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Synthesis and Guest-Binding Properties of pH/Reduction Dual-Responsive Cyclophane Dimer
| Content Provider | MDPI |
|---|---|
| Author | Hayashida, Osamu Tanaka, Yudai Miyazaki, Takaaki |
| Copyright Year | 2021 |
| Description | A water-soluble cyclophane dimer having two disulfide groups as a reduction-responsive cleavable bond as well as several acidic and basic functional groups as a pH-responsive ionizable group 1 was successfully synthesized. It was found that 1 showed pH-dependent guest-binding behavior. That is, 1 strongly bound an anionic guest, 6-p-toluidinonaphthalene-2-sulfonate (TNS) with binding constant $(K/M^{−1}$) for 1:1 host-guest complexes of 9.6 × $10^{4}$ $M^{−1}$ at pH 3.8, which was larger than those at pH 7.4 and 10.7 (6.0 × $10^{4}$ and 2.4 × $10^{4}$ $M^{−1}$, respectively), indicating a favorable electrostatic interaction between anionic guest and net cationic 1. What is more, release of the entrapped guest molecules by 1 was easily controlled by pH stimulus. Large favorable enthalpies (ΔH) for formation of host-guest complexes were obtained under the pH conditions employed, suggesting that electrostatic interaction between anionic TNS and 1 was the most important driving force for host-guest complexation. Such contributions of ΔH for formation of host-guest complexes decreased along with increased pH values from acidic to basic solutions. Upon addition of dithiothreitol (DTT) as a reducing reagent to an aqueous PBS buffer (pH 7.4) containing 1 and TNS, the fluorescence intensity originating from the bound guest molecules decreased gradually. A treatment of 1 with DTT gave 2, having less guest-binding affinity by the cleavage of disulfide bonds of 1. Consequently, almost all entrapped guest molecules by 1 were released from the host. Moreover, such reduction-responsive cleavage of 1 and release of bound guest molecules was performed more rapidly in aqueous buffer at pH 10.7. |
| Starting Page | 3097 |
| e-ISSN | 14203049 |
| DOI | 10.3390/molecules26113097 |
| Journal | Molecules |
| Issue Number | 11 |
| Volume Number | 26 |
| Language | English |
| Publisher | MDPI |
| Publisher Date | 2021-05-22 |
| Access Restriction | Open |
| Subject Keyword | Molecules Organic Chemistry Cyclophane Dimer Host-guest Complexation Ph-dependent Guest-binding Reduction-responsive Guest Release |
| Content Type | Text |
| Resource Type | Article |
