title: Photochemistry of quinolylmethylisothioronium salts. Guanine selective DNA photocleavage reagents.
abstract: Quinolylmethylisothioronium salts (1a and 4a) cleave DNA upon irradiation. The cleavage is more than 10-fold enhanced by piperidine treatment and subsequently shows a high preference for guanines. Photolysis of 1a, 2a and 4a in water at lambda greater than 300 nm resulted in photoheterolysis. Irradiation of 1a in 2-propanol gave only products from photohomolysis, irradiation of 1a in methanol and 2a and 4a in 2-propanol resulted in products from both photoheterolysis and photohomolysis. Quantum yields for the disappearance of 1a in water and 2-propanol were determined. The presence or absence of oxygen had no effect in water, whereas oxidation products were observed upon irradiation in methanol and 2-propanol in the presence of oxygen. The guanine specific DNA photoreaction is proposed to take place by alkylation at N7 via the quinolylmethyl carbocation and thus to represent a photoalkylation.
authors.affiliation: Research Center for Medical Biotechnology, H.C. Orsted Institute, University of Copenhagen, Denmark.
authors.forename: U
authors.initials: U
authors.lastname: Henriksen
authors.forename: C
authors.initials: C
authors.lastname: Larsen
authors.forename: G
authors.initials: G
authors.lastname: Karup
authors.forename: C
authors.initials: C
authors.lastname: Jeppesen
authors.forename: P E
authors.initials: PE
authors.lastname: Nielsen
authors.forename: O
authors.initials: O
authors.lastname: Buchardt
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000528:radiation effects*; D006147:Guanine; D007202:Indicators and Reagents; D007550:Isothiuronium / Q000031:analogs & derivatives*; D008969:Molecular Sequence Data; D010777:Photochemistry; D010957:Plasmids / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D007202:Indicators and Reagents; D007550:Isothiuronium; D006147:Guanine; D004247:DNA