Bt蛋白在矿物表面吸附的光谱研究

he persistence of the insecticidal protein of Bacillus thuringiensis (Bt) may constitute a hazard to the soil ecosystem, however, studies on secondary structures of the Bt toxin adsorbed onto soil minerals are limited. The secondary structures of the toxin, in Na2HPO4-NaH2PO4 buffer (pH 7.0) or adsorbed onto montmorillonite, kaolinite, goethite and silicon dioxide, were carried out by fluorescence spectroscopy, circular dichroism (CD) spectroscopy and infrared spectroscopy (IR). The maximum emission (λem) of the Bt toxin was at 338 nm by the excitation at 282 nm. Theλem of the toxin desorbed from kaolinite and montmorillonite was red shifted 5 and 9.5 nm, respectively, and that of the toxin desorbed from goethite and silicon dioxide was not obviously shifted. The α-helix content of the toxin was reduced while the β-sheet fraction was increased 4.5-17.2% among the toxin adsorption-desorption with minerals, and the ordered structure (α-helix + β-sheet) of the toxin was increased in a certain extent. IR spectroscopy indicated that the conformational of the adsorbed Bt toxin onto minerals were not obviously changed.