The spectrophotometric titrations have been performed in buffered aqueous solution (pH=7.20) at 25~40℃ to give the stability constants (logKs) and the thermodynamic parameters (△H^O and △SO) for the supramolecular system formed by various amino acids with mono-[6-(1-pyridinio)-6-deoxy]-α and γ-cyclodextrins (1) and (3), and the results were compared with the data reported for mono-[6-(1-pyridinio)-6-deoxy]-β-cyclodextrin (2). The supramolecular system stoichiometry is 1:1 for all amino acid inclusion complexation with host compounds (1) and (3). The contributions of the size-fit or shape-fit and the several weak forces working between chemically modified cyclodextrins and guest amino acids, which include van der Waals forces, hydrogen bonding, and hydrophobic interactions upon forming supramolecular system are discussed from a viewpoint of thermodynamics. The thermodynamic parameters obtained indicate that the cyclodextrin derivatives carrying one positively charged pyridinio moiety as a molecular probe can recognize not only the differences between the molecular size and shape of amino acids, but also the L/D-amino acid chiral isomer, it further indicates the important action of the molecular receptor upon the selectivity to combine substrate to form the supramolecular system.

Key words: SPECTROPHOTOMETRY, AMINO ACID, PYRIDINE P, THERMODYNAMIC PROPERTIES, STABILITY CONSTANT, CYCLODEXTRIN, CHEMICLAL MODIFICATION, OLECULAR RECOGNITION