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Eight chemicals, including glycerol monolaurate, hydrogen peroxide, acetic acid, lactic acid, sodium benzoate, sodium chlorate, sodium carbonate, and sodium hydroxide, were tested individually or in combination for their ability to inactivate Campylobacter jejuni at 4 degrees C in suspension. Results showed that treatment for up to 20 min with 0.01% glycerol monolaurate, 0.1% sodium benzoate, 50 or 100 mM sodium chlorate, or 1% lactic acid did not substantially (< or = 0.5 log CFU/ml) reduce C. jejuni populations but that 0.1 and 0.2% hydrogen peroxide for 20 min reduced C. jejuni populations by ca. 2.0 and 4.5 log CFU/ml, respectively. By contrast, treatments with 0.5, 1.0, 1.5, and 2.0% acetic acid, 25, 50, and 100 mM sodium carbonate, and 0.05 and 0.1 N sodium hydroxide reduced C. jejuni populations by >5 log CFU/ml within 2 min. A combination of 0.5% acetic acid plus 0.05% potassium sorbate or 0.5% acetic acid plus 0.05% sodium benzoate reduced C. jejuni populations by >5 log CFU/ml within 1 min; however, substituting 0.5% lactic acid for 0.5% acetic acid was not effective, with a reduction of C. jejuni of <0.5 log CFU/ml. A combination of acidic calcium sulfate, lactic acid, ethanol, sodium dodecyl sulfate, and polypropylene glycol (ACS-LA) also reduced C. jejuni in suspension by >5 log CFU/ml within 1 min. All chemicals or chemical combinations for which there was a >5-log/ml reduction of C. jejuni in suspension were further evaluated for C. jejuni inactivation on chicken wings. Treatments at 4 degrees C of 2% acetic acid, 100 mM sodium carbonate, or 0.1 N sodium hydroxide for up to 45 s reduced C. jejuni populations by ca. 1.4, 1.6, or 3.5 log CFU/g, respectively. Treatment with ACS-LA at 4 degrees C for 15 s reduced C. jejuni by >5 log CFU/g to an undetectable level. The ACS-LA treatment was highly effective in chilled water at killing C. jejuni on chicken and, if recycled, may be a useful treatment in chill water tanks for poultry processors to reduce campylobacters on poultry skin after slaughter.
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PMID:Reduction of Campylobacter jejuni on chicken wings by chemical treatments. 1662 17

The organic derivatization of silicon-based nanoporous photonic crystals is presented as a method to immobilize peptides for the detection of protease enzymes in solution. A narrow-line-width rugate filter, a one-dimensional photonic crystal, is fabricated that exhibits a high-reflectivity optical resonance that is sensitive to small changes in the refractive index at the pore walls. To immobilize peptide in the pore of the photonic crystal, the hydrogen-terminated silicon surface was first modified with the alkene 10-succinimidyl undecenoate via hydrosilylation. The monolayer with the succinimide ester moiety at the distal end served the dual function of protecting the underlying silicon from oxidation as well as providing a surface suitable for subsequent derivatization with amines. The surface was further modified with 1-aminohexa(ethylene glycol) (EG(6)) to resist nonspecific adsorption of proteins common in complex biological samples. The distal hydroxyl of the EG(6) is activated using the solid-phase coupling reagent disuccinimidyl carbonate for selective immobilization of peptides as protease recognition elements. X-ray photoelectron spectroscopy analysis reveals high activation and coupling efficiency at each stage of the functionalization. Exposure of the peptide-modified crystals to the protease subtilisin in solution causes a change in the refractive index, resulting in a shift of the resonance to shorter wavelengths, indicating cleavage of organic material within the pores. The lowest detected concentration of enzyme was 37 nM (7.4 pmol in 200 microL).
ACS Nano 2007 Nov
PMID:Peptide-modified optical filters for detecting protease activity. 1920 74

