The significance of hydrolase cascades on poly(aspartic) acid biodegradation assessment.

Effect of pH and temperature upon self-assembling process between poly(aspartic acid) and Pluronic F127

The antifoam agent DOW Corning Q2-3183A will be added to waste streams in the Hanford River Protection Program-Waste Treatment and Immobilization Plant (RPP-WTP) to prevent foaming. It consists mostly of polydimethylsiloxane (PDMS) and polypropylene glycol (PPG). These and other minor constituents of the antifoam have organic constituents that may participate in radiolytic and chemical reactions that produce hydrogen in Hanford waste. It has been recommended by The WTP R&T Department recommended personnel to treat the organic compounds of the antifoam like the in a similar manner as other organic compounds that are native to the Hanford waste with respect to hydrogen production. This testing has investigated the radiolytic and thermal production of hydrogen from antifoam added to simulant waste solutions to determine if the organic components of the antifoam produce hydrogen in the same manner as the native organic species in Hanford waste. Antifoam additions for this testing were in the range of 4 to 10 wt% to ensure adequate hydrogen detection. Test conditions were selected to bound exposures to the antifoam agent in the WTP. These levels are higher than previously recommended values of 350 mg/L for actual applications in WTP tanks containing air spargers and pulse jet mixers. Limited degradation analyses for the organic components of the antifoam were investigated in this study. A more detailed study involving analyses of antifoam degradation and product formation is in progress at SRNL and results from that study will be reported at a later time. The total organic carbon (TOC) content of the Q2-3183A antifoam was measured to be 39.7 {+-} 4.9 wt% TOC. This measurement was performed in triplicate with on three different dilutions of the pure antifoam liquid using a TOC combustion analyzer instrument with catalytic oxidation, followed by CO{sub 2} quantification using an infrared detector. Test results from this study indicate that the WTP HGR correlation conservatively bounds hydrogen generation rates (HGRs) from antifoam-containing simulants if the antifoam organic components are treated the same as other native organics. Tests that used the combination of radiolysis and thermolysis conducted on simulants containing antifoam produced measured hydrogen that was bounded by the WTP correlation. These tests used the bounding WTP temperature of 90 C and a dose rate of 1.8 x 10{sup 5} rad/hr. This dose rate is about ten times higher than the dose rate equivalent calculated for a bounding Hanford sludge slurry composition of 10 Ci/L, or 2 x 10{sup 4} rad/hr. Hydrogen was measured using a quadrupole mass spectroscopy instrument. Based on the analyses from the 4wt% and 10wt% antifoam samples, it is expected that the HGR results are directly proportional to the antifoam concentration added. A native organic-containing simulant that did not contain any added antifoam also produced a measurable radiolytic/thermal hydrogen rates that was in bounded by the WTP correlation. A base simulant with no added organic produced a measurable radiolytic/thermal HGR that was {approx}2X higher than the predicted HGR. Analysis of antifoam-containing simulants after prolonged irradiation of 52 Mrad and heating (23 days at 90 C) indicates that essentially all of the PDMS and greater than 60% of the PPG components are degraded, likely to lower molecular weight species. The antifoam components were analyzed by extraction from the salt simulants, followed by gel permeation chromatography (GPC) by personnel at Dow Corning. A more detailed study of the antifoam degradation and product formation from radiolysis and thermolysis is currently in progress at SRNL. That study uses a dose rate of about 2 x 10{sup 4} rad/hr and bounding temperatures of 90 C. Results from that study will be reported in a future report.

