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1.
The complete amino acid sequence of the 121 amino acid residues of piratoxin II, a phospholipase A(2) like myotoxin from Bothrops pirajai venom, is reported. PrTX-II is a basic protein with a molecular mass of 13740 Da, a calculated pI of 9.03, but an experimental pI of 8.4 +/- 0.2, showing sequence similarity with other bothropic (90-99%) or non-bothropic ( approximately 80%) Lys49 PLA(2)-like myotoxins. This similarity falls to approximately 70% when this sequence is aligned with that of Asp49 PLA(2). Due to the substitution of Asp49 by Lys49 and alterations in the calcium binding loop structure, as the replacement of Gly32 by Leu32, piratoxin-II shows no PLA(2) activity when assayed on egg yolk. Piratoxin-II showed the same primary structure as piratoxin-I, except that it has Lys116 for Leu116. Despite this slightly higher basicity at the C-terminal region, piratoxin-II was shown to be less myotoxic than piratoxin-I. The change Leu --> Lys induced an alteration of the molecule surface shape and probably of the environment charge high enough to slightly decrease the myotoxic activity. When aligned with B. jararacussu bothropstoxin-I and with B. asper Basp-II, piratoxin-II revealed a single (position 132) and a quintuple (positions 17, 90, 111, 120 and 132) amino acid substitution, respectively, suggesting a common evolutionary origin for these three myotoxins. 相似文献
2.
Braden BC Velikovsky CA Cauerhff AA Polikarpov I Goldbaum FA 《Journal of molecular biology》2000,297(5):1031-1036
We have determined the three-dimensional structure of 6, 7-dimethyl-8-ribityllumazine synthase (lumazine synthase) from Brucella abortus, the infectious organism of the disease brucellosis in animals. This enzyme catalyses the formation of 6, 7-dimethyl-8-ribityllumazine, the penultimate product in the synthesis of riboflavin. The three-dimensional X-ray crystal structure of the enzyme from B. abortus has been solved and refined at 2.7 A resolution to a final R-value of 0.18 (R(free)=0.23). The macromolecular assembly of the enzyme differs from that of the enzyme from Bacillus subtilis, the only other lumazine synthase structure known. While the protein from B. subtilis assembles into a 60 subunit icosahedral capsid built from 12 pentameric units, the enzyme from B. abortus is pentameric in its crystalline form. Nonetheless, the active sites of the two enzymes are virtually identical indicating inhibitors to theses enzymes could be effective pharmaceuticals across a broad species range. Furthermore, we compare the structures of the enzyme from B. subtilis and B. abortus and describe the C teminus structure which accounts for the differences in quaternary structure. 相似文献
3.
Transcatheter treatment was performed in 81 patients with unresectable non-colorectal liver metastases. Effectiveness increased in the following order: hepatic artery infusion--arterial chemoembolization--combined, arterial and portal vein oily chemoembolization. The mean survival rates for these methods were 8.2 +/- 5.3, vs 11.7 +/- 12.9 vs 13.6 +/- 6.8 mo, and 1-year survival rates 29% vs 46% vs 65%, respectively. Chemoembolization with doxorubicin-in-oil and gelatin sponge was the most effective technique. Interventional radiological procedures were effective in neuroendocrine liver metastases. The mean survival, 1- and 3-year survival rates were as high as 34 mo, 100% and 80%, respectively, for hepatic metastases from resected malignant carcinoid tumors. Also good results were achieved after chemoembolization of metastatic ovarian carcinoma and arterial infusion for gastric carcinoma metastatic to the liver. Transcatheter treatment was ineffective in liver metastases from pancreatic carcinoma, gallbladder cancer, and unknown (and non-resected) tumors. The initial results of the use of interventional radiological procedures in non-colorectal liver metastases are promising, so following clinical trails are needed. 相似文献
4.
The crystallographic structure of a novel trypsin inhibitor (CTI) from Copaifera langsdorffii is reported. The structure was solved by MIRAS procedure and refined to a crystallographic residual of 17.3% (R(free) = 20.3%) at 1.8 A resolution. Two isomorphous derivatives were obtained by quick cryo-soaking approach. CTI is the first structure of a member of Kunitz (STI) family formed by two noncovalently bound polypeptide chains and only one disulfide bridge. A standard Kunitz-type inhibitor has a single polypeptide chain and two disulfide bridges. Structural features granting CTI high inhibitory activity are discussed. 相似文献
5.
