Increasing Polyethylene Glycol Concentration Research Articles

In vitro screening of rice genotypes for drought tolerance using polyethylene glycol

The aim of the present investigation was to study in vitro somatic embryogenesis and to screen calli for drought tolerance using mature embryos as explants. Mature embryos of three aromatic (Pusa Basmati 1, Pant Sugandh Dhan 17, Taraori Basmati) and one non-aromatic (Narendra 359) indica rice (Oryza sativa L.) varieties were used for developing callus on Murashige and Skoog medium supplemented with 2, 4-dichlorophenoxy acetic acid (2, 4-D) (2.0 mg l−1 for Narendra 359 and 2.5 mg l−1 for Pusa Basmati 1, Taraori Basmati and Pant Sugandh Dhan 17). Screening of calli was done by sub-culturing calli for 15 days on Murashige and Skoog (MS) basal medium supplemented with different concentrations of polyethylene glycol (PEG)-6000 as chemical drought inducer. Callus volume decreased and total proline content was found to be increased significantly with increase in PEG concentration. Narendra 359 showed best response in terms of callus growth at 70 g l−1 of PEG. The highest percentage somatic embryogenesis among selected calli was observed in Pusa Basmati 1 and the lowest in Pant Sugandh Dhan 17. Excellent shooting and rooting (94%) was observed in MS + 0.1 mg l−1 naphthalene acetic acid (NAA) and MS + 2.0 mg l−1 2, 4-D. Regenerated plants were successfully acclimatized with 98% efficiency in greenhouse and grown under pot conditions up to maturity. It was observed that PEG treated somaclones accumulated more proline, chlorophyll content and developed more tiller and height than normal somaclones. Ten random amplified polymorphic DNA (RAPD) primers were used to amplify genomic DNA of somaclones of different varieties. Level of genetic polymorphism existing among these somaclones indicates that these markers can be used in breeding program for improving varieties through in vitro techniques.

Physicochemical Studies on the Interfacial and Micellization Behavior of CTAB in Aqueous Polyethylene Glycol Media

AbstractInterfacial and micellization behavior of cetyltrimethylammonium bromide (CTAB) have been studied in aqueous polyethylene glycol (PEG) mixed solvent systems of varying concentrations and molar mass. Interfacial behavior of CTAB was investigated by the equilibrium surface tension method. Conductance studies of surfactant solutions under different condition helped in determining the critical micelle concentration (CMC) and degree of dissociation of CTAB micelles. In addition, the limiting molar conductivity of surfactant and micellar species were evaluated from the differential plots. The CMC of CTAB was found to increase with increasing PEG concentration as well as its molar mass, although, the process of interfacial adsorption and micellization was found to be spontaneous, as evidenced by negative free energy change. The viscosity of CTAB micelles in aqueous‐PEG mixtures was found to increase with the increase in PEG concentration and molar mass. Dynamic light scattering measurements revealed a size enhancement effect contributed by the PEG oligomers. An increase in the CMC of CTAB and the subsequent presence of a higher number of ionic species in their dissociated form was further established by an overall increase in the zeta potential value in the presence of PEG oligomers. It is proposed that the PEG could wrap around the micelles through their conformational changes. Results also suggest that PEG oligomers could give solvophobic effect which enhances the CMC of CTAB compared to that in pure water.

Enhanced Dechlorination of Tetrachloroethylene by Zerovalent Silicon in the Presence of Polyethylene Glycol under Anoxic Conditions

