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  • Two-dimensional polyacrylamide gel electrophoresis  (29)
  • Physics  (5)
  • Wiley-Blackwell  (34)
  • 1
    Electronic Resource
    Electronic Resource
    Effect of the directionality of the ester group on the formation of hairpins in polyesters containing naphthalene and a flexible spacer (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1127-1133 
    Details
    ISSN: 0887-6266
    Keywords: excimer ; fluorescence ; molecular dynamics ; naphthalene ; polyester ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Steady-state fluorescence measurements and molecular dynamics simulations have been used to study the intramolecular formation of excimers in five model compounds for polyesters containing naphthalene groups separated by flexible spacers. The model compounds are derived from 2-hydroxynaphthalene and HOOC—(CH2)n—COOH, n = 2-6. The ratio of the intensity of excimer and monomer emissions, ID/IM, is nearly independent of the viscosity of the medium, η, over the range covered in dilute solution. Although ID/IM is always very small, it shows an odd-even effect for the first four members of the series, with maxima when n is odd. Molecular dynamics simulations provide an explanation for the small values of ID/IM, their weak dependence on η, and the trend of ID/IM with n. The results for the present series of model compounds are compared with previous work, which reported larger values of ID/IM, and a stronger dependence of ID/IM on η, for bichromophoric compounds derived from 2-naphthoic acid and aliphatic glycols, where the direction of the ester groups is reversed. The origin of the difference in the behavior of ID/IM in the two series is identified. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1127-1133, 1997
    Additional Material: 9 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Phase behavior of a substituted poly(paraphenylene): Poly(para-2,5-didecyl-p-phenylene) (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 49-54 
    Details
    ISSN: 0887-6266
    Keywords: substituted poly(paraphenylene) ; phase transitions ; synchrotron radiation ; mesophases ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal behavior of poly(para-2,5-didecyl-p-phenylene) has been investigated by differential scanning calorimetry and real time X-ray diffraction. Poly(para-2,5-didecyl-p-phenylene) is a semicrystalline material that crystallizes in a layered structure. The system exhibits two thermal transitions in the investigated temperature range. The first one, occurring at lower temperatures, provokes a reduction of the layered spacing accompanied by an appreciable disordering of the lateral side chains. Above the first transition the material is shearable, highly viscous, and birefringent. Thus, we have associated this transition to the formation of a layered mesophase. The higher temperature transition exhibits a twofold endothermic DSC peak and is characterized by the disappearance of X-ray diffracted intensity. At temperatures above the second transition the system presents the characteristics of an isotropic melt. Consequently, we have associated this transition with the complete disordering of the polymeric backbones. By following an appropriate thermal treatment it has been shown that the twofold shape of the endotherm characterizing the higher temperature transition can be changed into a single endotherm. This effect has been interpreted as being due to the kinetics of main-chain ordering. This ordering seems to proceed by the initial growth of domains with a high level of order followed by the subsequent increase of these domains through the inclusion of less ordered material. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 49-54, 1998
    Additional Material: 8 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Excluded-volume effect for various chain models. I. Application to optical anisotropy and end-to-end distance of linear polymers (1974)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 12 (1974), S. 417-429 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A study of the effect of excluded volume on the mean-square optical anisotropy 〈γ2〉 and the mean-square end-to-end distance 〈R2〉 has been carried out for polymer chains of up to 2000 bonds. The calculations have been made for models assuming (a) equiprobability of internal rotations and (b) interdependence of short-range intramolecular interactions. All the results indicate that 〈γ2〉 is practically insensitive to the excluded-volume effect. Concomitantly the behavior of 〈R2〉 has been analyzed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1974.180120214
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  • 4
    Electronic Resource
    Electronic Resource
    The orientation of amorphous chains in spherulites (1975)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 13 (1975), S. 1991-2029 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A theory for amorphous orientation in spherulitic polymers is presented based upon a consideration of conformational changes in the chains, loops, and cilia located between crystalline lamellae within a spherulite which is assumed to undergo an affine deformation. Chain statistics are worked out on the basis of (a) an analytical method involving random walks on a cubic lattice between barriers following a technique proposed by DiMarzio and Rubin and (b) a Monte Carlo computer simulation on a tetrahedral lattice. The latter method is considered more appropriate in view of the chain constraints such that lattice geometry becomes important. Values of the amorphous orientation are calculated as a function of the degree of crystallinity, initial lamellar separation, mole fraction of bonds in amorphous chains of each type, and chain lengths of each type of amorphous chain. It is found that tie chains are the principal contributor to amorphous orientation and the amount increases with increasing fraction and decreasing length of these. Results are compared with measurements of amorphous orientation by the birefringence x-ray and the infrared dichroism technique. It is concluded that the tie chains must be initially quite highly elongated and that the assumed affineness of spherulite deformation is not closely obeyed.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1975.180131012
