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排序方式: 共有92条查询结果,搜索用时 15 毫秒
1.
Levans produced by four Zymomonas mobilis strains showed antitumour activity against sarcoma 180 and Ehrlich carcinoma in Swiss albino mice. Levans from two strains (ZAP and CP4) had the highest effects. NMR analysis showed that the polymers were composed only of fructose units. The results suggested that the antineoplasic effect is associated to the polysaccharide molecular weight and that a particular molecular weight range may be responsible for this effect. 相似文献
2.
Uno Lindberg Clarence E. Schutt Eva Hellsten Ann-Christine Tjder Thomas Hult 《Biochimica et Biophysica Acta (BBA)/General Subjects》1988,967(3)
In the purification of proline hydroxylase by affinity chromatography on poly(L-proline)-Sepharose it was found earlier that two other components, profilin and the complex profilin-actin, also bind with high affinity to this matrix. We have exploited this observation to develop a rapid procedure for the isolation of profilin and profilin-actin complexes in high yields directly from high-speed supernatants of crude tissue-extracts. Through an extensive search for elution conditions, avoiding poly(L-proline) as the desorbant, we have found that active proteins can be recovered from the affinity column with a buffer containing 30% dimethyl sulphoxide. Subsequent chromatography on hydroxylapatite separates free profilin and the two isoforms of profilactin, profilin-actinβ and profilin-actinγ. The profilin-actin complexes produced this way have high specific activities in the DNAase-inhibition assay, give rise to filaments on addition of Mg2+, and can be crystallized. From the isolated profilin-actin complexes the β- and γ-actin isoforms of non-muscle cells can easily be prepared in a polymerization competent form. Pure profilin is either obtained from an excess pool present in some extracts or by dissociation of profilin-actin complexes and removal of the actin. 相似文献
3.
Variation in the ribosomal internal transcribed spacers (ITS1 and ITS2) among eight taxa of the Mimulus guttatus species complex 总被引:1,自引:0,他引:1
The internal transcribed spacer region (ITS1 and ITS2) of the 18S-25S
nuclear ribosomal DNA sequence and the intervening 5.8S region were
sequenced from three individuals in each of eight taxa of the Mimulus
guttatus species complex. Three discrete variants, or "types," of ITS
sequences were found, among which 30%-40% of sites differed, compared with
1%-2% within types. Dot plots indicate that these types were not related by
conspicuous rearrangements or inversions. More than one ITS type was often
found in the same taxon, and two of three ITS types span species
boundaries, indicating their presence prior to speciation. These ITS
sequences showed essentially no positional homology with the nearest
sequenced relative, tomato. In contrast, the 5.8S region was relatively
unvaried, with 8 of 162 sites varied in the sample among all eight taxa.
The phylogeny inferred by the most common ITS sequence type, rooted by the
two other ITS types, agreed with isozymes in showing the distinctness of M.
nudatus, M. laciniatus, and M. tilingii from the other five taxa.
相似文献
4.
Variation in heat shock proteins within tropical and desert species of poeciliid fishes 总被引:8,自引:0,他引:8
Norris CE; diIorio PJ; Schultz RJ; Hightower LE 《Molecular biology and evolution》1995,12(6):1048-1062
The 70-kilodalton heat shock protein (hsp70) family of molecular
chaperones, which contains both stress-inducible and normally abundant
constitutive members, is highly conserved across distantly related taxa.
