葫芦[8]尿腔中顺序包含两个小碱阳离子：动力学和热力学研究,Physical Chemistry Chemical Physics

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葫芦[8]尿腔中顺序包含两个小碱阳离子：动力学和热力学研究
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2014-07-31 00:00:00 , DOI: 10.1039/c4cp02919d
Zsombor Miskolczy _{1,

2,

3,

4} , László Biczók _{1,

2,

3,

4}

Affiliation

将吸收光谱和荧光光谱研究与等温量热滴定和停止流测量相结合，是揭示葫芦[8] uril（CB8）形成包合物的热力学和动力学的有效方法。小ber碱（B ⁺），一种药学上重要的天然生物碱，具有独特的光物理特性，可用来区分连续的包囊过程，并检查其在CB8腔中的分布。B ⁺对环境的高度敏感的荧光寿命允许选择性检测各种葫芦科草配合物，并表明嵌入的客体可与水相互作用的程度。高度稳定的1：1和2-1 B ⁺ ：由于从CB8内部释放了高能水分子，产生了CB8复合物，并且第二个结合步骤被证明几乎放热了3倍。有利的熵变化对1：1封装的驱动力有明显贡献。相反，第二种B ⁺在CB8中的嵌入导致熵大大降低。通过记录B ⁺和CB8快速混合后的荧光强度变化，实时跟踪封装动力学。没有发现中间体的证据。（64±9）×10 ⁶和（5.0±0.5）×10 ⁶ M ^-1 s ^-1的速率常数分别以1：1和2：1的关联得到，而在283 K时，逆过程的速率常数分别为3.8±0.6和0.6±0.1 s ^-1。

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Sequential inclusion of two berberine cations in cucurbit[8]uril cavity: kinetic and thermodynamic studies

A combination of absorption and fluorescence spectroscopic studies with isothermal calorimetric titrations and stopped-flow measurements is a powerful way to reveal the thermodynamics and kinetics of inclusion complex formation with cucurbit[8]uril (CB8). The unique photophysical characteristics of berberine (B⁺), a pharmaceutically important natural alkaloid, were exploited to distinguish the consecutive encapsulation processes, and to examine the confinement in the CB8 cavity. The highly environment sensitive fluorescence lifetime of B⁺ permitted the selective detection of various cucurbituril complexes, and indicated to what extent the embedded guest was available for interaction with water. Highly stable 1 : 1 and 2 : 1 B⁺ : CB8 complexes were produced due to the release of the high energy water molecules from the CB8 interior, and the second binding step proved to be almost 3 times more exothermic. The favorable entropy change contributed appreciably to the driving force of 1 : 1 encapsulation. In contrast, the embedment of the second B⁺ in CB8 led to substantial entropy diminution. The kinetics of encapsulation was followed in real time by recording the fluorescence intensity change after rapid mixing of B⁺ and CB8. No evidence was found for intermediates. The rate constants of (64 ± 9) × 10⁶, and (5.0 ± 0.5) × 10⁶ M⁻¹ s⁻¹ were found for the 1 : 1 and 2 : 1 associations, whereas 3.8 ± 0.6, and 0.6 ± 0.1 s⁻¹ were obtained as the rate constants of the reverse processes at 283 K, respectively.

更新日期：2014-07-31

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