Degradation Of Polyethylene Glycol Research Articles

Photocatalytic Degradation of Polyethylene Glycol by Nano-Titanium Dioxide Modified With Ferric Acetylacetonate

The surface of anatase TiO2 nanoparticles was modified by ferric acetylacetonate complex Fe(acac)3. This modification improved the dispersion of TiO2 in polymer and also the photocatalytic activity. The photodegradation of polyethylene glycol (PEG) catalyzed by modified TiO2 (Fe-TiO2) was extensively studied. The degradation character was evident. For example, the polymer lost its weight gradually, and the molecular weight decreased. Meantime the molecular weight distribution index increased. The molecular weight of PEG has a great influence upon the degradation. In all cases Fe-TiO2 displayed much higher catalytic activity than the neat TiO2.

Polyethylene Glycol/Fe<sub>3</sub>O<sub>4</sub> Nanoparticle Composite Materials: Structure, Physical Properties and Application

Fe3O4 nanoparticles with a highly symmetric octadecahedral nanobox structure were fabricated using β-cyclodextrin as a protection agent. A series of composites (CM-1-CM-4) of polyethylene glycol (PEG) and Fe3O4 nanoparticles with different initial mass ratios were prepared using a colloid process. We found that the shape of the composites depended on the amount of Fe3O4 nanoparticles. In particular, the melting process of PEG was not only influenced by the presence of Fe3O4 nanoparticles, but also by their amount. We also noticed that the crystallinity of PEG lowered upon compositing with Fe3O4 nanoparticles, and decreased as the amount of Fe3O4 nanoparticles increased with the exception of CM-4. Interestingly, the degradation of PEG was affected by the Fe3O4 nanoparticles, leading to the appearance of different degradation products. Like the initial Fe3O4 nanoparticles, the Fe3O4 components in the composites exhibited typical soft ferromagnetism but possessed much lower saturation magnetizations. X-ray photoelectron spectroscopy (XPS) experiments revealed that electronic shift occurred from iron to oxygen. The resulting decrease in the electronic density of iron explained the observed decrease in saturation magnetizations of the composites. The composites induced strong surface-enhanced Raman scattering of organic dyes that depended on the amount of Fe3O4 nanoparticles in the composite. This study contributes to the development of composite materials combining polymers with inorganic nanoparticles.

Exploring micromycetes biodiversity for screening benzo[a]pyrene degrading potential

Twenty-five strains of filamentous fungi, encompassing 14 different species and belonging mainly to Ascomycetes, were tested for their ability to degrade benzo[a]pyrene (BaP) in mineral liquid medium. The most performing isolates for BaP degradation (200 mg l(-1)) in mineral medium were Cladosporium sphaerospermum with 29 % BaP degradation, i.e., 82.8 μg BaP degraded per day (day(-1)), Paecilomyces lilacinus with 20.5 % BaP degradation, i.e., 58.5 μg BaP day(-1), and Verticillium insectorum with 22.3 % BaP degradation, i.e., 64.3 μg BaP day(-1), after only 7 days of incubation. Four variables, e.g., biomass growth on hexadecane and glucose, BaP solubilization, activities of extracellular- and mycelium-associated peroxidase, and polyethylene glycol degradation, were also studied as selective criteria presumed to be involved in BaP degradation. Among these variables, the tests based on polyethylene glycol degradation and on fungal growth on hexadecane and glucose seemed to be the both pertinent criteria for setting apart isolates competent in BaP degradation, suggesting the occurrence of different mechanisms presumed to be involved in pollutant degradation among the studied micromycetes.

