Adding a True 3-D Display to a Raster Graphics System

This Experimental 3-D Graphics System Can Be Added to Standard Raster Graphics Systems at Modest Expense. It Promises Much Broader Access to Effective 3-D Display.     

Characterization of IgG1 immunoglobulins and peptide-Fc fusion proteins by limited proteolysis in conjunction with LC-MS

A combinatory approach for the characterization of post-translational and chemical modifications in high molecular weight therapeutic proteins like antibodies and peptide-Fc fusion proteins (MW > or = 50 000 Da) is presented. In this approach, well-established techniques such as limited proteolysis, reversed-phase (RP) high-performance liquid chromatography (HPLC), and in-line mass spectrometry (MS) were combined for the characterization of a monoclonal IgG1 antibody and three different peptide-Fc fusion proteins. The one commonality of these molecules is the presence of a similarly accessible lysine residue either located in the flexible hinge region of the antibody or in the flexible linker of the peptide-Fc fusion proteins. Applying limited proteolysis using endoproteinase Lys-C resulted in the predominant cleavage C-terminal of this lysine residue. The created fragments, two identical Fab domain fragments and one Fc domain fragment derived from the IgG1 antibody and one Fc domain fragment and each of the three individual peptide moieties generated from the peptide-Fc fusion proteins, were readily accessible for complete separation by RP-HPLC and detailed characterization by in-line MS analysis. This approach facilitated rapid detection of a variety of chemical modifications such as methionine oxidation, disulfide bond scrambling, and reduction as well as the characterization of various carbohydrate chains. We found limited proteolysis followed by RP-HPLC-MS to be less time-consuming for sample preparation, analysis, and data interpretation than traditional peptide mapping procedures. At the same time, the reduced sample complexity provided superior chromatographic and mass spectral resolution than the analysis of the corresponding intact molecules or a large number of enzymatically generated fragments.     

Fourier transform infrared spectroscopic imaging of anisotropic poly(vinylidene fluoride) films with polarized radiation

The technique of Fourier transform infrared (FT-IR) spectroscopic imaging with focal plane array detectors has proved to be a powerful technique for rapid chemical visualization of samples with a lateral resolution up to about 10 mum. However, the potential of FT-IR imaging for the characterization of anisotropic materials can be significantly enhanced by using polarized radiation. This issue will be addressed in the present communication, which reports for the first time imaging investigations based on the FT-IR polarization spectra of poly(vinylidene fluoride) films that have been uniaxially elongated below and above the threshold temperature of the II(alpha) --> I(beta) phase transition.     

Interplay between oxygen demand reactions and kinetic gas-water transfer in porous media

Gas-water phase transfer associated with the dissolution of trapped gas in porous media is a key process that occurs during pulsed gas sparging operations in contaminated aquifers. Recently, we applied a numerical model that was experimentally validated for abiotic situations, where multi-species kinetic inter-phase mass transfer and dissolved gas transport occurred during pulsed gas penetration-dissolution events [Balcke, G.U., Meenken, S., Hoefer, C. and Oswald, S.E., 2007. Kinetic gas-water transfer and gas accumulation in porous media during pulsed oxygen sparging. Environmental Science & Technology 41(12), 4428-4434]. Here we extend the model by using a reactive term to describe dissolved oxygen demand reactions via the formation of a reaction product, and to study the effects of such an aerobic degradation process on gas-water mass transfer and dissolution of trapped gas in porous media. As a surrogate for microbial oxygen reduction, first-order oxygen demand reactions were based on the measured oxidation of alkaline pyrogallol in column experiments. This reaction allows for adjusting the rate to values close to expected biodegradation rates and detection of the reaction product. The experiments and model consistently demonstrated accelerated oxygen gas-water mass transfer with increasing oxygen demand rates associated with an influence on the partitioning of other gases. Thus, as the oxygen demand accelerates, less gas phase residues, consisting mainly of nitrogen, are observed, which is in general beneficial to the performance of field biosparging operations. Model results additionally predict how oxygen demand influences oxygen mass transfer for a range of biodegradation rates. A typical field case scenario was simulated to illustrate the observed coupling of oxygen consumption and gas bubble dissolution. The model provides a tool to improve understanding of trapped gas behavior in porous media and contributes to a model-assisted biosparging.     

