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101.
The relationship of complement consumption to immune fever 总被引:2,自引:0,他引:2
I D Mickenberg R Snyderman R K Root S E Mergenhagen S M Wolff 《Journal of immunology (Baltimore, Md. : 1950)》1971,107(5):1466-1476
102.
L Alonso EC Souza MV Oliveira LFE do Nascimento PMS Dantas 《Biology of sport / Institute of Sport》2014,31(4):267-270
The objective of this study was to evaluate the genetic and environmental contribution to variation in aerobic power in monozygotic (MZ) and dizygotic (DZ) twins. The sample consisted of 20 MZ individuals (12 females and 8 males) and 16 DZ individuals (12 females and 4 males), aged from 8 to 26 years, residents in Natal, Rio Grande do Norte. The twins were assessed by a multistage fitness test. The rate of heritability found for aerobic power was 77%. Based on the results, the estimated heritability was largely responsible for the differences in aerobic power. This implies that such measures are under strong genetic influence. 相似文献
103.
Kelly Champagne Akira Shishido Michael J. Root 《The Journal of biological chemistry》2009,284(6):3619-3627
Cellular entry of human immunodeficiency virus type 1 (HIV-1) involves
fusion of viral and cellular membranes and is mediated by structural
transitions in viral glycoprotein gp41. The antiviral C-peptide T20 targets
the gp41 N-terminal heptad repeat region (N-HR), blocking gp41 conformational
changes essential for the entry process. To probe the T20 structure-activity
relationship, we engineered a molecular mimic of the entire gp41 N-HR coiled
coil using the 5-Helix design strategy. T20 bound this artificial protein
(denoted 5H-ex) with nanomolar affinity (KD = 30
nm), close to its IC50 concentration (∼3
nm) but much weaker than the affinity of a related inhibitory
C-peptide C37 (KD = 0.0007 nm). T20/C37
competitive binding assays confirmed that T20 interacts with the hydrophobic
groove on the surface of the N-HR coiled coil outside of a deep pocket region
crucial for C37 binding. We used 5H-ex to investigate how the T20 N and C
termini contributed to the inhibitor binding activity. Mutating three aromatic
residues at the T20 C terminus (WNWF → ANAA) had no effect on affinity,
suggesting that these amino acids do not participate in T20 binding to the
gp41 N-HR. The results support recent evidence pointing to a different role
for these residues in T20 inhibition (Peisajovich, S. G., Gallo, S. A.,
Blumenthal, R., and Shai, Y. (2003) J. Biol. Chem. 278,
21012–21017; Liu, S., Jing, W., Cheung, B., Lu, H., Sun, J., Yan, X.,
Niu, J., Farmar, J., Wu, S., and Jiang, S. (2007) J. Biol. Chem. 282,
9612–9620). By contrast, mutations near the T20 N terminus substantially
influenced inhibitor binding strength. When Ile was substituted for Thr in the
second T20 position, a 40-fold increase in binding affinity was measured
(KD = 0.75 nm). The effect of this affinity
enhancement on T20 inhibitory potency varied among different viral strains.
The original T20 and the higher affinity T20 variant had similar potency
against wild type HIV-1. However, the higher affinity T20 variant was
significantly more potent against T20-resistant virus. The findings suggest
that other factors in addition to binding affinity play a role in limiting T20
potency. As a mimetic of the complete gp41 N-HR coiled coil region, 5H-ex will
be a useful tool to further elucidate mechanistic profiles of C-peptide
inhibitors.The HIV-12 surface
glycoprotein Env promotes viral entry through the fusion of viral and cellular
membranes (3). Env consists of
three gp120 surface subunits and three gp41 transmembrane subunits arranged as
a trimer-of-heterodimers on the virion surface. In the current model of HIV-1
entry, cellular receptor binding to gp120 initiates a series of coordinated
structural transformations that stimulate gp41 to extend and insert its
N-terminal fusion peptide into target cell membranes (see
Fig. 1A)
(4,
5). This high energy extended
intermediate structure ultimately collapses into a trimer-of-hairpins
conformation that juxtaposes the gp41 fusion peptide and transmembrane domain.