Effects of macromolecular crowding on the structural stability of human α-lactalbumin

The folding of protein, an important process for protein to fulfill normal functions, takes place in crowded physiological environments. α-Lactalbumin, as a model system for protein-folding studies, has been used extensively because it can form stable molten globule states under a range of conditions. Here we report that the crowding agents Ficoll 70, dextran 70, and polyethylene glycol (PEG) 2000 have different effects on the structural stability of human α-lactalbumin (HLA) represented by the transition to a molten globule state: dextran 70 dramatically enhances the thermal stability of Ca(2+)-depleted HLA (apo-HLA) and Ficoll 70 enhances the thermal stability of apo-HLA to some extent, while PEG 2000 significantly decreases the thermal stability of apo-HLA. Ficoll 70 and dextran 70 have no obvious effects on trypsin degradation of apo-HLA but PEG 2000 accelerates apo-HLA degradation by trypsin and destabilizes the native conformation of apo-HLA. Furthermore, no interaction is observed between apo-HLA and Ficoll 70 or dextran 70, but a weak, non-specific interaction between the apo form of the protein and PEG 2000 is detected, and such a weak, non-specific interaction could overcome the excluded-volume effect of PEG 2000. Our data are consistent with the results of protein stability studies in cells and suggest that stabilizing excluded-volume effects of crowding agents can be ameliorated by non-specific interactions between proteins and crowders.

An approach to polymer degradation through microbes

Inertness and indiscriminate uses as well as growing water and land pollution problems have lead to concern about plastics. Present paper investigates the possibility of plastic degradation by microbes isolated from forest soil and automobile washout sludge. The in-vivo degradation was studied by litter bag experiment by taking 1 g of each plastic and buried under forest soil and automobile wash-out sludge at a depth of 15 cm from the surface during the month of September to February, 20102011. An in-vitro experiment was started after collecting the plastic samples from the litter bag experiment and the microbes were isolated from the surface of the plastic. Then the isolated microbes inoculated in the Burk’s medium without carbon source in two sets, one with plastic and the other with polyethylene glycol (PEG). Result showed that no variety of plastic comfortable degraded under burial condition during six months. But interesting result was recorded from Scanning Electron Microscopy (SEM) study. The preliminary screening of biodegradation capability was done by Fourier Transform Infra Red (FTIR) Spectroscopy for surface changes. Again, degradation of PEG by microbes clearly indicates their existence in the said medium. Therefore it can be speculated that microbes has enough potential to degrade plastic with due course of time.

Effects of microbial population in degradation process of xenobiotic polymers

Microbial depolymerization processes of exogenous type are studied for biodegradation of polyethylene glycol. The time factor of a degradation rate is the microbial population which grows on degraded monomer units as the carbon source. Numerical simulation shows that our model is of practical use. References F. Kawai, M. Watanabe, M. Shibata, S. Yokoyama, and Y. Sudate. Experimental analysis and numerical simulation for biodegradability of polyethylene. Polymer Degradation and Stability, 76:129--135, 2002. doi:10.1016/S0141-3910(02)00006-X F. Kawai, M. Watanabe, M. Shibata, S. Yokoyama, Y. Sudate, and S. Hayashi. Comparative study on biodegradability of polyethylene wax by bacteria and fungi. Polymer Degradation and Stability, 86:105--114, 2004. doi:10.1016/j.polymdegradstab.2004.03.015 Fusako Kawai and Shogo Enokibara. Symbiotic degradation of polyethylene glycol (peg) 20,000-phthalate polyester by phthalate ester- and peg 20,000-utilizing bacteria. Journal of Fermentation and Bioengineering, 82(6):575--579, 1996. M. Watanabe and F. Kawai. Numerical simulation of microbial depolymerization process of exogenous type. ANZIAM J., 46(E):C1188--C1204, 2005. Proc. of 12th Computational Techniques and Applications Conference, CTAC-2004, Melbourne, Australia in September 2004, Editors: Rob May and A. J. Roberts http://anziamj.austms.org.au/ojs/index.php/ANZIAMJ/article/view/1014 M. Watanabe and F. Kawai. Mathematical study of the biodegradation of xenobiotic polymers with experimental data introduced into analysis. ANZIAM J., 47:C665--C681, 2007. Proceedings of the 7th Biennial Engineering Mathematics and Applications Conference, EMAC-2005, Melbourne, Editors: Andrew Stacey and Bill Blyth and John Shepherd and A. J. Roberts, http://anziamj.austms.org.au/ojs/index.php/ANZIAMJ/article/view/1069 M. Watanabe and F. Kawai. Mathematical analysis of microbial depolymerization processes of xenobiotic polymers. In Geoffry N. Mercer and A. J. Roberts, editors, Proceedings of the 14th Biennial Computational Techniques and Application Conference, CTAC2008, volume 50 of ANZIAM J., pages C930--C946, 2009. http://anziamj.austma.org.au/ojs/index.php/ANZIAMJ/article/view/1465 M. Watanabe and F. Kawai. Modeling and simulation of biodegradation of xenobiotic polymers based on experimental results. In BIOSIGNALS 2009, Second International Conference on Bio-inspired Systems and Signal Processing, Proceedings, Porto, Portugal, 14--17 January, 2009, pages 25--34. INSTICC Press, 2009. M. Watanabe and F. Kawai. Study on effects of microorganism in depolymerization process of xenobiotic polymers by modeling and simulation. In Ana Fred, Joaquim Filipe, and Hugo Gamboa, editors, Proceedings of the First International Conference on Bioinformatics, Valencia, Spain, January 20--23, 2010, pages 181--186. 2010 INSTICC, Institute for Systems and Technologies of Information, Control and Communication, 2010. M. Watanabe, F. Kawai, M. Shibata, S. Yokoyama, and Y. Sudate. Computational method for analysis of polyethylene biodegradation. Journal of Computational and Applied Mathematics, 161(1):133--144, December 2003. doi:10.1016/S0377-0427(03)0051-X M. Watanabe, F. Kawai, M. Shibata, S. Yokoyama, Y. Sudate, and S. Hayashi. Analytical and computational techniques for exogenous depolymerization of xenobiotic polymers. Mathematical Biosciences, 192:19--37, 2004. doi:10.1016/j.mbs.2004.06.006

