Institute of Organic Chemistry, University of Zurich, Winterthurerstrasse 190, Switzerland 8057.
Biochemistry. 2010 May 25;49(20):4339-48. doi: 10.1021/bi9020583.
A new family of G-quadruplex ligands termed "amido phthalocyanines" (APcs) was synthesized by reacting variable amino acids with tetraamino zinc phthalocyanine. Variation in the number of methylene units separating the APc scaffold from terminal ammonium groups systematically modulated ammonium pK(a) values that, in turn, mediated APc aggregation and DNA binding. Certain APcs exhibited nearly 1000-fold enhancements in fluorescence quantum yield upon binding G-quadruplex DNA under physiological conditions of pH and ionic strength. G-quadruplexes derived from the c-myc and c-kit promoters and the human telomeric repeat were evaluated for APc affinity and specificity using two complementary and direct fluorescence binding assays that revealed apparent dissociation constants ranging from 20 to 200 nM. Approximately 500-fold lower affinities for duplex and single-stranded DNAs were observed. Interestingly, APc-quadruplex binding was relatively insensitive to ionic strength (0.03-1 M KCl) but highly dependent on the pH of the solution. Our results provide a mechanism for the "turn-on" fluorescence properties exhibited by these compounds that will assist in future rational design of new G-quadruplex-specific fluorescent probes and drug candidates.
一种新的 G-四链体配体家族被称为“酰胺酞菁”（APcs），它是通过将各种氨基酸与四氨基锌酞菁反应合成的。APc 支架与末端铵基团之间的亚甲基单元数量的变化系统地调节了铵 pKa 值，进而介导了 APc 的聚集和 DNA 结合。某些 APc 在生理 pH 值和离子强度条件下与 G-四链体 DNA 结合时，荧光量子产率几乎提高了 1000 倍。使用两种互补的直接荧光结合测定法评估了来源于 c-myc 和 c-kit 启动子以及人类端粒重复序列的 G-四链体的 APc 亲和力和特异性，结果表明表观解离常数范围为 20 至 200 nM。对于双链和单链 DNA 的亲和力约低 500 倍。有趣的是，APc-四链体结合对离子强度（0.03-1 M KCl）相对不敏感，但高度依赖于溶液的 pH 值。我们的结果为这些化合物表现出的“开启”荧光特性提供了一种机制，这将有助于未来设计新的 G-四链体特异性荧光探针和药物候选物。
