Singlet oxygen (1Δg) production by pterin derivatives in aqueous solutions

Abstract

Six compounds of the pterin family (pterin, 6-carboxypterin, 6-formylpterin, folic acid, biopterin and neopterin) have been investigated for their efficiencies of singlet oxygen (O2(1deltag)) production and quenching in aqueous solutions. The quantum yields of 1O2 production (phidelta) have been determined by measurements of the 1O2 luminescence in the near-infrared (1270 nm) upon continuous excitation of the sensitizer. Under our experimental conditions, all studied compounds (except folic acid) are relatively efficient 1O2 sensitizers with phidelta values of up to 0.47. Results show that the nature of the substituent at position 6 on the pterin moiety, as well as the pH, affect considerably the capacity of pterins to produce 1O2. All compounds investigated are efficient 1O2 quenchers: the rate constant of 1O2 total quenching (kt) by folic acid (3.0(+/- 0.3) x 10(7) M(-1) s(-1)) is one order of magnitude larger than those for the other pterin derivatives investigated (1.4(+/- 0.1) x 10(6) M(-1) s(-1) to 2.9(+/- 0.3) x 10(6) M(-1) s(-1)).

Photooxidation of Pterin in Aqueous Solutions: Biological and Biomedical Implications

“…Values of the quantum yields of 1 O 2 production (F D ) for the acidic and basic forms of PT were already reported as 0.18 (AE 0.02) and 0.30 (AE 0.02), respectively [15]. In addition, a value of 2.9 (AE 0.3) Â 10 6 l mol À1 s À1 was determined for the rate constant of total 1 O 2 quenching (k t k r k q ) by PT in alkaline medium [15].…”

“…The role of molecular O 2 in the mechanisms of the photochemical reactions is analyzed, and the capability of PT to yield reactive oxygen species (ROS) is discussed. In particular, we have followed the production of H 2 O 2 during the photooxidation of PT, and we have studied the reaction between PT and 1 O 2 , the latter species being generated by PT itself under irradiation [15]. The role of this ROS in the photooxidation of PT is discussed.…”

Theoretical Study on the Relative Energies of Neutral Pterin Tautomers

“…Under UV-A irradiation, the excited pterins may undergo photooxidation besides fluorescence emission. Pterins, chiefly 6-carboxy pterin, have been shown to photosensitize DNA damage by both type I (electron transfer) and type II (singlet oxygen) mechanisms (19)(20)(21)(22). Despite their important contribution, the electronic and geometrical features of related low-lying states as well as the explicit mechanism of photochemistry and photophysics of pterins are still unclear.…”

Effects of Injectable Propofol Emulsion on Singlet Oxygen Released From Activated Human Neutrophils and That Chemically Generated

“…Pterin derivatives, such as pterin-6-carboxylic acid, produce 1 O 2 under UV-A radiation (7). EPR spectroscopy was used with 4-oxo-TEMP, which reacts with 1 O 2 and produces a stable nitroxide radical, 2,2,6,6- …”