Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PEG”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMed2001

Targeted PEG-based bioconjugates enhance the cellular uptake and transport of a HIV-1 TAT nonapeptide.

We previously described the enhanced cell uptake and transport of R.I-K(biotin)-Tat9, a large ( approximately 1500 Da) peptidic inhibitor of HIV-1 Tat protein, via SMVT, the intestinal biotin transporter. The aim of the present study was to investigate the feasibility of targeting biotinylated PEG-based conjugates to SMVT in order to enhance cell uptake and transport of Tat9. The 29 kDa peptide-loaded bioconjugate (PEG:(R.I-Cys-K(biotin)-Tat9)8) used in these studies contained eight copies of R.I-K(biotin)-Tat9 appended to PEG by means of a cysteine linkage. The absorptive transport of biotin-PEG-3400 (0.6-100 microM) and the bioconjugate (0.1-30 microM) was studied using Caco-2 cell monolayers. Inhibition of biotin-PEG-3400 by positive controls (biotin, biocytin, and desthiobiotin) was also determined. Uptake of these two compounds was also determined in CHO cells transfected with human SMVT (CHO/hSMVT) and control cells (CHO/pSPORT) over the concentration ranges of 0.05-12.5 microM and 0.003-30 microM, respectively. Nonbiotinylated forms of these two compounds, PEG-3350 and PEG:(R.I-Cys-K-Tat9)8, were used in the control studies. Biotin-PEG-3400 transport was found to be concentration-dependent and saturable in Caco-2 cells (K(m)=6.61 microM) and CHO/hSMVT cells (K(m)=1.26 microM). Transport/uptake was significantly inhibited by positive control substrates of SMVT. PEG:(R.I-Cys-K(biotin)Tat9)8 also showed saturable transport kinetics in Caco-2 cells (K(m)=6.13 microM) and CHO/hSMVT cells (K(m)=8.19 microM). Maximal uptake in molar equivalents of R.I-Cys-K(biotin)Tat9 was 5.7 times greater using the conjugate versus the biotinylated peptide alone. Transport of the nonbiotinylated forms was significantly lower (P<0.001) in all cases. The present results demonstrate that biotin-PEG-3400 and PEG:(R.I-Cys-K(biotin)Tat9)8 interact with human SMVT to enhance the cellular uptake and transport of these larger molecules and that targeted bioconjugates may have potential for enhancing the cellular uptake and transport of small peptide therapeutic agents.

Animals↗
PubMed1997

Capillary electrophoresis of r-hirudin and a polyethylene glycol derivative of r-hirudin (PEG-hirudin).

UNLABELLED: Recombinant (r-) hirudins and PEG-hirudin are currently tested for anticoagulant therapy. For their concentration measurement, radioimmunoassay and HPLC methods are available. The separation of r- and PEG-hirudin is currently performed by HPLC. However, the sensitivity of the method is low. Capillary electrophoresis is a rapid, selective technique that requires low sample amounts. Our aim was the development of a capillary electrophoresis method to measure r- and PEG-hirudin. The results are as follows: In a borate solution (0.3% boric acid and 0.4% sodium tetraborate, pH 9.5) r-hirudin was separated from PEG-hirudin in a purified system using a fused silica capillary (50 cm long and 75-micron i.d. and reversed polarity). A neutral capillary with a 20 mM tricine buffer (pH 8.0, field strength 500 V/cm) was also effective in resolving r- from PEG-hirudin. A linear correlation was found between the peak area and the concentration between 20 micrograms/mL and 10 mg/mL for hirudin (r2 = 0.99) and between 1.25 and 10 mg/mL for PEG-hirudin (r2 = 0.99). In human plasma mixtures, r- and PEG-hirudin were completely separated. The linear correlation between the peak area and the concentration was r2 = 0.99. CONCLUSION: In a fused silica capillary, r- and PEG-hirudin are separated in a purified system. Capillary electrophoresis which is performed in a neutral capillary, resolves r- from PEG-hirudin in a purified system, in plasma and in urine. The sensitivities of the methods are comparable. Capillary electrophoresis separates r- from PEG-hirudin and may be applied to biologic systems to measure the concentration and purity of r- and PEG-hirudin.