Peroxynitrite is formed by the very fast reaction of nitric oxide and superoxide radicals, a reaction that kinetically competes with other routes that chemically consume or physically sequester the reagents. It can behave either as an endogenous cytotoxin toward host tissues or a cytotoxic effector molecule against invading pathogens, depending on the cellular source and pathophysiological setting. Peroxynitrite is in itself very reactive against a few specific targets that range from efficient detoxification systems, such as peroxiredoxins, to reactions eventually leading to enhanced radical formation (e.g., nitrogen dioxide and carbonate radicals), such as the reaction with carbon dioxide. Thus, the chemical biology of peroxynitrite is dictated by the chemical kinetics of its formation and decay and by the diffusion across membranes of the species involved, including peroxynitrite itself. On the other hand, most durable traces of peroxynitrite passing (such as 3-nitrotyrosine) are derived from radicals formed from peroxynitrite by routes that represent extremely low-yield processes but that have potentially critical biological consequences. Here we have reviewed the chemical kinetics of peroxynitrite as a biochemical transient species in order to estimate its rates of formation and decay and then its steady-state concentration in different intra- or extracellular compartments, trying to provide a quantitative basis for its reactivity; additionally, we have considered diffusion across membranes to locate its possible effects. Finally, we have assessed the most successful attempts to intercept peroxynitrite by pharmacological intervention in their potential to increment the existing biological defenses that routinely deal with this cytotoxin.
ACS Chem Biol 2009 Mar 20
PMID:Chemical biology of peroxynitrite: kinetics, diffusion, and radicals. 1926 56

Besides the classical atom/ion/molecule based mechanism, nonclassical crystallization provides a nanoparticle-based crystallization pathway toward single crystals. However, there is a lack of experimentally established strategies for engineering a range of crystalline microstructures from common nanoparticles by nonclassical crystallization. We demonstrate that a commercial random copolymer polyelectrolyte poly(4-styrene sulfonate)-co-(maleic acid) (PSS-co-MA) considerably guides crystallization of calcium carbonate (CC) with a high versatility. The bioinspired nonclassical crystallization protocol yielded a series of calcite microstructures. Calcite single crystals obtained at low supersaturation show a pseudo-dodecahedral shape with curved faces, whereas increasing supersaturation generated calcite mesocrystals with pseudo-octahedral shapes and scalloped surfaces. Further increase of supersaturation induced the formation of polycrystalline multilayered and hollow spheres. In the initial growth stage of all these microstructures, amorphous CC nanoparticles formed as the early product. Remarkably, microparticles with minimal primitive (P)-surface were captured as the prominent intermediate indicative of liquidlike behavior. Moreover, nanogranular structures exist broadly in the as-synthesized crystals. These results demonstrate that the polyelectrolyte can effectively stabilize the amorphous CC nanoparticle precursors, impart control over the evolution from amorphous precursors via a liquid aggregate through P-surface intermediates to the final crystals, and thus allow the morphogenesis. Simple variation of calcium and polyeletrolyte concentrations enables a systematic control over the size and morphology of particles among pseudo-dodecahedra, pseudo-octahedra, multilayered spheres, and hollow spheres, which are expressed in a morphology diagram. A unifying nanoparticle aggregation formation mechanism was suggested to explain the morphogenesis by the combination of nonclassical crystallization and surface area minimization principles.
ACS Nano 2009 Jul 28
PMID:Polyelectrolyte-directed nanoparticle aggregation: systematic morphogenesis of calcium carbonate by nonclassical crystallization. 1957 17

Graphite oxide was exfoliated and dispersed in propylene carbonate (PC) by bath sonication. Heating the graphene oxide suspensions at 150 degrees C significantly reduced the graphene oxide platelets; paper samples comprising such reduced graphene oxide platelets had an electrical conductivity of 5230 S/m. By adding tetraethylammonium tetrafluoroborate (TEA BF(4)) to the reduced graphene oxide/PC slurry and making a two-cell ultracapacitor, specific capacitance values of about 120 F/g were obtained.
ACS Nano 2010 Feb 23
PMID:Exfoliation of graphite oxide in propylene carbonate and thermal reduction of the resulting graphene oxide platelets. 2011 29

Mineral-coated microspheres were prepared via a bioinspired, heterogeneous nucleation process at physiological temperature. Poly(d,l-lactide-co-glycolide) (PLG) microspheres were fabricated via a water-in-oil-in-water emulsion method and were mineral-coated via incubation in a modified simulated body fluid (mSBF). X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy with associated energy-dispersive X-ray spectroscopy confirmed the presence of a continuous mineral coating on the microspheres. The mineral grown on the PLG microsphere surface has characteristics analogous to those of bone mineral (termed "bonelike" mineral), with a carbonate-containing hydroxyapatite phase and a porous structure of platelike crystals at the nanometer scale. The assembly of mineral-coated microspheres into aggregates was observed when microsphere concentrations above 0.50 mg/mL were incubated in mSBF for 7 days, and the size of the aggregates was dependent on the microsphere concentration in solution. In vitro mineral dissolution studies performed in Tris-buffered saline confirmed that the mineral formed was resorbable. A surfactant additive (Tween 20) was incorporated into mSBF to gain insight into the mineral growth process, and Tween 20 not only prevented aggregation but also significantly inhibited mineral formation and influenced the characteristics of the mineral formed on the surface of PLG microspheres. Taken together, these findings indicate that mineral-coated PLG microspheres or mineral-coated microsphere aggregates can be synthesized in a controllable manner using a bioinspired process. These materials may be useful in a range of applications, including controlled drug delivery and biomolecule purification.
ACS Appl Mater Interfaces 2009 Jul
PMID:Growth of hydroxyapatite coatings on biodegradable polymer microspheres. 2016 78

