Intramolecular Fluorescence Quenching Research Articles

Effect of a protein on the light energy conversion in dual fluorophore-nitroxide probes studied by ESR and fluorescence spectroscopy

Probing biological environment with dual fluorophore-nitroxide (FN) molecules in which fluorophore is tethered with nitroxide, a fluorescence quencher, opens unique opportunities to study molecular dynamics and micropolarity of the medium which affect intramolecular fluorescence quenching (IFQ), electron transfer, photoreduction and light energy conversion. In such molecules, the excited fragment of the chromophore can serve as an electron donor, and the nitroxide fragment as an electron acceptor. The same groups allow monitoring of molecular dynamics and also make it possible to measure micropolarity of the medium in the vicinity of the donor (by fluorescence technique) and acceptor (by electron spin resonance [ESR]) moieties. In the present work, two dual dansyl-nitroxide probes were incorporated in a binding site of bovine serum albumin. Their interactions with the protein, mobility, and photoreduction, as well as micropolarity of the media, have been studied by ESR and fluorescence methods. IFQ and spectral relaxation shift of the dansyl fragment have been monitored by time-resolved fluorescence technique. In parallel, computational studies on intramolecular dynamics of the FN probe were performed. On the basis of the Marcus model of the electron transfer between the excited dansyl fluorophore (donor) and nitroxide group (acceptor) and our experimental data, the mechanism of the electron transfer in the dual molecules incorporated into bovine serum albumin was established. It was shown that dual FN molecules in the protein meet main requirements for an efficient light energy conversion system.

Bromoacyl Analogues of Phosphatidylcholine with Intramolecular Fluorescence Quenching and Their Use as Substrates for Continuous Monitoring of Phospholipase A2Activity

Two new derivatives of phosphatidylcholine with intramolecular fluorescence quenching were obtained by substituting residues of pyrene butyric and bromine-containing fatty acids for acyl chains. The two compounds can be used for quantitative evaluation of catalytic activity of pancreatic phospholipase A2 in kinetic mode.

Intramolecular Fluorescence Quenching of Crowned 7-Aminocoumarins as Potential Fluorescent Chemosensors

The effects of the nature of solvent, temperature and complex formation with alkali and alkaline-earth metal cations, as well as protonation, on the efficiency and the kinetics of fluorescence of 3-azacrowned 7-diethylaminocoumarins have been studied. For the crown-ethers under investigation, the ratio of a dipole moment to the radius of Onsager cavity delta micro/rho is a constant value, and a macrocycle does not affect delta micro, and rho. The fluorescence of coumarin 1 in acetonitrile is quenched by an electron donor, triethylamine, with the Stern-Volmer constant being equal to (0.474+/-0.009) M(-1). The decrease in coumarin 1 fluorescence quantum yield upon the introduction of N-alkylazacrown moiety into position 3 is caused by an intramolecular photoinduced electron transfer from the nitrogen atom of macroheterocycle to the coumarin moiety, where the excitation is localized. The fluorescence quenching has an activation energy 2.32+/-0.05 kcal/mol in various hydrocarbons, and does not depend on the solvent viscosity. The fluorescence kinetics of free crowned coumarins in methanol is not monoexponential because of the existence of macrocycle conformers, or because of the hydrogen bond complex formation between the solvent and the nitrogen atom of macrocycle, in which the efficiency of intramolecular electron transfer is different. Upon complex formation with alkali and alkaline-earth metal cations and upon protonation, the fluorescence quantum yield increases and fluorescence decay becomes monoexponential.

Intramolecular Fluorescence Quenching of Tyrosine by the Peptide α-Carbonyl Group Revisited

The environment-dependent multiexponential behavior of N-acetyltyrosinamide (NAYA) and other tyrosine derivatives is revisited, aiming for a better understanding of tyrosine as an intrinsic fluorescent probe for protein microenvironment changes during conformational changes. The effects of solvent polarity, viscosity, and temperature on the fluorescence decay of NAYA were evaluated using dioxane−water mixtures and pure solvents. Double-exponential decays were observed in dioxane−water mixtures above 70% (v/v) water concentration including pure water, for temperatures below 50 °C. However, at higher temperatures, or in dioxane−water mixtures with lower water concentrations, NAYA shows single-exponential decays. Single-exponential decays were also generally observed in pure solvents (dioxane, acetonitrile, methanol, ethanol, DMSO). The exception was the strong hydrogen-bond donor trifluorethanol, in which NAYA decays as a double exponential. The results are consistent with a solvent-modulated excited-state ...

