An On/Off Circular Dichroism Signal Reveals a pH Dependent Competition between a Cyclodextrin and a Polyelectrolyte for an Atropisomeric Aromatic Guest
An On/Off Circular Dichroism Signal Reveals a pH Dependent Competition between a Cyclodextrin and a Polyelectrolyte for an Atropisomeric Aromatic Guest
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开/关圆二色性信号揭示了环糊精和聚电解质之间对阻转异构芳香客体的 pH 依赖性竞争
DOI：
10.1021/ja972789s
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发表时间：
1997
影响因子：
15
通讯作者：
A. Müller
中科院分区：
文献类型：
--
作者：
Sung;Mark M. Green;G. Schultz;S. Jha;S. Jha;A. Müller
在下一篇论文中，我们展示了如何利用pH依赖的聚甲基丙烯酸（PMA）疏水特性，在环糊精和作为PMA标记的atrosom异构芳香基团之间形成可逆的超分子复合物。该系统由手性光信号监测，该信号不仅对测量时的pH值敏感，而且对样品的pH值和时间历史都敏感。环糊精1与萘衍生物之间的配合物引起了较大的诱导圆二色性（ICD）效应，这与不对称环糊精内腔对萘发色团的扰动有关。2然而，当0.6%的聚甲基丙烯酸（PMA）的单体单元与4-溴甲基- 1,1′-联萘基3(1)发生酯化反应时，即使加入大量的γ-环糊精，也没有显示出圆二色性信号。然而，当pH高于6时，预期的诱导圆二色性（ICD）出现，这表明芳香发色团在环糊精腔中掺入。pH值为10时，该配合物的结合常数为1250l /M。当pH值低于6时，ICD立即消失，当pH值高于6时，ICD再次出现。5,6图1显示了pH值与ICD之间的相互作用，下面将讨论pH值
In the following paper, we show how the pH dependent hydrophobic characteristics of poly (methacrylic acid)(PMA) may be used to develop a reversible supramolecular complex between a cyclodextrin and an atropisomeric aromatic group bound as a label to the PMA. The system is monitored by a chiral optical signal which is sensitive not only to the pH at the time of measurement but also to both the pH and time history of the sample.The complexes between cyclodextrins1 and naphthalene derivatives cause a large induced circular dichroism (ICD) effect associated with the naphthalene chromophore perturbed by the asymmetric cyclodextrin internal cavity. 2 However an aqueous solution of polymethacrylic acid (PMA), 0.6% of whose monomer units were esterified with 4-bromomethyl-1, 1′-binaphthyl3 (1) showed no circular dichroism signal on addition of even large excesses of γ-cyclodextrin. When the pH is raised above 6, however, the expected induced circular dichroism (ICD) appears signaling the incorporation of the aromatic chromophore in the cyclodextrin cavity. The binding constant for this complex is 1250 L/M at pH 10. 4 This ICD instantly disappears on reducing the pH below near to 6 and reappears when the pH is raised above this point. 5, 6 Figure 1 exhibits this interplay between the pH and the ICD and, to be discussed below, the pH