PC와 SAN 사이의 계면장력 및 친화도에 미치는 저분자량 성분의 영향을 알아보기 위하여 용매 추출법으로 각 고분자에서 저분자량 성분을 추출하였다. GPC(gel permeation chromatography)로 분자량 분포를 확인한 결과, 각 고분자의 저분자량 성분은 용매 추출법에 의해 효과적으로 제거된 것을 확인하였다. 저분자량 성분이 제거된 고분자를 이용하여 계면장력 및 형태학 분석 결과, 저분자량 성분이 제거된 PC와 SAN은 계면장력이 높아졌고 친화도가 떨어진 것을 확인할 수 있었다. 즉 저분자량 성분이 두 고분자 사이에 상용화제와 같은 역할을 하는 것을 알 수 있었다. 두 고분자 중 SAN의 저분자량 성분이 PC의 저분자량 성분보다 상용화 효과에 더 많이 기여하는 것을 확인하였고, 이로서 PC/ABS 제조 시 저분자량 성분이 많이 포함된 SAN을 사용하는 것이 더 유리하다는 것을 알 수 있었다. Low molecular weight species were extracted from PC and SAN by a solvent extraction method in order to investigate the effect of low molecular weight species on interfacial tension and affinity between PC and SAN. From the analysis of molecular weight distribution by the GPC, it was confirmed that the low molecular weight species were effectively eliminated by the solvent extraction. Interfacial tension measurements and morphological observation were carried out with the PC and SAN of which the low molecular weight species were extracted. Interfacial tension was increased and the infinity was decreased for the extracted PC and SAN pair. This result implied that the low molecular weight species play a role as a compatibilizer between two polymers. Among two polymers, low molecular weight SAN contributes more in the compatibilization. Thus, it is favorable to use SAN containing a larger amount of low molecular weight species in fabrication of PC/ABS blend.

Fundamental studies on the separation of coal derivatives by means of gel permeation chromatography (GPC) are reported on (1) the chromatographic conditions for preparative GPC separation for structural analyses of coal and (2) basic experiments to odtain the molecular weight distributtion from analytical GPC elution curves using the chloroform soluble qart (γ-part) of pyridine extract from Akabira coal. On the basis of this informaton, the distributions of molecularweight of oil and asphaltene obtained from hydrogenolysis of Akabira coal are investigated by GPC analyses and their variation with reaction temperature is discussed.The petroleum soluble portion (γ1-part) and the insoluble portion (γ2-4-part) from the γ-part were selected as the sample for the discussion of the optimum conditions for GPC separation, such as pore size of gel and elution solvent. From the experimental results, it is obvious that separation by preparative GPC is achieved, odtaining fractions of considerably narrow molecular weight distribution. This contributed remarkably to the resolution of thechemical structure of coal. The relationship detween the elution volume (Ve) of the analytical GPC and average molecular weight (M) estimated by vapor pressure osmometry is fairly good for the fractionation products from preparative GPC (Fig. 9, 10). The M-Ve correlation lines of the 1- and the 2-4-parts were straight lines of different slope. Therefore it was assumed that the difference was due to a difference in structural type on the components. Consequently, these γ relationships of log M-Ve can be applied to the estimation of the molecular weight distribution from analytical GPC chromatograms as the correlation lines of high-molecular and low-molecular weight components respectively for the coal derived liquids.Oil and asphaltene in hydrogenolysis products werealso separated into fraction on the basis of molecular weight by preparative GPC and each fraction was correlated by elution counts of analytical GPC and average molecular weight. The results of these relationships were in fairly good agreement with correlation lines of log M-Ve odtained from the γ1 and the γ2-4 componets respectively (Fig. 13, 14). From the elution curves of analytical GPC for oil and asphaltene of varying reaction temperature, it is recognized that the distribution of molecular wight for asphaltene shifts gradually in the direction of a lower molecular weight distribution as the reaction temperature increases. On the other hand, the distribution of moleclar weight of oil changes only slightly and tends to converge to the constant distribution of low molecular weight components.

