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Photophysical and Photochemical Properties of 3‐methylpterin as a New and More Stable Pterin‐type Photosensitizer
Author(s) -
Estébanez Sandra,
Lorente Carolina,
Kaufman Teodoro S.,
Larghi Enrique L.,
Thomas Andrés H.,
Serrano Mariana P.
Publication year - 2018
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 - 10.1111/php.12931
Subject(s) - pterin , chemistry , photochemistry , photosensitizer , singlet oxygen , moiety , aqueous solution , tautomer , fluorescence , oxygen , stereochemistry , organic chemistry , cofactor , physics , quantum mechanics , enzyme
Pterin derivatives are heterocyclic compounds which are present in different biological systems. Neutral aqueous solutions of pterins present acid–base and keto–enol equilibria. These compounds, under UV ‐A radiation fluoresce, undergo photooxidation, generate reactive oxygen species and photoinduce the oxidation of biological substrates. As photosensitizers, they may act through different mechanisms, mainly through an electron transfer‐initiated process (type‐I mechanism), but they also produce singlet molecular oxygen ( 1 O 2 ) upon irradiation (type‐ II mechanism). In general, upon UV ‐A excitation two triplet states, corresponding to the lactim and lactam tautomers, are formed, but only the last one is the responsible for the photosensitized reactions of biomolecules. We present a study of the photochemical properties of 3‐methylpterin (3‐Mep) which, in contrast to most pterin derivatives, exists only in the lactam form. Also an improvement in the synthesis of 3‐Mep is reported. The spectroscopic properties 3‐Mep in aqueous solution were similar to those of the unsubstituted pterin derivative (Ptr) in its acid form, such as absorption, fluorescent and phosphorescent emission spectra. Experiments using 2′‐deoxyguanosine 5′‐monophosphate ( dGMP ) as oxidizable target demonstrated that methylation at C‐3 position of the pterin moiety does not affect significantly the efficiency of photosensitization, but results in a more photostable sensitizer.