Targeted quantum dot conjugates for siRNA delivery

Treatment of human diseases such as cancer generally involves the sequential use of diagnostic tools and therapeutic modalities. Multifunctional platforms combining therapeutic and diagnostic imaging functions in a single vehicle promise to change this paradigm. in particular, nanoparticle-based multifunctional platforms offer the potential to improve the pharmacokinetics of drug formulations, while providing attachment sites for diagnostic imaging and disease targeting features. We have applied these principles to the delivery of small interfering RNA (siRNA) therapeutics, where systemic delivery is hampered by rapid excretion and nontargeted tissue distribution. Using a PEGlyated quantum dot (QD) core as a scaffold, siRNA and tumor-homing peptides (F3) were conjugated to functional groups on the particle's surface. We found that the homing peptide was required for targeted internalization by tumor cells, and that siRNA cargo could be coattached without affecting the function of the peptide. Using an EGFP model system, the role of conjugation chemistry was investigated, with siRNA attached to the particle by disulfide cross-linkers showing greater silencing efficiency than when attached by a nonreducible thioether linkage. Since each particle contains a limited number of attachment sites, we further explored the tradeoff between number of F3 peptides and the number of siRNA per particle, leading to an optimized formulation. Delivery of these F3/siRNA-QDs to EGFP-transfected HeLa cells and release from their endosomal entrapment led to significant knockdown of EGFP signal. By designing the siRNA sequence against a therapeutic target (e.g., oncogene) instead of EGFP, this technology may be ultimately adapted to simultaneously treat and image metastatic cancer.     

Do Insectivorous Birds use Volatile Organic Compounds from Plants as Olfactory Foraging Cues? Three Experimental Tests

Some insectivorous birds orient towards insect‐defoliated trees even when they do not see the foliar damage or the herbivores. There are, however, only a few studies that have examined the mechanisms behind this foraging behaviour. Previous studies suggest that birds can use olfactory foraging cues (e.g. volatile organic compounds (VOCs) emitted by defoliated plants), indirect visual cues or a combination of the two sensory cues. VOCs from insect‐defoliated plants are known to attract natural enemies of herbivores, and researchers have hypothesized that VOCs could also act as olfactory foraging cues for birds. We conducted three experiments across a range of spatial scales to test this hypothesis. In each experiment, birds were presented with olfactory cues and their behavioural responses or foraging outcomes were observed. In the first experiment, two different VOC blends, designed to simulate the volatile emissions of mountain birch (Betula pubescens ssp. czerepanovii) after defoliation by autumnal moth (Epirrita autumnata) larvae, were used in behavioural experiments in aviaries with pied flycatchers (Ficedula hypoleuca). The second experiment was a field‐based trial of bird foraging efficiency; the same VOC blends were applied to mountain birches, silver birches (B. pendula) and European white birches (B. pubescens) with plasticine larvae attached to the trees to serve as artificial prey for birds and provide a means to monitor predation rate. In the third experiment, the attractiveness of silver birch saplings defoliated by autumnal moth larvae versus intact controls was tested with great tits (Parus major) and blue tits (Cyanistes caeruleus) in an aviary. Birds did not orient towards either artificial or real trees with VOC supplements or towards herbivore‐damaged saplings when these saplings and undamaged alternatives were hidden from view. These findings do not support the hypothesis that olfactory foraging cues are necessary in the attraction of birds to herbivore‐damaged trees.     

Crystal structure of a human peptidyl-tRNA hydrolase reveals a new fold and suggests basis for a bifunctional activity

Peptidyl-tRNA hydrolase (Pth) activity releases tRNA from the premature translation termination product peptidyl-tRNA. Two different enzymes have been reported to encode such activity, Pth present in bacteria and eukaryotes and Pth2 present in archaea and eukaryotes. Here we report the crystallographic structure of the Homo sapiens Pth2 at a 2.0-A resolution as well as its catalytic properties. In contrast to the structure of Escherichia coli Pth, H. sapiens Pth2 has an alpha/beta fold with a four-stranded antiparallel beta-sheet in its core surrounded by two alpha-helices on each side. This arrangement of secondary structure elements generates a fold not previously reported. Its catalytic efficiency is comparable with that reported for the archaeal Sulfolobus solfataricus Pth2 and higher than that of the bacterial E. coli Pth. Several lines of evidence target the active site to two close loops with highly conserved residues. This active site architecture is unrelated to that of E. coli Pth. In addition, intermolecular contacts in the crystal asymmetric unit cell suggest a likely surface for protein-protein interactions related to the Pth2-mediated apoptosis.     

