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  • 1
    ISSN: 1570-7458
    Keywords: Nilaparvata lugens ; mannose-binding lectins ; Galanthus nivalis agglutinin ; Narcissus pseudonarcissus agglutinin ; Allum sativum agglutinin ; Oryza sativa agglutinin ; Urtica dioica agglutinin ; N-acetylglucosamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Insect feeding trials were carried out to determine the effects of a range of mannose-specific lectins on third instar nymphs of the rice brown planthopper (BPH),Nilaparvata lugens. Stål. Dose response curves show thatGalanthus nivalis agglutinin (GNA) has the strongest toxic effect of the lectins tested, and is effective at concentrations considerably lower than those previously reported.Narcissus pseudonarcissus agglutinin (NPA) andAllium sativum agglutinin (ASA) exhibit a significant antimetabolic effect towards the insect but were less effective (on a molar basis) than GNA.LC50 values for GNA, NPA and ASA are approximately 4 μM, 11 μM and 〉40μM respectively. These mannose-specific lectins are serologically identical, but differ in the number of subunits per protein molecule; ASA is a dimer, NPA is a trimer and GNA is a tetramer. The results obtained support the hypothesis, that the effectiveness of the mannose-binding lectins as antimetabolites is determined by the number of subunits per molecule. Two N-acetylglucosamine binding lectins, the dimericOryza sativa agglutinin (OSA) and the monomericUrtica dioica agglutinin (UDA), were also tested but at a concentration of 0.1% w/v exhibited no significant antimetabolic effect towards BPH, although the related lectin wheatgerm agglutinin (WGA) has previously been demonstrated to be toxic towards the insect.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4935
    Keywords: Urtica dioica agglutinin ; chitooligosaccharide-binding lectin ; Isothermal titration calorimetry ; thermodynamic parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract UDA (Urtica dioica agglutinin) contains two hevein like domains with two non-identical interacting sites and is specific for chitooligosaccharides. The binding of chitooligosaccharides to UDA was studied by Isothermal Titration Calorimetry. Each site is composed of three subsites, each binding to a sugar residue. Thermodynamic parameters obtained show that while chitobiose has two independent non-interacting sites, chitotriose, chitotetrose and chitopentose have two interacting sites on each monomer of UDA. Values of binding enthalpy (ΔH) increase almost by a factor of 7 in going from chitobiose to chitotriose indicating the existence of three subsites in the combining site of UDA. The binding constant for chitotetrose and chitopentose increase without any further enhancement in the values of ΔH indicating that for oligomers larger than chitotriose interaction is favoured entropically.
    Type of Medium: Electronic Resource
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