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81.
Irene Mangialavori Ana Mar��a Villamil Giraldo Cristina Marino Buslje Mariela Ferreira Gomes Ariel J. Caride Juan Pablo F. C. Rossi 《The Journal of biological chemistry》2009,284(8):4823-4828
The purpose of this work was to obtain structural information about
conformational changes in the membrane region of the sarcoplasmic reticulum
(SERCA) and plasma membrane (PMCA) Ca2+ pumps. We have assessed
changes in the overall exposure of these proteins to surrounding lipids by
quantifying the extent of protein labeling by a photoactivatable
phosphatidylcholine analog
1-palmitoyl-2-[9-[2′-[125I]iodo-4′-(trifluoromethyldiazirinyl)-benzyloxycarbonyl]-nonaoyl]-sn-glycero-3-phosphocholine
([125I]TID-PC/16) under different conditions. We determined the
following. 1) Incorporation of [125I]TID-PC/16 to SERCA decreases
25% when labeling is performed in the presence of Ca2+. This
decrease in labeling matches qualitatively the decrease in transmembrane
surface exposed to the solvent calculated from crystallographic data for SERCA
structures. 2) Labeling of PMCA incubated with Ca2+ and calmodulin
decreases by approximately the same amount. However, incubation with
Ca2+ alone increases labeling by more than 50%. Addition of C28, a
peptide that prevents activation of PMCA by calmodulin, yields similar
results. C28 has also been shown to inhibit ATPase SERCA activity.
Interestingly, incubation of SERCA with C28 also increases
[125I]TID-PC/16 incorporation to the protein. These results suggest
that in both proteins there are two different E1
conformations as follows: one that is auto-inhibited and is in contact with a
higher amount of lipids (Ca2+ + C28 for SERCA and Ca2+
alone for PMCA), and one in which the enzyme is fully active (Ca2+
for SERCA and Ca2+-calmodulin for PMCA) and that exhibits a more
compact transmembrane arrangement. These results are the first evidence that
there is an autoinhibited conformation in these P-type ATPases, which involves
both the cytoplasmic regions and the transmembrane segments.Although membrane proteins constitute more than 20% of the total proteins,
the structure of only few of them is known in detail. An important group of
integral membrane proteins are ion-motive ATPases. These proteins belong to
the family of P-type ATPases, which share in common the formation of an
acid-stable phosphorylated intermediate as part of its reaction cycle.
Crystallographic information is available for a few members of this family.
There are several crystal structures of the Ca2+ pump of
sarcoplasmic reticulum
(SERCA)2 revealing
different conformations
(1–5),
and recently, crystal structures of the H+-ATPase
(6) and of the Na,K-ATPase were
reported as well (7).We are interested in obtaining structural information about the plasma
membrane calcium pump (PMCA). This pump is an integral part of the
Ca2+ signaling mechanism
(8). It is highly regulated by
calmodulin, which activates this protein by binding to an auto-inhibitory
region and changing the conformation of the pump from an inhibited state to an
activated one (8,
9). Crystallization of PMCA is
particularly challenging because there is no natural source from which this
protein can be obtained in large quantities. Moreover, the presence of several
isoforms in the same tissue further complicates efforts to obtain a
homogeneous sample suitable for crystallization.Information about the structure and assembly of the transmembrane domain of
an integral membrane protein can also be obtained from the analysis of the
lipid-protein interactions. In this work, we have used a hydrophobic
photolabeling method to study the noncovalent interactions between PMCA and
the surrounding phospholipids under different experimental conditions that
lead to known conformations. We employed the photoactivatable
phosphatidylcholine analog
1-palmitoyl-2-[9-[2′-[125I]iodo-4′-(trifluoromethyldiazirinyl)-benzyloxycarbonyl]-nonaoyl]-sn-glycero-3-phosphocholine
([125I]TID-PC/16) that has been previously used to analyze
lipid-protein interfaces
(10–12).