The combination of zerovalent silicon (Si(0)) with polyethylene glycol (PEG) is a novel technique to enhance the dechlorination efficiency and rate of chlorinated hydrocarbons. In this study, the dechlorination of tetrachloroethylene (PCE) by Si(0) in the presence of various concentrations of PEG was investigated under anoxic conditions. Several surfactants including cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and Tween 80 were also selected for comparison. Addition of SDS and Tween 80 had little effect on the enhancement of PCE dechlorination, while CTAB and PEG significantly enhanced the dechlorination efficiency and rate of PCE by Si(0) under anoxic conditions. The Langmuir-Hinshelwood model was used to describe the dechlorination kinetics of PCE and could be simplified to pseudo-first-order kinetics at low PCE concentration. The rate constants (k(obs)) for PCE dechlorination were 0.21 and 0.36 h(-1) in the presence of CTAB and PEG, respectively. However, the reaction mechanisms for CTAB and PEG are different. CTAB could enhance the apparent water solubility of PCE in solution containing Si(0), leading to the enhancement of dechlorination efficiency and rate of PCE, while PEG prevented the formation of silicon dioxide, and significantly enhanced the dechlorination efficiency and rate of PCE at pH 8.3 ± 0.2. In addition, the dechlorination rate increased upon increasing PEG concentration and then leveled off to a plateau when the PEG concentration was higher than 0.2 μM. The k(obs) for PCE dechlorination by Si(0) in the presence of PEG was 106 times higher than that by Si(0) alone. Results obtained in this study would be helpful in facilitating the development of processes that could be useful for the enhanced degradation of cocontaminants by zerovalent silicon.

Synergistic extraction of bovine serum albumin using polyethylene glycol based aqueous biphasic system

An attempt was made to study the partitioning behaviour of bovine serum albumin (BSA) in the PEG (polyethylene glycol)–sodium citrate based aqueous two-phase system. The investigation focus on the factors that influence partitioning of BSA, including PEG molar mass (4000, 6000 and 8000), and concentration, phase forming salt concentration, pH and temperature. The concentration of the BSA was measured by Bradford method. The partition of BSA to the salt rich (bottom) phase is strongly favoured in systems with higher molar mass of PEG, due to increase in hydrophobic nature of PEG with molar mass. The partition coefficient value tends to decrease with increase in PEG concentration, due to diminution of free volume available for the protein to accommodate in the top PEG rich phase. The enhanced affinity of BSA for the PEG phase increases with increase in sodium citrate concentration, due to an increase of the salting-out effect in the bottom phase. The results indicates that BSA partitioning equilibrium is displaced to the citrate rich-phase as the system pH increases, therefore the partition coefficient value changes depending upon the isoelectric point and protein charge. Furthermore, it is observed that the BSA partitions to the bottom phase at higher temperature.

Characterization and magnetic properties of polyethylene glycol modified NiZn ferrite thin films

Polyethylene glycol (PEG) modified Ni 0.5Zn 0.5Fe 2.0O 4.0 ferrite thin films were deposited on Si (100) substrate by a sol–gel method. The crystal structure, surface morphology and magnetic properties of PEG-modified NiZn ferrite thin films (NZFs) were investigated by using the X-ray diffractometer (XRD), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM). The FTIR spectrums showed that PEG molecules were on the surface of as-prepared particles, which effectively improved their dispersibility. The crystallization of NZFs improved and crystallite size increased with increasing PEG concentration. Optimal PEG concentration could improve the surface morphology and reduce the roughness. Magnetic properties measurement indicated that compared with the sample without PEG, PEG-modified NZFs showed excellent magnetic properties with higher saturation magnetization and lower coercive force. Finally, PEG-modified NZFs showed a high saturation magnetization 312 emu/cm 3 and low coercive force 90 Oe when PEG concentration was 40 g/L.

Physicochemical characterization of gliclazide–macrogol solid dispersion and tablets based on optimized dispersion

Background: This study investigated the physical interaction of gliclazide (GLC) with a hydrophilic carrier, that is, macrogol [polyethylene glycol (PEG)]. Different molecular weights of PEG (4000, 10,000, and 20,000) were used in different drug : carrier weight ratios (1 : 1, 1 : 2, 1 : 5, and 1 : 10). Method: Preliminary screening was done by phase solubility studies to characterize the liquid state interaction between the drug and the carrier. Solid dispersions (SDs) of GLC and PEG in different ratios were prepared by fusion technique and by physical mixing. The solid-state interaction between the drug and the carrier was examined by performing differential scanning calorimetry and Fourier transform infrared spectroscopic studies. SD with satisfactory characteristics was selected for the formulation of tablets by wet granulation method and compared with the commercial brand for in vitro dissolution. Results: It was evident from phase solubility studies that the drug solubility increased linearly with increasing PEG concentrations. In vitro dissolution of GLC improved significantly in the SDs prepared by fusion method as compared with the original drug and physical mixtures. Scanning electron microscopy images showed well-defined changes in the surface topography of GLC, thus confirming the effective formation of a fused binary system. The SD tablets showed a significant improvement in the drug release profile than that of the commercial brand. Conclusion: It was thus concluded that SD formulations of GLC can be successfully used to design a solid dosage form of the drug, which would have significant advantages over the current marketed tablets.

