Atomistic Details of Chymotrypsin Conformational Changes upon Adsorption on Silica.

Adsorption of enzymes on solid surfaces may lead to conformational changes that reduce their catalytic conversion activity and are thus detrimental to the efficiency of biotechnology or biosensing applications. This work is a joint theoretical and experimental endeavor in which we identify and quantify the conformational changes that chymotrypsin undergoes when in contact with the surface of amorphous silica nanoparticles. For this purpose, we use circular dichroism spectroscopy, standard molecular dynamics, and advanced-sampling methods.

Label-free determination of adenosine and mercury ions according to force mapping-based force-to-color variety.

Single molecule force spectroscopy based on atomic force microscopy (AFM) is a simple and sensitive technique to probe molecular recognition forces. Here we demonstrate that visual color-intensity analysis of single molecule force mapping (SMFM) can be employed as a quick and convenient force-to-color detection towards the presence of various dissolved analytes in very low concentrations. To achieve this aim, analyte-specific single-strand DNA aptamers are first bound to an AFM tip.

Interactions at the Silica-Peptide Interface: Influence of the Extent of Functionalization on the Conformational Ensemble.

In this contribution, the effect of silica particle size (28 and 210 nm) and surface chemistry (i.e., hydroxyl, methyl, or amino groups) on peptide binding response is studied with a specific emphasis on the effect of the extent of functionalization on binding.

An air-breathing enzymatic cathode with extended lifetime by continuous laccase supply.

We present a novel concept of an air-breathing enzymatic biofuel cell cathode combined with continuous supply of unpurified laccase-containing supernatant of the white-rot fungus Trametes versicolor for extended lifetime. The air-breathing cathode design obviates the need for energy-intensive active aeration. In a corresponding long-term experiment at a constant current density of 50 µA cm, we demonstrated an increased lifetime of 33 days (cathode potential above 0.

Effects of wastewater constituents and operational conditions on the composition and dynamics of anodic microbial communities in bioelectrochemical systems.

Over the last decade, there has been an ever-growing interest in bioelectrochemical systems (BES) as a sustainable technology enabling simultaneous wastewater treatment and biological production of, e.g. electricity, hydrogen, and further commodities.

Simultaneous use of a crossflow filtration membrane as microbial fuel cell anode - Permeate flow leads to 4-fold increased current densities.

A new concept for the combination of membrane bioreactors and microbial fuel cells is introduced, that aims at the production of electricity for reducing the overall energy consumption of wastewater treatment. In contrast to previous approaches, the anode is integrated as microfiltration membrane in sidestream crossflow configuration. Using a stainless steel filtration membrane with G.

Anchoring of Iron Oxyhydroxide Clusters at H and L Ferritin Subunits.

Ferritin (Fn) proteins or their isolated subunits can be used as biomolecular templates for the selectively heterogeneous nucleation and growth of nanoparticles, in particular of iron oxyhydroxides. To shed light on the atomistic mechanisms of ferritin-promoted mineralization, in this study we perform molecular dynamics simulations to investigate the anchoring sites for Fe(III) clusters on Fn subunit assemblies using models of goethite and ferrihydrite nanoparticles. For this aim, we develop and parametrize a classical force field for Fe(III) oxyhydroxides based on reference density functional theory calculations.

Recent Advances in Nanoporous Membranes for Water Purification.

Nanoporous materials exhibit wide applications in the fields of electrocatalysis, nanodevice fabrication, energy, and environmental science, as well as analytical science. In this review, we present a summary of recent studies on nanoporous membranes for water purification application. The types and fabrication strategies of various nanoporous membranes are first introduced, and then the fabricated nanoporous membranes for removing various water pollutants, such as salt, metallic ions, anions, nanoparticles, organic chemicals, and biological substrates, are demonstrated and discussed.

Membrane partitioning of ionic liquid cations, anions and ion pairs - Estimating the bioconcentration potential of organic ions.

Recent efforts have been directed towards better understanding the persistency and toxicity of ionic liquids (ILs) in the context of the "benign-by-design" approach, but the assessment of their bioaccumulation potential remains neglected. This paper reports the experimental membrane partitioning of IL cations (imidazolium, pyridinium, pyrrolidinium, phosphonium), anions ([C(CN)], [B(CN)], [FSO)N], [(CF)PF], [(CFSO)N]) and their combinations as a measure for estimating the bioconcentration factor (BCF). Both cations and anions can have a strong affinity for phosphatidylcholine bilayers, which is mainly driven by the hydrophobicity of the ions.

Variability of Zinc Oxide Dissolution Rates.

Zinc oxide (ZnO) is of widespread use for numerous applications, including many in the cosmetic industry. Thus, ZnO particles are quite likely to enter the environment. ZnO may be harmful because of the release of cytotoxic Zn ions during dissolution reactions.

Mixture toxicity of flubendazole and fenbendazole to Daphnia magna.

