Effect of viscosity and temperature on torsional relaxation of molecular rotors

Loutfy, Rafik O.; Arnold, Bradley A.

doi:10.1021/j100218a023

Cited by 270 publications

(248 citation statements)

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“…The data could be fitted using the empirical relationship F ∝ η 0.6 / . Such a relationship has been described previously for a class of fluorescent dyes called molecular rotors (30,40). These dyes show increased fluorescence when introduced into highviscosity media due to the decreased torsional relaxation.…”

Section: B) Assembly Of Phfs Can Be Monitored By the Interaction Withmentioning

confidence: 86%

Rapid Assembly of Alzheimer-like Paired Helical Filaments from Microtubule-Associated Protein Tau Monitored by Fluorescence in Solution

et al. 1998

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Alzheimer's disease is characterized by the progressive deposition of two types of fibers in the affected brains, the amyloid fibers (consisting of the A peptide, generating the amyloid plaques) and paired helical filaments (PHFs, made up of tau protein, forming the neurofibrillary tangles). While the principles of amyloid aggregation are known in some detail, the investigation of PHF assembly has been hampered by the low efficiency of tau aggregation, the requirement of high protein concentrations, and the lack of suitable detection methods. Here we report a quantitative assay system that permits monitoring of the assembly of PHFs in real time by the fluorescence of dyes such as thioflavine S or T. Using this assay, we evaluated parameters that influence the efficiency of filament formation. Disulfide-linked dimers of tau constructs representing the repeat domain assemble into PHFs most efficiently, but other tau isoforms or constructs form bona fide PHFs as well. The rate of assembly is greatly enhanced by polyanions such as RNA, heparin, and notably polyglutamate which resembles the acidic tail of tubulin. The assembly is optimal at pH ∼6 and low ionic strengths (<50 mM) and increases steeply with temperatures above 30°C , indicating that it is an entropy-driven process.

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Section: B) Assembly Of Phfs Can Be Monitored By the Interaction Withmentioning

confidence: 86%

Rapid Assembly of Alzheimer-like Paired Helical Filaments from Microtubule-Associated Protein Tau Monitored by Fluorescence in Solution

et al. 1998

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“…The partial quenching of the fluorescence of bound thioflavin T when a ligand binds to the acylation site cannot result from fluorescence resonance energy transfer, because there is no spectral overlap between thioflavin T and either of the acylation site ligands edrophonium or TMTFA. However, the fluorescence of thioflavin T has been shown to depend on solvent viscosity (27), with a relationship previously described for a class of fluorescent dyes called molecular rotors (28,29). These dyes show increased fluorescence when introduced into high viscosity media, due to a decreased torsional relaxation.…”

Section: Discussionmentioning

confidence: 99%

Thioflavin T Is a Fluorescent Probe of the Acetylcholinesterase Peripheral Site That Reveals Conformational Interactions between the Peripheral and Acylation Sites

Ferrari¹,

Mallender

Inestrosa

et al. 2001

Journal of Biological Chemistry

128

176

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Three-dimensional structures of acetylcholinesterase (AChE) reveal a narrow and deep active site gorge with two sites of ligand binding, an acylation site at the base of the gorge, and a peripheral site near the gorge entrance. Recent studies have shown that the peripheral site contributes to catalytic efficiency by transiently binding substrates on their way to the acylation site, but the question of whether the peripheral site makes other contributions to the catalytic process remains open. A possible role for ligand binding to the peripheral site that has long been considered is the initiation of a conformational change that is transmitted allosterically to the acylation site to alter catalysis. However, evidence for conformational interactions between these sites has been difficult to obtain. Here we report that thioflavin T, a fluorophore widely used to detect amyloid structure in proteins, binds selectively to the AChE peripheral site with an equilibrium dissociation constant of 1.0 M. The fluorescence of the bound thioflavin T is increased more than 1000-fold over that of unbound thioflavin T, the greatest enhancement of fluorescence for the binding of a fluorophore to AChE yet observed. Furthermore, when the acylation site ligands edrophonium or m-(N, N,Ntrimethylammonio)trifluoroacetophenone form ternary complexes with AChE and thioflavin T, the fluorescence is quenched by factors of 2.7-4.2. The observation of this partial quenching of thioflavin T fluorescence is a major advance in the study of AChE for two reasons. First, it allows thioflavin T to be used as a reporter for ligand reactions at the acylation site. Second, it indicates that ligand binding to the acylation site initiates a change in the local AChE conformation at the peripheral site that quenches the fluorescence of bound thioflavin T. The data provide strong evidence in support of a conformational interaction between the two AChE sites.

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“…Dual emission and a TICT state have also been found for 4-diethylaminobenzoic acid ethyl ester [29]. Additional systems in which involvement of a TICT state has been discussed are: 4-(9-anthryl)-N,N-dimethylanilines (ADA-system) [30][31][32], a series of N-aryl carbazoles (pyrroles) [33], N,N-dialkyl-4-(l,3,5-triazinyl)-anilines (DTA-system) [34], 4-N,N-dialkylaminobenzylidenemalonitriles (DBM-system) [35,36], and (phenylamino)naphthalenesulfonates [37],…”

Section: Discussionmentioning

confidence: 99%

Fluorescence of Trans-4-Cyano-4′-dimethylaminostilbene; No Evidence for a TICT State

Gruen

Görner

1983

Zeitschrift Für Naturforschung A

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The fluorescence properties of trans-4-cyano-4'-dimethylaminostilbene (trans-1) and a rigid analogue, in which the dimethylaminophenyl group is replaced by an indoline ring, trans-1-(4-cyanophenyl)-2-(5-[2,3-dihydro]N-methylindolyl)ethylene (trans-2) were studied in 20 solvents. The quantum yields of fluorescence (tf> f ) and of trans-»eis photoisomerization (<2>t-c) as well as the fluorescence maximum (v f ) and the bandwidth (zlv f ) were examined. The activation energies (range: 3.5-7.8 kcal/mol) obtained from <2> f and <£ t _ c measurements are nearly the same for 1 and 2 in a given solvent. 0 f , v f and Jv f as a function of solvent polarity and temperature show similar trends for 1 and 2. No dual emission was observed for either of the cyanostilbenes. These findings indicate that a twisted intramolecular charge transfer (TICT) state is not involved in the relaxation process of the first excited trans singlet state ('t*). The main deactivation pathway of 't* competing with fluorescence is trans eis photoisomerization by twisting about the C = C double bond in the first excited singlet state for both.

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Effect of viscosity and temperature on torsional relaxation of molecular rotors

Cited by 270 publications

References 3 publications

Rapid Assembly of Alzheimer-like Paired Helical Filaments from Microtubule-Associated Protein Tau Monitored by Fluorescence in Solution

Rapid Assembly of Alzheimer-like Paired Helical Filaments from Microtubule-Associated Protein Tau Monitored by Fluorescence in Solution

Thioflavin T Is a Fluorescent Probe of the Acetylcholinesterase Peripheral Site That Reveals Conformational Interactions between the Peripheral and Acylation Sites

Fluorescence of Trans-4-Cyano-4′-dimethylaminostilbene; No Evidence for a TICT State

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