Radiolytic mapping of solvent-contact surfaces in photosystem II of higher plants: Experimental identification of putative water channels within the photosystem

Background: Substrate water must reach the buried Mn4O 5Ca cluster in Photosystem II. Results: OH produced by radiolysis modified buried amino acid residues. These were mapped onto the PS II crystal structure. Conclusion: Two groups of oxidized residues were identified which form putative pathways to the Mn4O5Ca cluster. Significance: Identification of water and oxygen channels is crucial for our understanding of Photosystem II function. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc

A Micro corona motor fabricated by a SU-8 built-on X-ray mask

Abstract A micro corona motor was fabricated using a membraneless built-on X-ray mask. Sharp stator electrodes of this motor ionize air molecules and ionized charges transfer onto the rotor surface, resulting in rotating rotor motions by Coulomb forces. For good performance, the stator's electrodes should be wide (axial) and have sharp tips. Therefore, X-ray lithography was adopted for precise, high aspect ratio characteristics. To avoid the fabrication difficulty of a membrane X-ray mask, a built-on X-ray mask (conformal mask) technique was employed with negative toned SU-8 photoresist. SU-8 features X-ray fabrication compatibility, X-ray transparency and a large range of thickness. This technique may be suitable for fast fabrication of prototypes or very tall structures, which can be largely affected by printing gaps. For the X-ray built-on mask, 20 lm SU-8 was patterned and 8 lm gold absorber was electroplated on top of the 300 lm PMMA resist. Tests showed good quality pattern transfer from the SU-8 pattern and smooth sidewalls. Introduction Corona motors, a unique type of electrostatic motor [1], have not been developed in the micro domain. This motor uses repulsive forces between charges of like polarity applied to stator electrodes and the charges induced via corona action onto rotor surface, to create rotating motion. Sharp edges of the stator's electrodes generate highly non-uniform fields; the tips of these long electrodes are close to the surface of the rotor. Since strong electric fields can ionize air molecules, resulting in a corona, the surface of the rotor can be charged by means of a partial corona discharge from the stator electrodes. In motor operation, the stator and rotor charges interact to produce both torque and bearing lift. Driving forces of past electrostatic micromotors (e.g., variable capacitance and induction motors) arose from Coulomb attraction between opposite charges. Coulomb's electrostatic force increases as distance between charge s decreases. Out of tolerance between a bearing and rotor produces unwanted radial motions of the rotor, which changes the air gap and disturbs the forces. A small disturbance can unbalance the rotor, and the resulting radial motions of the rotor increase contact, friction, and wear, which limit life. In the corona motor introduced in this paper, repulsion between like charged stator electrodes and rotor surface charges levitate the rotor, augmenting bearing action and avoiding stiction and friction. The design of this motor demands small dimensions, high tolerances, large aspect ratios, and very sharp electrodes. X-ray lithography was adopted for fabrication of this motor, because the short wavelength of X-rays can satisfy the following geometric specifications. First, the smallest possible tip radius of a sharp electrode is determined by the wavelength of the light sourc

Effectiveness of aqueous and hydroalcoholic extracts of Acanthospermum australe (Loefl.) Kuntze against diarrhea-inducing bacteria

<div><p>Abstract Leaves and roots of Acanthospermum australe (Asteraceae) have been used in Brazilian folk medicine for the treatment of various ailments including diarrhea, skin diseases, blennorrhagia, dyspepsia, parasitic worms and malaria. The aim of study was to characterize the chemical profiles of the aqueous and hydroalcoholic extracts of leaves and roots of A. australe, and to evaluate their antimicrobial activities against diarrhea-inducing bacteria (Enterococcus faecalis, Shigella dysenteriae and Yersinia enterocolitica), as well as their cytotoxic properties. Aqueous leaf extracts were obtained by infusion, while aqueous root extracts were obtained by decoction. The hydroalcoholic leaf and root extracts were prepared by maceration in 90% ethanol for 3 days. Antimicrobial activity was assessed using standard techniques and cytotoxicity was evaluated using Chinese hamster ovary cells CHO-K1. Chemical analysis revealed the presence of tannins, flavonoids, saponins and phenolic compounds in the extracts. Although root extracts were not effective against E. faecalis, leaf extracts at concentrations of 20 mg/mL exhibited bactericidal activities against this microorganism. The hydroalcoholic root extract was unique in presenting a bactericidal effect against S. dysenteriae. None of the extracts showed bacteriostatic or bactericidal activities against Y. enterocolitica. The results presented herein demonstrate that the Gram-positive E. faecalis and the Gram-negative S. dysenteriae were susceptible to A. australe extracts, although bacteriostatic/bactericidal activities were only observed at concentrations considered too high for clinical application. Our results support the ethnopharmacological use of A. australe in the treatment of gastrointestinal disorders, particularly diarrhea caused by infectious bacteria, although further studies are required to determine the anti-diarrhea effects and the toxicities of the extracts in vivo.</p></div

Disclosing the antitumour potential of the marine bromoditerpene sphaerococcenol a on distinct cancer cellular models

Nature has revealed to be a key source of innovative anticancer drugs. This study evaluated the antitumour potential of the marine bromoditerpene sphaerococcenol A on different cancer cellular models. Dose-response analyses (0.1–100 μM; 24 h) were accomplished in eight different tumour cell lines (A549, CACO-2, HCT-15, MCF-7, NCI-H226, PC-3, SH-SY5Y, SK-MEL-28). Deeper studies were conducted on MFC-7 cells, namely, determination of hydrogen peroxide (H2O2) levels and evaluation of apoptosis biomarkers (phosphatidylserine membrane translocation, mitochondrial dysfunction, Caspase-9 activity, and DNA changes). The ability of the compound to induce genotoxicity was verified in L929 fibroblasts. Sphaerococcenol A capacity to impact colorectal-cancer stem cells (CSCs) tumourspheres (HT29, HCT116, SW620) was evaluated by determining tumourspheres viability, number, and area, as well as the proteasome inhibitory activity. Sphaerococcenol A hepatoxicity was studied in AML12 hepatocytes. The compound exhibited cytotoxicity in all malignant cell lines (IC50 ranging from 4.5 to 16.6 μM). MCF-7 cells viability loss was accompanied by H2O2 generation, mitochondrial dysfunction, Caspase-9 activation and DNA nuclear morphology changes. Furthermore, the compound displayed the lowest IC50 on HT29-derived tumourspheres (0.70 μM), followed by HCT116 (1.77 μM) and SW620 (2.74 μM), impacting the HT29 tumoursphere formation by reducing their number and area. Finally, the compound displayed low cytotoxicity on AML12 hepatocytes without genotoxicity. Overall, sphaerococcenol A exhibits broad cytotoxic effects on different tumour cells, increasing H2O2 production and apoptosis. It also affects colorectal CSCs-enriched tumoursphere development. These data highlight the elevance to include sphaerococcenol A in further pharmacological studies aiming cancer treatments.info:eu-repo/semantics/publishedVersio