Nowadays, residual amounts of many pharmaceuticals can be found in various environmental compartments including surface and ground waters, soils and sediments as well as biota. Even though they undergo degradability, their environmental discharge is relatively continuous, thus they may be regarded as quasi-persistent contaminants, and are also frequently regarded as emerging organic pollutants. Benzimidazoles, especially flubendazole (FLU) and fenbendazole (FEN), represent two anthelmintic drugs belonging to this group.

Influence of geometry and material of insulating posts on particle trapping using positive dielectrophoresis.

Insulator-based dielectrophoresis (iDEP) is a powerful particle analysis technique based on electric field scattering at material boundaries which can be used, for example, for particle filtration or to achieve chromatographic separation. Typical devices consist of microchannels containing an array of posts but large scale application was also successfully tested. Distribution and magnitude of the generated field gradients and thus the possibility to trap particles depends apart from the applied field strength on the material combination between post and surrounding medium and on the boundary shape.

Consequences of a Chronic Exposure of Cultured Brain Astrocytes to the Anti-Retroviral Drug Efavirenz and its Primary Metabolite 8-Hydroxy Efavirenz.

Efavirenz is a widely prescribed non-nucleoside reverse transcriptase inhibitor for the treatment of HIV infections. To test for potential long-term consequences of efavirenz on brain cells, cultured primary astrocytes were incubated with this substance or with its primary metabolite 8-hydroxy efavirenz for up to 7 days. Both, efavirenz and 8-hydroxy efavirenz caused time- and concentration-dependent cell toxicity and stimulated in subtoxic concentrations the glycolytic flux (glucose consumption and lactate release) in astrocytes.

Irreversible Damage of Polymer Membranes During Attenuated Total Reflection Infrared Analysis.

Analyzing polymer membranes by attenuated total reflection infrared spectroscopy (ATR-IR) can lead to irreversible damage to the material and induces systematic errors in the data. Attenuated total reflection infrared spectroscopy is a common tool for analyzing the surface of polymer membranes. In order to provide sufficient contact between the membrane and the internal reflection element (i.

Applying Alkyl-Chain Surface Functionalizations in Mesoporous Inorganic Structures: Their Impact on Gas Flow and Selectivity Depending on Temperature.

Porous inorganic capillary membranes are prepared to serve as model structures for the experimental investigation of the gas transport in functionalized mesopores. The porous structures possess a mean pore diameter of 23 nm which is slightly reduced to 20 nm after immobilizing C-alkyl chains on the surface. Gas permeation measurements are performed at temperatures ranging from 0 to 80 °C using Ar, N, and CO.

A novel aptasensor based on single-molecule force spectroscopy for highly sensitive detection of mercury ions.

We have developed a novel aptasensor based on single-molecule force spectroscopy (SMFS) capable of detecting mercury ions (Hg(2+)) with sub-nM sensitivity. The single-strand (ss) DNA aptamer used in this work is rich in thymine (T) and readily forms T-Hg(2+)-T complexes in the presence of Hg(2+). The aptamer was conjugated to an atomic force microscope (AFM) probe, and the adhesion force between the probe and a flat graphite surface was measured by single-molecule force spectroscopy (SMFS).

Selective covalent immobilization of ferritin on alumina.

Selective and specific covalent immobilization and simultaneous suppression of nonspecific adsorption of the protein ferritin (FN) on the surfaces of polycrystalline α-alumina colloidal particles and single α-alumina crystals is demonstrated. FN immobilization is obtained by using a classical immobilization route and by combining either the organic silane 3-(triethoxysilyl)propylsuccinic anhydride (TESPSA) or (3-aminopropyl)triethoxysilane (APTES) with the zero-length cross linking system N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS). The combination of APTES or TESPSA with EDC/NHS leads to a stable FN binding via amide bonds.

Label-free sensing of adenosine based on force variations induced by molecular recognition.

We demonstrate a simple force-based label-free strategy for the highly sensitive sensing of adenosine. An adenosine ssDNA aptamer was bound onto an atomic force microscopy (AFM) probe by covalent modification, and the molecular-interface adsorption force between the aptamer and a flat graphite surface was measured by single-molecule force spectroscopy (SMFS). In the presence of adenosine, the molecular recognition between adenosine and the aptamer resulted in the formation of a folded, hairpin-like DNA structure and hence caused a variation of the adsorption force at the graphite/water interface.

Adaptation of the Daphnia sp. acute toxicity test: miniaturization and prolongation for the testing of nanomaterials.

Manufacturing of nanomaterials (NMs) is often complex and expensive, and their environmental risks are poorly understood or even unknown. An economization of testing NMs is therefore desirable, which can be achieved by miniaturizing test systems. However, the downsizing of test vessels and volumes can enlarge the surface/volume ratio (SVR) which in turn can affect the bioavailable concentration of adsorbing substances like NMs.