Ultrasonic spectroscopy study of relaxation and scattering in whey protein solutions

Ultrasonic attenuation spectroscopy was used to investigate the influence of pH on fast chemical reactions and aggregation of whey proteins in aqueous solution. Ultrasonic attenuation spectra (1–100 MHz) of 2.5 wt% aqueous solutions containing either ‘native’ or ‘alkali-denatured’ proteins were measured as a function of pH (2–12). Peaks in the attenuation occurred at pH 2.8 and 11.6 due to proton transfer equilibria, ie  CO₂H ↔  CO₂⁻ + H⁺ and  NH₂ + H⁺ ↔  NH₃⁺ respectively. Attenuation at other pH values was attributed to a hydration relaxation mechanism. Relaxation times for the equilibria were of the order of 10⁻⁸ s. There was an additional attenuation peak at the isoelectric point of the proteins (pH 5) for solutions containing ‘alkali-denatured’ protein, which was due to scattering of ultrasound by aggregated proteins. The particle size distribution of the aggregates could be determined using ultrasonic scattering theory to analyse the attenuation spectra. Ultrasonic spectroscopy is an extremely valuable tool for probing the molecular characteristics of proteins in solution. © 1999 Society of Chemical Industry     

Biotic and abiotic interactions in aquatic microcosms determine fate and toxicity of Ag nanoparticles: part 2-toxicity and Ag speciation

To study the effects of complex environmental media on silver nanoparticle (AgNP) toxicity, AgNPs were added to microcosms with freshwater sediments and two species of aquatic plants (Potamogeton diversifolius and Egeria densa), followed by toxicity testing with microcosm surface water. Microcosms were designed with four environmental matrices in order to determine the contribution of each environmental compartment to changes in toxicity: water only (W), water + sediment (WS), water + plants (WP), and water + plants + sediment (WPS). Silver treatments included AgNPs with two different coatings, gum arabic (GA-AgNPs) or polyvinylpyrollidone (PVP-AgNPs), as well as AgNO(3). Water samples taken from the microcosms at 24 h postdosing were used in acute toxicity tests with two standard model organisms, early life stage zebrafish (Danio rerio) and Daphnia magna. Speciation of Ag in these samples was analyzed using Ag L3-edge X-ray absorption near edge spectroscopy (XANES). Silver speciation patterns for the nanoparticle treatments varied significantly by coating type. While PVP-AgNPs were quite stable and resisted transformation across all matrices (>92.4% Ag(0)), GA-AgNP speciation patterns suggest significantly higher transformation rates, especially in treatments with plants (<69.2% and <58.8% Ag(0) in WP and WPS, respectively) and moderately increased transformation with sediments (<85.6% Ag(0)). Additionally, the presence of plants in the microcosms (with and without sediments) reduced both the concentration of Ag in the water column and toxicity for all Ag treatments. Reductions in toxicity may have been related to decreased water column concentrations as well as changes in the surface chemistry of the particles induced by organic substances released from the plants.     

Spatial and temporal distribution of singlet oxygen in Lake Superior

A multiyear field study was undertaken on Lake Superior to investigate singlet oxygen ((1)O(2)) photoproduction. Specifically, trends within the lake were examined, along with an assessment of whether correlations existed between chromophoric dissolved organic matter (CDOM) characteristics and (1)O(2) production rates and quantum yields. Quantum yield values were determined and used to estimate noontime surface (1)O(2) steady-state concentrations ([(1)O(2)](ss)). Samples were subdivided into three categories based on their absorbance properties (a300): riverine, river-impacted, or open lake sites. Using calculated surface [(1)O(2)](ss), photochemical half-lives under continuous summer sunlight were calculated for cimetidine, a pharmaceutical whose reaction with (1)O(2) has been established, to be on the order of hours, days, and a week for the riverine, river-impacted, and open lake waters, respectively. Of the CDOM properties investigated, it was found that dissolved organic carbon (DOC) and a300 were the best parameters for predicting production rates of [(1)O(2)](ss). For example, given the correlations found, one could predict [(1)O(2)](ss) within a factor of 4 using a300 alone. Changes in the quantum efficiency of (1)O(2) production upon dilution of river water samples with lake water samples demonstrated that the CDOM found in the open lake is not simply diluted riverine organic matter. The open lake pool was characterized by low absorption coefficient, low fluorescence, and low DOC, but more highly efficient (1)O(2) production and predominates the Lake Superior system spatially. This study establishes that parameters that reflect the quantity of CDOM (e.g., a300 and DOC) correlate with (1)O(2) production rates, while parameters that characterize the absorbance spectrum (e.g., spectral slope coefficient and E2:E3) correlate with (1)O(2) production quantum yields.     

