Long residence times of soil organic matter have been attributed to reactive mineral surface sites that sorb organic species and cause inaccessibility due to physical isolation and chemical ...stabilization at the organic-mineral interface. Instrumentation for probing this interface is limited. As a result, much of the micron- and molecular-scale knowledge about organic-mineral interactions remains largely qualitative. Here we report the use of force spectroscopy to directly measure the binding between organic ligands with known chemical functionalities and soil minerals in aqueous environments. By systematically studying the role of organic functional group chemistry with model minerals, we demonstrate that chemistry of both the organic ligand and mineral contribute to values of binding free energy and that changes in pH and ionic strength produce significant differences in binding energies. These direct measurements of molecular binding provide mechanistic insights into organo-mineral interactions, which could potentially inform land-carbon models that explicitly include mineral-bound C pools.Most molecular scale knowledge on soil organo-mineral interactions remains qualitative due to instrument limitations. Here, the authors use force spectroscopy to directly measure free binding energy between organic ligands and minerals and find that both chemistry and environmental conditions affect binding.
Here we report radiation-induced formation of Ce( iii ) nanostructures in an in situ liquid cell for the transmission electron microscope (TEM). Small (<5 nm) irregular Ce(OH) 3 nanoparticles were ...identified as the final products from cerium( iii ) nitrate solutions of initial pH 5.2. Pourbaix diagrams show that solid Ce(OH) 3 can only exist above pH 10.4, whereas at lower pH values, Ce( iii ) should remain soluble as aqueous Ce 3+ . Reduction of Ce 3+ to zerovalent Ce by aqueous electrons followed by hydrolysis is a plausible catalytic mechanism for generating hydroxide. Numerical simulations support that radiolysis of cerium nitrate solutions may lead to pH increases, in contrast to well-known acidification of pure water. Compared to previous radiolytic synthesis routes in aqueous solution for other metal or metal oxide nanoparticles, based on metal ion reduction, for example, the chemical pathways leading to these Ce( iii ) nanostructures require an increase in the local pH to alkaline conditions where Ce(OH) 3 can exist. These results extend the range of chemical conditions that can be induced by radiolysis to form oxidized nanostructures from solution.
An overview of acoustic wave sensor arrays for gas-phase chemistry is presented, with emphasis on such issues as interaction mechanisms, chemical diversity, coating selection approaches, array ...design, and multivariate data analysis.
Glucose oxidase immobilized in mesocellular carbon foam results in a highly sensitive and fast glucose biosensor. The structure of the mesocellular foam (see Figure), with a combination of mesopores ...containing the glucose oxidase (GOx) enzymes and micropores and transport channels, results in high enzyme loading and low mass‐transfer limitations, producing higher catalytic activity and sensitivity than polymer‐matrix‐based GOx glucose sensors.
Nanobiocatalysis, in which enzymes are incorporated into nanostructured materials, has emerged as a rapidly growing area. Nanostructures, including nanoporous media, nanofibers, carbon nanotubes and ...nanoparticles, have manifested great efficiency in the manipulation of the nanoscale environment of the enzyme and thus promise exciting advances in many areas of enzyme technology. This review will describe these recent developments in nanobiocatalysis and their potential applications in various fields, such as trypsin digestion in proteomic analysis, antifouling, and biofuel cells.
In the original version of this Article, the Acknowledgements section omitted the Department of Energy-funded Environmental and Molecular Sciences Laboratory in which the XRD measurements were ...performed. This error has now been corrected in both the PDF and HTML versions of the Article.
Nanostructures for enzyme stabilization Kim, Jungbae; Grate, Jay W.; Wang, Ping
Chemical engineering science,
02/2006, Letnik:
61, Številka:
3
Journal Article
Recenzirano
Recent breakthroughs in nanotechnology have made various nanostructured materials more affordable for a broader range of applications. Although we are still at the beginning of exploring the use of ...these materials for biocatalysis, various nanostructures have been examined as hosts for enzyme immobilization via approaches including enzyme adsorption, covalent attachment, enzyme encapsulation, and sophisticated combinations of methods. This review discusses the stabilization mechanisms behind these diverse approaches; such as confinement, pore size and volume, charge interaction, hydrophobic interaction, and multipoint attachment. In particular, we will review recently reported approaches to improve the enzyme stability in various nanostructures such as nanoparticles, nanofibers, mesoporous materials, and single enzyme nanoparticles (SENs). In the form of SENs, each enzyme molecule is surrounded with a nanometer scale network, resulting in stabilization of enzyme activity without any serious limitation for the substrate transfer from solution to the active site. SENs can be further immobilized into mesoporous silica with a large surface area, providing a hierarchical approach for stable, immobilized enzyme systems for various applications, such as bioconversion, bioremediation, and biosensors.
We present Solvent Immersion Imprint Lithography (SIIL), a technique for polymer functionalization and microsystem prototyping. SIIL is based on polymer immersion in commonly available solvents. This ...was experimentally and computationally analyzed, uniquely enabling two practical aspects. The first is imprinting and bonding deep features that span the 1 to 100 μm range, which are unattainable with existing solvent-based methods. The second is a functionalization scheme characterized by a well-controlled, 3D distribution of chemical moieties. SIIL is validated by developing microfluidics with embedded 3D oxygen sensors and microbioreactors for quantitative metabolic studies of a thermophile anaerobe microbial culture. Polystyrene (PS) was employed in the aforementioned applications; however all soluble polymers - including inorganic ones - can be employed with SIIL under no instrumentation requirements and typical processing times of less than two minutes.
Plastic dielectric materials are required in radiation and rare event physics detectors as structural parts, insulators, seals, light reflectors, and in connectors. In order to observe events of ...interest rather than counting the radioactivity of the detector itself, these materials must be of high radiopurity. Using a mass spectrometric method, a number of solid plastic materials and parts were analyzed for mass levels of contaminants 232Th and 238U, which were used as an assessment of radiopurity. Sample preparation began with dry ashing the solid subsamples in very low mass containers of ultra low background electroformed copper (ULB EF-Cu) foil that had been cut and folded into boats serving as crucibles. Final determinations were carried out by inductively coupled plasma mass spectrometry (ICP-MS) with liquid nebulization sample solution introduction. Sample sizes were in the 25 mg to 1.25 g mass, and analyses could be completed in less than two days. Detection limits to pg/g (i.e, parts per trillion) levels are obtained and converted to radioactivity units μBq/kg of material. Determinations on poly(methyl methacrylate) (PMMA) gave values for 238U below 10 μBq/kg, while values for poly(chlorotrifluoroethylene) (PCTFE) rod stock material or acid-leached machined PCTFE parts were at or below 50 μBq/kg in 238U. Results for solid Purad poly(vinylidene fluoride) (PVDF) material are also reported at ca 5 mBq/kg of 238U, although PVDF Solef 1010 raw material in powder and pellet form has been previously reported as low as 25 μBq/kg, and 200 μBq/kg 238U, respectively. An analysis of a polyetherimide (PEI) material, sold as ULTEM, indicated promising radiopurity with a found value of 30 μBq/kg for 238U. A variety of solid dielectric polymer materials were found with radiopurities at less than a mBq/kg 238U and 232Th.
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