This reagent is located in the phospholipidic milieu, and upon photolysis it
reacts indiscriminately with its molecular neighbors. It is thus possible to
directly analyze the interaction between a membrane protein and lipids
belonging to its immediate environment
(13–15).
By measuring the amount of labeling of SERCA in conditions that promote
conformations for which there are well resolved crystal structures, we were
able to validate this photolabeling approach as a convenient tool for
analyzing conformational changes within transmembrane regions. Furthermore,
using this technique on PMCA and comparing the results obtained for SERCA, we
were able to draw structural conclusions about these proteins under activated
and inhibited states. 相似文献
82.
Jasen L. Wise Richard J. Crout Daniel W. McNeil Robert J. Weyant Mary L. Marazita Sharon L. Wenger 《PloS one》2009,4(6)
Five percent of patients with unexplained mental retardation have been attributed to cryptic unbalanced subtelomeric rearrangements. Half of these affected individuals have inherited the rearrangement from a parent who is a carrier for a balanced translocation. However, the frequency of carriers for cryptic balanced translocations is unknown. To determine this frequency, 565 phenotypically normal unrelated individuals were examined for balanced subtelomeric rearrangements using Fluorescent In Situ hybridization (FISH) probes for all subtelomere regions. While no balanced subtelomeric rearrangements were identified, three females in this study were determined to be mosaic for the X chromosome. Mosaicism for XXX cell lines were observed in the lymphocyte cultures of 3 in 379 women (0.8%), which is a higher frequency than the 1 in 1000 (0.1%) reported for sex chromosome aneuploidies. Our findings suggest that numerical abnormalities of the X chromosome are more common in females than previously reported. Based on a review of the literature, the incidence of cryptic translocation carriers is estimated to be approximately 1/8,000, more than ten-fold higher than the frequency of visible reciprocal translocations. 相似文献
83.
Marcela Beatriz Roigé Sandra Mariela Aranguren María Belén Riccio Silvia Pereyra Alejandro Luis Soraci María Ofelia Tapia 《Revista iberoamericana de micología》2009,26(4):233-237
Wheat (as bran) and corn (as dry grain or fermented feed) are main ingredients of feedstuffs used in local cattle and pig farms in the South of the Buenos Aires Province (Argentina). Therefore, determining mycobiota and mycotoxins in wheat and corn is of prime importance for developing feed management techniques to optimise animal production and to minimize toxicity. Then, a mycological survey was carried out in the Southeastern part of the Buenos Aires Province, in order to identify the mycobiota and the main mycotoxins present in fermented feed, wheat grain and corn grain samples. Samples were cultured for fungal quantification, isolation and identification, and analysed for deoxynivalenol (DON), zearalenone (ZEA), T-2 toxin and aflatoxins (AFLA). Penicillium (74%), Aspergillus (32%) and Scopulariopsis (21%) were the prevalent genera in fermented feed. Penicillium (70%), Fusarium (47%) and Aspergillus (34%) were the most frequent fungi isolated from corn. Penicillium (42%), Fusarium (27%) and Alternaria (25%) were the most frequently recovered genera from wheat. DON was detected in 59% of the corn samples, in 45% of the wheat samples and in 38% of the silage samples. ZEA was detected in 36% of the corn samples, in 49% of the wheat samples and in 16% of the silage samples. T-2 toxin and aflatoxin B1 were each detected in 4% of the corn samples. Eighteen percent of the fermented feed samples showed T-2 contamination. Fermented feed and wheat samples were negative for AFLA. 相似文献
84.
