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At least 865 records · Page 48Linked to original sources
PubMed1993

Molecular weight identification of polyethylene glycols in pharmaceutical preparations by gel permeation chromatography.

The suitability of different Fractogel media [Fractogel TSK HW40(S), Fractogel TSK HW55(F), and Fractogel TSK HW65(F)] for the molecular weight identification of polyethylene glycols was examined. The results were compared with those obtained on two recently introduced gel filtration media (Superdex 75 prep grade and Superdex 200 prep grade); nonspecific adsorptions were observed for the latter. An aqueous gel filtration procedure was developed for the molecular weight identification of polyethylene glycols in drug formulations as an alternative method to that prescribed by the American Pharmacopeia. This procedure was optimized by a logit-log calibration method.

Chromatography, Gel↗
PubMed1993

Refolding and proton pumping activity of a polyethylene glycol-bacteriorhodopsin water-soluble conjugate.

Bacteriorhodopsin (BR), from the purple membrane (PM) of Halobacterium halobium, was chemically modified with methoxypolyethylene glycol (m-PEG; molecular weight = 5,000 Da) succinimidyl carbonate. The polyethylene glycol-bacteriorhodopsin (m-PEG-SC-BR33) conjugate, containing one polyethylene glycol chain, was water soluble. The secondary structure of the conjugate in water appeared partially denatured, but was shown to contain alpha-helical segments by circular dichroism spectroscopy. The isolated bacteriorhodopsin conjugate, with added retinal, was refolded in a mixed detergent-lipid micelle and had an absorption maximum at 555 nm. The refolded conjugate was transferred into vesicles that pumped protons, upon illumination, as efficiently as did native BR. Modification of the PM with m-PEG did not alter the native structure or inhibit proton pumping, and therefore it is suggested that the glycol polymer is present as a moiety covalently linked to residues unnecessary for proton pumping and proper folding. The site of attachment of m-PEG was determined to be at either Lys 129 or Lys 159, with position Lys 129 the most probable site of attachment. The m-PEG-SC-BR33 could be stepwise refolded to the native conformation by the addition of trifluoroethanol to lower the dielectric constant, simulating the insertion of the BR into the phospholipid bilayer.

Bacteriorhodopsins↗
PubMed2003

Structure of deoxyhemoglobin: ionizable groups and polyethylene glycol.

X-ray studies on deoxy-hemoglobin have been reported on crystals grown under conditions of high (about 2.5 M) and low salt (about 0.1 M). The high-salt crystals were grown in water, whereas the low-salt crystals were prepared in polyethylene glycol solutions (m.w. 6000-8000 Da, 10-30% w/v). Oxygen-binding characteristics of hemoglobin in these two environments differ radically. In salt solutions, hemoglobin binds oxygen with a p50 value of about 5 torr of oxygen and in a cooperative manner characterized with an n value of Hill varying from two to three. In polyethylene glycol solutions, hemoglobin crystals are oxygenated with a p50 value of about 270 torr of oxygen, without exhibiting a cooperative effect. I report on a detailed study of the X-ray data defining the dimer interface (alpha1beta2) of these two forms of hemoglobin. The study reveals that the main difference between the two structures lies in the number and arrangement of the water molecules and in distances between ionizable side chains in the dimer interface. I propose that these differences lead to significant shifts in the pK values of the ionizable groups in the dimer interface.

Amino Acid Sequence↗
PubMed1992

Effect of polyethylene glycol-400 at low concentrations on long-term growth of muscle phosphoglucomutase crystals from concentrated salt solutions.

