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排序方式: 共有121条查询结果,搜索用时 15 毫秒
21.
Shiro Okumura Tetsuyuki Akao Satoko Yamashita Tokio Ichimatsu Kuniyo Inouye 《Cytotechnology》2005,47(1-3):59-67
Proteins of plasma membrane could be an index of purification of the plasma membrane of animal cells. A convenient method
is proposed for determining the plasma membrane proteins by a surface plasmon resonance (SPR) biosensor. Biotinylated proteins
were observed only in the peripheral areas of MOLT-4 cells which were treated by 5-[5-(N-succinimidyloxycarbonyl) pentylamido] hexyl-d-biotinamide. The proteins on HeLa cells were also biotinylated. And then the membrane samples of the HeLa cells were injected
onto the avidin-immobilized SPR-surface, and components bound non-specifically on the surface were removed by a washout solution.
The amount of biotinylated protein (BP) was determined directly from the absolute resonance unit (RU) after injection of the
washout solution. In the method a reference surface was not needed. The amount of BP bound to the surface was gradually attenuated
with the repeated injection, and a method for calibrating the RU value was introduced by considering the ratio of attenuation
by every injection. The correlation between the BP titer calculated by the calibration and the theoretically-estimated one
was greatly improved. Three cycles of the BP determination on a sensor surface was performed successfully. During the purification
process of membrane fractions, the degree of purification as judged by the BP titer was in good agreement with the degree
of increase in aminopeptidase N activity in the membrane fraction. Thus, the BP titer could be used as an index for purification
of plasma membrane. 相似文献
22.
Hiroshi Morita Yuichiro Tomizawa Jun Deguchi Tokio Ishikawa Hiroko Arai Kazumasa Zaima Takahiro Hosoya Yusuke Hirasawa Takayuki Matsumoto Katsuo Kamata Wiwied Ekasari Aty Widyawaruyanti Tutik Sri Wahyuni Noor Cholies Zaini Toshio Honda 《Bioorganic & medicinal chemistry》2009,17(24):8234-8240
Cassiarin A 1, a tricyclic alkaloid, isolated from the leaves of Cassia siamea (Leguminosae), shows powerful antimalarial activity against Plasmodium falciparum in vitro as well as P. berghei in vivo, which may be valuable leads for novel antimalarials. Interactions of parasitized red blood cells (pRBCs) with endothelium in aorta are especially important in the processes contribute to the pathogenesis of severe malaria. Nitric oxide (NO) reduces endothelial expression of receptors/adhesion molecules used by pRBC to adhere to vascular endothelium, and reduces cytoadherence of pRBC to vascular endothelium. Cassiarin A 1 showed vasorelaxation activity against rat aortic ring, which may be related with NO production. A series of a hydroxyl and a nitrogen-substituted derivatives and a dehydroxy derivative of 1 have been synthesized as having potent antimalarials against P. falciparum with vasodilator activity, which may reduce cytoadherence of pRBC to vascular endothelium. Cassiarin A 1 exhibited a potent antimalarial activity and a high selectivity index in vitro, suggesting that the presence of a hydroxyl and a nitrogen atom without any substituents may be important to show antimalarial activity. Relative to cassiarin A, a methoxy derivative showed more potent vasorelaxant activity, although it did not show improvement for inhibition of P. falciparum in vitro. These cassiarin derivatives may be promising candidates as antimalarials with different mode of actions. 相似文献
23.
24.
Tokio Kogoma Nelda L. Subia Kaspar von Meyenburg 《Molecular & general genetics : MGG》1985,200(1):103-109
Summary
Escherichia coli rnh mutants lacking ribonuclease H (RNase H) activity can tolerate deletion of the origin of DNA Replication (oriC) and transposon-insertional inactivation of an initiator gene (dnaA:Tn10). Introduction of the recA200 allele encoding a thermolabile RecA protein intornh
– dnaA: Tn10 and rnh
–
oriC mutants strains rendered DNA synthesis and colony formation of these mutants temperature sensitive. The temperature sensitivity and the broth sensitivity (Srm–) of the rnh
– dnaA: Tn10 recA200 strain was suppressed by the presenceof plasmids (pBR322 derivatives) carrying dnaA
+only when the intact oriC site was present on the chromosome. Lack of RNase H activity neither promoted replication of minichromosomes (pOC24 and pasn20) in the absence of required DnaA+ protein nor inhibited dnaA
+–dependent minichromosome replication. These results led to the conclusion that RNase H is not directly involved in the events leading to initiation of DNA replication at oriC. Rather, it functions as a specificity factor by eliminating certain forms of RNA-DNA hybrids which could otherwise be used to prime DNA replication at sites other than oriC. 相似文献
25.
26.