Electrophoresis, Capillary↗
PubMed2003

Percutaneous endoscopic gastrostomy (PEG) for enteral nutrition in patients with stroke.

BACKGROUND: The use of percutaneous endoscopic gastrostomy (PEG) for enteral nutrition in patients admitted for stroke is difficult, varying and needs specific consideration. There is therefore need for more data on this patient group. We examined the indications, survival, tube removal and time with PEG in stroke patients and in other patients with PEG with the aim of providing guidance for the management of enteral nutrition via PEG in stroke patients. METHODS: Retrospective assessment of data from all stroke patients and patients with other diseases (control group) who had received PEG for enteral nutrition during a period of 8.5 years. RESULTS: Eighty-three stroke patients with dysphagia received PEG after unsuccessful use of nasogastric tubes or long-term tube feeding. Early mortality rate was 19% in the stroke group, 26% in the older group (>74 years) and 12% in the younger group (60-74 years). The PEG tubes were later removed due to swallowing recovery in 20% of the older group and in 31% of the younger group. At 90 days, 50%-60% still needed PEG. The stroke patients were older compared to the control group (n = 115); 30-day mortality was similar but more patients recovered the ability to swallow. CONCLUSIONS: Stroke patients are older than other patients who receive PEG; 27% have swallowing recovery and more than 75% have long-term need for PEG. Nasogastric tubes often fail, and the need for early PEG placement (within 2 weeks) must be assessed in appropriate patients. The patient's prognosis, the objective of nutritional treatment, duration of dysphagia, age and comorbidity should all be taken into consideration.

Adult↗
PubMed1992

Polyethylene glycol (PEG) modification of granulocyte-macrophage colony stimulating factor (GM-CSF) enhances neutrophil priming activity but not colony stimulating activity.

PEG-modified proteins have numerous advantages over their unmodified counterparts (increased half life, reduced antigenicity, improved solubility), but almost without exception, they show a modest to marked reduction in biological or enzymatic activity. However, while investigating a new protocol for the preparation of PEG-proteins, we compared PEG-modified and unmodified GM-CSF with respect to their polymorphonuclear neutrophil granulocyte (PMN) priming activities. PEG-GM-CSF was unexpectedly more active than GM-CSF in its ability to prime neutrophils to respond to the synthetic peptide n-formyl-methionyl-leucyl-phenylalanine (FMLP) with an oxidative burst (assessed both by nitroblue tetrazolium reduction and ferricytochrome c reduction). These results were in contrast to the findings for colony stimulating activity and with GM-CSF induced thymidine uptake, where the biological activity was unchanged or reduced. The enhanced neutrophil priming activity of PEG-GM-CSF was confirmed using FPLC fractionated PEG-modified GM-CSF. This showed changes in the bioactivity profile consistent with both the shift in protein elution profile and enhanced activity of the PEG-modified material (reflected in the increased area under the bioactivity curve). We also excluded a neutrophil priming action for PEG-modified fetal calf serum proteins, carrier proteins and 'irrelevant' cytokine, erythropoietin. The dissociation of the two bioactivities was confirmed using individual FPLC fractions. These results suggest the presence of differences in either binding, receptor/ligand processing or signal transduction for neutrophils versus progenitors, that are differentially affected by PEG-modification of GM-CSF. The demonstration that PEG-modification can partially dissociate two biological activities suggests the feasibility of using PEG-modification to produce proteins with subtly altered spectra of biological activity and hence new ranges of clinical applications.

Cells, Cultured↗
PubMed2000

Weekly subcutaneous pegylated recombinant native human leptin (PEG-OB) administration in obese men.

