pH-dependent fluorescence spectroscopy XVII: First excited singlet state dissociation constants, phtootautomerism and dual fluorescence of flavonol

Wolfbeis, Otto S.; Knierzinger, Andreas; Schipfer, Rudolf

doi:10.1016/0047-2670(83)80009-4

Cited by 74 publications

(49 citation statements)

References 21 publications

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“…USA 93 (1996) 12961 predominantly in anionic form. Tyr-411 is the most probable candidate for the 3-HF anion formation in this site, since the phenolic hydroxyl group has approximate pK values of 9.8-10.4, which are comparable with the pK value of the S 0 state of 3-HF (28). The lower affinity binding site of 3-HF, having binding constant of 2.5 ϫ 10 5 M Ϫ1 , is situated in the IIA subdomain and is occupied by the normal tautomer.…”

Section: Biophysics: Sytnik and Litvinyukmentioning

confidence: 50%

“…On the basis of the pHdependence of the 3-HF absorption (26)(27)(28), it is known that the band with max ϭ 420 nm corresponds to the anion, while the band with max ϭ 340 nm corresponds to the neutral form. The absorption of the neutral form is only weakly dependent on the surrounding medium exhibiting slight spectral shift in different solvents.…”

Section: Appendix A: Decomposition Of the Absorption Spectra Of The Hmentioning

confidence: 99%

“…In both cases, the absorption spectra consist of three distinct bands. Comparison of these bands with the 3-HF absorption in aprotic and protic solvents (26)(27)(28) suggests that both 3-HF normal tautomer ( max ϭ 345 nm) and anion ( max ϭ 417 nm) contribute to the probe absorption. Large spectral shift between the ionic forms of 3-HF allows to separate their relative contributions to the absorption of HSA-3-HF complexes ( Fig.…”

mentioning

confidence: 99%

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Energy transfer to a proton-transfer fluorescence probe: Tryptophan to a flavonol in human serum albumin

Sytnik

Litvinyuk

1996

Proc. Natl. Acad. Sci. U.S.A.

171

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A protein f luorescence probe system, coupling excited-state intermolecular Förster energy transfer and intramolecular proton transfer (PT), is presented. As an energy donor for this system, we used tryptophan, which transfers its excitation energy to 3-hydroxyf lavone (3-HF) as a f lavonol prototype, an acceptor exhibiting excited-state intramolecular PT. We demonstrate such a coupling in human serum albumin-3-HF complexes, excited via the single intrinsic tryptophan (Trp-214). Besides the PT tautomer f luorescence ( max ‫؍‬ 526 nm), these protein-probe complexes exhibit a 3-HF anion emission ( max ‫؍‬ 500 nm). Analysis of spectroscopic data leads to the conclusion that two binding sites are involved in the human serum albumin-3-HF interaction. The 3-HF molecule bound in the higher affinity binding site, located in the IIIA subdomain, has the association constant (k 1 ) of 7.2 ؋ 10 5 M ؊1 and predominantly exists as an anion. The lower affinity site (k 2 ‫؍‬ 2.5 ؋ 10 5 M ؊1 ), situated in the IIA subdomain, is occupied by the neutral form of 3-HF (normal tautomer). Since Trp-214 is situated in the immediate vicinity of the 3-HF normal tautomer bound in the IIA subdomain, the intermolecular energy transfer for this donor͞ acceptor pair has a 100% efficiency and is followed by the PT tautomer f luorescence. Intermolecular energy transfer from the Trp-214 to the 3-HF anion bound in the IIIA subdomain is less efficient and has the rate of 1.61 ؋ 10 8 s ؊1 , thus giving for the donor͞acceptor distance a value of 25.5 Å.Excitation by light may initiate both intramolecular and intermolecular transformations of a molecule. Among excited-state intramolecular processes, the most important are electron transfer (1-4), proton transfer (PT; refs. 5 and 6), and conformational transformation (e.g., twisting, torsion, and isomerization; refs. 7-9). The most conspicuous intermolecular events are electron, proton, and energy transfer (10, 11). Excited-state transformations can be coupled with each other and with the surrounding medium. Dependence of the excitedstate intramolecular electron transfer on environmental relaxation (2, 3) and the twisting of solute groups in response to the excited-state charge transfer (12-15) are well-established phenomena. When joined in one molecular system, excited-state events can compete dynamically. An example of such competition is the mutual exclusion of intramolecular electron and PT in 4Ј-diethylamino-3-hydroxyflavone (16-19). Proper pairing of excited-state transformations can be a source of structural͞dynamical information about the molecules possessing these transformations, the excited-state transformations themselves, and the medium where the coupling takes place.The present paper focuses on the coupling between the Förster intermolecular energy transfer (11,20,21) and intramolecular PT (refs. 6 and 22; Fig. 1). The first step of such a coupling is the R Ϫ6 -dependent (R is the intermolecular distance) dipole-dipole intermolecular energy transfer from excited donor to unexcite...