Because the fusion peptide and transmembrane domain are inserted in target
cell and viral membranes, formation of the trimer-of-hairpins is proposed to
bring these membranes into the close proximity required for efficient
fusion.Open in a separate windowFIGURE 1.HIV-1 gp41 and its role in viral membrane fusion. A, a
model of HIV-1 entry (46). In
native Env prior to receptor activation, gp41 is held in a metastable
conformation by a canopy of gp120 proteins (green). Receptor binding
to gp120 stimulates gp41 to extend and insert its fusion peptide segment
(red) into the target cell membrane. The N-HR (gray) and
C-HR (blue) regions of the gp41 ectodomain are transiently exposed in
this prehairpin state. Subsequently, gp41 collapses into the
trimer-of-hairpins conformation that brings the gp41 fusion peptides,
transmembrane regions (purple), and their associated membranes into
the close proximity for membrane fusion. The actual disposition of gp120 in
both the prehairpin and trimer-of-hairpins states is uncertain; for clarity,
the protein is omitted in the schematic of the trimer-of-hairpins
conformation. B, a diagram of HIV-1 gp41 identifying its fusion
peptide (FP), N-HR, C-HR, MPER (MP), transmembrane
(TM), and cytoplasmic (cyto) domains. Amino acid sequences
above and below the diagram are derived from the N-HR and C-HR/MPER regions of
EnvHXB2; all but the MPER sequence WNWF (magenta) were
used in the design of 5H-ex. The N-HR and C-HR segments found in the original
5-Helix are boxed in gray and blue, respectively, whereas
the sequences of C37 and T20 are denoted by lines. The side chains of
the C-HR amino acids marked with + pack into the hydrophobic pocket at the C
terminus of the N-HR coiled coil.The core of the trimer-of-hairpins is a bundle of six α-helices
formed by two hydrophobic heptad repeat sequences in the N- and C-terminal
regions of the gp41 ectodomain (N-HR and C-HR, respectively)
(6,
7). In the trimer-of-hairpins,
the N-HR segments from three gp41 ectodomains form a central trimeric coiled
coil, around which the three C-HR segments pack as antiparallel helices into
hydrophobic grooves
(8–11).
In the prehairpin extended conformation, the N-HR and C-HR segments are
unassociated and transiently accessible to inhibitors of HIV-1 entry
(5,
12). Several such inhibitors
are formed from the peptide sequence of the C-HR and adjacent gp41 regions
(4,
6,
13,
14). Denoted C-peptides, they
work in a dominant negative fashion by binding to the exposed N-HR coiled
coil, thereby blocking trimer-of-hairpins formation and inhibiting viral
membrane fusion (4,
15–21).
One C-peptide, T20 (also called enfuvirtide), has shown antiviral activity
in vivo and has been approved for use in the treatment of HIV-1
infection (22,
23).T20 is a 36-amino acid peptide extending from Tyr638 in the
middle of the C-HR to Phe673 in the Trp-rich membrane proximal
external region (MPER) that precedes the gp41 transmembrane domain (residue
numbering is according to the EnvHXB2 sequence; see
Fig. 1B)
(13). In T20, these C-terminal
MPER-derived residues are critical for inhibitory activity, although their
structure and function in the gp41-bound state are currently unknown
(1,
24,
25). A second class of
similarly potent C-peptides includes C34 (residues 628–661) and the
slightly larger C37 (residues 625–661)
(4,
6,
26,
27). These peptides are
derived entirely from the C-HR sequence and thus are shifted in the N-terminal
direction compared with T20 (Fig.
1B). The interactions of C34 and C37 with gp41 are
greatly stabilized by residues Trp628, Trp631, and
Ile635 near the C-HR N terminus
(4). Their bulky hydrophobic
side chains pack into a deep hydrophobic pocket on the surface of the N-HR
coiled coil. T20 lacks these pocket binding residues and their stabilizing
effect. However, T20 does contain bulky hydrophobic residues
(Trp670, Trp672, and Phe673) at its C
terminus that might pack into a similar pocket at the other end of the N-HR
coiled coil.High resolution structures of the gp41 trimer-of-hairpins have aided our
understanding of the mechanism of C-peptide inhibition. These structures have
enabled the design of polypeptides that mimic the gp41 N-HR coiled coil and
bind C34/C37, thereby providing a tool to probe the structure-activity
relationships of the inhibitors
(26,
28–30).