ナフチルアラニン誘導体の分子内蛍光消光に及ぼす置換基効果

ナフチルアラニン誘導体の分子内蛍光消光に及ぼす置換基効果

Metal-Induced Self-Assembly of a Pyrene-Tethered Hydroxamate Ligand for the Generation of Multichromophoric Supramolecular Systems. The Pyrene Excimer as Switch for Iron(III)-Driven Intramolecular Fluorescence Quenching

We report the first example of intramolecular excimer formation in supramolecular trichromophoric systems resulting from the metal-directed self-assembly of chromophore-labeled ligand molecules. The trichromophoric gallium(III) chelate, (1)3Ga, shows an intense pyrene excimer fluorescence emission in acetonitrile, while the iron(III) analogue, (1)3Fe, exhibits a fluorescence of very low intensity compared to that of the free hydroxamate ligand 1. The trivalent gallium metal cation is demonstrated to play the role of an inert and transparent linker, whereas the ferric center acts additionally as an extra chromophore that quenches the pyrene singlet state. On the basis of low-temperature fluorescence measurements, the mechanism of quenching within (1)3Fe is attributed to a pyrene-to-iron electronic energy transfer process. 1H NMR and electronic absorption spectroscopies show that intramolecular interactions between pyrene chromophores prevail in the ground state, which leads to the formation of preassociated excimers for both chelates. From the dependence of the solvent on the photophysical properties of (1)3Ga and (1)3Fe, it is inferred that the Fe(III)-induced quenching process is triggered by the ground-state and excited-state intramolecular dimerization of the pyrene moieties, with the pyrene-to-iron energy transfer taking place more readily from the excimer singlet state as donor than from the locally excited state.

Solvent and Temperature Effects on the Intramolecular Fluorescence Quenching in Dipeptide Model Compounds [1

AbstractThe mechanism of fluorescence quenching through intramolecular electron transfer (ET) was investigated in the dipeptide model compounds DL‐N‐[4‐(diethylamino)alkyl]‐2‐acetylamino‐3‐(1‐naphthyl)propionamides (1) by stationary and time‐resolved fluorescence spectroscopy in non‐polar and polar solvents. An analysis of the observed singlet‐exciplex fluorescence and the biexponential decay of monomer fluorescence established that emission quenching in non‐polar solvents proceeds through the singlet‐exciplex intermediate with a strong charge‐transfer character, and that the quenching rate constant increases with a decrease in free‐energy change for ET (ΔGet) but it is not very sensitive to the variation of methylene chain length in 1. The observations of biexponential emission decay and very weak exciplex emission in polar solvents suggest that a singlet exciplex and/or a solvent‐separated radical ion pair become a key intermediate in the quenching process. The finding that the magnitude of ΔGet, being regarded as a measure of the stability of an intermediate formed, linearly correlates with the logarithm of solvent viscosity is explained in terms of a short‐lived singlet exciplex that serves as a precursor of the radical ion pair intermediate. Thus, solvent viscosity effects on the biexponential emission decay processes of 1 with small ΔGet in protic polar solvents provide a good criterion for the exclusive operation of a singlet‐exciplex mechanism in the case that a short‐lived exciplex and a long‐lived radical ion pair are produced. It was also found that any of activation parameters for ET fluorescence quenching process in acetonitrile is comparable to the corresponding parameter obtained in methylcyclohexane. This finding may present kinetic evidence for the participation of a singlet‐exciplex mechanism in the aprotic polar solvent, acetonitrile.

The Inverted Region of Electron Transfer in Intramolecular Fluorescence Quenching of Quinolinium Betaines

AbstractFluorescence quenching through intramolecular electron transfer (ET) was studied in N‐(ω‐sulfonatoalkyl)‐ and N‐(ω‐carboxyalkyl)‐quinolinium betaines by stationary and time‐resolved fluorescence spectroscopy in the solvents water and acetonitrile. These substances are zwitterionic in the ground and local excited state of the quinolinium chromophore. In the sulfonato compounds fluorescence quenching through ET does not occur in water, whereas quenching is efficient in acetonitrile. A surprising opposite behaviour is observed for the carboxylato compounds: quenching is efficient in water whereas it is inefficient in acetonitrile. Semiempirical calculations were used to derive the parameters needed for the description of the quenching process by non‐adiabatic Bixon‐Efrima‐Jortner‐theory. These parameters include the solvent (λs) and the intrinsic (λv) contributions to the total reorganisation energy λ and the approximate free energy of reaction ΔG°. The vibrational motion of an aromatic C‐H bond influenced by the interaction with the negatively charged donor was taken as the major intramolecular accepting mode. ET fluorescence quenching in the present compounds and solvents may be interpreted in terms of the “normal” and the “inverted region” of Marcus theory.

