Ethylene Oxide-propylene Oxide Copolymer Research Articles

Purification of recombinant apolipoprotein A-1 Milano expressed in Escherichia coli using aqueous two-phase extraction followed by temperature-induced phase separation

A method for purification of recombinant apolipoprotein A1 in aqueous two-phase systems has been studied. A mutant of apolipoprotein A-I, the Milano variant, was expressed in E. coli. Phase systems containing ethylene oxide (EO)–propylene oxide (PO) random copolymers have been used. These polymers are thermoseparating and have the ability to separate into one water-rich and one polymer-rich phase when heated above a critical temperature i.e. the cloud point. The filtrate from an E. coli fermentation was added to a primary aqueous two-phase system composed of an EO–PO copolymer and Reppal, which is an inexpensive hydroxypropyl starch. Apolipoprotein A-I was partitioned to the top EO–PO copolymer phase and contaminating proteins to the bottom starch phase. The phase diagrams for Reppal PES 100-EO 50PO 50 (Ucon) and Reppal PES 100-EO 30PO 70 were determined. The effect on partitioning, when changing parameters such as polymer concentration, type of polymer, protein concentration, pH, salt concentration and volume ratio, were studied. Studies on E. coli DNA partitioning showed that DNA could be partitioned strongly to the bottom phase. An optimal system was scaled up from 5 g to 5 kg with similar degrees of purification, i.e. 2.5 and 2.7 and yields of 79% and 82% respectively. Furthermore temperature-induced phase formation was used for separation of apolipoprotein A-I from the copolymer by raising the temperature above the copolymer cloud point; thus, recovering protein in a `clean' water phase.

Effects of salts and the surface hydrophobicity of proteins on partitioning in aqueous two-phase systems containing thermoseparating ethylene oxide-propylene oxide copolymers

The partitioning of five well-characterized model proteins, bovine serum albumin (BSA), lysozyme, β-lactoglobulin A, myoglobulin and cytochrome c, in aqueous two-phase systems has been studied. As top phase polymers PEG (polyethylene glycol, 100% EO) and the thermoseparating ethylene oxide (EO)-propylene oxide (PO) random copolymers,Ucon 50-HB-5100 (50% EO, 50% PO) and EO 30PO 70 (30% EO, 70% PO), respectively, were used. The top phase polymers are increasing hydrophobicity with increasing content of PO. Reppl PES 200 (hydroxypropyl starch) was used as the bottom phase polymer. Phase diagraams for Reppal PES 200-PEG and Reppal PES 200-EO 30PO 70 two-phase systems were determined. The partitioning of four salts with different hydrophobicity, and also the effect of the salts on protein partitioning inn these systems, was studied. It waas found that the partitioning of the salts followed the Hofmeister series. The partitioning of proteins with low surface hydrophobicity, mygglobin and cytochrome c, was little affected by hydrophobic polymers and salts. However, the parttioning of a protein with higher surface by hydrophobiocity, lysozyme, was strongly affected when polymer hydrophobicity was increased and a hydrophobicity counterion was used. A protein with relatively hydrophobic surfac can be partitioned to a phase containing a thermoseparating EO-PO copolymer by using a hydrophobic counterion. The parttioning of lysozyme and cytochrome c in the polymer-water system formed after temperature-induced phase separation was also examined. Both proteins partitioned exclusivvely to the water phase. A separation of the protein and polymer was obtained by temperature-induced phase separation on the isolated phase containing the EO-PO copolymer. The partitioning data also indicatedthat the hydroxypropyl starch polymer had a weak negative charge.

A Study on the Properties of Micelle Formed by Ethyleneoxide-Propyleneoxide Copolymer with Fluorescent Probe Method

A Study on the Properties of Micelle Formed by Ethyleneoxide-Propyleneoxide Copolymer with Fluorescent Probe Method

Polymer aqueous solutions as quenching media. II. Ethylene oxide–propylene oxide copolymers

AbstractThe cooling power of aqueous solutions of ethylene oxide‐propylene oxide copolymers are studied with a silver standard sample by using two apparatuses quench with injection and quench with agitation. For temperature T>400°C, the viscosity plays the predominant role; for T<400°C, the cooling is controlled by the polymer precipitation and the cooling rate decreases by lowering the cloud point of the polymer solution. This work demonstrates the possibility of adjusting the cooling curves by taking into account the thermodynamical properties of the polymer.

Effect of hydrophilic soft segment side chains on the surface properties and blood compatibility of segmented poly (urethaneureas)

Segmented poly(urethaneureas) with hydrophilic side chains were prepared from poly(tetramethylene oxide) (PTMO), 4,4'-diphenylmethane diisocyanate (MDI), ethylene diamine (ED) and a diol with a long hydrophilic side chain comprised of an ethylene oxide-proplene oxide copolymer. The end groups of the hydrophilic chains were either sodium sulfonate or methoxy groups. The state of microphase separation showed a small dependence on the fraction of long-chain hydrophilic diol. Surface analysis by means of static underwater contact angle and dynamic contact angle measurements revealed that the graft chains were at the aqueous interface in the hydrated state. An ex vivo A-V shunt experiment revealed that a more thrombogenic blood-material response was correlated with an increase in the concentration of polymeric hydrophilic side chain incorporation. The polyurethane containing a long chain diol with methoxy end groups exhibited a higher level of thrombogenicity than the similar polymers possessing a sulfonate terminated side chain.

