Abstract: Combining supramolecular chemistry with biochemistry was a new research direction. In this paper, self-assembly between a host compound CB[8] with a guest molecule benzyl viologen(BEV) was examined by UV absorption measurement, cyclic voltammetric method and ¹H NMR technique. The experimental results revealed that CB[8] included benzyl and part of pyridinum of BEV to form binary compounds BEV-CB[8], and when BEV²⁺ was reduced to BEV^+·, a new stable ternary complex (BEV^+·)₂/CB[8] would be formed. The two kinds of viologens, BEV and BEV-CB[8], were used for DNA photocleavage stu-dies in physiological environment following the research results that CB[8] could enhance the interaction between BEV and CT DNA with intercalation and electrostatic interaction. Only 50 μmol/L of the complex BEV-CB[8] could cleave SC pBR 322 DNA completely compared with BEV, which showed no ability for DNA clea-vage under the irradiation of Xe lamp. The main reason was that BEV²⁺ was reduced to BEV^+· under irradiation and CB[8] bound BEV^+· tightly to form (BEV^+·)₂/CB[8], which prolonged the lifetime of viologen radical BEV^+·, causing the dissolved oxygen in water activation and the reactive oxygen species, · OH and O₂^-·, could cleave SC pBR 322 DNA. The results indicate an important application by host molecule CB in supramolecular chemistry, which gives an obviously evidence for the field of DNA cleavage.

Key words: Cucurbit[8]uril, Viologen, Supramolecular self-assembly, DNA photocleavage