Viscosity Effects on the Intramolecular Fluorescence Quenching in Dipeptide Model Compounds

AbstractThe finding that the increased solvent viscosity decreases the rate for intramolecular fluorescence quenching in the title compounds [N(n)D], giving a singlet‐exciplex intermediate, but increases the rate for the reverse process, regenerating the locally excited singlet‐state N(n)D, is explained in terms of the viscosity‐dependent free‐energy change for this fluorescence quenching process (ΔGet). A linear correlation between the ΔGet and the logarithm of solvent viscosity is found to provide a good criterion for a singlet‐exciplex mechanism in polar solvents.

Efficient Intramolecular Fluorescence Quenching in Triphenylmethane‐Dyes Involving Excited States with Charge Separation and Twisted Conformations

AbstractThe high fluorescence quantum yields ϕf of most Triphenylmethane(TPM)‐dyes and carbon‐bridged TPM‐dyes in highly viscous solutions (ϕf ranging from 0.3 to 0.8) decrease with increasing temperature by a factor > 100, due to viscosity dependent nonradiative deactivation. The deactivation rates krd of bridged model dyes are significantly smaller (by a factor of up to 170) as compared to krd of the unbridged crystal violet. ‐ Application of the Twisted Intramolecular Charge Transfer (TICT)‐model to neutral and ionic TPM‐dyes yields an explanation for the different behaviour of similarly structured compounds. The influence of steric and electronic factors on various TPM‐dyes is discussed within this framework. This leads to a simple rule involving donor and acceptor properties of molecular subunits, which permits the prediction of fluorescence properties (high quantum efficiency for laser dyes or ultrafast deactivation for saturable absorbers).

Liquid-Crystalline Solvents as Mechanistic Probes. 10. Dynamics of Intramolecular Quenching of Pyrenyl Fluorescence in the Liquid-Crystalline and Isotropic Phases of a Cholesteric Solvent1

Abstract The effect of cholesteric order in a 59.5/15.6/24.9 (w/w/w) mixture of cholesteryl oleate/cholesteryl nonanoate/cholesteryl chloride (CM) on the intramolecular fluorescence quenching of l,3-bis(l-pyrenyl) propane (P3P) has been explored. A comparison with fluorescence quenching of N,N-dimethyl-4-[3-(l-pyrenyl)propyl]aniline (P3D) in CM is made. From the Arrhenius activation parameters for quenching in the cholesteric and isotropic phases, it is concluded that the motions which take the ground state conformers of P3P to their quenching transition state are nearly impervious to macroscopic CM mesophase order: in the cholesteric phase, E'a = 10.5±0.4 kcal mol−1 and ΔS† = 1 ± 1 eu; in the isotropic phase, E'a = 10.0 ± 0.2 kcal mol−1 and ΔS† = 0 ± 0.5 eu. An explanation of these results is advanced.

ChemInform Abstract: LIQUID CRYSTALLINE SOLVENTS AS MECHANISTIC PROBES. 9. DYNAMICS OF INTRAMOLECULAR FLUORESCENCE QUENCHING PROCESSES OF N,N‐DIMETHYL‐4‐(3‐(1‐PYRENYL)PROPYL)ANILINE IN THE LIQUID CRYSTALLINE AND ISOTROPIC PHASES OF A CHOLESTERIC SOLVENT

Chemischer InformationsdienstVolume 14, Issue 7 Physical Organic Chemistry ChemInform Abstract: LIQUID CRYSTALLINE SOLVENTS AS MECHANISTIC PROBES. 9. DYNAMICS OF INTRAMOLECULAR FLUORESCENCE QUENCHING PROCESSES OF N,N-DIMETHYL-4-(3-(1-PYRENYL)PROPYL)ANILINE IN THE LIQUID CRYSTALLINE AND ISOTROPIC PHASES OF A CHOLESTERIC SOLVENT V. C. ANDERSON, V. C. ANDERSONSearch for more papers by this authorB. B. CRAIG, B. B. CRAIGSearch for more papers by this authorR. G. WEISS, R. G. WEISSSearch for more papers by this author V. C. ANDERSON, V. C. ANDERSONSearch for more papers by this authorB. B. CRAIG, B. B. CRAIGSearch for more papers by this authorR. G. WEISS, R. G. WEISSSearch for more papers by this author First published: February 15, 1983 https://doi.org/10.1002/chin.198307056AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue7February 15, 1983 RelatedInformation