Characterization of azadirachtin binding to Sf9 nuclei in vitro

Alasdair J. Nisbet, A. Jennifer Mordue, Robert B. Grossman, Lyn Jennens, Steven V. Ley, William Mordue

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


[22,23-3H2]dihydroazadirachtin was incorporated by Sf9 cells in culture and was bound specifically to the nuclear fraction. The observed association constant of the binding of the radioligand to a purified nuclear fraction was determined to be 0.037 ± 0.008 min-1 using a one-phase exponential association equation, and binding appeared to be to a single population of sites. The binding was essentially irreversible, and the dissociation constant was estimated to be 0.00065 ± 0.00013 min-1. An association rate constant of 7.3 × 106 M-1 min-1 was calculated from these data. Binding was saturable, and the receptor number and affinity were determined as Bmax = 23.87 ± 1.15 pmol/mg protein, Kd = 18.1 ± 2.1 nM. The order of potency of semisynthetic azadirachtin analogues for competition for the binding site was as follows (IC50 in parentheses): azadirachtin (1.55 × 10-8 M) > dihydroazadirachtin (3.16 × 10-8 M) > dansyl dihydroazadirachtin (7.40 × 10-8 M) > DNP-azadirachtin (7.50 × 10-8 M) > biotin dihydroazadirachtin (1.27 × 10-7 M) ≫ 11-methoxy 22,23-dihydroazadirachtin (6.67 × 10-7 M).

Original languageEnglish
Pages (from-to)461-473
Number of pages13
JournalArchives of Insect Biochemistry and Physiology
Issue number4
StatePublished - 1997


  • Azadirachta indica
  • Neem
  • Proliferation
  • Protein synthesis

ASJC Scopus subject areas

  • Physiology
  • Biochemistry
  • Insect Science


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