A series of poly(arylene ethynylene) conjugated polyelectrolytes (CPEs) substituted with carboxylic acid side groups have been synthesized and characterized. The polymers feature a backbone consisting of a carboxylated dialkoxyphenylene-1,4-ethynylene unit alternating with a second arylene ethynylene moiety of variable electron demand. The HOMO-LUMO gap is varied across the series, giving rise to a set of four polymers that have absorption maxima ranging from 404 to 495 nm. The CPEs adsorb effectively from solution onto nanostructured TiO(2) films, giving rise to TiO(2)/CPE films that absorb approximately 90% of the incident light at the absorption band maximum. The photocurrent generation efficiency of the TiO(2)/CPE films was examined in a solar cell configuration using an I(3)(-)/I(-) propylene carbonate electrolyte and a Pt/fluorine-doped tin oxide counter electrode. Most of the films exhibit good photocurrent generation efficiency with a peak quantum efficiency of approximately 50% at wavelengths corresponding to the polymers' absorption band maximum. Interestingly, the photocurrent generation efficiency for the lowest-band-gap polymer is substantially lower compared to the other three systems. This effect is attributed to efficient nonradiative decay of excitons at trap sites arising from interchain contacts distal from the TiO(2)/CPE interface.
ACS Appl Mater Interfaces 2009 Feb
PMID:Variable-band-gap poly(arylene ethynylene) conjugated polyelectrolytes adsorbed on nanocrystalline TiO(2): photocurrent efficiency as a function of the band gap. 2035 27

Three-dimensional chitosan self-assembled nanostructures are reported whose morphology can be adjusted by tuning of the processing parameters, including the rate of solvent removal, the surface roughness of the substrate, and the polarity of the solvent used. Upon this, chitosan nanostructures of more interesting morphology and even higher complexity can be prepared, which can serve as nanotemplates for subsequent biomineralization of calcium carbonate, leading to controllable three-dimensional biominerals having the same complex morphology as that exhibited by the self-assembled chitosan nanotemplates.
ACS Appl Mater Interfaces 2009 Jan
PMID:Self-assembled chitosan nanotemplates for biomineralization of controlled calcite nanoarchitectures. 2035 47

Dissolution of biologically important sparingly soluble salts, such as calcium carbonate and calcium oxalate, is possible by use of carboxyl- and carboxyl/phosphonate-bearing, anionic additives, citrate, malate, carboxyphosphonate, and butane tetracarboxylate. Calcium-containing dissolution products have been identified, characterized, and independently synthesized. These are polymeric materials composed of calcium and the additive as the ligand. Their full characterization was carried out by single-crystal X-ray crystallography and other techniques.
ACS Appl Mater Interfaces 2009 Jan
PMID:Novel calcium carboxyphosphonate/polycarboxylate inorganic-organic hybrid materials from demineralization of calcitic biomineral surfaces. 2035 49

Poly(propylene carbonate) (PPC), a polymer produced from CO2, has been melt-mixed with 30 wt % poly(methyl methacrylate) (PMMA) with the aim of enhancing the physical properties of PPC for practical use but keeping a relatively high CO2 fixing rate in the compound. The observation of a coarse phase structure with a large PMMA domain size and a large size distribution in the blend indicates the immiscibility between PPC and PMMA. The addition of a small amount of poly(vinyl acetate) (PVAc) not only shifts the glass transition temperatures (T(g)'s) of both PPC and PMMA markedly but also significantly increases the modulus and tensile strength of the blend. The prepared compound with 5 per hundred parts of resin PVAc shows a 26 times higher elastic modulus and an approximately 3.8 times higher tensile strength than pure PPC at room temperature. The morphological investigation indicates that the incorporation to PVAC not only induces the finer dispersion of PMMA in the PPC matrix but also results in the phase transformation from a sea-island to a co-continuous structure.
ACS Appl Mater Interfaces 2009 Aug
PMID:Compatibilization by homopolymer: significant improvements in the modulus and tensile strength of PPC/PMMA blends by the addition of a small amount of PVAc. 2035 79


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