title: Generation of electronically excited triplet species at the cellular level: a potential source of genotoxicity.
abstract: Selected enzymatic systems can efficiently produce a product in the electronically excited triplet state. Earlier, only the formation of electronically excited singlet species was known. The formation of triplet species has been demonstrated with both normal substrates/metabolites and with xenobiotics, even at the cellular level. Triplet excited species have intrinsically much longer lifetimes than excited singlets, whereby they can be potentially important agents for normal and/or deleterious processes, including mutagenesis. Enzymically generated triplet species can damage DNA, even when protein coated, as in the case of the lambda-phage of Escherichia coli. Some evidence of damage by triplet species has also been reported for intact cells. Triplet excited species may produce their effects through type I and/or type II dark photosensitization, that is, the events may be started by H abstraction and/or singlet oxygen/superoxide ion production. The induction of lipid peroxidation, with concomitant clastogenic effects, appears to be of special importance.
authors.affiliation: Department of Biochemistry, Universidade de São Paulo, Brazil.
authors.forename: G
authors.initials: G
authors.lastname: Cilento
authors.forename: A L
authors.initials: AL
authors.lastname: Nascimento
mesh_terms: D000079:Acetaldehyde / Q000031:analogs & derivatives / Q000494:pharmacology; D000447:Aldehydes / Q000494:pharmacology; D016718:Arachidonic Acid / Q000494:pharmacology; D004247:DNA / Q000187:drug effects*; D004563:Electrochemistry; D066298:In Vitro Techniques; D007210:Indoleacetic Acids / Q000494:pharmacology; D009153:Mutagens / Q000494:pharmacology*; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction; D014297:Trimethylsilyl Compounds / Q000494:pharmacology
chemical_list: D000447:Aldehydes; D007210:Indoleacetic Acids; D009153:Mutagens; D014297:Trimethylsilyl Compounds; D016718:Arachidonic Acid; C055300:isobutyraldehyde trimethylsilyl enol ether; C070971:indole-3-acetic acid ethyl ester; D004247:DNA; C017439:isobutyraldehyde; D000079:Acetaldehyde; C013192:phenylacetaldehyde