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  • Wiley-Blackwell  (20,073)
  • American Physical Society  (16,829)
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  • 1995-1999  (30,965)
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  • 1995-1999  (30,965)
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  • 101
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    Electronic Resource
    Mass spectrometry, high performance liquid chromatography, and brain peptides (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996), S. 257-264 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper is a personal recollection of some of the events and research that surrounded the amino acid sequence determination of the hypothalamic releasing factor, TRF (now known as TRH), by mass spectrometry (MS), and the development of reverse phase high performance liquid chromatography (RP-HPLC) MS and tandem MS (MS/MS) methods for the qualitative and quantitative analysis of native opioid neuropeptides in human pituitary tissue extracts. © 1996 John Wiley & Sons, Inc.
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  • 102
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    Peptide chemistry: Development of high performance liquid chromatography and capillary zone electrophoresisDedicated to the late Dr. Roger Burgus. (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996), S. 265-317 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The development of relatively non-compressible supporting media of small particle size as well as pumps which deliver constant flow rates at high pressures has enabled investigators to perform rapid, high resolution liquid chromatography for more than two decades. Studies initiated in this laboratory in 1975, evaluating the compatibility of unprotected peptides with commercially available chromatographic supports and development of solvent systems ultimately led to separations not previously observed with both synthetic peptides and native peptides from tissue extracts. It was rapidly realized however, that recovery of certain molecules could be problematic. To meet the challenges presented by the isolation of natural hormones (such as corticotropin releasing factor and growth hormone releasing hormone) and proteins (such as inhibin and activin) and the need for large quantities of highly purified peptides for clinical investigations, our group invested heavily in identifying new supports (high carbon loading and 300 Å pore sizes) and solvent systems (triethylammonium phosphate and trifluoroethanol) compatible with reverse phase, size exclusion and ion exchange chromatographies from a practical and economical perspective. More recently, we have contributed to the identification of unusual buffer systems (inclusive of organic modifiers) compatible with capillary zone electrophoresis that will both modulate the capillaries' selectivity, increase resolution and serve as an orthogonal approach to determining peptide purity. From a pragmatic point of view, in this paper we highlight the original and timely contributions (technical and strategical) of this laboratory in the field of analytical and preparative high performance liquid chromatography and capillary zone electrophoresis of synthetic and native biologically active peptides and proteins over the past twenty years. © 1996 John Wiley & Sons, Inc.
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  • 103
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    Masthead (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360400401
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  • 104
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    Interaction of oxytocin with Ca2+: I. CD and fluorescence spectral characterization and comparison with vasopressin (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996), S. 433-443 
    Details
    ISSN: 0006-3525
    Keywords: hormone-receptor interaction ; Ca2+-hormone interaction ; bioactive conformation ; structure-activity correlation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Extracellular Ca2+ is required for the action of oxytocin and both the hormone and its receptor have binding sites for divalent metal cations. To characterize the cation-bound form of oxytocin, we monitored the binding of Ca2+ and Mg2+ to oxytocin as well as peptides representing its ring and tail regions in trifluoroethanol, a lipid-mimetic solvent, using CD and fluorescence spectroscopy. Binding Ca2+ (Kd ˜ 50 μM) caused drastic CD and fluorescence changes leading to a helical conformation. Mg2+ caused CD changes smaller than and opposite to Ca2+. However, the helical structure was enhanced when both Ca2+ and Mg2+ were present together. CD changes in the tail peptide of oxytocin showed its ability to bind Ca2+ and Mg2+ whereas the vasopressin tail peptide did not bind either cation. CD spectral changes on Ca2+ and Mg2+ binding to tocinoic acid (the ring moiety of oxytocin) were much smaller than those of oxytocin. These data suggest that the tail segment of oxytocin potentiates Ca2+ binding by the ring. While vasopressin displayed a CD spectrum similar to that of oxytocin, CD spectra of its cation-bound forms were markedly different from those of oxytocin; the Ca2+-induced CD changes in vasopressin were very much smaller and of opposite sign, and Mg2+-induced ones significantly larger than in oxytocin. Taken together, our observations bring out the structural differences between oxytocin and vasopressin in the context of their interaction with Ca2+ and Mg2+. This may be relevant to understanding the differences in the bioactive conformations and receptor interactions of the two hormones. © 1997 John Wiley & Sons, Inc. Biopoly 40: 433-443, 1996
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  • 105
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    Synthesis and antinociceptive activity of peptides related to interleukin-1β193-195 Lys-Pro-Thr (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996), S. 479-484 
    Details
    ISSN: 0006-3525
    Keywords: structure-activity relationships ; analgesic peptides ; antinociceptive activity ; interleukin-1β193-195 ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: To obtain information about the structure-activity relationships of analgesic peptides, we modified the previously reported tripeptide, H-Lys-Pro-Thr-OH (C). The proline part in C was replaced with various analogues of unconventional amino acids {(3aS, 7aS)-octahydroindole-2-carboxylic acid (Oic), (S,S,S,)-2-azabiciclo [3.3.0] octane-3-carboxylic acid (Aoc), D-Aoc, and (2S, 4R)-hydroxyproline (Hyp)} with varying lipophilic, steric, and conformational properties, and alternatively with Lys and Orn in the lysine part. Moreover, the threonine part was changed to various natural amino acids (Ser, Thr, Val, Leu). All the compounds were screened in vivo for their analgesic effects in mouse writhing test. Compound 24 (H-Orn-Hyp-Val-OH), the most active compound within the series, showed an ED50 value of 10 mg/kg, which is comparable with the ED50 values exhibited by indometacin (4.1 mg/kg) and the dipeptide H-Lys-D-Pro-OH (6.9 mg/kg), both used as reference drugs. © 1997 John Wiley & Son's, Inc. Biopoly 40: 479-484, 1996
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  • 106
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    Preferred conformation of peptides rich in alicyclic Cα,α-disubstituted glycines (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996), S. 519-522 
    Details
    ISSN: 0006-3525
    Keywords: conformational analysis, of peptides ; disubstituted glycines, peptides rich in ; Fourier transform ir absorption, of peptides ; 310-helical conformation, in peptides ; Cα-methylated α-amino acids, peptides rich in ; nmr, of peptides ; peptide conformation ; x-ray diffraction, of peptides ; β-turn conformation, in peptides ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational preferences of the alicyclic Cα,α-disubstituted glycines Acnc (1-amino-1-cycloalkane-carboxylic acid; n = 4, 7, 9, 12) were assessed in selected model compounds, including homopeptides and Ala (or Aib, α-aminoisobutyric acid)/Acnc peptides containing a small total number of residues, by Fourier transform ir absorption, 1H-nmr, and x-ray diffraction analyses. The results obtained indicate that β-turn and 310-helical structures are preferentially adopted by short peptides rich in these cycloaliphatic α-amino acids. © 1997 John Wiley & Sons, Inc. Biopoly 40: 519-522, 1996
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    Threonine6-bradykinin: Conformational study of a flexible peptide in dimethyl sulfoxide by NMR and ensemble calculations (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996), S. 561-569 
    Details
    ISSN: 0006-3525
    Keywords: bradykinin ; nmr ; peptide conformation ; ensemble averages ; distance geometry calculations ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation of the natural peptide threonine6 (Thr6)-bradykinin, Arg1-Pro2-Pro3-Gly4-Phe5-Thr6-Pro7-Phe8-Arg9, was investigated in DMSO by nmr spectroscopy and computer simulations. The structural analysis of the Thr6-peptide is made particularly interesting by the fact that despite the high sequence homology with native bradykinin (only one conservative substitution: Ser6/Thr6) there is a marked and significant difference in the biological profiles of the two peptides.The nmr spectra indicate a relatively flexible structure with the presence of an N-terminal turn. Standard distance geometry calculations failed to produce structures in accord with the experimental observations; the resulting structures are indeed too rigid and conformationally restricted for the nmr data. The results of ensemble calculations reveal conformational changes occurring rapidly on the nmr time scale and allow for the establishment of a series of disordered conformations, prevalently extended with a partially populated turn in residues 2-5, which when considered together, as an average, fulfill the experimental restraints. The structural characterization of (Thr6)-bradykinin supports the hypothesis of the significant role of the residue at position 6 on both conformation as well as biological activities and suggests a N-terminal turn as a possible bioactive conformation. © 1997 John Wiley & Sons, Inc. Biopoly 40: 561-569, 1996
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  • 108
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    The effect of N-methylation on helical peptides (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996), S. 609-616 
    Details
    ISSN: 0006-3525
    Keywords: helical peptides ; N-methyl amino acid ; Lifson-Roig statistics ; helix-coil transition ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In N-methyl amino acids, the hydrogen of the N-H group is replaced with a bulky methyl group. While this change is expected to destabilize helical structures, the amount of destabilization is not known. Here the N-methyl group is placed into several positions of the helical peptides, acetyl-WGG(EAAAR)4A-amide and acetyl-WGG(RAAAA)4R-amide, and the melting of the peptides followed using CD.When analyzed using a simple two-state model, the destabilization associated with the H to CH3 substitution at 0°C is between 0.3 to 1.7 kcal/mole and is position dependent. The melting data may also be analyzed using a modified form of the Lifson-Roig statistics that should more correctly model the helix-coil transition in this small peptide. This analysis fails, however, apparently because the destabilization energy is greater than the energy that can be attributed to a single residue in this model. © 1997 John Wiley & Sons, Inc. Biopoly 40: 609-616, 1996
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    Editorial (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996), S. 593-593 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360400602
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    Structure optimization of an artificial neural filter detecting membrane-spanning amino acid sequences (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 13-29 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An artificial neural network has been developed for the recognition and prediction of transmembrane regions in the amino acid sequences of human integral membrane proteins. It provides an additional prediction method besides the common hydrophobicity analysis by statistical means. Membrane/nonmembrane transition regions are predicted with 92% accuracy in both training and independent test data. The method used for the development of the neural filter is the algorithm of structure evolution. It subjects both the architecture and parameters of the system to a systematical optimization process and carries out local search in the respective structure and parameter spaces. The training technique of incomplete induction as part of the structure evolution provides for a comparatively general solution of the problem that is described by input-output relations only. Seven physicochemical side-chain properties were used to encode the amino acid sequences. It was found that geometric parameters like side-chain volume, bulkiness, or surface area are of minor importance. The properties polarity, refractivity, and hydrophobicity, however, turned out to support feature extraction. It is concluded that membrane transition regions in proteins are encoded in sequences as a characteristic feature based on the respective side-chain properties. The method of structure evolution is described in detail for this particular application and suggestions for further development of amino acid sequence filters are made. © 1996 John Wiley & Sons, Inc.
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  • 111
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    Heat capacity and normal modes of poly (L-valine) in relation to spectra of oligovalines (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 53-67 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(L-valine) (PLV) belongs to the class of polyamino acids having a bulky side chain. It preferably adopts the β-sheet conformation, although high molecular weight PLV may form an α-helix as well. In the present article we report a detailed study of the phonons and their dispersion for β-PLV and the spectra of oligovalines in relation to its polymeric form. The N-deuterated analogue of β-PLV has also been studied to check the correctness of assignments and force field. Density of states and heat capacity have been obtained. The heat capacity is in very good agreement with the experimental measurements of Roles et al. © 1996 John Wiley & Sons, Inc.
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  • 112
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    Conformational stability of simusan - an exocellular lipopolysaccharide Acenitobacter sp. (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 43-52 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By the heating of diluted solutions of simusan - an anionic exocellular lipopolysaccharide of Acenitobacter sp. - an endothermic, presumably, conformational transition occurs. Specific features of this transition are its high cooperativity and the reduction of the transition heat by the decrease of the temperature scanning rate. The temperature of the transition is a linear function of the logarithm of the concentration of NaCl or KCl. The conformational transition appears to be accompanied by an athermic transition that manifests itself in the additional change of the specific heat. Divalent metal ions (Mg2+ and Ca2+) increase the temperature and the enthalpy of the transition to a greater extent than monovalent ions do. The cooperativity of the transition in the presence of divalent metal ions is higher than in the presence of monovalent metal ions. The removal of hydrophobic groups leads to the decrease both of the temperature and the cooperativity of the conformational transition of simusan. © 1996 John Wiley & Sons, Inc.