ABSTRACTA modified poly(aspartic acid) (PASPTU) as an efficient formaldehyde adsorbent is successfully prepared by grafting poly(aspartic acid) (PASP) with threonine and urea. The graft copolymer is characterized by means of nuclear magnetic resonance, Fourier transform infrared spectroscopy, and gel permeation chromatography. Its formaldehyde adsorbent property is measured. The optimal adsorption process is as follows: synthesis temperature was 40 °C, molar ratio of PSI, threonine, and urea was 1:0.6:0.4 and adsorption time was 3.0 h. In above condition, the formaldehyde adsorbent efficiency of the copolymer was nearly 100% when the PASPTU dosage was 0.5 g. The Langmuir and Freundlich adsorption isotherms are used to study the adsorption process of formaldehyde. The findings show that PASPTU has excellent formaldehyde adsorbent efficiency. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45798.

Cyclic polymers were produced by end-to-end coupling of telechelic linear polymers under dilute conditions in THF, using intramolecular atom transfer radical coupling or click chemistry. In addition to the expected shift to longer elution times on gel permeation chromatography (GPC) indicative of the formation of cyclic product, lower molecular weight species were consistently observed upon analysis of the unpurified cyclization reaction mixture. By systematically removing or altering single reaction components in the highly dilute cyclization reaction, it was found that THF itself was responsible for the low-molecular-weight material, forming oligomeric chains of poly(THF) regardless of the other reaction components. When the reactions were performed at higher concentrations and for shorter time intervals, conducive to intermolecular chain-end-joining reactions, the low-molecular-weight peaks were absent. Isolation of the material and analysis by 1H NMR confirmed that poly(THF) was being formed in the highly dilute conditions required for cyclization by end-to-end coupling. When a series of mock cyclization reactions were performed with molar ratios of the reactants held constant, but concentrations changed, it was found that lower concentrations of reactants led to higher amounts of poly(THF) side product.

Water-soluble synthetic polymers are extensively used in cosmetics, detergents and paints. Many end up in wastewater and, later on, in wastewater-treatment plants. In order to gain an insight into their fate in such plants, fluorescence and radioactivity labelings were compared using a lab-scale reactor designed to mimic industrial conditions. Two fermentation media were considered, namely a mixture of E402 and E204 micro-organisms and an activated sludge collected from a water-treatment plant located in the south of France. A sample of low molar mass commercial poly(acrylic acid) (PAA) was labeled by radioactivity with tritium and by coupling the 6-aminofluorescein fluorescent dye. Labeled PAA-containing sludges were allowed to ferment. To monitor the fate of the polymers, aliquots of the fermented mixtures were withdrawn at selected times and centrifuged. Liquid and solid phases were analyzed by scintigraphy or UV spectrometry, depending of the labeling techniques. Both techniques led to similar distributions, c.a. 75% in the supernatant and 25% in the solid phase. Distributions remained constant during the biological tests. There was no degradation of the commercial PAA after aqueous size exclusion chromatography (SEC), in agreement with literature. These features showed that fluorescence-labeling can be used instead of the complex and expensive radiolabeling. The validated fluorescence-based method was then applied to a linear poly(acrylic acid) synthesized by ATRP and labeled with 6-aminofluorescein. There was no significant difference between the commercial and the linear poly(acrylic acid)s. In contrast, a linear PAA with 5% of tert-butyl ester repeating units was predominantly found in the solid phase although adsorption or absorption by micro-organisms could not be demonstrated. The method based on fluorescence labeling should be applicable to other water soluble polymers provided that the dye remains attached to the polymer as it was the case for the studied poly(acrylic acid)s.