Susana R. Morcelle Constanza S. Liggieri Mariela A. Bruno Nora Priolo Pere Claps 《Journal of Molecular Catalysis .B, Enzymatic》2009,57(1-4):177-182
Partially purified preparations with proteolytic activity, obtained from South American native plants, were used as biocatalysts in condensation reactions of N-protected arginine alkyl ester derivatives with decylamine and dodecylamine in low-water content systems. The final products are cationic surfactants with potential application as emulsifiers and preservatives. Most of the proteolytic extracts were obtained from latex of species belonging to the Asclepiadaceae family (araujiain from Araujia hortorum, asclepain c from Asclepias curassavica and funastrain from Funastrum clausum). Hieronymain was obtained from unripe fruits of Bromelia hieronymi (Bromeliaceae). Plant proteases from commercial sources (papain and bromelain) were also tested as catalysts in the same reactions. Araujiain and funastrain furnished good reaction conversions (60–84%, with a ratio synthesis/hydrolysis of 2–5) similar to those obtained with commercial papain. Moreover, araujiain was the biocatalyst which rendered the best conversions (60%) for the synthesis of the two novel Bz-Arg-NH-dodecylamide (Bz-Arg-NHC12) and Bz-Arg-NH-decylamide (Bz-Arg-NHC10) derivatives. Moderate to poor conversions (10–50%, showing a ratio synthesis/hydrolysis of 0.5–1) were achieved with asclepain c, hieronymain and bromelain. The screening presented in this work revealed that, although these are structurally similar, their behavior for the synthesis of this kind of products differ among them. 相似文献
85.
Noelia L. Grosso Jacqueline Bua Alina E. Perrone Mariela N. Gonzalez 《Experimental parasitology》2010,126(2):239-244
We describe some biological and molecular characteristics of a Trypanosoma cruzi isolate derived from a Triatomine captured in Nicaragua. PCR based typification showed that this isolate, named Nicaragua, belonged to the lineage Tc I. Nicaragua infected culture cells were treated with allopurinol, showing different behavior according to the cellular compartment, being cardiomyocyte primary cultures more resistant to this drug. The course of the infection in a mice experimental model and its susceptibility to benznidazole and allopurinol was analyzed. In benznidazole treatment, mice reverted the high lethal effect of parasites during the acute infection, however, a few parasites were detected in the heart of 88% of mice 1 year post-infection. Since T. cruzi is a heterogeneous species population it is important to study and characterize different parasites actually circulating in humans in endemic areas. In this work we show that T. cruzi Nicaragua isolate, is sensitive to early benznidazole treatment. 相似文献
86.
The Intra-Hippocampal Leucine Administration Impairs Memory Consolidation and LTP Generation in Rats
Viviane Glaser Valeria P. Carlini Laura Gabach Marisa Ghersi Susana Rubiales de Barioglio Oscar A. Ramirez Mariela F. Perez Alexandra Latini 《Cellular and molecular neurobiology》2010,30(7):1067-1075
Leucine accumulates in fluids and tissues of patients affected by maple syrup urine disease, an inherited metabolic disorder,
predominantly characterized by neurological dysfunction. Although, a variable degree of cognition/psychomotor delay/mental
retardation is found in a considerable number of individuals affected by this deficieny, the mechanisms underlying the neuropathology
of these alterations are still not defined. Therefore, the aim of this study was to investigate the effect of acute intra-hippocampal
leucine administration in the step-down test in rats. In addition, the leucine effects on the electrophysiological parameter,
long-term potentiation generation, and on the activities of the respiratory chain were also investigated. Male Wistar rats
were bilaterally administrated with leucine (80 nmol/hippocampus; 160 nmol/rat) or artificial cerebrospinal fluid (controls)
into the hippocampus immediately post-training in the behavioral task. Twenty-four hours after training in the step-down test,
the latency time was evaluated and afterwards animals were sacrificed for assessing the ex vivo biochemical measurements.
Leucine-treated animals showed impairment in memory consolidation and a complete inhibition of long-term potentiation generation
at supramaximal stimulation. In addition, a significant increment in complex IV activity was observed in hippocampus from
leucine-administered rats. These data strongly indicate that leucine compromise memory consolidation, and that impairment
of long-term potentiation generation and unbalance of the respiratory chain may be plausible mechanisms underlying the deleterious
leucine effect on cognition. 相似文献
87.