No similar tool is available for investigating T20 inhibition in detail. The
structures of the gp41 trimer-of-hairpins do not include the T20 C terminus (9
residues) nor the gp41 N-terminal segments that putatively interact with it.
Furthermore, gp41 N-HR-derived peptides predicted to interact with T20 are
poorly soluble and difficult to use in solution phase interaction assays
(6). Here we describe the
design of a soluble protein (denoted 5H-ex) that mimics the putative
T20-binding site on the N-HR coiled coil. 5H-ex interacts with T20 with an
equilibrium dissociation constant (KD) of 30
nm, close to the T20 50% inhibitory concentration (IC50)
of 3 nm. Using this protein, we explored the extent to which the N
and C termini of T20 contribute to its binding activity. First, we showed that
the MPER-derived residues at the peptide C terminus do not stabilize the
5H-ex/T20 interaction. Second, we identified an N-terminal substitution that
significantly enhanced T20 binding affinity and improved peptide inhibitory
activity against T20-resistant HIV-1. The results suggest that T20 binding to
the N-HR coiled coil is stabilized primarily by residues derived from the C-HR
and not the MPER. 5H-ex is likely to be a useful tool in probing the
structure-activity relationship of T20. 相似文献
104.
A lentiviral RNAi library for human and mouse genes applied to an arrayed viral high-content screen 总被引:22,自引:0,他引:22
Moffat J Grueneberg DA Yang X Kim SY Kloepfer AM Hinkle G Piqani B Eisenhaure TM Luo B Grenier JK Carpenter AE Foo SY Stewart SA Stockwell BR Hacohen N Hahn WC Lander ES Sabatini DM Root DE 《Cell》2006,124(6):1283-1298
To enable arrayed or pooled loss-of-function screens in a wide range of mammalian cell types, including primary and nondividing cells, we are developing lentiviral short hairpin RNA (shRNA) libraries targeting the human and murine genomes. The libraries currently contain 104,000 vectors, targeting each of 22,000 human and mouse genes with multiple sequence-verified constructs. To test the utility of the library for arrayed screens, we developed a screen based on high-content imaging to identify genes required for mitotic progression in human cancer cells and applied it to an arrayed set of 5,000 unique shRNA-expressing lentiviruses that target 1,028 human genes. The screen identified several known and approximately 100 candidate regulators of mitotic progression and proliferation; the availability of multiple shRNAs targeting the same gene facilitated functional validation of putative hits. This work provides a widely applicable resource for loss-of-function screens, as well as a roadmap for its application to biological discovery. 相似文献
105.
Echeverri CJ Beachy PA Baum B Boutros M Buchholz F Chanda SK Downward J Ellenberg J Fraser AG Hacohen N Hahn WC Jackson AL Kiger A Linsley PS Lum L Ma Y Mathey-Prévôt B Root DE Sabatini DM Taipale J Perrimon N Bernards R 《Nature methods》2006,3(10):777-779
Large-scale RNA interference (RNAi)-based analyses, very much as other 'omic' approaches, have inherent rates of false positives and negatives. The variability in the standards of care applied to validate results from these studies, if left unchecked, could eventually begin to undermine the credibility of RNAi as a powerful functional approach. This Commentary is an invitation to an open discussion started among various users of RNAi to set forth accepted standards that would insure the quality and accuracy of information in the large datasets coming out of genome-scale screens. 相似文献
106.
Pumroy RA Nardozzi JD Hart DJ Root MJ Cingolani G 《The Journal of biological chemistry》2012,287(3):2022-2031
The human genome encodes six isoforms of importin α that show greater than 60% sequence similarity and remarkable substrate specificity. The isoform importin α5 can bind phosphorylated cargos such as STAT1 and Epstein-Barr Virus Nuclear Antigen 1, as well as the influenza virus polymerase subunit PB2. In this work, we have studied the interaction of the nucleoporin Nup50 with importin α5. We show that the first 47 residues of Nup50 bind to the C terminus of importin α5 like a "clip," stabilizing the closed conformation of ARM 10. In vitro, Nup50 binds with high affinity either to empty importin α5 or to a preassembled complex of importin α5 bound to the C-terminal domain of the import cargo PB2, resulting in a trimeric complex. By contrast, PB2 can only bind with high affinity to importin α5 in the absence of Nup50. This suggests that Nup50 primary function may not be to actively displace the import cargo from importin α5 but rather to prevent cargo rebinding in preparation for recycling. This is the first evidence for a nucleoporin modulating the import reaction by directly altering the three-dimensional structure of an import adaptor. 相似文献
107.