Synthesis and characterization of polyethersulfone membranes

Phase inversion method was used to prepare polyethersulfone (PES) ultrafiltration (UF) membranes. Polyethylene glycol (PEG); N, N-dimethyl formamide (DMF) and water were utilized as pore-forming additive, solvent and non-solvent, respectively. Effects of PES and PEG concentrations in the casting solution, PEG molecular weight (MW) and coagulation bath temperature (CBT) on morphology of the prepared membranes were investigated. Taguchi experimental design was applied to run a minimum number of experiments. 18 membranes were synthesized and their permeation and rejection properties to pure water and human serum albumin (HSA) solution were studied. It was found out that increasing PEG concentration, PEG MW and CBT, accelerates diffusional exchange rate of solvent (DMF) and non-solvent (water) and consequently facilitates formation of macrovoids in the membrane structure. The results showed that, increasing PES concentration, however, slows down the demixing process. This prevents instantaneous growth of nucleuses in the membrane structure. Hence, a large number of small nucleuses are created and distributed throughout the polymer film and denser membranes are synthesized. A trade-off between water permeation and HSA rejection was involved, with membranes having higher water permeation exhibited lower HSA rejection, and vice versa. Hence, optimizing preparation variables to achieve high pure water permeation flux along with reasonable HSA rejection was inevitable. Analysis of variance (ANOVA) showed that all parameters have significant effects on the response (water flux and HSA rejection). However, CBT and PES concentration were more influential factors than PEG concentration and MW on the responses.

Effect of preparation variables on morphology and pure water permeation flux through asymmetric cellulose acetate membranes

In this study, cellulose acetate (CA) ultrafiltration (UF) membranes were prepared using the phase inversion method. Effects of CA and polyethylene glycol (PEG) concentrations in the casting solution and coagulation bath temperature (CBT) on morphology of the synthesized membranes were investigated. Based on L 9 orthogonal array of Taguchi experimental design 18 membranes were synthesized (with two replications) and pure water permeation flux through them were measured. It was found out that increasing PEG concentration in the casting solution and CBT, accelerate diffusional exchange rate of solvent 1-methyl-2-pyrrolidone (NMP) and nonsolvent (water) and consequently facilitate formation of macrovoids in the membrane structure. Increasing CA concentration, however, slows down the demixing process. This prevents instantaneous growth of nucleuses in the membrane structure. Hence, a large number of small nucleuses are created and distributed throughout the polymer film and denser membranes are synthesized. Rate of water flux through the synthesized membranes is directly dependent on the size and number of macrovoids in the membrane structure. Thus, maximum value of flux is obtained at the highest levels of PEG concentration and CBT (10 wt.% and 23 °C, respectively) and the lowest level of CA concentration (13.5 wt.%). Analysis of variance (ANOVA) showed that all parameters have significant effects on the response. However, CBT is the less influential factor than CA and PEG concentrations on the response (flux).

Gas permeation properties of polyvinylchloride/polyethyleneglycol blend membranes

AbstractIn this study, the effect of the molecular weight of polyethyleneglycol (PEG) on the gas permeability and selectivity of a series of polyvinylchloride/polyethyleneglycol (PVC/PEG) blend membranes was investigated. The molecular weight of polyethylene glycol ranged from 400 to 4000. PVC/PEG blend membranes were prepared via thermal phase inversion of PVC/PEG/dimethylformamide solution at 60°C. The permeabilities of pure CO2, CH4, O2, and N2 gases through prepared membranes were determined at room temperature (25°C) and 20 bar feed pressure. The blend membranes having PEG with 4000 molecular weight showed higher values of CO2 permeability, and CO2/CH4 and CO2/N2 ideal selectivities (the ratio of pair gas permeabilities) compared with other blend membranes containing PEGs of lower molecular weights. It was also found that the gas permeabilities of PVC/PEG4000 blend membrane rapidly increased with an increase in PEG concentration (weight fraction). The PVC/PEG blends containing 10, 20, and 30 wt % of PEG4000 showed CO2 permeabilities equal to 0.84, 2.38, and 5.82 Barrer (1 Barrer = 10−10 cm3 (STP) cm/cm2 s cmHg), respectively. The CO2/N2 ideal selectivities of 10, 20, and 30 wt % of PEG4000/PVC blend membranes were 49, 70, and 109, respectively. This is a great improvement compared with the pure PVC membrane, which showed CO2 permeability and CO2/N2 ideal selectivity of 0.13 Barrer and 14.5, respectively. These results and comparison of CH4 and N2 permeabilities of PVC membrane and PVC/PEG blend membranes indicated that the gas solubility is dominant in the permeation of gases through abovementioned blend membranes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Effects of Water Stress on Respiration, Photosynthetic Pigments and Water Content in Two Maize Cultivars

