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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 26 (1993), S. 1862-1868 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1879-1885 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present the design of a voltage pulse generator controlled by an IBM or compatible AT Personal Computer (PC) capable of synthesizing some of the voltage pulse wave forms commonly used in electrochemical studies. The included signals are: differential pulse voltametry, differential normal pulse voltametry, and differential pulse amperometry. Additionally, a triangular wave form and a constant-voltage signal, used in the pretreatment of carbon fiber microelectrodes for neurochemical analysis, are also available. Operating the generator imposes a minimum of restrictions on the specification of the duration, amplitude, and type of wave shapes. Low-cost PC-based design allows for compatibility, portability, and versatility. The operating ranges of the wave form parameters for the three voltametric signals are: initial voltage, −0.9–+0.9 V; step amplitude, 0.1–900 mV; period, 6 ms–60 s; measuring pulse amplitude, 0.1–900 mV; measuring pulse duration, 2 ms–20 s; prepulse duration, 2 ms–20 s. In the electrode pretreatment mode, the operating ranges are: amplitude, 0–±5 V; duration, unlimited; frequency, 15–240 Hz. The generator uses its own time base for the generation of all signals, thereby rendering it independent of processor clock speed or power-line frequency. The results of the experimental evaluation indicate that the system is accurate within ±10% of the expected values, taking into account the errors associated with the signal synthesis and the digitizing process. The maximum achievable scan rate is 500 V/s, and the highest frequency for the triangular wave form is 240 Hz. Therefore, the pulse generator could be used for fast cyclic voltametry (FCV). FCV and other wave forms could be added through software modules, without any hardware changes. We conclude that the PC-based electrochemistry pulse generator represents an economical and flexible alternative for electroanalytical applications. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 177 (1999), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The regulation of the pac gene encoding the penicillin G acylase of Escherichia coli W ATCC 11015 has been investigated by a molecular approach using lacZ as a reporter gene. This analysis revealed that a region of 170 bp located upstream of the pac structural gene contains the regulatory sequences that control its expression. The cAMP receptor protein is involved not only in the catabolite repression of penicillin G acylase production caused by glucose but also in the induction of pac gene expression by phenylacetic acid. Primer extension analyses have demonstrated that the transcription of the pac gene can be initiated from at least three different promoters. Although all these promoters are functional, their relative activity depends on the transcribed gene, the P1 and P3 promoters being more active in the presence of the pac gene, whereas the P2 promoter was stronger when the upstream region of the pac gene was fused to the lacZ reporter. A deletion of the region surrounding the −10 box of the P3 promoter produced a constitutive expression of the fused gene indicating that this sequence is required for phenylacetic acid induction and suggesting that the expression of the pac gene is regulated by a repression mechanism. This work reveals that the regulation of the pac gene is more complex than previously envisioned and provides new clues to investigate further this interesting regulatory system.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A biochemical approach to identify proteins with high affinity for choline-containing pneumococcal cell walls has allowed the localization, cloning and sequencing of a gene (lytC ) coding for a protein that degrades the cell walls of Streptococcus pneumoniae. The lytC gene is 1506 bp long and encodes a protein (LytC) of 501 amino acid residues with a predicted Mr of 58 682. LytC has a cleavable signal peptide, as demonstrated when the mature protein (about 55 kDa) was purified from S. pneumoniae. Biochemical analyses of the pure, mature protein proved that LytC is a lysozyme. Combined cell fractionation and Western blot analysis showed that the unprocessed, primary product of the lytC gene is located in the pneumococcal cytoplasm whereas the processed, active form of LytC is tightly bound to the cell envelope. In vivo experiments demonstrated that this lysozyme behaves as a pneumococcal autolytic enzyme at 30°C. The DNA region encoding the 253 C-terminal amino acid residues of LytC has been cloned and expressed in Escherichia coli. The truncated protein exhibits a low, but significant, choline-independent lysozyme activity, which suggests that this polypeptide adopts an active conformation. Self-alignment of the N-terminal part of the deduced amino acid sequence of LytC revealed the presence of 11 repeated motifs. These results strongly suggest that the lysozyme reported here has changed the general building plan characteristic of the choline-binding proteins of S. pneumoniae and its bacteriophages, i.e. the choline-binding domain and the catalytic domain are located, respectively, at the N-terminal and the C-terminal moieties of LytC. This work illustrates the natural versatility exhibited by the pneumococcal genes coding for choline-binding proteins to fuse separated catalytic and substrate-binding domains and create new and functional mature proteins.