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    Stabilization of an isolated helical capping box in solution by hydrophobic interactions: Evidence from the NMR study of bioactive peptides from the C-terminus of human C5a anaphylatoxin (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 31-41 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthetic analogues of the C-terminal portion of C5a were designed and found to be agonists of the C5a receptor [J. A. Ember et al. (1992) Journal of Immunology, Vol. 148, p. 3165]. Nuclear magnetic resonance experiments were carried out to determine the solution conformation of the most potent analogue, the peptide C5a 65-74 (Tyr65, Phe67) (Tyr65-Ser66-Phe67-Lys68-Asp69-Met70-Gln71-Leu72-Gly73-Arg74). Medium-range nuclear Overhauser effects (NOEs) were observed for residues 65-70 of this C5a peptide, suggesting that this region adopts a folded conformation in a significant population of the solution conformational ensemble. Quantitative analyses of 3JNH-aH coupling constants and sequential NOE cross peaks gave an estimated helical population of 65% in the region Ser66-Met70. Additional evidence supporting the presence of a helical turn includes reduced amide-proton temperature coefficients and lowered3JHN-aH coupling constants in the region of Phe67-Met70. Conformational behavior of this C5a analogue peptide was studied using molecular modeling incorporating observed NOEs as constraints. The side chains of Tyr65, Phe67, and Met70 consistently form a hydrophobic cluster in all the model structures. The side chains of residues Ser66 and Asp69 can form reciprocal hydrogen bonds with the backbone NH groups of these two residues, indicating that residues Ser66-Phe67-Lys68-Asp69 (or SFKD) form a helix-stablizing capping box [E. T. Harper and G. D. Rose (1993) Biochemistry, Vol. 32, p. 7605: H. X. Zhou et al. (1994) Proteins: Structure, Function and Genetics, Vol. 18. p. 1] even within the single turn of helical structure found in the analogue C5a peptide. A comparison of the nmr results obtained for the analogue peptide and the natural decapeptide C5a 65-74 (He65-Ser66-His67-Lys68-Asp69-Met70-Gln71-Leu72-Gly73-Arg74) indicated that incorporation of residues Tyr65 and Phe67 helps stabilize an isolated capping box involving residues Ser66-Asp69 in the C5a peptides through more extensive hydrophobic/aromatic interactions between residues Tyr65, Phe67, and Met70 in the analogue peptide C5a 65-74 (Tyr65, Phe67). These results constitute the first experimental demonstration of hydrophobic determinants in helical capping-box interactions, proposed recently by a statistical analysis of protein structures [J. W. Seale et al. (1994) Protein Science, Vol. 3. pp. 1741-1745]. The stabilized helical turn may also account for the greater potency of the analogue peptide C5a65-74(Tyr65, Phe67) in receptor-binding assays. © 1996 John Wiley & Sons, Inc.
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    Mechanical properties of tropomyosin and implications for muscle regulation (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 89-95 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tropomyosin is a protein that controls the interactions of actin and myosin as a part of the regulation of muscle contraction. The 420 Å long α-helical coiled-coil molecules form long filaments, both in muscle and in crystals. The x-ray diffraction data from tropomyosin crystals have indicated large scale motions of the filaments that can be related to the inherent mechanical properties of the molecule, and by extension, to the role of tropomyosin in the cooperative activation of the thin filaments of muscle. Diffuse scattering analysis has provided information about the amplitudes of the motions that has been used to calculate the intrinsic flexibility of the molecule. It can then be shown that each tropomyosin molecule by itself can only mediate interactions of the nearest-neighboring tropomyosin molecules along the filament. The repeating nature of the thin filament, however, allows the entire filament to activate cooperatively. © 1996 John Wiley & Sons, Inc.
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    New theoretical methodology for elucidating the solution structure of peptides from NMR data. II. free energy of dominant microstates of Leu-enkephalin and population-weighted average nuclear Overhauser effects intensities (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 69-88 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A small linear peptide in solution may populate several stable states (called here microstates) in thermodynamic equilibrium: elucidating its dynamic three dimensional structure by multidimensional nmr is complex since the experimentally measured nuclear Overhauser effect intensities (NOEs) represent averages over the individual contributions. We propose a new methodology based on statistical mechanical considerations for analyzing nmr data of such peptides. In a previous paper [called paper I, H. Meirovitch et al. (1995) Journal of Physical Chemistry. 99, 4847-4854] we have developed theoretical methods for determining the contribution to the partition function Z of the most stable microstates. i.e., those that pertain to a given energy range above the global energy minimum (GEM). This relatively small set of dominant microstates provides the main contribution to medium- and long-range NOE intensities. In this work the individual populations and NOEs of the dominant microstates are determined, and then weighted averages are calculated and compared with experiment. Our methodology is applied to the pentapeptide Leu-enkephalin H-Tyr-Gly-Gly-Phe-Leu-OH, described by the potential energy function ECEPP. Twenty one significantly different energy minimized structures are first identified within the range of 2 kcal/mol above the GEM by an extensive conformational search; this range has been found in paper l to contribute 0.6 of Z These structures then become “seeds” for Monte Carlo (MC) simulations designed to keep the molecule relatively close to its seed. Indeed, the MC samples (called MC microstates) illustrate what we define as intermediate chain flexibility: some dihedral angles remain in the vicinity of their seed value, while others visit the full range of [-180°, 180°]. The free energies of the MC microstates (which lead to the populations) are calculated by the local states method, which (unlike other techniques) can handle any chain flexibility. The NOE of MC microstate iis calculated as the average 〈l/r3〉2i, and an effective interatomic distance reffi is defined as reffi = 〈l/r3〉-⅓i, where r is the distance between two protons. Under the “initial rate approximation,” and neglecting angular modulations, the overall intensity I is the average over reff-6i, weighted by the populations of the MC microstates. This treatment is justified under the assumption that the rates at which conformations interconvert within, and among, microstates are faster and slower, respectively, than the rotational reorientation of the molecule.I-6 leads to the virtual theoretical distances, compared to the corresponding virtual experimental distances, which were obtained previously from a cryoprotective solution of Leu-enkephalin at 280 K. A reasonable fit is found between theory and experiment. Future research directions are outlined. © 1996 John Wiley & Sons, Inc.
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    Solution structure of dehydropeptides: A CD investigation (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 97-108 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A CD investigation of eleven dehydropeptides is reported. The compounds investigated include tri-, tetra-, hexa-, hepta-, and octapeptides and contain one, two, or three dehydro-phenylalanine (ΔPhe) residues. The peptides showed different CD profiles depending on chain length, position, and number of dehydro residues. The CD data very much complemented that provided by nmr studies, confirming the conformational preference for β-bend structures in small peptides (tripeptides), and 310-helical or α-helical structures in longer peptides. The secondary structures were stable in chloroform solution and were denaturated by addition of trifluoroacetic acid. Solvent titration experiments performed by measuring CD as a function of solvent composition provided evidence that the order →←2 disorder conformational changes occurred as cooperative transitions. © 1996 John Wiley & Sons, Inc.
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    Binding of tacrine and 6-chlorotacrine by acetylcholinesterase (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 109-117 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Multiconfiguration thermodynamic integration was used to determine the relative binding strength of tacrine and 6-chlorotacrine by Torpedo californica acetylcholinesterase. 6-Chlorotacrine appears to be bound stronger by 0.7 ± 0.4 kcal/mol than unsubstituted tacrine when the active site triad residue His-440 is deprotonated. This result is in excellent agreement with experimental inhibition data on electric eel acetylcholinesterase. Electrostatic Poisson-Boltzmann calculations confirm that order of binding strength, resulting in ΔG of binding of -2.9 and -3.3 kcal/mol for tacrine and chlorotacrine, respectively, and suggest inhibitor binding does not occur when His-440 is charged. Our results suggest that electron density redistribution upon tacrine chlorination is mainly responsible for the increased attraction potential between protonated inhibitor molecule and adjacent aromatic groups of Phe-330 and Trp-84. © 1996 John Wiley & Sons, Inc.
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    Masthead (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360380101
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    Direct analysis of solute self-association by sedimentation equilibrium (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 119-130 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An improved procedure is described for the characterization of solute self-association by sedimentation equilibrium. Whereas previous statistical-mechanical approaches to allowance for the effects of thermodynamic nonideality have entailed tedious iteration because of their specification of activity coefficients in terms of the equilibrium concentrations of all species, such reliance upon knowledge of the solution composition is avoided by the adaptation of an alternative statistical-mechanical formulation [T. L. Hill and Y. D. Chen (1973) Biopolymers, Vol. 12, pp. 1285-1312] in which thermodynamic nonideality is expressed in terms of total solute concentration. The development of an analysis in terms of a relationship with total solute concentration as the experimental variable allows this attribute of the Adams-Fujita approach to be retained without sacrifice of statistical-mechanical rigor. Its use is illustrated by application to Rayleigh interferometric records of sedimentation equilibrium distributions reflecting α-chymotrypsin dimerization and lysozyme self-association. © 1996 John Wiley & Sons, Inc.
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    Application of the small-angle x-ray scattering technique for the study of two-step equilibrium enzyme-substrate interactions (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 131-139 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The small-angle x-ray scattering (SAXS) technique is used for the investigation of two-stage equilibrium macromolecular interactions of the enzyme-substrate type in solution. Experimental procedures and methods of analyzing the data obtained from SAXS have been elaborated. The algorithm for the data analysis allows one to determine the stoichiometric, equilibrium, and structural parameters of the enzyme-substrate complexes obtained. The thermodynamic characteristics for the formation of complexes of double-stranded oligonucleotide with Eco dam methyltransferase (MTase) have been determined and demonstrate a high cooperativity of MTase binding when the ternary complex containing the dimeric enzyme is formed. The structural parameters (Rg, Rc, semiaxes) have been determined for free enzyme and polynucleotides and of enzyme-substrate complexes, indicating structural rearrangements of the enzyme in the interaction with substrates. © 1996 John Wiley & Sons, Inc.
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    Clathrate hydrates are poor models of biomolecule hydration (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 177-181 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Clathrate hydrates form the basis of a general model of biomolecule hydration. In clathrate hydrate crystal structures, the size of hydrogen-bonded water rings is highly constrained to five members. The clathrate hydrate model predicts that the size of water rings near biomolecule surfaces is similarly constrained to five members. This report describes a test of this model of biomolecule hydration. We have demonstrated that five-membered water rings are not a general feature of protein or nucleic acid hydration. The clathrate hydrate model appears to be inappropriate for biomolecules. © 1996 John Wiley & Sons, Inc.
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    Conformational analysis of β-methyl-para-nitrophenylalanine stereoisomers of cyclo[D-Pen2, D-Pen5]enkephalin by NMR spectroscopy and conformational energy calculations (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 141-156 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solution conformations of β-methyl-para-nitrophenylalanine4 analogues of the potent δ-opioid peptide cyclo[D-Pen2, D-Pen5]enkephalin (DPDPE) were studied by combined use of nmr and conformational energy calculations. Nuclear Overhauser effect connectivities and 3JHNCαH coupling constants measured for the (2S, 3S)-, (2S, 3R)-, and (2R, 3R)-stereoisomers of[β-Me-p-NO2Phe4]DPDPE in DMSO were compared with low energy conformers obtained by energy minimization in the Empirical Conformational Energy Program for Peptides #2 force field. The conformers that satisfied all available nmr data were selected as probable solution conformations of these peptides. Side-chain rotamer populations, established using homonuclear (3JHαHβ) and heteronuclear (3JHαCγ) coupling constants and 13C chemical shifts, show that the β-methyl substituent eliminates one of the three staggered rotamers of the torsion angle x1 for each stereoisomer of the β-Me-p-NO2Phe4. Similar solution conformations were suggested for the L-Phe4-containing (2S, 3S)- and (2S, 3R)-stereoisomers. Despite some local differences, solution conformations of L- and D-Phe4-containing analogues have a common shape of the peptide backbone and allow similar orientations of the main δ-opioid pharmacophores. This type of structure differs from several models of the solution conformations of DPDPE, and from the model of biologically active conformations of DPDPE suggested earlier. The latter model is allowed for the potent (2S, 3S)- and (2S, 3R)-stereoisomers of [β-Me-p-NO2Phe4] DPDPE, but it is forbidden for the less active (2R, 3R)- and (2R, 3S)-stereoisomers. It was concluded that the biologically active stereoisomers of [β-Me-p-No2Phe4] DPDPE in the δ-receptor-bound state may assume a conformation different from their favorable conformations in DMSO. © 1996 John Wiley & Sons, Inc.
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    Exploration of the conformational space of oxytocin and arginine-vasopressin using the electrostatically driven Monte Carlo and molecular dynamics methods (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 157-175 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational analysis of the neurohypophyseal hormones oxytocin (OT) and arginine-vasopressin (AVP) has been carried out using two different computational approaches and three force fields, namely by the Electrostatically Driven Monte Carlo (EDMC) method, with the Empirical Conformational Energy Program for Peptides (ECEPP/3) force field or with the ECEPP/3 force field plus a hydration-shell model, and by simulated-annealing molecular dynamics with the Consistent Valence Force Field (CVFF). The low-energy conformations obtained for both hormones were classified using the minimal-tree clustering algorithm and characterized according to the locations of β-turns in the cyclic moieties. Calculations with the CVFF force field located conformations with a β-turn at residues 3 and 4 as the lowest energy ones both for OT and for AVP. In the ECEPP/3 force field the lowest energy conformation of OT contained a β-turn at residues 2 and 3, conformations with this location of the turn being higher in energy for AVP. The later difference can be attributed to the difference in the size of the side chain in position 3 of the sequences: the bulkier phenylalanine residue of AVP in combination with the bulky Tyr2 residue hinders the formation of a turn at residues 2 and 3. Conformations of OT and AVP with a turn at residues 3,4 were in the best agreement with the x-ray structures of deaminooxytocin and pressinoic acid (the cyclic moiety of vasopressin), respectively, and with the nmr-derived distance constraints. Generally, the low-energy conformations obtained with the hydration-shell model were in a better agreement with the experimental data than the conformations calculated in vacuo. It was found, however, that the obtained low-energy conformations do not satisfy all of the nmr-derived distance constraints and the nuclear Overhauser effect pattern observed in nmr studies can be fully explained only by assuming a dynamic equilibrium between conformations with β-turns at residues 2.3, 3.4, and 4.5. The low-energy structures of OT with a β-turn at residues 2.3 have the disulfide ring conformations close to the model proposed recently for a potent bicyclic antagonist of OT [M.D. Shenderovich et al. (1994) Polish Journal of Chemistry, Vol. 25, pp. 921-927], although the native hormone differs from the bicyclic analogue by the conformation of the C-terminal tripeptide. This finding confirms the hypothesis of different receptor-bound conformations of agonists and antagonists of OT. © 1996 John Wiley & Sons, Inc.
