COOPERATIVE BINDING BY AGGREGATED MONO-6-(ALKYLAMINO)-BETA-CYCLODEXTRINS
COOPERATIVE BINDING BY AGGREGATED MONO-6-(ALKYLAMINO)-BETA-CYCLODEXTRINS
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DOI：
10.1021/ja00166a021
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发表时间：
1990-05-09
影响因子：
15
通讯作者：
LIN, FT
中科院分区：
文献类型：
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作者：
PETTER, RC;SALEK, JS;LIN, FT
6-(十六氨基)-β-环糊精(5)和6-(辛氨基)-β-环糊精(4)与有机客体(4-硝基苯酚、4-羟基苯甲酸、环己烷羧酸等)进行了滴定。在水溶液中给出S型结合等温线。根据Hill方程重新绘制这些数据，得到Hill系数>；1.0(在5和4-硝基苯酚的情况下为2.2)。相反，β-环糊精(β-CD)和单-6-氨基-β-环糊精(3)都表现出双曲线结合等温线，导致Hill系数接近1。希尔系数大于1是合作性的实验标志，其中最初的结合事件使随后的结合事件更有利。协作性的程度对主体(4和5)的浓度和溶剂(在DMSO中协作性被抑制)很敏感。用电导、动态光散射和核磁共振研究了两亲主体(4和5的cmc分别为200和1.4µm)的聚集性质。提出并讨论了两种可能的机制来解释观察到的协作性。
Mono-6-(hexadecylamino)-.beta.-cyclodextrin (5) and mono-6-(octylamino)-.beta.-cyclodextrin (4) have been titrated against organic guests (4-nitrophenol, 4-hydroxybenzoic acid, cyclohexanecarboxylic acid, etc.) in aqueous solution to give sigmoidal binding isotherms. Replotting of these data according to the Hill equation gives Hill coefficients > 1.0 (2.2 in the case of 5 and 4-nitrophenol). In contrast, both .beta.-cyclodextrin (.beta.-CD) and mono-6-amino-.beta.-cyclodextrin (3) both exhibit hyperbolic binding isotherms, leading to Hill coefficients close to unity. Hill coefficients greater than one are the experimental hallmark of cooperativity, in which initial binding events render subsequent binding events more favorable. The degree of cooperativity is sensitive to the concentration of the hosts (4 and 5) and the solvent (cooperativity is suppressed in DMSO). These results are discussed in terms of the aggregation properties of the amphipathic hosts (cmc = 200 and 1.4 .mu.M, for 4 and 5, respectively), which were studied by conductivity, dynamic light scattering, and NMR. Two possible mechanisms to account for the observed cooperativity are presented and discussed.