Although rabbit muscle phosphoglucomutase occasionally deposits tetragonal crystals from solutions of ammonium sulfate at about 47% of saturation, low concentrations of polyethylene glycol-400 (PEG), 1 to 4.5% w/v, must be included to sustain crystal growth. A comparison of long-term growth rates for macroscopic crystals in the presence and absence of added PEG suggests that at high salt concentration this cosolute exerts its primary effect on disordered protein aggregates, either in the external medium or at the surface of the crystal, and thereby allows the growth of much larger crystals. Since the observed effects may arise from a PEG-induced increase in the "solubility" of the aggregate that exceeds the induced increase in solubility of the crystalline phase under these conditions, the physical basis for a cosolute-induced increase in solubility in the presence of a precipitant is considered. The applicability of such a rationale to the present system is supported by an assessment of the relative effects of polyethylene glycol and beta-octylglucoside on amorphous, salt-induced precipitates of phosphoglucomutase. PEG also produces what appears to be a differential effect on nucleation efficiency and crystal growth rate. Thus, seed crystals cannot be enlarged at a significant rate at high salt concentration without producing showers of extraneous nucleation centers when the concentration of added PEG is 3% or less. But PEG concentrations of 4.5% essentially eliminate the showering problem, ostensibly by increasing the supersaturation required for nucleation to a greater extent than that required for crystal growth. The same type of effect is observed during de novo growth. Again a solubility-based mechanism is posed. Hysteretic effects related to properties of amorphous aggregates of the protein also are described.

Ammonium Sulfate↗
PubMed2002

Liquid-phase peptide synthesis on polyethylene glycol (PEG) supports using strategies based on the 9-fluorenylmethoxycarbonyl amino protecting group: application of PEGylated peptides in biochemical assays.

Stepwise synthetic assembly of polypeptide chains reversibly linked to polyethylene glycol represents a hybrid between traditional solution and solid-phase chemistries and combines the inherent advantages of both approaches. The technical simplicity and scalability of the liquid-phase peptide synthesis method renders it particularly attractive for multiple parallel syntheses, combinatorial approaches and the large-scale preparation of peptides. The versatile protection strategy based on the N alpha-fluorenylmethoxycarbonyl group commonly used in solid-phase peptide synthesis was adapted to the liquid-phase approach. Fluoride ions were used rather than the conventional organic base piperidine for the repetitive amino-deprotection step. Using a range of acid- and base-labile linkers between the polymer and the peptide, it was shown that free and fully side-chain protected peptides can be obtained using our version of the liquid-phase peptide synthesis method. Protocols for simultaneous multiple syntheses requiring a minimum of equipment are presented and the use of polyethylene glycol-bound peptides in biochemical binding and functional assay systems is demonstrated.

Amino Acids↗
PubMed1996

Electrophoresis of polyethylene glycols and related materials as sodium dodecyl sulfate complexes.

Polyethylene glycol (PEG) and polyethylene glycol derivatives are analyzed by a modification of the sodium dodecyl sulfate-polyacrylamide stacking gel electrophoresis procedure of Kurfürst. Gels using a discontinuous buffer system but which do not have a separate stacking gel are used without loss of resolution and with less tendency to form artifactual multiple or distorted bands. Examination of several commercial preparations of PEGs and PEG derivatives on such gels indicates heterogeneity other than the expected unimodal size distributions. SDS-gel electrophoresis of proteins or other materials in samples containing PEGs may yield gels with zones of contamination from the PEGs. Methods of reducing such contamination are suggested.

Electrophoresis, Polyacrylamide Gel↗
PubMed1997

Determination of polyethylene glycol activated with cyanuric chloride in liposomes.

A simple method was developed for the determination of polyethylene glycol (PEG) 5000 activated with cyanuric chloride attached or adsorbed to the liposome membrane. The procedure is based in the measurement of the absorbance at 234 nm of the triazine ring of cyanuric chloride after disrupting the liposomal structure with CHCl3/MeOH (1/8, v/v). In this medium, the molar absorptivity of the molecule is the highest, and lipid does not interfere with the measurement. This procedure results in a convenient, sensitive, and rapid method for the determination of this kind of activated polyethylene glycol in liposomes. The minimal concentration of PEG measured is 50 microM, and so the method is sufficiently sensitive to quantify PEG 5000 in the minimal amounts used for protecting the liposomes from the action of serum. Values calculated by this method have been compared with those obtained by 1H NMR, and a good correlation between them has been obtained.

Cross-Linking Reagents↗
PubMed1994

The effect of polyethylene glycol gavage on plasma volume.

