The Bimolecular Reactivity of Singlet Molecular Oxygen

Gorman, A. A.

doi:10.1002/9780470133484.ch4

Cited by 50 publications

(6 citation statements)

References 168 publications

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“…Enzymatic reduction of the oxygen concentration upon addition of Oxyrase prevents photobleaching associated with the generation of singlet oxygen, resulting in an increase in fluorescence intensity from the larger number of molecules in the focal volume with little change in the brightness of individual fluorophores (Table 2). Decreasing the concentration of molecular oxygen also results in significant increases in the triplet state that is most pronounced for the free dye, consistent with prior suggestions that singlet oxygen is generated upon the collisional interaction between oxygen and fluorophores in the first excited triplet state (10,43,44).…”

Section: Resultssupporting

confidence: 88%

Fluorophore-Assisted Light Inactivation of Calmodulin Involves Singlet-Oxygen Mediated Cross-Linking and Methionine Oxidation

et al. 2006

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Fluorophore-assisted light inactivation (FALI) permits the targeted inactivation of tagged proteins and, when used with cell-permeable multiuse affinity probes (MAPs), offers important advantages in identifying physiological function, because targeted protein inactivation is possible with spatial and temporal control. However, reliable applications of FALI, also known as chromophore-assisted light inactivation (CALI) with fluorescein derivatives, have been limited by lack of mechanistic information regarding target protein sensitivity. To permit the rational inactivation of targeted proteins, we have identified the oxidizing species and the susceptibility of specific amino acids to modification using the calcium regulatory protein calmodulin (CaM) that, like many essential proteins, regulates signal transduction through the reversible association with a large number of target proteins. Following the covalent and rigid attachment of 4',5'-bis(1,3,2-dithioarsolan-2-yl)fluorescein (FlAsH) to helix A, we have identified light-dependent oxidative modifications of endogenous methionines to their corresponding methionine sulfoxides. Initial rates of methionine oxidation correlate with surface accessibility and are insensitive to the distance between the bound fluorophore and individual methionines, which vary between approximately 7 and 40 A. In addition, we observed a loss of histidines, as well as zero-length cross-linking with binding partners corresponding to the CaM-binding sites of smooth myosin light chain kinase and ryanodine receptor. Our results provide a rationale for proteomic screens using FALI to inhibit the function of many signaling proteins, which, like CaM, commonly present methionines at binding interfaces.

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Section: Resultssupporting

confidence: 88%

Fluorophore-Assisted Light Inactivation of Calmodulin Involves Singlet-Oxygen Mediated Cross-Linking and Methionine Oxidation

et al. 2006

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“…reactant R Two types of singlet oxygen reactions have been observed, a physical quenching giving back ground-state oxygen and phenolic compound and a chemical quenching giving various products including corresponding quinones. In both cases, the reactions involved are electron transfer reactions from the DP to singlet oxygen as demonstrated by spectroscopic evidence of the formation of phenoxyl radicals ΦO • (31)(32)(33).…”

Section: Table 2 Rate Constants For Reactions Of Halogenated Peroxyl ...mentioning

confidence: 99%

Two-Step Mechanism of Induction of the Gene Expression of a Prototypic Cancer-Protective Enzyme by Diphenols

Bensasson

Zoete

Dinkova‐Kostova

et al. 2008

Chem. Res. Toxicol.

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Cancer-preventive activity by exogenous molecules can be mediated by enhancing the expression of cytoprotective enzymes [e.g, glutathione- S-transferase (GST) or NAD(P)H-quinone oxidoreductase 1 (NQO1)] via antioxidant-response elements (AREs) present in the promoter regions of their genes. Previously, potency of induction of NQO1 has been linearly correlated with the ability to release an electron from different classes of inducers, including diphenols, phenylpropenoids, and flavonoids. In the present work, we focus on the induction of NQO1 by diphenols, which we consider as a model underlying the mechanisms of action of other phenolic inducers such as phenylpropenoids and flavonoids. A two-step mechanism of NQO1 activation is proposed involving (i) oxidation of diphenol inducers to their quinone derivatives and (ii) oxidation of two highly reactive thiol groups by these quinones of a protein involved in NQO1 induction. These two putative routes are supported by linear correlations between the inducer potencies and the redox properties of diphenols and of their corresponding quinones. The linear correlations demonstrate the possibility to predict the enhanced gene expression of enzymatic defenses by diphenols from quantum mechanical calculations (i) of the ability of diphenols to release electrons and (ii) of the electron affinity of their corresponding quinones.

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“…Singlet oxygen is a better oxidizing agent than molecular oxygen; its reactions include addition to double bonds, of particular importance in lipid peroxidation. We also include the ene reaction, as well as 2 + 4 and 2 + 2 additions in this category (20). Because of this high reactivity, it is common practice to determine singlet oxygen quantum yield (Φ 1 Δ g ) in oxygen or air‐equilibrated solutions when in the process of studying the photosensitizing properties of a drug.…”

Section: Time‐resolved Luminescence Techniquesmentioning

confidence: 99%

Laser Techniques in the Study of Drug Photochemistry^¶

Cosa

Scalano

2004

Photochem & Photobiology

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This review describes the application of different laser time‐resolved techniques, such as time‐resolved fluorescence, phosphorescence and laser flash photolysis, to elucidate the mechanism of drug photodegradation. The assignment of transient species based on their luminescence or absorption spectra and based on their reactivity to various quenchers is illustrated. The mathematical expressions used in fitting measured transient decays over time are also discussed. Practical situations found in the literature and relevant to drug photodegradation illustrate different examples. The importance of laser power, concentration and absorbance of the ground state, as well as other parameters intrinsic to laser techniques are discussed.

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The Bimolecular Reactivity of Singlet Molecular Oxygen

Cited by 50 publications

References 168 publications

Fluorophore-Assisted Light Inactivation of Calmodulin Involves Singlet-Oxygen Mediated Cross-Linking and Methionine Oxidation

Fluorophore-Assisted Light Inactivation of Calmodulin Involves Singlet-Oxygen Mediated Cross-Linking and Methionine Oxidation

Two-Step Mechanism of Induction of the Gene Expression of a Prototypic Cancer-Protective Enzyme by Diphenols

Laser Techniques in the Study of Drug Photochemistry^¶

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The Bimolecular Reactivity of Singlet Molecular Oxygen

Cited by 50 publications

References 168 publications

Fluorophore-Assisted Light Inactivation of Calmodulin Involves Singlet-Oxygen Mediated Cross-Linking and Methionine Oxidation

Fluorophore-Assisted Light Inactivation of Calmodulin Involves Singlet-Oxygen Mediated Cross-Linking and Methionine Oxidation

Two-Step Mechanism of Induction of the Gene Expression of a Prototypic Cancer-Protective Enzyme by Diphenols

Laser Techniques in the Study of Drug Photochemistry¶

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Laser Techniques in the Study of Drug Photochemistry^¶