To assess the biological activity and tolerability of pegylated recombinant native human leptin (PEG-OB), 30 obese men (mean body mass index, 33.9 kg/m2) were randomized to a double-blind treatment with weekly sc injections of 20 mg PEG-OB or placebo for 12 weeks, in addition to a hypocaloric diet (deficit, 2 MJ/day). Body composition, energy expenditure, and metabolic parameters were measured before and after treatment. PEG-OB was generally well tolerated based on adverse event reports, lab values, and vital signs. Weekly sc PEG-OB led to sustained serum concentrations of PEG-OB and leptin throughout treatment. No significant differences in the delta or percent weight loss, percent body fat, sleeping metabolic rate, or respiratory quotient were observed between the PEG-OB and placebo groups. Percent change in serum triglycerides from baseline was significantly correlated with body weight loss in the PEG-OB group, but not in the placebo group. Although larger reductions in serum triglycerides were observed in the PEG-OB group compared with the placebo group, these differences were not statistically significant. We concluded that weekly injection of PEG-OB leads to sustained serum concentration of PEG-OB and leptin throughout the 12-week treatment period and is generally well tolerated. The trends observed in serum triglycerides suggest that a weekly 20-mg sc treatment with PEG-OB may have biological effects in obese men.

Adolescent↗
PubMed2000

Gravimorphogenesis of Cucurbitaceae plants: development of peg cells and graviperception mechanism in cucumber seedlings.

We examined the effect of microgravity on the peg formation of cucumber seedlings for clarifying the mechanism of gravimorphogenesis in cucurbitaceous plants. The spaceflight experiments verified that gravity controls the formation of peg, hypocotyl hook and growth orientation of cucumber seedlings. Space-grown cucumber developed a peg on each side of the transition zone of the hypocotyl and root, indicating that on the ground peg formation is regulated negatively by gravity (Takahashi et al. 2000). It was found that the auxin-regulated gene, CS-IAA1, was strongly expressed in the transition zone where peg develops (Fujii et al. 2000). In the seedlings grown horizontally on the ground, CS-IAA1 transcripts were much abundant on the lower side of the transition zone, but no such differential expression of CS-IAA1 was observed in the space-grown cucumber (Kamada et al. 2000). These results imply that gravity plays a role in peg formation through auxin redistribution. By the negative control, peg formation on the upper side of the transition zone in the horizontally growing seedlings might be suppressed due to a reduction in auxin concentration. The threshold theory of auxin concentration accounted for the new concept, negative control of morphogenesis by gravity (Kamada et al. 2000). Anatomical studies have shown that there exists the target cells destined to be a peg and distinguishable at the early stage of the growth. Ultra-structural analysis suggested that endoplasmic reticulum develops well in the cells of the future peg. Furthermore, it was found that reorganization of cortical microtubules is required for the change in cell growth polarity in the process of peg formation. The spaceflight experiment with cucumber seedlings also suggested that in microgravity positive hydrotropic response of roots occurred without interference by gravitropic response (Takahashi et al. 1999b). Thus, this spaceflight experiment together with the ground-based studies has shown that cucumber seedling is an ideal for the study of gravimorphogenesis, hydrotropism and their interaction. Although peg formation is seen specifically in cucurbitaceous seedlings, it involves graviperception, auxin transport and redistribution and cytoskeletal modification for controlling cell growth polarity. This system could be a useful model for studying important current issues in plant biology.

Cucumis sativus↗
PubMed1997

[Our experience of PEG and home care for twelve years].

Percutaneous endoscopic gastrostomy (PEG) was introduced in 1980 by Ponsky et al. This technique does not require general anesthesia and is performed safely and rapidly under local anesthesia without laparotomy. For the past twelve years, in order to maintain enteral alimentation for patients who suffered from dysphagia due to cerebral angiopathy, and to reduce patients' suffering from the long-term placement of a nasogastric tube, PEGs were performed in 150 patients (130 patients for enteral nutrition and 20 for drainage of gastrointestinal contents). We also provided home care service for 30 (27 for enteral nutrition and 3 for decompression) of these patients. We pointed out two problems connected with our retrospective studies for PEG. One is related to the indication of PEG, especially to the evaluation of preoperative status. We suggested a new method for measuring the preoperative status of patients for PEG (PEG-POS score). Retrospective studies showed the PEG-POS score was effective. Using this PEG-POS score, we have not had any early-stage deaths after PEG. Another is related to the home care service for patients with PEG. Consulting the questionnaire survey of families who experienced PEG home care, we examined various problems of home care.

