PHOTO-RESPONSIVE CATALYSIS BY THYMINE-CYCLODEXTRIN CONJUGATES

Primary hydroxy groups of beta-cyclodextrin (beta-CD) have been substi tuted with thymine (Thy) groups. By photo-irradiation with UV light at 280 nm, the introduced thymine groups adjacent to the CD cavity under went reversible dimerization and the catalytic efficiency (k(cat)/K-dl ss) of the modified CD in the hydrolyses of p-nitrophenyl acetate and m-nitrophenyl acetate increased. By further irradiation with light at 240 nm, the catalytic efficiency decreased to that of the CD-Thy conju gate due to the photo-cleavage of the thymine dimer. This phenomenon i mplies that the binding of guest molecules by the CD-Thy conjugate and subsequent change in the catalytic efficiency of the conjugate occurr ed photo-responsively The steric effect on the acceleration or deceler ation of the hydrolyses of phenyl esters by CD-Thy and its derivatives is also discussed.