Thermal degradation of polyethylene glycol 6000 and its effect on the assay of macroprolactin

ObjectivesTo study the effectiveness of partially degraded polyethylene glycol 6000 (PEG) as a precipitant for macroprolactin. Design and methodsPEG was heated to 63°C in air for up to 20days and its effectiveness assessed as a precipitant for sera containing normal prolactin or macroprolactin. Decomposition was studied chemically and with NMR spectroscopy. ResultsThermal degradation was similar to what had occurred over several years of natural degradation. Initially PEG degraded 2–5days caused excess precipitation of monomeric prolactin (false-positive macroprolactinemia). Samples degraded 18–20days failed to precipitate macroprolactin, giving false negative results. Two 1H NMR peaks at 4–4.5ppm were not detectable in undegraded PEG but were after 1day. Their relative integral increased to 20days. ConclusionsAging of PEG can be accelerated by heating. The suitability of PEG for use in macroprolactin assays can be assessed by the absence of peaks at 4–4.5ppm by 1H NMR.

The Free‐Radical Chemistry of Polyethylene Glycol: Organic Reactions in Compressed Carbon Dioxide

The thermal oxidative degradation of polyethylene glycol (PEG) is known to occur in an oxygen atmosphere at elevated temperatures. In this study, PEG radicals assumed to result from thermal oxidative degradation are successfully applied, in combination with compressed CO(2), to initiate a range of free-radical reactions, such as selective formylation of primary and secondary aliphatic alcohols, oxidation of benzylic alcohols, benzylic C==C bond cleavage, and benzylic sp(3) C--H oxidation, demonstrating enormous synthetic potential in a cost-efficient, practically useful, and environmentally friendly manner; not requiring any catalyst or additional free-radical initiator. We find that both PEG and molecular oxygen are prerequisites in order to perform these reactions smoothly. Given that dense CO(2) is immune to free-radical chemistry; it is an ideal solvent for such reactions. As a result, compressed CO(2) allows reactions initiated by PEG radicals to be tuned by subtly adjusting reaction parameters such as the CO(2) pressure, thereby enhancing the product selectivity. By attaining a high selectivity towards the desired products this methodology is practical for organic syntheses.

Polyethylene glycol radical-initiated oxidation of benzylic alcohols in compressed carbon dioxide

The PEG radical from oxidative degradation of polyethylene glycol was first used to initiate the oxidation of benzylic alcohols to carbonyl compounds without the need of a catalyst and/or additive in a viable synthetic, cost-effective and environmentally benign way, in which PEG/O2/CO2 acts as initiator, oxidant and solvent. Compressed CO2 in this study not only provides a safe environment to conduct the oxidation employing molecular oxygen as an oxidant, but also could improve the reaction and adjust the selectivity of the target product by altering CO2 pressure. Moreover, this methodology could be used to oxidize a set of benzyl alcohols. The findings introduced here provide useful examples for developing free-radical chemistry from PEG thermal oxidative degradation.

