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  • 1
    Electronic Resource
    Electronic Resource
    Homooligopeptides composed of hydrophobic amino acid residues interact in a specific manner by taking α-helix or β-structure toward lipid bilayers (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 391-398 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to investigate the role of each amino acid residue in determining the secondary structure of the transmembrane segment of membrane proteins in a lipid bilayer, we made a conformational analysis by CD for lipid-soluble homooligopeptides, benzyloxycarbonyl-(Z-) Aaan-OEt (n = 5-7), composed of Ala, Leu, Val, and Phe, in three media of trifluoroethanol, sodium dodecyl sulfaie micelle, and phospholipid liposomes. The lipid-peptide interaction was also studied through the observation of bilayer phase transition by differential scanning cahrimetry (DSC). The CD studies showed that peptides except for Phe oligomers are present as a mainly random structure in trifluoroethanol, as a mixture of α-helix, β-sheet, β-turn, and /or random in micelles above the critical micellization concentration and preferably as an extended structure of α-helical or β-structure in dipalmitoyl-D,L-α-phosphatidylcholine (DPPC) liposomes of gel state. That the β-structure content of Val oligomers in lipid bilayers is much higher than that in micelles and the oligopeptides of Leu (n = 7) and Ala (n = 6) can take an α-helical structure with one to two turns in lipid bilayers despite their short chain lengths indicates that lipid bilayers can stabilize the extended structure of both α-helical and β-structures of the peptides. The DSC study for bilayer phase transition of DPPC / peptide mixtures showed that the Leu oligomer virtually affects neither the temperature nor the enthalpy of the transition, while Val and Ala oligomers slightly reduce the transition enthalpy without altering the transition temperature. In contrast, the Phe oligomer affects the phase transition in much more complicated manner. The decreasing tendency of the transition enthalpy was more pronounced for the Ala oligomer as compared with the Leu and Val oligomers, which means that the isopropyl group of the side chain has a less perturbing effect on the lipid acyl chain than the methyl group of Ala. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360360312
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  • 2
    Electronic Resource
    Electronic Resource
    Characteristics of permeation and separation of aqueous alcoholic solutions through a poly[bis(2,2,2-trifluoroethoxy)phosphazene] membrane by evapomeation and pervaporation (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 234 (1996), S. 39-51 
    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 Permeations- und Trennungseigenschaften von Poly[bis(2,2,2-trifluoroethoxy)-phosphazene]-(PBTFP)-Membranen wurden durch Pervaporation und Evapomeation von wäßrigen Methanol-Lösungen und Ethanol-Lösungen untersucht. Bei der Pervaporation permeierten vorwiegend Methanol bei allen Mischungsverhältnissen und Ethanol bei Mischungen mit geringem Ethanolgehalt. Wasser permeierte bevorzugt bei Ethanol/Wasser-Mischungen mit höheren Ethanolkonzentrationen. Bei der Evapomeation durchdrang Wasser bei allen Dampfkonzentrationen der wanrigen Methanol-und Ethanol-Liisungen selektiv die Membran. Diese verschiedenen Permeationsselek-tivitäten hingen von den Mischungsverhaltnissen ab. Die Techniken der Membranen-permeation wurden bei unterschiedlichen Permeations- und Trennungsmechanismen diskutiert. Es wurde festgestellt, daß die Permeationsgeschwindigkeit vom Quellungsgrad der PBTFP-Membranen beeinflurßt wird und sich die Permeationsselektivitat von Wasserdampf aus alkoholischen Esungen mit zunehmendem Quellungsgrad der Membranen erhoht. Während der Einfluß steigender Permeationstemperaturen auf den Quellungsgrad der Membranen gering ist, nehmen Permeationsgeschwindigkeit und Permeationsselektivitat von Alkohol bei Pervaporation und Evapomeation mit steigenden Permeationstemperaturen starker zu. Die Ergebnisse werden hinsichtlich der Struktur der PBTFP-Membranen bei Pervaporation und Evapomeation diskutiert.
