title: Chemiexcitation in the arachidonic acid cascade.
abstract: As investigated in neutrophils, the very weak luminescence accompanying the arachidonic acid cascade is associated with the lipoxygenase pathway. The emission is dramatically enhanced by energy transfer to chlorophyll a. The number of chlorophyll molecules excited to the fluorescent state per oxygen consumed, (the S1/O2 ratio), equal to the product of the quantum yields of chemiexcitation and of energy transfer, is 5.4 x 10(-6). The quantum yield of chemiexcitation is inferred to be higher than 1 x 10(-3). The two most likely chemiexcitation routes point to triplet conjugated carbonyls as the most likely candidates for the excited species that transfer to chlorophyll. As such the emission intensity may reflect the level of hydroperoxyeicosatetraenoic acid. This is the first case where addition of a biotic substrate to a cellular system results in substantial generation of electronic excited states without any drastic loss of cell viability. Whether the formation of excited states in the arachidonic acid cascade in neutrophils is accidental or has a biological role is an open question.
authors.affiliation: Departamento de Bioquimica, Universidade de São Paulo, Brasil.
authors.forename: A L
authors.initials: AL
authors.lastname: Nascimento
authors.forename: G
authors.initials: G
authors.lastname: Cilento
mesh_terms: D000818:Animals; D001095:Arachidonic Acids / Q000097:blood*; D002734:Chlorophyll; D000077194:Chlorophyll A; D007202:Indicators and Reagents; D007700:Kinetics; D008084:Lipoxygenase / Q000097:blood; D049449:Luminescence; D009504:Neutrophils / Q000502:physiology*; D010101:Oxygen Consumption; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D001095:Arachidonic Acids; D007202:Indicators and Reagents; D002734:Chlorophyll; D008084:Lipoxygenase; D000077194:Chlorophyll A