Fluorescence and absorption of rhodamine 6G solutions as pressure standards for a diamond-anvil cell.

The absorption and fluorescence spectra of rhodamine 6G (R6G) dissolved in water, methanol, ethanol and isopropanol have been applied to calibrate the pressure in a diamond anvil cell (DAC). Owing to the strong initially nearly linear temperature-independent bathochromic shift of 7 nm GPa found in absorption and emission bands for methanol R6G solutions, they are ideal for precise pressure calibration to over 3.4 GPa, when methanol freezes.

Tetramethylalloxazines as efficient singlet oxygen photosensitizers and potential redox-sensitive agents.

Tetramethylalloxazines (TMeAll) have been found to have a high quantum yield of singlet oxygen generation when used as photosensitizers. Their electronic structure and transition energies (S → S, S → T, T → T) were calculated using DFT and TD-DFT methods and compared to experimental absorption spectra. Generally, TMeAll display an energy diagram similar to other derivatives belonging to the alloxazine class of compounds, namely π,π* transitions are accompanied by closely located n,π* transitions.

5-Deazaalloxazine as photosensitizer of singlet oxygen and potential redox-sensitive agent.

Flavins are a unique class of compounds that combine the features of singlet oxygen generators and redox-dependent fluorophores. From a broad family of flavin derivatives, deazaalloxazines are significantly underdeveloped from the point of view of photophysical properties. Herein, we report photophysics of 5-deazaalloxazine (1a) in water, acetonitrile, and some other solvents.

Photophysical properties of alloxazine derivatives with extended aromaticity - Potential redox-sensitive fluorescent probe.

The spectral and photophysical properties of two four-ring alloxazine derivatives, naphtho[2,3-g]pteridine-2,4(1H,3H)-dione (1a) and 1,3-dimethylnaphtho[2,3-g]pteridine-2,4(1H,3H)-dione, (1b) were studied. The propensity of 1a for excited-state proton transfer reactions in the presence of acetic acid as a catalyst was also studied, showing no signature of the reaction occurring. In addition, quenching of 1a fluorescence by acetic acid was investigated.

Quantification of 5-methyl-2'-deoxycytidine in the DNA.

Methylation at position 5 of cytosine (Cyt) at the CpG sequences leading to formation of 5-methyl-cytosine (m(5)Cyt) is an important element of epigenetic regulation of gene expression. Modification of the normal methylation pattern, unique to each organism, leads to the development of pathological processes and diseases, including cancer. Therefore, quantification of the DNA methylation and analysis of changes in the methylation pattern is very important from a practical point of view and can be used for diagnostic purposes, as well as monitoring of the treatment progress.

Photochemistry of riboflavin derivatives in methanolic solutions.

Light-induced degradation of the riboflavin derivatives is reported, including 5-deaza-riboflavin, iso-6,7-riboflavin, 3-methyl-tetra-acetyl-riboflavin (3MeTARF), and 3-benzyl-lumiflavin. The studied compounds undergo photolytic processes with considerable quantum yields in methanolic solutions (φ ≈ 10(-3)-10(-4) mol einst(-1)). Photolysis in anaerobic conditions is more efficient than that in the presence of oxygen.