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 31 (1999), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Safracin is an antibiotic with anti-tumour activity produced by Pseudomonas fluorescens A2-2. The entire safracin synthetic gene cluster spanning 17.5 kb has been identified, cloned and sequenced. The safracin cluster comprises 10 open reading frames (ORFs) encoding proteins for three non-ribosomal peptide synthetases (NRPS), three safracin precursor biosynthetic enzymes, two safracin tailoring enzymes, a safracin resistance protein and a small hypothetical protein of unknown function. These genes are organized in two divergent operons of eight and two genes respectively. This pathway exhibits unusual features when compared with other NRPS systems. We have demonstrated by heterologous expression of the cluster that it is able to direct the synthesis of safracin in other strains. Cross-feeding experiments have confirmed that 3-hydroxy-5-methyl-O-methyltyrosine is the precursor of two amino acids of the molecule. Genetic analyses have allowed us to demonstrate that the bicistronic operon encodes the hydroxylation and N-methylation activities of the pathway. The cloning and expression of the safracin cluster has settled the basis for the in vivo and in vitro production of a wide variety of compounds, such as the promising ecteinascidins anti-cancer compounds.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Archiv der Mathematik 62 (1994), S. 116-125 
    ISSN: 1420-8938
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A 7.5 kb BclI-fragment of Streptococcs pneumoniae DNA has been cloned in Escherichia coli HB101 using pBR322 as a vector. The new plasmid (pGL30) of 12.0 kb expresses a protein that has been characterized by biochemical, immunological and genetic methods as the inactive form (E-form) of the pneumococcal N-acetyl-muramyl-l-alanyl amidase (EC 3.5.1.28). Our results demonstrate that the E-form is the primary product of the lyt gene of S. pneumoniae. The inactive E-form can be converted to the active C-form in vitro by incubation of the E-form enzyme with choline-containing pneumococcal cell walls at low temperature in a similar way to enzyme production in the homologous system. The production of this protein in E. coli HB101 was 500-fold higher than in the homologous host. E. coli CSR603 containing pGL30 and labeled with [35S]methionine synthesized a 35 kd protein. pGL30 can transform at high frequency an autolysin-defective mutant of S. pneumoniae to the lyt+ phenotype.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1617-4623
    Keywords: Autolysins ; Pneumococcal amidase ; Frame shift mutation ; Recombinant plasmids ; maxicells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A spontaneous mutation in the gene lyt encoding the pneumococcal autolysin has been characterized. This mutation, named lyt-32, which behaves as a high-efficiency marker in pneumococcal transformation, is a single base pair GC deletion causing the appearance of two consecutive termination codons in the amino terminal part of the sequence of the autolysin gene. The mutant lyt gene did not code for a polypeptide of relative molecular mass corresponding to the pneumococcal E form amidase in Escherichia coli maxicells. Pneumococcal cells containing the lyt-32 mutation (M32) were fully transformable, multiplied at a normal growth rate forming small chains and showed a tolerant response when treated with beta-lactam antibiotics. Strain M32 represents the first example of a mutant of Streptococcus pneumoniae completely lacking amidase as a consequence of an alteration in the structural gene coding for the pneumococcal autolysin.
    Type of Medium: Electronic Resource
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  • 10
    Publication Date: 2023-12-23
    Description: La Dirección General Marítima a través de sus dos Centros de Investigación localizados en Cartagena y Tumaco, desarrolla investigación científica marina con una tradición de más de dos décadas y aportes significativos al conocimiento descriptivo de las aguas oceánicas del Caribe y del Pacífico, a sus litorales y zonas costeras. Es tal vez esta materia en la que mayores resultados tangibles se han obtenido en los últimos años, no solamente al existir una tradición y experiencia ampliamente reconocidas nacional e internacionalmente, sino porque contamos con un recurso humano idóneo, calificado, tanto a bordo de las unidades oceanográficas como en tierra y con un extraordinario sentido de pertenencia. Considerando que las plataformas de investigación son esenciales para el fortalecimiento de la capacidad operativa e investigativa de la Armada Nacional y la Dirección General Marítima, se desarrolla desde 1999, el proyecto de reparaciones mayores de los buques oceanográficos ARC Malpelo y ARC Providencia, que debe terminar en el 2001. El presente anuario contiene los siguientes artículos: // Manejo integral de la zona costera aplicado al ordenamiento territorial del municipio de Tumaco. // Análisis de algunas características físico-químicas registradas en las aguas estuarinas de la Ensenada de Tumaco. // Variación espacio-temporal del zooplancton en la Ensenada de Tumaco, Pacífico colombiano. // Investigación oceanográfica conjunta en la Región Pacífica Sudeste y su proyección.
    Description: Published
    Description: Non Refereed
    Keywords: Zona costera ; Plancton ; Morfodinámica ; ASFA_2015::M::Marine biology ; ASFA_2015::C::Contamination ; ASFA_2015::C::Coastal zone
    Repository Name: AquaDocs
    Type: Book/Monograph/Conference Proceedings
    Format: 35pp.
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