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Possible use of Thioflavin T based fluorescent molecular rotors as temperature sensors was assessed in this work. Fluorescent properties of Thioflavin T and its derivative 6-Me-BTA-2C in 99% glycerol were studied using steady-state and time-resolved fluorescence spectroscopy methods. For Thioflavin T in glycerol it has been found that temperature growth from 261 to 353 K results in ~3 orders of magnitude increase of non-radiative decay rate constant knr for the excited state of the molecule. Fluorescence decay studies by time-correlated single photon counting method showed that fluorescence decay kinetics of Thioflavin T in glycerol can be used for temperature measurements in the range 260–290 K. For 6-Me-BTA-2C molecule the range of the maximal sensitivity was shifted to higher temperatures (280–320 K). The obtained results about fluorescent properties and decay kinetics of Thioflavin T based dyes in highly viscous media can be used to develop nanoscale temperature sensors. [ABSTRACT FROM AUTHOR]

New fluorescent molecular rotors (FMRs) were developed by modification of the Thioflavin T (ThT) structure via introduction of methyl and methoxy groups. Effects of the substituents on fluorescence properties and twisted intramolecular charge transfer (TICT) rate in the excited state of the molecules were studied using steady-state fluorescence and time-resolved absorption spectroscopy. Quantum chemical calculations of the molecules in the ground and excited states were carried out to aid interpretation of the experimental results. Only cationic forms of ThT derivatives have FMR properties and exhibit viscosity-dependent fluorescence. The TICT rate was found to be affected by the size of the molecular fragments, which experience mutual rotation, dihedral angle φ between the fragments in the ground state as well as their donor/acceptor properties. [ABSTRACT FROM AUTHOR]

It was found that the spectral and fluorescent properties of BTA-1C cation in protic and aprotic solvents differ. It was shown that for solutions in long-chain alcohols viscosity is the main factor that determines the dynamics of intramolecular charge transfer in the excited state of the BTA-1C molecule. In the case of aprotic solvents a correlation was found between the rate constant of twisted intramolecular charge transfer (TICT) during rotation of fragments of the molecule in relation to each other in the excited state and the solvent relaxation rate: kTICT ~ 1/τS. [ABSTRACT FROM AUTHOR]

The nitration of tyrosyl residues in proteins is considered a type of post-translational modification of proteins, indicating disruptions in the metabolic and signaling functions of nitric oxide •NO and the development of oxidative nitrosative stress. We have examined the nonenzymatic pathway of protein nitration by the action of visible light in the presence of riboflavin and nitrite. Mass spectrometry was used to show that riboflavin-photosensitized redox processes involving nitrite and tyrosine or tyrosyl residues lead to nitration of residues Tyr-103 and Tyr-146 in the polypeptide chain of horse heart myoglobin. A possible role is discussed for riboflavin and other natural photosensitizers in the modification and damage of proteins when the body is exposed to intense visible light in the presence of nitrites in the blood. [ABSTRACT FROM AUTHOR]

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. A reversible modulation of QDs emission intensity which correlates with magnitude of transient photoinduced absorption band of the diarylethenes during photochromic transformations has been demonstrated. [ABSTRACT FROM AUTHOR]