Photocleavage of plasmid pBR322 DNA by some anionic porphyrins

✍ Scribed by Shampa R. Chatterjee; T. S. Srivastava; J. P. Kamat; T. P. A. Devasagayam

• Book ID: 102659368
• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 756 KB
• Volume: 02
• Category: Article
• ISSN: 1088-4246
• DOI: 10.1002/(sici)1099-1409(199807/10)2:4/5<337::aid-jpp80>3.0.co;2-l

✦ Synopsis

The water-soluble porphyrins meso-tetrakis [4-(carboxymethyleneoxy)phenyl]porphyrin (H 2 T4CPP), meso-tetrakis [3-(carboxymethyleneoxy)phenyl]porphyrin (H 2 T3CPP) and meso-tetrakis [3,4bis(carboxymethyleneoxy)phenyl]porphyrin (H 2 T3,4BCPP) cleave plasmid pBR322 DNA to single-strand breaks (SSBs) in the presence of molecular oxygen and visible light. These porphyrins induced SSBs in DNA as a function of irradiation time as well as porphyrin concentration. Under similar conditions (10 mM or more), H 2 T3CPP showed more SSBs in DNA than the porphyrins H 2 T4CPP and H 2 T3,4BCPP. The DNA cleavage was more in D 2 O-based buffer than in H 2 O buffer. In addition, this DNA cleavage was inhibited by the presence of sodium azide and lipoic acid, which are potent quenchers of singlet oxygen ( 1 O 2 ). These observations suggest the involvement of 1 O 2 in photocleavage of DNA. Further, the DNA cleavage, to a limited extent, was also inhibited by tert-butanol and mannitol, both quenchers of hydroxyl radical ( . OH), suggesting the involvement of . OH in photocleavage of DNA. Thus both 1 O 2 and . OH are involved in photocleavage of plasmid DNA by these porphyrins.