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  • charybdotoxin  (2)
  • genebank  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Use of toxins to study potassium channels (1991)
    Springer
    Journal of bioenergetics and biomembranes 23 (1991), S. 615-646 
    Details
    ISSN: 1573-6881
    Keywords: Potassium channels ; venoms ; charybdotoxin ; noxiustoxin ; iberiotoxin ; apamin ; leiurotoxin 1 ; dendrotoxin ; membrane vesicles ; peptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Potassium channels comprise groups of diverse proteins which can be distinguished according to each member's biophysical properties. Some types of K+ channels are blocked with high affinity by specific peptidyl toxins. Three toxins, charybdotoxin, iberiotoxin, and noxiustoxin, which display a high degree of homology in their primary amino acid sequences, have been purified to homogeneity from scorpion venom. While charybdotoxin and noxiustoxin are known to inhibit more than one class of channel (i.e., several Ca2+-activated and voltage-dependent K+ channels), iberiotoxin appears to be a selective blocker of the high-conductance, Ca2+-activated K+ channel that is present in muscle and neuroendocrine tissue. A distinct class of small-conductance Ca2+-activated K+ channel is blocked by two other toxins, apamin and leiurotoxin-1, that share no sequence homology with each other. A family of homologous toxins, the dendrotoxins, have been purified from venom of various related species of snakes. These toxins inhibit several inactivating voltage-dependent K+ channels. Although molecular biology approaches have been employed to identify and characterize several species of voltagegated K+ channels, toxins directed against a particular channel can still be useful in defining the physiological role of that channel in a particular tissue. In addition, for those K+ channels which are not yet successfully probed by molecular biology techniques, toxins can be used as biochemical tools with which to purify the target protein of interest.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00785814
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  • 2
    Electronic Resource
    Electronic Resource
    High-conductance calcium-activated potassium channels; Structure, pharmacology, and function (1996)
    Springer
    Journal of bioenergetics and biomembranes 28 (1996), S. 255-267 
    Details
    ISSN: 1573-6881
    Keywords: maxi-K channels ; charybdotoxin ; iberiotoxin ; smooth muscle ; ion channel purification ; slo channels ; Β-subunit ; K channel agonists ; K channel blockers ; ion channel pharmacology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract High-conductance calcium-activated potassium (maxi-K) channels comprise a specialized family of K+ channels. They are unique in their dual requirement for depolarization and Ca2+ binding for transition to the open, or conducting, state. Ion conduction through maxi-K channels is blocked by a family of venom-derived peptides, such as charybdotoxin and iberiotoxin. These peptides have been used to study function and structure of maxi-K channels, to identify novel channel modulators, and to follow the purification of functional maxi-K channels from smooth muscle. The channel consists of two dissimilar subunits, α and Β. The α subunit is a member of theslo Ca2+-activated K+ channel gene family and forms the ion conduction pore. The Β subunit is a structurally unique, membrane-spanning protein that contributes to channel gating and pharmacology. Potent, selective maxi-K channel effectors (both agonists and blockers) of low molecular weight have been identified from natural product sources. These agents, together with peptidyl inhibitors and site-directed antibodies raised against α and Β subunit sequences, can be used to anatomically map maxi-K channel expression, and to study the physiologic role of maxi-K channels in various tissues. One goal of such investigations is to determine whether maxi-K channels represent novel therapeutic targets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02110699
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  • 3
    Electronic Resource
    Electronic Resource
    Colombia and Venezuela 1992 wild potato (Solanum sect. Petota) germplasm collecting expedition: taxonomy and new germplasm resources (1995)
    Springer
    Euphytica 81 (1995), S. 45-56 
    Details
    ISSN: 1573-5060
    Keywords: Colombia ; genebank ; germplasm ; Solanum sect. Petota ; taxonomy ; Venezuela
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We conducted a joint Colombia/United States/Venezuela wild potato (Solanum sect. Petota Dumort.) germplasm collecting expedition in Colombia from June 27–August 24, and in Venezuela from August 17–September 15, 1992. The goals of the expedition were to collect germplasm and study the species boundaries of all of the 23 Colombian and Venezuelan taxa accepted by current taxonomists. We made 128 collections of 16 of these taxa, 96 as true seed collections. We collected the first available germplasm collections of S. cacetanum, S. cuatrecasasii, S. estradae, S. lobbianum, S. orocense, S. paramoense, and S. sucubunense, and obtained germplasm collections of S. neovalenzuelae and S. pamplonense as a germplasm exchange from the Colombian national germplasm collection. We had problems identifying some of our collections, and currently are investigating them for species status and interrelationships. We summarize the state of germplasm collections for Colombia and Venezuela, provide our field data regarding the taxonomy of Colombian and Venezuelan wild potatoes, and provide recommendations for future collecting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00022458
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