Involvement of PEG-carboxylate dehydrogenase and glutathione S-transferase in PEG metabolism by Sphingopyxis macrogoltabida strain 103

Sphingopyxis terrae and the Sphingopyxis macrogoltabida strains 103 and 203 are able to degrade polyethylene glycol (PEG). They possess the peg operon, which is responsible for the conversion of PEG to PEG-carboxylate-coenzyme A (CoA). The upstream (3.0 kb) and downstream (6.5 kb) regions of the operon in strain 103 were cloned and sequenced. The structure was well conserved between S. macrogoltabida strain 203 and S. terrae, except that two sets of transposases are absent in strain 203. The downstream region contains the genes for PEG-carboxylate dehydrogenase (PCDH), glutathione S-transferase (GST), tautomerase, and a hypothetical protein. The genes for pcdh and gst were transcribed constitutively and monocistronically, indicating that their transcription is independent of the operon regulation. PCDH and GST were expressed in Escherichia coli and characterized biochemically. PCDH is a homotetramer of 64-kDa subunits and contains one molecule of flavin adenine dinucleotide per subunit. The enzyme dehydrogenates PEG-carboxylate to yield glyoxylate, suggesting that the enzyme is the third enzyme involved in PEG degradation. GST is a homodimer of 28-kDa subunits. GST activity was noncompetitively inhibited by acyl-CoA and PEG-carboxylate-CoA, suggesting the interaction of GST with them. The proposed role for GST is to buffer the toxicity of PEG-carboxylate-CoA.

Analysis of acids and degradation products related to iron and sulfur in the Swedish warship Vasa

Abstract Aqueous wood extracts from the historic Swedish warship Vasa have been analyzed by 1H-NMR spectroscopy, ion chromatography, and matrix assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry as part of studies on the chemical degradation related to increased levels of iron and sulfur. The results show that low molecular organic acids have accumulated in the Vasa wood after the 1961 salvage. The increased acidity was found in a context of chemical degradation of the wood polymers and the conservation agent polyethylene glycol (PEG) in iron-rich parts of the timber. Formic, glycolic and oxalic acid are all possible end-products of oxidative degradation of wood polymers, whereas hydrolysis of acetyl groups in xylan may have contributed to increased concentrations of acetic acid. MALDI-TOF spectra of PEG displaced towards low-molecular PEG oligomers, as reported earlier, were accompanied by increased levels of formic acid, indicating oxidative degradation of PEG. PEG with a carboxylic acid end group (PEGC) was observed to a minor degree in the wood. However, analysis of stored conservation treatment solutions showed high concentrations of PEGC yielding significant contributions to the acidity during the 1960s conservation period. PEGC was probably formed as a result of microbial processes during the early conservation regime. Calculations using concentrations and well-established acidity constants show that oxalic and formic acid are the primary contributors to a low pH in the wood. The increased acidity in the interior of the wood was found in the absence of sulfur compounds but in a context of iron. The majority of the sub-samples with significant levels of sulfate in the surface region with a prospective sulfur oxidation, however, showed neither a decreased pH nor significant depolymerization. This indicates that oxidation pathways of organically bound sulfur do not necessarily produce strong acids, and thereby free protons, as the final product. These observations imply opposing effects of iron and reduced sulfur species, with iron acting as a initiator in oxidative reactions of Fenton type, whereas the reduced organic sulfur compounds may act as anti-oxidants.

