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  • 1
    Electronic Resource
    Electronic Resource
    Alkaline phosphatase-somatostatin hybrid proteins as probes for somatostatin-14 receptors (1992)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 14 (1992), S. 1-9 
    Details
    ISSN: 0887-3585
    Keywords: protein engineering ; cassette mutagenesis ; peptide hormone ; molecular modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: By inserting appropriate peptide ligands into surface loops on globular proteins, we expect to develop probes for the location, accessibility, and steric and electrostatic environment of these ligand-binding sites on their membrane-bound receptors. Three residues in a loop on the surface of E. coli alkaline phosphatase were substituted by an 18-residue peptide containing the receptor-binding segment of somatostatin-14 without significantly affecting the catalytic properties of the enzyme. This hybrid protein was then used to investigate the ligand-binding site of somatostatin receptors. Tryptic cleavage of the hybrid protein within the inserted sequence, and binding of the hybrid protein to antisomatostatin antibodies demonstrated the surface accessibility of the guest peptide. Both the wild-type enzyme and the hormone-enzyme hybrid displaced 125I-labeled somatostatin from rat brain membrane receptors only at high concentrations. How-ever, chemical cationization of the hybrid protein, which again did not disturb the phosphatase activity, enhanced its receptor-binding potency to a level only 23 times lower than that of somatostatin itself and 280 times higher than that of the cationized wild-type protein. This alkaline phosphatase/somatostatin hybrid protein appears, therefore, to be a suitable starting point for the development of probes for the steric and electrostatic environment of the ligand-binding site of somatostatin receptors. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340140103
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  • 2
    Electronic Resource
    Electronic Resource
    Semicontinuous seeded emulsion copolymerization of vinyl acetate and methyl acrylate (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 169-186 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The semicontinuous seeded emulsion copolymerization of vinyl acetate and methyl acrylate was investigated. The effect of type of process (starved process versus semi-starved process), type of feed (neat monomer addition versus monomer emulsion addition), amount of seed initially charged in the reactor, and feed rate on the time evolution of the overall conversion, copolymer composition, and polymer particle size was analyzed. It was found that, in the case of the starved process, both monomers, but mainly vinyl acetate, accumulated in the reactor. The preferential accumulation of vinyle acetate resulted in a drift of the copolymer composition. Both monomers accumulation and copolymer composition drift were reduced by increasing the amount of seed initially charged in the reactor and by decreasing the feed rate. For the semi-starved process, it was found that a vinyl aceatate rich copolymer was formed when a low methyl acrylate feed was used, whereas a methyl acrylate rich copolymer was obtained at high methyl acrylate feed rates. For both starved process and semi-starved process, the total number of polymer particles, after an initial increase, reached a plateau value which was the same in all of the experiments carried out. These results were analyzed by means of a mathematical model developed for this system.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1991.080290204
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  • 3
    Electronic Resource
    Electronic Resource
    Grafting reactions of vinyl acetate onto poly[(vinyl alcohol)-co-(vinyl acetate)] (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 2581-2594 
    Details
    ISSN: 0887-624X
    Keywords: grafting ; poly(vinyl alcohol) ; poly(vinyl acetate) ; vinyl acetate ; methine carbon ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The grafting preference of vinyl acetate onto the methine carbon of poly(vinyl alcohol) (PVOH) versus the acetate group of poly(vinyl acetate) (PVAc) was determined as part of an attempt to prepare novel branched PVOH from partially hydrolyzed PVAc. The results showed long chain grafting on the acetate groups of the PVAc units rather than the methine carbons of the PVOH or PVAc units. Decreasing the monomer or initiator concentration decreased the molecular weight of the graft copolymer formed. Of the initiators studied, ammonium persulfate gave the largest increase in copolymer molecular weight. Both hydrolysis and reacetylation combined with gel permeation chromatography (GPC) and 13C-NMR of the fully hydrolyzed material were used to estimate the number and location of grafts. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Miniemulsion copolymerization of vinyl acetate and butyl acrylate. I. Differences between the miniemulsion copolymerization and the emulsion copolymerization processes (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 24 (1986), S. 861-874 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Differences between the emulsion copolymerization and miniemulsion copolymerization processes, in terms of emulsifier adsorption, emulsion stability, polymerization kinetics, copolymer composition and dynamic mechanical properties were studied for the comonomer mixture of 50:50 molar ratio vinyl acetate (VA+) - butyl acrylate (BuA), using sodium hexadecyl sulfate (SHS) as a surfactant and hexadecane (HD) as a co-surfactant. The use of hexadecane with the appropriate SHS initial concentration led to a higher adsorption of surfactant, smaller droplet size, higher stability of the emulsions, lower polymerization rates, and larger latex particle size. The copolymer composition during the initial 70% conversion was found to be less rich in Vac monomer units for the miniemulsion process. The dynamic mechanical properties of the copolymer films showed less mixing between the BuA-rich core and the VAc-rich shell in the miniemulsion latexes compared to the conventional latex films.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1986.080240505
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  • 5
    Electronic Resource
    Electronic Resource
    Polyamides incorporating phosphine oxide groups. I. Wholly aromatic polymers (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 1561-1566 
    Details
    ISSN: 0887-624X
    Keywords: phosphine oxide ; polyamide ; polycondensation ; thermal properties ; fire-retardant materials ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Five novel polyamides incorporating phosphine oxide groups have been synthesized by the condensation reaction of bis(4-carboxyphenyl)phenylphosphine oxide with a series of aromatic diamines. The thermal properties of these polymers were investigated by differential scanning calorimetry and thermogravimetric analysis. Glass transition temperatures in the 225-254°C range were recorded, together with good thermooxidative stability (5% weight loss occurring at 〉420°C) and high char yield upon prolonged heating at 650-800°C (24-50%). Also, good solubility in aprotic polar solvents was observed for all polyamides synthesized. © 1996 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    The modification of polysulfone by metalation (1988)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 26 (1988), S. 123-127 