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    Conformational study of angiotensin II (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 183-190 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational free energy calculations using an empirical potential ECEPP/3 (Empirical Conformational Energy Program for Peptides, Version 3) were carried out on angiotensin II (AII) of sequence Asp-Arg-Val-Tyr-Ile-His-Pro-Phe to find the stable conformations of the free state in the unhydrated and the hydrated states. A conformational analysis of the unhydrated state was carried out using the buildup procedure. The free energy calculation using the hydration shell model was also carried out to obtain the stable conformation of the hydrated state. The calculated stable conformations of AII in both states have a partially right-handed α-helical structure stabilized by short- and medium-range interactions. The similarity between the lowest free energy conformations of the unhydrated and hydrated states suggests that the hydration might not be important to stabilize the overall conformation of AII in a free state. The absence of any intramolecular interaction of the Tyr side chain suggests the possible interaction of this residue with the receptor. In this study, we found that the low free energy conformations contain both the parallel-plate and the perpendicular-plate geometries of the His and Phe rings, suggesting the coexistence of both conformations. © 1996 John Wiley & Sons, Inc.
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    Parallel-stranded duplex DNA containing dA · dU base pairs (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 209-220 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: DNA oligonucleotides with dA and dU residues can form duplexes with trans d(A · U) base pairing and the sugar-phosphate backbone in a parallel-stranded orientation, as previously established for oligonucleotides with d(A · T) base pairs. The properties of such parallel-stranded DNA (ps-DNA) 25-mer duplexes have been characterized by absorption (uv), CD, ir, and fluorescence spectroscopy, as well as by nuclease sensitivity. Comparisons were made with duplex molecules containing (a) dT in both strands, (b) dU in one strand and dT in the second, and (c) the same base combinations in reference antiparallel-stranded (aps) structures. Thermodynamic analysis revealed that total replacement of deoxythymine by deoxyuridine was accompanied by destabilization of the ps-helix (reduction in Tm by -13°C in 2 mM MgGl2, 10 mM Na-cacodylate). The U-containing ps-helix (U1 · U2) also melted 14°C lower than the corresponding aps-helix under the same ionic conditions; this difference was very close to that observed between ps and aps duplexes with d(A · T) base pairs. Force field minimized structures of the various ps and aps duplexes with either d(A · T) or d(A · U) base pairs ps/aps and dT/dU combinations are presented. The energy-minimized helical parameters did not differ significantly between the DNAs containing dT and dU. © 1996 John Wiley & Sons, Inc.
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    Conformational analysis of cyclic hexapeptides designed as constrained ligands for the SH2 domain of the p85 subunit of phosphatidylinositol-3-OH kinase (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 191-208 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structures of the cyclic hexapeptide cyclo(-Gly-Tyr-Val-Pro-Met-Leu-) (1) and its phosphotyrosyl (pTyr) derivative cyclo[-Gly-Tyr(PO3H2)-Val-Pro-Met-Leu-] (2), designed as constrained models of a sequence that interacts with the src homology 2 (SH2) region of the p85 subunit of phosphatidylinositol-3-OH kinase (PI-3 kinase), were studied in methanol/water solutions by 500 MHz nmr spectroscopy. Compound 1 was found to exist as a 2:1 mixture of isomers about the Val-Pro bond (trans and cis prolyl) between 292-330 K in 75% CD3O (D,H)/(D,H)2O solutions. A third species of undetermined structure (ca. 5%) was also observed. Compound 2, a model of phosphorylated peptide ligand that binds to the PI-3 kinase SH2 domain, exhibited similar conformational isomerism. When either compound was dissolved in pure solvent [i.e., 100% CD3O(H,D) or (H,D)2O] the ratio of cis to trans isomers was ca 1:1. A battery of one- and two-dimensional nmr experiments at different temperatures and solvent compositions allowed a complete assignment of both the cis and trans forms of 1 and indicated the trans compound to be the major isomer. The spectral properties of the phosphorylated derivative 2 paralleled those of 1, indicating like conformations for the two compounds. Analysis of rotating frame Overhauser spectroscopy data, coupling constants, amide proton temperature dependence, and amide proton exchange rates generated a set of constraints that were employed in energy minimization and molecular dynamics calculations using the CHARMM force field. The trans isomer exists with the tyrosine and C-terminal Tyr(+3) (Met) residues at opposite corners of the 18-membered ring separated by a distance of 16-18 Å, in contrast with the cis isomer where the side chains of these residues are much closer in space (7-14 Å). It was previously shown that the pTyr and the third amino acid C-terminal to this residue are the critical recognition elements for pTyr-peptide binding to the PI-3 kinase SH2 domain. Such cyclic structures may offer appropriate scaffolding for positioning important amino acid side chains of pTyr-containing peptides as a means of increasing their binding affinities to SH2 domains, and in turn provide a conceptual approach toward the design of SH2 domain directed peptidomimetics. © 1995 John Wiley & Sons, Inc.
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    Twist, writhe, and geometry of a DNA loop containing equally spaced coplanar bends (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 235-250 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation of a topologically closed DNA loop is important in many biological processes, including the regulation of transcription, recombination, and replication. Modeling DNA as an isotropic elastic rod, we use finite element analysis to show that the dependence of the twist (ΔTw) and the writhe (Wr) upon the linking number deficit (ΔLk) is strongly influenced by intrinsic bends. We determine how the geometry of a DNA loop changes as a function of the number of uniformly spaced coplanar 20° bends, oriented so as to open toward the center of the loop. We also calculate the geometry of DNA rods that are smoothly bent to the same extent. The response of both ΔTw and Wr of a bent DNA to changes in ΔLk falls into one of three categories, depending upon the number of bends. For a single bend of 20°, Wr increases monotonically with ΔLk and the change in ΔTw with distance is constant along the entire DNA axis. For two to ten 20° bends, Wr passes first through a local maximum, then through a local minimum, and finally increases monotonically as ΔLk increases. For eleven to eighteen 20° bends, Wr again varies monotonically with ΔLk. For all numbers of bends greater than two, the ΔTw per unit length depends upon the distribution of intrinsic bends, being constant between any two adjoining bends but varying with their position relative to the cut location. Accompanying these ΔLk-associated changes in Wr and ΔTw per unit length are characteristic changes in geometry that are specific for each category. The results of these calculations raise the possibility that intrinsic bends can serve as a control factor in the biological functions associated with loop formation in DNA. © 1996 John Wiley & Sons, Inc.
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    Development of a model for the δ-opioid receptor pharmacophore: 3. Comparison of the cyclic tetrapeptide Tyr-c[D-Cys-Phe-D-Pen] OH with other conformationally constrained δ-receptor selective ligands (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 221-234 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have previously proposed a model of the δ-opioid receptor bound conformation for the cyclic tetrapeptide, Tyr-c[D-Cys-Phe-D-Pen]OH (JOM-13) based on its conformational analysis and from conformation-affinity relationships observed for its analogues with modified first and third residues. To further verify the model, it is compared here with results of conformational and structure-activity studies for other known conformationally constrained δ-selective ligands: the cyclic pentapeptide agonist, Tyr-c[D-Pen-Gly-Phe-D-Phe]OH (DPDPE); the peptide antagonist, Tyr-Tic-Phe-PheOH (TIPP); the alkaloid agonist, 7-spiroindanyloxymorphone (SIOM); and the related alkaloid antagonist, oxymorphindole (OMI). A candidate δ-bound conformer is identified for DPDPE that provides spatial overlap of the functionally important N-terminal N+3 and C-terminal COO- groups and the aromatic rings of the Tyr and Phe residues in both cyclic peptides. It is shown that all δ-selective ligands considered have similar arrangements of their pharmacophoric elements, i.e., the tyramine moiety and a second aromatic ring (i.e., the rings of Phe3, Phe4, and Tic2 residues in JOM-13, DPDPE, and TIPP, respectively; the indole ring system in OMI, and the indanyl ring system in SIOM). The second aromatic rings, while occupying similar regions of space throughout the analogues considered, have different orientations in agonists and antagonists, but identical orientations in peptide and alkaloid ligands with the same agonistic or antagonistic properties. These results agree with the previously proposed binding model for JOM-13, are consistent with the view that δ-opioid agonists and antagonists share the same binding site, and support the hypothesis of a similar mode of binding for opioid peptides and alkaloids. © 1996 John Wiley & Sons, Inc.
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    Masthead (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.360380201
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    Concept and design of a new class of sequential oligopeptide carriers (SOC) for covalent attachment of multiple antigenic peptides (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 291-294 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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    A new efficient method for the synthesis of 1,4-benzodiazepine-2,5-dione diversomers (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 295-300 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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    Solid-state CD and peptide helical screw sense (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 301-304 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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    Dynamic simulations of the molecular conformations of wild type and mutant xanthan polymers suggest that conformational differences may contribute to observed differences in viscosity (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 251-272 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Xanthan gum is an exopolysaccharide secreted by the bacterium Xanthamonas campestris whose ability to make solutions viscous at low concentrations and over a pH and temperature range have generated much interest in both academic and industrial environments. Mutant Xanthamonas strains have been derived that produce xanthan gums with an altered or variant subunit chemical structure and different measured viscosities when compared with the wild type (wt) form of the polymer. Two variant gums were targeted as potentially interesting in this study, these being the nonacetylated tetramer (natct; and the acetylated tetramer (atet), which both lack a side-chain terminal mannose residue and in one case (natet) lacks an acetate group on an internal mannose residue. Solutions of these tetrameric gums possess viscosities higher (natet) and lower (atet) than the wt gum, and therefore we have attempted to determine whether these molecules possess unique conformational preferences when compared with the wt and with each other. In this manner we can initiate an understanding of how a polysaccharide's conformation contributes to its solution properties.The GEGOP software permits a sampling of the static and dynamic equilibrium states of carbohydrate molecules, and this software was employed to calculate equilibrium states of representative oligosaccharides with chemical structures representative of xanthan-like molecules. Energy minimization techniques revealed similar local minima for all three molecules. Some of these minima are comprised of elongate backbone conformations (A type) in which side chains fold onto backbone surfaces. Other minima with A backbones possessed side chains in less intimate backbone contact especially when calculations were performed with a low dielectric constant. This phenomenon was particularly pronounced in the wt molecule where an increased number of negatively charged side-chain residues experience charge repulsion resulting in reduced side-chain-backbone contact.Metropolis Monte Carlo (MMC) dynamic simulations performed with an elevated temperature factor (1000 K) allowed a better qualitative representation of conformational space than 300 K simulations. Employing a nonhierarchical cluster analysis method (population density profile: PDP) coupled with a classification scheme, it was possible to partition resulting MMC data sets into conformational families. This analysis revealed that in simulations performed with different dielectric constant values (10, 25, and ∞) all molecules possessed primarily A-type backbones. Less elongate, more open helical backbone forms (B, C, D, J, and Flat-a) did occur during the simulations but were populated to a lesser extent. In the natet molecule significantly open helical backbones existed (E, F, G, H, and I) that did not occur in the lower viscosity wt and atet molecules. PDP clustering methods and subsequent conformational classification applied to the first residue (mannose) of the side chain permitted a determination of side-chain orientation. Comparison of all three molecules indicated a larger population of side-chain conformational families in less direct backbone contact for the wt molecule than either of the variant molecules (natet/atet) suggesting that the side chains in the wt are more flexible. Thus, a major conformational difference between the high viscosity natet. In addition, the significant difference between the higher viscosity wt and the lower viscosity atet is the increase side-chain flexibility in the wt. We hypothesize that conformational differences of this kind could form a partial explanation of the observed differences in viscosity between these xanthan-like polymers. © 1996 John Wiley & Sons, Inc.
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    Reduced surface: An efficient way to compute molecular surfaces (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 305-320 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Because of their wide use in molecular modeling, methods to compute molecular surfaces have received a lot of interest in recent years. However, most of the proposed algorithms compute the analytical representation of only the solvent-accessible surface. There are a few programs that compute the analytical representation of the solvent-excluded surface, but they often have problems handling singular cases of self-intersecting surfaces and tend to fail on large molecules (more than 10,000 atoms). We describe here a program called MSMS, which is shown to be fast and reliable in computing molecular surfaces. It relies on the use of the reduced surface that is briefly defined here and from which the solvent-accessible and solvent-excluded surfaces are computed. The four algorithms composing MSMS are described and their complexity is analyzed. Special attention is given to the handling of self-intersecting parts of the solvent-excluded surface called singularities. The program has been compared with Connolly's program PQMS [M. L. Connolly (1993) Journal of Molecular Graphics, Vol. 11, pp. 139-141] on a set of 709 molecules taken from the Brookhaven Data Base. MSMS was able to compute topologically correct surfaces for each molecule in the set. Moreover, the actual time spent to compute surfaces is in agreement with the theoretical complexity of the program, which is shown to be O[n log(n)] for n atoms. On a Hewlett-Packard 9000/735 workstation, MSMS takes 0.73 s to produce a triangulated solvent-excluded surface for crambin (1crn, 46 residues, 327 atoms, 4772 triangles), 4.6 s for thermolysin (3tln, 316 residues, 2437 atoms, 26462 triangles), and 104.53 s for glutamine synthetase (2gls, 5676 residues, 43632 atoms, 476665 triangles). © 1996 John Wiley & Sons, Inc.