This study examines the hypothesis that whole gut irrigation with polyethylene glycol-electrolyte gavage solution (PEG-ELS) increases intravascular volume. Seventeen patients drank 6 to 8 liters of PEG-ELS in preparation for elective colonoscopy. The patients were weighed and serum electrolytes, albumin, hematocrit, blood urea nitrogen, and creatinine were obtained prior to the gavage and 8 hr following gavage. Plasma volume was measured before and after gavage using an isotope dilution technique involving 125I-human serum albumin. No patients developed symptoms of intravascular volume excess or depletion following gavage. There was no significant change in body weight, serum sodium, chloride, potassium, bicarbonate, blood urea nitrogen, or creatinine following gavage with PEG-ELS. When measured by the isotope dilution technique, the mean plasma volume increased from 3174 +/- 117 ml before gavage to 3365 +/- 160 ml following gavage (P = 0.03). This represented a mean percentage change in plasma volume of 5.88 +/- 2.4%. The percentage change in plasma volume associated with gavage ranged from -9.8 to +29.8%. This data supports the hypothesis that gavage with polyethylene glycol-electrolyte solution is associated with an increase in plasma volume. Although in most patients the increase in plasma volume is minimal, there is significant variability in this response, with some patients experiencing substantial increases in plasma volume.

Colon↗
PubMed1996

Purification of apolipoprotein H by polyethylene glycol precipitation.

A new method of polyethylene glycol precipitation followed by heparin affinity chromatography was established to purify apolioprotein H (Apo H, beta 2-glycoprotein I). This method is simple and effective and yields more harvest of Apo H (3-4 mg Apo H from 100 ml fetal bovine serum) than the current HClO4 extraction method. There are notable differences between Apo H purified by the polyethylene glycol method [Apo H (PEG)] and Apo H purified by the HClO4 method [Apo H (HClO4)] in respects of their SDS electrophoresis characteristics, circular dichroism spectroscopy, and isoelectric focusing graph. It is concluded that the strong acid HClO4 treatment may induce some disordered structure in Apo H molecule resulting in the lowering of molecular weight and pIs. Apo H (PEG) retains more integrated structure which may be related to its bioactivity.

Apolipoproteins↗
PubMed1991

Ether-cleaving enzyme and diol dehydratase involved in anaerobic polyethylene glycol degradation by a new Acetobacterium sp.

A strictly anaerobic, homoacetogenic bacterium was enriched and isolated from anoxic sewage sludge with polyethylene glycol (PEG) 1000 as sole source of carbon and energy, and was assigned to the genus Acetobacterium on the basis of morphological and physiological properties. The new isolate fermented ethylene glycol and PEG's with molecular masses of 106 to 1000 to acetate and small amounts of ethanol. The PEG-degrading activity was not destroyed by proteinase K treatment of whole cells. In cell-free extracts, a diol dehydratase and a PEG-degrading (ether-cleaving) enzyme activity were detected which both formed acetaldehyde as reaction product. The diol dehydratase enzyme was oxygen-sensitive and was stimulated 10-14 fold by added adenosylcobalamine. This enzyme was found mainly in the cytoplasmic fraction (65%) and to some extent (35%) in the membrane fraction. The ether-cleaving enzyme activity reacted with PEG's of molecular masses of 106 to more than 20000. The enzyme was measurable optimally in buffers of high ionic strength (4.0), was extremely oxygen-sensitive, and was inhibited by various corrinoids (adenosylcobalamine, cyanocobalamine, hydroxocobalamine, methylcobalamine). This enzyme was found exclusively in the cytoplasmic fraction. It is concluded that PEG is degraded by this bacterium inside the cytoplasm by a hydroxyl shift reaction, analogous to a diol dehydratase reaction, to form an unstable hemiacetal intermediate. The name polyethylene glycol acetaldehyde lyase is suggested for the responsible enzyme.

Anaerobiosis↗
PubMed1993

Bone reaction to uncemented threaded polyethylene acetabular components.

One hundred and eighty-one cementless total hip arthroplasties with threaded polyethylene acetabular components, carried out between 1980 and 1981, have been reviewed retrospectively. Discrepancy between the complaints of the patients with loose components and destruction of acetabular bone led to the development of a four stage radiological grading system which would enable loosening to be anticipated in routine cases. There was a high percentage of loosening (33%) in our series and direct bone-polyethylene contact gave rise to severe granulomatous reactions around the implants. Strict radiological follow up and early revision surgery is indicated in this type of arthroplasty.

Acetabulum↗
PubMed1987

Real time observations of polylysine, dextran and polyethylene glycol induced mutual adhesion of erythrocytes held in suspension in an ultrasonic standing wave field.

