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  • 1
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 203-210 
    ISSN: 0887-624X
    Schlagwort(e): poly(4-vinylpyridine) ; 4,5-dicyanoimidazole ; betaine salt ; nucleophillic aromatic substitution ; polyelectrolyte ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A novel betaine internal salt (3) has been synthesized by the reaction of pyridine with 1-methyl-2-bromo-4,5-dicyanoimidazole (1). The reaction of pyridine with 1 serves as a model for the reaction of poly(4-vinylpyridine) with 1. The reaction of poly(4-vinylpyridine) with 1 gives betaine salt substituted polymers which were characterized by IR, NMR, UV-visible spectroscopy, and viscometry. The substituted polymers were compared to the model compound (3) and to unsubstituted poly(4-vinylpyridine) in order to determine polymer structure and the degree of substitution. One of the substituted polymers shows polyelectrolyte behavior. Thermal characterization of the substituted polymers shows two exothermic transitions at 260 and 340°C attributed to chemical reactions of the pendant groups.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 2
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The type II and type III collagen α-1 chain N-telopeptides are a nonadecamer with the sequence pEMAGGFDEKAGGAQLGVMQ-NH2 and a tetradecamer with the sequence pEYEAYDVKSGVAGG-NH2, respectively. Their conformations have been studied in CD3OH/H2O (60/40) solution by means of two-dimensional proton nmr spectroscopy. Based on double quantum filtered correlation spectroscopy, total correlation spectroscopy, rotating frame nuclear Overhauser enhancement (ROE) spectroscopy, and nuclear Over-hauser enhancement (NOE) spectroscopy experiments, all resonances were assigned and the conformational properties were analyzed in terms of vicinal NH-Hα coupling constants, sequential and medium-range NOEs (ROEs), and amide proton temperature coefficients. The NOE distance constraints as well as dihedral constraints based on the vicinal NH-Hα coupling constants were used as input parameters for restrained molecular mechanics, consisting of restrained molecular dynamics and restrained energy minimization calculations. The type II N-telopeptide's conformation is dominated by a fused βγ-turn between Phe6 and Ala10, stabilized by three hydrogen bonds and a salt bridge between the side-chain end groups of Glu8 and Lys9. The first 5 amino acids are extended with a much higher degree of conformational freedom. The 2 Gly residues following the turns were found to be highly flexible (hinge-like), leaving the spatial position of the second half of the molecule relative to the fused βγ-turn undefined. In the type III telopeptide, a series of sequential NH(i)-NH(i + 1) ROEs were observed between the amino acids Tyr2 and Ser9, indicating that a fraction of the conformational space is helical. However, the absence of medium-range ROEs and the lack of regularity of the effects associated with α-helices suggest the presence of a nascent rather than a complete helix. © 1993 John Wiley & Sons, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1295-1308 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The proteodermatan sulfate (PDS) of bovine skin is a low molecular weight proteoglycan with a molecular structure consisting of a protein chain and a sulfated polysaccharide chain covalently linked at the 4-serine of the protein. Static and dynamic laser light scattering methods have been used to determine the weight-average molecular weight, Mw, z-average radius of gyration, Rgz′, and z-average translational diffusion coefficient, Dt,z°, of bovine skin PDS. We have also characterized the two components of PDS, i.e., the protein core and the dermatan sulfate (DS) chain. (The latter contained an N-terminal-linked penta- or tetrapeptide.) Interpretation of the PDS data is complicated by the block copolymer nature of its structure. When appropriate corrections are made, our results indicate that Mw for PDS monomer is 62,000 when dissolved in 4M guanidine hydrochloride (GdnHCl), and increases to 610,000 in 0.15M NaCl. Mw for the core protein in 4M GdnHCl is 39,000, and this also increases substantially to 650,000 in 0.15M NaCl. In contrast, Mw for the DS chain is 24,000 in 0.15M NaCl, indicating that there is minimal self-association of DS in 0.15M NaCl. Thus we conclude that the self-association of PDS involves the protein core. Comparison of Rgz and Rh, the average hydrodynamic radius, suggests that trace amounts of aggregation persist for the PDS and its core protein even in 4M GdnHCl. This conclusion is supported by evaluation of the second moments of the dynamic light scattering correlation function. Comparisons of the observed Dt,z° for PDS with predicted values using hydrodynamic theory are consistent with a “lollipop” conformation for the molecule.