Stabilization of the activated alphaMbeta2 integrin by a small molecule inhibits leukocyte migration and recruitment

Integrins are potential targets for the development of antiinflammatory agents. Here we develop a novel high-throughput assay by allowing a chemical library to compete with phage display peptide binding and identify a novel small-molecule ligand to the leukocyte-specific alpha(M)beta(2) integrin. The identified thioxothiazolidine-containing compound, IMB-10, had an unexpected activity in that it stabilized binding of alpha(M)beta(2) to its endogenous ligands proMMP-9 and fibrinogen. Single amino acid substitutions in the activity-regulating C-terminal helix and the underlying region in the ligand-binding I domain of the integrin suppressed the effect of IMB-10. A computational model indicated that IMB-10 occupies a distinct cavity present only in the activated form of the integrin I domain. IMB-10 inhibited alpha(M)beta(2)-dependent migration in vitro and inflammation-induced neutrophil emigration in vivo. Stabilization of integrin-mediated adhesion by a small molecule is a novel means to inhibit cell migration and may have a utility in treatment of inflammatory diseases involving leukocyte recruitment.     

Optimal Locations for Methanol and CHP Production in Eastern Finland

Finland considers energy production from woody biomass as an efficient energy planning strategy to increase the domestic renewable energy production in order to substitute fossil fuel consumption and reduce greenhouse gas emissions. Consequently, a number of developmental activities are implemented in the country, and one of them is the installation of second generation liquid biofuel demonstration plants. In this study, two gasification-based biomass conversion technologies, methanol and combined heat and power (CHP) production, are assessed for commercialization. Spatial information on forest resources, sawmill residues, existing biomass-based industries, energy demand regions, possible plant locations, and a transport network of Eastern Finland is fed into a geographically explicit Mixed Integer Programming model to minimize the costs of the entire supply chain which includes the biomass supply, biomass and biofuel transportation, biomass conversion, energy distribution, and emissions. The model generates a solution by determining the optimal number, locations, and technology mix of bioenergy production plants. Scenarios were created with a focus on biomass and energy demand, plant characteristics, and cost variations. The model results state that the biomass supply and high energy demand are found to have a profound influence on the potential bioenergy production plant locations. The results show that methanol can be produced in Eastern Finland under current market conditions at an average cost of 0.22??/l with heat sales (0.34??/l without heat sales). The introduction of energy policy tools, like cost for carbon, showed a significant influence on the choice of technology and CO₂ emission reductions. The results revealed that the methanol technology was preferred over the CHP technology at higher carbon dioxide cost (>145??/t_CO2). The results indicate that two methanol plants (360?MW_biomass) are needed to be built to meet the transport fuel demand of Eastern Finland.     

Survival of male Tengmalm’s owls increases with cover of old forest in their territory

The loss and fragmentation of forest habitats have been considered to pose a worldwide threat to the viability of forest-dwelling animals, especially to species that occupy old forests. We investigated whether the annual survival of sedentary male Tengmalm’s owls Aegolius funereus was associated with the cover of old coniferous forests in Finland. Survival and recapture probabilities varied annually with density changes in populations of the main prey (Microtus voles). When this variation was controlled for, and relationships between survival and proportions of the three different forest age classes (old-growth, middle-aged, and young) were modeled separately, the old-growth model was the most parsimonious. Survival increased with the cover of old forest, although the extent of old forest within owl territories was relatively small (mean ∼12%, range 2–37%). This association, however, varied among years and appeared especially in years of increasing vole abundance. At such times, old forests may sustain high populations of bank voles Clethrionomys glareolus, shrews and small passerines. In addition, old forests may serve as refuges against large avian predator species, such as Ural owls Strix uralensis and goshawks Accipiter gentilis. Our results suggest that changes in habitat quality created by agriculture and forestry may have the potential to reduce adult survival, an essential component of fitness and population viability.     

Invasion Pressure on the Finnish Lake District: Invasion Corridors and Barriers

In a literature-based study, 29 non-indigenous species present in northeastern European waters were assessed for their potential for introduction and establishment in Finnish inland lakes. Their physiological and ecological demands were compared to abiotic and biotic lake conditions. The availability of adequate vectors was surveyed from shipping statistics for the Saimaa Canal, which connects the Finnish Lake District to the Baltic Sea. There exists a high probability for the introduction of six non-indigenous invertebrate species, i.e., Anguillicola crassus, Potamothrix heuscheri, Potamothrix vejdovskyi, Hemimysis anomala, Cercopagis pengoi and Gmelinoides fasciatus, with the Gulf of Finland as the main donor area. Barriers against new species introductions, which maintain the biological integrity of Finnish inland lakes, include low water temperature, northern isolated location, and low concentration of nutrients and major ions.