samples contained 3 30 detergent molecules per protein molecule as determined by gas-liquid liquid chromatography. Some of the protein solutions also contained natural membrane lipids. It was probably only a fraction of detergent molecules and lipids, which was bound to the protein. Complete amino acid analysis showed that none of the proteins contained amino sugars and only one of them contained half-cystine. The specific absorbances and the molar absorption coefficients were calculated from the absorption spectra. The hydrophobicities and the partial specific volumes were calculated from the amino acid composition. The hydrophobicity values did not differ significantly from those of non-membrane proteins. Attempts to determine the sedimentation coefficients and the molecular weights were done ultracentrifugation after removal of the bulk of the detergent. The molecular weights, as determined by ultracentrifugation, were in general higher than the molecular weights determined by polyacrylamid-gel electrophoresis in sodium dodecyl sulphate (SDS), indicating that most of the proteins formed aggregates upon reducing the concentration of Tween 20. The size of these aggregates was not influenced by storage of the proteins at 0 C but it seemed to be highly affected by the speed and the time of centrifugation. The electrophoretic mobolities of the proteins were determined by free zone electrophoresis. Crossed immunoelectrophoresis was utilized to demonstrate that the Tween 20-soluble membrane proteins were not undergoing proteolysis during the preparation procedure. 相似文献
7.
Rinaldi R Aniya Y Svensson R Eliasson E Swedmark S Shimoji M Morgenstern R 《Chemico-biological interactions》2004,147(2):163-172
Microsomal glutathione transferase 1 (MGST1) can become activated up to 30-fold by several mechanisms in vitro (e.g. covalent modification by reactive electrophiles such as N-ethylmaleimide (NEM)). Activation has also been observed in vivo during oxidative stress. It has been noted that an NADPH generating system (g.s.) can activate MGST1 (up to 2-fold) in microsomal incubations, but the mechanism was unclear. We show here that NADPH g.s treatment impaired N-ethylmaleimide activation, indicating a shared target (identified as cysteine-49 in the latter case). Furthermore, NADPH activation was prevented by sulfhydryl compounds (glutathione and dithiothreitol). A well established candidate for activation would be oxidative stress, however we could exclude that oxidation mediated by cytochrome P450 2E1 (or flavine monooxygenase) was responsible for activation under a defined set of experimental conditions since superoxide or hydrogen peroxide alone did not activate the enzyme (in microsomes prepared by our routine procedure). Actually, the ability of MGST1 to become activated by hydrogen peroxide is critically dependent on the microsome preparation method (which influences hydrogen peroxide decomposition rate as shown here), explaining variable results in the literature. NADPH g.s. dependent activation of MGST1 could instead be explained, at least partly, by a direct effect observed also with purified enzyme (up to 1.4-fold activation). This activation was inhibited by sulfhydryl compounds and thus displays the same characteristics as that of the microsomal system. Whereas NADPH, and also ATP, activated purified MGST1, several nucleotide analogues did not, demonstrating specificity. It is thus an intriguing possibility that MGST1 function could be modulated by ligands (as well as reactive oxygen species) during oxidative stress when sulfhydryls are depleted. 相似文献
8.
In this paper we describe a fast and mild method based on the use of a unique cation exchanger and buffers containing ethylene glycol and salt for the purification of the myelin basic protein (MBP; MW 18.5 kDa). MBP thus purified hydrolyses catalytically p-nitrophenyl acetate. This esterase activity facilitates not only the purification of MBP but also indicates that probably it is in its native state, i.e. there is a good chance that the purified molecules are structurally and chemically identical. This is a prerequisite to obtain crystals appropriate for x-ray diffraction and other studies.Abbreviations used MBP
myelin basic protein
- MW
molecular weight
- kDa
kilo Dalton
- octyl-POE
n-octylpolydisperse oligooxyethylene
- CHAPS
3-3-cholamidopropyl dimethylammonio-1-propane-sulfonate
- CTAB
cetyltrimethylammonium bromide
- SDS
sodium dodecyl sulfate
- SDS-PAGE
polyacrylamide gel electrophoresis in the presence of SDS
- G 3707
heptaoxyethylene lauryl ether
- TWEEN-20
polyoxyethylenesorbitan-monolaurat
- EDTA
ethylenediaminetetraacetic acid
- HEPES
N-(2-hydroxyethyl)-piperazine-N-(2-ethanesulfonic acid) 相似文献
9.
A method is described for on-line enrichment/zone sharpening of a sample of negatively charged proteins (an analogous method for cationic proteins can be designed). The sample is applied on the top of a 5-mm thick layer of a neutral polyacrylamide gel which rests on another 5-mm thick, large-pore polyacrylamide gel which contains positively charged groups. The latter gel layer is attached to the neutral gel column, used for the electrophoretic separation of the proteins. When a voltage is applied the proteins start migrating and become electrostatically adsorbed at the top of the charged, large-pore gel layer (pH 5.4). With the upper electrode vessel filled with a buffer of a pH higher (pH 7.7) than that employed in the enrichment step and with a voltage between the electrodes, these enriched proteins are released (because the enrichment gel is non-charged at pH 7.7) with zone sharpening and migrate into the 5-cm long column (i.d. 5 mm) of a neutral, large-pore polyacrylamide gel for electrophoretic analysis. Upon the electrophoretic migration from the enrichment gel into the separation gel a second zone sharpening may occur, if the increase in pH from 5.4 to 7.7 in the separation gel is not close to momentary. By employing colored test proteins the efficiency of the enrichment step is visually illustrated by a picture. The principle of the concentration method described has been employed also in chromatographic experiments and can with appropriate modifications also be used in other electrophoretic methods, such as capillary electrophoresis. 相似文献
10.
Wubshet Mamo Ferenc Rozgonyi Stellan Hjertén Torkel Wadström 《FEMS microbiology letters》1987,48(1-2):195-200
Abstract The surface hydrophobicity of cells of Staphylococcus aureus strains isolated from bovine mastitis grown on conventional agar and broth media was drastically reduced after incubation with bovine milk. Strains grown in high carbohydrate-high salt media yielded cells with reduced surface hydrophobicity compared to cells grown in conventional media, and adding bovine milk to minimal medium also yielded cells with reduced surface hydrophobicity, as determined by hydrophobic interaction chromatography and the salt aggregation test. Incubation of strains in milk and growth in a medium supplemented with bovine milk also significantly changed bacterial surface charge as determined by free-zone electrophoresis. Strains with high or with decreased adsorptive and aggregating properties did not produce surface capsule or slime. Heat treatment (60° C or 80° C) of the bacterial suspensions did not significantly change their adsorptive and aggregating properties. 相似文献