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 449-458 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The solution conformation of tubulin-β(422-434)-NH2 (YQQYQDATADEQG-NH2) and its Nac-DATADEQG-NH2 fragment has been studied by two-dimensional 1H-nmr spectroscopy in CD3OH/H2O (90/10 v/v) at neutral and low pH. The 13 amino acid peptide is a segment of the C-terminal region of tubulin, and is directly involved in the selective binding site with microtubule-associated proteins MAP-2 and the τ protein. Based on correlated spectroscopy, total correlation spectroscopy, and rotating frame nuclear Over-hauser effect spectroscopy experiments, a complete assignment of all proton resonances was achieved, and the conformation of the backbone could be deduced from coupling constants, NH temperature coefficients, and nuclear Overhauser effects. The spectroscopic evidence indicates that the T8-Q12 section of both molecules forms one complete α-helical turn, stabilized by a NH(Q12)-C=O(T8) hydrogen bond. Furthermore, strong pH-dependent backfolding of the E11 side chain to its own NH proton was found. In addition, close proximity between the aromatic side chains of Y1, Y4, and the α-helical part, resulting in some substantial chemical shift changes when comparing the entire 13-mer with the octamer, could be explained in terms of a nonclassical kink in the DATA section. The conformational space is dominated by extended structures and the nonextended conformers are only a minor, yet spectroscopically clearly discernible entity. The presence of the α-helical region at the C-terminus of the 13-mer is important because binding studies of this peptide with MAP-2 indicate that the D10-E11-Q12-G13 fragment is critical for the binding interaction.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 741-756 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: cis-/trans-[1.1.1]-Trithia- and trans-[4.4.4]-Hexathia-tris-σ-homobenzenesStarting from the cis- and trans-benzene trioxides 2/7 the cis-/trans-[1.1.1]-Trithia-tris-σ-homobenzenes 1/6 and the trans-dioxathia-/oxadithia analogs 19/21 are synthesized by regioselective epoxide opening reactions with appropriate S-nucleophiles. Under the influence of heat and light cis-trisulfide 1 quickly looses sulfur and does not undergo [σ2 + σ2 + σ2]cycloreversion. Attempts to build up cis-[4.4.4]-tris-σ-homobenzenes from 2 by threefold six-membered ring anellation, in the special case of 1,2-benzenedithiol as 1,4-dinucleophil, led preferably to the trans-[4.4.4]-hexathia-tris-σ-homobenzene 44 (X-ray analysis) manifesting effective S-neighbouring group participation. cis-Trisulfide 1 is a poor tridentate ligand: only with Ni(ClO4)2 a 2:1 complex (presumably octahedral, 48) is formed.
    Notizen: Die cis-/trans-[1.1.1]-Trithia-tris-σ-homobenzole 1/6 und die trans-O,O,S-/O,S,S-Analogen 19/21 wurden ausgehend von den cis-/trans-Trioxiden 2/7 über regioselektive Epoxidöffnungsreaktionen mit geeigenten S-Nucleophilen hergestellt. cis-Trisulfid 1 verliert bei Wärme- bzw. Lichteinfluß rasch Schwefel bzw. geht nicht die [σ2 + σ2 + σ2]-Cycloreversion ein. Versuche, ausgehend vom cis-Trioxid 2 unter dreifacher Sechsringanellierung cis-[4.4.4]-Tris-σ-homobenzol-Gerüste aufzubauen, ergaben mit 1,2-Benzoldithiol als 1,4-Dinucleophil bevorzugt trans-[4.4.4]-Hexathia-tris-σ-homobenzol 44 (Röntgenstrukturanalyse)  -  als Ergebnis effizienter S-Nachbargruppenbeteiligung. cis-Trisulfid 1 ist ein mäßiger dreizähniger Ligand, nur mit Ni(ClO4)2 wurde ein (wahrscheinlich octaedrischer) 2:1-Komplex (48) gebildet.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 6
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The composition and sequence distribution of copolymers of maleic anhydride (MA) with p-methoxystyrene (p-MST) and p-chlorostyrene (p-CST) prepared in ethyl methyl ketone at 50 ± 0,1°C were analysed using 13C DEPT NMR techniques, in order to compare the applicability of composition and sequence distribution data to the study of the mechanism of copolymerisation using the terminal, penultimate and complex-participation models. In the case of the strongly alternating copolymerisation of p-MST with MA, the comparison of models on the basis of sequence distribution data was found to be better at separating each model in terms of its applicability, with the complex-participation model providing the best fit to the data. In the case of the less strongly alternating copolymerisation of p-CST with MA, neither method of comparison could clearly distinguish between the penultimate and complex-participation models.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 2001-2015 