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    A vibrational spectroscopic study of the metastable form of associated polyinosinic acid (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 329-338 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have studied by Raman and ir spectroscopy the metastable complex formed by the self-association of polyinosinic acid in aqueous solution. The complex is easily prepared by quickly cooling to ca. 0°C a warm solution of the polyribonucleotide to which a small amount of rubidium salt has been added. Upon heating, this metastable form melts cooperatively near 13°C, well below the dissociation temperature of a stable four-stranded complex, which occurs at 47°C in the same conditions. The presence of several components in the stretching-mode region of the carbonyl groups in the vibrational spectra of the metastable complex suggests that it also has a parallel four-stranded structure. The difference in structure between the two forms is believed to be caused by the presence of fewer metal ions in the central channel of the metastable complex, in agreement with conclusions reached in previous investigations. The Raman spectra further show that the ribose units in the metastable form have a C3′-endo conformation, in contrast with the stable form, for which we have previously suggested a mixed C2′-endo/C3′-endo conformation. © 1996 John Wiley & Sons, Inc.
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    Chain length and oligonucleotide stability at high pressure (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 321-328 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of hydrostatic pressure on the helix-coil transition temperature (Tm) was measured for the DNA oligomers (dA)n(dT)n, where n = 11, 15, and 19, in 50 mM NaCl. The data were analyzed in light of previously published data for the polymer, poly(dA)·poly(dT) under the same conditions. As has been observed for DNA polymers, increasing the hydrostatic pressure led to an increase in the Tm of the oligomers; however, the effect of pressure diminished with decreasing chain length. The value of dTm/dP decreased linearly with the inverse of the chain length varying from 3.15 × 10-2°C MPa-1 for the polymer to 0.7 × 10-2°C MPa-1 for the 11-mer. The two-state or van't Hoff enthalpy (ΔHvH) of the helix-coil transition was obtained by analysis of the half-width of the thermal transition. As expected, ΔHvH decreases with decreasing chain length. In contrast to the behavior of the polymer, poly(dA)·poly(dT), and (dA)19(dT)19, the ΔHvH of the two shorter duplex oligonucleotides displayed a small pressure dependence dΔHvH/dP≃-0.4 kJ MPa-1 in both cases. The changes observed in the Tm and ΔHvH were not sufficient to explain the magnitude of the chain-length dependence of the pressure effect. To interpret the large chain-length dependence of dTm/dP, we propose that the terminal base pairs contribute a negative volume change to the helix-coil transition. Base pairs distant from the ends exhibit behavior characterized by the polymer where end effects are assumed to be negligible, i.e., a positive volume change for the helix-coil transition. The negative volume change of separating terminal bases may originate from the imperfect interactions these base pairs form with water due to the existence of several energetically equivalent conformations. This is reminiscent of one of the mechanisms proposed to be important in the pressure-induced dissociation of multimeric proteins into their constituent subunits. © 1996 John Wiley & Sons, Inc.
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    A flexible model for the cell wall polysaccharide of Streptococcus mitis J22 determined by three-dimensional 13C edited nuclear overhauser effect spectroscopy and 13C-1H long-range coupling constants combined with molecular modeling (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 339-354 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report on the conformation of a tetrasaccharide fragment in the repeating subunit of the cell wall polysaccharide of Streptococcus mitis J22, a receptor for the lectin of Actinomyces viscosus T14V in a bacterial coaggregation that is important in the ecological interactions of oral bacteria. Although there is considerable overlap of the 1H-nmr signals, some cross peaks can be extracted from conventional two-dimensional nuclear Overhauser effect spectroscopy (NOESY) data on the polysaccharide. These data cannot be fit to a single conformation of the tetrasaccharide fragment. Therefore we have prepared a polysaccharide sample fully enriched in 13C from which we have determined accurate NOESY cross-peak volumes in a three-dimensional heteronuclear-resolved spectrum that allows accurate determination of many more NOESY cross peaks than does conventional two-dimensional spectroscopy. We have also used the 13C enriched polysaccharide to measure accurate values of long-range 13C-1H coupling constants that can be correlated with glycosidic dihedral angles. Molecular modeling calculations on the polysaccharide fragment, including molecular dynamics simulations, identify multiple low-energy conformations. This result is to be contrasted with previous calculations on blood group oligosaccharides in our laboratory using similar methods that showed relatively rigid conformations with little flexibility of the glycosidic linkages. The present NOESY and 3JCH data can be reconciled with a model for the antigenic tetrasaccharide in which three distinct conformations are in fast exchange. We propose that some carbohydrate epitopes such as those of the blood group oligosaccharides are relatively rigid while others such as the tetrasaccharide fragment in these studies exhibit much greater flexibility. © 1996 John Wiley & Sons, Inc.
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    Imaging polysaccharides by atomic force microscopy (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 355-366 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Techniques have been developed for the routine reliable imaging of polysaccharides by atomic force microscopy (AFM). The polysaccharides are deposited from aqueous solution onto the surface of freshly cleaved mica, air dried, and then imaged under alcohols. The rationale behind the development of the methodology is described and data is presented for the bacterial polysaccharides xanthan, acetan, and the plant polysaccharides 1-carrageenan and pectin. Studies on uncoated polysaccharides have demonstrated the improved resolution achievable when compared to more traditional metal-coated samples or replicas. For acetan the present methodology has permitted imaging of the helical structure. Finally, in addition to data obtained on individual polysaccharides, AFM images have also been obtained of the network structures formed by κ-carrageenan and gellan gum. © 1996 John Wiley & Sons, Inc.
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    Masthead (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360400501
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    Computational study of packing a collagen-like molecule: Quasi-hexagonal vs “Smith” collagen microfibril model (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996), S. 595-607 
    Details
    ISSN: 0006-3525
    Keywords: equivalent packing ; triple helix ; energy minimization ; ECEPP/3 force field ; dihedral angles ; axial periodicity ; frustration ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The lateral packing of a collagen-like molecule, CH3CO-(Gly-L-Pro-L-Pro)4-NHCH3, has been examined by energy minimization with the ECEPP/3 force field. Two current packing models, the Smith collagen microfibril twisted equilateral pentagonal model and the quasi-hexagonal packing model, have been extensively investigated. In treating the Smith microfibril model, energy minimization was carried out on various conformations including those with the symmetry of equivalent packing, i.e., in which the triple helices were arranged equivalently with respect to each other. Both models are based on the experimental observation of the characteristic axial periodicity, D = 67 nm, of light and dark bands, indicating that, if any superstructure exists, it should consist of five triple helices. The quasi-hexagonal packing structure is found to be energetically more favorable than the Smith microfibril model by as much as 31.2 kcal/mol of five triple helices. This is because the quasi-hexagonal packing geometry provides more nonbonded interaction possibilities between triple helices than does the Smith microfibril geometry. Our results are consistent with recent x-ray studies with synthetic collagen-like molecules and rat tail tendon, in which the data were interpreted as being consistent with either a quasi-hexagonal or a square-triangular structure. © 1997 John Wiley & Sons, Inc. Biopoly 40: 595-607, 1996
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    Die Chemie der Feuerwerkskörper (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 12-22 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/ciuz.19780120103
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    Konstitution und Lichtabsorption organischer Farbstoffe (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 1-11 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/ciuz.19780120102
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    Vektorielle Biokatalyse (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 33-40 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/ciuz.19780120202
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    Masthead (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978) 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19780120301
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    mini-chiuz (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. A4 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19780120107
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    Atomorbitale (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 23-26 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 30 Ill.
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    URL: http://dx.doi.org/10.1002/ciuz.19780120104
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    Chronik (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 32-32 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19780120106
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    Das Portrait: Rudolf Criegee (1902-1975) (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 49-55 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Der feste Zustand - Eine Einführung in die Festkörperchemie anhand sieben ausgewählter Beispiele. Von W. J. Moore. Friedr. Vieweg & Sohn Verlagsges. mbH, Braunschweig 1977. VIII, 164 S., 76 Abb., brosch. DM 22,80 (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 64-64 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19780120208
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    Behandlung hochradioaktiver Abfälle (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 82-88 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/ciuz.19780120304
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    mini-chiuz (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. A32 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/ciuz.19780120307
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    Wie schmutzig ist der Rhein?? (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 111-122 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Rheinanliegerstaaten haben im gemeinsamen Bemühen um die Qualität des Rheinwassers schon 1963 die „Internationale Kommission zum Schutze des Rheins gegen Verunreinigung“ (IKSR) ins Leben gerufen. Die IKSR überwacht die Wasserqualität und gibt einen jährlichen Bericht mit Analysendaten heraus. Außerdem erarbeitet sie Vorschläge für Maßnahmen zum Schutze des Stroms. In Ergänzung der jeweiligen nationalen Gewässerschutzmaßnahmen haben die Rheinanliegerstaaten 1976 das Übereinkommen zum Schutze des Rheins gegen chemische Verunreinigung (Chemieabkommen) abgeschlossen. Das Chemieakbkommen, durch das die Ableitung bestimmter gefährlicher Stoffe aus den Stoffgruppen und -familien: Queck-silber- und Cadmiumverbindungen, organische Halogen-, Phosphor- und Zinnverbin-dungen, cancerogene Stoffe so weit wie möglich verhindert und aus weiteren Stoffgruppen und -familien, darunter den meisten Metallen, streng überwacht und eingeschränkt werden soll, hat einen langfristigen präventiven Charakter. Das Chloridabkommen soll dagegen sofort zu Maßnahmen führen. Zu diesen Abkommen der Rheinanliegerstaaten treten eine Reihe weiterer internationaler Abkommen und Vereinbarungen mit Auswirkungen auf den Rhein, verschiedene Richtlinien der Europäischen Gemeinschaft, ein geplantes Abkommen der Länder im Europarat, ein Abkommen zum Schutze der Nordsee und des Nordatlantiks gegen die Verschmutzung vom Lande aus.
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    „Senföle“ (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 182-188 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Tab.
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    Lorenz Crell und das erste chemische Periodicum 1778 (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 199-200 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19780120605
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    Chemie in 30 Jahren (1996)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 30 (1996), S. 39-44 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: „ChiuZ“ wird 30 Jahre alt! Runde Geburtstage sind nicht nur Grund zum Feiern; die Jubilare nehmen sie auch oft zum Anlaß, um einerseits Bilanz zu ziehen und um andererseits über Gegenwart und Zukunft nachzudenken. Wir haben nun unsere Kuratoren gebeten, einmal aus ihrer Sicht mögliche Entwicklungslinien aufzuzeigen und zu kommentieren, natürlich immer eingedenk der Warnung Niels Bohrs: „Prognosen sind schwierig, besonders wenn sie die Zukunft betreffen.“ Doch lesen Sie selbst!.
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    Corrigendum (1996)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 30 (1996), S. 52-52 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19960300111
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    Chiuz aktuell (1996)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 30 (1996), S. 54-54 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
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    URL: http://dx.doi.org/10.1002/ciuz.19960300113
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    Masthead (1996)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 30 (1996) 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
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    URL: http://dx.doi.org/10.1002/ciuz.19960300201
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    Dendrimere - von der Ästhetik zur Anwendung? (1996)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 30 (1996), S. 75-85 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/ciuz.19960300204
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    Wissenschaft Aktuell (1996)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 30 (1996), S. 103-105 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
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    URL: http://dx.doi.org/10.1002/ciuz.19960300207
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    Editorial (1996)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 30 (1996), S. 4-4 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Karl Dimroth: 18. 8. 1910 - 26. 11. 1995 (1996)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 30 (1996), S. 45-45 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Zum Artikel von „Chemie auf dem Internet“ von Johann Gasteiger und Wolf-D. Ihlenfeldt: (Chem. unserer Zeit 1995, 29, 249-259) erreichte uns noch folgende kritische Stellungnahme: (1996)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 30 (1996), S. 157-157 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Editorial (1996)
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    Chemie in unserer Zeit 30 (1996), S. 116-116 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
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    URL: http://dx.doi.org/10.1002/ciuz.19960300302
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    Neue Aspekte der nucleophilen Substitution an Arenen (1996)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 30 (1996), S. 134-140 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 17 Ill.
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    URL: http://dx.doi.org/10.1002/ciuz.19960300305
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    Wer war es? (1996)
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    Chemie in unserer Zeit 30 (1996), S. 158-158 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19960300311
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    Masthead (1996)
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    Chemie in unserer Zeit 30 (1996) 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Analyse von Aminosäuresequenzen mit künstlichen neuronalen Netzen (1996)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 30 (1996), S. 172-181 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 8 Ill.
