| Abstract
| - Complex stability constant (K), standard free energy (ΔG°), reaction enthalpy (ΔH°), and entropychange (TΔS°) for 1:1 inclusion complexation of the diastereomeric dipeptides Z-d/l-Glu-l-Tyr (Z =benzyloxycarbonyl) and its component amino acids (Z-d/l-Glu and N-Ac-Tyr) with native α-, β-, andγ-cyclodextrins (CDs) and A,X-modified bis(6-trimethylammonio-6-deoxy)-β-CDs (AX-TMA2-β-CDs) weredetermined in buffer solution (pH 6.9) at T = 298.15 K by isothermal titration microcalorimetry. ConcurrentNMR spectral examinations revealed that the penetration mode and the resulting complex architecture aredramatically altered by the peripheral modification and also by the CD's cavity size. Upon complexation ofthe ditopic Z-Glu-Tyr guest, native α- and β-CDs preferentially bind the Z's phenyl group, whereas AX-TMA2-β-CDs predominantly include the Tyr's phenol moiety. In contrast, native γ-CD includes both of thearomatic moieties simultaneously in the same cavity. Furthermore, for isomeric AB-, AC, and AD-TMA2-β-CDs, an inversion of enantioselectivity and a switching of the penetration mode were observed, criticallydepending on the position of TMA substituents.
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