Adult↗
PubMed2002

Treating cancer with PEG Intron: pharmacokinetic profile and dosing guidelines for an improved interferon-alpha-2b formulation.

BACKGROUND: PEG Intron (pegylated interferon-alpha-2b [IFN-alpha-2b]; Schering-Plough, Kenilworth, NJ) has demonstrated delayed clearance and increased area under the curve compared with native IFN-alpha-2b. Studies in patients with chronic hepatitis C infection and malignancies have demonstrated both biologic and clinical activity of PEG Intron and have provided empiric data to compare the pharmacokinetics (PK) and pharmacodynamics of PEG Intron and IFN-alpha-2b. METHODS: The authors conducted a review of the available data comparing the PK and pharmacodynamic effects of PEG Intron and IFN-alpha-2b. Safety and efficacy data from Phase I/II studies of PEG Intron in patients with chronic myelogenous leukemia (CML) and solid tumors were also reviewed. RESULTS: Data from patients with chronic hepatitis C infection suggest that exposure to IFN at a PEG Intron dose of 0.25 microg/kg per week is similar to that observed after administration of IFN-alpha-2b at a dose of 3 million International Units, three times per week. PEG Intron at doses up to 6 microg/kg per week was well tolerated and demonstrated clinical activity in patients with CML and solid tumors, including metastatic melanoma and renal cell carcinoma. CONCLUSIONS: Dose intensification can be achieved safely in patients with CML and solid tumors using PEG Intron, which could improve efficacy. These results provide useful dosing guidelines to clinicians investigating the antitumor activity of PEG Intron in patients with malignancies. More data are needed to determine the optimal dose in various oncologic indications. However, these results provide a sound rationale for further investigation of PEG Intron.

Antineoplastic Agents↗
PubMed2006

The apparent plasticizing effect of polyethylene glycol (PEG) on the crystallinity of spray dried lactose/PEG composites.

Aqueous solutions of lactose and polyethylene glycol (PEG) were spray dried in a Büchi Model 191 spray dryer with the aim to investigate the effect of PEG on the crystallinity of the composite. A PEG concentration of 10.7% by weight of solids was studied for PEG 200, 600, 1500, 4000 and 8000. For PEG 200 and 4000 additional concentrations from 1.5-19.3% to 1.5-32.4%, respectively, were investigated. The spray dried composites were analysed with X-ray powder diffraction and modulating differential scanning calorimetry. The crystallinity of lactose in the composites varied from 0% to 60%, dependent on the molecular weight and concentration of PEG. Apparently, lactose crystallinity is promoted by low molecular weight and high concentration of the PEG. PEG did not affect the lactose glass transition temperature. It is suggested that lactose and PEG are solidified separately during spray drying and that partial crystallization of lactose is associated with effects of PEG on the rate of drying.

Calorimetry, Differential Scanning↗
PubMed2006

True incidence and clinical significance of pneumoperitoneum after PEG placement: a prospective study.

BACKGROUND: PEG is a widely used method for providing nutritional support. Although pneumoperitoneum is a known finding after PEG placement, its true incidence is subject to debate. Small retrospective studies have found varied rates of free air after PEG placement. PATIENTS: There were a total of 65 patients. OBJECTIVE: To assess the true incidence of pneumoperitoneum and its clinical significance. DESIGN: Prospective study. SETTING: Long Island Jewish Medical Center. INTERVENTIONS: We obtained upright and anterior-posterior chest radiographs of 65 patients within 3 hours after PEG placement. Type of PEG tube, gauge of the needle used, number of sticks, and indications were recorded. The presence of pneumoperitoneum on the initial chest film was considered to be a positive finding. After a positive result, a repeat chest film was obtained 72 hours later to determine whether there was progression or resolution of the free air. Patients enrolled in the study were also monitored clinically for evidence of peritonitis. MAIN OUTCOME: Of the 65 patients who underwent PEG placement, 13 developed a pneumoperitoneum on the initial chest radiograph; there was complete resolution of pneumoperitoneum at 72 hours in 10 of the 13 patients. In 3 patients, the free air persisted but was of no clinical significance. MEASUREMENTS: The free air was quantified by measuring the height of the air column under the diaphragm and was graded with a scoring system (0, no air; 1, small; 2, moderate; 3, large). RESULTS: Eleven patients who underwent PEG died during the hospitalization; none of the deaths were related to the PEG placement or pneumoperitoneum. The other 54 patients were discharged to a skilled nursing facility. No patients in the study had clinical evidence of peritonitis. There were no adverse events, ie, infection or bleeding, associated with the PEG placement in any of the patients. CONCLUSIONS: Our data suggest that pneumoperitoneum after PEG placement is common and, in the absence of clinical symptoms, is of no clinical significance and does not warrant any further intervention.

