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Reactivity of Conjugated and Unconjugated Pterins with Singlet Oxygen (O 2 ( 1 Δ g )): Physical Quenching and Chemical Reaction †
Author(s) -
Cabrerizo Franco M.,
Laura Dántola M.,
Petroselli Gabriela,
Capparelli Alberto L.,
Thomas Andrés H.,
Braun André M.,
Lorente Carolina,
Oliveros Esther
Publication year - 2007
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/2006-09-15-ra-1041
Subject(s) - singlet oxygen , reactivity (psychology) , quenching (fluorescence) , conjugated system , chemistry , photochemistry , singlet state , oxygen , organic chemistry , excited state , polymer , fluorescence , physics , atomic physics , pathology , quantum mechanics , medicine , alternative medicine
Pterins (PTs) belong to a class of heterocyclic compounds present in a wide range of living systems. They participate in relevant biological functions and are involved in different photobiological processes. We have investigated the reactivity of conjugated PTs (folic acid [FA], 10‐methylfolic acid [MFA], pteroic acid [PA]) and unconjugated PTs (PT, 6‐hydroxymethylpterin [HPT], 6‐methylpterin [MPT], 6,7‐dimethylpterin [DPT], rhamnopterin [RPT]) with singlet oxygen ( 1 O 2 ) in aqueous solutions, and compared the efficiencies of chemical reaction and physical quenching. The chemical reactions between 1 O 2 , produced by photosensitization, and PT derivatives were followed by UV‐visible spectrophotometry and high‐performance liquid chromatography, and corresponding rate constants ( k r ) were evaluated. Whenever possible, products were identified and quantified. Rate constants of 1 O 2 total quenching by the PT derivatives investigated were obtained from steady‐state 1 O 2 luminescence measurements. Results show that the behavior of conjugated PTs differs considerably from that of unconjugated derivatives, and the mechanisms of 1 O 2 physical quenching by these compounds and of their chemical reaction with 1 O 2 are discussed in relation to their structural features.