Abstract
Six new organoplatinum complexes (4b–g) were synthesized by addition of sodium 2-mercaptopyridine N-oxide and various sulfoxides to K2PtCl4 in DMF and H2O (1:5) at room temperature. To realize the role of sulfoxide ligand in the platinum (II) organometallic compounds, we carried out time-dependence NMR study of 4b in CDCl3 upon photolysis with 350-nm UV light. The results were compared with those of compound 4a.Irradiation with UV light (350 nm) of organoplatinum complexes 4a–f in a phosphate buffer (pH = 5.0–8.0) containing the supercoiled circular □X174 RFI DNA (form I; 50 □M/base pair) under aerobic conditions for 2.0 h resulted in the single-strand scission of the DNA. These results indicate that the organoplatinum complexes 4a–f functioned as DNA cleavers. Among all of the new organoplatinum complexes, PtCl(n-Bu2SO)[□2-C5H4SN(O)] (4b) exhibited the greatest DNA cleaving efficiency. The ratio of (form II)/(form I) for 4b was 1.0 at the concentration as low as 9.6 □M. Results from control experiments indicate that UV light was essential and functioned as a "trigger" to initiate the DNA cleavage processes.