Fenton-induced degradation of polyethylene glycol and oak holocellulose. A model experiment in comparison to changes observed in conserved waterlogged wood

Abstract Degradation of polysaccharides and polyethylene glycol have recently been observed in the wood of the Swedish war-ship Vasa. The signs of degradation are highly correlated to the presence of iron compounds, indicating iron initiated reactions of Fenton type. In order to test this hypothesis pure polyethylene glycol (PEG, Mw =1500 u) and prepared oak holocellulose were oxidized by hyddroxyl radicals induced by Fenton's reagent [Fe(II)/H2O2] in aqueous solution. The changes in molar weight distribution (MWD) were analysed by MALDI-TOF mass spectrometry and size exclusion chromatography. The changes in MWD were consistent to random scission of the polymers according to statistical simulations. By NMR analysis the main PEG degradation products formed were identified as PEG molecules with different end groups: alcohols, aldehydes and formate esters; the latter hydrolyse to formic acid. The all over results show close similarities to the situation observed in the Vasa wood and strengthen the hypothesis of oxidative degradation initiated by iron compounds in the wood.

N‐Methylation and N‐Formylation of a Secondary Amine Drug (Varenicline) in an Osmotic Tablet

Significant degradation of the amine-based smoking cessation drug varenicline tartrate in an early development phase osmotic, controlled-release (CR) formulation yields predominantly two products: N-methylvarenicline (NMV) and N-formylvarenicline (NFV). NMV is produced by reaction of the amine moiety with both formaldehyde and formic acid in an Eschweiler-Clarke reaction, while NFV is formed by reaction of formic acid alone with varenicline. This represents the first report of these reactions occurring on storage of solid pharmaceutical formulations. Both formaldehyde and formic acid are formed from oxidative degradation of polyethylene glycol (PEG) used in an osmotic coating through a process heavily dependent on the physical state of the PEG. When the concentration of PEG in the coating is sufficiently low, the PEG remains phase compatible with the other component of the coating (cellulose acetate) such that its degradation (and the resulting drug reactivity) is effectively eliminated. Antioxidants in the coating and oxygen scavengers in the packaging also serve to prevent the PEG degradation, and consequently provide for drug stability.

Degradation of polyethylene glycol and hemicellulose in the Vasa

Abstract Mass spectrometric analysis of aqueous wood extracts from the Swedish warship Vasa reveals a serious chemical condition in the depth of the wood. The surface is less affected. Polyethylene glycol, used as conservation agent, is affected and partly degraded, and low-molecular fragments from hemicellulose are found at sites with high iron content and low pH. These findings imply a catalytic oxidative process and acidic hydrolysis in the wood, which contributes to a new picture of the challenge of long-term preservation of the Vasa.

Polyethylene glycol (PEG)–carboxylate–CoA synthetase is involved in PEG metabolism in Sphingopyxis macrogoltabida strain 103

Sphingopyxis macrogoltabida strain 103 possesses polyethylene-glycol (PEG)-inducible pegBCDAE operon encoding the genes relevant to PEG degradation. PEG is converted to PEG-carboxylate by PegA (PEG dehydrogenase) and PegC (PEG-aldehyde dehydrogenase). In this study, the recombinant PegE (homologous to acyl-CoA synthetases) was characterized. PegE was an acyl-CoA synthetase active for PEG-carboxylate and fatty acids. Judging from the nature of this kind of protein (located on the cytoplasmic membrane as a translocator), PegE might be responsible for the translocation of PEG-carboxylate from the periplasm into the cytoplasm or for the detoxification of strong acidity of the substrate.

Degradation of polyethylene glycol by Fenton reaction: a comparative study

Photochemical advanced oxidation processes (AOPs) utilising different Fenton systems were investigated in laboratory-scale experiments for the degradation of polyethylene glycol (PEG). The results of the study showed that the degradation rate of PEG was strongly accelerated by the homogeneous system, and this proved to be advantageous in comparison to the heterogeneous system. Between Fenton and photo-Fenton heterogeneous systems, the photo-Fenton process reached the highest removal rate of the organic compound, due to the enhanced reduction efficiency of Fe(III) to Fe(II) under UV-irradiation. The oxidation rate in the heterogeneous system was investigated using varying different parameters, such as the pH value, the concentration of hydrogen peroxide and the amount of Fe(OH)3 as the catalyst. For the homogeneous Fenton system the rate of degradation is significantly higher. At the same time of operation the elimination rates can be found to be 30% over the rates of the heterogeneous system. Optimising the typical influence parameters mentioned before, a degradation of about 93% of PEG can be achieved by using the homogeneous Fenton system.