    Notes: The characteristics of permeation and separation for aqueous solutions of methanol and ethanol through a poly[bis(2,2,2-trifluoroethoxy)phosphazene] (PBTFP) membrane were studied by pervaporation and evapomeation. In pervaporation technique, methanol was preferentially permeated in all of the feed solution compositions and ethanol was permeated in lower ethanol concentrations of the feed solution. Water was predominantly permeated from the feed solutions with higher ethanol concentration. In evapomeation technique, water was selectively permeated in both all of the feed vapor compositions for aqueous methanol and ethanol solutions. These different permselectivities depended on the feed composition and the membrane permeation technique and could be discussed by a difference in the mechanisms of permeation and separation. It was found that the permeation rate was influenced remarkably by the degree of swelling of the PBTFP membrane and the permselectivity for water of aqueous alcoholic solutions was enhanced by an increasing degree of swelling of the membrane. When the degree of swelling of the membrane with rising permeation temperature was small, both the permeation rate and permselectivity for alcohol in pervaporation and evapomeation increased with the permeation temperature. The above results are discussed considering the PBTFP membrane structure in evapomeation and pervaporation.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052340105
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  • 3
    Electronic Resource
    Electronic Resource
    Maximum virginiamycin production by optimization of cultivation conditions in batch culture with autoregulator addition (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 437-444 
    Details
    ISSN: 0006-3592
    Keywords: Streptomyces virginiae ; autoregulator ; virginiae butanolide ; virginiamycin fermentation ; optimization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A strategy for optimization of non-growth-associated production in batch culture employing an empirical approach was developed through the study of virginiamycin production. The strategy is formulated with two aims: attaining a high cell concentration at the beginning of the production phase without decrease in production activity; and enhancing the production activity during the production phase. As a practical example, the goal of a maximum virginiamycin (M and S) production in the batch culture of Streptomyces virginiae was set. To attain a high cell concentration in the production phase of the batch culture, that is, to extend the growth phase for as long as possible, the optimum composition and concentration of the complex medium, especially the yeast extract (YE) concentration, were first investigated. Dissolved oxygen (DO) concentration control was also a parameter considered in maintaining the production activity during the production phase. In addition, to enhance the production activity, an optimum addition strategy of an autoregulator, virginiae butanolide-C (VB-C), was investigated. Combining these measures, the optimum cultivation conditions were found to be an initial YE concentration in the complex medium of 45 g/L, the shot addition of 300 μg/L of VB-C 11.5 h after the start of the batch culture, and a DO concentration maintained above 2 mg/L. The maximum concentrations of virginiamycin M and S were about ninefold those obtained under nonoptimum cultivation conditions. Nonoptimum cultivation conditions consisted of an initial YE concentration one sixth (7.5 g/L) that of the optimum cultivation conditions, and no VB-C addition. These conditions were used as representative of the standard cultivation of virginiamycin in this study. The strategy developed here will be applicable to the production of other antibiotics, especially to the cultivation of Streptomyces species, in which a hormonelike signal material (an autoregulator) plays an important role in antibiotic production. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Study on the thermal stability of a chiral stationary phase coated on capillaries for GC (1995)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 18 (1995), S. 630-634 
    Details
    ISSN: 0935-6304
    Keywords: GC ; Enantiomer separation ; Thermal stability ; Chiral stationary phase ; Metal capillary column ; Glass capillary column ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A chiral stationary phase prepared by bonding L-valine-t-butylamide to XE-60 has been coated on glass and metal capillaries. The performances of the chiral glass and metal columns were equivalent to those of commercial fused silica capillary columns. The thermal stability of the glass column was examined up to 280°C. It was found that no appreciable change in separation factor (α value) was observed up to 230°C. The α values gradually decreased between 240 and 260°C, and enantiomer separation was no longer achieved at 280°C. It was concluded that the allowable upper limit temperature of the chiral stationary phase is between 230 and 240°C in the isothermal mode, and ca 260°C in temperature-programmed mode.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240181004
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  • 5
    Electronic Resource
    Electronic Resource
    Cyclodextrin carbamates as novel chiral stationary phases for capillary gas chromatography (1995)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 18 (1995), S. 179-189 
    Details
    ISSN: 0935-6304