Myeloid-Derived Suppressor Cells Gain Suppressive Function during Neonatal Bacterial Sepsis

Neonates are at an increased risk of an infectious disease. This is consistent with an increased abundance of myeloid-derived suppressor cells (MDSCs) compared with older children and adults. Using a murine model of neonatal bacterial sepsis, we demonstrate that MDSCs modulate their activity during an infection to enhance immune suppressive functions. A gene expression analysis shows that MDSCs increased NOS2, Arg-1 and IL-27p28 expression in vitro and in vivo in response to Escherichia coli O1:K1:H7 and this is regulated at the level of the gene expression. Changes in the effector gene expression are consistent with increased enzymatic activity and cytokine secretion. The neonatal MDSCs express toll-like receptor (TLR) 2, 4 and 5 capable of recognizing pathogen-associated molecular patterns (PAMPS) on E. coli. However, a variable level of effector expression was achieved in response to LPS, peptidoglycan or flagellin. Individual bacterial PAMPs did not stimulate the expression of Arg-l and IL-27p28 equivalently to E. coli. However, the upregulation of NOS2 was achieved in response to LPS, peptidoglycan and flagella. The increased immune suppressive profile translated to an enhanced suppression of CD4+ T cell proliferation. Collectively, these findings increase our understanding of the dynamic nature of MDSC activity and suggest that these cells abundant in early life can acquire activity during an infection that suppresses protective immunity.     

Shear Retrofit of Flared RC Bridge Columns Subjected to Earthquakes

This paper presents an evaluation of the seismic performance and retrofit of reinforced-concrete bridge columns with structural flares. Experimental and analytical studies were performed on four 40%-scale specimens. Two specimens represented the as-built columns, while the other two were retrofitted with steel jackets for shear capacity enhancement. The results indicate that some of the existing methods for evaluating the shear capacity of columns can be unconservative and could overestimate the shear capacity of the columns included in this study by 60%. It is also shown that by implementing proper detailing, steel jackets can be used to enhance the shear capacity and ductility of flared columns with no appreciable increase in the shear demand.     

Fluorescent dye encapsulated ZnO particles with cell-specific toxicity for potential use in biomedical applications

Fluorescein isothiocyanate (FITC)-encapsulated SiO₂ core-shell particles with a nanoscale ZnO finishing layer have been synthesized for the first time as multifunctional “smart” nanostructures. Detailed characterization studies confirmed the formation of an outer ZnO layer on the SiO₂–FITC core. These ~200 nm sized particles showed promise toward cell imaging and cellular uptake studies using the bacterium Escherichia coli and Jurkat cancer cells, respectively. The FITC encapsulated ZnO particles demonstrated excellent selectivity in preferentially killing Jurkat cancer cells with minimal toxicity to normal primary immune cells (18% and 75% viability remaining, respectively, after exposure to 60 μg/ml) and inhibited the growth of both gram-positive and gram-negative bacteria at concentrations ≥250–500 μg/ml (for Staphylococcus aureus and Escherichia coli, respectively). These results indicate that the novel FITC encapsulated multifunctional particles with nanoscale ZnO surface layer can be used as smart nanostructures for particle tracking, cell imaging, antibacterial treatments and cancer therapy.     

Gander's distance from the nest as a function of the goose's incubation period in Canada geese (Branta canadensis maxima).

The purpose of this study was to determine if a gander's distance from its mate's nest changed as a function of the goose's incubation period. The subjects were a captive flock of wild giant Canada geese (Branta canadensis maxima). Ganders' distance from their mates' nests was recorded daily at 4 randomly selected times. A daily mean was calculated from the 4 daily distance measurements. The results of this study indicated that the ganders' distance from their mates' nests remained constant over the incubation period but decreased significantly on the day that goslings hatched. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence that the Wiskott-Aldrich syndrome protein may be involved in lymphoid cell signaling pathways

Wiskott-Aldrich syndrome is an X-linked combined immunodeficiency affecting cells of several different hemopoietic lineages. The Wiskott-Aldrich syndrome protein (WASP), which has no homology with any other known protein families, is rich in proline motifs known to contribute to Src homology 3 binding sites. However, its function has not been determined. The Tec family of cytoplasmic tyrosine kinases, which include Btk (the X-linked agammaglobulinemia gene), Itk, and Tec, is thought to be involved in lymphoid cell signaling pathways. In this work, we show binding of WASP to the Src homology 3 domains of Btk, Itk, Tec, Grb2, and phospholipase C-gamma, which suggests a function for WASP in lymphoid cell signaling.     

High resolution solid state C n.m.r. of Canadian peats

Peat samples from three locations in Quebec, Canada, were characterized by ¹³C CP/MAS n.m.r. spectroscopy. The n.m.r. analysis indicates that the peats contain a significant amount of unaltered plant components including cellulose, hemicellulose, lignin, waxes and resins. Integration of specific regions of the spectra can give semi-quantitative estimates of some of these plant components and, in limited cases, information about the degree of decomposition can be obtained from the ¹³C CP/MAS n.m.r. spectrum. Dipolar dephasing experiments and difference spectroscopy were found to be valuable techniques for spectra assignments and enhancement of compositional differences.