A technique which enables cells to be observed in suspension for times of the order of minutes (employing acoustic radiation forces in a 1 MHz ultrasonic standing wave field) is described. Video recordings of the mutual adhesion of human erythrocytes in suspension have been analysed. Concave-ended cell doublets and linear rouleaux developed in 0.5-1.5% w/v Dextran T500 by a gradual (2.5-17 s) increase in the area of cell contact over the cell cross-section. The concave-ended rouleaux form was not seen in polylysine or in polyethylene glycol. In 5-7% dextran and in 20 micrograms/ml polylysine mutual adhesion was a two stage process. Cells first form a strong local contact which persists (without apparently growing in area) for a number of seconds following which the cell surfaces move suddenly to form a spherical doublet. The average initial contact time and engulfment time for cells in 7% Dextran T500 are 18 and 2.7s, respectively. The corresponding values for cells in 20 micrograms/ml, 14 kDa, polylysine are 2.7 and 0.3s. There was no initial contact delay during spherical doublet formation in 1 mg/ml polylysine. Electron microscopy showed that the intercellular seam for spherical doublets formed with all three agglutinating molecules was bent in a wavy lambda approximately equal to 4 micron) profile. The thickness of the intercellular space varied in a spatially periodic way (lambda approximately equal to 0.8 microns) for cells in polylysine. Examples of periodic intercellular spaces were seen by light microscopy in polyethylene glycol induced clumps. The role of interfacial instability in the adhesion processes is discussed.

Cell Adhesion↗
PubMed1981

Comparative studies of Feulgen hydrolysis for DNA. I. Influence of different fixatives and polyethylene glycols.

We compared the Feulgen hydrolysis curves (37 degrees C, 5 M HCl) of human blood lymphocytes fixed by the following four methods: 96% ethanol, 60 min at 20 degrees C; ethanol-acetone, 1:1, 120 min at 4 degrees C; ethanol-glacial acetic acid mixture (3:1), containing 2% of formaldehyde (EAF), 90 min at 20 degrees C; and ethanol-glacial acetic acid (3:1), 60 min followed by 5% chrome alum solution for 360 min at 20 degrees C. The best results were obtained with EAF-fixation, with respect to the highest amount of DNA-Schiff complex at the peak point of the curve, the longest "plateau" region and the smallest scattering of DNA-Schiff amount values along the "plateau". With other types of fixation the addition of polyethylene glycol (PEG) 6,000 to the hydrolysis solution resulted in modification of the shape of the hydrolysis curve so that it became nearly similar to the EAF-curve. The effect of PEG6000 on the EAF-curve was minimal. Slides fixed by ethanol were used for a comparison of polyethylene glycols with m.w. 1,500, 6,000 and 20,000. The longest "plateau" was obtained with PEG6000. The only effect of PEG1500 was a dramatic increase of DNA-Schiff amount at the peak point. PEG20000 had no significant effect on the shape of the hydrolysis curve. The results are discussed in terms of Kjellstrand's "chain with a stable structure" model of Feulgen hydrolysis.

Acetates↗
PubMed1989

Piretanide-dextran and piretanide-polyethylene glycol interact with high affinity with the Na+ 2 Cl- K+ cotransporter in the thick ascending limb of the loop of Henle.

Piretanide blocks the Na+ 2Cl- K+ cotransporter protein in the thick ascending limb (TAL) of the loop of Henle reversibly. When tested from the luminal side in isolated perfused cTAL segments it leads to a half maximal inhibition (IC50) of the equivalent short circuit current (Isc) at a concentration of 10(-6) mol/l. From the basolateral side it has no effect on Isc up to 10(-4) mol/l. The present study was designed to search for high affinity blockers of the Na+ 2Cl- K+ cotransporter with large molecular weight in an attempt to use these macromolecules for antibody-labelling or affinity separation of this transport-protein. Amino-ethyl-dextran or amino-ethyl-polyethylene glycol (M.W. 5kd) were coupled to isothiocyanato-piretanide (ISO-PIR) at room temperature in DMSO. The resulting compounds dextran-sulfonylurea-piretanide (PIR-DEX) and polyethylene glycol-sulfonylurea-piretanide (PIR-PEG) (M.W. 5.38kd) were purified and tested in isolated perfused cTAL segments. IC50 values for ISO-PIR, PIR-DEX and PIR-PEG were estimated from dose response curves after their addition to the lumen or bath perfusate, respectively. ISO-PIR, PIR-DEX and PIR-PEG acted from the lumen side at 3.10(-6), 6.10(-6) and 2.10(-6) mol/l. The inhibitory effect was easily reversible. From the basolateral side no effect for any compound was seen at up to 10(-4) mol/l. In clearance experiments PIR-DEX was given to female Wistar rats as an i.v. bolus (25 mumol/kg) and the diuretic urine was collected. After dialysis (exclusion limit 2.5kd) the dialysed urine and the dialysate were tested in isolated perfused cTAL segments.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