Analysis of this protein family in individuals from an outbred population
of tropical topminnows, Poeciliopsis gracilis, showed that while
constitutive hsp70 family members showed no variation in protein isoforms,
inducibly synthesized hsp70 was polymorphic. Several species of
Poeciliopsis adapted to desert environments exhibited lower levels of
inducible hsp70 polymorphism than the tropical species, but constitutive
forms were identical to those in P. gracilis, as they were in the
confamilial species Gambusia affinis. These differences suggest that
inducible and constitutive members of this family are under different
evolutionary constraints and may indicate differences in their function
within the cell. Also, northern desert species of Poeciliopsis synthesize a
subset of the inducible hsp70 isoforms seen in tropical species. This
distribution supports the theory that ancestral tropical fish migrated
northward and colonized desert streams; the subsequent decrease in
variation of inducible hsp70 may have been due to genetic drift or a
consequence of adaptation to the desert environment. Higher levels of
variability were found when the 30- kilodalton heat shock protein (hsp30)
family was analyzed within different strains of two desert species of
Poeciliopsis and also in wild-caught individuals of Gambusia affinis. In
both cases the distribution of hsp30 isoform diversity was similar to that
seen previously with allozyme polymorphisms.
相似文献
5.
D M Bollag A P Seddon P B?hlen Y Gluzman C E Schutt 《Journal of molecular biology》1991,218(3):493-494
Human basic fibroblast growth factor (hbFGF) has been modified, with Ala3 and Ser5 substituted by glutamic acid, and the purified recombinant protein has been crystallized. The crystals are triclinic (space group P1) with unit cell parameters a = 31.0 A, b = 33.6 A, c = 34.7 A, alpha = 88 degrees, beta = 85 degrees, gamma = 76 degrees, and they diffract to at least 2 A. 相似文献
6.
A comparative structural analysis of the ADF/cofilin family 总被引:4,自引:0,他引:4
Actin-depolymerizing factor (ADF) and cofilin define a family of actin-binding proteins essential for the rapid turnover of filamentous actin in vivo. Here we present the 2.0 A crystal structure of Arabidopsis thaliana ADF1 (AtADF1), the first plant crystal structure from the ADF/cofilin (AC) family. Superposition of the four AC isoform structures permits an accurate sequence alignment that differs from previously reported data for the location of vertebrate-specific inserts and reveals a contiguous, vertebrate-specific surface opposite the putative actin-binding surface. Extending the structure-based sequence alignment to include 30 additional isoforms indicates three major groups: vertebrates, plants, and "other eukaryotes." Within these groups, several structurally conserved residues that are not conserved throughout the entire AC family have been identified. Residues that are highly conserved among all isoforms tend to cluster around the tryptophan at position 90 and a structurally conserved kink in alpha-helix 3. Analysis of surface character shows the presence of a hydrophobic patch and a highly conserved acidic cluster, both of which include several residues previously implicated in actin binding. 相似文献
7.
We have recently reported on the characterization of beta-actin carrying the mutation S14C in one of the phosphate-binding loops. The present paper describes the attachment of the adenosine 5'-[gamma-thio]-triphosphate (ATPgammaS) to actin containing this mutation. Treatment of S14C-actin with ATPgammaS blocked further nucleotide exchange and raised the thermal stability of the protein, suggesting the formation of a covalent bond between the sulfhydryl on the terminal phosphate of ATPgammaS and cysteine-14 of the mutant actin. The affinity of the derivatized G-actin for DNase I as compared to wild-type ATP-actin was lowered to a similar extent as that of ADP.AlF(4)-actin. The derivatized actin polymerized slower than ATP-actin but faster than ADP-actin. Under these conditions the bound ATPgammaS was hydrolyzed, suggesting the formation of a state corresponding to the transient ADP.P(i)-state. ATPgammaS-actin interacted normally with profilin, whereas the interaction with actin depolymerizing factor (ADF) was disturbed, as judged on the effects of these proteins on actin polymerization. 相似文献
8.
