研究目的
To study the effects of L-ascorbic acid (AA), 3-O-ethyl-L-ascorbic acid (3-EtAA), and Trolox (TX) on the photosensitized singlet oxygen generation by riboflavin (RF) in phosphate buffer (pH 6.8) at room temperature, and to determine the mechanisms of suppression through quenching of excited states.
研究成果
The suppression of RF-photosensitized singlet oxygen generation by AA, 3-EtAA, and TX is primarily due to quenching of the triplet state of RF, with minor contributions from singlet state quenching. AA and TX are more effective than 3-EtAA. The findings suggest these antioxidants could mitigate singlet oxygen-induced damage in biological contexts, with implications for skin and eye health.
研究不足
The study is limited to phosphate buffer solutions at pH 6.8 and room temperature; results may not generalize to other conditions or biological systems. The use of specific chemicals and concentrations might not cover all possible scenarios. Potential areas for optimization include extending to varied pH, temperatures, or additional quenchers.
1：Experimental Design and Method Selection:
The study involved measuring time profiles of near-infrared phosphorescence of singlet oxygen generated by RF, using laser excitation at 355 nm. Fluorescence and transient absorption measurements were conducted to determine quenching rate constants. The experiments were designed to assess the suppression of singlet oxygen generation by AA, 3-EtAA, and TX.
2：Sample Selection and Data Sources:
Sample solutions were prepared in phosphate buffer (pH 6.8) at 25°C, using chemicals such as RF, AA, 3-EtAA, TX, and NA without further purification. Concentrations were specified, e.g., 0.1 mmol dm?3 RF and 0.4 mmol dm?3 quenchers.
3：8) at 25°C, using chemicals such as RF, AA, 3-EtAA, TX, and NA without further purification. Concentrations were specified, e.g., 1 mmol dm?3 RF and 4 mmol dm?3 quenchers.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment included a Continuum Surelite Nd:YAG laser (355 nm, 10 Hz repetition rate), UV absorption spectrometer, transient absorption setup, fluorescence lifetime measurement system, and near-IR phosphorescence detector. Materials included RF (TCI GR Grade), AA (FUJIFILM Wako GR Grade), 3-EtAA (TCI), TX (TCI), NA (TCI), acetonitrile (FUJIFILM Wako GR Grade), and phosphate buffer solution (FUJIFILM Wako).
4：Experimental Procedures and Operational Workflow:
Samples were excited with the laser, and time-resolved measurements were performed. For phosphorescence, intensities were monitored at specific wavelengths (e.g., 1274 nm), with background subtraction. Transient absorption was measured at 690 nm. Fluorescence lifetimes were determined in air-saturated solutions. Each measurement averaged 512 laser shots to avoid photodecomposition.
5：Data Analysis Methods:
Data were analyzed using Stern-Volmer equations to calculate bimolecular rate constants for quenching. Computer simulations were used to model time profiles of phosphorescence intensity. Statistical analysis involved plotting and fitting data to determine constants.
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