Structure and conservation of a polyethylene glycol-degradative operon in sphingomonads

Sphingopyxis terrae, and Sphingopyxis macrogoltabida strains 103 and 203, can degrade polyethylene glycols (PEGs). They differ in the following respects: (i) different substrate specificities (chain length) of assimilable PEG, (ii) PEG-inducible or constitutive PEG-degradative proteins, and (iii) symbiotic or axenic degradation of PEG. S. terrae was able to incorporate PEG 6000, but strain 103 could not incorporate more than PEG 4000, suggesting that the difference in assimilable PEG chain length depends on the ability to take up substrate. PEG-degradative genes (pegB, C, D, A, E and R) from these strains were cloned. Their primary structures shared a high homology of more than 99 %. The peg genes encode a TonB-dependent receptor (pegB), a PEG-aldehyde dehydrogenase (pegC), a permease (pegD), a PEG dehydrogenase (pegA) and an acyl-CoA ligase (pegE), and in the opposite orientation, an AraC-type transcription regulator (pegR). The peg operon was flanked by two different sets of transposases. These three strains contained large plasmids and the operon was located in one of the large plasmids in S. terrae. The peg genes could be detected in other PEG-degrading sphingomonads. These results suggest that the peg genes have evolved in a plasmid-mediated manner. An insertion of a transposon gene (pegF) between pegD and pegA in strain 203 was found, which caused the constitutive expression of pegA in this strain.

Characterisation of the polyethylene glycol impregnation of the Swedish warship Vasa and one of the Danish Skuldelev Viking ships

The Swedish 17th century warship Vasa and the Danish Skuldelev Viking ships from the 11th century were impregnated with polyethylene glycol (PEG) in the 1960s. The molecular weight, amount and integrity of this PEG were investigated at a range of depths below the wood surface. Large amounts of PEG could be extracted from degraded parts of the ships but hardly any from sound parts. Mass spectrometry showed that PEG 4000 is present only in the surface layers of the wood, PEG 1500 and PEG 600 are present at all depths of the wood that has been treated with it. Low molecular weight PEG was detected in one of the Skuldelev ships by mass spectrometry and Size Exclusion Chromatography (SEC), it is argued that this is due to degradation of PEG 4000. SEC also showed that PEG 600 is the major PEG component in the Vasa which makes this particular object sensitive to changes in air humidity since PEG 600 is hygroscopic.

Formic and acetic acids in archaeological wood. A comparison between the Vasa Warship, the Bremen Cog, the Oberländer Boat and the Danish Viking Ships

Abstract A method has been developed to analyse and quantify formic and acetic acids in archaeological and fresh wood. The method takes advantage of the fact that, in equilibrium, the gas-phase concentrations of formic and acetic acids over pulverised archaeological wood in a sulfuric acid solution are proportional to their absolute concentrations in wood. The method is based on automated solid-phase micro extraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS). Good linearity of the calibration curves was observed. The content of formic and acetic acids in archaeological wood from ships conserved with polyethylene glycol (PEG) was determined. The content of formic acid is related to the intensity of conservation and, hence, the PEG content in wood. Accordingly, formic acid found in the hull of the ships may partly be a result of PEG degradation. The formic acid content in the Vasa warship is, on average, not higher than in the other ships analysed. In contrast, the acetic acid content in PEG-preserved archaeological wood is lower than in fresh wood. The acetic acid content is age-dependent and is lowest in 1000-year-old wood. The acetic acid probably originates from the wood.

Degradation of PEG in the Warship Vasa

AbstractThe distribution and ageing of polyethylene glycol (PEG) in the Vasa warship has been examined and compared with other archaeological shipwrecks which have also been impregnated with PEG. The distribution of the PEG has been characterised using a variety of mass spectrometric and FT‐IR techniques. Our results show that the PEG after 30 years is still in a reasonably good condition, with a molecular weight distribution that resembles fresh PEG. Only minor levels of degradation products were found. It seems that the PEG preserved wood contains an increased amount of formic acid and the results suggest that it originates from the PEG. Acetic acid is also present; this probably originates from the wood.