Noncooperative stabilization effect of phalloidin on ADP.BeFx- and ADP.AlF4-actin filaments

Actin plays important roles in eukaryotic cell motility. During actin polymerization, the actin-bound ATP is hydrolyzed to ADP and P i. We carried out differential scanning calorimetry experiments to characterize the cooperativity of the stabilizing effect of phalloidin on actin filaments in their ADP.P i state. The ADP.P i state was mimicked by using ADP.BeF x or ADP.AlF 4. The results showed that the binding of the nucleotide analogues or phalloidin stabilized the actin filaments to a similar extent when added separately. Phalloidin binding to ADP.BeF x- or ADP.AlF 4-actin filaments further stabilized them, indicating that the mechanism by which phalloidin and the nucleotide analogues affect the filament structure was different. The results also showed that the stabilization effect of phalloidin binding to ADP.BeF x or ADP.AlF 4-bound actin filaments was not cooperative. Since the effect of phalloidin binding was cooperative in the absence of these nucleotide analogues, these results suggest that the binding of ADP.BeF x or ADP.AlF 4 to the actin modified the protomer-protomer interactions along the actin filaments.     

Immunolocalization of a novel annexin‐like protein encoded by a stress and abscisic acid responsive gene in alfalfa

We report here on the isolation and characterization of a full-length cDNA clone from alfalfa termed AnnMs2 encoding a 333 amino acid long polypeptide that shows 32–37% sequence identity with both mammalian and plant annexins, and has four tandem repeats. While other plant annexins exhibit a high level of sequence similarity to each other (up to 77% identity at amino acid level), AnnMs2 appears to be a distinct type of plant annexins. All the four endonexin folds contain the conserved eukaryotic motif within this alfalfa protein, but this element is considerably different in the second repeat. The AnnMs2 gene is expressed in various tissues of alfalfa with elevated mRNA accumulation in root and flower. This gene is activated in cells or tissues exposed to osmotic stress, abscisic acid (ABA) or water deficiency. The recombinant AnnMs2 protein is able to bind to phospholipid in the presence of Ca²⁺. Indirect immunofluorescence studies using affinity purified rabbit anti-AnnMs2 peptide antibody show mainly nucleolar localization, but the protein sequence lacks the usual nuclear localization signal. The potential role of this novel annexin-like protein in the basic and stress-induced cellular functions is discussed.     

The role of sampling effort,taxonomical resolution and abundance weight in multivariate comparison of stream dwelling caddisfly assemblages collected from riffle and pool habitats

We examined how the sample representativeness of a single assemblage and the separation of two assemblages can be improved by finding appropriate combinations of sampling effort, taxonomical resolution and abundance weight for stream dwelling caddisflies as model organisms. We found that these parameters strongly influenced the outcome of multivariate analyses both individually and when considered jointly. This is the first study to show that sample representativeness of an assemblage can decrease with increasing sampling effort. We assume that the turnover rate of the assemblage and the rarity of the species are responsible for this phenomenon. We found that the separation of two assemblages can be improved by increasing sampling effort and applying abundance data. Further, we observed that the effect of taxonomical resolution on the separation of ecological assemblages was highly context-dependent. Decreased taxonomical resolution, i.e. changing from species to genus or to family, did not decrease, or even more increased the separation of assemblages. In sum, this study demonstrates the importance of the careful selection of sampling, laboratory and data processing related factors (i.e. sampling effort, taxonomical resolution, abundance weight) in the multivariate comparison of assemblages.     

Juxtacellular Monitoring and Localization of Single Neurons within Sub-cortical Brain Structures of Alert,Head-restrained Rats

There are a variety of techniques to monitor extracellular activity of single neuronal units. However, monitoring this activity from deep brain structures in behaving animals remains a technical challenge, especially if the structures must be targeted stereotaxically. This protocol describes convenient surgical and electrophysiological techniques that maintain the animal’s head in the stereotaxic plane and unambiguously isolate the spiking activity of single neurons. The protocol combines head restraint of alert rodents, juxtacellular monitoring with micropipette electrodes, and iontophoretic dye injection to identify the neuron location in post-hoc histology. While each of these techniques is in itself well-established, the protocol focuses on the specifics of their combined use in a single experiment. These neurophysiological and neuroanatomical techniques are combined with behavioral monitoring. In the present example, the combined techniques are used to determine how self-generated vibrissa movements are encoded in the activity of neurons within the somatosensory thalamus. More generally, it is straightforward to adapt this protocol to monitor neuronal activity in conjunction with a variety of behavioral tasks in rats, mice, and other animals. Critically, the combination of these methods allows the experimenter to directly relate anatomically-identified neurophysiological signals to behavior.     

