Development of a set of simple bacterial biosensors for quantitative and rapid measurements of arsenite and arsenate in potable water

Testing for arsenic pollution is commonly performed with chemical test kits of unsatisfying accuracy. Bacterial biosensors are an interesting alternative as they are easily produced, simple, and highly accurate devices. Here, we describe the development of a set of bacterial biosensors based on a nonpathogenic laboratory strain of Escherichia coli, the natural resistance mechanism of E. coli against arsenite and arsenate, and three reporter proteins: bacterial luciferase, beta-galactosidase and Green Fluorescent Protein (GFP). The biosensors were genetically optimized to reduce background expression in the absence of arsenic. In calibration experiments with the biosensors and arsenite-amended potable water, arsenite concentrations at 4 microg of As/L (0.05 microM) were routinely and accurately measured. The currently most quantitative system expressed the bacterial luciferase as reporter protein, responding proportional with a concentration range between 8 and 80 microg of As/L. Sensor cells could be stored as frozen batches, resuspended in plain media, and exposed to the aqueous test sample, and light emission was measured after 30-min incubation. Field testing for arsenite was achieved with a system that contained beta-galactosidase, producing a visible blue color at arsenite concentrations above 8 microg/L. For this sensor, a protocol was developed in which the sensor cells were dried on a paper strip and placed in the aqueous test solution for 30 min after which time color development was allowed to take place. The GFP sensor showed good potential for continuous rather than end point measurements. In all cases, growth of the biosensors and production of the strip test was achieved by very simple means with common growth media, and quality control of the sensors was performed by isolating the respective plasmids with the genetic constructs according to simple standard genetic technologies. Therefore, the biosensor cells and protocols may offer a realistic alternative for measuring arsenic contamination in potable water.     

Melissa officinalis: Composition,Pharmacological Effects and Derived Release Systems—A Review

Melissa officinalis is a medicinal plant rich in biologically active compounds which is used worldwide for its therapeutic effects. Chemical studies on its composition have shown that it contains mainly flavonoids, terpenoids, phenolic acids, tannins, and essential oil. The main active constituents of Melissa officinalis are volatile compounds (geranial, neral, citronellal and geraniol), triterpenes (ursolic acid and oleanolic acid), phenolic acids (rosmarinic acid, caffeic acid and chlorogenic acid), and flavonoids (quercetin, rhamnocitrin, and luteolin). According to the biological studies, the essential oil and extracts of Melissa officinalis have active compounds that determine many pharmacological effects with potential medical uses. A new field of research has led to the development of controlled release systems with active substances from plants. Therefore, the essential oil or extract of Melissa officinalis has become a major target to be incorporated into various controlled release systems which allow a sustained delivery.     

Processing of soft pupae and uneclosed pharate adults of Drosophila for scanning electron microscopy

For over four decades, scanning electron microscopy (SEM) has been used in research involving Drosophila genetics and developmental biology. It allows for observation and documentation of the gross morphology of exoskeletal structures as well as their characterization at very high resolution. In most cases, SEM in Drosophila has been limited to imaging adult heads, thoraces, appendages, and embryos, as these structures are relatively hard and/or easy to process for SEM. In contrast, the structures of the pharate adult stages are difficult to prepare for SEM because their integument is quite soft, they are extremely dirty and they are resistant to the usual processing methods. Here, we present an innovative method to prepare these types of structures. Our protocol efficiently removes extraneous material originating from the exuvial fluid of pharate adults and uses a hydrophobic expansion step to keep the soft exoskeleton of the body inflated. In addition to using immersion fixation, it utilizes fixation within the body that occurs via a reaction between osmium tetroxide and alcohols that are infiltrated into the body during a hydrophobic expansion step. This novel approach results in a properly inflated integument that retains its shape in subsequent procedures. Our method provides a useful, general alternative for processing difficult samples, including soft, biological "whole-mount" specimens and samples that are extremely dirty or resistant to fixative penetration.     

