Solvent effect on excited state potential energy surfaces of Thioflavin T. Qualitatively different results by TDDFT and SA-2-CASSCF methods.

Thioflavin T (ThT) is a viscosity-sensitive fluorescent dye and its emission intensity undergoes a significant enhancement upon binding to DNA or amyloid fibrils. This fluorescence light-up feature has been attributed earlier to restriction of structural rearrangements in the excited state that are coupled to an intramolecular charge transfer (ICT) reaction. In this work TDDFT (using B3LYP and CAM-B3LYP functionals) and SA-2-CASSCF calculations were carried out to obtain relaxed excited-state potential energy surfaces (PES) along twisting φ and wagging δ angles that describe mutual orientation of benzothiazole (BTZ) and dimethylaniline (DMA) fragments in ThT.

Photoinduced Reversible Modulation of Fluorescence of CdSe/ZnS Quantum Dots in Solutions with Diarylethenes.

Steady-state absorption and fluorescence spectra, fluorescence decay kinetics of CdSe/ZnS quantum dots (QD) with photochromic diarylethenes (DAE) in toluene have been studied. Two kinds of QDs emitting at 525 and 600 nm were investigated and DAE were selected to ensure good overlap of their photoinduced absorption band with QDs emission spectra. It has been found that photochromic molecules form complexes with QD which results in partial fluorescence quenching.

Photochromic systems with photoinduced emission modulation of colloidal CdSe quantum wells.

A spectroscopic study of photochromic systems containing two-dimensional CdSe nanoparticles (colloidal quantum wells) and photochromic compounds of the thermally relaxing chromene and thermally irreversible diarylethene classes in solutions was carried out. First, the systems were found to exhibit modulation of emission of two-dimensional nanoparticles in accordance with the photochromic transformations of compounds due to Förster resonance energy transfer (FRET) from the two-dimensional nanoparticles to photoinduced photochromic isomers.

S-Nitrosoglutathione formation at gastric pH is augmented by ascorbic acid and by the antioxidant vitamin complex, Resiston.

Context: Exogenous nitrogen oxides must be made bioavailable to sustain normal physiology because nitric oxide synthase (NOS) deficient mice are viable. In the stomach, S-nitrosoglutathione (GSNO) is formed from ingested nitrite and high levels of airway glutathione (GSH) that are cleared and swallowed. However, gastric GSNO may be broken down by nutrients like ascorbic acid (AA) before it is absorbed.

Solvent Polarity Effect on Nonradiative Decay Rate of Thioflavin T.

It has been established earlier that fluorescence quantum yield of thioflavin T (ThT)-a probe widely used for amyloid fibrils detection-is viscosity-dependent, and photophysical properties of ThT can be well-described by the fluorescent molecular rotor model, which associates twisted internal charge transfer (TICT) reaction with the main nonradiative decay process in the excited state of the dye. Solutions of ThT in a range of polar solvents were studied using steady-state fluorescence and sub-picosecond transient absorption spectroscopy methods, and we showed that solvent effect on nonradiative transition rate knr cannot be reduced to the dependence on viscosity only and that ∼3 times change of knr can be observed for ThT in aprotic solvents and water, which correlates with solvent polarity. Different behavior was observed in alcohol solutions, particularly in longer n-alcohols, where TICT rate was mainly determined by rotational diffusion of ThT fragments.