A simple mechanical technique to obtain carbon nanoscrolls from graphite nanoplatelets

A simple approach for the bulk production of carbon nanoscrolls (CNSs) is described. This method is based on the application of shear-friction forces to convert graphite nanoplatelets into carbon nanoscrolls using a bi-axially oriented polypropylene (BOPP) surface. The combined action of shear and friction forces causes the exfoliation of graphite nanoplatelets and the simultaneous roll-up of graphite layers. Evidence of the CNS formation is given by optical microscopy, scanning electron microscopy, and transmission electron microscopy. These investigations reveal that the CNSs have a long tube-like and fusiform structure with a hollow core surrounded by few layers of graphene. Micro-Raman spectroscopy shows that the produced structures are not defect free, and optical spectroscopy reveals distinctive features due to the presence of two weak absorption bands at 224 and 324 nm.     

FORMATION OF SULFATE CONJUGATES METABOLITES IN THE DEGRADATION OF PHENANTHRENE,ANTHRACENE, PYRENE AND BENZO[A]PYRENE BY THE ASCOMYCETE ASPERGILLUS TERREUS

Abstract

The metabolism of four PAHs (phenanthrene, anthracene, pyrene and benzo(a)pyrene) by an Aspergillus terreus strain, isolated from a polluted soil, was investigated in liquid submerged culture. The main metabolites identified by the HPLC-MS technique, after solvent extraction of the fermentation broth and mycelium, were aryl-sulfates and hydroxyl-aryl-sulfates. A metabolic pathway was identified involving in sequence: the hydroxylation by a monooxygenase of the PAHs, the conjugation with a sulfate ion, followed by a further hydroxylation to hydroxyl-aryl-sulfates compounds. PAHs degradation by A. terreus yielded a different number of metabolite isomers depending on the type of the parent PAH. The environmental fate and ecotoxicity of the metabolite 9-phenanthrenesulfate was also investigated by a respirometric test of ready biodegradability and by a Vibrio fischeri acute toxicity test respectively. This compound was easily degradable by microbial consortia derived from polluted soil and capable of thriving on phenanthrene as its sole carbon source. Moreover the sulfate conjugate resulted in 2 orders of magnitude less toxic than its precursors phenanthrene.     

Thermo‐responsive albumin hydrogels with LCST near the physiological temperature

This paper deals with the synthesis of thermoresponsive microspheres with proteic structure exhibiting a transition temperature close to the body temperature. The hydrogels were synthesized by free radical polymerization of methacrylate Bovine Serum Albumin (BSA‐MA) as crosslinker, and 2‐hydroxyethyl methacrylate (HEMA) and/or N‐isopropylacrylamide (NIPAAm), as hydrophilic and thermoresponsive monomers, respectively. The modification of the hydrophilic/hydrophobic balance in the polymerization feed allows to modulate the volume phase transition temperature of the macromolecular network. The hydrogels were characterized by infrared spectroscopy and thermal analyses, which showed negative thermoresponsive behavior for all compositions and, by increasing the content of the hydrophilic moieties in the network, the transition temperature was ranged from 34.2 to 36.8°C. To test the preformed materials as drug carriers, diclofenac diethyl ammonium salt was chosen and drug entrapment percent was determined. Drug release profiles, in media at different temperature, depend on the crosslinking degree and on the composition of the hydrogels. By using semiempirical equations, the release mechanism was extensively studied and the diffusional contribute evaluated. The physic‐chemical characteristics of thermoresponsive materials confirm the applicability of the microspheres as drug delivery device. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Terpenoids are widespread in actinomycetes: a correlation of secondary metabolism and genome data

The genomes of all bacteria with publicly available sequenced genomes have been screened for the presence of sesquiterpene cyclase homologues, resulting in the identification of 55 putative geosmin synthases, 23 homologues of 2-methylisoborneol synthases, and 98 other sesquiterpene cyclase homologues. Most of these enzymes by far were found in actinomycetes. The terpenoid volatiles from 35 strains, including 31 actinomycetes and four strains from other taxa, were collected by using a closed-loop stripping apparatus and identified by GC-MS. All of these bacteria apart from one strain encode sesquiterpene cyclase homologues in their genomes. The identified volatile terpenoids were grouped according to structural similarities and their biosynthetic relationship, and the results of these analyses were correlated to the available genome information, resulting in valuable new insights into bacterial terpene biosynthesis.     

