da Silva Fernando Luís B, Linse Sara, Jönsson Bo
Department of Theoretical Chemistry and Department of Biophysical Chemistry, Lund University, P.O. Box 124, S-22100 Lund, Sweden.
J Phys Chem B. 2005 Feb 10;109(5):2007-13. doi: 10.1021/jp049304o.
Although interactions in biological systems occur in the presence of a large number of charged species, the binding of charged ligands to different biomolecules is often analyzed in a simplified model focusing only upon the receptor, ligand, and added salt. Here we demonstrate that the presence of charged macromolecules can affect binding to the receptor in an unexpected way. Experimental studies of the binding of barium ions to the chelator 5,5'-dibromo-1,2-bis(O-amino-phenoxy)-ethane-N,N,N',N'-tetraacetic acid in the presence of charged silica sols show that the binding affinity increases with added salt. The experimental findings are verified in Monte Carlo simulations using a dielectric continuum model with a uniform dielectric permittivity throughout the solution. The anomalous salt behavior is caused by a reduction of the chemical potential of the free ligand, which even in the absence of binding interacts strongly with the oppositely charged receptor. These results are also relevant for the interpretation of competition studies often used in the case of strong ligand binding.
尽管生物系统中的相互作用是在大量带电物种存在的情况下发生的，但带电配体与不同生物分子的结合通常在一个简化模型中进行分析，该模型仅关注受体、配体和添加的盐。在这里，我们证明带电大分子的存在会以意想不到的方式影响与受体的结合。在带电硅溶胶存在下，钡离子与螯合剂5,5'-二溴-1,2-双（O-氨基苯氧基）乙烷-N,N,N',N'-四乙酸结合的实验研究表明，结合亲和力随添加盐的增加而增加。实验结果在蒙特卡罗模拟中得到验证，该模拟使用了一个在整个溶液中具有均匀介电常数的介电连续体模型。异常的盐行为是由游离配体化学势的降低引起的，即使在没有结合的情况下，游离配体也会与带相反电荷的受体强烈相互作用。这些结果对于解释在强配体结合情况下经常使用的竞争研究也具有重要意义。