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  • 5
    Electronic Resource
    Electronic Resource
    Polymerization of N-(fluoro phenyl) maleimidesPaper presented in part before the IUPAC, International Symposium on Macromolecules (SIM) held in Rio de Janeiro, Brazil, 26-31 July 1974. (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 81-96 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(N-aryl maleimide)s of characteristic structures have been synthesized and some of their physical properties studied. These include N-(2-fluoro phenyl), N-(3-fluoro phenyl), N-(4-fluoro phenyl), N-(2,4-difluoro phenyl), N-(2,5-difluoro phenyl), N-(2,3,5,6-tetrafluoro phenyl), and N-(pentafluoro phenyl). The polymerization of N-(fluoro phenyl) maleimides by free-radical initiation in bulk or in solution and by anionic catalyst have been studied to compare the characteristics of polymerization by γ-ray irradiation with that by free-radical initiation. The polymers were characterized by elemental analysis, intrinsic viscosity, spectroscopy (IR and NMR), programmed thermogravimetric analysis, and x-ray diffraction. Spectra of polymers prepared by radiation and anionic polymerization were nearly identical with those of polymers prepared by free-radical polymerization initiated by AIBN in bulk or in solution and by the self-initiated thermal polymerization. A variety of reaction conditions were tried, but all attempts to change the molecular structure of the polymers were unsuccessful. Rates of thermal degradation for poly[N-(fluoro phenyl) maleimide]s have been analyzed by using a multiple-heating-rate procedure. Overall activation energy, order of reaction, and frequency factor have been evaluated. On the basis of the comparison between the overall activation energy of the thermal degradation of poly[N-(fluoro phenyl) maleimide]s and NMR spectra of their corresponding monomers, it can be concluded that the 1H shifts due to ethylenic protons are so characteristic in sign and magnitude as to be useful in thermal stability elucidation. Some qualitative explanations were given on the stability of these polymers as affected by the type and size of the substituent. The x-ray diffractograms of all samples show two rather broad peaks indicative of noncrystalline structures. The location of the peaks does not depend upon preparation conditions and temperature. Poly(N-maleimide)s of fluoroanilines have not been hitherto described.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.170170109
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  • 6
    Electronic Resource
    Electronic Resource
    Phenotyping of apolipoprotein E using immobilized pH gradient gels for one-dimensional and two-dimensional separations (1995)
    Weinheim : Wiley-Blackwell
    Electrophoresis 16 (1995), S. 1184-1186 
    Details
    ISSN: 0173-0835
    Keywords: Apolipoprotein E ; Immobilized pH gradient ; Phenotyping ; Immunoblotting ; Two-dimensional polyacrylamide gel electrophoresis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Apolipoprotein E (apo E) is a normal component of several classes of plasma lipoproteins. Apo E phenotypes are closely related to total cholesterol, low density lipoprotein (LDL)-cholesterol and apo B concentration. The apo E 2/2 phenotype is related to the type III hyperlipoproteinemia due to the defective binding of apo E-2 to the hepatic receptors. The apo E 4/4 phenotype has been reported to be present in most elderly people suffering from the Alzheimer disease, and is associated with increased risk of coronary heart disease and Creutzfeld-Jakob disease. Therefore, apo E phenotyping is essential. The method described here uses a precast immobilized pH gradient, avoids time-consuming separation of lipoproteins from plasma, needs no pretreatment with neuraminidase and involves highly sensitive enhanced chemiluminescence for visualization. Therefore it has many advantages over previously published methods.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.11501601196
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  • 7
    Electronic Resource
    Electronic Resource
    The yeast SWISS-2DPAGE database (1996)
    Weinheim : Wiley-Blackwell
    Electrophoresis 17 (1996), S. 556-565 
    Details
    ISSN: 0173-0835
    Keywords: Yeast ; SWISS-2DPAGE ; Two-dimensional polyacrylamide gel electrophoresis ; Protein database ; Protein mapping ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The systematic sequencing of the yeast genome will soon be completed. A new challenge has been launched by the EUROFAN (European Functional Analysis) project whose goal is to elucidate the physiological and biochemical function of newly discovered open reading frames (ORF) from yeast. One of the approaches is to use protein-based technologies such as two-dimensional gel eletrophoresis and protein identification in order to establish a yeast reference map. Modified protein patterns can be compared to the reference map which hopefully will help identify changes related, for example, to growth processes or developmental events. This paper describes the yeast SWISS-2DPAGE database in which charge separation was obtained using immobilized pH gradient (IPG). Proteins identified by gel comparison, amino acid composition analysis and/or microsequencing are recorded and described in an accessible uniform format. We have identified more than one hundred polypeptides, several of which were newly mapped. In addition, the yeast SWISS-2DPAGE database can be freely accessed through the World Wide Web (WWW) network on the ExPASy molecular biology server.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150170326
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  • 8
    Electronic Resource
    Electronic Resource
    Spermatocytes and round spermatids of rat testis: The difference between in vivo and in vitro protein patterns (1997)
    Weinheim : Wiley-Blackwell
    Electrophoresis 18 (1997), S. 548-552 
    Details
    ISSN: 0173-0835