A combined approach for the analysis of support groups on Facebook - the case of patients of hidradenitis suppurativa

Multimedia Tools and Applications - Hidradenitis Suppurativa (HS), also known as Acne Inversa, is a chronic, underdiagnosed, often debilitating and painful disease that affects the folds of the...     

Motor stimulant effects of caffeine in 6-hydroxydopamine-lesioned rats are dependent on previous stimulation of dopamine receptors: a different role of D1 and D2 receptors

Caffeine has been reported to induce contralateral rotational behaviour in rats bearing a unilateral 6-hydroxydopamine lesion of the dopaminergic nigrostriatal pathway. In order to define the role of dopamine receptors in the mediation of this behaviour, we have evaluated the influence of previous exposure to a dopamine receptor agonist and the importance of the time elapsed from the 6-hydroxydopamine lesion on the rotational behaviour induced by caffeine. Separate groups of rats lesioned with 6-hydroxydopamine 2 weeks previously were exposed to four administrations of the D1/D2 receptor agonist apomorphine (0.3 mg/kg s.c.) (primed) or vehicle (drug-naive). Three days later, all rats received caffeine (30 mg/kg s.c.). Drug-naive 6-hydroxydopamine-lesioned rats did not rotate in response to caffeine, while rats primed with apomorphine rotate contralaterally in response to caffeine. When apomorphine priming was paired to the same environment (hemispherical bowls) where rats received caffeine, rotational behaviour was significantly higher than that obtained in rats primed in an unpaired environment (cylinders). Repeated priming with the D2/D3 receptor agonist quinpirole (0.2 mg/kg s.c.) induced a totally context-dependent contralateral rotation in response to caffeine, while caffeine contralateral rotation was not dependent from the context after repeated priming with the D1 agonist SKF 38393 [1-phenyl-2,3,4,5-tetrahydro-(1 H)-3-benzazepine-7,8-diol hydrochloride, 3 mg/kg s.c.]. Caffeine-mediated contralateral rotation was also evaluated in rats lesioned with 6-hydroxydopamine 12 weeks previously and exposed to four administrations of apomorphine or vehicle. As for rats repeatedly exposed to vehicle or apomorphine 2 weeks after 6-hydroxydopamine lesioning, caffeine failed to induce contralateral rotation in drug-naive rats, while it did induce a partially context-dependent contralateral rotation in apomorphine-primed rats. Different from rats receiving apomorphine priming 2 weeks after 6-hydroxydopamine lesioning, in 12 week-lesioned rats, caffeine also induced contralateral rotation after one priming with apomorphine (0.3 mg/kg s.c.), a condition which fails to induce context-dependent rotation. Administration of selective antagonists of A1 (8-cyclopentyl-1,3-dipropylxanthine), (DPCPX) or A2A (5-amino-2-(2-furyl)-7-(3-phenylpropyl)-pyrazolo[4,3-e]-1 ,2,4-triazolo[5c]pirimidine), (SCH 58261) adenosine receptors failed to induce contralateral rotation either alone or in combination in 12 week-6-hydroxydopamine-lesioned rats repeatedly primed with apomorphine. All together, the results indicate that: (i) caffeine does not induce any contralateral rotation in drug-naive 6-hydroxydopamine-lesioned rats; (ii) priming with a dopamine agonist enables caffeine to induce contralateral rotation, this rotation is, however, context independent only after priming with a selective D1 agonist; (iii) contralateral rotation in response to caffeine is dependent on the time from the 6-hydroxydopamine lesion; (iv) blockade of A1 and A2A adenosine receptors with selective antagonists does not induce contralateral rotational behaviour in 6-hydroxydopamine-lesioned rats.     