    Keywords: Enantioselective gas chromatography ; Chiral stationary phase ; Cyclodextrin carbamate ; Hydrogen bonding interaction ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The following carbamate derivatives of cyclodextrins (CDs) were prepared as novel chiral stationary phases for capillary gas chromatography: hexakis(2,6-di-O-pentyl)-α-cyclodextrin hexa(3-n-propyl, 3-isopropyl, and 3-phenylcarbamate), heptakis-(2,6-di-O-pentyl)-β-cyclodextrin hepta(3-n-propyl, 3-isopropyl, and 3-phenylcarbamate), and octakis(2,6-di-O-pentyl)-γ-cyclodextrin octa(3-n-propyl, 3-isopropyl, and 3-isopropyl, and 3-phenylcarbamate). Metal capillary columns coated with these stationary phases resolved many kinds of racemic mixture. In general, they were especially effective towards polar compounds such as free alcohols, amines, and epoxides. The types of sample which were effectively resolved depended on the cavity size of the CD: α-CD derivatives were specifically effective toward compounds having linear alkyl chains, and β-CD derivatives toward compounds with phenyl groups. The results indicate that chiral separation with the cyclodextrin carbamates depends on the formation of inclusion complexes and also on the hydrogen-bonding interactions between the samples and the CD carbamates.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240180309
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  • 6
    Electronic Resource
    Electronic Resource
    Nontoxic embolic liquids for treatment of arteriovenous malformations (1997)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 38 (1997), S. 79-86 
    Details
    ISSN: 0021-9304
    Keywords: embolic liquids ; interventional surgery ; arteriovenous malformations ; poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) ; noncytotoxic ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Interventional radiology is becoming one of the standard treatments of arteriovenous malformation (AVM). Cyanoacrylate derivatives and polymer solutions are widely used to occlude the AVM nidus by their injection through a catheter, but they are far from satisfactory embolic liquids. For instance, cyanoacrylate derivatives sometimes glue the catheter to the artery, resulting in serious complications; in addition, the organic solvents used to dissolve polymers cause damage to the surrounding brain tissue of the AVM. Therefore, we attempted to develop embolic liquids by dissolving poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) in Iopamiron with an addition of a small amount of ethyl alcohol. This new embolic liquid is not cytotoxic and is easily injected into the AVM through a thin, long catheter to effectively occlude the AVM. © 1997 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 38: 79-86, 1997
    Additional Material: 8 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Entrapment of islets into reversible disulfide hydrogels (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 115-123 
    Details
    ISSN: 0021-9304
    Keywords: entrapment ; islet ; reversible gel ; disulfide bond ; bioartificial pancreas ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Currently, there are three types of devices for a bioartificial pancreas; microencapsulation, an extravascular diffusion chamber, and an intravascular diffusion chamber. The purpose of the present study was to provide a new extracellular matrix hydrogel for the devices of extra- and intravascular diffusion chamber types. As the sol-gel transition of this hydrogel is reversible, refilling of islets in vivo will be possible without a severe traumatic procedure. The hydrogel was produced from a polyacrylamide derivative carrying thiol groups synthesized by radical copolymerization of acrylamide and N,N′-bis-acrylcystamine, followed by reduction of the disulfide bonds in the copolymer. This water-soluble copolymer was used to entrap hamster islets by re-formation of disulfide bonds on the copolymer to produce a hydrogel. The formed hydrogel was easily reliquefied by reduction of the disulfide crosslinks to thiols. Insulin release from the islet-entrapped hydrogel continued for more than 1 month when examined in vitro. A static glucose stimulation test for the entrapped islets exhibited an increased insulin release. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 115-123, 1998.
    Additional Material: 12 Ill.
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  • 8
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    Architectures of class-defining and specific domains of glutamyl-tRNA synthetase (1995)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1995-03-31
    Description: The crystal structure of a class I aminoacyl-transfer RNA synthetase, glutamyl-tRNA synthetase (GluRS) from Thermus thermophilus, was solved and refined at 2.5 A resolution. The amino-terminal half of GluRS shows a geometrical similarity with that of Escherichia coli glutaminyl-tRNA synthetase (GlnRS) of the same subclass in class I, comprising the class I-specific Rossmann fold domain and the intervening subclass-specific alpha/beta domain. These domains were found to have two GluRS-specific, secondary-structure insertions, which then participated in the specific recognition of the D and acceptor stems of tRNA(Glu) as indicated by mutagenesis analyses based on the docking properties of GluRS and tRNA. In striking contrast to the beta-barrel structure of the GlnRS carboxyl-terminal half, the GluRS carboxyl-terminal half displayed an all-alpha-helix architecture, an alpha-helix cage, and mutagenesis analyses indicated that it had a role in the anticodon recognition.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nureki, O -- Vassylyev, D G -- Katayanagi, K -- Shimizu, T -- Sekine, S -- Kigawa, T -- Miyazawa, T -- Yokoyama, S -- Morikawa, K -- New York, N.Y. -- Science. 1995 Mar 31;267(5206):1958-65.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biophysics and Biochemistry, School of Science, University of Tokyo, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7701318" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Amino Acyl-tRNA Synthetases/chemistry ; Anticodon ; Biological Evolution ; Computer Graphics ; Crystallography, X-Ray ; Escherichia coli/enzymology ; Glutamate-tRNA Ligase/*chemistry/metabolism ; Models, Molecular ; Molecular Sequence Data ; Mutagenesis, Site-Directed ; Protein Conformation ; Protein Folding ; Protein Structure, Secondary ; Protein Structure, Tertiary ; RNA, Transfer, Glu/chemistry/metabolism ; Sequence Alignment ; Thermus thermophilus/*enzymology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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