The Kinetics of Ampicillin Complexation by 纬-Cyclodextrins. A Single Molecule Approach

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• 作者：Alina Asandei ; Loredana Mereuta ; Tudor Luchian
• 刊名：Journal of Physical Chemistry B
• 出版年：2011
• 出版时间：August 25, 2011
• 年：2011
• 卷：115
• 期：33
• 页码：10173-10181
• 全文大小：1017K
• 年卷期：v.115,no.33(August 25, 2011)
• ISSN：1520-5207

文摘

Efficient measuring of binding thermodynamics of interactions between cyclodextrins (CDs) and antibiotics remains a challenge in the fields of physical chemistry and pharmaceutics. Here we report on a single-molecule investigation of pH- and voltage-dependent reversible interactions between ampicillin and 纬-CDs, through monitoring of ionic current signatures across an 伪-hemolysin (伪-HL) protein entrapping a 纬-CD molecule. Our data reveal that electric and electro-osmotic driving forces alter the reversible reaction rates of ampicillin interaction with 纬-CDs, as well as free energy changes accompanying the interaction. We found that close to neutral pH values facilitate more unstable 纬-CD鈥揳mpicillin complexes, as well as a decreased affinity of the 纬-CD鈥揳mpicillin reversible interaction, as compared to acidic pH. We posit that a pH-dependent partial electric charge on the ampicillin molecule and anionic selectivity of the 伪-HL路纬CD complex account for the antibiotic and 纬-CD intracavity manifestations. This approach may provide unique alternatives for the characterization of CD鈥揼uest interactions, useful for pharmaceutical formulations and tunable drug delivery systems.