Water stress is one of the most important environmental factors that reduce growth, development and production of plants. Stress was applied with polyethyleneglycol (PEG) 6000 and water potentials were: zero (control), -0.15 (PEG 10%), -0.49 (PEG 20%), -1.03 (PEG 30%) and -1.76 (PEG 40%) MPa. The roots and leaves respiration of two maize (Zea mays L.) cultivars -704 and 301- were determined in various concentrations of PEG 6000. Oxygen uptake declined in leaves and roots with increasing PEG concentrations. Decrease of oxygen uptake in roots and leaves of 704 variety were higher than 301 variety. Chlorophyll a, b and total chlorophyll content were significantly decreased (p < 0.05), but carotenoids content increased (p < 0.05) under water stress. Decrease of chlorophyll content in 704 var. was higher than 301 var., but carotenoids content in 301 var. was higher than 704 var. Relative Water Content (RWC) was used to indicate the degree of stress. RWC decreased with increasing PEG concentrations. Lowering of RWC reduced growth and increased shoot/root ratio. Decrease of water content in 704 plants was higher than 301 plants. Shoot/root ratio in 704 var. was higher than 301 var.

Stabilization of the anatase phase in TiO 2(Fe 3+, PEG) nanostructured coatings

Multilayered TiO 2(Fe 3+, PEG) films were deposited on glass and SiO 2/glass substrates by sol–gel dipping method. The influence of Fe 3+ and PEG(polyethylene glycol) concentrations, the number of layers, the thermal treatment time and the temperature on the optical and microstructural properties of the TiO 2 films were studied. As-deposited TiO 2(Fe 3+, PEG) films were very porous, but after the thermal treatment at 500 °C, the PEG decomposed and burned out to porosity decreasing. Homogeneous nanostructured films were obtained, where the amorphous and the anatase phases coexist. XRD analysis showed that no rutile phase is observed in the films deposited on SiO 2/glass as compared with those deposited directly on glass and that the presence of the anatase phase in the films without PEG is more evident in the three-layers film. The XRD intensity of the main peak of anatase from 25° decreases with the increase of PEG concentration. The optical gap of the TiO 2(Fe 3+, PEG) films is found in 2.52–2.56 eV range and does not essentially depend on the PEG content.

PEG(polyethylene glycol) 농도와 PEG/Gly(glycerol) 흔합비에 따른 견 피브로인 필름의 물성

To study the effects of plasticizer concentration and its ratio on the physical properties of silk fibroin films, polyethylene glycol (PEG) was used at 4 different concentrations; 1, 2, 3, (w/v). Tensile strength (TS) and water vapor permeability (WVP) increased with the increase of PEG concentration, while opposite trend was observed for percent elongation of silk fibroin films. WVP of silk fibroin films increased from for of PEG to for . In addition, a mixture of PEG and glycerol (Gly) as a plasticizer was used at the ratio of 100:0, 75:25, 50:50, 25:75, and 0:100 (w/w). Percent elongation of the films was improved to when the ratio of 75:25 was used. On the contrary, WVP of silk fibroin films increased with the decrease of the ratio of PEG:Gly. Effect of the plasticizer concentration and its ratio on the color of silk fibroin films was negligible. These results suggest that mixture of PEG and Gly as a plasticizer provide more flexible than PEG alone in silk fibroin films, and the best ratio of PEG to Gly was 75:25.

