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- Dong, Jingran, et al.
(author)
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Kinetics and mechanism of oxidation of the anti-tubercular prodrug isoniazid and its analog by iridium(IV) as models for biological redox systems
- 2017
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In: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; 46:26, s. 8377-8386
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Journal article (peer-reviewed)abstract
- A complex reaction mechanism of oxidation of the anti-tubercular prodrug isoniazid (isonicotinic hydrazide, INH) by [IrCl6]2− as a model for redox processes of such drugs in biological systems has been studied in aqueous solution as a function of pH between 0 and 8.5. Similar experiments have been performed with its isomer nicotinic hydrazide (NH). All reactions are overall second-order, first-order in [IrCl6]2− and hydrazide, and the observed second-order rate constants k′ have been determined as a function of pH. Spectrophotometric titrations indicate a stoichiometry of [Ir(IV)]:[hydrazide] = 4:1. HPLC analysis shows that the oxidation product of INH is isonicotinic acid. The derived reaction mechanism, based on rate law, time-resolved spectra and stoichiometry, involves parallel attacks by [IrCl6]2− on all four protolytic species of INH and NH as rate-determining steps, depending on pH. These steps are proposed to generate two types of hydrazyl free radicals. These radicals react further in three rapid consecutive processes, leading to the final oxidation products. Rate constants for the rate-determining steps have been determined for all protolytic species I–IV of INH and NH. They are used to calculate reactivity–pH diagrams. These diagrams demonstrate that for both systems, species IV is ca. 105 times more reactive in the redox process than the predominant species III at the physiological pH of 7.4. Thus, species IV will be the main reactant, in spite of the fact that its concentration at this pH is extremely low, a fact that has not been considered in previous work. The results indicate that pH changes might be an important factor in the activation process of INH in biological systems also, and that in such systems this process most likely is more complicated than previously assumed
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| 2. |
- Xu, Li, 1986, et al.
(author)
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Graphene-based biosensors for the detection of prostate cancer protein biomarkers: a review
- 2019
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In: BMC Chemistry. - : Springer Science and Business Media LLC. - 2661-801X. ; 13:1
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Journal article (other academic/artistic)abstract
- Prostate cancer (PC) is the sixth most common cancer type in the world, which causes approximately 10% of total cancer fatalities. The detection of protein biomarkers in body fluids is the key topic for the diagnosis and prognosis of PC. Highly sensitive screening of PC is the most effective approach for reducing mortality. Thus, there are a growing number of literature that recognizes the importance of new technologies for early diagnosis of PC. Graphene is playing an important role in the biosensor field with remarkable physical, optical, electrochemical and magnetic properties. Many recent studies demonstrated the potential of graphene materials for sensitive detection of protein biomarkers. In this review, the graphene-based biosensors toward PC analysis are mainly discussed in two groups: Firstly, novel biosensor interfaces were constructed through the modification of graphene materials onto sensor surfaces. Secondly, ingenious signal amplification strategies were developed using graphene materials as catalysts or carriers. Graphene-based biosensors have exhibited remarkable performance with high sensitivities, wide detection ranges, and long-term stabilities.
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