The apoenzyme of DNA photolyase can efficiently repair its substrate after excitation by 280 nm light (Φ＝0.56). In order to mimic this repair process of apoenzyme, we synthesized two model compounds, in which tryptophan and/or tyrosine was covalently linked to cyclobutane thymine dimer, and measured the splitting quantum yield of dimer under 295 nm light. By investigating the photosensitized splitting properties of the dimer, some new insights into the intramolecular electron-transfer process were gained.

Key words: DNA photoreactivation, cyclobutane thymine dimer, tryptophan, tyrosine, model study