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排序方式: 共有397条查询结果,搜索用时 15 毫秒
1.
J R Vandenheede S D Yang W Merlevede 《Biochemical and biophysical research communications》1983,115(3):871-877
The major active protein phosphatase present in a rabbit skeletal muscle extract is associated with the glycogen particle and migrates in sucrose density gradient centrifugation as a Mr = 70,000 protein and contains modulator activity. Addition of extra modulator protein causes a time- and concentration-dependent conversion of the enzyme to an inactive FA-ATP, Mg-dependent form. The intrinsic modulator in the active phosphatase is destroyed by limited proteolysis without an appreciable change in the phosphatase activity. The proteolyzed active enzyme has a lower molecular weight (Mr = 40,000) and it reassociates with the modulator producing a FA-ATP, Mg-dependent enzyme form (Mr = 60,000). The modulator protein is used stoichiometrically in the activation of the ATP, Mg-dependent phosphatase. This is in agreement with the presence of one unit of modulator activity per unit of native spontaneously active phosphatase. 相似文献
2.
Jackie R. Vandenheede Sigrid Staquet Wilfried Merlevede 《Molecular and cellular biochemistry》1989,87(1):31-39
Summary Fractionation of rabbit skeletal muscle cytosol on Aminohexyl-Sepharose has resulted in the identification of a latent ATP, Mg-dependent protein phosphatase whose catalytic subunit is in the active conformation, but is inhibited by the presence of more than one modulator unit. The partially purified enzyme is converted to an inactive, kinase FA-dependent form upon incubation at 30°C unless modulator-specific polyclonal antibodies are added to the preparation. The immunoglobulins also relieve the inhibition which is responsible for the low basal phosphatase activity of the enzyme, and they counteract all of the heat-stable inhibitor activity present in the preparation. Addition of free catalytic subunit abolishes the inhibition of the latent enzyme in a dose-dependent way, but cannot prevent the inactivation process. The inactivated phosphatase and the original latent enzyme exhibit the same apparent M
r in sucrose density-gradient centrifugation (70 000) and in gel filtration (110 000).Abbreviations PMSF
Phenylmethanesulphonyl Fluoride
- TLCK
L-l-chloro-3-(4-tosylamido)-7-amino2-heptanone-hydrochloride
- TPCK
L-l-chloro-3-(4-tosvlamido)-4-phenyl-2-butanone 相似文献
3.
Characterization of glycogen-synthase phosphatase and phosphorylase phosphatase in subcellular liver fractions 总被引:3,自引:0,他引:3
Upon fractionation of a postmitochondrial supernatant from rat liver, the synthase phosphatase (EC 3.1.3.42) activity (assayed at high tissue concentrations) was largely recovered in the glycogen fraction and to a minor extent in the cytosol. In contrast, the phosphorylase phosphatase (EC 3.1.3.17) activity was approximately equally distributed between these two fractions, a lesser amount being recovered in the microsomal fraction. The phosphatase activities in the microsomal and glycogen fractions were almost completely inhibited by a preincubation with the modulator protein, a specific inhibitor of type-1 (ATP,Mg-dependent) protein phosphatases. In the cytosolic fraction, however, type-2A (polycation-stimulated) phosphatase(s) contributed significantly to the dephosphorylation of phosphorylase and of in vitro phosphorylated muscular synthase. Liver synthase b, used as substrate for the measurement of synthase phosphatase throughout this work, was only activated by modulator-sensitive phosphatases. Trypsin treatment of the subcellular fractions resulted in a dramatically increased (up to 1000-fold) sensitivity to modulator, a several-fold increase in phosphorylase phosphatase activity and a complete loss of synthase phosphatase activity. Similar changes occurred during dilution of the glycogen-bound enzyme. A preincubation with the deinhibitor protein, which is known to counteract the effects of inhibitor-1 and modulator, increased several-fold the phosphorylase phosphatase activity, but exclusively in the cytosolic and microsomal fractions. It did not affect the synthase phosphatase activity. Taken together, the results indicate the existence of distinct, multi-subunit type-1 phosphatases in the cytosolic, microsomal and glycogen fractions. 相似文献
4.
J R Vandenheede C Vanden Abeele W Merlevede 《Biochemical and biophysical research communications》1986,135(2):367-373
The activation as well as the inactivation of the ATP,Mg-dependent protein phosphatase has been shown to be totally dependent upon the presence of the modulator subunit. This modulator (inhibitor-2) is a heat stable protein and its isolation in pure form (32 kDa) always includes a boiling step. The boiled modulator fractions are known to be inhibitory to the phosphatase activity. Unboiled rabbit skeletal muscle preparations do not contain "free modulator", but two higher molecular weight complexes (70 kDa) can be isolated which have the 32 kDa modulator together with a 38 kDa protein. One complex is the already characterized inactive ATP,Mg-dependent phosphatase [FCM] while the second one, [MX], although seemingly of identical composition, does not exhibit phosphatase activity when measured under the usual conditions. The MX-complex does not inhibit the phosphatase activity unless subjected to a boiling step which dissociates the modulator subunit. The unboiled [MX] exhibits the activation as well as the inactivation characteristics of the free modulator. 相似文献
5.
6.
On the mechanism of activation of the ATP X Mg(II)-dependent phosphoprotein phosphatase by kinase FA 总被引:4,自引:0,他引:4
S Jurgensen E Shacter C Y Huang P B Chock S D Yang J R Vandenheede W Merlevede 《The Journal of biological chemistry》1984,259(9):5864-5870
The mechanism of activation of the Mg(II) X ATP-dependent phosphatase by the kinase FA has been investigated. The inactive protein phosphatase can be represented as FC X M where FC is the inactive catalytic component and M is the heat-stable modulator protein (also known as inhibitor-2). Phosphorylation of the modulator protein is demonstrated during activation of FC X M. In addition, continuous ATP hydrolysis during the activation is observed. This suggests that a cyclic phosphorylation-dephosphorylation reaction is continuously occurring during the activation. It is proposed that phosphorylation of the modulator protein causes an isomerization in FC to generate an active phosphatase. The activated phosphatase is capable of dephosphorylating the phosphorylated modulator. Upon dephosphorylation of modulator, the active phosphatase returns to its inactive form via a slow isomerization. 相似文献
7.
J Di Salvo D Gifford J R Vandenheede W Merlevede 《Biochemical and biophysical research communications》1983,111(3):912-918
A spontaneously active (Mr greater than 350,000) and an ATPMg-dependent phosphatase (Mr congruent to 140,000) were identified in bovine aortic smooth muscle. The spontaneously active phosphatase was effective in dephosphorylating both phosphorylase a (240nmol32P/min/mg) and phosphorylated myosin light chains (1000nmol32P/min/mg). In contrast, the ATPMg-dependent phosphatase was only effective in dephosphorylating phosphorylase a (400nmol32P/min/mg). Phosphorylase phosphatase activity of the ATPMg-dependent enzyme was suppressed by the well-characterized modulator protein (inhibitor-2), whereas the activity of the spontaneously active enzyme was unaffected. The aortic spontaneously active phosphatase did not convert to an ATPMg-dependent form when it was stored at 4 degrees or incubated at 30 degrees C in either the presence or absence of modulator protein. These findings suggest that spontaneous and ATPMg-dependent phosphatase activities described in these studies are probably ascribable to different enzymes. Since both phosphorylase and myosin light chains are phosphorylated when smooth muscle contracts these phosphatases may participate in coordinating arterial contractility and metabolism. 相似文献
8.
9.
10.
The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
相似文献