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稀土可通过食物链进入生命体并累积已成为不争的事实,但稀土离子的植物细胞化学行为尚不清楚.本文通过~(140)La(Ⅲ)、~(141)Ce(Ⅲ)、~(160)Tb(Ⅲ)在植物体内放射自显影技术和量子化学计算等研究发现,化学性质相似的稀土离子La(Ⅲ)、Ce(Ⅲ)、Tb(Ⅲ)在细胞质膜和质膜外作用靶点显著不同,即Ce(Ⅲ)主要与质膜物质发生键合,La(Ⅲ)还能与细胞质膜外的细胞外物质和胞外基质分子键合,Tb(Ⅲ)更可与细胞壁物质键合;La(Ⅲ)和Tb(Ⅲ)与胞吞作用进入细胞的物质发生键合而进入细胞,Ce(Ⅲ)尚未观察到此现象;La(Ⅲ)和Tb(Ⅲ)与细胞质膜和质膜外物质通过配位共价键及分子间氢键形成稳定的路易斯酸碱配合物,Ce(Ⅲ)则可能仅靠库仑力与细胞质膜物质发生作用.由此导致La(Ⅲ)、Ce(Ⅲ)、Tb(Ⅲ)3种离子对细胞的作用靶点具有明显选择性,其中Ce(Ⅲ)的选择性>La(Ⅲ)>Tb(Ⅲ).可见,3种稀土离子不同数量f电子的成键活性所致细胞质膜及膜外靶分子键长、键角等参数差异,将导致下游信号转导及细胞化学行为迥异,终致其毒理不同.本文结果可为科学探究稀土累积对生物危害的细胞学机理提供新的思考与借鉴,也为稀土食品安全及人类健康预防提供重要指导.
It is an indisputable fact that rare earths can enter and accumulate in the living body through the food chain, but the chemical behavior of rare earth ions in plant cells is not yet clear.In this paper, the chemical composition of La (Ⅲ), ~ (141) Ce (Ⅲ), ~ ) Tb (Ⅲ) autoradiography and quantum chemical calculations in plants showed that rare earth ions La (Ⅲ), Ce (Ⅲ) and Tb (Ⅲ) with similar chemical properties were found to be targets outside the plasma membrane and plasma membrane Significantly different, that is, Ce (Ⅲ) mainly binds to the plasma membrane material, La (Ⅲ) can also bind to extracellular and extracellular matrix molecules outside the plasma membrane, and Tb (Ⅲ) La (Ⅲ) and Tb (Ⅲ) enter into the cells by the endocytosis into the cells, and this phenomenon has not been observed by Ce (Ⅲ); La (Ⅲ) and Tb Ce (Ⅲ) may interact with cytoplasmic membrane material only by Coulomb force, which leads to the formation of stable Lewis acid-base complexes by coordinate covalent bonds and intermolecular hydrogen bonds. As a result, La (Ⅲ), Ce ), Tb (Ⅲ) three kinds of ions on the cell target has obvious selectivity, Ce (Ⅲ)> La (Ⅲ)> Tb (Ⅲ) .Can be seen that the three kinds of rare earth ions Differences in parameters such as bond length and bond angle between the plasma membrane and extracellular membrane molecules resulting from the bonding activity of the number f electrons will result in different signal transduction and cytochemical behaviors downstream and ultimately result in different toxicological effects. Rare earth accumulation on the biological hazards of cytology provide new thinking and reference, but also for rare earth food safety and human health prevention provide an important guide.