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Laser spectroscopy is used to investigate the excited state intramolecular proton transfer (ESIPT)-based UV protection and [super 1][O.sub.2] quenching activity of aloesaponarin I [AS1]. It is seen that the functional groups participating in the excited-state intramolecular proton transfer also play important roles in the singlet oxygen quenching.

The fragment molecular orbital (FMO) method was used to perform molecular orbital calculations of the complex between DNA-ERE (estrogen response element) and ER (estrogen receptor)-DBD (DNA binding domain). The results revealed that the ER-DBD dimer has larger ESP values and therefore can bind more strongly to DNA than the ER-DBD monomer, thus indicating that ER-DBD dimer is crucial for interactions between the recognition helix and base pairs.

Research into the kinetics of reactions 1'-4' in vitamin E solutions and in micellar dispersions indicates that proton tunneling plays a significant role in reactions 1, 3 and 4, but not in the damaging reaction 2.

Excited-state intramolecular proton-transfer (ESIPT) and singlet-oxygen ((1)O2) quenching activities of intramolecularly hydrogen-bonded 1-(acylamino)anthraquinones have been studied by means of static and laser spectroscopies. The ESIPT shows a substituent effect, which can be explained in terms of the nodal-plane model. The ESIPT activity positively and linearly correlates with their (1)O2 quenching activity. The reason for this correlation can be understood by considering ESIPT-induced distortion of their ground-state potential surface and their encounter complex formation with (1)O2. Intramolecularly hydrogen-bonded hydroxyanthraquinones found in aloe also show a similar positive and linear correlation, which can be understood in the same way.