The red‐edge effects: 30 years of exploration

Abstract

In 1970, three laboratories independently made a discovery that, for aromatic fluorophores embedded into different rigid and highly viscous media, the spectroscopic properties do not conform to classical rules. The fluorescence spectra can depend on excitation wavelength, and the excited-state energy transfer, if present, fails at the "red" excitation edge. These red-edge effects were related to the existence of excited-state distribution of fluorophores on their interaction energy with the environment and the slow rate of dielectric relaxation of this environment. In these conditions the site-selection can be provided by variation of the energy of illuminating light quanta, and the behaviour of selected species can be followed as a function of time and other variables. These observations found extensive application in different areas of research: colloid and polymer science, molecular biophysics, photochemistry and photobiology. In particular, they led to the development of very productive methods of studying the dynamics of dielectric relaxations in protein and membranes, using the tryptophan emission and the emission of a variety of probes. These studies were extended to the time domain with the observation of new site-selective effects in emission intensity and anisotropy decays. They stimulated the emergence and development of cryogenic energy-selective and single-molecular techniques that became valuable tools in their own right in chemistry and biophysics research. Site-selection effects were discovered for electron-transfer and proton-transfer reactions if they depended on the dynamics of the environment. This review is focused on the progress in the field of red-edge effects, their applications and prospects.

Polarity Assessment of Thermoresponsive Poly(NIPAM-co-NtBA) Copolymer Films Using Fluorescence Methods

“…A similar effect was observed in the parent 3-hydroxyflavones in protic solvents where solvent hydrogen bonding with the dye may increase the activation energy barrier to ESIPT [46][47]. In this case, ESIPT is irreversible and is characterized by the fact that the average lifetime of the T* band is longer than that for the N* band [43][44]. The highest degree of ESIPT non-equilibration seems to occur in MFE doped copolymers where the difference in average lifetime (∆τ ) is ≈ 1.6 ns (Table 1), while the BFE doped copolymers have a much lower ∆τ of ≈ 0.4 ns) ( Table 3 and Figure 10A-C).…”

“…However, when we investigated the effect of different excitation wavelengths on the 3-HF probe loaded copolymers, we found that the intensity ratio I N* /I T* ( Figure 7A-C), and the position of the N* band ( Figure 8) varies for every dye. In solvents, this excitation dependence is not observed [32], and so it could be attributed to a classical red-edge effect which is usually observed in rigid media [42][43]. In this case, red-edge excitation will photo-select dielectrically stabilized species, which in turn leads to lower T* emission.…”

Exploring membrane organization and dynamics by the wavelength-selective fluorescence approach

“…It has previously been shown for 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD)-labeled phospholipids incorporated into model membranes, that a dipole moment change of Â/4 D upon excitation is enough to give rise to significant red edge effects . A recent comprehensive review on the red edge effect is provided by Demchenko (2002).…”

Crystal structure of L-tryptophaniumphosphite,(C11H13N2O2)[H2PO3]

“…Discussion L-Tryptophan is a naturally occurring amino acid, with a non-polar side chain and no net charge at physiological pH. Tryptophan fluorescence is widely used as a tool to monitor changes in proteins and to make inferences regarding conformation and dynamics [3,4], The nonexponential fluorescence decay of tryptophan, in * Correspondence author (e-mail: manuela@pollux.fis.uc.pt) aqueous solutions, has been explained by the emission from noninterconverting rotamers which have different lifetimes due to different rates of intramolecular charge transfer [5]. Looking for compounds with optical properties and phase transitions, we have been synthesizing L-tiyptophan salts, namely the title compound, L-tryptophanium phosphite.…”