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  • 1
    ISSN: 1432-1017
    Keywords: Key words Single cardiac Na+ channels ; Site-directed antipeptide antibody ; Proteolysis ; Protein reagents ; Calpain ; Stochastic mode switching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Failure of inactivation is the typical response of voltage-gated Na+ channels to the cytosolic presence of proteolytic enzymes, protein reagents such as N-bromoacetamide (NBA) or iodate, and antibodies directed against the linker between domains III and IV of the α-subunit. The present patch clamp experiments with cardiac Na+ channels aimed to test the hypothesis that these interventions may provoke the occurrence of non-inactivating Na+ channels with distinct kinetic properties. A site-directed polyclonal antibody (anti-SLP2, target sequence 1481–1496 of the cardiac Na+ channel α-subunit) eliminated fast Na+ inactivation to induce burst activity which was accompanied by the occurrence of two open states. A deactivation process terminated channel activity during membrane depolarization proceeding with time constants of close to 40 ms (at –40 mV). NBA-modified and iodate-modified Na+ channels were kinetically indistinguishable from the anti-SLP2-modified type since they likewise deactivate and, thus, attain an only moderate Po of close to 20%. This is fundamentally different from the behaviour of enzymatically-modified Na+ channels: after cytosolic proteolysis with α-chymotrypsin, trypsin or pronase, mean Po during membrane depolarization amounted to approximately 40% because deactivation operated extremely slowly and less efficiently (time constants 100–200 ms at –40 mV, as a minimum) or was virtually non-operating. In-vitro cleavage of the synthetic linker sequence 1481–1496 confirmed that this part of the α-subunit provides a substrate for these peptidases or reactants for NBA but cannot be chemically modified by iodate. This iodate resistance indicates that iodate-modified Na+ channels are based on a structural alteration of still another region which is also involved in Na+ inactivation, besides the linker between domains III and IV of the α-subunit. Endogenous peptidases such as calpain did not affect Na+ inactivation. This stresses the stochastic nature of a kinetic peculiarity of cardiac Na+ channels, mode-switching to a non-inactivating mode.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 147-181 
    ISSN: 1075-2617
    Keywords: peptide ; siderophore ; microbial metabolites ; iron ; complex ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Siderophores are low molecular weight iron chelators, produced by virtually all bacteria, fungi and some plants. They serve to deliver the essential element iron, barely soluble under aerobic conditions, into microbial cells. Siderophores are therefore important secondary metabolites which are very often based on amino acids and their derivatives. Biosynthesis, transport, regulation and chemical synthesis of natural siderophores and their analogues is of considerable interest for the protein and peptide chemist. This review gives an overview of the structural classes of peptidic siderophores, along with data on their biosynthesis. On a number of representative examples, strategies and schemes of their chemical synthesis are described. ©1998 European Peptide Society and John Wiley & Sons, Ltd.
    Additional Material: 34 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0021-9304
    Keywords: growth substrates ; laminin ; adhesion peptides ; electrochemical coupling ; cell adhesion ; axonal growth ; surface functionalization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Interactions between cultured nerve cells and surfaces are of importance for the implantation of biocompatible electrode materials such as glassy carbon (GC). Since implants serve as recording sensors in prosthetic neuroscience, we investigated whether coating electrodes with certain laminin derivatives containing the peptide sequences SIKVAV, CDPGYIGSR, PDSGR, YFQRYLI, and RNIAEIIKDA influences neuronal adhesion and neurite outgrowth in vitro. The coating of GC was performed by electrochemical polymerization and, for comparison, by adsorption or covalent coupling. Electrochemical polymerization is suitable for the coupling of peptides to GC, as shown by amino acid analysis and sequencing. Embryonic chicken retinal ganglion cells and brain cells (days E7 or E17) were used for both attachment and growth studies. Surfaces made by electrochemical polymerization of peptides were more efficient than those made by adsorption or covalent coupling of peptides. Synthetic cyclic peptide derivatives of CDPGYIGSR and 18-mer SIKVAV were found to be more efficient than the linear peptides. Competitive effects that resulted in a decreased cell attachment could be found upon application of soluble peptides. Nevertheless, irrespective of the method of coating, peptides were less efficient compared with the whole laminin molecule, as expected from its multiple adhesion sites. When small GC pins were implanted into the brain of E17 chicken after coating with the 18-mer SIKVAV peptide, nerve cell attachment was observed in vivo. The results suggest that chronically implantable materials may exert a higher neurocompatibility when coated with synthetic peptides. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 278-288, 1998.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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