PEG Molecular Mass Research Articles

Effect of PEG molecular mass and HEMA capping on the thermal, morphological, and hydrophilic properties of ısocyanate-terminated polyurethane acrylate films

Effect of PEG molecular mass and HEMA capping on the thermal, morphological, and hydrophilic properties of ısocyanate-terminated polyurethane acrylate films

Partitioning and recovery of proteases from lizardfish (Saurida micropectoralis) stomach using combined phase partitioning systems and their storage stability.

Partitioning and recovery of proteases from stomach extract (SE) and acidified stomach extract (ASE) of lizardfish using a three-phase partitioning (TPP) system in combination with an aqueous two-phase system (ATPS) was optimized. The highest yield and purity were obtained in the interphase of the TPP system, which consisted of a SE or ASE to t-butanol ratio of 1.0 : 0.5 in the presence of 40% (w/w) (NH4)2SO4. Both TPP fractions were further subjected to ATPS. Phase compositions of ATPS including PEG molecular mass and concentrations as well as types and concentrations of salts influenced protein partitioning. The best ATPS conditions for protease partitioning into the top phase from TPP fractions of SE and ASE were 15% Na3C6H5O7-20% PEG1000 and 20% Na3C6H5O7-15% PEG1000, which increased the purity by 4-fold and 5-fold with the recovered activity of 82% and 77%, respectively. ATPS fractions of SE and ASE were subsequently mixed with several PEGs and salts for back extraction (BE). BE using 25% PEG8000-5% Na3C6H5O7 gave the highest PF and yield for both ATPS fractions. SDS-PAGE investigation revealed that the decrease in contaminating protein bands was observed after the combined partitioning systems. BE fractions of SE and ASE were quite stable at -20 and 0 °C up to 14 days. Therefore, the combination of TPP, ATPS and BE could be effectively applied to recover and purify proteases from the stomach of lizardfish.

Structural investigations of poly(ethylene glycol)-dodecylbenzenesulfonic acid complexes in aqueous solutions

Abstract The structures arising in mixed colloidal solutions of anionic surfactant dodecylbenzenesulfonic acid (DBSA) and neutral poly(ethylene glycol) (PEG) polymer in water for a wide range of concentrations and different molecular masses of the polymer were studied by small-angle neutron scattering (SANS) and dynamic light scattering (DLS). The micellization behavior of the system near the critical micelle concentration was characterized by fluorescence spectroscopy and measurements of the surface tension of the solutions. The assumption of the coexistence of free micelles, surfactant-polymer complexes in the form of a necklace structure, and polymer coils was confirmed by DLS and SANS. The typical sizes of micelles and complexes were estimated. It was found that there is an impact of PEG molecular mass on the ability of multi-micelle complex formation. The obtained results are important in particular for the PEGylation of magnetic nanoparticles in sterically stabilized aqueous ferrofluids.

Extractive Fermentation for Process integration and amplified pullulan production by A. pullulans in Aqueous Two Phase Systems

Extractive fermentation technique or in situ product recovery process is a novel technique to segregate the desired product simultaneously in a fermentation process. For economic and high yield production of pullulan, Extractive fermentation process was applied fermentation process of A. pullulans. Aqueous Two Phase system (ATPS) systems were designed with various molecular mass of PEG (400, 600, 4000 and 6000) and dextran or mono/bi-sodium phosphate salts. Systems with short Tie Line length (TLL) 6.7 and 7.5% w/w for PEG-Salt and PEG-dextran respectively were chosen. Volume ratio for all the systems was kept constant at 1.0 and pH 7.0 for PEG-dextran and PEG-NaH2PO4 was maintained, whereas pH 9.0 was kept for PEG-Na2HPO4. A. pullulans, was found to be viable with PEG-NaH2PO4 and PEG-dextran systems. The biomass partitioned in the PEG rich top phase and the exopolysaccharide pullulan shown affinity towards the bottom phase. A maximum yield (36.47 g/L) was found with PEG 4000-Dextran 500 system of extractive fermentation process. The proposed process aptly integrates upstream and downstream process for continuous production and recovery of pullulan from the biomass, thus reducing the time quotient of the whole process.