Adult↗
PubMed2006

Synthesis and cellular studies of PEG-functionalized meso-tetraphenylporphyrins.

The total syntheses of four PEG-functionalized porphyrins, containing one to four low molecular weight PEG chains linked via amide bonds to the para-phenyl positions of meso-tetraphenylporphyrin, are reported. The hydrophobic character of the PEG-porphyrins decreases with the number of PEG chains linked to the porphyrin ring, while their tendency for aggregation in buffered aqueous solution increases. The porphyrins containing one or two PEG chains accumulated within human HEp2 cells to a much higher extent than those having three or four PEGs at the macrocycle periphery. All PEG-porphyrins were found to be non-toxic in the dark, and only those containing one or two PEG chains were phototoxic (IC(50)=2 microM at 1J/cm(2) light dose). The preferential sites of subcellular localization of the porphyrins containing one or two PEG chains were found to be the mitochondria and endoplasmic reticulum (ER), while those containing three or four PEG chains localize preferentially in the lysosomes.

Animals↗
PubMed2001

Incidence and predictors of PEG placement in ALS/MND.

In the Project on Death in America ALS cohort, 121 patients were followed to examine the timing of key milestones in the course of the disease, such as tracheostomy and PEG placement. During the 2- to 4-year follow-up period, 26.5% of patients received PEG, yielding a cumulative incidence of 48%. PEG placement occurred, on average, 16 months after patients received confirmation of the diagnosis at our Center. Patients who received PEG were more likely to have tracheostomies than patients not using PEG (p<0.01). In multivariate proportional hazard models that included both sociodemographic and disease indicators, the strongest predictor of PEG use was a patient's baseline preference for PEG: 57.1% of patients "absolutely in favor" went on to have PEG, compared to only 9.3% of those "absolutely against" (p<0.01). PEG users were more likely to have initiated health care proxies. These findings suggest that patients who use PEG may be consistently proactive in the face of the disease.

Attitude to Health↗
PubMed1996

Thrombopoietic effects of pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) in patients with advanced cancer.

BACKGROUND: Pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) is a potent stimulator of megakaryocyte colony formation and platelet production. It is likely to be useful in the management of severe thrombocytopenia. To determine its clinical activity and safety, we gave it to patients with advanced cancer before chemotherapy. METHODS: Patients were randomly assigned to receive either PEG-rHuMGDF or placebo in a three to one ratio. PEG-rHuMGDF was given at a dose of 0.03, 0.1, 0.3, or 1.0 microgram/kg body weight. The study drug or placebo were administered daily by subcutaneous injection for up to 10 days or until a target platelet count was reached. FINDINGS: 17 patients, median age 59 years, received either PEG-rHuMGDF (13 patients) or placebo (four patients). PEG-rHuMGDF produced a dose-dependent increase in platelet counts. Patients given placebo. 0.03, and 0.1 microgram/kg of PEG-rHuMGDF had median increases in platelet counts of 16%, 12%, and 39%. Those receiving 0.3 and 1.0 microgram/kg of PEG-rHuMGDF had an increase in blood platelets of between 51% and 584%. Platelets rose from day 6 of PEG-rHuMGDF administration and continued to rise after stopping the drug. The platelet count peaked between days 12 and 18 and remained above 450 x 10(9)/L for up to 21 days. There were no alterations in white-blood-cell count or haematocrit, and low toxicity. Platelets taken from patients during PEG-rHuMGDF administration and at the time of peak platelet count were morphologically and functionally normal. INTERPRETATION: The potency with which PEG-rHuMGDF stimulates platelet production and its low toxicity indicate that this is likely to be a useful agent for the management of thrombocytopenia.

