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2244 Publications

Showing 2151-2160 of 2244 results
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    06/16/09 | Self-organization of the Escherichia coli chemotaxis network imaged with super-resolution light microscopy. (With commentary)
    Greenfield D, McEvoy AL, Shroff H, Crooks GE, Wingreen NS, Betzig E, Liphardt J
    PLoS Biology. 2009 Jun 16;7(6):e1000137. doi: 10.1371/journal.pbio.1000137

    The Escherichia coli chemotaxis network is a model system for biological signal processing. In E. coli, transmembrane receptors responsible for signal transduction assemble into large clusters containing several thousand proteins. These sensory clusters have been observed at cell poles and future division sites. Despite extensive study, it remains unclear how chemotaxis clusters form, what controls cluster size and density, and how the cellular location of clusters is robustly maintained in growing and dividing cells. Here, we use photoactivated localization microscopy (PALM) to map the cellular locations of three proteins central to bacterial chemotaxis (the Tar receptor, CheY, and CheW) with a precision of 15 nm. We find that cluster sizes are approximately exponentially distributed, with no characteristic cluster size. One-third of Tar receptors are part of smaller lateral clusters and not of the large polar clusters. Analysis of the relative cellular locations of 1.1 million individual proteins (from 326 cells) suggests that clusters form via stochastic self-assembly. The super-resolution PALM maps of E. coli receptors support the notion that stochastic self-assembly can create and maintain approximately periodic structures in biological membranes, without direct cytoskeletal involvement or active transport.

    Commentary: Our goal as tool developers is to invent methods capable of uncovering new biological insights unobtainable by pre-existing technologies. A terrific example is given by this paper, where grad students Derek Greenfield and Ann McEvoy in Jan Liphardt’s group at Berkeley used our PALM to image the size and position distributions of chemotaxis proteins in E. Coli with unprecedented precision and sensitivity. Their analysis revealed that the cluster sizes follow a stretched exponential distribution, and the density of clusters is highest furthest away from the largest (e.g., polar) clusters. Both observations support a model for passive self-assembly rather than active cytoskeletal assembly of the chemotaxis network.

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    06/05/09 | Three-dimensional nanoscopy of biological samples.
    Vaziri A, Tang J, Shroff H, Shank CV
    2009 Conference on Lasers and Electro-Optics and Quantum Electronics and Laser Science Conference (CLEO/QELS 2009), Vols. 1-5. 2009 Jun 5;1-5:147-8

    We have demonstrated super-resolution imaging of protein distributions in cells at depth at multiple layers with a lateral localization precision better than 50 nm. The approach is based on combining photoactivated localization microscopy with temporal focusing.

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    06/01/09 | [Analysis on acupuncture literature in Science Citation Index (SCI) periodicals in 2007].
    Gao L, Tian L, Guo Y
    Zhongguo Zhen Jiu = Chinese Acupuncture & Moxibustion. 2009 Jun;29(6):504-7. doi: 10.1364/AO.50.001792

    To grasp the international developing tendency of acupuncture research and provide some references for promoting acupuncture and moxibustion internationalization process, the articles about acupuncture in Science Citation Index (SCI) periodicals in 2007 were retrieved by adopting the retrieval tactics on line in combination with database searching. Results indicate that 257 articles about acupuncture had been retrived from the SCI Web databases. These articles were published in 125 journals respectively, most of which were Euramerican journals. Among these journals, the impact factor of the Journal of the American Medical Association (JAMA), 25. 547, is the highest one. It is shown that the impact factors of the SCI periodicals, in which acupuncture articles embodied are increased, the quality of these articles are improved obviously and the types of the articles are various in 2007, but there is obvious difference in the results of these studies due to the difference of experimental methods, the subjects of these experiments and acupuncture manipulations. Therefore, standardization of many problems arising from the researches on acupuncture is extremely imminent.

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    06/01/09 | The ethomics era?
    Reiser M
    Nature Methods. 2009 Jun;6:413-4. doi: 10.1016/j.cub.2010.06.072

    Applying modern machine-vision techniques to the study of animal behavior, two groups developed systems that quantify many aspects of the complex social behaviors of Drosophila melanogaster. These software tools will enable high-throughput screens that seek to uncover the cellular and molecular underpinnings of behavior.

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    Eddy/Rivas Lab
    05/15/09 | Infernal 1.0: inference of RNA alignments.
    Nawrocki EP, Kolbe DL, Eddy SR
    Bioinformatics. 2009 May 15;25:1335-7. doi: 10.1093/bioinformatics/btp157

    SUMMARY: INFERNAL builds consensus RNA secondary structure profiles called covariance models (CMs), and uses them to search nucleic acid sequence databases for homologous RNAs, or to create new sequence- and structure-based multiple sequence alignments. AVAILABILITY: Source code, documentation and benchmark downloadable from INFERNAL is freely licensed under the GNU GPLv3 and should be portable to any POSIX-compliant operating system, including Linux and Mac OS/X.