New poly(ester-amide) copolymers modified with polyether (PEAE) for anticancer drug encapsulation

New poly(ester–amide) copolymers modified with polyethers were developed for carboplatin encapsulation. These new copolymers contain hydrophobic blocks made of tyrosine derivative and dimer fatty acid, and poly(ethylene glycol) (PEG) as hydrophilic blocks. Short-term hydrolytic degradation revealed high water absorption, slight increase of pH of simulated body fluid and change of sample shape, which indicated the erosive mechanism of polymers degradation. Poly(ester-amide)-PEG copolymers were used for microspheres preparation and carboplatin encapsulation. A double emulsification process was used to produce microspheres with an average diameter of 20–30 μm. It was found that the amount of drug released was controlled by the molecular mass of PEG used for microspheres preparation. Mathematical models were used to elucidate the release mechanism of the carboplatin from the microspheres. The results demonstrate that poly(ester-amide)-PEG copolymers may be used for targeted carboplatin encapsulation and release.

Use of response surface methodology for partitioning, one-step purification of alkaline extracellular lipase from Penicillium candidum (PCA 1/TT031).

This report shows the partitioning and purification of alkaline extracellular lipase from Penicillium candidum (PCA 1/TT031) by solid-state fermentation (SSF). In the present analysis, some of the important parameters such as PEG concentration, PEG molecular mass, salt concentration and buffer concentration were optimised through the response surface methodology (RSM). The optimum aqueous two-phase systems (ATPS) environment consisted of 13.8% (w/w) phosphate buffer, 9.2% (w/w) PEG-3000 and 3.3% (w/w) NaCl at 25°C. The RSM approach was proved to be the most suitable methodology for the recovery of desired enzymes. In this method, the enzyme partitioned into the top phase of the PEG-buffer-NaCl ATPS. Under this experimental environment, the purification factor was found to be 33.9, the partition coefficient was 4.0 and the yield was found to be 84.0% of lipase. Moreover, the experimental and predicted results were in considerable agreement, which established the reliability and validity of the proposed model. The ATPS methodology is proven to be effective for the primary recovery of lipase at a low cost with a large loading capacity and possibility of linear scale up. In addition to using the existing methodologies for improving enzyme production, the use of statistical optimisation of the constituents of phases through RSM continues to be the basic and practical method.

Effect of PEG Addition on the Properties of YAG:Ce Phosphor Synthesized via a Homogeneous Precipitation Method

Abstract YAG:Ce precursors were synthesized via a homogeneous precipitation method with the addition of different molecular mass of PEG (PEG 6000 and PEG 10000) used as dispersant. The FT-IR spectra show that no significant difference is found between the precursors. SEM images indicate that the size of the primary particles with PEG is much smaller than that of the sample without PEG. Confirmed by the DSC traces and X-ray diffraction (XRD), the crystallization of YAG is a one-step process without any intermediate phase. The crystallization of YAG is significantly promoted and the oxidation of Ce3+ is inhibited by addition of PEG, which enhances the luminescent properties of YAG:Ce phosphor.

Synergistic effect of anionic and nonionic monomers on the synthesis of high solid content waterborne polyurethane