Effect of surface phosphorus functionalities of activated carbons containing oxygen and nitrogen on electrochemical capacitance

Micro/mesoporous activated carbons containing oxygen and phosphorus heteroatoms were modified by incorporation of nitrogen using melamine and urea precursors. The surface chemistry was analyzed by the means of elemental analysis, XPS, and ³¹P MAS NMR. The results indicate that upon the incorporation of nitrogen at high temperatures not only new species involving carbon/nitrogen/oxygen are formed but also the phosphorous environment is significantly altered. Both urea and melamine precursors have similar effects on formation of P-N and P-C bonds. These compounds, although present in small but measurable quantities seem to affect the performance of carbons in electrochemical capacitors. With an increase in the heterogeneity of phosphorus containing species and with a decrease in the content pyrophosphates the capacitance increases and the retention ratio of the capacitor is improved.     

Untersuchungen von Gleitfiguren im Klydonographgebiet durch Strom- und Spannungsmessungen mit dem Kathodenstrahloszillographen

Zusammenfassung Mit einem Kathodenstrahloszillographen wurden Spannungsmessungen an Klydonographenfiguren auf Hartgummiplatten und Photoplatten durchgeführt. Der Vorteil dieser Untersuchungen war, da\ bei jedem Sto\ Vergleiche zwischen Gleitfiguren und den Oszillogrammen der Spannungsstö\e gezogen werden konnten. Mit diesen Verfahren wurden bei beiden Polaritäten die Abhängigkeit der Form der Gleitfiguren von der Steilheit und Spannung der Wanderwelle untersucht.Weiter wurden Versuche für die Messung der Ausbreitungsgeschwindigkeit der Gleitfiguren durchgeführt, und dabei gefunden, da\ diese Geschwindigkeit bei beiden Polaritäten proportional der Steilheit ist. Durch diese Versuche konnte auch festgestellt werden, da\ bei positiven Stö\en die Gleitfiguren in Bereichen kleinerer Steilheiten (1 kV/s) nicht mehr wachsen, gleichgültig ob die Höchstspannung erreicht ist oder nicht, während bei negativen Stö\en die Gleitfiguren, sogar nachdem die Wanderwelle ihren grö\ten Wert erreicht hat, nicht weiter wachsen können.Durch die Stromversuche mit einer besonderen, in den Kathodenstrahloszillographen eingebauten Spule wurden die Ströme dieser Gleitfiguren gemessen und die Ladungen (Q=i · t) ermittelt. Schlie\lich wurden die Kapazitäten (C=Q/U) der Gleitfiguren bei verschiedenen Spannungen errechnet. Auf Grund der schon veröffentlichten Annahmen anderer Verfasser wurde versucht, die durch diese Arbeit gewonnenen Ergebnisse zu erklären.     

Specific anion and cation capacitance in porous carbon blacks

Porous carbon black was modified to introduce oxygen and nitrogen surface functionality and characterized using wet titration methods, elemental analysis, XPS, TEM, thermal analysis, adsorption of nitrogen and carbon dioxide. Then the electrochemical capacitance was measured for cations and anions in 1 M H₂SO₄. The results were compared to those obtained on activated carbons. The modified carbon black samples have four times higher adsorption of anions than cations. It is hypothesized that the graphitic microstructure of carbon blacks with structural defects is responsible for intercalation of anions in-between the graphene layers which take place at potentials higher than 0.75 V vs. Ag/AgCl and at moderately low current loads. This process is reversible and the deintercalation occurs at approximately 0.4 V vs. Ag/AgCl during the cathodic reduction. Introduction of nitrogen have generally a detrimental effect on the anion adsorption capacitance due to a structural defects blockage. At high current loads this phenomenon of enhanced anion adsorption capacitance becomes less pronounced due to the kinetic limitations. For amorphous activated carbons enhanced anion electrosorption at low current loads is governed by proton assistance while at high current loads larger cation capacitance is due to the pseudocapacitive interactions of protons with nitrogen and oxygen functional groups.     