Dose-Response Relationship, Drug↗
PubMed2002

Ultrasensitive probing of the protein resistance of PEG surfaces by secondary ion mass spectrometry.

The highly sensitive surface analytical techniques X-ray photoelectron spectroscopy (XPS) and time-of-flight static secondary ion mass spectrometry (ToF-SIMS) were used to test the resistance of poly(ethylene glycol) (PEG) coatings towards adsorption of lysozyme (LYS) and fibronectin (FN). PEG coatings were prepared by grafting methoxy-terminated aldehyde-PEG (MW 5000 Da) onto two amino-functionalised surfaces with different amine group densities, generated by radio frequency glow discharge polymerisation of n-heptylamine and allylamine. Grafting was performed at the lower critical solution temperature to maximise the graft density of the PEG chains. XPS showed that the grafted density of PEG chains was slightly higher on the allylamine surface. XPS detected no adsorption of either protein on either PEG coating. ToF-SIMS analysis, on the other hand, found, in the positive ion spectra, minute but statistically significant signals assignable to amino acid fragment ions from both proteins adsorbed to the lower density PEG coating and from LYS but not FN on the higher density PEG coating. Negative ion spectra contained relatively more intense protein fragment ion signals for the lower density PEG coating but no changes assignable to adsorbed proteins on the higher density PEG coating. These results demonstrate the importance of utilising highly sensitive techniques to study protein adsorption on surfaces intended to be protein resistant, and that both positive and negative ion ToF-SIMS spectra should be acquired to probe for possible very low levels of protein adsorption.

Adsorption↗
PubMedDate not supplied

Poly(DMAEMA-NVP)-b-PEG-galactose as gene delivery vector for hepatocytes.

A block copolymer composed of cationic polymer and poly(ethylene glycol) (PEG) was used as a DNA carrier. Poly(2-(dimethylamino)ethyl methacrylate (DMAEMA)-co-N-vinyl-2-pyrrolidone (NVP)) having a terminal carboxylic group was synthesized by free radical polymerization using an initiator, 4,4'-azobis(4-cyanovaleric acid). The terminal carboxylic acid was activated by N-hydroxysuccinimide (NHS) with dicyclohexylcarbodiimide (DCC) and then conjugated with PEG-bis(amine). For specific gene targeting to asialoglycoprotein receptor of hepatocytes, a galactose moiety was incorporated into the PEG terminal end of poly(DMAEMA-NVP)-b-PEG by reductive coupling using lactose and sodium cyanoborohydride. RSV luciferase plasmid was used as a reporter gene, and in vitro gene transfection efficiency was measured in HepG2 human hepatocarcinoma cells. Poly(DMAEMA-NVP)-b-PEG-galactose/DNA complexes formed at 0.5-2 polymer/plasmid weight ratio had compacted structures around 200 nm particle size and exhibited slightly negative surface charge. These complexes were coated with a cationic, pH sensitive, endosomolytic peptide, KALA, to generate positively charged poly(DMAEMA-NVP)-b-PEG-galactose/DNA/KALA complex particles. In the presence of serum proteins, both the PEG block and the galactose moiety of poly(DMAEMA-NVP)-b-PEG-galactose greatly enhanced the gene transfection efficiency, which was very close to that of Lipofectamine plus. Irrespective of the presence of serum proteins, as the KALA/DNA weight ratio increased, the transfection efficiency of poly(DMAEMA-NVP)-b-PEG-galactose was enhanced due to the pH dependent endosomal disruptive property of KALA. This study demonstrates that sufficient transfection efficiency as high as that of commercial agent could be attained by judicious formulation of molecular engineered poly(DMAEMA-NVP)-b-PEG-galactose in combination with an endosomolytic peptide, KALA.

Amino Acid Sequence↗
PubMedDate not supplied

New PEGs for peptide and protein modification, suitable for identification of the PEGylation site.