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    Konzepte und Methoden des Umweltschutzes: das Beispiel Dioxine (1996)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 30 (1996), S. 182-191 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/ciuz.19960300404
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    Radiation-induced graft polymerization of vinyl monomers onto polyamide-6 (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 234 (1996), S. 1-12 
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    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die strahleninduzierte Pfropfcopolymerisation von 4-Vinylpyridin (VP) und eines binären Gemisches von VP mit Acrylnitril (AN) auf Polyamid-6 (PA6) wurde untersucht. Die optimalen Reaktionsbedingungen zur Erzielung maximaler Pfropfung wurden ermittelt. Die Pfropfcopolymeren wurden mittels IR-Spektroskopie und thermogravimetrischer Analyse charakterisiert. Die thermischen Eigenschaften der Fasern änderten sich durch das Pfropfen, das Färbeverhalten der Fasern bezüglich der Gesamtfarbstoffaufnahme jedoch kaum.
    Notes: Radiation-induced graft copolymerization of 4-vinyl pyridine (VP) and a binary mixture of VP and acrylonitrile (AN) onto polyamide-6 (PA6) fiber has been studied. Optimum reaction conditions leading to maximum percentage of grafting have been evaluated. The graft copolymers have been characterized by IR spectroscopy, thermogravimetric analysis and also by studying the dyeing behaviour of the grafted and ungrafted fiber. It has been observed that, although the thermal properties of fibers had changed upon grafting, the dyeing behaviour, with respect to the total dye uptake, did show only little improvement.
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    URL: http://dx.doi.org/10.1002/apmc.1996.052340101
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    Structural investigations on low-molecular-weight polyisobutenes (1996)
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    Angewandte Makromolekulare Chemie 234 (1996), S. 71-90 
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    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Mittels 1H- und 13C-NMR-Spektroskopie werden Strukturuntersuchungen an Polyisobutenen, die durch Selektivpolymerisation hergestellt wurden, und an Handelsprodukten durchgeführt. Es ist möglich, die Signale “normalen” und einigen ungewöhnlichen Doppelbindungsstrukturen zuzuordnen. Die Ergebnisse werden mit Literaturdaten verglichen.
    Notes: Structural investigations of low-molecular-weight polyisobutenes synthesized by selective polymerization and of commercial polyisobutenes were made by 1H- and 13C-NMR spectroscopy. It is possible to attribute the signals to “normal” and to some unusual olefinic structures. A comparison was made to literature data.
    Additional Material: 3 Ill.
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    Crosslinked polymers from resin acids (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 234 (1996), S. 91-102 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch Addition von Epichlorhydrin an Polyamide oder Poly(amidimid)e, die durch Polykondensation von Poly(alkylenpolyamid)en mit Diels-Alder-Verbindungen von Harzsäuren hergestellt wurden, konnten neuartige Polymere erhalten werden. Die Ausgangsverbindungen wurden aus Acrylsäure bzw. Maleinsäreanhydrid und Harzsäuren, die aus Kolophonium extrahiert wurden, synthetisiert. Die hergestellten Polymeren wurden mit den üblichen physikalischen und chemischen Methoden charakterisiert. Sie haben eine dreidimensionale Struktur, sind heißhärtbar und verfügen über eine relativ gute thermische Stabilität.
    Notes: New polymers were synthesized by addition of epichlorohydrin to the polyamides or poly(amideimide)s derived from the polycondensation of poly(alkylenepolyamide)s with some Diels-Alder adducts of resin acids. The adducts were prepared by the reaction between resin acids (extracted from rosin) and acrylic acid or maleic anhydride. The obtained polymers, which were investigated by usual physical and chemical methods, are three-dimensional, thermosetting and fairly thermostable.
    Additional Material: 3 Ill.
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    Modell zur beschreibung der viskoelastischen eigenschaften von synthetischen fasern (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 234 (1996), S. 159-175 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The evaluation of the viscoelastic response of synthetic fibres from stress-relaxation data over a wide range of time at different strain rates is very time-consuming. Therefore, mathematical models are used to describe the viscoelastic response. The characteristic of synthetic fibres is that already at very low deformation rates like an elongation 〈 1% a nonlinear viscoelasticity has to be considered.Based on the analytical representation of isothermal viscoelastic behaviour by Boltzmann a new model making an assertion to the nonlinear viscoelasticity is proposed. Applying this model, the calculated values of moduli and relaxation tensions of the fibres Nomex® and PEEK are in good agreement with the experimental values.
    Notes: Zur Beurteilung des viskoelastischen Verhaltens von Synthesefasern sind zeitaufwendige Relaxationsuntersuchungen erforderlich. Um zu schnelleren Aussagen zu gelangen, werden mathematische Modelle benötigt. Charakteristisch für Synthesefasern ist, daß bereits bei sehr kleinen Dehnungen 〈 1% kein lineares viskoelastisches Verhalten angenommen werden kann. Es wird ein auf der Grundlage der Boltzmann-Theorie erweitertes Modell vorgestellt, welches das nichtlineare viskoelastische Verhalten von Synthesefasern beschreibt. Unter Anwendung des hier vorgestellten Modells wird das Relaxationsverhalten der Synthesefasern Nomex® und PEEK beschrieben und ein Konzept zur Messung und Auswertung des Ergebnisses vorgestellt.
    Additional Material: 11 Ill.
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    Study on electrorheological properties of semiconducting polyaniline-based suspensions (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 235 (1996), S. 21-34 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Elektrorheologische (ER) Flüssigkeiten, bestehend aus einem Dispersionsmittel mit niedriger Dielektrizitätskonstante und mit Ammoniakwasser oder Natriumhydroxid bei verschiedenen Konzentrationen deprotonierten Polyanilin-Partikeln wurden hergestellt. Der Einfluß der Dielektrizitätskonstante, der Leitfähigkeit des Volumenanteils der Polyanilin-Partikel, der Art des Dispersionsmittels, der Zugabe eines Benetzungsmittels sowie der elektrischen Feldstärke und der Temperatur auf die elektrorheologischen Eigenschaften der ER-Flüssigkeiten wurde untersucht. Die Ergebnisse zeigten, daß eine feuchtigkeitsunempfindliche, hochaktive elektrorheologische Flüssigkeit aus chloriertem Paraffinöl und mit Ammoniakwasser bei bestimmten pH-Werten deprotonierten Polyanilin-Partikeln hergestellt werden kann. Das Produkt wies eine Streck-spannung von 〉 10 kPa und eine Stromdichte von 〈 40 μA cm-2 bei einer Stärke des elektrischen Feldes von 2.8 kV mm-1 auf.
    Notes: Electrorheological (ER) fluids composed of a dispersing medium with a low dielectric constant and polyaniline particles, deprotonated with ammonia or sodium hydroxide at different concentrations for 24 h were studied. The effects of dielectric constant, conductivity and volume fraction of the polyaniline particles, the kind of dispersing medium, addition of surfactant, as well as the electric field strength and temperature on the ER properties of the ER fluids were investigated. The results showed that a moisture-insensitive, highly ER-active fluid can be obtained from chlorinated paraffin oil and polyaniline particles deprotonated with ammonia water at certain pH values and exhibited a static yield stress 〉 10 kPa and current density 〈 40 μA cm-2 at 2.8 kV mm-1 DC electric field.
    Additional Material: 14 Ill.
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    Pultruded fiber-reinforced polyurethane-toughened phenolic resin, I. Reactivity and morphology (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 235 (1996), S. 35-45 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Ein Phenolharz-Polyurethan-Copolymeres wurde aus einem Phenolharz, einem geschützten Polyurethan und p-Toluolsulfonsäure hergestellt. Dieses Copolymere weist trotz großer Härte eine gute Verarbeitbarkeit (einschließlich Topfzeit und Reaktivität) auf. Die Synthese des Copolymeren wurde mit IR-Spektroskopie verfolgt. Es wurde gefunden, daß die Isocyanatgruppe des Polyurethans nach Abspaltung der Schutzgruppe mit der Hydroxygruppe des Phenolharzes reagierte. Glasfaserverstärkte Verbundwerkstoffe offenbarten bei SEM-Untersuchungen eine hervorragende Verbindung zwischen Faser und Matrix. Ein Überlappungspeak im DMA-Diagram wies auf Wechselwirkungen zwischen Phenolharz und Polyurethan hin, die die Härte des Phenolharzes verbessern.
    Notes: A phenolic resin/polyurethane copolymer was synthesized by reaction of a phenolic resin, a blocked-polyurethane and p-toluene sulfonic acid. The copolymer provides a good balance between the processability (including pot life, reactivity) and toughness. The reactions that proceeded during the synthesis of the copolymer was investigated by IR spectroscopy. It was found that blocked polyurethane reacted with the hydroxy group of the phenolic resin. Glass fiber-reinforced composites showed excellent bonding between fiber and matrix as revealed by SEM photographs. An overlap peak was found from the DMA diagram; it indicated that an interaction existed between phenolic resin and polyurethane and that improved the toughness of the phenolic resin.
    Additional Material: 7 Ill.
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    High-temperature and ageing properties of trans-polyoctenylene-filled natural rubber vulcanizates and their correlation with network changes (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 235 (1996), S. 81-93 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß eines vernetzbaren Verarbeitungshilfsmittels, trans-Polyoctenylen (TOR), auf die Spannungs-Dehnungs-Eigenschaften von Vulkanisaten aus gefülltem Naturkautschuk (NR) bei hohen Temperaturen und nach einem Alterungsprozeß wurde systematisch untersucht. Zum Einsatz kamen drei verschiedene Vernetzungssysteme, ein konventionelles (CV), ein semi-effizientes (SEV) sowie ein effizientes (EV). Die beste Retention des 200%-Moduls und der Zugfestigkeit von NR bei hohen Temperaturen sowie nach der Alterung zeigte sich mit TOR für das CV-System. TGA-Messungen ergaben eine durch TOR bedingte erhöhte Stabilität der Elastomer/Polymer-Blends sowohl unter Sauerstoff als auch unter Stickstoff. Eine verbesserte thermische Stabilität wurde ebenfalls anhand der erhöhten Onset-und Peak-Temperaturen bei der Bestimmung der Rescan-Enthalpien mit DSC beobachtet. FTIR-(ATR)-Spektren zeigen allerdings keine Wechselwirkungen zwischen NR und TOR. Aufgrund der DSC-Ergebnisse wurde die Verbesserung der Eigenschaften im CV-System begründet, und es wurde ein wahrscheinlicher Mechanismus für die Änderung der Netzwerk-Struktur vorgeschlagen.
    Notes: A systematic study of filled natural rubber (NR) vulcanizates has been carried out to investigate the effect of a crosslinkable processing aid, trans-polyoctenylene (TOR) on stress-strain properties at high temperature and after ageing. Three different crosslinking systems, i. e., conventional (CV), semi-efficient (SEV) and efficient (EV), are included in this study. Retention of 200% modulus and tensile strength (TS) at high temperature as well as after ageing has been found to be better with TOR in the CV system. TGA results of gum polymeric blends showed enhanced stability with addition of TOR in both oxygen and nitrogen atmosphere. Enhanced thermal stability is also exhibited by higher onset and peak temperature while determining the rescan enthalpy of the filled vulcanized sample by means of DSC. FTIR (ATR) spectra however show no polymeric interaction between NR and TOR. The improvement of properties in the CV system has been explained with the help of DSC results and a probable mechanism has been suggested on the changes of network structure.
    Additional Material: 5 Ill.
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    Surface functionalization of polymer networks. Sulfonation of the internal surface of macroporous styrene-divinylbenzene copolymersDedicated to Prof. Dr. Joachim Klein on the occasion of his 60th birthday (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 235 (1996), S. 131-148 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Oberflächenfunktionalisierung polymerer Netzwerke wurde anhand der Sulfonierung makroporöser Styrol-Divinylbenzol-Copolymerer (S-DVB) als Modellreaktion untersucht. Die Bedingungen für eine Oberflächensulfonierung wurden untersucht. Es wurde gefunden, daß die Sulfonierung mit Schwefelsäure in Gegenwart von Nitromethan eine geeignete Methode ist. Modelle und Vorstellungen über die Struktur der Netzwerke werden entwickelt, um Oberflächenkapazitäten abzuschätzen und um zu zeigen, daß oberflächensulfonierte Netzwerke erhalten wurden.
    Notes: Surface functionalization of porous polymer networks was investigated using the sulfonation of macroporous styrene-divinylbenzene (S-DVB) copolymers as model reaction. Reaction conditions for the surface sulfonation were studied. Sulfonation with sulfuric acid in the presence of nitromethane was found to be a suitable method. Models and ideas of network structure are developed in order to estimate surface capacities and to show that surface-sulfonated networks were obtained.
    Additional Material: 9 Ill.
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    Niederdruckumkehrosmose mit modifizierten polyacrylnitril-ultrafiltrationsmembranen (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 235 (1996), S. 161-174 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The chemical modification of polyacrylonitrile ultrafiltration (PAN-UF) membranes by hydroxylamine yields low-pressure reverse-osmosis (LP-RO) membranes containing amidoxime and hydroxamic acid groups besides nitrile groups. These membranes are positively charged at pH values of 4.0 to 6.5.The water permeability of the membranes decreases from 400 L h-1 m-2 to 15 L h-1 m-2 (p = 0.3 MPa) by this modification. A comprehensive characterization was carried out by retention curves, IR and NMR spectra, Hg porosimetry, measurement of membrane potentials and separation performance regarding different metal salts.Due to the Donnan exclusion these membranes have a retention of 88% at a filtrate flux of 8 L h-1 m-2(p = 0.3 MPa) regarding bivalent metal ions like Ca2+ and Mg2+ which cause the water hardness. Regarding heavy metal ions like Cu2+ and In3+ much higher filtrate fluxes from 90 to 100 L h-1 m-2 (p = 0.3 MPa) are possible.In water medium without any heavy metal ions the amidoxime and hydroxamic acid groups are hydrolysed to carboxylic acid groups which are able to reject multivalentanions. By this the water softening ability remains.