Preparation and photo-catalytic activity of FeTiO 2 thin films prepared by sol–gel dip coating

Thin films of iron (Fe) doped titanium dioxide (FeTiO 2) were prepared on a variety of substrates by using Ti-peroxy sol–gel dip coating method. The surface structure of the film was modified by adding different concentrations of polyethylene glycol (PEG) into the TiO 2 sol. Most of the metal ion doped entered TiO 2 lattice resulting the shift in optical absorption edge towards visible side. Addition of PEG alters the surface morphology and structure of the films. The increase in concentration of PEG increases the number and size of the pores on surface of the film by decomposition of PEG when the films are subjected to heat treatment. The adsorbed hydroxyl content of such porous films is found to increase with amount of PEG added. Photo-catalytic properties of the surface modified and Fe ion doped TiO 2 catalyst was investigated by degradation of methyl orange in sunlight. The photo-catalytic activity of the PEG added FeTiO 2 catalyst was enhanced by 2–2.5 times than undoped TiO 2.

Biophoton Emission Induced by Osmotic Stress in Adzuki Bean Root

In order to evaluate the physiological damage to plants caused by osmotic stress, we have investigated the relationship between the inhibition of root elongation and spontaneous photon emission from the root. Adzuki bean roots were soaked in polyethylene glycol (PEG) solutions for short periods in their early growth stage, and their root length and photon emission were measured afterwards. Consequently, it became clear that the root elongation decreased with the increase of PEG concentration. Moreover, there was a clear correlation between the emission intensity of the cell division area in the root and the inhibition of elongation, though the elongation of individual roots varied to some degree.

Purification of xylose reductase from Candida mogii in aqueous two-phase systems

Xylose reductase (XR) from Candida mogii was extracted by partitioning in aqueous two-phase systems (ATPS) composed of polyethylene glycol (PEG) and phosphate salts. An experimental design was used to evaluate the influence of the variables molar mass of PEG ( A), concentration of PEG ( B), concentration of phosphate ( C), and concentration of NaCl ( D) on XR extraction. The positive effect of variable B and the negative effect of A and of the interaction between A and B on the purification factor in the top phase (PF T) indicated that a simultaneous increase in PEG concentration with a decrease in molar mass of PEG leads to an increase in that response. Phosphate concentration also had a negative effect, indicating an increase in PF T with a decrease in its value. A linear model fitted to the data indicated the need to change the ranges of the variables. In a second experimental design, the influence of a lower range of PEG molar mass (MMPEG) and of tie-line length (TLL) on the partitioning of XR was studied. Quadratic models were predicted for the responses purification factor in the top phase and XR yield in the top phase ( Y T), and the maximum values predicted by these models were 1.59±0.40 and 105.8±26.2%, respectively. A 19-fold increase in the selectivity factor was experimentally achieved for a system with PEG 1000 and TLL 34. The k, PF T and Y T values corresponding to 21.21, 1.89 and 103.5 respectively were also obtained under these experimental conditions.

Rheological properties of reversible thermo-setting in situ gelling solutions with the methylcellulose?polyethylene glycol?citric acid ternary system

The composition of vehicle on the reversible sol-gel transition temperature in a ternary system made up of methylcellulose (MC), polyethylene glycol (PEG), and citric acid (SC) was investigated. The properties of the in situ gelling system were estimated by rheological measurement. When PEG (4000) concentration was varied from 0% to 10% while MC (SM25) and SC concentrations were kept constant at 1.5% and 3.5%, respectively, the reversible sol-gel transition temperature lowered from 38 °C to 26 °C with increasing PEG concentration. However, the extent of lowering in temperature was not influenced by the molecular weight of PEG. The reversible sol-gel transition temperature shifted towards the lower temperature with increasing MC concentration, and towards the higher temperature with decreasing pH. Comparison of rheological properties between the present thermo-setting in situ gelling solution and a conventional one, such as gellan gum solution or Poloxamer 407 solution, revealed that the present solution radically differed from the conventional solutions in the incipient gelling mechanism. These findings suggest that the ternary system in this study would be useful as a drug delivery system for instillation of drugs into the eye.

In vitro quality assessment of two tropical shrub legumes in relation to their extractable tannins contents.