New PEG derivatives were studied for peptide and protein modification, based upon an amino acid arm, Met-Nle or Met-beta Ala, activated as succinimidyl ester. PEG-Met-Nle-OSu or PEG-Met-beta Ala-OSu react with amino groups in protein-yielding conjugates with stable amide bond. From these conjugates PEG may be removed by BrCN treatment, leaving Nle or beta Ala as reporter amino acid, at the site where PEG was bound. The conjugation of PEG and its removal by BrCN treatment was assessed on a partial sequence of glucagone and on lysozyme as model peptide or protein. Furthermore, insulin, a protein with three potential sites of PEGylation, was modified by PEG-Met-Nle, and the PEG isomers were separated by HPLC. After removal of PEG, as reported above, the sites of PEGylation were identified by characterization of the two insulin chains obtained after reduction and carboxymethylation. Mass spectrometry, amino acid analysis and Edman sequence, could reveal the position of the reporter norleucine that corresponds to the position of PEG binding.

Dipeptides↗
PubMedDate not supplied

Structural and biophysical characterization of the 40 kDa PEG-interferon-alpha2a and its individual positional isomers.

The human recombinant Interferon-alpha(2a) (IFNalpha(2a)) is a potent drug (Roferon-A) to treat various types of cancer and viral diseases including Hepatitis B/C infections. To improve the pharmacological properties of the drug, a new pegylated form of IFNalpha(2a) was developed (PEGASYS). This 40 kDa PEG-conjugated IFNalpha(2a) ((40)PEG-IFNalpha(2a)) is obtained by the covalent binding of one 40 kDa branched PEG-polymer to a lysine side chain of IFNalpha(2a). (40)PEG-IFNalpha(2a) is a mixture of mainly six monopegylated positional isomers modified at K31, K134, K131, K121, K164, and K70, respectively. Here we report the detailed structural and biophysical characterization of (40)PEG-IFNalpha(2a) and its positional isomers, in comparison with IFNalpha(2a), using NMR spectroscopy, analytical ultracentrifugation, circular dichroism, fluorescence spectroscopy, and differential scanning calorimetry. Our results show that the three-dimensional structure of IFNalpha(2a) is not modified by the presence of the polymer in all positional isomers constituting (40)PEG-IFNalpha(2a). Regardless of where the PEG-polymer is attached, it adopts a very mobile and flexible random coil conformation, producing a shield for the protein without a permanent coverage of the protein surface. Hydrodynamic data indicate that the protein-attached PEG has a slightly more compact random-coil structure than the free PEG-polymer. Our results also provide evidence of significant structural and physicochemical advantages conferred by the pegylation: increase of the effective hydrodynamic volume and modification of the molecular shape, higher temperature stability, and reduced tendency for aggregation. These results are of tremendous pharmacological interest and benefit as was clinically shown with PEGASYS. This study constitutes a new standard for the characterization of pegylated proteins and enables an important step toward the understanding on a molecular level of the binding of (40)PEG-IFNalpha(2a) and its positional isomers to its cellular receptors.

Humans↗
PubMedDate not supplied

Synthesis of polyethylene glycol (PEG) derivatives and PEGylated-peptide biopolymer conjugates.

We synthesized a library of 50 poly(ethylene glycol) (PEG) derivatives to expand the extent of conjugation with biologically active molecules (biopolymers, peptides, drugs, etc.) and biomaterial substrates. The formation of PEG derivatives was confirmed with HPLC, (1)H and (13)C NMR. PEG derivatives were polymerized into networks in order to study the role of PEG and terminal functional groups in modulating the hydrophilicity of biomaterials and cell-biomaterial interaction. The resulting surface hydrophilicity and the number of adhered fibroblasts were primarily dependent on the PEG concentration with the molecular weight and the terminal functional group of PEG derivatives being less important. One of PEG derivatives, PEG-bis-glutarate, was utilized to link peptide sequences to gelatin backbone in the formation of novel biomedical hydrogels. PEG-peptide conjugates were characterized by mass spectroscopy. PEG-peptide modified gelatins were characterized by gel permeation chromatography.

Biopolymers↗