Biodegradation of chemically modified wheat gluten-based natural polymer materials

Biodegradation of a series of chemically modified thermally processed wheat gluten (WG)-based natural polymers were examined according to Australian Standard (AS ISO 14855). Most of these materials reached 93-100% biodegradation within 22 days of composting, and the growth of fungi and significant phase deformation were observed during the process. Chemical crosslinking did slow down the rate or reduce the degree of the biodegradation with different behaviours for different modified systems. The segments containing structures derived from the reactions with additives such as tannin or epoxidised soybean oil remained in the degradation residues while the glycidoxypropyl trimethoxysilane agent produced ∼20% un-degraded residues containing silicon-crosslinking structures. The biodegradation rate of each component of the materials was also different with the protein and starch components degraded fast but lipid degraded relatively slowly.     

Fire retardancy and biodegradability of poly(methyl methacrylate)/montmorillonite nanocomposite

The poly(methyl methacrylate) (PMMA)/montmorillonite (MMT) nanocomposite was prepared by emulsifier-free emulsion technique and its structure and properties were characterized with infra red, X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, and cone calorimetry. The highly exfoliated MMT layers with dimension 1-2 nm in thickness were randomly dispersed in the polymer matrix containing MMT lower than 5% w/v, whereas the intercalated structure was predominant with MMT content higher than 5% w/v. Consequently, the fine dispersion of the MMT and the strong interactions between PMMA and MMT created significant improvement of the thermo-stability and fire retardancy of the nanocomposite. The combustion behavior has been evaluated using oxygen consumption cone calorimetry. In addition, a scheme was proposed to describe fire retardancy of PMMA and MMT as well as the correlation between the interaction and structure in polymer/clay systems. The biodegradability of the nanocomposite fire-retardant was tested for its better commercialization.     

Structure and properties of biodegradable wheat gluten/attapulgite nanocomposite sheets

Wheat gluten (WG) and Attapulgite (ATP) was mixed in acidic solution and freeze-dried, thermally compression-molded to form nanocomposite sheet. The influences of reduction and sonication on structure of wheat gluten were examined by Raman spectrum. The variation of disulfide bonding in wheat gluten show that the sonication is more effective than reduction on the breakage of disulfide bonds, whereas the content of disulfide bonds in the WG sheet molded by sonicated WG powder is the highest in the molded sheets. FT-IR analysis displays that the bands in the range of 1700-1600 cm⁻¹ shift to higher frequency after mixing WG and ATP powders and molding the nanocomposite. The tensile and bending properties of the WG sheet increase with addition of ATP powder, and the properties of the sheet molded by sonicated WG powder decrease for the reduction of the disulfide bonding, but the properties of the sheet can be improved by addition of ATP. The WG/ATP nanocomposite images observed by SEM and TEM show that rod-like ATP particles are evenly dispersed in WG matrix, but the crystal structure of ATP is impervious. The viscoelasticity of the WG sheet declines with addition of ATP particle, and that the α-relaxation of the WG sheet molded by sonicated WG powder shift to high temperature and become broad. Both mass and bending strength of 7 wt% WG/ATP nanocomposite sheet show a decline over a soil exposure time of 20 days.     

Enantioselective separation of the carfentrazone‐ethyl enantiomers in soil,water and wheat by HPLC

A simple enantioselective HPLC method was developed for measuring carfentrazone‐ethyl enantiomers. The separation and determination was accomplished on an amylose tris[(S)‐α‐methylbenzylcarbamate] (Chiralpak AS) column using n‐hexane/ethanol (98:2, v/v) as mobile phase at a flow rate of 1.0 mL/min with UV detection at 248 nm. The effects of mobile‐phase composition and column temperature on the enantioseparation were discussed. The accuracy, precision, linearity, LODs, and LOQ of the method were also investigated. LOD was 0.001 mg/kg in water, 0.015 mg/kg in soil and wheat, with an LOQ of 0.0025 mg/kg in water and 0.05 mg/kg in soil and wheat for each enantiomer of carfentrazone‐ethyl. SPE was used for the enrichment and cleanup of soil, water, and wheat samples. Recoveries for two enantiomers were 88.4–106.7% with RSD_r of 4.2–9.8% at 0.1, 0.5, and 1 mg/kg levels from soil, 85.8–99.5% with the RSD_r of 4.4?9.6% at 0.005, 0.025, and 0.05 mg/kg levels from water, and from wheat the recoveries were 86.3?91.3% with RSD_r below 5.0% at 0.2, 0.5, and 1 mg/kg levels. This method could be used to identify and quantify the carfentrazone‐ethyl enantiomers in food and environment.     

