title: Substituent effects on the photophysical properties of pterin derivatives in acidic and alkaline aqueous solutions.
abstract: Pterins are heterocyclic compounds with important biological functions, and most of them may exist in two acid-base forms in the pH range between 3 and 13 in aqueous solution. In this work, the photophysical properties of acid and basic forms of six compounds of the pterin family (6-hydroxymethylpterin [HPT], 6-methylpterin [MPT], 6,7-dimethylpterin [DPT], rhamnopterin [RPT], N-methylfolic acid [MFA], and pteroic acid [PA]) have been studied. The effects of the chemical nature of the substituents at position 6 of the pterin moiety and the effects of the pH on the absorption and emission properties are analyzed. The fluorescence characteristics (spectra, quantum yields, lifetimes) of these compounds have been investigated using the single-photon-counting technique. Results obtained for pterin derivatives containing small substituents with 1 carbon atom (HPT, MPT, DPT) and short hydrocarbon chain (4 carbon atoms) (RPT) are different from those found for pterin derivatives containing a p-aminobenzoic acid (PABA) moiety in the substituent (MFA and PA). Fluorescence quantum yields (Phi(F)) of the first group of compounds are relatively high (>/=0.4), whereas MFA and PA exhibit very small Phi(F) values (</=0.01).
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata, Casilla de Correo 16, Sucursal 4 (1900) La Plata, Argentina.
authors.forename: Franco M
authors.initials: FM
authors.lastname: Cabrerizo
authors.forename: Gabriela
authors.initials: G
authors.lastname: Petroselli
authors.forename: Carolina
authors.initials: C
authors.lastname: Lorente
authors.forename: Alberto L
authors.initials: AL
authors.lastname: Capparelli
authors.forename: Andrés H
authors.initials: AH
authors.lastname: Thomas
authors.forename: André M
authors.initials: AM
authors.lastname: Braun
authors.forename: Esther
authors.initials: E
authors.lastname: Oliveros
mesh_terms: D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D010777:Photochemistry; D011622:Pterins / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D011622:Pterins; D012996:Solutions; D014867:Water