Uric Acid: A Less‐than‐Perfect Probe for Singlet Oxygen

Abstract

Uric acid and/or its monoanion has long been used as chemical-trapping agents to demonstrate the presence of singlet oxygen, O (a Δ ), in aqueous systems. "Oxidative bleaching" of uric acid, generally monitored through changes in the uric acid absorption spectrum, is often used in support of claims for the intermediacy of O (a Δ ). The bleaching of uric acid has also been used to quantify photosensitized O (a Δ ) yields in selected systems. Unfortunately, experiments performed to these ends often neglect processes and phenomena that can influence the results obtained. For the present study, we experimentally examined the behavior of uric acid under a variety of conditions relevant to the photoinitiated creation and subsequent removal of O (a Δ ). Although the oxidative destruction of uric acid can indeed be a useful tool in some cases, we conclude that caution must be exercised such as not to incorrectly interpret the data obtained.

Double-Stranded DNA Matrix for Photosensitization Switching

“…The S 1 molecular orbitals and electronic structures of SG under various dihedral angles were further calculated with TD-DFT. 37 As shown in Figure 3b, Supporting Information Figures S15 and S16, increasing the dihedral angle (0-90°) results in increases of the SOC constants (ξ) and decrease of the singlet−triplet energy gap (ΔE ST ), which is consistent with previous works. [30][31][32] However, the oscillator strength of SG at 90°is nearly zero, which is not feasible for the whole transition.…”

Edaravone, a scavenger for multiple reactive oxygen species, reacts with singlet oxygen to yield 2-oxo-3-(phenylhydrazono)-butanoic acid

“…The ratios of rate constants of edaravone to those of references (k E /k R ) were calculated and are summarized in Table 1. Considering the rate constants of the references, (11)(12)(13)(14)(15)(16) the rate constant of edaravone was estimated on the order of 10 8 -10 9 M −1 s −1 . Moreover, the k E /k R values were much reduced in 50% methanol (Table 1), suggesting that the reactivity of edaravone anions to 1 O 2 is much greater than that of edaravone non-ions.…”

“…UA 1.76 ± 0.02 1.5 × 10 8 (11,12) 0.08 ± 0.01 His 10.0 ± 0.5 7.0 × 10 7 (13) 0.56 ± 0.02 0.7 × 10 7 (16) Met 10.5 ± 0.2 2.2 × 10 7 (14) 0.84 ± 0.01 0.5 × 10 7 (16) Trp 31.0 ± 2.2 3.4 × 10 7 (15) 1.41 ± 0.02 0.4 × 10 Product of 1 O 2 -induced oxidation of edaravone. In order to identify the oxidation product of edaravone induced by 1 O 2 , photooxidation of edaravone was conducted.…”

Antibacterial Nanoparticles with Natural Photosensitizers Extracted from Spinach Leaves

“…A linear increase in the I 3 – concentration (following the UV/vis absorbance change at 287 or 351 nm) proportional to the generation of O 2 ( 1 Δ g ) was found (Figure S11 in Supporting Information). Alternatively, O 2 ( 1 Δ g ) photogeneration was confirmed by photodegradation of uric acid at 293 nm (Figure S12 in Supporting Information). The experimental data indicate that oxidation of both I – and uric acid substrates is due to oxidation by O 2 ( 1 Δ g ) for several reasons: a) formation of O 2 ( 1 Δ g ) was confirmed from luminescence measurement (see photophysical measurements above), (b) the oxidation did not take place in inert gas-saturated samples and/or in aerated samples in the dark, and (c) a strong physical quencher of singlet oxygen (sodium azide) inhibited oxidation of both substrates.…”