Cd(II)-ethylenediamine mono- and bimetallic complexes - Synthesis and characterization by Cd NMR spectroscopy and single crystal X-ray diffraction

Formation of three Cd(II)-ethylenediamine (en) complexes ([Cd(en)_n]²⁺, n = 1-3) in aqueous solution and in DMSO solvent has been established by means of ¹¹³Cd NMR spectroscopy. It is clearly shown that Cd(II)-en complexes form primarily in basic solutions. A correlation between the ¹¹³Cd NMR chemical shifts and the ethylenediamine (en) coordination number has been observed and discussed. Two single crystals with the composition [Cd₂(en)₅](ClO₄)₄ (1) and [Cd(en)₃](ClO₄)₂ (2) were prepared from aqueous solution, and their structures were determined by single crystal X-ray diffraction. Cd(II) ions are coordinated by six atoms in both compounds, 1 and 2: via five N-donor atoms and one O-donor atom forming a bimetallic complex 1, and via six N-donor atoms forming a distorted octahedral monometallic complex 2. Raman spectra of complexes 1 and 2 also provide additional evidence that the cis-form of the bridging en is present in complex 1.     

Rieske business: structure-function of Rieske non-heme oxygenases

Rieske non-heme iron oxygenases (RO) catalyze stereo- and regiospecific reactions. Recently, an explosion of structural information on this class of enzymes has occurred in the literature. ROs are two/three component systems: a reductase component that obtains electrons from NAD(P)H, often a Rieske ferredoxin component that shuttles the electrons and an oxygenase component that performs catalysis. The oxygenase component structures have all shown to be of the alpha3 or alpha3beta3 types. The transfer of electrons happens from the Rieske center to the mononuclear iron of the neighboring subunit via a conserved aspartate, which is shown to be involved in gating electron transport. Molecular oxygen has been shown to bind side-on in naphthalene dioxygenase and a concerted mechanism of oxygen activation and hydroxylation of the ring has been proposed. The orientation of binding of the substrate to the enzyme is hypothesized to control the substrate selectivity and regio-specificity of product formation.     

Effect of dynamic loading on the frictional response of bovine articular cartilage

The objective of this study was to test the hypotheses that (1) the steady-state friction coefficient of articular cartilage is significantly smaller under cyclical compressive loading than the equilibrium friction coefficient under static loading, and decreases as a function of loading frequency; (2) the steady-state cartilage interstitial fluid load support remains significantly greater than zero under cyclical compressive loading and increases as a function of loading frequency. Unconfined compression tests with sliding of bovine shoulder cartilage against glass in saline were carried out on fresh cylindrical plugs (n=12), under three sinusoidal loading frequencies (0.05, 0.5 and 1 Hz) and under static loading; the time-dependent friction coefficient mu(eff) was measured. The interstitial fluid load support was also predicted theoretically. Under static loading mu(eff) increased from a minimum value (mu(min)=0.005+/-0.003) to an equilibrium value (mu(eq)=0.153+/-0.032). In cyclical compressive loading tests mu(eff) similarly rose from a minimum value (mu(min)=0.004+/-0.002, 0.003+/-0.001 and 0.003+/-0.001 at 0.05, 0.5 and 1 Hz) and reached a steady-state response oscillating between a lower-bound (mu(lb)=0.092+/-0.016, 0.083+/-0.019 and 0.084+/-0.020) and upper bound (mu(ub)=0.382+/-0.057, 0.358+/-0.059, and 0.298+/-0.061). For all frequencies it was found that mu(ub)>mu(eq) and mu(lb)相似文献   

Role of ATP sensitive potassium channel on 7-hydroxy flavone induced antinociception and possible association with changes in glycaemic status

Opioid type of analgesics open ATP sensitive potassium channel at the cellular level to produce antinociceptive response. These channels have also been shown to modulate insulin secretion by the pancreas. 7-hydroxy flavone, an antinociceptive agent shown to act through opioid pathways was investigated for its effect on glycaemic state and associated algesic state. The involvement of ATP sensitive potassium channel in the action was examined by using glybenclamide. The result reveal that 7-HF per se did not elicit any significant change in the glycaemic state simultaneously eliciting antinociceptive response as tested by acetic acid induced abdominal constriction assay procedure. Glibenclamide treatment attenuated the antinociceptive effect of 7-HF and while maintained its hypoglycaemic response. The present finding suggest that 7-HF induces antinociception like morphine, utilise ATP sensitive potassium channel at the cellular level and do not suggest a cause-effect relationship between the changes in the glycaemic and algesic state. Possibly, insulin which is controlled by ATP sensitive potassium channel at the cellular level might also modulate antinociception exhibiting a cause-effect relationship between them.     

Sex pheromones of Callosobruchus subinnotatus and C. maculatus (Coleoptera: Bruchidae): congeneric responses and role of air movement

Females of Callosobruchus spp. are known to produce sex pheromones that attract males. These sex pheromones cannot be adopted for use in pest management without first investigating the responses of the males in the windless conditions of storage environments. Consequently, behavioural bioassays of Callosobruchus subinnotatus Pic males were conducted in an olfactometer in the absence of air-flow. Under these conditions males were found to be able to follow odour trails to the source. However, the latency period was longer in diffusional bioassays than for insects in a Y-tube olfactometer that provided directional wind cues. The highest percentage of males reached the pheromone source when components of the pheromones, (E)-3-methyl-2-heptenoic acid (E32A) and (Z)-3-methyl-2-heptenoic acid (Z32A), were formulated in a 50:50 or 25:75 ratio. Males of C. maculatus (Fabricius) responded to sex pheromone of C. subinnotatus, but males of C. subinnotatus did not respond to that of C. maculatus. The two sex pheromone components of C. subinnotatus are also constituents of C. maculatus sex pheromone. These two components may be potentially useful in monitoring the populations of both species in stored beans. It is postulated that (Z)-3-methyl-3-heptenoic acid (Z33A), the major component of the sex pheromone of C. maculatus, must have acted as an antagonist inhibiting response of C. subinnotatus to the sex pheromone of C. maculatus.     