    Details
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1988.140260211
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  • 7
    Electronic Resource
    Electronic Resource
    Single-stranded DNA binding proteins (SSBs) from prokaryotic transmissible plasmids (1991)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 9 (1991), S. 120-134 
    Details
    ISSN: 0887-3585
    Keywords: plasmid SSBs ; protein and DNA sequence ; single-stranded DNA binding proteins ; helix destabilizing proteins ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The DNA and protein sequences of single-stranded DNA binding proteins (SSBs) encoded by the plP71a, plP231a, and R64 conjugative plasmids have been determined and compared to Escherichia coli SSB and the SSB encoded by F-plasmid. Although the amino acid sequences of all of these proteins are highly conserved within the NH2-terminal two-thirds of the protein, they diverge in the COOH-terminal third region. A number of amino acid residues which have previously been implicated as being either directly or indirectly involved in DNA binding are conserved in all of these SSBs. These residues include Trp-40, Trp-54, Trp-88, His-55, and Phe-60. On the basis of these sequence comparisons and DNA binding studies, a role for Tyr-70 in DNA binding is suggested for the first time. Although the COOH-terminal third of these proteins diverges more than their NH2-terminal regions, the COOH-terminal five amino acid residues of all five of these proteins are identical. In addition, all of these proteins share the characteristic property of having a protease resistant, NH2-terminal core and an acidic COOH-terminal region. Despite the high degree of sequence homology among the plasmid SSB proteins, the F-plasmid SSB appears unique in that it was the only SSB tested that neither bound well to poly(dA) nor was able to stimulate DNA polymerase III holoenzyme elongation rates. Poly [d(A-T)] melting studies suggest that at least three of the plasmid encoded SSBs are better helix-destabilizing proteins than is the E. coli SSB protein.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340090206
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  • 8
    Electronic Resource
    Electronic Resource
    Reaction path and free energy calculations of the transition between alternate conformations of HIV-1 proteaseThe content of this publication does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organization imply endorsement by the U.S. Government. (1998)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 32 (1998), S. 7-16 
    Details
    ISSN: 0887-3585
    Keywords: conformational change ; free energy calculations ; HIV protease ; molecular dynamics simulations ; protein structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Two different structures of ligand-free HIV protease have been determined by X-ray crystallography. These structures differ in the position of two 12 residue, β-hairpin regions (or “flaps”) which cap the active site. The movements of the flaps must be involved in the binding of substrates since, in either conformation, the flaps block the binding site. One of these structures is similar to structures of the ligand-bound enzyme; however, the importance of both structures to enzyme function is unclear. This transformation takes place on a time scale too long for conventional molecular dynamics simulations, so the process was studied by first identifying a reaction path between the two structures and then calculating the free energy along this path using umbrella sampling. For the ligand-free enzyme, it is found that the two structures are nearly equally stable, with the ligand-bound-type structure being less stable, consistent with X-ray crystallography data. The more stable open structure does not have a lower potential energy, but is stabilized by entropy. The transition occurs through a collapse and reformation of the β-sheet structure of the conformationally flexible, glycine-rich flap ends. Additionally, some problems in studying conformational changes in proteins through the use of a single reaction path are addressed. Proteins 32:7-16, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis and properties of new crystalline poly(arylene ether)s containing pendant benzoyl groups (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 605-611 
    Details
    ISSN: 0887-624X
    Keywords: poly(arylene ether)s ; pendant benzoyl groups ; 2,5-difluoro-4-benzoyl-benzophenone ; hydroquinone derivatives ; thermostability ; semi-crystalline polymer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(arylene ether)s (3) containing pendant benzoyl groups were prepared by the aromatic substitution reaction of 2,5-difluoro-4-benzoylbenzophenone (2) with hydroquinone (1a) and methylhydroquinone (1b) in the presence of potassium carbonate in N,N-dimethylacetamide. The polycondensation proceeded smoothly at 165°C and produced poly(arylene ether)s with inherent viscosities up to 0.8 dL/g. The polymer (3b) derived from methylhydroquinone was quite soluble in common organic solvents and could be processed into uniform films from solutions. On the other hand, the polymer (3a) derived from hydroquinone was only soluble in pentafluorophenol and methanesulfonic acid and had a high crystallinity. These polymers showed 10% weight losses at around 420 and 490°C in nitrogen. Polymer 3b also showed good tensile strength and tensile moduli. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 605-611, 1997
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Structure-property relationships of ionene polymers (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 87-109 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of new ionenes was accomplished by the reaction of novel diamines and dihalides. A new class of crosslinkable ionenes was made possible by the synthesis of tertiary diamines with acrylate functionality, generated ultimately from diepoxides and secondary amines. Other tertiary diamines were produced by endcapping of diols with tolylene diisocyanate, followed by reaction with N,N-dimethylethanolamine and also termination of living poly(tetrahydrofuran) polymer with dimethylamine. New dihalides were produced by the opening of diepoxides with ω-bromoacids.These diamines and dihalides underwent Menschutkin reactions providing novel ionenes for structure-property relationship studies. Correlations were drawn concerning amine nucleophilicity, dihalide nucleofugascity, and molecular weight. Stress-strain and thermal data reflected the effects of ionic domains and large flexible segments in the polymers. Also considered were the electrical conductivity, moisture-vapor transmission, and oxygen permeability of these materials.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1987.080250109
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