High solid content waterborne polyurethane dispersions (PUDs) were synthesized via to the combination of ionic and nonionic monomers, in which the effect of the molecular mass of poly (ethylene glycol) (PEG) and its connection relationships of those hydrophilic groups in polyurethane with dimethylol propionic acid (DMPA) (through changed the synthetic schemes of PUDs) were researched. It is found that the molecular mass of PEG has obvious effect on combining with DMPA to synthesize PUDs. The incorporation of small molecular mass PEG200 (Mn = 200) had little effect on improving the dispersion and stability properties of anionic PUDs. But as the molecular mass of PEG increasing, they (PEG400, PEG600, PEG1000 and PEG2000) have obvious effect on improving the dispersion and stability properties, and can decrease the required dosage of DMPA to stabilize PUDs, moreover, cam improve the solid content of the latex. However, the effect of PEG2000 is less prominent than that of PEG400, PEG600 and PEG1000. The connection relationships of PEG with DMPA also have a certain effect on the property of the latex. When the small molecular mass one (PEG400) directly connects with DMPA, the synergistic effort is enhanced and the required dosage of DMPA to stabilize latex decreases to 2.0% (using DMPA alone needs 2.4%). As a result, the solid content of PUDs increased from 42% (using DMPA alone) to 52%, and the water resistance of PUDs is also improved. The thermal, dynamic mechanical and tensile-strength properties of derived films of PUDs were also analyzed, and the results show the incorporating PEG into polyurethane decrease the glass transition temperature of soft segments (Tgs), as well decreases the crystallinity and the extent of phase separation, which both cause the decrease of heat resistance. But through the combination, the synthetic formulas of PUDs with better tensile strength and elongation ratio than using DMPA alone were obtained. Besides, it is found that the molecular mass of PEG and the connection relationships of PEG with DMPA also had some influence on the properties of the derived films.

Stabilization of copper nanoparticles prepared by reduction from solutions of poly(acrylic acid) complexes with Cu2+ ions and poly(ethylene glycols)

Copper sols are prepared via the reduction of copper ions with hydrazine borane in dilute aqueous solutions of mixtures of the PAA-Cu2+ complex and poly(ethylene glycols) of various molecular masses at PEG: PAA = 0.25 base-mol/base-mol and PAA: Cu2+ = 10 base-mol/mol in the pH range 4.0–7.0. The stability of sols against oxidation (dissolution) or aggregation (enlargement) of metal nanoparticles is much higher than that of sols prepared in the absence of PEG. With an increase in the initial pH or a decrease in the molecular mass of PEG, the formed copper nanoparticles are much larger (no less than 20 nm in diameter) than copper nanoparticles occurring in the sol prepared in a solution of the PAA double complex with Cu2+ ions and high-molecular-mass PEG at a low initial pH (3–10 nm in diameter). Copper nanoparticles in sols prepared in solutions of complexes based on the high-molecular-mass PEG do not aggregate during exposure, thereby indicating the high stability of polymer screens on their surfaces.

Effect of particle size on salt-induced diffusiophoresis compared to Brownian mobility.

For ternary polymer-salt-water systems at low polymer concentration (0.5%, w/w), we have experimentally investigated the effect of polymer size on polymer diffusiophoresis (i.e., polymer migration induced by a salt concentration gradient) and salt osmotic diffusion (i.e., salt migration induced by a polymer concentration gradient). Specifically, Rayleigh interferometry was employed to measure ternary diffusion coefficients for aqueous solutions of poly(ethylene glycol) (PEG) and KCl at 25 °C. Our investigation focused on four polymer molecular masses (from 10 to 100 kg mol(-1)) and two salt concentrations (0.25 and 0.50 M). To describe and examine our experimental results, we introduced a normalized diffusiophoresis coefficient as the ratio of polymer diffusiophoresis to polymer Brownian mobility. This coefficient was found to increase with polymer molecular mass, thereby demonstrating that the relative importance of polymer diffusiophoresis compared to its intrinsic Brownian mobility increases with particle size. The observed behavior was linked to preferential hydration (water thermodynamic excess) and hydration (bound water) of the macromolecule. The ratio of salt osmotic diffusion to binary salt-water diffusion approximately describes the nonuniform spatial distribution of salt along a static polymer concentration gradient at equilibrium. The significance of polymer diffusiophoresis, especially at high PEG molecular mass, was examined by considering a steady-state diffusion problem showing that salt concentration gradients can produce large enhancements and depletions of polymer concentration. This work is valuable for understanding and modeling the effect of salt concentration gradients on diffusion-based transport of polymers with applications to interfacial processes.