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    Eddy/Rivas Lab
    05/15/09 | Local RNA structure alignment with incomplete sequence.
    Kolbe DL, Eddy SR
    Bioinformatics. 2009 May 15;25(10):1236-43. doi: 10.1093/bioinformatics/btp154

    Accuracy of automated structural RNA alignment is improved by using models that consider not only primary sequence but also secondary structure information. However, current RNA structural alignment approaches tend to perform poorly on incomplete sequence fragments, such as single reads from metagenomic environmental surveys, because nucleotides that are expected to be base paired are missing.

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    Svoboda Lab
    05/14/09 | Subcellular dynamics of type II PKA in neurons.
    Zhong H, Sia G, Sato TR, Gray NW, Mao T, Khuchua Z, Huganir RL, Svoboda K
    Neuron. 2009 May 14;62:363-74. doi: 10.1016/j.neuron.2009.03.013

    Protein kinase A (PKA) plays multiple roles in neurons. The localization and specificity of PKA are largely controlled by A-kinase anchoring proteins (AKAPs). However, the dynamics of PKA in neurons and the roles of specific AKAPs are poorly understood. We imaged the distribution of type II PKA in hippocampal and cortical layer 2/3 pyramidal neurons in vitro and in vivo. PKA was concentrated in dendritic shafts compared to the soma, axons, and dendritic spines. This spatial distribution was imposed by the microtubule-binding protein MAP2, indicating that MAP2 is the dominant AKAP in neurons. Following cAMP elevation, catalytic subunits dissociated from the MAP2-tethered regulatory subunits and rapidly became enriched in nearby spines. The spatial gradient of type II PKA between dendritic shafts and spines was critical for the regulation of synaptic strength and long-term potentiation. Therefore, the localization and activity-dependent translocation of type II PKA are important determinants of PKA function.

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    Svoboda Lab
    05/01/09 | Myosin-dependent targeting of transmembrane proteins to neuronal dendrites.
    Lewis TL, Mao T, Svoboda K, Arnold DB
    Nature Neuroscience. 2009 May;12(5):568-76. doi: 10.1038/nn.2318

    The distinct electrical properties of axonal and dendritic membranes are largely a result of specific transport of vesicle-bound membrane proteins to each compartment. How this specificity arises is unclear because kinesin motors that transport vesicles cannot autonomously distinguish dendritically projecting microtubules from those projecting axonally. We hypothesized that interaction with a second motor might enable vesicles containing dendritic proteins to preferentially associate with dendritically projecting microtubules and avoid those that project to the axon. Here we show that in rat cortical neurons, localization of several distinct transmembrane proteins to dendrites is dependent on specific myosin motors and an intact actin network. Moreover, fusion with a myosin-binding domain from Melanophilin targeted Channelrhodopsin-2 specifically to the somatodendritic compartment of neurons in mice in vivo. Together, our results suggest that dendritic transmembrane proteins direct the vesicles in which they are transported to avoid the axonal compartment through interaction with myosin motors.

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    Magee Lab
    04/16/09 | Pathway interactions and synaptic plasticity in the dendritic tuft regions of CA1 pyramidal neurons.
    Takahashi H, Magee JC
    Neuron. 2009 Apr 16;62(1):102-11. doi: 10.1016/j.neuron.2009.03.007

    Input comparison is thought to occur in many neuronal circuits, including the hippocampus, where functionally important interactions between the Schaffer collateral and perforant pathways have been hypothesized. We investigated this idea using multisite, whole-cell recordings and Ca2+ imaging and found that properly timed, repetitive stimulation of both pathways results in the generation of large plateau potentials in distal dendrites of CA1 pyramidal neurons. These dendritic plateau potentials produce widespread Ca2+ influx, large after-depolarizations, burst firing output, and long-term potentiation of perforant path synapses. Plateau duration is directly related to the strength and temporal overlap of pathway activation and involves back-propagating action potentials and both NMDA receptors and voltage-gated Ca2+ channels. Thus, the occurrence of highly correlated SC and PP input to CA1 is signaled by a dramatic change in output mode and an increase in input efficacy, all induced by a large plateau potential in the distal dendrites of CA1 pyramidal neurons.

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    Riddiford Lab
    04/01/09 | The molecular mechanisms of cuticular melanization: the ecdysone cascade leading to dopa decarboxylase expression in Manduca sexta.
    Hiruma K, Riddiford LM
    Insect Biochemistry and Molecular Biology. 2009 Apr;39(4):245-53. doi: 10.1016/j.ibmb.2009.01.008

    Many insect developmental color changes are known to be regulated by both ecdysone and juvenile hormone. Yet the molecular mechanisms underlying this regulation have not been well understood. This review highlights the hormonal mechanisms involved in the regulation of two key enzymes [dopa decarboxylase (DDC) and phenoloxidase] necessary for insect cuticular melanization, and the molecular action of 20-hydroxyecdysone on various transcription factors leading to DDC expression at the end of a larval molt in Manduca sexta. In addition, the ecdysone cascade found in M. sexta is compared with that of other organisms.

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