Phosphorylation of the PTEN tail regulates protein stability and function

The PTEN gene is a tumor suppressor localized in the frequently altered chromosomal region 10q23. The tumor suppressor function of the PTEN protein (PTEN) has been linked to its ability to dephosphorylate the lipid second-messenger phosphatidylinositol 3,4, 5-trisphosphate and phosphatidylinositol 3,4-bisphosphate and, by doing so, to antagonize the phosphoinositide 3-kinase pathway. The PTEN protein consists of an amino-terminal phosphatase domain, a lipid binding C2 domain, and a 50-amino-acid C-terminal domain (the "tail") of unknown function. A number of studies have shown that the tail is dispensable for both phosphatase activity and blocking cell growth. Here, we show that the PTEN tail is necessary for maintaining protein stability and that it also acts to inhibit PTEN function. Thus, removing the tail results in a loss of stability but does not result in a loss of function because the resultant protein is more active. Furthermore, tail-dependent regulation of stability and activity is linked to the phosphorylation of three residues (S380, T382, and T383) within the tail. Therefore, the tail is likely to mediate the regulation of PTEN function through phosphorylation.     

Choristoneura fumiferana entomopoxvirus prevents metamorphosis and modulates juvenile hormone and ecdysteroid titers

Larvae of the spruce budworm, Choristoneura fumiferana, infected with C. fumiferana entomopoxvirus (CfEPV) continue to feed and grow without undergoing metamorphosis and die as moribund larvae. The lethal dose (LD(50)) and lethal time (LT(50)) values for fourth instar larvae are 2.4 spheroids and 25.2 days, respectively. One hundred percent of the control fourth instar larvae, which were fed water instead of virus, pupated by 18 days post feeding (PF). Only 30% of the larvae that were fed the LD(50) dose and none of the larvae that were fed the LD(95) dose pupated by 18 days PF. Of the control larvae, 95% became adults by 24 days PF, whereas in the treated group only 2% of larvae that were fed the LD(50) dose and none of the larvae that were fed the LD(95) dose became adults by 24 days PF. Some of the virus-treated larvae died as either larval/pupal or pupal/adult intermediates. These phenotypic effects were similar to the larval/pupal and pupal/adult intermediates, resulting from treating larvae with juvenile hormone (JH) or its analogs, which suggests that EPV may cause such abnormalities by modulating JH and/or ecdysteroid titers. In untreated sixth instar larvae the JH titer decreased to low levels by 24 h after ecdysis and remained low throughout larval life. EPV-fed sixth instar larvae had 2112 pg/ml on day 0, 477 pg/ml on day 1 and 875 pg/ml on day 8 of the sixth instar. Control larvae contained 860 ng of ecdysteroids per ml hemolymph on day 8 of the sixth instar, whereas EPV-treated larvae of the same age (30 days PF) had only 107 ng of ecdysteroids per ml of hemolymph. Thus, EPV infection results in increased JH titer and decreased ecdysteroid titer. Northern hybridization analysis was performed using RNA isolated from control and EPV-fed larvae and cDNA probes for (i) juvenile hormone esterase (JHE), which is JH inducible, (ii) Choristoneura hormone receptor 3 (CHR3), which is ecdysteroid inducible, and (iii) larval specific diapause associated protein 1 (DAP1), whose expression is larval specific. EPV-treated larvae showed higher levels of JHE and DAP1 mRNA and lower levels of CHR3 mRNA, indicating that they had higher levels of JH and lower levels of ecdysteroids. Thus, our data show that EPV prevents metamorphosis by modulating ecdysteroid and JH levels.     

Adaptation of bacterial communities to environmental transitions from labile to refractory substrates

The aim of this work was to assess the adaptation of bacterial communities to environmental transitions from labile to refractory substrates. This involved testing the hypothesis that bacteria self-organize and propagate not only as individual cellular systems, but also as functional sets of interacting organisms. A biofilm community was cultivated in a flow-cell irrigated with tryptic soy broth and subjected to a cyclic series of environmental transitions, from labile to refractory substrates, followed by a period of starvation (30 days). The appearance and disappearance of specific colony morphotypes when the emigrants were plated onto tryptic soy agar was used to monitor the restructuring of the community. Confocal laser microscopy of flow cells showed that these transitions decreased the biofilm thickness and coverage. Substrate shifts also changed the architecture of the biofilm communities. Repeated inoculation of flow-cell communities with a composite inoculum increased the number and diversity of emigrants. Their biofilms were thicker and covered a wider area than those of communities that had been inoculated only at the beginning of the experiment. With repeated inoculation, the time required for the community to restructure and stabilize decreased during most transitions. This suggested that organismal recombination acted as a mechanism of adaptation, enhancing the growth of microbial communities exposed to environmental stresses. Changes in the profiles of emigrants during the adaptation of biofilm communities to environmental transitions showed the appearance and disappearance of discrete sets of organisms. This suggested that the biofilm communities responded to environmental stresses as sets of interacting organisms. Enhanced growth of biofilm communities due to repeated environmental cycling suggested that the functionality of cellular positioning accrued from one cycle to the next and was thus heritable, although it was not necessarily genetically encoded.