Synthesis of exfoliated polystyrene/montmorillonite nanocomposite by emulsion polymerization using a zwitterion as the clay modifier

Montmorillonite (MMT) was modified with zwitterion aminoundecanoic acid (AUA). First AUA was protonized to facilitate molecules to get into the galleries of the montmorillonite to accomplish ion exchange, and the carboxyl groups were then ionized in the alkaline aqueous media to enable exfoliation of the clay. It was demonstrated by rheological measurements and atomic force microscopic studies that exfoliation of the clay driven by the electrostatic repulsion took place in an alkaline medium. Polystyrene/montmorillonite (PS/MMT) nanocomposite was synthesized via emulsion polymerization in the presence of the modified MMT. The exfoliated microstructure of the composites was studied by the X-ray diffraction and transmission electron microscopy. The exfoliated PS/MMT nanocomposite showed a greatly improved modulus, a higher glass transition temperature and a better thermal stability compared to the neat polystyrene and the intercalated PS/MMT composites.     

Studies of biodegradability of certain oils in forest soil as determined by the respirometric BOD OxiTop method

The suitability of the respirometric BOD OxiTop method for biodegradation studies of different oils in soil was assessed. Different forestry chain oils and wood-preservative oils were used as model substances. Experiments were carried out on different types of Finnish forest soils. The results of these experiments are in good agreement with our earlier results of oil-biodegradation experiments in water. The BOD OxiTop method proved to be a highly suitable analysis method for biodegradation studies of oils in soil.     

How can the Cross-Link Adducts Formed by Novel Trans Platinum Drug be Influenced by Hydrogen Bond

A systematic quantum chemical characterization of intrinsic structure, energies and spectral properties of all the studied cross-link adducts formed by the novel trans platinum with thiazole ligand has been carried out at B3LYP/6-31G^＊ level of theory with the Lanl2dz pseudo potential basis set for the Pt atom. Special attention has been paid to the relative stability of these complexes and the factors that probably alter the order of the relative stability. The important influence of hydrogen bond on the structures, the energies and the spectral property was revealed. Other factors that contribute to relative stability including solvation effect, entropy and electronic delocalization energy were taken into account. The stability energy of the whole complex, and the interaction energy between two purine bases and the [Pt-（NH3）thiazole]^2＋ group were adopted to study the interplay among subsystems and their contribution to relative stability of all the studied cross-link model. Finally, basic spectral properties of these complexes including H（8） chemical shifts of all the studied complexes and the VCD （vibrational circular dichroism） spectra of two pairs of GG chelate enantiomers, were provided in order to define the structure of the most possible duplex bearing novel trans platinum drug lesions.     

Potential effects of biochar application on mitigating the drought stress implications on wheat (Triticum aestivum L.) under various growth stages

Drought is the main abiotic stress that severely reduces wheat yield across the globe. To cope up this situation, use of organic amendments is the best option. Biochar is an organic soil amendment that is used to improve soil carbon, organic contents, improve water holding capacity of soil, enhance soil fertility and maintain desired soil. Present study was carried out under semi-arid climatic conditions to mitigate the adverse effects of drought at critical wheat growth stages i.e., tillering (DTS), flowering (DFS) and grain filling stage (DGFS) by using three biochar treatments viz. B₀ = Control, B₁ = 27.88 g kg⁻¹ and B₂ = 37.18 g kg⁻¹. Results revealed that drought stress negatively affected the growth and yield attributes of wheat at all critical growth stages, while, grain filling stage was found the most sensitive stage resulted severe yield reduction. However, biochar application significantly mitigated the detrimental effects of drought by improving number of fertile tillers (19.50%), spike length (6.52%), number of grains per spike (3.07%), thousand grain weight (6.42%), biological (9.43%) and economic yield (13.92%) as compared to control treatment. Moreover, biochar significantly improved water use efficiency and physiological attributes of drought stressed wheat. Principal component analysis linked different scales of study and demonstrated the potential of physio-biochemical traits to explain the wheat yield variations under drought condition with response to biochar application. In crux, biochar application (37.18 g kg⁻¹) can be used as an effective stratagem to achieve improved wheat grain yield through mitigating the adverse effects of drought stress.     