Effect of landscape context on fish metacommunity structuring in stream networks

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Design, synthesis, and biological evaluation of 8-biarylquinolines: a novel class of PDE4 inhibitors

The structure-activity relationship of a novel series of 8-biarylquinolines acting as type 4 phosphodiesterase (PDE4) inhibitors is described herein. Prototypical compounds from this series are potent and non-selective inhibitors of the four distinct PDE4 (IC(50)<10 nM) isozymes (A-D). In a human whole blood in vitro assay, they inhibit (IC(50)<0.5 microM) the LPS-induced release of the cytokine TNF-alpha. Optimized inhibitors were evaluated in vivo for efficacy in an ovalbumin-induced bronchoconstriction model in conscious guinea pigs. Their propensity to produce an emetic response was evaluated by performing pharmacokinetic studies in squirrel monkeys. This work has led to the identification of several compounds with excellent in vitro and in vivo profiles, including a good therapeutic window of efficacy over emesis.     

Hybrid solar cells

Historically, conventional solar cells were built from inorganic materials such as silicon. Although the efficiency of such conventional solar cells is high, very expensive materials and energy intensive processing techniques are required.Hybrid and photoelectrochemical (dye sensitized) solar cells have been the cheap alternatives for conventional silicon solar cells. A hybrid solar cell consists of a combination of both organic and inorganic materials therefore, combines the unique properties of inorganic semiconductors with the film forming properties of the conjugated polymers. Organic materials are inexpensive, easily processable and their functionality can be tailored by molecular design and chemical synthesis. On the other hand, inorganic semiconductors can be manufactured as nanoparticles and inorganic semiconductor nanoparticles offer the advantage of having high absorption coefficients and size tunability. By varying the size of the nanoparticles the bandgap can be tuned therefore the absorption range can be tailored.In this short review, we will focus on the concepts of organic/inorganic “hybrid” solar cells.     

Combining taxon‐by‐trait and taxon‐by‐site matrices for analysing trait patterns of macroinvertebrate communities: a rejoinder to Monaghan & Soares ()

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Immunodetection of retinoblastoma-related protein and its phosphorylated form in interphase and mitotic alfalfa cells

Plant retinoblastoma-related (RBR) proteins are primarily considered as key regulators of G(1)/S phase transition, with functional roles in a variety of cellular events during plant growth and organ development. Polyclonal antibody against the C-terminal region of the Arabidopsis RBR1 protein also specifically recognizes the alfalfa 115?kDa MsRBR protein, as shown by the antigen competition assay. The MsRBR protein was detected in all cell cycle phases, with a moderate increase in samples representing G(2)/M cells. Antibody against the human phospho-pRb peptide (Ser807/811) cross-reacted with the same 115?kDa MsRBR protein and with the in vitro phosphorylated MsRBR protein C-terminal fragment. Phospho-MsRBR protein was low in G(1) cells. Its amount increased upon entry into the S phase and remained high during the G(2)/M phases. Roscovitine treatment abolished the activity of alfalfa MsCDKA1;1 and MsCDKB2;1, and the phospho-MsRBR protein level was significantly decreased in the treated cells. Colchicine block increased the detected levels of both forms of MsRBR protein. Reduced levels of the MsRBR protein in cells at stationary phase or grown in hormone-free medium can be a sign of the division-dependent presence of plant RBR proteins. Immunolocalization of the phospho-MsRBR protein indicated spots of variable number and size in the labelled interphase nuclei and high signal intensity of nuclear granules in prophase. Structures similar to phospho-MsRBR proteins cannot be recognized in later mitotic phases. Based on the presented western blot and immunolocalization data, the possible involvement of RBR proteins in G(2)/M phase regulation in plant cells is discussed.