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The composition and monomer unit sequence distribution of copolymers of p-methoxystyrene (p-MST) with citraconic anhydride (CA) prepared in methyl ethyl ketone (MEK) at 50,0 ± 0,1°C were determined over a range of comonomer feed mole fractions using 13C NMR spectroscopy. The monomer units in these copolymers were found to display an increasingly strong tendency to alternate as the mole fraction of CA in the feed increases. The existence of a 1:1 charge-transfer complex formed between p-MST and CA in the feed was confirmed via UV spectroscopy and the equilibrium constant for complex formation was determined. The terminal, penultimate and complex-participation models were tested for applicability to the mechanism of copolymerisation for this comonomer system. On the basis of copolymer composition data, the penultimate and complex-participation models were found to provide each an adequate description of the mechanism of copolymerisation in the comonomer system via non-linear least squares methods. The inadequacies of the terminal and penultimate models in describing the copolymers were exposed more explicitly through an analysis of their comonomer unit sequence distributions using reactivity ratio related test functions.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 8
    ISSN: 0269-3879
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: A high performance liquid chromatographic (HPLC) method with fluorescence detection after on-line reduction for the determination of 1-nitropyrene (NP), 1-nitrosopyrene (NSP), 1-aminopyrene (AP) and N-acetylaminopyrene (AAP) has been developed. The reduction efficiency of NP and NSP on a zinc column was found to be higher than that of an electrochemical reducer. Using a HPLC equipped with a zinc column (4.0 mm i.d. × 10 mm) and an imidazole/HCIO4 (pH 6.8):acetonitrile mobile phase, detection limits (S/N = 3) of 20-30 fmol for NP, NSP and AP and 350 fmol for AAP were obtained. NP, NSP and AP were determined in the incubation mixture of NP and Salmonella typhimurium, YG1021, by this method. Time course studies showed that a large ratio of NP was metabolized in the pre-incubation step of the Ames test.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 3229-3233 
    ISSN: 0887-624X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Perfluoroalkylene diacetylenes, HC≡C—(CF2)n—C≡CH, underwent thermal polymerization at 250-350°C to give glassy polymers stable to 450°C. Partial polymerization of the volatile monomers gave oligomers that are processable at atmospheric pressure. Polymers with similar thermal stability were obtained by transition-metal-catalyzed polymerization of the monomers at moderate temperatures.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 1413-1423 
    ISSN: 0887-624X
    Schlagwort(e): poly(imidazoleamide) ; cyanoimidazole ; heteroaramide ; imidazole amino acids ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The synthesis of a new class of heteroaromatic polyamides based on cyanoimidazoles are described. The monomer, 2-amino-4-cyanoimidazole-5-carboxylic acid (3) is prepared from a two-step hydrolysis of 2-amino-4,5-dicyanoimidazole (1). A model dimer prepared from condensation of 1 with 4-cyanoimidazole-5-carboxylic acid was structurally characterized by single crystal diffraction. The dimer, C10H8N8O3, crystallizes with Z = 2 and includes two waters of hydration in the P1 space group, a = 7.684 (2), b = 7.864 (3), c = 10.918 (5), α = 100.14 (3), β = 93.15 (3), γ = 103.79 (3). The model dimer is totally planar and shows trans geometry across the amide linkage. The monomer was polymerized by phosphorylation reaction conditions leading to a highly colored oligomeric polyamide. The polymer was characterized by IR spectroscopy, viscometry, GPC chromatography, and luminescence studies. The polymer luminesces strongly under 450 nm laser irradiation at low temperatures.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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