Separation of the unique proteins of wheat protein fractions by capillary electrophoresis

Summary The wheat maturation process was monitored by high-performance capillary electrophoresis. The different protein components of the albumin, globulin, gliadin and glutenin fractions from the Osborne extraction procedure were analysed. The wheat sample was a Hungarian winter wheat, cultivar Martonvásári 23. The protein fractions were analysed by capillary zone electrophoresis using a low pH phosphate buffer containing a polymeric additive and organic modifiers. The albumins and gliadins as well as glutenins showed a characteristic pattern of development during the maturation process. For these fractions the development occurred at different stages of maturation. The formation of protein fractions of wheat at different stages of maturation—and thus the entire maturation process—could be well characterised by high-performance capillary electrophoresis. Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September, 1–3, 1999     

Separation and quantification by high-performance liquid chromatography with light scattering detection of the main wheat flour phospholipids during dough mixing in the presence of phospholipase

Phospholipids (PL) are minor components of wheat flour involved in baking quality and exogenous phospholipids are used as emulsifiers giving better loaf volume and crumb grain. Few biochemical data are available on the phospholipid evolution during mixing, probably because of the time-consuming methods proposed for their extraction, separation and quantification. In the present study, the extraction, separation and quantification of the main wheat flour phospholipids were carried out. Total lipids (2% dry mass of wheat flour) were extracted from flour or dough by a mixture of chloroform-methanol-water (1:1:1 (v/v)). The phospholipids were separated from the lipid extract on silica cartridge by solid-phase extraction (SPE) procedure under a 1.5-4 mmHg vacuum, at a 0.8 mL min(-1) flow rate (1 mmHg = 133.322 Pa). The recovery of the lipid extract was 100%, whereas the SPE yield for the PLs was 50%. The resulting fraction was then submitted to HPLC with evaporative light scattering detection on a Diol stationary phase allowing the separation and quantification of each class of phospholipids, in less than 16 min. The developed method allowed to quantify the phospholipid amounts from eight wheat flours as well as their evolution during mixing in the presence of phospholipase.     

Comparison of direct solid sampling and slurry sampling for the determination of cadmium in wheat flour by electrothermal atomic absorption spectrometry

Two analytical methods for the determination of cadmium in wheat flour by electrothermal atomic absorption spectrometry without prior sample digestion have been compared: direct solid sampling analysis (SS) and slurry sampling (SlS). Besides the conventional modifier mixture of palladium and magnesium nitrates (10 μg Pd + 3 μg Mg), 0.05% (v/v) Triton X-100 has been added to improve the penetration of the modifier solution into the solid sample, and 0.1% H₂O₂ in order to promote an in situ digestion for SS. For SlS, 30 μg Pd, 12 μg Mg and 0.05% (v/v) Triton X-100 have been used as the modifier mixture. Under these conditions, and using a pyrolysis temperature of 800 °C, essentially no background absorption was observed with an atomization temperature of 1600 °C. About 2 mg of sample have been typically used for SS, although as much as 3-5 mg could have been introduced. In the case of SlS multiple injections had to be used to achieve the sensitivity required for this determination. Calibration against aqueous standards was feasible for both methods. The characteristic mass obtained with SS was 0.6 pg, and that with SlS was 1.0 pg. The limits of detection were 0.4 and 0.7 ng g⁻¹, the limits of quantification were 1.3 and 2.3 ng g⁻¹ and the relative standard deviation (n = 5) was 6-16% and 9-23% for SS and SlS, respectively. The accuracy was confirmed by the analysis of certified reference materials. The two methods were applied for the determination of cadmium in six wheat flour samples acquired in supermarkets of different Brazilian cities. The cadmium content varied between 8.9 ± 0.5 and 13 ± 2 ng g⁻¹ (n = 5). Direct SS gave results similar to those obtained with SlS using multi-injections; the values of both techniques showed no statistically significant difference at the 95% confidence level. Direct SS was finally adopted as the method of choice, due to its greater simplicity, the faster speed of analysis and the better figures of merit.     

Copper‐based supported catalysts for the atom transfer radical polymerization of methyl methacrylate: How can activity and control be tuned up?

This article is aimed at revisiting the synthesis of copper‐based catalysts immobilized onto crosslinked polystyrene (PS) resins carrying pyridinimine groups (PS–pyridinimine/CuBr). These supported catalytic systems were used for promoting the atom transfer radical polymerization of methyl methacrylate as initiated by ethyl‐2‐bromoisobutyrate. It was evidenced that the control over the polymerization reaction was strongly influenced by the coordination ability and extent of the transition‐metal salt on the supported pyridinimine ligands. For instance, increasing the ligand‐to‐catalyst molar ratio allowed for increasing the polymerization rate and improving the control over the molecular parameters of the synthesized poly(methyl)methacrylate (PMMA) in terms of the molar masses and molecular weight distributions. The PS–pyridinimine/CuBr supported catalyst was recycled and reused for further polymerization reactions. After two recycling steps, the reaction activity appeared to be preserved, and the control was improved in terms of the initiation efficiency. However, a slight increase in the polydispersity indices was observed. Interestingly, the introduction of a flexible polydimethylsiloxane spacer between the PS support and the catalytic sites led to some more improvement of the control over the molecular parameters of PMMA chains, which displayed narrower molecular weight distributions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 744–756, 2006     

一类三元共聚反应的拟二元化处理方法和简单稳态假定下的三元共聚的可拟二元化特性

对一类两种主单体比例保持恒定,微量或少量第三单体参与的改性三元共聚体系,采用了将两种主单体视为一种单体,微(少)量第三单体与此"主单体"进行拟二元共聚的处理方式,分别用动力学概念推导法和从三元共聚简易组成式直接导出法,推得拟二元共聚等效竞聚率计算式,两种方法所得结果一致.对文献报道的一些三元共聚实例进行了计算,证实了本...     