Poly(lactic-co-glycolic acid) (PLGA) is a biocompatible, biodegradable polymer approved by the FDA and EMA, which is the most widely used in the field of health. In this study, PLGA was synthesized primarily from lactide and glycolide by polycondensation and ring-opening polymerization. Then, amino acid derivatives of PLGA were synthesized by the reaction of PLGA and amino acids in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC). The polymers synthesized were PLGA, PLGA-L-glutamic acid (PLGA-G), and PLGA-L-aspartic acid (PLGA-A). The chemical structure of these polymers was confirmed by 1H and 13C Nuclear Magnetic Resonance (1H NMR and 13C NMR), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and Gel Permeation Chromatography (GPC). When the 13C NMR analyses of PLGA-amino acid derivatives were observed, an increase in the number of carbonyl carbons around 170 ppm was found and the structure accuracy was supported. In addition, when the FTIR analyses of PLGA-amino acid derivatives were examined, the structure was confirmed by observing the signal of the amide bond carbonyl vibration at 1700 cm-1. While the typical endothermic thermogram of the PLGA-amino acid derivative structures was observed by DSC analysis, it was shown that the structures were low molecular weight polymers [~5000-6000 Da] by GPC analysis.

pH-responsive poly(aspartic acid) hydrogel-coated magnetite nanoparticles for biomedical applications

Influencing factors on in vitro micelle stability of adriamycin-block copolymer conjugates

Synthesis, complex formation and corneal permeation of cyclodextrin-modified, thiolated poly(aspartic acid) as self-gelling formulation of dexamethasone

Emission level, particle size and exposure risks of airborne bacteria from the oxidation ditch for seven months observation

Exogenous proline treatment inhibiting enzymatic browning of fresh-cut potatoes during cold storage

Two major superoxide dismutases (SODs; SODs I and II) were found in the crude enzyme extract of wheat seedlings after heat treatment, ammonium sulfate fractionation, anionic exchange chromatography, and gel permeation chromatography. The purification fold for SODs I and II were 154 and 98, and the yields were 11 and 2.4%, respectively. SOD I was further characterized. It was found that SOD I from wheat seedlings is a homodimer, with a subunit molecular mass of 23 kDa. Isoelectric focusing electrophoresis (IEF) and zymogram staining results indicated that the isoelectric point of SOD I is 3.95. It belongs to the MnSOD category due to the fact that it was insensitive to KCN or hydrogen peroxide inhibitor. This MnSOD from wheat seedlings was found to be stable over pH 7-9, with an optimum pH of 8, but was sensitive to extreme pH, particularly to acidic pH. It was stable over a wide range of temperatures (5-50 degrees C). Thermal inactivation of wheat seedling MnSOD followed first-order reaction kinetics, and the temperature dependence of rate constants was in agreement with the Arrhenius equation. The activation energy for thermal inactivation of wheat seedling MnSOD in the temperature range of 50-70 degrees C was found to be 150 kJ/mol. HgCl2 and SDS at a concentration of 1.0 mM significantly inhibited enzyme activity. Chemical modification agents, including diethyl pyrocarbonate (2.5 mM) and Woodward's reagent K (50 mM), significantly inhibited the activity of wheat seedling SOD, implying that imidazole groups from histidine and carboxyl groups from aspartic acid and glutamic acid are probably located at or near the active site of the enzyme.

The interaction of radiocobalt with glycine, alanine or aspartic acid dissolved in seawater was investigated under laboratory conditions by means of adsorption on Chelex 100 solvent extraction with dithizone or gel filtration chromatography. The results also were compared with those in freshly prepared or stored culture filtrates of chlorella, fishpond and offshore seawaters in which ionic radiocobalt was spiked, respectively. The distribution coefficients for Co in Chelex 100 and the extraction rates (%) of Co with dithizone in carbon tetrachloride decreased more greatly with time in the presence of the amino acids than in the control. The inhibitory effect of glycin on the adsorption of Co on the Chelex 100 was smaller than that of alanine or aspartic acid. In the fishpond and offshore seawaters or freshly prepared chlorella culture filtrate, the distribution coefficients for Co in Chelex 100 were somewhat greater than in the control, while no significant difference was observed in dithizone extraction. The results of Sephadex G-10 gel filtration chromatography for Co showed that the higher molecular species of Co associated with the amino acids occurred after several days ageing and then increased together with decreasing in the lower molecular species.