The in vitro dry matter digestibility (IVDMD) of the two leguminous tree fodders Gliricidia sepium and Calliandra calothyrsus which differ in their tannin content was examined by the rumen simulation technique. Extractable condensed tannin (CT) concentrations ranged from 0.57% in G. sepium to 5.05% in C. calothyrsus using the butanol-HCl extraction. On the basis of their respective CT contents, G. sepium was classified as containing traces of CT, whereas C. calothyrsus had medium amounts of CT. Polyethylene glycol (PEG) was added at different concentrations (0, 1.5, 5 and 10 g/100 g plant material substrate) to assess the effect of tannins on IVDMD. The IVDMD was higher for G. sepium (range: 60-65%) than for C. calothyrsus (39.5-53.5%). In vitro gas production and IVDMD increased with increased PEG concentrations especially for C. calothyrsus. A non-significant response to increasing PEG concentrations for IVDMD of G. sepium confirms PEG binding with the tannins. On the basis of these results, it is assumed that G. sepium has a higher nutritive value than C. calothyrsus. Good relationship between PEG binding and the improvement of IVDMD confirms the usefulness of this technique for improving the nutritive value of tanniniferous tropical browses.

Carbohydrate status during somatic embryo maturation in Norway spruce

The development of Norway spruce (Picea abies (L.) Karst.) somatic embryos on a maturation medium was accompanied by changes in nonstructural carbohydrate status. During embryo maturation, the content of total soluble sugars in the embryonal suspensor mass decreased and the partitioning between sucrose and hexoses changed considerably in favor of sucrose. Developing somatic embryos were mainly responsible for these changes. Osmotic stress caused by the presence of 3.75% polyethylene glycol (PEG) in the maturation medium (decrease in osmotic potential by 52.5 kPa) resulted in dramatic changes in the content of endogenous saccharides. There was a lower total carbohydrate content in the embryonal suspensor mass grown on the medium containing PEG in comparison with the untreated control. Isolated embryos from later stages of embryo development contained mainly sucrose with a small amount (20%) of fructose and nearly no glucose. A further increase in PEG concentration in the medium (7.5%; decrease in osmotic potential by 112.5 kPa compared to the maturation medium) led to a large increase in the total endogenous sugar content. This increase in sugars was a result of the enhanced content of sucrose, fructose, and glucose. The increased glucose content was in contrast to embryos grown on the medium with lower or no PEG content.

Effect of solute concentration on hindered diffusion in porous membranes

AbstractThe effect of solute concentration on hindered diffusion was investigated by measuring diffusion rates of dextran and polyethylene glycol (PEG) in track‐etched polycarbonate membranes at concentrations up to 60 mg/mL. Results were interpreted using a model that incorporates a first‐order virial coefficient to describe the concentration dependence of the equilibrium partition coefficient, as well as the intrapore diffusivity. For dextran, both virial coefficients were positive, indicating that the effective diffusivity increases with solute concentration. Measured values of the virial coefficient for equilibrium partitioning agreed with a model that includes attractive van der Waals interactions between dextran and the pore wall. For PEG, both virial coefficients were negative, indicating that the diffusivity decreases as solute concentration increases. These observations may be due to chain entanglement or aggregation that occurs with increasing PEG concentration.

Elongational flow studies of the conformation of DNA molecules in the globular state

Elongational flow-induced birefringence of a T4-phage DNA aqueous solution was measured with changing NaCl and polyethylene glycol (PEG) concentrations. DNA molecules are known to manifest a coil–globule transition with increasing PEG concentration. At certain PEG concentrations near the critical concentration of the transition, the globular DNA solution, which was expected to be nonbirefringent, showed flow-induced birefringence. Strain-rate dependence of the birefringence intensity, having a critical strain rate, was similar to that of the flexible polymer chain that manifests the coil–stretch transition. The flow-induced birefringence pattern, however, suggested that the globular DNA molecules were rigid and optically anisotropic. At the critical strain rate, the globular DNA molecules in the solution of the particular PEG concentration were considered to collapse nonadiabatically to an optically anisotropic and mechanically rigid conformation. The overall shape of the collapsed conformation of the globular DNA was estimated to be an ellipsoid with an aspect ratio of about 0.7. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1351–1358, 2000