Complement activation by PEG-functionalized multi-walled carbon nanotubes is independent of PEG molecular mass and surface density

Carboxylated (4%) multi-walled carbon nanotubes were covalently functionalized with poly(ethylene glycol)1000 (PEG1000), PEG1500 and PEG4000 with a PEG loading of approximately 11% in all cases. PEG loading generated non-uniform and heterogeneous higher surface structures and increased nanotube width considerably, but all PEGylated nanotube species activated the complement system in human serum equally. Increased PEG loading, through adsorption of methoxyPEG2000(or 5000)-phospholipid conjugates, generated fewer complement activation products; however, complement activation was never completely eliminated. Our observations address the difficulty in making carbon nanotubes more compatible with innate immunity through covalent PEG functionalization as well as double PEGylation strategies. From the Clinical EditorComplement-mediated toxicity is a major limiting factor in certain nanomedicine applications. This study clarifies that PEGylation of carbon nanotubes is unlikely to address this complication.

Efeitos do pH e massa molar do polímero sobre o sistema bifásico aquoso PEG/fosfato

Liquid-liquid extraction using aqueous two-phase systems (ATPSs) is a promising technique for the purification of biomolecules of industrial and laboratory interest. This work presents a study of the phase diagrams for different poly(ethylene glycol) (PEG) molar masses (ranging from 400 to 4000) and potassium phosphate at pH varying from 6 to 11 in standard conditions. The influence of PEG molecular mass at different pHs was studied from the phase diagrams formed. Stock solutions of PEG 400 and 4000 (100 and 50% w w -1 , respectively) and phosphate (20% w w -1 KH 2 PO 4 /K 2 HPO 4 ) were prepared at the appropriate pH (6, 7, 8 and 9). For pHs 10 and 11, NaOH 1M was used in addition to the salts. The results showed that low concentrations were used to form the ATPS with high molecular mass PEG. On the other hand, there was no pH influence in the equilibrium curves – in other words, a significant shift of the binodal in different pHs.

Aspergillus oryzae alpha-amylase partition in potassium phosphate-polyethylene glycol aqueous two-phase systems

The aim of this work is to study the partitioning of alpha-amylase from Aspergillus oryzae in polyethylene glycol-potassium phosphate systems formed by polymers of different molecular masses with different total concentrations, several NaCl concentrations and different volume ratio between the phases and at different temperatures. The enzyme was partitioned towards the top phase in the 2000-molecular-mass polyethylene glycol systems and towards the bottom phase in the other systems analyzed with higher molecular mass. The protein–medium interaction parameter (A) was determined; it increased in the same way as PEG molecular mass. The enthalpic and entropic changes found, in general, were negative and were shown to be associated by an entropic–enthalpic compensation effect suggesting that the ordered water structure in the chain of polyetyleneglycol plays a role in protein partition. The recovery in each of the phases was calculated in order to choose the best systems to be applied to enzyme isolation either from a polymer-rich or a polymer-poor phase.Enzymatic activity, circular dichroism and fluorescence were studied for the protein alone and in the presence of the different phases of the aqueous two-phase systems (ATPSs) in order to understand how they affect the enzymatic structure and the role of the protein-polymer interaction in the partitioning process. Secondary structure is not affected, in general, by the presence of the phases that do affect the enzymatic activity; therefore, there should be a change in the tertiary structure in the enzyme active site. These changes are more important for PEG 8000 than for PEG 2000 systems according to the results of the quenching of the intrinsic fluorescence. In a bio-separation process, the A. oryzae alpha-amylase could be isolated with ATPSs PEG 2000/Pi or PEG 8000/Pi with a high recovery, in the top or bottom phases, respectively.

Sizing the Bacillus anthracis PA 63 Channel with Nonelectrolyte Poly(Ethylene Glycols)

Nonelectrolyte polymers of poly(ethylene glycol) (PEG) were used to estimate the diameter of the ion channel formed by the Bacillus anthracis protective antigen 63 (PA 63). Based on the ability of different molecular weight PEGs to partition into the pore and reduce channel conductance, the pore appears to be narrower than the one formed by Staphylococcus aureus α-hemolysin. Numerical integration of the PEG sample mass spectra and the channel conductance data were used to refine the estimate of the pore's PEG molecular mass cutoff (∼1400 g/mol). The results suggest that the limiting diameter of the PA 63 pore is <2 nm, which is consistent with an all-atom model of the PA 63 channel and previous experiments using large ions.

