Oxygen quenching of sensitized terbium luminescence in complexes of terbium with small organic ligands and proteins.

Prendergast, F. G.; Lü, Jianguo; Callahan, P J

doi:10.1016/s0021-9258(18)32585-7

Cited by 45 publications

(16 citation statements)

References 35 publications

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“…Fluorescence emission spectra was scanned in the wavelength range of 290–500 nm by the excitation wavelength of 278 nm, emission wavelength of 290 nm, and slit width of 5 nm . Fluorescence quenching was described by the Stern–Volmer equation, as follows: where F and F 0 are fluorescence intensity with and without quenching agent, respectively; K SV is the Stern–Volmer quenching constant; [ Q ] denotes the quenching agent concentration; K q represents the quenching constant of biomolecules; and τ 0 reflects the life of the fluorophore, that is, τ 0 = 2.97 ns for α-amylase and τ 0 = 10 –8 s for α-glucosidase.…”

Section: Methodsmentioning

confidence: 99%

Research on the Influences of Five Food-Borne Polyphenols on In Vitro Slow Starch Digestion and the Mechanism of Action

Ren

Liu

2019

J. Agric. Food Chem.

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Inhibiting starch digestion can effectively control postprandial blood sugar level. In this study, the in vitro digestion differences among the mixtures of five polyphenols (i.e., procyanidins [PAs], catechin [CA], tannic acid [TA], rutin [RU], and quercetin [QU]) and starch were analyzed through an in vitro simulation test of starch digestion. The interaction characteristics of these five polyphenols with α-amylase and α-glucosidase were investigated in terms of the inhibition effect, dynamics, fluorescence quenching, and circular dichroism (CD). The results revealed that the rapidly digestible starch (RDS) contents decreased, while the resistant starch (RS) contents increased. All five polyphenols inhibited the α-amylase activity through the noncompetitive approach but inhibited the α-glucosidase activity through the competitive approach. Five polyphenols combined with α-amylase spontaneously by using the hydrophobic effect. The interaction of PAs and QU with α-glucosidase were recognized as van der Waals forces and H bonding, whereas CA and TA interacted with α-glucosidase through the hydrophobic effect. All five polyphenols can cause conformational changes in enzymes.

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Section: Methodsmentioning

confidence: 99%

Research on the Influences of Five Food-Borne Polyphenols on In Vitro Slow Starch Digestion and the Mechanism of Action

Ren

Liu

2019

J. Agric. Food Chem.

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“…The fluorescence quenching data were analyzed according to Zhang et al [24,27]. Thermodynamic parameters, including binding constant (K b ), number of binding sites (n), enthalpy change (∆H), entropy change (∆S), and free energy change (∆G), were calculated according to Wang et al [28].…”

Section: Analysis Of Fluorescence Quenching Datamentioning

confidence: 99%

Structure Activity Relationships of Flavonoids as Potent α-Amylase Inhibitors

Yuan

Liu

Yang

et al. 2014

Natural Product Communications

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The effects of three flavonoids (quercetin, luteolin, diosmetin) on -amylase were examined by enzymatic kinetics and fluorescence spectroscopy. The three test flavonoids were non-competitive inhibitors of the enzyme. Addition of flavonoids led to fluorescence quenching of -amylase. The quenching was initiated from the formation of a complex between the flavonoids and the enzyme, corresponding to a static quenching process. An -amylase molecule provides a binding site for the test flavonoid. The main binding force was hydrophobic. The decreasing order of inhibition of -amylase by flavonoids and the binding force was luteolin, diosmetin, and quercetin. It is demonstrated that hydroxylation in ring C and methylation of the hydroxyl group in ring B of flavonoids may weaken the binding affinities to -amylase.

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“…In some Tb metalloenzymes, ET has been demonstrated to proceed by long-range nonradiative energy transfer from protein aromatic singlet states. , At shorter distances, a Dexter exchange mechanism has been suggested . Rare earth sensitization by aromatic triplet donors in nonbiological systems has been known for some time, , and quenching of Tb emission by dissolved O 2 strongly suggests the involvement of triplet state donors. , The presence of an O 2 -dependent rise in Tb luminescence following pulsed excitation has been presented as evidence for a triplet state donor in TbAP 14 and in Tb elastase . We undertook this study of the AP system at low temperature to help resolve the nature of protein ET to Tb in TbAP.…”

Section: Introductionmentioning

confidence: 99%

Low-Temperature Study of Photoinduced Energy Transfer from Tryptophan Residues of Escherichia coli Alkaline Phosphatase to Bound Terbium

et al. 2003

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Low-temperature phosphorescence (LTP) decay measurements have been carried out in wild-type Escherichia coli alkaline phosphatase (AP), metal-depleted AP (apoAP), and terbium-substituted AP (TbAP) at 77, 4.2, and 1.2 K. Over this temperature range, Tb emission monitored at 542.4 nm decays with two apparent lifetime components of 16−20 ms and 130−170 ms when TbAP is excited at 280 nm where Tb absorbs negligibly. These lifetimes are orders of magnitude greater than exhibited by TbCl3 at low temperature and by TbAP at room temperature; we attribute this Tb luminescence in TbAP largely to energy transfer from the triplet state of initially excited tryptophan. LTP and ODMR at 1.2 K suggest that Trp109 and Trp220 have similar environments in AP and in apoAP. Trp109 is found to occupy two distinct sites in both AP and apo AP that exhibit resolved ODMR transitions. Comparison of the phosphorescence spectra of AP and TbAP shows clearly that the sensitized Tb emission observed in TbAP is due selectively to energy transfer (ET) from Trp109 to Tb and not significantly from Trp220. Evaluation of the results also suggests that ET takes place through space by Dexter's exchange mechanism, where the lowest triplet state of Trp acts as donor and the 7F6 ground state of Tb acts as acceptor. The ratio of the two ET rate constants suggests that two sites of Trp109 (possibly those resolved by ODMR) act as donors to either or both metal-binding sites, M2 or M3, rather than one Trp109 site transferring energy to Tb at either site M2 or M3.

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Oxygen quenching of sensitized terbium luminescence in complexes of terbium with small organic ligands and proteins.

Cited by 45 publications

References 35 publications

Research on the Influences of Five Food-Borne Polyphenols on In Vitro Slow Starch Digestion and the Mechanism of Action

Research on the Influences of Five Food-Borne Polyphenols on In Vitro Slow Starch Digestion and the Mechanism of Action

Structure Activity Relationships of Flavonoids as Potent α-Amylase Inhibitors

Low-Temperature Study of Photoinduced Energy Transfer from Tryptophan Residues of Escherichia coli Alkaline Phosphatase to Bound Terbium

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