    Notes: Die chemische Modifizierung von Polyacrylnitril-Ultrafiltrations(PAN-UF)-Membranen mit Hydroxylamin führt zu Niederdruckumkehrosmose-Membranen, die neben verbleibenden Nitrilguppen sowohl Amidoxim- als auch Hydroxamsäuregruppen enthalten und bei einem pH von 4,0 bis 6,5 positiv geladen sind.Die Wasserdurchlässigkeit der Membranen sinkt durch diese Modifizierung von 400 L h-1 m-2 auf 15 L h-1 m-2 (p = 0,3 MPa). Eine umfassende Charakterisierung erfolgte anhand von Trennkurven, IR- und NMR-Spektren, der Hg-Porosimetrie, der Membranpotentialmessung und der Trennleistung für verschiedene Metallsalze. Infolge des Donnan-Ausschlusses haben diese Membranen für zweiwertige Metallionen, wie die Härtebildner des Wassers Ca2+ und Mg2+, eine Rückhaltung von 88% bei einem Filtratfluß von 8 L h-1 m-2 (p = 0.3 MPa). Für Schwermetallionen wie Cu2+ und In3+ sind bei annähernd gleicher Rükhaltung wesentlich höhere Durchflußraten von 90 bis 100 L h-1 m-2 (p = 0,3 MPa) möglich.Im wäßrigen, schwermetallionenfreien Medium unterliegen die Amidoxim- und Hydroxamsäuregruppen der Hydrolyse, und es entstehen an der Membranoberfläche Carboxylgruppen, durch die mehrwertige Anionen zurückgehalten werden. Ihr Vermögen zur Wasserenthärtung bleibt erhalten.
    Additional Material: 5 Ill.
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    Synthesis of ketonic resins from self-polymerization of acetone, 2Part 1 cf.1.. Action of bases on acetone and the synthesis of halogenated and diels-alder adducts (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 236 (1996), S. 21-33 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Aceton wurde unter der Einwirkung von NaOH, NaOEt und KOH in ethanolischer oder methanolischer Lösung und bei Molverhältnissen Aceton/Base zwischen 1,5 : 1 und 12 : 1 zu einem flüssigen Harz polymerisiert. Das Polymerisationsprodukt wurde mit einer maximalen Ausbeute von 60% bezogen auf das eingesetzte Aceton und in allen Fällen mit unterschiedlichen Mengen an Isophoron als Nebenprodukt erhalten. Die Polyen-Struktur des Ketonharzes wurde mittels Elektronen- und IR-Spektroskopie sowie durch Vergleich mit einem Isophoron-Harz als Modellsubstanz nachgewiesen. Es wird vermutet, daß die Struktur des Acetonharzes der eines Kondensationsprodukts von Aceton mit Isophoron oder von Isophoron mit sich selbst entspricht. Acetonharze, die mit Brönsted-Säuren, Lewis-Säuren und alkalischen Katalysatorsystemen hergestellt wurden, lassen sich leicht bis zu einem bestimmten Sättigungsgrad halogenieren. Mit Maleinsäureanhydrid, 4-Benzochinon oder Fumarsäure bilden die Acetonharze Diels-Alder-Addukte, die ein bis zwei Dienophilmoleküle pro Harzmolekül aufweisen.
    Notes: Acetone was polymerized under the action of NaOH, NaOEt or KOH in ethanolic or methanolic solutions at a molar ratio acetone/base ranging from 1.5 : 1 to 12:1 to give a liquid resin. The liquid resin was obtained with a maximum yield of 60% over initial acetone and was always accompanied by variable quantities of isophorone. The polyenic nature of the ketonic resin obtained was shown by infrared and electronic spectroscopy, as well as by using an isophorone resin as model compound. It is proposed that the structure of the acetone resin should be a condensation product of acetone/ isophorone and isophorone/isophorone. Acetone resins (PCA) obtained both with Brönsted acids (PCA-B), Lewis acids (PCA-L) and alkaline catalysts (PCA-A) can be easily halogenated up to certain degrees of saturation. All PCA resins form Diels-Alder adducts with maleic anhydride, p-benzoquinone and fumaric acid. The adducts can contain from 1 to 2 dienophile molecules per molecule of resin.
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    A novel process for the chlorination of polymers in solution (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 234 (1996), S. 119-132 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wird ein neuer und einheitlicher Prozeß für die Lösungschlorierung von PVC, PE und Naturkautschuk mit Initiierung durch γ-Strahlung oder radikalische Initiatoren (Azo-Verbindungen) beschrieben. Dichlormethan wird an Stelle der industriellen Lösungsmittel Tetrachlormethan oder -ethan verwendet. Die Reaktion wird in einem Rührautoklaven bei 70-100°C und 4-7 bar durchgeführt. Bei der gleichzeitig stattfindenden Chlorierung des Lösungsmittels entsteht als Hauptprodukt Trichlormethan und weniger als 1 Gew.-% Tetrachlormethan. Die Charakterisierung der chlorierten Polymeren durch DSC- und NMR-Messungen ergab keine Unterschiede zu konventiell hergestellten Proben.
    Notes: A new uniform process for the solution chlorination of PVC, PE, and natural rubber has been developed with initiation by γ-irradiation or radical initiators (azocompounds). The solvent used is dichloromethane instead of the industrially used tetrachloroethane or tetrachloromethane. The reaction is carried out in an autoclave with stirrer at temperatures between 70 and 100°C and pressures from 4 to 7 bar. As a result of the simultaneous chlorination of the solvent, trichloromethane is formed and only less than 1 wt.-% tetrachloromethane. Characterization of the chlorinated polymers by DSC and NMR measurements showed no differences to conventionally chlorinated products.
    Additional Material: 5 Ill.
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    New aspects of the synthesis of polymercaptals (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 234 (1996), S. 191-207 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die protonenkatalysierte Polykondensation von aromatischen Aldehyden und α,ω-Dithiolen führt zu Polymercaptalen. Die Reaktion kann in Substanz oder Lösung durchgeführt werden. Die Substanzpolykondensation wurde mit Hexafluorophosphorsäure (HPF6) katalysiert, welche photochemisch durch Bestrahlen der Proben nach Zusatz von Diaryliodoniumsalz erzeugt wurde. Die Polymeren werden in hohen Ausbeuten, aber mit relativ niedrigen Molekulargewichten von Mn 2300-5700 (Dampfdruckosmometrie, VPO) erhalten. Die Lösungspolykondensation in Dichlormethan mit p-Toluolsulfonsäure als Katalysator führt dagegen zu hochmolekularen Produkten mit Mn 9100-24000 (VPO). Die Polymeren wurden mit NMR, VPO, GPC und TGA charakterisiert. Außerdem wurden cyclische Nebenprodukte isoliert und analysiert. Unter bestimmten Reaktionsbedingungen konnten Polyrotaxanstrukturen erhalten werden.
    Notes: The proton-catalyzed polycondensation of aromatic aldehydes with aliphatic and aromatic α,ω-dithiols leads to polymercaptals. The reaction may be carried out in bulk or solution. The bulk polycondensation was catalyzed by hexafluorophosphorous acid (HPF6), formed photochemically by irradiation of the samples containing diaryliodonium salt. The polymers were obtained in high yields but with low molecular weights of Mn 2300-5700 determined by vapour pressure osmometry (VPO). High-molecular-weight products of Mn 9100-24000 (VPO) were obtained by solution polycondensation in dichloromethane catalyzed by p-toluenesulfonic acid. The polymers have been characterized by NMR, VPO, GPC and TGA. Cyclic side products have been isolated and identified. Polyrotaxane structures were found under special conditions.
    Additional Material: 10 Ill.
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    Synthesis and characterization of poly(vinyl alcohol)-β-cyclodextrin copolymer (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 235 (1996), S. 15-20 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch aufeinanderfolgende Umsetzung von β-Cyclodextrin (BCD) mit Toluylendiisocyanat und Polyvinylalkohol (PVA) wurde ein PVA-BCD-Copolymeres hergestellt. Die Copolymerbildung wurde mittels IR-Spektroskopie, Differentialthermoanalyse (DSC) und Gelpermeationschromatographie nachgewiesen. Rasterelektronenmikroskopaufnahmen zeigen morphologische Unterschiede zwischen PVA und dem Copolymeren. Das Copolymere ist in gebräuchlichen Lösungsmitteln nahezu unlöslich; die Gleichgewichtsquellung in Wasser beträUgt 50%, womit es sich als Membranmaterial anbietet.
    Notes: A poly(vinyl alcohol)-β-cyclodextrin (PVA-BCD) copolymer was prepared by successive reaction of BCD with toluylene diisocyanate and PVA. Copolymer formation was evidenced by infrared spectroscopy, differential scanning calorimetry and gel permeation chromatography. Scanning electron micrographs show morphological differences between PVA and the copolymer. The copolymer, being almost insoluble in common solvents with an equilibrium swelling in water of 50%, is a potential membrane material.
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    Adhesive properties of poly(propylene) modified in bulk (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 236 (1996), S. 35-41 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Isotaktisches Polypropylen (iPP) wurde in Masse durch Zusatz von niedermolekularen Verbindungen wie Maleinsäureanhydrid, Natriummoleat, Fettsäuren oder deren Natriumsalzen und Dibutylphthalat modifiziert. Es wurde festgestellt, daß die Abhängigkeit der mechanischen Adhäsionsarbeit des Systems modifiziertes iPP-Polyvinylacetat von der Konzentration der niedermolekularen Stoffe im iPP ein Maximum aufweist. Das Maximum entspricht dem höchsten Wert der mechanischen Adhäsionsarbeit des modifizierten iPP mit einer bestimmten Konzentration an niedermolekularem Zusatzstoff. Es wurde festgestellt, daß der höchste Wert der mechanischen Adhäsionsarbeit für iPP mit 5 Gew.-% Maleinsäureanhydrid oder Natriummaleat und 1 oder 1,2 Gew.-% Fettsäuren oder deren Salze gilt. Als wirksamster Modifikator erwies sich Natriumoleat, das die mechanische Adhäsionsarbeit um den Faktor 6,4 erhöhte.
    Notes: Isotactic poly(propylene) (iPP) was modified in bulk by addition of low-molecular compounds, e.g. maleic anhydride, sodium maleate, fatty acids or their sodium salts and dibutyl phthalate. It was found that the dependence of the mechanical work of adhesion in the system modified iPP-poly(vinyl acetate) on the concentration of the low-molecular compound in iPP exhibited a maximum. It was shown that the highest value of the mechanical work of adhesion was reached in iPP containing 5 wt.-% of maleic anhydride or sodium maleate and 1 or 1.2 wt.-% of fatty acids or their salts, respectively. It was found that sodium oleate is the most efficient modifier and its addition increased the mechanical work of adhesion by 6.4 times.
    Additional Material: 4 Ill.
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    Effect of structure on the thermal behaviour of ethynyl-terminated imide resins (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 236 (1996), S. 55-66 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Eine Reihe aromatischer Imide mit Phosphinoxid-Einheiten im Molekülgerüst und Ethinyl-Endgruppen wurde durch Reaktion vom 3-Ethinylanilin mit Tris(3-aminophenyl)-phosphinoxide oder Bis(3-aminophenyl)-methylphosphinoxide und Pyromellitsäuredianhydrid oder 3, 3′,4, 4′-Benzophenontetracarbonsäuredianhydrid oder 4, 4′-Hexafluorisopropylidenbis(phthalsäureanhydrid) hergestellt. Die Struktur der Substanzen wurde mittels IR- und NMR-Spektroskopie sowie Elementaranalyse charakterisiert. Das thermische Verhalten wurde mittels Differentialkalorimetrie und Thermogravimetrie untersucht. Die Ethinyl-Endgruppen ermöglichen eine Härtung bei hohen Temperaturen. Die Zersetzungstemperaturen unter Stickstoff der gehärteten Harze liegen bei über 500°C. Bei 800°C beträgt der Aschegehalt zwischen 52% und 63,5%.
    Notes: A series of ethynyl-terminated aromatic imide monomers containing phosphine oxide in the backbone were synthesized by the reaction of tris(3-aminophenyl) phosphine oxide (TAP) or bis(3-aminophenyl)methyl phosphine oxide (BAP) with pyromellitic dianhydride (PMDA) or 3, 3′,4, 4′-benzophenone tetracarboxylic acid dianhydride (BTDA) or 4, 4′-perfluoroisopropylidenebis(phthalic anhydride), and 3-ethynyl aniline. Structural characterization was done by infrared, nuclear magnetic resonance spectroscopy and elemental analysis. Thermal characterization was done by differential scanning calorimetry and thermogravimetric analysis. The decomposition temperatures of cured resins were above 500°C in nitrogen atmosphere. Char yield at 800°C ranged from 52-63.5%.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1996.052360105
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    Einfluß von haftvermittlern auf das feuchteverhalten naturfaserverstärkter kunststoffeHerrn Professor Dr. Dr. h. c. Dietrich Braun zum 65. Geburtstag gewidmet (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 236 (1996), S. 129-138 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The poor resistance of cellulose fibres to moisture absorption and the lack of good interfacial adhesion make these fibres less attractive for reinforced plastics. By an optimal predrying, it is possible to increase the mechanical properties of jute-epoxy composites by 20%. Using silance as a coupling agent, the interface and, therefore, the composite properties are improved and the influence of moisture decreases. With this surface treatment, the tensile strength becomes independent of the moisture content of the composite. For the Young's modulus and the Wöhler curves, the influence of moisture on this composite properties decreases also distinctly.