Structural studies of the allelic wheat glutenin subunits 1Bx7 and 1Bx20 by matrix-assisted laser desorption/ionization mass spectrometry and high-performance liquid chromatography/electrospray ionization mass spectrometry

Structural studies of the high molecular mass (HMM) glutenin subunits 1Bx7 (from cvs Hereward and Galatea) and 1Bx20 (from cv. Bidi17) of bread wheat were conducted using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and reversed-phase high-performance liquid chromatography/electrospray ionization mass spectrometry (RP-HPLC/ESI-MS). For all three proteins, MALDI-TOFMS analysis showed that the isolated fractions contained a second component with a mass about 650 Da lower than the major component. The testing and correction of the gene-derived amino acid sequences of the three proteins were performed by direct MALDI-TOFMS analysis of their tryptic peptide mixture. Analysis of the digest was performed by recording several MALDI mass spectra of the mixture at low, medium and high mass ranges, optimizing the matrix and the acquisition parameters for each mass range. Complementary data were obtained by RP-HPLC/ESI-MS analysis of the tryptic digest. This resulted in coverage of about 98% of the sequences. In contrast to the gene-derived data, the results obtained demonstrate the insertion of the sequence QPGQGQ between Trp716 and Gln717 of subunit 1Bx7 (cv. Galatea) and a possible single amino acid substitution within the T20 peptide of subunit 1Bx20. Moreover, the mass spectrometric data demonstrated that the lower mass components present in all the fractions correspond to the major components but lack about six amino acid residues, which are probably lost from the protein C-terminus. Finally, the results obtained provide evidence for the lack of glycosylation or other post-translational modifications of these subunits.     

Polymerization of 1‐olefins by zirconium/titanium precatalysts with O,N,O‐ligating atoms—can aggregation of catalyst be inferred from the reaction profile?

The 2‐[benzyl‐(2‐hydroxy‐2‐phenylethyl)‐amino]‐1‐phenylethanol ligand (1‐H₂) prepared as a diastereomeric mixture or in racemic and meso forms, from known procedure, has been disodiated and complexed with ZrCl₄. The precatalysts (mix‐1‐ZrCl₂, rac‐1‐ZrCl₂, and meso‐1‐ZrCl₂) were used in combination with methylaluminoxane and found to be active for the polymerization of 1‐hexene and 1‐octene. The high molecular weight polyhexenes (PHs) and polyoctenes (POs) thus obtained were isotactic in nature and showed a negligible amount of end groups arising from the chain termination reactions. In PHs and POs, there was linear correlation in the modified Arrhenius plot (the natural logarithm of the number‐average molecular weight vs. the reciprocal of the temperature), indicating the presence of a single active species. The enantiomerically pure titanium precatalyst ((R,R)‐1‐TiCl₂), when employed for the polymerization of 1‐hexene, was found to be active and the modified Arrhenius plot showed linear dependence demonstrating presence of a single active species. The analogous titanium precatalysts (mix‐1‐TiCl₂, rac‐1‐TiCl₂, and meso‐1‐TiCl₂) obtained from known procedures were also found to be active for the polymerization of 1‐octene. The rac‐1‐TiCl₂ precatalyst demonstrated a sigmoidal behavior in the modified Arrhenius plot for the POs and the mix‐1‐TiCl₂ precatalyst showed an exponential type of behavior. The obtained POs seemed to have small amounts of chain termination via β‐hydride elimination alone. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3599–3610, 2007     

How many hydrogen molecules can be inserted into C60? Comments on the paper ‘AM1 treatment of endohedrally hydrogen doped fullerene, nH2@C60’ by L. Türker and Ş. Erkoç [J. Mol. Struct. (Theochem) 638 (2003) 37–40]

The possibility of the formation of endohedral complexes between H₂ molecules and C₆₀ fullerene is discussed on the basis of general geometric considerations as well as the results of molecular mechanics calculations. The obtained results revealed that only one hydrogen molecule being incorporated inside the C₆₀ cage can form the stable complex in agreement with geometric considerations and recent experimental data. The reliability of semiempirical methods to study the problem of H₂ insertion into C₆₀ is also discussed.