The Syringe Nitroxide Free Radical – Part II

Buettner, Garry R.; Sharma, Mukesh Kumar

doi:10.3109/10715769309056s227

Cited by 10 publications

(12 citation statements)

References 9 publications

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“…On the other hand, the low intensity of the additional adducts seems reasonable since it is well known that DMPO-OOH adducts have short half lifetimes in water and easily undergo disproportionation [15]. Additionally, the kinetics of the reactions between •OOH and DMPO are typically much slower than that reported for the formation of the DMPO-OH spin adduct [16,17].…”

Section: Resultsmentioning

confidence: 86%

Light-induced generation of radicals on semiconductor-free carbon photocatalysts

Velasco

Maurino

Laurenti

et al. 2013

Applied Catalysis A: General

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This work provides an experimental evidence of the photoinduced generation of radical species upon UV irradiation of aqueous suspensions of carbon materials with varied textural, structural and chemical composition. The use of a powerful spectroscopic tool as spin trapping electron spin resonance (ESR) has allowed to detect and identify these radicals (among which are hydroxyl, superoxide and other organic radicals), which are the basis of the so-called Advanced Oxidation Processes. Our results demonstrate the ability of carbon materials-including activated carbons-to interact with UV light, and also to generate highly reactive species capable of promoting the photooxidation of an aromatic pollutant. Moreover, for some of the carbons the concentration of radicals was higher than that detected for titania powders. Although the photogeneration of radicals upon irradiation is a well-known process for inorganic semiconductors such as titanium oxide or zinc oxide, our results demonstrate a similar behavior on carbon materials in the absence of semiconductor additives. .

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Section: Resultsmentioning

confidence: 86%

Light-induced generation of radicals on semiconductor-free carbon photocatalysts

Velasco

Maurino

Laurenti

et al. 2013

Applied Catalysis A: General

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“…iron accelerates the reaction between catechols and superoxide (62) and complicates the detection of superoxide by DMPO (64). The reaction between superoxide and 3-chlorocatechol is expected to produce a mixture of multimeric species and o-quinones (62,65), which would be difficult to detect given their low concentrations.…”

Section: Table II In Vitro Reactivation Of Dhbd From Burkholderia Spmentioning

confidence: 99%

“…Finally, it is noted that the inactivation of DHBD with 3-chlorocatechol was rapid (Ͻ10 s) and would thus produce a burst of superoxide. Such bursts are harder to detect because the efficiency of trapping agents decreases as the rate of superoxide production increases (50,64). Nevertheless, the results strongly imply that inactivation of DHBD during catalytic turnover involves the dissociation of superoxide from the EAO 2 ternary complex.…”

Section: Table II In Vitro Reactivation Of Dhbd From Burkholderia Spmentioning

confidence: 99%

The Mechanism-based Inactivation of 2,3-Dihydroxybiphenyl 1,2-Dioxygenase by Catecholic Substrates

Vaillancourt¹,

Labbé²,

Drouin³

et al. 2002

Journal of Biological Chemistry

113

107

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2,3-Dihydroxybiphenyl 1,2-dioxygenase (EC 1.13.11.39), the extradiol dioxygenase of the biphenyl biodegradation pathway, is subject to inactivation during the steadystate cleavage of catechols. Detailed analysis revealed that this inactivation was similar to the O 2 -dependent inactivation of the enzyme in the absence of catecholic substrate, resulting in oxidation of the active site Fe(II) to Fe(III). Interestingly, the catecholic substrate not only increased the reactivity of the enzyme with O 2 to promote ring cleavage but also increased the rate of O 2 -dependent inactivation. Thus, in air-saturated buffer, the apparent rate constant of inactivation of the free enzyme was (0.7 ؎ 0.1) ؋ 10 ؊3 s ؊1 versus (3.7 ؎ 0.4) ؋ 10 ؊3 s ؊1 for 2,3-dihydroxybiphenyl, the preferred catecholic substrate of the enzyme, and (501 ؎ 19) ؋ 10 ؊3 s ؊1 for 3-chlorocatechol, a potent inactivator of 2,3-dihydroxybiphenyl 1,2-dioxygenase (partition coefficient ‫؍‬ 8 ؎ 2, K m app ‫؍‬ 4.8 ؎ 0.7 M). The 2,3-dihydroxybiphenyl 1,2-dioxygenase-catalyzed cleavage of 3-chlorocatechol yielded predominantly 2-pyrone-6-carboxylic acid and 2-hydroxymuconic acid, consistent with the transient formation of an acyl chloride. However, the enzyme was not covalently modified by this acyl chloride in vitro or in vivo. The study suggests a general mechanism for the inactivation of extradiol dioxygenases during catalytic turnover involving the dissociation of superoxide from the enzyme-catecholic-dioxygen ternary complex and is consistent with the catalytic mechanism.

