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  • 1
    Digitale Medien
    Digitale Medien
    Radical polymerization of poly(butyl acrylate) in the presence of poly(L-lactic acid), 1. Synthesis, characterization and properties of blends (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 246 (1997), S. 49-63 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Poly(L-milchsäure) ist ein biokompatibler, semikristalliner, thermoplastischer Polyester mit ungünstigen mechanischen Eigenschaften. Daher wurde in einem “reactive blending”-Prozeß ein Acrylkautschuk, n-Butylacrylat, mittels einer Suspensionspolymerisation in Wasser auf in einem organischen Lösungsmittel gelöste Poly(L-milchsäure) gepfropft. Die gebildeten Copolymeren konnten isoliert und durch NMR-Spektroskopie und DSC-Messungen charakterisiert werden. Die Untersuchung der mechanischen Eigenschaften ergab keine befriedigenden Ergebnisse, weil die Kautschukphase wahrscheinlich aus viskosen linearen Makromolekülen besteht und daher keine elastischen Eigenschaften besitzt. In weiteren Arbeiten soll der Syntheseweg so modifiziert werden, daß durch den Einbau von Diacrylaten eine zumindest partielle Vernetzung der Kautschukphase erreicht wird.
    Notizen: Poly(L-lactic acid) is a biocompatible polyester, semicrystalline, thermoplastic, with low versatility in mechanical properties. To overcome this problem, a reactive blending procedure was performed by grafting an acrylic rubber, n-butyl acrylate, via water suspension polymerization onto poly(L-lactic acid) dissolved in an organic solvent. It was possible to isolate the copolymeric phase formed from the two polymers and characterize it by using NMR and DSC techniques. Mechanical tests on blends gave no satisfactory response, probably because the rubbery phase is composed essentially of viscous linear macromolecules, not able to perform elastic properties. Work is in progress to modify the synthetic pathway to incorporate diacrylates in order to realize a rubbery phase at least partially cross-linked.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1997.052460104
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Elucidation of the structure of constrained bicyclopeptides in solution by two-dimensional cross-relaxation spectroscopy: Amatoxin analogues (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 2 (1996), S. 3-13 
    Details
    ISSN: 1075-2617
    Schlagwort(e): Structure of amatoxin analogues ; constrained bicyclopeptides ; NMR ; molecular dynamics ; Chemistry ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The evaluation of peptide structures in solution is made feasible by the combined use of two-dimensional NMR in the laboratory (NOESY) and rotating frames (ROESY), and by the use of molecular dynamics calculations. The present paper describes how both the NMR method and molecular dynamics calculations were applied to very rigid synthetic bicyclic peptides that are analogues of natural amatoxins. The NMR theory, which allows the estimate of interatomic distances between interacting nuclei, is briefly discussed. The experimental data were compared with those of known solid-state structures. Three amatoxin analogues have been examined. Of these, one is biologically active (S-deoxo γ[R] OH-Ile3-amaninamide) and its structure in the solid state has recently been worked out. The second and third analogues (S-deoxo-Ile3 -Ala5-amaninamide and S-deoxo-D-Ile3 -amaninamide, respectively) are inactive and their solid-state structures are unknown. The data presented confirm the authors' previous hypothesis that lack of biological activity of S-deoxo-Ile3-Ala5- amaninamide is due to the masking of the tryptophan ring by the methyl group of L-Ala and not to massive conformational changes of the analogue.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/psc.44
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    A conformational study in solution of pro-somatostatin fragments by NMR and computational methods (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 305-318 
    Details
    ISSN: 1075-2617
    Schlagwort(e): pro-somatostatin ; β-turn ; NMR ; computational methods ; conformational analysis ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The results of a conformational study by nuclear magnetic spectroscopy and computational methods on a series of point-mutated synthetic peptides, containing 14 amino acid residues and mimicking the region containing the Arg-Lys dibasic cleavage site of pro-somatostatin, have confirmed the possible role of a well defined secondary structure in the recognition phenomenon by processing enzymes.The importance of the residues located near the Arg-Lys dibasic site in the C-terminal region of the pro-hormone for the cleavage of the precursor into somatostatin-14 has been confirmed. The present structural analysis indicates the occurrence of two β-turns in the 4-7 and 11-14 regions, flanking the cleavage site, for all the peptides recognized as substrates by the processing enzyme.Interestingly, in the point-mutated analogue not processed by the enzyme and containing the replacement of proline by alanine in position 5 the first β-turn is displaced by one residue and involves the Ala5-Arg8 segment. This observation may explain the lack of recognition by the maturation enzyme. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Conformational studies on synthetic peptides reproducing the dibasic processing site of pro-ocytocin-neurophysin (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 1 (1995), S. 251-265 
    Details
    ISSN: 1075-2617
    Schlagwort(e): Hormone biosynthesis ; ocytocin ; prohormone ; proteolytic processing ; β-turn ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthetic peptides reproducing the proteolytic processing site of pro-ocytocin were studied by different spectroscopic techniques, including circular dichroism, Fourier tranform infrared absorption, and mono and bidimensional nuclear magnetic resonance, in order to ascertain the possible role of three-dimensional structure in the recognition process by maturation enzymes. Experimental results were compared with energy minimization calculations and suggest that: (i) the region situated on the N-terminus of the Lys-Arg doublet may form a β-turn; (ii) the sequential organization of the residues participating in the β-turn determines the privileged relative orientation of the basic amino acid sidechains and the subtype of turn; and (iii) the peptide segment situated on the C-terminal side of the dibasic doublet may assume a helix arrangement. These findings, in spite of the limitations connected to the flexibility of linear peptides, seem to substantiate the hypothesis that structural motifs around the cleavage site could be important for recognition and processing. However, a straightforward correlation between details of the secondary structure and the in vitro reactivity toward a putative convertase is not yet possible.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/psc.310010406