Acute Inhalation Toxicity Studies in Several Animal Species of An Ethylene ox Ide/Propylene Oxide Copolymer (Ucon 50-Hb-5100)

An acute inhalation toxicity study in several species of animals with an ethylene oxide/propylene oxide copolymer (EO/PO) having a molecular weight of 4000 [UCON-50-HB-5100, CAS #9038-95-3] was designed to determine if any species variation could be shown. Species tested included: rats, mice, hamsters, guinea pigs, and dogs. The test material was administered as a respirable liquid aerosol for 4 hours at target concentrations of 50, 100, 200, and 500 mg/m3. A vehicle control group was exposed to a distilled water aerosol. The 4 hours LC50's were calculated to be 147 mg/m3 [rats], 174 mg/m3 [mice], 293 mg/m3 [guinea pigs] and 511 mg/m [hamsters]. The dog LC50 was determined to be greater than 500 mg/m3 since all the test animals survived exposure to this concentration. These values show that rats and mice were the most sensitive species with a declining response in guinea pigs, hamsters and dogs. Lung weights were increased at all exposure concentrations in rats, mice and hamsters. Lung weights were increased in guinea pigs at exposure concentrations of 100 mg/m3 and above. Lung weights in dogs were increased only at the 500 mg/m3 exposure concentration. Significant pathological changes were limited to the lungs and were more common in animals which died prior to scheduled sacrifice. Grossly, these lung changes consisted of red discoloration, edema, emphysema, and surface irregularities. Microscopic findings in the lungs included acute congestion and hemorrhage and, less commonly, acute interstitial inflammation.

Characterization of hydrophobicity gradients prepared by means of radio frequency plasma discharge

A hydrophobicity gradient was created by gradually exposing a polydimethylsiloxane film to a radio frequency glow discharge in an oxygen atmosphere. A change in contact angle from 100 to 0° was measured along the gradient surface by means of the Wilhelmy balance technique. The gradient surface was characterized by studying the adsorption from single protein solutions of human albumin, IgG and fibrinogen using total internal reflectance fluorescence (TIRF). Generally, adsorption values similar to monolayer capacities were measured on the hydrophobic side. The adsorption decreased towards the hydrophilic end in correspondence with the change in contact angle. The displacement of proteins with a ethylene oxide-propylene oxide copolymer (EO 70PO 100EO 70) was higher on the hydrophobic side than on the hydrophilic side. Albumin showed an adsorption peak in the wetting transition region, indicating a very strong affinity.

Wetting and plasma-protein adsorption studies using surfaces with a hydrophobicity gradient

Wetting gradients on silica were prepared according to the technique developed by Elwing et al. (J. Colloid Interface Sci., 119 (1987) 1). The contact angle, determined by the Wilhelmy-plate method, showed an S-shaped dependence on the position along the gradient. The advancing water contact angle was 0° on the hydrophilic end and 97±3° on the hydrophobic end. The receding water contact angles were ∼40° smaller in the wetting transition region and ∼20° smaller on the hydrophobic side of the gradient. Total internal reflection fluorescence (TIRF) was used to study the adsorption of three fluorescein-labelled proteins: human serum albumin, IgG and fibrinogen. The gradient surface exposed to a single protein solution resulted in an amount of adsorbed protein on the hydrophobic end that approximately corresponded to a monolayer. As a rule, lower adsorption was found on the hydrophilic end. When the proteins were adsorbed from a mixture, the surface concentration of albumin was generally not affected, the fibrinogen adsorption decreased by 40–50% and the IgG adsorption decreased to 10% of the adsorption measured from a single protein solution. The so-called Vroman effect (for example, transient IgG adsorption maximum in adsorption kinetics) was found on the hydrophobic side of the gradient. The desorption experiments were carried out with a nonionic polymeric surfactant, an ethylene oxide-propylene oxide copolymer: EO100-PO70-EO100. The adsorption affinity of albumin to the wetting transition region, as measured by surfactant induced desorption, was extraordinarily high.

Ionic conduction in ethylene oxide-propylene oxide copolymers containing LiClO4

Abstract Ethylene oxide and propylene oxide were copolymerized at various mixing ratios using coordination catalysts. Total ionic conductivities and lithium ion transport numbers of the copolymer-LiClO 4 -complexes were measured in the temperature range +25°C to +90°C. Total conductivity was found to decrease with increasing PO content of the copolymer, however being higher than the conductivities of commercial PEO and PPO. The lithium transport number does not significantly deviate from that of pure polymer-LiClO 4 -complexes.

Sequence Analysis of Ethylene Oxide-Propylene Oxide Copolymers by Carbon-13 Nuclear Magnetic Resonance

Sequence Analysis of Ethylene Oxide-Propylene Oxide Copolymers by Carbon-13 Nuclear Magnetic Resonance