A method for the purification of E. coli plasmid DNA by homogeneous lysis and polyethylene glycol precipitation.

A procedure is described for the isolation and purification of E. coli plasmid DNA by polyethylene glycol precipitation. The method is rapid, simple, inexpensive and amenable to both small and large scale manipulation. This procedure involves lysis of bacterial cells by treatment with pronase in sodium dodecyl sulfate, removal of chromosomal DNA by centrifugation, precipitation of residual nucleic acids with polyethylene glycol and removal of RNA by precipitation with LiCl. Plasmid DNA purified as described is pure enough for restriction endonuclease analysis, for use as a vector for the cloning of cDNA or synthetic DNA, or for use as a template in an E. coli transcription-translation cell-free system.

DNA↗
PubMed1997

Actinomyces infection in porous polyethylene orbital implant.

BACKGROUND: A 60-year-old patient developed actinomycotic inflammation within a porous polyethylene orbital implant which she received following enucleation. METHODS: She had repeated conjunctival exposures with inflammation; the primary implant was removed and replaced with another one. RESULTS: The anterior two-thirds of the porous implant was infiltrated with numerous actinomycotic granules surrounded by polymorphonuclear cells and necrotic debris. The organisms were demonstrated with Gram stains on the histopathologic preparations and with scanning electron microscopy. Within the zones of inflammation, the polyethylene skeleton of the implant was extensively damaged. CONCLUSION: Actinomycetes have been described as causative organisms in conjunctivitis, blepharitis, canaliculitis, dacryocystitis and keratitis, but to the best of our knowledge actinomycotic involvement has never been reported in an infected porous orbital implant.

Actinomyces↗
PubMed1984

Rectal absorption of metronidazole from polyethylene glycol suppositories.

The rectal absorption of metronidazole from an aqueous suspension, a fatty suppository and three different polyethylene glycol suppositories was studied in healthy volunteers and compared with absorption from an oral solution. Rectal absorption was found to be rather slow for all suppositories. Of all rectal dosage forms, the polyethylene glycol suppositories gave the highest peak plasma levels and the highest relative bioavailability. Compared with oral administration, a relative bioavailability of 80% could be obtained.

Administration, Oral↗
PubMed1992

Stability of sufentanil citrate in a portable pump reservoir, a glass container and a polyethylene container.

The stability of sufentanil citrate (100 ml, 5 micrograms/ml) in an admixture with sodium chloride 0.9% injection was investigated when filled in a portable pump reservoir with PVC wall, a glass container and a polyethylene container, at 32 degrees C, 4 degrees C and -20 degrees C for up to 21 days. No change in colour was visually observed in any of the samples during the 21-day storage period. A slight precipitation was noticed in three out of nine portable pump reservoirs, one at each storage temperature. There was a slight rise in pH at each storage temperature in all samples. There was approximately 13% loss of sufentanil citrate in the portable pump reservoirs stored at 32 degrees C during 2 days and 60% loss after 21 days, due to absorption of sufentanil citrate in the reservoir wall. No loss of sufentanil citrate could be detected in the portable pump reservoirs when stored at -20 degrees C and 4 degrees C. However, a serious inhomogeneity of the sufentanil citrate solution occurred after thawing at room temperature in the portable pump reservoirs which had been kept at -20 degrees C. The homogeneity could be restored by shaking for approximately 10 min. There was no change in the sufentanil citrate concentrations in the glass containers and polyethylene containers stored at the three temperatures. The portable pump reservoirs stored at 32 degrees C also showed a significant loss of vehicle due to evaporation (1.0 +/- 0.1 ml a week). This could not be detected in any of the other samples.

Absorption↗