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  • 5
    Digitale Medien
    Digitale Medien
    Synthesis, Characterization and Conformational Analysis of gp120-derived Synthetic Peptides That Specifically Enhance HIV-1 Infectivity (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 3 (1997), S. 15-30 
    Details
    ISSN: 1075-2617
    Schlagwort(e): gp120/CD4 interactions ; HIV-1 PND ; conformation by CD and NMR ; solid-phase peptide synthesis ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A series of peptides patterned on the principal neutralizing domain of the HIV-1 envelope glycoprotein gp120 have been synthesized by solid-phase techniques. Interestingly, in vitro experiments have shown that some of these peptides specifically interact with CD4 and, in particular, that the peptide corresponding to the sequence 307-330 of the HIV-1 MN isolate was able to enhance infection in a dose- specific and not a strain-restricted way. To bypass problems observed in preliminary runs, several peptides were synthesized by both Fmoc and Boc chemistry. Comparison of the two strategies has allowed the set up of convenient protocols for the preparation of the target peptides in good yield, and with the high-purity grade needed for biological and physicochemical studies. Since the biological effects were present in the carboxyl-free C-terminal linear peptide but not in the amidated C-terminal analogue, preliminary conformational studies by circular dichroism and nuclear magnetic resonance techniques were also performed in an attempt to correlate these effects with possible contributions of structured conformations as predicted by theoretical calculations. The possibility of a β-turn structure for the crucial Gly-Pro-Gly-Arg sequence has been confirmed by 2D NMR experiments. Ongoing studies suggest the exploitation of the activating properties of the MN-derived peptides to design a more sensitive and innovative serological test based on the virus itself and not on anti-HIV antibodies, as is the case for the large majority of tests currently in use. © 1997 European Peptide Society and John Wiley & Sons, Ltd.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    NMR conformational studies on a synthetic peptide reproducing the [1-20] processing domain of the pro-ocytocin-neurophysin precursor (1996)
    New York : Wiley-Blackwell
    Biopolymers 39 (1996), S. 837-848 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The combined use of several nuclear magnetic resonance and restrained molecular dynamics techniques allowed the formulation of a molecular model for the preferred solution conformation of a synthetic peptide reproducing the [1-20] processing domain of the pro-ocytocin-neurophysin precursor. In the model, the conformation of the 20-membered tocin ring, with the two Cys1 and Cys6 residues bridged by a disulphide bond, is very close to that observed for isolated ocytocin in the solid state; in addition, a type II β-turn is postulated for the 7-10 segment of the acyclic tail containing the Lys11-Arg12 processing site, and connecting ocytocin to the neurophysin domain, while the C-terminal 13-20 segment of the molecule is believed to assume a helical structure. This particular structural organization could be important in participating as the favorable conformation for optimal substrate-enzyme active site recognition and processing by specific endoproteases. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    CD conformational studies on synthetic peptides encompassing the processing domain of the ocytocin/neurophysin precursor (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 461-476 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthetic peptides of different size, reproducing the proteolytic processing site of proocytocin, were studied by CD under several experimental conditions in order to ascertain the ability of different solvents to stabilize secondary structural motifs, such as α-helix tracts and β-turns. A combination of deconvolution methods and empirical calculations subtracting the contributions due to unordered structures from the spectra suggests that in solution (a) mainly two distinct families of ordered conformers containing structurally different β-turns are present, (b) the relative stability of the different conformers depends from the nature of the solvent, and (c) in the case of the larger peptides, a population containing an α-helical conformation is also present. From the biological point of view the presence of at least two families of ordered conformers could be in line with current theories assuming that the catalytic effect of the receptor microenvironment may be determinant in shifting the equilibrium toward the active conformation. © 1997 John Wiley & Sons, Inc. Biopoly 41: 461-479, 1997
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Preparation of poly(β-hydroxybutyrate)/poly(methyl methacrylate) blends by reactive blending and their characterisation (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1901-1907 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Poly(β-hydroxybutyrate) (PHB) is a biotechnologically produced polyester, highly crystalline, totally biodegradable with low versatility in mechanical properties. To overcome this problem we performed a reactive blending procedure with a glassy acrylic polymer, poly(methyl methacrylate) (PMMA), via water suspension polymerisation of the acrylic monomer precursor onto poly(β-hydroxybutyrate). It was possible to isolate the co-polymeric phase formed between the two polymers and to characterize it using NMR and differential scanning calorimetry (DSC) techniques. Fracture tests on the blends gave a satisfactory response: in fact the Critical Energy Release Factor (Gc) calculated by Linear Elastic Fracture Mechanism (LEFM) theory of a PHB/PMMA 70/30 wt/wt blend is less than two times larger than that of neat PHB.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 9
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    Toward a better understanding of the interaction between TGF-β family members and their ALK receptors (2012)
    Springer
    Details
    Publikationsdatum: 2012-02-22
    Print ISSN: 1610-2940
    Digitale ISSN: 0948-5023
    Thema: Chemie und Pharmazie
    Publiziert von Springer
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  • 10
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    Analysis of the interface variability in NMR structure ensembles of protein–protein complexes (2016)
    Elsevier
    Details
    Publikationsdatum: 2016-06-01
    Print ISSN: 1047-8477
    Digitale ISSN: 1095-8657
    Thema: Biologie
    Publiziert von Elsevier
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