title: Quenching of the fluorescence of aromatic pterins by deoxynucleotides.
abstract: Steady-state and time-resolved studies of the fluorescence of four aromatic unconjugated pterins (pterin (Ptr), 6-(hydroxymethyl)pterin (Hmp), 6-methylpterin (Mep), and 6,7-dimethylpterin (Dmp)) in aqueous solutions in the presence of different nucleotides (2'-deoxyguanosine 5'-monophosphate (dGMP), 2'-deoxyadenosine 5'-monophosphate (dAMP), and 2'-deoxycytosine 5'-monophosphate (dCMP)) have been performed using the single-photon counting technique. The singlet excited states of acid forms of pterins are deactivated by purine nucleotides (dGMP and dAMP) via a combination of dynamic and static processes. The efficiency of the dynamic quenching is high, independently of the nature of the purine base of the nucleotide and of the chemical structure of the substituents linked to the pterin moiety. Analysis of the static quenching indicates that ground-state association between pterins and purine nucleotides takes place, but the formation of the corresponding complexes is significant only at relatively high reactant concentrations. The quenching of the fluorescence of acid forms of pterin derivatives by dCMP, a pyrimidine nucleotide, is slightly less efficient than the quenching by purine nucleotides and is purely dynamic. In alkaline media, the fluorescence quenching is much less efficient than in acidic media, the deactivation by purine nucleotides being purely dynamic, whereas quenching by dCMP is negligible. Possible mechanisms for the quenching of fluorescence of pterin derivatives by the different nucleotides are discussed.
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CCT La Plata-CONICET, Boulevard 113 y 64, 1900 La Plata, Argentina.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Petroselli
authors.forename: M Laura
authors.initials: ML
authors.lastname: Dántola
authors.forename: Franco M
authors.initials: FM
authors.lastname: Cabrerizo
authors.forename: Carolina
authors.initials: C
authors.lastname: Lorente
authors.forename: André M
authors.initials: AM
authors.lastname: Braun
authors.forename: Esther
authors.initials: E
authors.lastname: Oliveros
authors.forename: Andrés H
authors.initials: AH
authors.lastname: Thomas
mesh_terms: D003838:Deoxyadenine Nucleotides / Q000737:chemistry; D003843:Deoxycytidine Monophosphate / Q000737:chemistry; D003848:Deoxyguanine Nucleotides / Q000737:chemistry; D003854:Deoxyribonucleotides / Q000737:chemistry*; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D015394:Molecular Structure; D011622:Pterins / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
chemical_list: D003838:Deoxyadenine Nucleotides; D003848:Deoxyguanine Nucleotides; D003854:Deoxyribonucleotides; D011622:Pterins; D014867:Water; D003843:Deoxycytidine Monophosphate; C012873:2'-deoxy-5'-adenosine monophosphate; C007257:2'-deoxyguanosine 5'-phosphate