Crystal structure of the oligomerization domain of NSP4 from rotavirus reveals a core metal-binding site 总被引:6,自引:0,他引:6
Bowman GD Nodelman IM Levy O Lin SL Tian P Zamb TJ Udem SA Venkataraghavan B Schutt CE 《Journal of molecular biology》2000,304(5):861-871
During the maturation of rotaviral particles, non-structural protein 4 (NSP4) plays a critical role in the translocation of the immature capsid into the lumen of the endoplasmic reticulum. Full-length NSP4 and a 22 amino acid peptide (NSP4(114-135)) derived from this protein have been shown to induce diarrhea in young mice in an age-dependent manner, and may therefore be the agent responsible for rotavirally-induced symptoms. We have determined the crystal structure of the oligomerization domain of NSP4 which spans residues 95 to 137 (NSP4(95-137)). NSP4(95-137) self-associates into a parallel, tetrameric coiled-coil, with the hydrophobic core interrupted by three polar layers occupying a and d-heptad positions. Side-chains from two consecutive polar layers, consisting of four Gln123 and two of the four Glu120 residues, coordinate a divalent cation. Two independent structures built from MAD-phased data indicated the presence of a strontium and calcium ion bound at this site, respectively. This metal-binding site appears to play an important role in stabilizing the homo-tetramer, which has implications for the engagement of NSP4 as an enterotoxin. 相似文献
9.
Lassing I Schmitzberger F Björnstedt M Holmgren A Nordlund P Schutt CE Lindberg U 《Journal of molecular biology》2007,370(2):331-348
An essential consequence of growth factor-mediated signal transduction is the generation of intracellular H2O2. It operates as a second messenger in the control of actin microfilament dynamics, causing rapid and dramatic changes in the morphology and motile activity of stimulated cells. Little is understood about the molecular mechanisms causing these changes in the actin system. Here, it is shown that H2O2 acts directly upon several levels of this system, and some of the mechanistic effects are detailed. We describe the impact of oxidation on the polymerizability of non-muscle β/γ-actin and compare with that of muscle α-actin. Oxidation of β/γ-actin can cause a complete loss of polymerizability, crucially, reversible by the thioredoxin system. Further, oxidation of the actin impedes its interaction with profilin and causes depolymerization of filamentous actin. The effects of oxidation are critically dependent on the nucleotide state and the concentration of Ca2+. We have determined the crystal structure of oxidized β-actin to a resolution of 2.6 Å. The arrangement in the crystal implies an antiparallel homodimer connected by an intermolecular disulfide bond involving cysteine 374. Our data indicate that this dimer forms under non-polymerizing and oxidizing conditions. We identify oxidation of cysteine 272 in the crystallized actin dimer, likely to a cysteine sulfinic acid. In β/γ-actin, this is the cysteine residue most reactive towards H2O2 in solution, and we suggest plausible structural determinants for its reactivity. No other oxidative modification was obvious in the structure, highlighting the specificity of the oxidation by H2O2. Possible consequences of the observed effects in a cellular context and their potential relevance are discussed. 相似文献
10.
Jacob I. Ayers Charles R. Schutt Ronald A. Shikiya Adriano Aguzzi Anthony E. Kincaid Jason C. Bartz 《PLoS pathogens》2011,7(3)
Prion strains are characterized by differences in the outcome of disease, most notably incubation period and neuropathological features. While it is established that the disease specific isoform of the prion protein, PrPSc, is an essential component of the infectious agent, the strain-specific relationship between PrPSc properties and the biological features of the resulting disease is not clear. To investigate this relationship, we examined the amplification efficiency and conformational stability of PrPSc from eight hamster-adapted prion strains and compared it to the resulting incubation period of disease and processing of PrPSc in neurons and glia. We found that short incubation period strains were characterized by more efficient PrPSc amplification and higher PrPSc conformational stabilities compared to long incubation period strains. In the CNS, the short incubation period strains were characterized by the accumulation of N-terminally truncated PrPSc in the soma of neurons, astrocytes and microglia in contrast to long incubation period strains where PrPSc did not accumulate to detectable levels in the soma of neurons but was detected in glia similar to short incubation period strains. These results are inconsistent with the hypothesis that a decrease in conformational stability results in a corresponding increase in replication efficiency and suggest that glia mediated neurodegeneration results in longer survival times compared to direct replication of PrPSc in neurons. 相似文献