Layer by layer deposition of hydroxyapatite onto the collagen matrix

Layer by layer (LbL) deposition is a useful method for deposition of many inorganic (including metals, oxides and phosphates) and organic (including polymers and proteins) components on a large range of substrates. The LbL deposition of hydroxyapatite (HA) onto a collagen matrix involves HA synthesis on the collagen matrix starting from electrically charged precursors such as Ca²⁺ and PO₄³⁻ at a proper pH to precipitate the desired calcium phosphate.The LbL deposition process was continuously monitored in order to study the amount of HA deposited in each layer. The deposition of the first layers of HA was concluded to be highly influenced by the collagen matrix. When the collagen matrix is crosslinked with glutaraldehyde, the matrix structure is not modified during the deposition, and the porosity will decrease with the number of layers until saturation is reached. Following pore saturation, HA will be only deposited onto the mineralized collagen matrix surface. The obtained composite materials were characterized by XRD, SEM, DTA-TG and FTIR.     

Combined Effect of Nitrogen‐ and Oxygen‐Containing Functional Groups of Microporous Activated Carbon on its Electrochemical Performance in Supercapacitors

Microporous activated carbon originating from coconut shell, as received or oxidized with nitric acid, is treated with melamine and urea and heated to 950 °C in an inert atmosphere to modify the carbon surface with nitrogen‐ and oxygen‐containing groups for a systematic investigation of their combined effect on electrochemical performance in 1 M H₂SO₄ supercapacitors. The chemistry of the samples is characterized using elemental analysis, Boehm titration, potentiometric titration, and X‐ray photoelectron spectroscopy. Sorption of nitrogen and carbon dioxide is used to determine the textural properties. The results show that the surface chemistry is affected by the type of nitrogen precursor and the specific groups present on the surface before the treatment leading to the incorporation of nitrogen. Analysis of the electrochemical behavior of urea‐ and melamine‐treated samples reveal pseudocapacitance from both the oxygen and the nitrogen containing functional groups located in the pores larger than 10 Å. On the other hand, pores between 5 Å and 6 Å are most effective in a double‐layer formation, which correlates well with the size of hydrated ions. Although the quaternary and pyridinic‐N‐oxides nitrogen groups have enhancing effects on capacitance due to the positive charge, and thus an improved electron transfer at high current loads, the most important functional groups affecting energy storage performance are pyrrolic and pyridinic nitrogen along with quinone oxygen.     

Ibuprofen,Flurbiprofen, Etoricoxib or Paracetamol Do Not Influence ACE2 Expression and Activity In Vitro or in Mice and Do Not Exacerbate In-Vitro SARS-CoV-2 Infection

SARS-CoV-2 uses the human cell surface protein angiotensin converting enzyme 2 (ACE2) as the receptor by which it gains access into lung and other tissue. Early in the pandemic, there was speculation that a number of commonly used medications—including ibuprofen and other non-steroidal anti-inflammatory drugs (NSAIDs)—have the potential to upregulate ACE2, thereby possibly facilitating viral entry and increasing the severity of COVID-19. We investigated the influence of the NSAIDS with a range of cyclooxygenase (COX)1 and COX2 selectivity (ibuprofen, flurbiprofen, etoricoxib) and paracetamol on the level of ACE2 mRNA/protein expression and activity as well as their influence on SARS-CoV-2 infection levels in a Caco-2 cell model. We also analysed the ACE2 mRNA/protein levels and activity in lung, heart and aorta in ibuprofen treated mice. The drugs had no effect on ACE2 mRNA/protein expression and activity in the Caco-2 cell model. There was no up-regulation of ACE2 mRNA/protein expression and activity in lung, heart and aorta tissue in ibuprofen-treated mice in comparison to untreated mice. Viral load was significantly reduced by both flurbiprofen and ibuprofen at high concentrations. Ibuprofen, flurbiprofen, etoricoxib and paracetamol demonstrated no effects on ACE2 expression or activity in vitro or in vivo. Higher concentrations of ibuprofen and flurbiprofen reduced SARS-CoV-2 replication in vitro.