    Keywords: Testis ; Spermatogenesis ; In vitro translation ; Two-dimensional polyacrylamide gel electrophoresis ; Two-dimensional polyacrylamide gel electrophoresis ; Protein map ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: During mammalian spermatogenesis meiotic cell division and spermiogenesis occurs. Gene expression during this process is temporally regulated at the transcriptional and translational levels but the mechanisms are not well understood. In this publication we have investigated the synthesis of proteins in vitro to detect the proteins with a high metabolic turnover and to compare them with the in vivo protein map. RNA of spermatocytes and round spermatid cell populations, purified by centrifugal elutriation, and total testis was isolated. The poly A+ mRNA fraction was translated using a rabbit reticulocyte lysate. The translation products were separated by two-dimensional (2-D) gel electrophoresis using nonlinear 3.5-10 immobilized pH gradients for the first-dimensional separation. The gels with 35S-translated proteins were transferred onto polyvinylidene difluoride (PVDF) membranes and scanned using a phosphorimager. A highly reproducible and complex protein pattern was obtained using this methodology. Only rat testis messages were translated. Using Melanie 2 software we could compare and detect more than 1000 proteins on 2-D radioactive images. Some changes could be observed in protein expression between the different cell types but they were not statistically significant. The comparison between the 2-D rat testis map and the in vitro translated patterns show no matching between any spots. This result suggests that the post-transcriptional modifications occurring in the reticulocyte system are not the same as those that occur in vivo in the testis. Rabbit reticulocyte proteins were detected by staining PVDF membranes with colloidal gold. Rat testis and reticulocyte patterns were completely different.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150180335
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  • 9
    Electronic Resource
    Electronic Resource
    Specific sample preparation in colorectal cancer (1997)
    Weinheim : Wiley-Blackwell
    Electrophoresis 18 (1997), S. 622-624 
    Details
    ISSN: 0173-0835
    Keywords: Two-dimensional polyacrylamide gel electrophoresis ; Antibodies monoclonal diagnostic use ; Colonic neoplasms ; Rectal neoplasms ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Large tissue samples from ten patients operated for colorectal cancer were prepared in the operating room in iced phosphate buffered saline, containing ethylene diaminetetraacetic acid and protease inhibitors. After cutting the specimens into small fragments, the tissues were gently pressed through a steel mesh. Membranes were permeabilized in chilled ethanol 70% to allow cytosolic fluoresceine isothiocyanate labeling, performed with anti-cytokeratin (CAM 5.2) antibodies. Samples were quantitatively sorted with a fluorescence activated cell sorter (FACS) and denatured before processing separation by two-dimensional electrophoresis on polyacrylamide gels. This procedure made it possible to sample about 4 × 107 viable normal and tumoral cells before fixation, and up to 4 × 106 cells after FACS. The gels run before and after fixation showed no major differences. The rate of cytokeratin-positive cells in the samples was the following (mean, Cl 5-95%): mucosa 29.5% (8.9-66.7%), tumor 44.3% (6.6-94.8%). The epithelial cell content in colorectal cancer and normal mucosa shows important intersample variations. This is important for any comparison of fresh samples, whether at DNA, RNA, or at the protein level. We propose a method allowing the preparation of pure epithelial cell samples from normal and tumoral colonic fresh mucosa.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150180346
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  • 10
    Electronic Resource
    Electronic Resource
    Extraction of membrane proteins by differential solubilization for separation using two-dimensional gel electrophoresis (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 837-844 
    Details
    ISSN: 0173-0835
    Keywords: Membrane proteins ; Solubility ; Two-dimensional polyacrylamide gel electrophoresis ; Proteome ; Escherichia coli ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: We describe the extraction and enrichment of membrane proteins for separation by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) after differential solubilization of an Escherichia coli cell lysate. In a simple three-step sequential solubilization protocol applicable for whole cell lysates, membrane proteins are partitioned from other cellular proteins by their insolubility in solutions conventionally used for isoelectric focusing (IEF). As the first step, Tris-base was used to solubilize many cytosolic proteins. The resultant pellet was then subjected to conventional solubilizing solutions (urea, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, dithiothreitol, Tris, carrier ampholytes). Following the completion of this step, 89% of the initial E. coli sample mass was solubilized. Finally, the membrane protein rich pellet was partially solubilized using a combination of urea, thiourea, tributyl phosphine and multiple zwitterionic surfactants. Using N-terminal sequence tagging and peptide mass fingerprinting we have identified 11 membrane proteins from this pellet. Two of these outer membrane proteins (Omp), OmpW and OmpX, have previously been known only as an open reading frame in E. coli, while OmpC, OmpT and OmpTOLC have not previously been identified on a 2-D gel. The prefractionation of an entire cell lysate into multiple fractions, based on solubility, results in simplified protein patterns following 2-D PAGE using broad-range pH 3.5-10 immobilized pH gradients (IPGs). Additional advantages of sample prefractionation are that protein identification and gel matching, for database construction, is a more manageable task, the procedure requires no specialized apparatus, and the sequential extraction is conducted in a single centrifuge tube, minimizing protein loss.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150190539
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