Summary
Escherichia coli rnh mutants deficient in ribonuclease H (RNase H) are capable of DNA replication in the absence of protein synthesis. This constitutive stable DNA replication (SDR) is dependent upon the recA
+ gene product. The requirement of SDR for recA
+ can be suppressed by rin mutations (for recA+-independent), or by lexA(Def) mutations which inactivate the LexA repressor. Thus, there are at least three genetically distinct types of SDR in rnh mutants: recA
+-dependent SDR seen in rnh
- rin+ lexA+ strains, recA
+-independent in rnh
- rin- lexA+, and recA
+-independent in rnh
- rin+ lexA(Def). The expression of SDR in rin
- and lexA(Def) mutants demonstrated a requirement for RNA synthesis and for the absence of RNase H. The suppression of the recA
+ requirement by rin mutations was shown to depend on some new function of the recF
+ gene product. In contrast, the suppression by lexA-(Def) mutations was not dependent on recF
+. The lexA3 mutation inhibited recA
+-dependent SDR via reducing the amount of recA
+ activity available, and was suppressed by the recAo254 mutation. The SDR in rnh
- rin- cells was also inhibited by the lexA3 mutation, but the inhibition was not reversed by the recAo254 mutation, indicating a requirement for some other lexA
+-regulated gene product in the recA
+-independent SDR process. A model is presented for the regulation of the expression of these three types of SDR by the products of the lexA
+, rin+ and recF
+ genes. 相似文献
27.
Summary The thermosensitivity of dnaA(Ts) mutations can be suppressed by integration of plasmid F (integrative suppression). In the light of the recent finding that F requires DnaA protein for both establishment and maintenance, integrative suppression of 11 dnaA(Ts) mutations by a mini-F, pML31, integrated near oriC was examined. The plating efficiency of integratively suppressed strains was dnaA(Ts) allele-dependent and medium-dependent. The initiation capability of suppressed dnaA(Ts) strains lacking the oriC site and their F- counterparts was determined at various temperatures between 30°C and 42°C. The degree of integrative suppression measured by the initiation capability varied in a dnaA(Ts) allele-dependent manner. F-directed DNA replication was most affected by the dnaA(Ts) mutations mapping in the middle of the gene whereas oriC-dependent replication was most thermosensitive in strains carrying mutations mapping in the carboxy-terminal half of the gene. The results indicated that the integrative suppression by F plasmid is a DnaA-dependent process and suggested that the requirements for DnaA protein in the oriC-dependent replication and F replication processes are qualitatively different. 相似文献
28.
Carbohydrates and proteins in surface water during a bloom ofMictrocystis, which is the dominant summer phytoplankton in Lake Suwa, were analyzed in order to evaluate the function ofMicrocystis in organic matter metabolism. Glucose was the predominant sugar constituent of the cellular carbohydrate fraction and decreased
in quantity from inside towards the outside of the cell through the slime layer. Other constituent sugars, on the other hand,
were present in larger proportions in the lake water. Although the sugar composition of the cells did not change in July and
August, during the first period of theMicrocystis bloom, it changed appreciably in September when the water temperature decreased below 20°C accompanied by the decrease in
solar radiation and a marked change in nutrient concentration.
It appears that the sugar composition of the cells may change in response to some environmental stresses. In addition, a temporal
change in the sugar composition was found, particularly in the fraction containing the slime extracted by shaking. Among the
constituent amino acids of the cells, the percentage of arginine, aspartic acid and leucine decreased from inside toward the
outside of the cell, while glutamic acid, threonine, serine and glycine showed an opposite trend. In contrast to the carbohydrates,
the percentage composition of each amino acid varied little throughout the period of the bloom. 相似文献
29.
Tokio Kogoma 《Journal of molecular biology》1976,103(1):191-197
In the Escherichia coli dnaB mutant BT165/70 were observed two types of temperature sensitivity of DNA replication: one slow but irreversible, occurring before the initiation of DNA replication, and the other instant but reversible, occurring during replication. These two types of temperature sensitivity appear to result from the single dnaB mutation. The observation suggests two different states of the dnaB gene product within the cell. Interaction of the dnaB protein with other components of the hypothetical replication complex is suggested. A temperature-insensitive revertant (second site mutation) of BT165/70 was isolated whose phenotype suggests an alteration in the interacting ability of the revertant protein. 相似文献
30.
Toshihiko Akiba Yuichi Abe Yoshitomo Kusaka Tokio Ichimatsu Tetsuyuki Akao Eiichi Mizuki Ryuta Kanai 《Journal of molecular biology》2009,386(1):121-149
Parasporin-2 is a protein toxin that is isolated from parasporal inclusions of the Gram-positive bacterium Bacillus thuringiensis. Although B. thuringiensis is generally known as a valuable source of insecticidal toxins, parasporin-2 is not insecticidal, but has a strong cytocidal activity in liver and colon cancer cells. The 37-kDa inactive nascent protein is proteolytically cleaved to the 30-kDa active form that loses both the N-terminal and the C-terminal segments. Accumulated cytological and biochemical observations on parasporin-2 imply that the protein is a pore-forming toxin. To confirm the hypothesis, we have determined the crystal structure of its active form at a resolution of 2.38 Å. The protein is unusually elongated and mainly comprises long β-strands aligned with its long axis. It is similar to aerolysin-type β-pore-forming toxins, which strongly reinforce the pore-forming hypothesis. The molecule can be divided into three domains. Domain 1, comprising a small β-sheet sandwiched by short α-helices, is probably the target-binding module. Two other domains are both β-sandwiches and thought to be involved in oligomerization and pore formation. Domain 2 has a putative channel-forming β-hairpin characteristic of aerolysin-type toxins. The surface of the protein has an extensive track of exposed side chains of serine and threonine residues. The track might orient the molecule on the cell membrane when domain 1 binds to the target until oligomerization and pore formation are initiated. The β-hairpin has such a tight structure that it seems unlikely to reform as postulated in a recent model of pore formation developed for aerolysin-type toxins. A safety lock model is proposed as an inactivation mechanism by the N-terminal inhibitory segment. 相似文献