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  • 1
    Electronic Resource
    Electronic Resource
    Monte Carlo simulations of hydrophobic polyelectrolytes. Evidence for a structural transition in response to increasing chain ionization (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 2715-2723 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Monte Carlo simulation has been used to study the configurational properties of a lattice-model isolated polyelectrolyte with attractive segment–segment interaction potentials. This model provides a simple representation of a hydrophobic polyelectrolyte. Configurational properties were investigated as a function of chain ionization, Debye screening length, and segment–segment potential. For chains with highly attractive segment–segment potentials (i.e., hydrophobic chains), large, global changes in polymer dimensions were observed with increasing ionization. The transformation from a collapsed chain at low ionization to an expanded chain at high ionization becomes increasingly sharp (i.e., occurs over a smaller range of ionization) with increasing chain hydrophobicity. The ionization-induced structural transitions for this model hydrophobic polyelectrolyte are analogous to pH-induced transitions seen in real polyelectrolytes and gels. These studies suggest a simple explanation for such transitions based on competing hydrophilic and hydrophobic interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458910
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  • 2
    Electronic Resource
    Electronic Resource
    Monte Carlo simulations of hydrophobic weak polyelectrolytes: Titration properties and pH-induced structural transitions for polymers containing weak electrolytes (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 8767-8774 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Monte Carlo simulation has been used to study titration and configurational properties of an isolated hydrophobic polymer containing weakly-ionizable groups. Using a cubic lattice, simulations were performed in the grand canonical ensemble to include the effect of the local charge environment on the ionization of weak electrolyte segments. Properties were studied as a function of polymer hydrophobicity, fraction of ionizable segments, solution ionic strength, and pH. The polymer segments experienced three types of competing interaction: excluded volume, attractive nearest-neighbor forces which account for the net balance of segment–segment, segment–solvent, and solvent–solvent interactions, and long-range electrostatic forces between ionized segments, calculated with a screened Debye–Hückel potential. Simulations show that the model chain expands with chain ionization, which depends on solution pH. As the chain becomes increasingly charged, the ionization process becomes more difficult because of rising local charge density around the ionizable segments. The effect of rising local charge density increases for larger fractions of ionizable groups, with increased hydrophobicity and with low ionic strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463346
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Monte Carlo simulations of a hydrophobic weak polyelectrolyte. Charge distribution as a function of conformation (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 4231-4232 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Monte Carlo simulations were performed to obtain the distribution of charged segments around the center of mass in a lattice-model, isolated weak polyelectrolyte with attractive segment–segment (hydrophobic) interactions. The charge distribution (relative to the mean ionization for a given state) is shown to depend essentially on chain conformation (stiffness).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466227
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Phase equilibria for aqueous protein/polyelectrolyte gel systems (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 2335-2353 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A molecular-thermodynamic analysis is directed toward predicting the partitioning of aqueous proteins into charged hydrogels. This analysis takes into account size exclusion by the network, electrostatic interactions, and the osmotic-pressure difference between a hydrogel and its surrounding solution. Electrostatic interactions in the polyelectrolyte gel can be described by Debye - Hückel theory, or the Mean Spherical Approximation, or Katchalsky's cell model for polyelectrolyte solutions. The cell model gives best agreement with experimental partition coefficients for cytochrome c. The quasi-electrostatic potential difference between a gel and its surrounding solution demonstrates how the electrostatic contribution to the protein partition coefficient depends on protein charge, gel-charge density, and solution ionic strength. Finally, a qualitative guide is presented for design of a polyelectrolyte gel such that it exhibits specified swelling and partitioning properties.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420823
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Sorption of lysozyme by HEMA copolymer hydrogels (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 225-234 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Sorption of lysozyme by 2-hydroxyethyl methacrylate (HEMA) copolymer hydrogels was studied as a function of pH and gel composition. Three types of HEMA gels were synthesized: neutral (HEMA), acidic (HEMA + acrylic acid), and basic (HEMA + dimethylaminoethyl methacrylate). Each gel was synthesized at four initial volume fractions to obtain different equilibrium swelling ratios and microstructures. Sorption as a function of time was measured for each gel at pH 7, 7.5, and 8. The rate of uptake by the acidic gels was more rapid than that by the neutral gels: To sorb 90% of the protein required only 1 h for the acidic gels but 15 days for neutral gels. Lysozyme did not adsorb or partition into the basic gels. The fractional approach to equilibrium was most rapid for the more swollen gels, and the effect of pH was small. The results reported here may be useful for rational design of new biomaterials where it is desirable to know the relative magnitude of the effects of composition, synthesis, and pH on protein sorption. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 6
    Electronic Resource
    Electronic Resource
    Characterization of size-exclusion effects in highly swollen hydrogels: Correlation and prediction (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 59 (1996), S. 1337-1346 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The literature provides several size-exclusion theories to predict solute exclusion by highly swollen hydrogels. Theoretical calculations are compared to the experimental data of Walther et al. (1993) for partitioning of poly(ethylene glycol)s and poly(ethylene oxide)s of various molecular weight into hydrogels made of poly-N-isopropylacrylamide or poly-2-hydroxyethyl methacrylate/dimethylaminoethyl methacrylate. Experimental size-exclusion curves can be correlated almost equally well by theories which characterize the gel as a collection of pores or of fibers; differences between these two theories are important only for partition coefficients near zero or unity. The experimental data of Walther et al. can be predicted best by Schnitzer's uniform pore model. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 7
    Electronic Resource
    Electronic Resource
    Electrophoresis of DNA in novel thermoreversible matrices (1996)
    Weinheim : Wiley-Blackwell
    Electrophoresis 17 (1996), S. 1460-1469 
    Details
    ISSN: 0173-0835
    Keywords: DNA ; Capillary electrophoresis ; Slab electrophoresis ; Thermoreversible matrices ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: We demonstrate the feasibility of temperature-sensitive polymers as novel matrices for capillary and slab electrophoresis of DNA. These matrices combine the ease-of-use of agarose with resolution properties of polyacrylamide. Two classes of matrices are used: (i) aqueous suspensions of gel microspheres and (ii) solutions containing uncross-linked temperature-sensitive polymers. When heated, the viscosity of these solutions drops dramatically because of the phase transition behavior of these polymers, and therefore these formulations are easy to pour or load. Results are presented for separation of double-stranded DNA fragments (〈 2000 bp) in capillary, tube, and slab electrophoresis. Preliminary results are also presented for separation of single-stranded sequencing fragments by capillary electrophoresis. In the tube format, good resolution was obtained for ΦX174/HaeIII fragments. In the slab format, excellent resolution of double-stranded DNA was obtained, including simulaneous separation of a 10 bp ladder up to 150 base pairs. In the capillary format, pBR322/MspI fragments were completely resolved, and single-base resolution of sequencing fragments was obtained up to 150 bases. We believer that temperature-sensitive polymers represent a new and promising class of electrophoretic media.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150170910
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