Partitioning of Poly(ethylene oxide), Poly(ethylene imide), and Bovine Serum Albumin in Isobutyric Acid + Water

We present new measurements of the partitioning of the polymers (poly(ethylene glycol) (PEG) and poly(ethylene imine) (PEI)) and the protein bovine serum albumin (BSA) between coexisting liquid phases of isobutyric acid + water. We show that all partition unevenly between the liquid phases: In all cases, there is substantially more polymer or protein in the upper, isobutyric acid-rich phase. At molecular masses above about 10 kg/mol, PEG and PEI fractionate between the liquid phases, with a higher average molecular mass in the lower, water-rich phase. The fractionation and partitioning are amplified both when the molecular mass of the polymer is increased, and when D2O + isobutyric acid is used instead of H2O + isobutyric acid. The dependence of the distribution coefficient on molecular mass disagrees with the predictions of Flory−Huggins mean field theory for all PEG and PEI systems studied. At low molecular weight, the PEG fractionations are consistent with theoretical predictions that the molecular mass distributions of the daughter phases will have the same mathematical forms as the parent phase. However, as the average molecular mass increases, the PEG molecular mass distributions of the daughter phases differ from those of the parent phases. The critical temperature, Tc, of PEG + isobutyric acid + H2O increases approximately linearly with PEG concentration, increases nonlinearly with PEG average molecular mass, and is independent of the terminating group.

Binding Mechanisms of PEGylated Ligands Reveal Multiple Effects of the PEG Scaffold

A series of synthetic ligands consisting of poly(ethylene glycol) (PEG), capped on one or both ends with the hapten 2,4-dinitrophenyl (DNP), were previously shown to be potent inhibitors of cellular activation in RBL mast cells stimulated by a multivalent antigen [Baird, E. J., Holowka, D., Coates, G. W., and Baird, B. (2003) Biochemistry 42, 12739-12748]. In this study, we systematically investigated the effect of increasing length of the PEG scaffold on the binding of these monovalent and bivalent ligands to anti-DNP IgE in solution. Our analysis reveals evidence for an energetically favorable interaction between two monovalent ligands bound to the same receptor, when the PEG molecular mass exceeds approximately 5 kDa. Additionally, for ligands with much higher molecular masses (>10 kDa PEG), the binding of a single ligand apparently leads to a steric exclusion of the second binding site by the bulky PEG scaffold. These results are further corroborated by data from an alternate fluorescence-based assay that we developed to quantify the capacity of these ligands to displace a small hapten bound to IgE. This new assay monitors the displacement of a small, receptor-bound hapten by a competitive monovalent ligand and thus quantifies the competitive inhibition offered by a monovalent ligand. We also show that, for bivalent ligands, inhibitory capacity is correlated with the capacity to form effective intramolecular cross-links with IgE.

Solute–solvent interactions within aqueous poly(ethylene glycol): solvatochromic probes for empirical determination and preferential solvation

Due to their vast industrial importance, poly(ethylene glycols) [PEGs] have become substances of major investigations. The hypothesis that aqueous PEG rather than pure PEG may provide substantially improved physicochemical properties for many industrial applications is addressed. Solvatochromic electronic absorbance probes are utilized to gather important information about these systems. Response from a water-soluble betaine dye suggests a decrease in dipolarity/polarizability and/or hydrogen-bond donating (HBD) acidity as the PEG is added to water. This is further confirmed by the response of N,N-diethyl-4-nitroaniline, which shows a decrease in dipolarity/polarizability and, in concert with the response from the betaine dye, a decrease in HBD acidity as the amount of PEG is increased. Response from 4-nitroaniline combined with dipolarity/polarizability is used to show that hydrogen-bond accepting (HBA) basicity increases with the addition of PEG to water. The extent of change in these important physicochemical properties depends on the PEG molecular mass. A simple mole-fraction weighted solvation model suggests significant preferential solvation of the betaine dye by PEG molecules in aqueous PEG solutions.