Measurement of glutathione in activated sludges

Thermal, electric, mechanical or oxidative stress seem a promising way to reduce the production of excess activated sludge during biological wastewater treatment. However, the adaptation and the resistance of the sludge microbial ecosystem to stress conditions is a major question as it may definitively limit the effect of some treatments. Defence mechanisms developed by aerobic organisms, in particular, in response to oxidative stress involve various antioxidant activities and compounds such as glutathione. An HPLC method was developed for measuring reduced and total glutathione (GSH and GSHt) in perchloric acid sludge extracts. The method was sensitive, highly specific and validated for linearity, precision and recovery. Considering the extraction yield and the oxidation of GSH during extract storage, the measured GSH concentration was estimated to represent 60% of the GSH content from activated sludges. GSHt ranged from 0.32 to 3.34micromolg(-1) volatile solids and the GSH/GSHt ratio ranged from 32% to 91%. Measurements performed on sludges stressed in precise conditions selected to reach a reduction of sludge production showed a decrease of GSH and GSHt concentrations with thermal, mechanical, electric and ozone stress.     

Transition state kinetics of Hg(II) adsorption at gibbsite-water interface

Kinetics of adsorption plays a pivotal factor in determining the bio-availability and mobility of Hg(II) in the environment. The kinetics of Hg(II) adsorption on gibbsite was examined as a function of pH, temperature and electrolyte type. Adsorption of Hg(II) was highly non-linear where the rate of Hg(II) retention was rapid initially and was followed by gradual or somewhat slow retention behavior with increasing contact time. The respective rate constants designated as k(1) (S-1: fast step) and k(2) (S-2: slow step). Always k(1) follows the order: k(1)(CIO)(4) >/= k(1)(NO3)(4) > k(1)(Cl). Such a relationship was not observed for the S-2 route. A two-step reaction model with pseudo-first order kinetics successfully described the adsorption rates of Hg(II) on gibbsite. Arrhenius and Erying models determined the thermodynamic parameters at activation states, which correspond to S-1 and S-2 routes. In a given system, always the activation energies showed a decrease with the pH. Gibbs free energy (DeltaG(#)), enthalpy (DeltaH(#)), and entropy (DeltaS(#)) values of activation states were almost similar both in NaClO(4) and NaNO(3) which signal a similar Hg(II) adsorptive mechanism on gibbsite. The configurations of different Hg(II)-surface complexes were elucidated by transmission vibration spectroscopy.     

Autolysis of propionibacteria: detection of autolytic enzymes by renaturing SDS-PAGE and additional buffer studies

Five strains of propionibacteria with 70-90% autolysis in sodium lactate broth (SLB) were studied by renaturing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Several lytic bands ranging in size between 25 and 143 kDa were detected by using propionibacteria cells or cell walls as substrate in the gel. Four Propionibacterium freudenreichii strains showed similar autolytic-enzyme profiles, consisting of two autolytic bands, one with molecular mass 162 kDa and one in the range 123-143 kDa. However, the Propionibacterium acidipropionici strain showed a completely different profile, consisting of 8 autolytic bands with molecular masses of 122, 97, 71, 55, 43, 39, 31, and 25 kDa. Lytic enzymes from P. freudenreichii INF-alpha, P. freudenreichii ISU P-59, P. freudenreichii ISU P-24, and P. freudenreichii ISU P-50 showed lytic activity against cells from all these four strains, but not against P. acidipropionici ATCC 4965. However, P. acidipropionici ATCC 4965 autolysed only its own cells. Effects of pH, temperature, and ions on autolytic activity were tested by renaturing SDS-PAGE and in buffer systems. Results from the SDS-PAGE electrophoresis showed optimal autolytic activity of P. acidipropionici ATCC 4965 at 37 degrees C and in the pH range 7 to 8.5 and of P. freudenreichii ISU P-59 at 20 degrees C and in the pH range 5 to 7. The autolytic activity of P. acidipropionici ATCC 4965 was extremely heat stable (100 degrees C, 2 h), in contrast to the lytic activity of P. freudenreichii ISU P-59, which was heat labile. The autolytic activities of P. acidipropionici ATCC 4965 were inhibited by divalent cations, however, the lytic activities of P. freudenreichii ISU P-59 were activated by Mn(2+), Ca(2+), and Co(2+). In buffer, optimum autolysis of P. acidipropionici ATCC 4965 was observed at pH 8.5 and at 40 degrees C. P. freudenreichii ISU P-59 showed optimum autolysis in buffer at pH 7.5 and at 30 degrees C.