    Notes: Die Feuchtigkeit stellt bei der Verwendung von Naturfasern in faserverstärkten Kunststoffen neben der geringen Faser-Matrix-Haftung eines der wesentlichen Problemfelder dar. Durch eine optimale Trocknung vor der Verarbeitung lassen sich bei Jute-EP-Verbunden die mechanischen Kennwerte um bis zu ca. 20% steigern.Durch den Einsatz von Haftvermittlern auf Silanbasis läßt sich neben einer Verbesserung der Faser-Matrix-Grenzschicht mit daraus resultierender deutlicher Erhöhung der mechanischen Verbundkennwerte auch der Feuchteeinfluß auf diese deutlich minimieren. So konnte die statische Zugfestigkeit durch die Silanisierung der Faseroberflächen unabhängig vom Feuchtegehalt der Verbunde eingestellt werden. Der Feuchteeinfluß auf den Verbund-E-Modul sowie auf die Wöhlerkurve konnte durch diese Art der Faserbehandlung auch deutlich reduziert werden.
    Additional Material: 7 Ill.
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    ANNOUNCEMENTS (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 236 (1996), S. 177-177 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052360114
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    Stat-poly(Ethylene oxide-co-propylene oxide). Synthesis, NMR characterization and crystallinity studies. Correlation with monte carlo simulation (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 237 (1996), S. 55-77 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch anionische Polymerisation nach einem bereits beschriebenen neuartigen heterogen-katalysierten Prozeß wurden statistische Poly(ethylenoxid-co-propylen-oxid)-Copolymere mit niedrigen Molekulargewichten hergestellt. Die Copolymeren wurden mit 1H NMR-und 13C NMR-Spektroskopie charakterisiert, um zum einen die Verteilung der um eine Ethylenoxid-Gruppe gebildeten Triaden und zum anderen die durchschnittliche Länge der Poly(ethylenoxid)-Sequenzen zu bestimmen. DSC-Messungen ergaben niedrige Kristallisationsgrade. Die so erhaltenen Copolymeren wurden erfolgreich als polymere Feststoffelektrolyte eingesetzt und zeigen bei Raumtemperatur hohe Leitfähigkeitswerte. Die Ergebnisse stimmen gut mit den Resultaten einer unter Verwendung des für die radikalische Polymerisation entwickelten Copolymerisations-Terminal-Modells durchgeführten Monte Carlo-Simulation überein.
    Notes: Low-molecular-weight stat-poly(ethylene oxide-co-propylene oxide) polymers have been prepared anionically using a new heterogeneous catalytic process previously reported. They were fully characterized by 1H and 13C NMR spectroscopy in order to determine the distribution of the ethylene oxide (EO)-centered triads, as well as the average lengths of poly(ethylene oxide) (PEO) sequences. Low degrees of crystallization were determined by DSC. These copolymers have been successfully used for applications in the solid polymer electrolytes field and high levels of conductivity at room temperature have been measured. The results are in good agreement with those obtained from a Monte Carlo simulation method using the copolymerization terminal model developed for radical polymerization.
    Additional Material: 6 Ill.
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    Polymerization of acrylamide in inverse microemulsion in the presence of mixtures of oleophilic and hydrophilic surfactants (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 237 (1996), S. 113-122 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Herstellung von einphasigen inversen Mikroemulsionen aus Toluol/Natrium-bis(2-ethylhexyl)-sulfosuccinat(AOT)/Wasser/Acrylamid(AAm)/Natriumdodecylsulfat(SDS) wird beschrieben. Die Eigenschaften der Mikroemulsionen vor der Polymerisation (Makroviskosität in Abhängigkeit vom Volumenanteil Φaw der dispersen wäßrigen Phase (Wasser + Acrylamid + SDS) und vom SDS/Acrylamid-Gewichtsverhältnis) wurden untersucht. Bei 20°C werden drei Viskositätsmaxima beobachtet, die auch bei 50°C noch gefunden werden. Die Viskosität des ersten bzw. dritten Signals ist jedoch auf 5-8 mPa· s gesunken, während die des zweiten und stärksten Peaks noch 250 mPa· s beträgt. Die Dispersionspolymerisation von Acrylamid wurde mit Ammoniumperoxodisulfat (hydrophil) und Benzoylperoxid (lipophil) bei60 C initiiert. Die Polymerisationsgeschwindigkeit von Acrylamid sinkt bei einembestimmten [Toluol]l[AOT]-Molverhaltnis und AcrylamiWasser-Gewichtsverhaltnis bei Volumenanteilen der warigen Phase Qaw iiber 20% stetig. Das durch Viskositatsmessung ermittelte Molekulargewicht des Polyacrylamids nimmt bis zu einem Volumenanteil der waarigen Phase maw von 30% unabhangig von der Art des Initiators zu. Oberhalb eines Q,-Werts von 30% scheint sich das Molekulargewicht des Polyacrylamids mit Anzeichen eines flachen Minimums bei einem CP,-Wert von an nahernd 50% einzupendeln.
    Notes: The preparation of single-phase toluene/sodium bis(2-ethylhexyl)sulfosuccinate(AOT)/water/acrylamide/sodium dodecyl sulfate(SDS) inverse microemulsions is described and their properties prior to polymerization (macroviscosity as a function of volume fraction Φaw of the dispersed aqueous (water + acrylamide(AAm) + SDS) phase, and of SDS/AAm mass ratio) are studied. At 20°C three viscosity maxima are observed. At 50°C all three peaks remain, the viscosity of the first and third peak, respectively, is lowered to 5-8 mPa· s while the second, most prominent peak still marks the level of ca. 250 mPa· s. The polymerization of acrylamide in dispersion systems is initiated by water-soluble ammonium peroxodisulfate (APS) and oilsoluble dibenzoyl peroxide (DBP) at 60°C. The polymerization rate of acrylamide for a given [toluene]/[AOT] molar ratio and AAm/water mass ratio monotonically decreases for Φaw values greater than 20%. The polyacrylamide viscosity molecular mass increases up to a Φaw value of ca. 30%, irrespective of the nature of initiator. For Φaw values over 30% the viscosity molecular mass of polyacrylamide seems to level off with some sings of shallow minimum close to Φaw of 50%.
    Additional Material: 5 Ill.
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    Einfluß der temperatur auf die zähigkeit, die bruchflächenmorphologie und das molekulare relaxationsverhalten von polycarbonat (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 237 (1996), S. 191-208 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The dynamic toughness behaviour of polycarbonate was performed with the instrumented Charpy impact test. In dependence on the temperature, elastic and elastic-plastic material behaviour with predominantly instable crack growth and elastic-plastic material behaviour with greater parts of stable crack growth were observed. An analysis method which enables the assessment of temperature dependence in a wide range of temperature is available by the energy-determined fracture mechanical parameter, „J integral“. The J integral values show a stress-determined local maximum at -60°C and a global maximum at 60°C, which is related to a stress-in-duced shear flow process. The intersection point in an Arrhenius plot between the straight line of the p relaxation and the fracture frequency was found at a temperature of -60°C and at a frequency of 300 Hz. It follows that the toughness peak at -60°C was induced by the p relaxation. In the selected range of temperature, it was possible to determine the quantitative extension of different areas of the fracture faces using optical microscopy. These results were correlated to the mechanical material behaviour of polycarbonate.
    Notes: Das Zähigkeitsverhalten von Polycarbonat wird bei dynamischer Beanspruchung mittels instrumentierter Kerbschlagbiegeprüfung bestimmt. In Abhängigkeit von der Temperatur wird elastisches, elastisch-plastisches Werkstoffverhalten mit überwiegend instabilem Rißwachstum und elastisch-plastisches Werkstoffverhalten mit dominanten Anteilen an stabilem Rißwachstum beobachtet. Mit der energiebestimmten bruchmechanischen Kenngröße „J-Integral“ wird eine Auswertemethode zur Verfügung gestellt, die eine Bewertung der Temperaturabhängigkeit in einem weiten Temperaturbereich erlaubt. Die J-Integral-Werte zeigen ein kraftdeterminiertes lokales Maximum bei -60°C und ein globales Maximum bei 60°C, das mit einem spannungsinduzierten Scherfließprozeß in Beziehung steht. Der Schnittpunkt der Spur der ß-Relaxation mit der Bruchfrequenz im Arrhenius-Diagramm ergibt sich zu einer Temperatur von -60°C bei einer Frequenz von 300 Hz. Daraus ist zu ersehen, daß die Zähigkeitserhöhung bei -60°C durch die ß-Relaxation stimuliert wird. Im gewählten Temperaturbereich war es möglich, die quantitative Größe ausgewählter Bruchflächenphänomene mittels lichtmikroskopischer Untersuchungen zu ermitteln und in Beziehung zum Werkstoffverhalten zu setzen.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1996.052370111
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    Microstructure and electrical conductivity of complex cathodes based on new vanadium oxides and polyether blends (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 238 (1996), S. 31-39 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: In dieser Arbeit wurden durch die Untersuchung der Kristallisationskinetik unter isothermen und nichtisothermen Bedingungen die Auswirkungen verschiedener Vanadiumoxide auf die Feinstruktur von PEO und PEO/PPO-Mischungen untersucht. Die elektrischen Eigenschaften der Probekörper wurden durch komplexe Impedanzanalyse ermittelt. Die Versuchsergebnisse bestätigen die Annahme, daß die verwendeten Zusätze (Ruß und Vanadiumoxide) aufgrund der Wechselwirkungen zwischen den Polymeren und den Additiven mikrostrukturelle Veränderungen im PEO/PPO-Polymerverbund hervorrufen.
    Notes: This paper studies the effect produced by different vanadium oxides on the microstructure of PEO and PEO/PPO blends by means of the analysis of the crystallization kinetics under isothermal and nonisothermal conditions. The electrical properties of the samples were characterized by complex impedance analysis. Results suggest that the additives employed (considering both carbon black and vanadium oxides) promote changes in the microstructure of PEO/PPO polymer blends because of polymer-additive interactions. All samples tested show good conductivity properties.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1996.052380103
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    In-line-rheometrie durch direkte wandschubspannungsermittlung (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 238 (1996), S. 73-86 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Considering the fundamentals of the capillary rheometry with the known correction method according to Rabinowitsch and Bagley, the traditional method to determine the die inlet pressure and the wall shear stress value is described.For some materials this method can lead to an incorrect assessment of the flow properties since a linear pessure drop in the dies is assumed. Therefore, a new method for direct shear stress determination as well as the necessary measuring device are described. This is a die which can be integrated in-line and determines the reac-tion force of the flowing melt onto the die wall on the basis of a die section resting on piezo-force transducers.The measuring results show that when determining the flow properties of materials with a potential to form structures during the flow process, e. g. LCP, the in-line die determines the correct wall shear stresses. With the classical method of capillary rheometry, however, comparable results for such materials can only be obtained if additional assumptions concerning the pressure profile are made.
    Notes: Ausgehend von den Grundlagen zur Kapillarrheometrie mit den bekannten Korrekturverfahren nach Rabinowitsch und Bagley wird das traditionelle Verfahren zur Ermittlung des Düseneinlaufdrucks sowie des Wandschubspannungswerts dargestellt. Dieses Verfahren kann bei manchen Materialien zur fehlerhaften Bewertung des Fließverhaltens führen, da ein linearer Druckabfall in den Meßdüsen unterstellt wird. Daher wird eine neue Methode zur direkten Schubspannungsermittlung vorgestellt sowie die dazu notwendige Meßeinrichtung beschrieben. Es handelt sich dabei um eine in-line integrierbare Düse, die auf der Basis eines auf Piezokraftaufnehmern gelagerten Düsenabschnitts die Reaktionskraft der strömenden Schmelze auf die Düsenwandung ermittelt.Die Meßergebnisse zeigen, daß bei der Ermittlung der Fließeigenschaften von Materialien, die ein Potential zur Strukturbildung während des Fließvorganges aufweisen, wie z. B. flüssigkristalline Polyester (LCP), mit der In-line-Düse korrekte Wandschubspannungen erhalten werden. Mit der klassischen Methode der Kapillarrheometrie hingegen können bei solchen Materialien nur dann vergleichbare Ergebnisse gewonnen werden, wenn zusätzliche Annahmen über den Druckverlauf in der Meßdüse gemacht werden.
    Additional Material: 7 Ill.
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    New azomethine-urethanic compounds (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 238 (1996), S. 119-127 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch Umsetzung von 2,2′-[Methylenbis(nitrilomethylidyn)]diphenol mit Toluylen-2,4-diisocyanat und Phenylisocyanat wurden neue Azomethin-Urethanverbindungen hergestellt, nämlich ein Polymeres bzw. dessen Modellverbindung. Die Produkte wurden mittels Elementaranalyse, IR- und NMR-Spektroskopie sowie Thermogravimetrie, DSC und Viskosimetrie charakterisiert. Beim Erhitzen dieser Verbindungen finden Umlagerungen statt, wobei sowohl Additions- als auch Kondensationsreaktionen ablaufen können, die zur Bildung thermostabiler Produkte, wahrscheinlich mit Hexahydrotriazin-Strukturen, führen.