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Section: Biophysics: Sytnik and Litvinyukmentioning

confidence: 50%

Section: Appendix A: Decomposition Of the Absorption Spectra Of The Hmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Energy transfer to a proton-transfer fluorescence probe: Tryptophan to a flavonol in human serum albumin

Sytnik

Litvinyuk

1996

Proc. Natl. Acad. Sci. U.S.A.

171

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“…Within the course of a project to prepare 3 complexes, we have reported the synthesis of cymene complexes with various substituted 3 and the influence of the substitution pattern 25 substituent on the in vitro anticancer activity order to extend the structure-activity relationships (SAR series of Ru II (arene) complexes with 3-hydroxyflavone 2 ; η 6 -arene = cym, toluene, biphen I), yielding complexes 1-13 in good to very good yields (Scheme 1). The compounds were characterised analytical methods (see experimental part) and 35 over one year though exposed to sunlight and air Scheme 1.…”

Section: Synthesismentioning

confidence: 99%

“…The octahedral geometry of ruthenium, its binding ability to plasma proteins and the number of possible oxidation states in biological environments, makes it well suitable for drug design. 1 By now, several ruthenium complexes have shown interesting properties in vivo and a generally lower 25 toxicity than for platinum drugs was observed. 2 Two Ru In the course of ruthenium anticancer drug development programmes, organometallic and especially half-sandwich Ru II (η 6 -arene) complexes have more and more demonstrated their 35 potential.…”

Section: Introductionmentioning

confidence: 99%

3-Hydroxyflavones vs. 3-hydroxyquinolinones: structure–activity relationships and stability studies on Ru^II(arene) anticancer complexes with biologically active ligands

et al. 2013

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RuII (η 6 -arene) complexes, especially with bioactive ligands, are considered as very promising compounds for anticancer drug design. We have shown recently that Ru II (η 6 -p-cymene) complexes with 3-hydroxyflavone ligands exhibit very high in vitro cytotoxic activities correlating with a strong inhibition of topoisomerase IIα. In order to expand the structure-activity relationships and to determine the impact 10 of lipophilicity of the arene ligand and of the hydrolysis rate on anticancer activity, a series of novel 3-hydroxyflavone derived Ru II (η 6 -arene) complexes were synthesised. Furthermore, the impact of the heteroatom in the bioactive ligand backbone was studied by comparing the cytotoxic activity of Ru II (η 6 -pcymene) complexes of 3-hydroxyquinolinone ligands with that of their 3-hydroxyflavone analogues. To better understand the behaviour of these Ru II complexes in aqueous solution, the stability constants and 15 pK a values for complexes and corresponding ligands were determined. Furthermore, the interaction with the DNA model 5'-GMP and with a series of amino acids was studied in order to elucidate potential biological target structures.

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Protein-flavonol interaction: Fluorescence spectroscopic study

2001

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pH-dependent fluorescence spectroscopy XVII: First excited singlet state dissociation constants, phtootautomerism and dual fluorescence of flavonol

Cited by 74 publications

References 21 publications

Energy transfer to a proton-transfer fluorescence probe: Tryptophan to a flavonol in human serum albumin

Energy transfer to a proton-transfer fluorescence probe: Tryptophan to a flavonol in human serum albumin

3-Hydroxyflavones vs. 3-hydroxyquinolinones: structure–activity relationships and stability studies on Ru^II(arene) anticancer complexes with biologically active ligands

Protein-flavonol interaction: Fluorescence spectroscopic study

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pH-dependent fluorescence spectroscopy XVII: First excited singlet state dissociation constants, phtootautomerism and dual fluorescence of flavonol

Cited by 74 publications

References 21 publications

Energy transfer to a proton-transfer fluorescence probe: Tryptophan to a flavonol in human serum albumin

Energy transfer to a proton-transfer fluorescence probe: Tryptophan to a flavonol in human serum albumin

3-Hydroxyflavones vs. 3-hydroxyquinolinones: structure–activity relationships and stability studies on RuII(arene) anticancer complexes with biologically active ligands

Protein-flavonol interaction: Fluorescence spectroscopic study

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3-Hydroxyflavones vs. 3-hydroxyquinolinones: structure–activity relationships and stability studies on Ru^II(arene) anticancer complexes with biologically active ligands