Mauricio Cabrera María Laura Lavaggi Fiorela Croce Laura Celano Leonor Thomson Marcelo Fernández Cristina Pintos Stella Raymondo Mariela Bollati Antonio Monge Adela López de Ceráin Oscar E. Piro Hugo Cerecetto Mercedes González 《Bioorganic & medicinal chemistry》2010,18(14):5391-5399
Cancer preventive agents (CPA) are drugs able to suppress the carcinogen metabolic activation or block the formation of ultimate carcinogens. CPA could act through various molecular mechanisms, for example by interfering with the action of procarcinogen. This could be attained by increasing the phase II enzymes levels of quinone reductase (QR) and glutathione S-transferase (GST). New flavonoids, especially chalcones, have been identified as in vivo monofunctional phase II enzymes inducers. Oral administration of chalcone, 4, and both p-methoxy-substituted chalcones, 6 and 14, increased hepatic QR activity with concomitant decrease in CYP1A1 activity, a member of the most important group of phase I enzymes cytochrome P450. Among them, 4 also increased GST activity. While p-bromo-substituted chalcone 8 was the best inducer of QR it decreased hepatic GST expression and cytochrome P450, being the most effective decreasing cytochrome P450-expression. Thienyl-chalcone 20 being the bioisostere of chalcone 4 did not display the same in vivo profile in the phase I level modification. As chalcone 4 its bioisostere, chalcone 20, displayed low DNA strand breakage and absence of mutagenicity. Also, in our preliminary in vivo tumourigenesis/chemopreventive and acute-toxicity studies, chalcones 4, 6 and 8 showed the best behaviours as CPA justifying additional studies that are ongoing. 相似文献
88.
Michal Letek Patricia González Iain MacArthur Héctor Rodríguez Tom C. Freeman Ana Valero-Rello Mónica Blanco Tom Buckley Inna Cherevach Ruth Fahey Alexia Hapeshi Jolyon Holdstock Desmond Leadon Jesús Navas Alain Ocampo Michael A. Quail Mandy Sanders Mariela M. Scortti John F. Prescott Ursula Fogarty Wim G. Meijer Julian Parkhill Stephen D. Bentley José A. Vázquez-Boland 《PLoS genetics》2010,6(9)
89.
Scortti M Lacharme-Lora L Wagner M Chico-Calero I Losito P Vázquez-Boland JA 《Nature medicine》2006,12(5):515-517
Discrepancies between resistance in vitro and therapeutic efficacy in vivo are generally attributed to failure of laboratory susceptibility tests to reflect an antibiotic's pharmacokinetic or pharmacodynamic properties. We show here that this phenomenon can result from differential in vitro-in vivo expression of bacterial determinants of antibiotic susceptibility. We found that an in vivo-induced virulence factor, Hpt, also mediates uptake of fosfomycin in Listeria monocytogenes. These bacteria therefore seem resistant to fosfomycin in vitro, although they are in fact susceptible to the antibiotic during infection. 相似文献
90.
OBJECTIVE: To determine whether postprandial lipids, coagulation factors and homocysteine levels are abnormal in young growth hormone (GH)-deficient (GHD) adolescents. METHODS: Fifteen GHD adolescents on GH replacement were studied. Ten untreated GHD adolescents and 15 healthy subjects served as controls. Fasting lipids, lipoprotein(a), fibrinogen, plasminogen activator inhibitor-1, homocysteine, folate and vitamin B12 levels were measured. Cholesterol and triglycerides were measured 4 h after a high fat meal. RESULTS: Fasting and postprandial triglycerides and homocysteine levels of untreated GHD patients were increased compared to those of GH-treated GHD subjects and healthy controls; fibrinogen concentrations were elevated in both treated and untreated adolescents. CONCLUSIONS: GHD adolescents present an abnormal fasting and postprandial lipid profile. In addition, the increased fibrinogen and homocysteine levels are suggestive of the accumulation of cardiovascular risk factors early on in life. 相似文献