| Abstract
| - Three long-wavelength absorbing dipeptide-modified hypocrellin B (HB) derivatives, Gly-HB, Tyr-HB, andTrp-HB, were prepared for application in photodynamic therapy (PDT). Their abilities to produce free radicalsand singlet oxygen were compared in detail with EPR technique, and their binding interactions with calfthymus DNA (CT DNA) were studied by absorption spectra and DNA melting temperature measurements.Tyr-HB and Trp-HB distinguish themselves from Gly-HB and HB remarkably by their significantly improvedefficiencies to generate semiquinone anion radicals, superoxide anion radicals, and hydroxyl radicals, as wellas their affinity to CT DNA, as the result of the electron-donating properties and intercalating abilities oftyrosine and tryptophan groups. Tyr-HB and Trp-HB show remarkably enhanced photodamage capabilitieson CT DNA than their parent HB in aerobic conditions. Moreover, they possess moderate photodamageabilities on CT DNA even in anaerobic conditions, indicating the role of Type I mechanism in theirphotodynamic behaviors.
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