The fluorescence spectra have been studied in phosphate buffer aqueous solution(pH=7.20) to give the stability constants( K s) for the supramolecular system formed by L Pro β CD(1), L Leu β CD(2), and L Ileu β CD(3) with TNS. The results obtained indicate that the binding ability of modified β cyclodextrins(1) with TNS is larger than that of 2 and 3. One possible explanation is that there are different substitutes among the three modified β cyclodextrins.The molecular binding ability is discussed from the size fit concept between the host and the guest molecules. The results indicate that the substitute on the side arm attached to the edge of β CD plays a crucial role in guest inclusion.