Extraction and determination of morphine in compound liquorice using an aqueous two-phase system of poly(ethylene glycol)/K 2HPO 4 coupled with HPLC

An aqueous two-phase system (ATPS) of poly(ethylene glycol) (PEG)/K 2HPO 4 coupled with high performance liquid chromatography (HPLC) method was developed for the separation and determination of morphine in compound liquorice. Morphine and its analogs were used as model compounds to investigate influence of various factors on extraction behaviors of ATPS, such as the types and concentrations of salts, PEG molecular mass, temperature and pH. It was observed that the types of salt had much influence on extraction efficiencies of morphine and its analogs. The results indicated that hydrophobic force cooperating with hydrogen bond interaction between analytes and phases played important role in extraction process. In the optimal system of containing 0.5 g PEG2000 and 1.5 g K 2HPO 4, the recoveries of the spiked standards for the analytes were all 91.7–100.3% with relative standard deviation of 1.0–3.0%. Morphine in compound liquorice was determined by the proposed method and the results were consistent with those of LC–MS method. Compared with conventional liquid–liquid extraction or solid-phase extraction, this extraction method can be completed in one operation and is low-cost. Since the entire extraction process is organic solvent-free, this new technique is environmental friendly.

The effect of methoxy-PEG chain length and molecular architecture on lymph node targeting of immuno-PEG liposomes

The rate of drainage and lymphatic distribution of subcutaneously injected liposomes is controlled by inclusion of methoxypoly(ethyleneglycol), mPEG-phospholipid into the liposomal bilayer. The effect is most dramatic with liposomes containing 15 mol% mPEG-lipid, with an average PEG molecular mass of 350 Da. These vesicles are drained rapidly from the injection site into the initial lymphatics when compared to unmodified liposomes, and are retained more favourably by the scavengers of the regional lymph node. Liposomes decorated with longer surface mPEG chains (6.7 mol% of mPEG 2000-lipid) exhibit faster drainage rates than vesicles having 15 mol% mPEG 350-lipid in their lipid bilayer, but their lymph node retention is very poor. The lymph node retention of rapidly drained PEG-bearing vesicles was increased dramatically following conjugation of a non-specific IgG to the distal end of PEG, using a functionalized PEG 2000 lipid. Adjusting the molecular architecture of surface mPEG and IgG-PEG chains to a “nearly overlapped mushroom” regime further enhanced target recognition of immuno-PEG 2000 liposomes without compromising their drainage rate from the interstitium. The lymph node retention of these vesicles was further optimized by enriching their lipid bilayer with 20 mol% phosphatidylserine. These approaches have established important compositional and structural variables that control lymphatic targeting of immuno-PEG liposomes and their application in experimental medicine and biology is discussed.

Partitioning and recovery of proteinase from tuna spleen by aqueous two-phase systems

Partitioning of spleen proteinase from yellowfin tuna ( Thunnus albacores) in an aqueous two-phase system (ATPS) was investigated. Phase compositions including PEG molecular mass and concentration as well as types and concentration of salts affected protein partitioning. ATPS comprising PEG1000 (15%, w/w) and magnesium sulfate (20%, w/w) provided the best condition for the maximum partitioning of the proteinase into the top phase and gave a highest specific activity (47.0 units/μg protein) and purification fold (6.61). The yield of 69.0% was obtained. Under the same ATPS condition used, the partitioning of proteinase of splenic extract from three tuna species involving skipjack tuna, yellowfin tuna and tongol tuna were compared. The purity of splenic extract from all tuna species increased after ATPS process. Among all species tested, yellowfin tuna showed the highest purification fold, followed by tongol tuna and skipjack tuna, respectively. SDS-substrate gel electrophoresis revealed that the band intensity of major proteinase in ATPS fraction from all tuna species slightly increased with the concomitant decrease in band intensity of other contaminating proteins, indicating the greater specific activity of splenic extract. Therefore, ATPS was an effective method for partitioning and recovery of proteinases from tuna spleen.