Low-Frequency Harmonic Perturbations Drive Protein Conformational Changes

Protein dynamics has been investigated since almost half a century, as it is believed to constitute the fundamental connection between structure and function. Elastic network models (ENMs) have been widely used to predict protein dynamics, flexibility and the biological mechanism, from which remarkable results have been found regarding the prediction of protein conformational changes. Starting from the knowledge of the reference structure only, these conformational changes have been usually predicted either by looking at the individual mode shapes of vibrations (i.e., by considering the free vibrations of the ENM) or by applying static perturbations to the protein network (i.e., by considering a linear response theory). In this paper, we put together the two previous approaches and evaluate the complete protein response under the application of dynamic perturbations. Harmonic forces with random directions are applied to the protein ENM, which are meant to simulate the single frequency-dependent components of the collisions of the surrounding particles, and the protein response is computed by solving the dynamic equations in the underdamped regime, where mass, viscous damping and elastic stiffness contributions are explicitly taken into account. The obtained motion is investigated both in the coordinate space and in the sub-space of principal components (PCs). The results show that the application of perturbations in the low-frequency range is able to drive the protein conformational change, leading to remarkably high values of direction similarity. Eventually, this suggests that protein conformational change might be triggered by external collisions and favored by the inherent low-frequency dynamics of the protein structure.     

Molecular Lego of Human Cytochrome P450: The Key Role of Heme Domain Flexibility for the Activity of the Chimeric Proteins

The cytochrome P450 superfamily are heme-thiolate enzymes able to carry out monooxygenase reactions. Several studies have demonstrated the feasibility of using a soluble bacterial reductase from Bacillus megaterium, BMR, as an artificial electron transfer partner fused to the human P450 domain in a single polypeptide chain in an approach known as ‘molecular Lego’. The 3A4-BMR chimera has been deeply characterized biochemically for its activity, coupling efficiency, and flexibility by many different biophysical techniques leading to the conclusion that an extension of five glycines in the loop that connects the two domains improves all the catalytic parameters due to improved flexibility of the system. In this work, we extend the characterization of 3A4-BMR chimeras using differential scanning calorimetry to evaluate stabilizing role of BMR. We apply the ‘molecular Lego’ approach also to CYP19A1 (aromatase) and the data show that the activity of the chimeras is very low (<0.003 min⁻¹) for all the constructs tested with a different linker loop length: ARO-BMR, ARO-BMR-3GLY, and ARO-BMR-5GLY. Nevertheless, the fusion to BMR shows a remarkable effect on thermal stability studied by differential scanning calorimetry as indicated by the increase in T_onset by 10 °C and the presence of a cooperative unfolding process driven by the BMR protein domain. Previously characterized 3A4-BMR constructs show the same behavior of ARO-BMR constructs in terms of thermal stabilization but a higher activity as a function of the loop length. A comparison of the ARO-BMR system to 3A4-BMR indicates that the design of each P450-BMR chimera should be carefully evaluated not only in terms of electron transfer, but also for the biophysical constraints that cannot always be overcome by chimerization.     

Formal verification of the NASA runway safety monitor

The runway safety monitor (RSM) designed by Lockheed Martin is part of NASA’s effort to reduce aviation accidents. We developed a Petri net model of the RSM protocol and used the model checking functions of our tool (stochastic and model checking analyzer for reliability and timing) SMART (Stochestic and model checking analyses for seliability and tunnig) to investigate a number of safety properties for the RSM. To mitigate the impact of state-space explosion, we built a highly discretized model of the system, obtained by partitioning the monitored runway zone into a grid of smaller volumes and by considering scenarios involving only two aircraft. The model also assumes that there are no communication failures, such as bad input from radar or lack of incoming data, thus it relies on a consistent view of reality by all participants. In spite of these simplifications, we were able to expose potential problems in the conceptual design of RSM. Our findings were forwarded to the design engineers, who undertook corrective action. Additionally, the results stress the efficiency attained by the new model checking algorithms implemented in SMART, and demonstrate their applicability to real-world systems. Attempts to verify RSM with similar NuSMV and SPIN models have failed due to excessive memory consumption. Work supported in part by the National Aeronautics and Space Administration under grant NAG-1-02095 and by the National Science Foundation under grants CCR-0219745 and ACI-0203971.