Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, Switzerland.
Environ Sci Technol. 2010 Dec 1;44(23):8870-6. doi: 10.1021/es103008s. Epub 2010 Oct 29.
Genetically modified Bt crops express insecticidal Cry proteins (Bt toxins) that may enter agricultural soils. A mechanistic understanding of Cry protein adsorption to soils is critical for risk assessment, as this process governs Cry protein fate and bioavailability. We used quartz crystal microbalance and optical waveguide lightmode spectroscopy to elucidate the driving forces of the adsorption of monomeric Cry1Ab to negatively charged quartz (SiO(2)) and positively charged poly-L-lysine (PLL) at pH 5-8 and constant ionic strength of 50 mM (NaCl). Bovine serum albumin and hen egg white lysozyme were used as reference proteins because of their known adsorption behavior. Electrostatics governed Cry1Ab adsorption; as pH increased above the isoelectric point of Cry1Ab, the initial rate and the extent of adsorption decreased on SiO(2) and increased on PLL. Reversible adsorption to SiO(2) suggested weak Cry1Ab-SiO(2) electrostatic interactions and no irreversible conformational changes of Cry1Ab at the surface. High conformational stability of Cry1Ab was further supported by supply rate-independent extent of adsorption of Cry1Ab to apolar gold. Some evidence is presented that the nonuniform surface charge distribution of Cry1Ab resulted in patch-controlled electrostatic attraction with sorbents that carried the same net charge as Cry1Ab. A more detailed discussion of this mechanism is given in a companion paper.
基因改良的 Bt 作物表达杀虫 Cry 蛋白（Bt 毒素），这些毒素可能进入农业土壤。了解 Cry 蛋白在土壤中的吸附机制对于风险评估至关重要，因为这一过程决定了 Cry 蛋白的命运和生物利用度。我们使用石英晶体微天平（QCM）和光波导光模式光谱法（OWLS），在 pH 值为 5-8 且离子强度恒为 50 mM（NaCl）的条件下，阐明了 Cry1Ab 单体对带负电荷的石英（SiO2）和带正电荷的聚-L-赖氨酸（PLL）的吸附驱动力。由于其已知的吸附行为，牛血清白蛋白和鸡卵清白溶菌酶被用作参考蛋白。静电作用力控制着 Cry1Ab 的吸附；当 pH 值高于 Cry1Ab 的等电点时，Cry1Ab 在 SiO2 上的初始吸附速率和吸附程度降低，而在 PLL 上则增加。Cry1Ab 在 SiO2 上的可逆吸附表明，Cry1Ab 与 SiO2 之间的静电相互作用较弱，且 Cry1Ab 在表面上没有发生不可逆的构象变化。Cry1Ab 具有较高的构象稳定性，这进一步得到了其对非极性金的吸附程度与供应速率无关的证据支持。有一些证据表明，Cry1Ab 的非均匀表面电荷分布导致了带有与 Cry1Ab 相同净电荷的吸附剂的补丁控制静电吸引。在一篇相关论文中，对该机制进行了更详细的讨论。
