Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, Switzerland.
Environ Sci Technol. 2010 Dec 1;44(23):8877-83. doi: 10.1021/es103007u. Epub 2010 Oct 29.
Adsorption governs the fate of Cry proteins from genetically modified Bt crops in soils. The effect of ionic strength (I) on the adsorption of Cry1Ab (isoelectric point IEP(Cry1Ab) ≈ 6) to negatively charged quartz (SiO(2)) and positively charged poly-L-lysine (PLL) was investigated at pH 5 to 8, using quartz crystal microbalance with dissipation monitoring and optical waveguide lightmode spectroscopy. Cry1Ab adsorbed via positively and negatively charged surface patches to SiO(2) and PLL, respectively. This patch controlled electrostatic attraction (PCEA) explains the observed increase in Cry1Ab adsorption to sorbents that carried the same net charge as the protein (SiO(2) at pH > IEP(Cry1Ab) and PLL at pH < IEP(Cry1Ab)) with decreasing I. In contrast, the adsorption of two reference proteins, BSA and HEWL, with different adsorption mechanism, were little affected by similar changes of I. Consistent with PCEA, Cry1Ab desorption from SiO(2) at pH > IEP(Cry1Ab) increased with increasing I and pH. Weak Cry1Ab-SiO(2) PCEA above pH 7 resulted in reversible, concentration dependent adsorption. Solution depletion experiments showed that PCEA also governed Cry1Ab adsorption to SiO(2) particles at environmentally relevant concentrations (a few ng mL(-1)). These results imply that models describing Cry1Ab adsorption to charged surfaces in soils need to account for the nonuniform surface charge distribution of the protein.
吸附作用决定了转基因 Bt 作物中的 Cry 蛋白在土壤中的命运。本研究采用石英晶体微天平（QCM-D）和光波导光模式光谱法，在 pH 值为 5 到 8 之间，研究了离子强度（I）对带负电荷的石英（SiO₂）和带正电荷的聚-L-赖氨酸（PLL）吸附 Cry1Ab（等电点 IEP(Cry1Ab) ≈ 6）的影响。Cry1Ab 通过带正电荷和带负电荷的表面斑块分别吸附到 SiO₂和 PLL 上。这种斑块控制静电吸引（PCEA）解释了观察到的 Cry1Ab 吸附到与蛋白质带相同净电荷的吸附剂上的增加（pH > IEP(Cry1Ab)时的 SiO₂和 pH < IEP(Cry1Ab)时的 PLL），随着 I 的降低而增加。相比之下，具有不同吸附机制的两种参考蛋白（BSA 和 HEWL）的吸附几乎不受类似 I 变化的影响。与 PCEA 一致，Cry1Ab 在 pH > IEP(Cry1Ab)时从 SiO₂的解吸随 I 和 pH 的增加而增加。高于 pH 7 时，Cry1Ab-SiO₂PCEA 较弱，导致可逆、浓度依赖性吸附。溶液耗尽实验表明，PCEA 也控制了 Cry1Ab 在环境相关浓度（数 ng mL⁻¹）下对 SiO₂颗粒的吸附。这些结果表明，描述 Cry1Ab 在带电荷土壤表面吸附的模型需要考虑蛋白质不均匀的表面电荷分布。