    Notes: New azomethine-urethanic compounds were synthesized, starting from 2,2′-[methylenebis(nitrilomethylidyne)]diphenol and phenylisocyanate for the model compound and tolylene-2,4-diisocyanate for the polymer. The products were characterized by elemental analysis, IR and NMR spectroscopy as well as thermogravimetry, DSC and viscosimetry. Through heating, these compounds suffer chemical modification, both addition and condensation reactions being possible. Thermogravimetric studies have evidenced the formation of thermostable products, possibly due to hexahydrotriazinic structures resulted from the thermal treatment.
    Additional Material: 4 Ill.
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    Surface treatment of an epoxy resin by CO2 laser irradiation (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 238 (1996), S. 177-189 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß von CO2-Laserstrahlung auf die Oberflächeneigenschaften eines Epoxid-Laminierharzes (wärmebeständig bis 120°C) für kohlefaserverstärkte Kunststoffe (CFK) wird untersucht. Infrarot- und XPS-Spektroskopie zeigen, daß die Hydroxygruppen des Harzes unter Bildung von Doppelbindungen eliminiert werden. In Kohlendioxidatmosphäre werden tiefer liegende Teile des Harzes modifiziert als bei der Behandlung in Luft. Eine Steigerung der Reproduzierbarkeit der Klebfestigkeit des verwendeten CFK auf Basis des untersuchten Harzes ist nur bei gleichzeitiger Verringerung der Klebfestigkeit selbst möglich. Beim Einsatz eines heißhärtenden Klebstoffes kann kein Einfluß der Laserbehandlung auf die Klebfestigkeit festgestellt werden.
    Notes: The influence of CO2 laser radiation on the surface properties of a lamination resin (temperature resistant up to 120°C) which is used for carbon fibre-reinforced plastics (CFRP) is examined. It is shown by XPS and infrared spectroscopy that the hydroxy groups of the resin are eliminated by the laser radiation. Using a carbon dioxide atmosphere, also deeper parts of the resin are influenced compared to the treatment in air. The reproducibility of the bond strength is higher for the laser-treated samples than for untreated samples if a room temperature-curing adhesive is used, but the bond strength itself is lower. Laser treatment shows no influence at all if a hot-curing adhesive is used.
    Additional Material: 5 Ill.
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    Synthesis of a new macromonomeric peroxyinitiator having poly(tetrahydrofuran)Systematic name: poly(oxytetramethylene). Units (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 239 (1996), S. 13-26 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Ein neuartiger makromonomerer Peroxyinitiator (MMPI) wurde aus Polytetrahydrofurandiol (p-THF-diol, Mw 1 000), Isophorondiisocyanat (IPDI), 2,5-Dimethylhexyl-2,5-dihydroperoxid und 2-Isocyanatoethylmethacrylat (IEM) hergestellt. Die Polymerisation von MMPI bei 80°C ergab vernetztes Polytetrahydrofuran (poly-THF) mit Quellungsverhältnissen in Trichlormethan (CHCl3) zwischen 1,4 und 4,2. Die mit MMPI initiierte Massepolymerisation von Styrol bei 80°C führte zu vernetzten Poly(THF-b-polystyrol)-Blockcopolymeren. Die Gesamtgeschwindigkeitskonstante k für Polymerausbeuten unter 15% wurde zu 1 · 10-4 (L mol-1)1/2 s-1 bestimmt. Die Quellungsverhältnisse der vernetzten Blockcopolymeren in CHCl3, lagen je nach MMPI-Konzentration und Polymerisationszeit zwischen 2,7 und 75, die Quellungsverhältnisse bei konstanter MMPI-Konzentration und zunehmender Polymerisationszeit zwischen 335 und 7,07. Die thermogravimetrische Analyse ergab, daß die vernetzten Blockcopolymeren noch unzersetzte Peroxy-Gruppen enthielten, die eine thermische Styrolpolymerisation initiieren und somit zu mmehrkomponentigen vernetzten Copolymeren führen können.
    Notes: A new macromonomeric peroxyinitiator (MMPI) was synthesized by the reaction of polytetrahydrofurandiol (p-THF-diol), Mw (1000), isophorone diisocyanate, 2,5-dimethylhexyl-2,5-dihydroperoxide and 2-isocyanatoethyl methacrylate. Homopolymerization of MMPI at 80°C gave crosslinked polytetrahydrofuran (poly-THF) with swelling ratios in CHCl3 varying between 1.4 and 4.2.Styrene polymerization initiated by MMPI at 80°C in bulk gave crosslinked poly-THF-b-polystyrene block copolymers. The overall rate constant, k, was found to be 1 · 10-4 (L mol-1)1/2 s-1 by keeping the polymer yield below 15%. Swelling ratios of the crosslinked block copolymers in CHCl3 were between 2.7 and 75 according to the concentration of MMPI and the polymerization time. In case the MMPI concentration was kept constant while the polymerization time was increased, swelling ratios were found between 3.55 and 7.07. Thermogravimetric analysis showed that the crosslinked block copolymers were still containing undecomposed peroxy groups, so they can thermally initiate styrene polymerization in order to obtain multicomponent cross-linked copolymers.
    Additional Material: 8 Ill.
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    Structural changes in poly(methyl methacrylate) during deep-etch X-ray synchrotron radiation lithography. Part I: Degradation of the molar massDedicated to Prof. Dr. Hansjörg Sinn on the occasion of his 65th birthday (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 239 (1996), S. 63-77 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: In der Röntgentiefenlithographie wird Polymethylmethacrylat (PMMA) gezielt mit Röntgensynchrotronstrahlung bestrahlt. Dadurch ändert sich die chemische Struktur des Polymeren, so daß es mit Hilfe eines selektiven Lösemittelgemisches vom restlichen unbestrahlten Polymeren abgetrennt werden kann. Ein wesentlicher Punkt der strahleninduzierten Strukturänderungen von PMMA ist die Molmassenabnahme, welche durch den Einsatz einer SEC-MALLS Kopplung zur Absolutbestimmung der Molmasse erstmals quantitativ bestimmt werden konnte. Zur Darstellung des experimentell ermittelten Verlaufs wurde eine kinetische Funktion abgeleitet, welche den Zusammenhang zwischen Dosis und Molmasse mit sehr guter Genauigkeit wiedergibt.
    Notes: Poly(methyl methacrylate) is a preferred material used in X-ray lithography. One effect observed after irradiation is a change of its chemical structure, combined with a decrease of the molar mass. This was analysed quantitatively using size exclusion chromatography combined with multi-angle laser-light scattering. Based on a kinetic model, an equation was derived which gives a satisfactory description of the dependence of the molar mass on the radiation dose.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052390107
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  • 196
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    Preparation and uranyl ion adsorptivity of macroreticular chelating resins containing a pair of neighboring amidoxime groups in a monomeric styrene unit (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 239 (1996), S. 121-132 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch Reaktion eines chlormethylierten Styrol/Divinylbenzol-Copolymeren mit Natriumcyanid wurde ein cyanmethyliertes Styrol/Divinylbenzol-Copolymeres hergestellt. Ein makroretikuläres Harz auf Polystyrolbasis, das zwei benachbarte Nitrilgruppen pro Monomereinheit enthielt, wurde durch die Reaktion des cyanmethylierten Copolymeren mit 3-Chlorpropionitril unter Phasentransferbedingungen hergestellt. Durch Reaktion mit Hydroxylamin wurde ein Chelatharz mit zwei Amidoximgruppen pro Monomereinheit erhalten. Das Chelatharz zeigte hohes Adsorptionsvermögen für Uranylionen. Es wurde festgestellt, daß das Harz ein wirksames Adsorbens für andere Schwermetallionen wie z. B. Hg2+ und Pb2+ ist.
    Notes: A cyanomethylated styrene-divinylbenzene copolymer was prepared by the reaction of a chloromethylated styrene-divinylbenzene copolymer with sodium cyanide. A polystyrene-based macroreticular resin containing a pair of neighboring nitrile groups in each monomeric styrene unit was obtained from the reaction of the cyanomethylated copolymer with 3-chloropropionitrile under phase transfer conditions. The resin was reacted with hydroxylamine to afford a chelating resin containing a pair of neighboring amidoxime groups in each monomeric styrene unit. The chelating resin showed high adsorption capacity for uranyl ions. It was found that the resin was an effective adsorbent for other heavy metal ions such as Hg2+ and Pb2+.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052390111
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  • 197
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    Graft polymerization of vinylidene chloride onto cellulose. A method to ascertain the grafting yield (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 239 (1996), S. 161-167 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Pfropfausbeute bei der mit Cer-Ionen initiierten Pfropfpolymerisation von Vinylidenchlorid (VDC) auf Cellulose erhöht sich mit zunehmender Reaktionsdauer und stabilisiert sich nach 6 h. Der Pfropfungsgrad nimmt von anfangs hohen Werten bei kurzen Reaktionszeiten rasch bis zu einem, konstanten Wert ab. Die Pfropfpolymerisation verläuft nach dem „from“-Mechanismus. Die Trennung von Homopolymerem und Pfropfpolymerem ist erforderlich, um die Pfropfausbeute und den Pfropfungsgrad zu ermitteln. Poly(vinylidenchlorid) (PVDC) ist aufgrund seiner großen Kristallinität und seines hohen Schmelzpunktes nur bei ausreichend hohen Temperaturen löslich. In Cyclohexanon löst sich PVDC bei 120°C unter teilweisem Abbau von Cellulose, der auf die Bildung von Chlorwasserstoff durch die Dehydrochlorierung des Polymeren zurückzuführen ist. Die Abtrennung des Homopolymeren vom Polymerisationsprodukt ohne Abbau der Cellulose gelingt mit einem Lösungsmittel-gemisch aus trockenem Cyclohexanon und 4-Methylpyridin.
    Notes: The graft polymerization of vinylidene chloride (VDC) onto cellulose initiated by ceric ions is reported. The grafting yield increases with reaction time and then levels off after 6 h. On the other hand, the grafting efficiency decreases rapidly from high initial values at short reaction times and then approaches to a constant value. The mechanism from of grafting is suggested for the present copolymerization. In order to determine both grafting yield and grafting efficiency, the separation of homopolymer and graft polymer is required. Sufficiently high temperatures are needed to dissolve poly(vinylidene chloride) (PVDC) because of its high crystallinity and melting point. Cyclohexanone dissolves the graft copolymer at 120°C bringing about some degradation of cellulose. Degradation is produced by hydrogen chloride formed throughout a slight dehydrochlorination of the synthetic polymer. A method inert for cellulose is suggested to retrieve the homopolymer from the polymerization crude by using a mixture of dry cyclohexanone and 4-methylpyridine as solvent.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052390114
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  • 198
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    Elastic properties of thermosets in glassy state (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 240 (1996), S. 31-38 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Young's modulus E and Poisson's ratio v of various thermosets, including 6 amine crosslinked epoxies, one anhydride crosslinked epoxy, one styrene crosslinked polyester and one styrene crosslinked vinylester, were determined from tensile tests in the 220-393 K temperature range and 1.6710-4-1.6710-2 s-1 strain rate range. The bulk (B) and shear (G) modulus were calculated from E and v. Some observations about structure-property relationships can be derived from these data and their comparison with corresponding ones relative to linear polymers. B appears to depend essentially of the cohesion and packing density and does not depend, practically, of temperature and strain rate. In contrast, G depends sharply of the local molecular mobility, this latter being affected by an antiplasticization mechanism. The Poisson's ratio seems to be systematically higher for thermosets than for linear polymers.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052400103
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  • 199
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    Synthesis and properties of epoxy-episulfide resins (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 240 (1996), S. 67-81 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Standard epoxy resins have good mechanical properties, but their prolonged low temperature curing time limits their potential use in clinical applications as well as in many industrial applications. A fast-curing epoxy-episulfide resin has been developed. The gel time of epoxy-episulfide made from EPONTrade mark of Shell Chemical Company. 828 ranges from 2 to 10 minutes by changing the ratio of the ingredients. The heat of reaction of this system is low, resulting in low cure shrinkage. Water absorption of the episulfide network is low. The epoxy-episulfide system cured with polyamide curing agent V-40 exhibits two transition temperatures, at about 85°C and 130°C, as shown in dynamic mechanical analysis data. In order to solve the long term stability problem of the above episulfides, and also the mixing problem, a lower viscosity resin, Eponex, was used to make Eponex-sulfide. Eponex-sulfide systems show promise in that they remain in a stable liquid form without epoxy. The other advantages appear to be retained.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052400106
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  • 200
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    Molecular design of reactive microgels (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 240 (1996), S. 99-112 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Structure and properties of microgels prepared by emulsion copolymerization depend on the composition and concentration of the monomers at the reaction sites, on the reactivity ratios and on the solubility of the comonomers in water. By separate and joint solubilization of 1,4-divinyl benzene and various comonomers of different solubility it could be shown, that the diffusion control of the copolymerization rate is favoured by crosslinking, by a high concentration of an oil-soluble initiator and of the emulsifier and by a low solubility of the comonomer in water.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052400109
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