Molecular recognition of DNA intercalators at nanomolar concentration in water.
Molecular recognition of DNA intercalators at nanomolar concentration in water.
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水中纳摩尔浓度 DNA 嵌入剂的分子识别。
DOI：
10.1021/ja015641o
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发表时间：
2001
影响因子：
15
通讯作者：
S. Kitagawa
中科院分区：
文献类型：
--
作者：
T. Mizutani;K. Wada;S. Kitagawa
开发能够与具有高亲和力和高选择性的生物活性分子结合的人工受体，并了解识别的基本原理是化学领域的一个有趣的课题。为了合理设计受体/配体相互作用1,2，已经有几次尝试评估功能基团或组成原子对结合自由能的贡献，使用酶抑制剂、抗体-抗原和蛋白质-配体结合的汇编数据。为了更深入地了解识别相互作用，使用合成受体进行研究是可取的，因为在控制受体构象的同时，官能团的系统变化是可能的。尽管我们对识别机制的了解仍然有限，但许多研究表明，更大的受体-客体接触表面积将导致更大的来自受体/客体相互作用和脱溶过程的驱动力。我们在这里报道了基于双卟啉的合成受体，具有与客体的大接触表面积，在水中以前所未有的亲和力与DNA插入物如吖啶橙，DAPI和溴化乙啶结合。以钯催化的交叉偶联反应为关键步骤，制备了山墙型卟啉化合物。我们制备了两种水溶性山墙卟啉，如方案1所示。用盐酸处理1，Zn2, 1， H4酯，碱水解制得1，Zn2, 1， H4游离碱。1H NMR （D2O和MeOH-d4）和质谱研究证实了受体的结构。受体1，Zn2, 1， H4和2，Zn2可溶于甲醇和水（pH> 7.0）。用紫外可见光谱和荧光光谱研究了不同来宾的结合。添加5-11后，1、Zn2、1、H4和2、Zn2的Soret波段被移向更长的波长。7 5-7的荧光被加入1，Zn2猝灭，而1，Zn2的荧光被加入8和9猝灭。图1显示，5 （47 nM）的荧光被加入纳摩尔浓度的1，Zn2猝灭。在pH为9的0.1 M硼酸盐缓冲液中，25℃时的结合常数由最小二乘曲线拟合确定，并总结在表1中。8 Job图和曲线拟合表明，受体与5-7、10和11之间形成1:1复合物和1:1复合物（受体：客体）。对于8和9，只形成了1:1的络合物。Zn2的结合常数为108。1 M-1的紫外可见光谱通过跟随卟啉索瑞特波段的红移，与荧光滴定测定的结果基本一致。6的荧光被
The development of artificial receptors capable of binding to biologically active molecules with high affinity and high selectivity, and understanding the underlying principles of recognition are an intriguing subject of chemistry. For rational design of receptor/ligand interactions, 1, 2 there have been several attempts to evaluate contributions of functional groups or constituent atoms to the binding free energy, using compiled data of enzymeinhibitor, antibody-antigen, and protein-ligand binding. 3 To gain deeper insight into recognition interactions, studies using synthetic receptors are desirable since systematic variation of the functional groups is possible while controlling conformation of the receptors. Although our knowledge of the recognition mechanism is still limited, a number of studies suggested that a larger receptorguest contact surface area would result in a greater driving force from receptor/guest interactions and desolvation processes. We report here that bisporphyrin-based synthetic receptors, having a large contact surface area with guest, bind to DNA intercalators such as acridine orange, DAPI, and ethidium bromide with unprecedented affinity in water. 4 Gable-type porphyrins5 were prepared using the palladiumcatalyzed cross-coupling reaction as a key step. 6 We prepared two water-soluble gable porphyrins as shown in Scheme 1. The free base of 1 ‚Zn2, 1 ‚H4, was prepared by treatment of the ester of 1 ‚Zn2 with HCl, followed by alkaline hydrolysis. 1H NMR (both in D2O and in MeOH-d4) and mass spectroscopic studies confirmed the structure of the receptors. Receptors 1 ‚Zn2, 1 ‚H4, and 2 ‚Zn2 are soluble in methanol and in water (pH> 7.0). Binding of various guests was studied by UV-visible and fluorescence spectroscopy. Upon addition of5-11, the Soret band of 1 ‚Zn2, 1 ‚H4, and 2 ‚Zn2 was shifted to longer wavelength. 7 The fluorescence of 5-7 was quenched by the addition of 1 ‚Zn2, while the fluorescence of 1 ‚Zn2 was quenched by the addition of 8 and 9. Figure 1 shows that the fluorescence of 5 (47 nM) is quenched by the addition of a nanomolar concentration of 1 ‚Zn2. The binding constants at 25 C in 0.1 M borate buffer at pH 9 are determined by least-squares curve fitting and are summarized in Table 1. 8 Job plot and the curve fitting showed that both a 1: 1 complex and a 1: 2 (receptor: guest) complex were formed between the receptors and 5-7, 10, and 11. For 8 and 9, only a 1: 1 complex was formed. The binding constant of 9 to 1 ‚Zn2 was also determined to be 108. 1 M-1 by UV-visible spectroscopy by following a red shift of the Soret band of porphyrin, in reasonable agreement with that determined by fluorescence titration. 9 The fluorescence of 6 quenched by the