Hannah M. Schapiro Mukta D. Khasnis Koree Ahn Alexandra Karagiaridi Stephanie Hayden Maria E. Cilento Michael J. Root 《PLoS pathogens》2022,18(5)
Glycoprotein Env of human immunodeficiency virus type 1 (HIV-1) mediates viral entry through membrane fusion. Composed of gp120 and gp41 subunits arranged as a trimer-of-heterodimers, Env adopts a metastable, highly dynamic conformation on the virion surface. This structural plasticity limits the temporospatial exposure of many highly conserved, neutralizing epitopes, contributing to the difficulty in developing effective HIV-1 vaccines. Here, we employed antibody neutralization of HIV-1 infectivity to investigate how inter- and intra-gp120 interactions mediated by variable loops V1/V2 and V3 at the Env apex regulate accessibility of the gp41 membrane-proximal external region (MPER) at the Env base. Swapping the V3 loop from EnvSF162 into the EnvHXB2 background shifted MPER exposure from the prefusogenic state to a functional intermediate conformation that was distinct from the prehairpin-intermediate state sensitive to gp41-targeted fusion inhibitors. The V3-loop swap had a profound impact on global protein dynamics, biasing the equilibrium to a closed conformation resistant to most anti-gp120 antibodies, stabilizing the protein to both cold- and soluble CD4-induced Env inactivation, and increasing the CD4 requirements for viral entry. Further dissection of the EnvHXB2 V3 loop revealed that residue 306 uniquely modulated epitope exposure and trimer stability. The R306S substitution substantially decreased sensitivity to antibodies targeting the gp41 MPER and, surprisingly, the gp120 V3-loop crown (residues 312–315), but had only modest effects on exposure of intervening gp120 epitopes. Furthermore, the point mutation reduced soluble CD4-induced inactivation, but had no impact on cold inactivation. The residue appeared to exert its effects by electrostatically modifying the strength of intra-subunit interactions between the V1/V2 and V3 loops. The distinct patterns of neutralization and stability pointed to a novel prefusogenic Env conformation along the receptor activation pathway and suggested that apical Env-regulation of gp41 MPER exposure can be decoupled from much of the dynamics of gp120 subunits. 相似文献
108.
Nandakumar KV Karthickeyan Duraisamy Shibu Balakrishnan Sunilkumar M Jaya Sankar S Karuna D. Sagili Srinath Satyanarayana Ajay Kumar MV Donald A. Enarson 《PloS one》2013,8(10)
Settings
Kerala State, India has reported the greatest dual burden of Tuberculosis (TB) and Diabetes Mellitus (DM). Malappuram district in Kerala has monitored and recorded DM status and its control from 2010 under Revised National Tuberculosis Control Program (RNTCP).Objectives
To assess, under programme conditions, comprehensiveness of recording DM status among TB cases and the TB treatment outcomes among DM patients (disaggregated by glycemic control) and compare with-non DM patients.Design
This retrospective record review included 3,116TB patients from April 2010 to September 2011.DM was defined as per international guidelines and TB treatment outcomes were categorized as favourable(cured and treatment completed) and unfavourable(death, default, failure and transfer out). Relative Risk (RR) and 95% confidence intervals(CI) were calculated to assess the risk of unfavourable outcomes.Results
DM status was recorded in 90% of TB cases and 667 (24%) had DM. 17% of DM patients and 23% of patients with unknown DM status had unfavourable outcomes but this difference was not statistically significant. Unadjusted RR for poor glycemic control or unknown control status for unfavourable outcome were (2.00; 95% CI 0.97–4.13) and (2.14; 95% CI 1.11–4.13).Conclusion
This study could not confirm an adverse association between DM or its control during treatment and the course of response to TB treatment.DM screening in TB cases and recording of DM care needs to be improved to enable more conclusive evidence. 相似文献109.
McLeod J O'Callaghan PM Pybus LP Wilkinson SJ Root T Racher AJ James DC 《Biotechnology and bioengineering》2011,108(9):2193-2204