Average protein density is a molecular-weight-dependent function 总被引:3,自引:0,他引:3
Fischer H Polikarpov I Craievich AF 《Protein science : a publication of the Protein Society》2004,13(10):2825-2828
The mass density of proteins is a relevant basic biophysical quantity. It is also a useful input parameter, for example, for three-dimensional structure determination by protein crystallography and studies of protein oligomers in solution by analytic ultracentrifugation. We have performed a critical analysis of published, theoretical, and experimental investigations about this issue and concluded that the average density of proteins is not a constant as often assumed. For proteins with a molecular weight below 20 kDa, the average density exhibits a positive deviation that increases for decreasing molecular weight. A simple molecular-weight-depending function is proposed that provides a more accurate estimate of the average protein density. 相似文献
6.
7.
Krauchenco S Pando SC Marangoni S Polikarpov I 《Biochemical and biophysical research communications》2003,312(4):1303-1308
The three-dimensional structure of a novel Kunitz (STI) family member, an inhibitor purified from Delonix regia seeds (DrTI), was solved by molecular replacement method and refined, respectively, to R(factor) and R(free) values of 21.5% and 25.3% at 1.75A resolution. The structure has a classical beta-trefoil fold, however, differently from canonical Kunitz type (STI) inhibitors, its reactive site loop has an insertion of one residue, Glu68, between the residues P1 and P2. Surprisingly, DrTI is an effective inhibitor of trypsin and human plasma kallikrein, but not of chymotrypsin and tissue kallikrein. Putative structural grounds of such specificity are discussed. 相似文献
8.
9.
Fernanda A. H. Batista Leandro S. Goto Wanius Garcia Derminda I. de Moraes Mario de Oliveira Neto Igor Polikarpov Marcia R. Cominetti Heloísa S. Selistre-de-Araújo Leila M. Beltramini Ana Paula Ulian Araújo 《European biophysics journal : EBJ》2010,39(8):1193-1205
Lectins have been classified into a structurally diverse group of proteins that bind carbohydrates and glycoconjugates with
high specificity. They are extremely useful molecules in the characterization of saccharides, as drug delivery mediators,
and even as cellular surface makers. In this study, we present camptosemin, a new lectin from Camptosema ellipticum. It was characterized as an N-acetyl-d-galactosamine-binding homo-tetrameric lectin, with a molecular weight around 26 kDa/monomers. The monomers were stable over
a wide range of pH values and exhibited pH-dependent oligomerization. Camptosemin promoted adhesion of breast cancer cells
and hemagglutination, and both activities were inhibited by its binding of sugar. The stability and unfolding/folding behavior
of this lectin was characterized using fluorescence and far-UV circular dichroism spectroscopies. The results indicate that
chemical unfolding of camptosemin proceeds as a two-state monomer-tetramer process. In addition, small-angle X-ray scattering
shows that camptosemin behaves as a soluble and stable homo-tetramer molecule in solution. 相似文献
10.
Figueira AC Neto Mde O Bernardes A Dias SM Craievich AF Baxter JD Webb P Polikarpov I 《Biochemistry》2007,46(5):1273-1283
High-resolution X-ray structures of thyroid hormone (TH) receptor (TR) DNA and ligand binding domains (DBD and LBD) have yielded significant insights into TR action. Nevertheless, the TR DBD and LBD act in concert to mediate TH effects upon gene expression, and TRs form multiple oligomers; however, structures of full-length TRs or DBD-LBD constructs that would clarify these influences are not available. Here, we report low-resolution X-ray structures of the TRbeta DBD-LBD construct in solution which define the shape of dimers and tetramers and likely positions of the DBDs and LBDs. The holo TRbeta DBD-LBD construct forms a homodimer with LBD-DBD pairs in close contact and DBDs protruding from the base in the same direction. The DBDs are connected to the LBDs by crossed extended D domains. The apo hTRbeta DBD-LBD construct forms tetramers that resemble bulged cylinders with pairs of LBD dimers in a head-to-head arrangement with DBD pairs packed tightly against the LBD core. Overall, there are similarities with our previous low-resolution structures of retinoid X receptors, but TRs exhibit two unique features. First, TR DBDs are closely juxtaposed in the dimer and tetramer forms. Second, TR DBDs are closely packed against LBDs in the tetramer, but not the dimer. These findings suggest that TRs may be able to engage in hitherto unknown interdomain interactions and that the D domain must rearrange in different oligomeric forms. Finally, the data corroborate our suggestion that apo TRs form tetramers in solution which dissociate into dimers upon hormone binding. 相似文献