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“…The photoinduced generation of ROS species, such as, hydroxyl radical (OH), superoxide (O 2 · ), and singlet oxygen ( 1 O 2 ) from photoexcited Cu 2 (OH)PO 4 NSs/QDs was examined using radicals, 5,5-dimethyl-1-pyrroline N-oxide (DMPO) was used as a spin-trapping agent. [22] Under dark conditions, Cu 2 (OH)PO 4 NSs (1 mg mL −1 ) in the presence of DMPO did not show any noticeable EPR signal (see green traces in Figure 3A).…”

Section: Photoinduced Generation Of Ros From Cu 2 (Oh)po 4 Nss and Qdsmentioning

confidence: 93%

Size and Shape Effects of Near‐Infrared Light‐Activatable Cu₂(OH)PO₄ Nanostructures on Phototherapeutic Destruction of Drug‐Resistant Hypoxia Tumors

Nuthalapati

Vankayala

Chiang

et al. 2020

Part & Part Syst Charact

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Development of simple, robust, and noninvasive therapeutic approaches to treat cancers and improve survival rates is a grand challenge in clinical biomedicine. In particular, the sizes and shape of the nanomaterials play a vital role in dictating their biodistribution and clearance pathways. It remains elusive how the size and shape of a nanomaterial affect its therapeutic efficacy in cancer diagnosis and treatments. To tackle the above problem, the effects of size and shape of Cu2(OH)PO4 nanostructures (nanosheets and quantum dots) on the photodynamic therapy (PDT) in destroying malignant drug‐resistant lung tumors and on combating the tumor hypoxia problem are investigated and compared. The photocatalytic mechanism of Cu2(OH)PO4 nanostructures mainly involves the generation of reactive oxygen species (ROS), such as hydroxyl radical (·OH) and singlet oxygen (1O2). Under an oxygen deprivation condition, Cu2(OH)PO4 nanosheets still can generate OH radicals to kill cancer cells upon near‐infrared (NIR) light irradiation. Overall, in vitro and in vivo experiments show that Cu2(OH)PO4 nanosheets can overcome tumor hypoxia problems and effectively mediate dual modal PDT and photothermal therapeutic (PTT) effects on destruction of NCI‐H23 lung tumors in mice using ultralow doses (350 mW cm−2) of NIR (915 nm) light.

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The Syringe Nitroxide Free Radical – Part II

Cited by 10 publications

References 9 publications

Light-induced generation of radicals on semiconductor-free carbon photocatalysts

Light-induced generation of radicals on semiconductor-free carbon photocatalysts

The Mechanism-based Inactivation of 2,3-Dihydroxybiphenyl 1,2-Dioxygenase by Catecholic Substrates

Size and Shape Effects of Near‐Infrared Light‐Activatable Cu₂(OH)PO₄ Nanostructures on Phototherapeutic Destruction of Drug‐Resistant Hypoxia Tumors

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The Syringe Nitroxide Free Radical – Part II

Cited by 10 publications

References 9 publications

Light-induced generation of radicals on semiconductor-free carbon photocatalysts

Light-induced generation of radicals on semiconductor-free carbon photocatalysts

The Mechanism-based Inactivation of 2,3-Dihydroxybiphenyl 1,2-Dioxygenase by Catecholic Substrates

Size and Shape Effects of Near‐Infrared Light‐Activatable Cu2(OH)PO4 Nanostructures on Phototherapeutic Destruction of Drug‐Resistant Hypoxia Tumors

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Product

Resources

About

Size and Shape Effects of Near‐Infrared Light‐Activatable Cu₂(OH)PO₄ Nanostructures on Phototherapeutic Destruction of Drug‐Resistant Hypoxia Tumors