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De novo generation of singlet oxygen and ammine ligands by photoactivation of a platinum anticancer complex.

Zhao Y, Farrer NJ, Li H, Butler JS, McQuitty RJ, Habtemariam A, Wang F, Sadler PJ - Angew. Chem. Int. Ed. Engl. (2013)

Bottom Line: Worth the excitement: Highly reactive oxygen and nitrogen species are generated by photoactivation of the anticancer platinum(IV) complex trans,trans,trans-[Pt(N3 )2 (OH)2 (MA)(Py)] (MA=methylamine, Py=pyridine).Singlet oxygen is formed from the hydroxido ligands and not from dissolved oxygen, and ammine ligands are products from the conversion of azido ligands to nitrenes.Both processes can induce oxidation of guanine.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Warwick, Coventry CV4 7AL (United Kingdom); Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (P.R. China).

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Time-dependent fluorescence (λex/λem=504/525 nm) from 1 (50 μm) and SOSG (1 μm) in H2O (3 % MeOH) upon weak irradiation at 365 nm (21 μW cm−2) (293 K). ▪: no additive; □: 50 % D2O; ▴: saturated with argon; •: 0.1 mm l-ascorbic acid (AscA). All the data points were the average of 2–4 independent experiments.
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fig02: Time-dependent fluorescence (λex/λem=504/525 nm) from 1 (50 μm) and SOSG (1 μm) in H2O (3 % MeOH) upon weak irradiation at 365 nm (21 μW cm−2) (293 K). ▪: no additive; □: 50 % D2O; ▴: saturated with argon; •: 0.1 mm l-ascorbic acid (AscA). All the data points were the average of 2–4 independent experiments.

Mentions: The nature of the released oxygen was investigated using a fluorescence probe for singlet oxygen: SOSG. SOSG is a highly selective sensor for 1O2 without any appreciable response to hydroxyl radicals or superoxide.9 In the absence of 1O2, SOSG exhibits low fluorescence, but in the presence of 1O2, strong green fluorescence can be observed with λex=504 nm and λem=525 nm. Solutions containing 1 and SOSG were stable in the dark or even upon irradiation at λ≥504 nm. However, when exposed to weak irradiation at 365 nm (21 μW cm−2), the intensity of the fluorescence at 525 nm increased rapidly, thus indicating that 1O2 was generated (Figure 2). The dose-dependent efficiency of generating 1O2 upon irradiation was higher the shorter the wavelength (UVA>420 nm>450 nm, see Figure S10 in the Supporting Information). Control experiments carried out in the dark or in the absence of 1 showed no change in the fluorescence intensity (see Figure S10 in the Supporting Information). A sample saturated with argon was irradiated at 365 nm and gave stronger fluorescence (Figure 2). This result revealed that the 1O2 was not generated from the dissolved O2 through energy transfer from a photosensitizer. N2 had a similar effect as argon. Neither argon nor N2 itself could trigger the fluorescence of SOSG. The release of singlet oxygen from a PtIV-diazidodihydroxido complex upon irradiation with light in the absence of any exogenous source of oxygen gas appears to be unprecedented.


De novo generation of singlet oxygen and ammine ligands by photoactivation of a platinum anticancer complex.

Zhao Y, Farrer NJ, Li H, Butler JS, McQuitty RJ, Habtemariam A, Wang F, Sadler PJ - Angew. Chem. Int. Ed. Engl. (2013)

Time-dependent fluorescence (λex/λem=504/525 nm) from 1 (50 μm) and SOSG (1 μm) in H2O (3 % MeOH) upon weak irradiation at 365 nm (21 μW cm−2) (293 K). ▪: no additive; □: 50 % D2O; ▴: saturated with argon; •: 0.1 mm l-ascorbic acid (AscA). All the data points were the average of 2–4 independent experiments.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4230391&req=5

fig02: Time-dependent fluorescence (λex/λem=504/525 nm) from 1 (50 μm) and SOSG (1 μm) in H2O (3 % MeOH) upon weak irradiation at 365 nm (21 μW cm−2) (293 K). ▪: no additive; □: 50 % D2O; ▴: saturated with argon; •: 0.1 mm l-ascorbic acid (AscA). All the data points were the average of 2–4 independent experiments.
Mentions: The nature of the released oxygen was investigated using a fluorescence probe for singlet oxygen: SOSG. SOSG is a highly selective sensor for 1O2 without any appreciable response to hydroxyl radicals or superoxide.9 In the absence of 1O2, SOSG exhibits low fluorescence, but in the presence of 1O2, strong green fluorescence can be observed with λex=504 nm and λem=525 nm. Solutions containing 1 and SOSG were stable in the dark or even upon irradiation at λ≥504 nm. However, when exposed to weak irradiation at 365 nm (21 μW cm−2), the intensity of the fluorescence at 525 nm increased rapidly, thus indicating that 1O2 was generated (Figure 2). The dose-dependent efficiency of generating 1O2 upon irradiation was higher the shorter the wavelength (UVA>420 nm>450 nm, see Figure S10 in the Supporting Information). Control experiments carried out in the dark or in the absence of 1 showed no change in the fluorescence intensity (see Figure S10 in the Supporting Information). A sample saturated with argon was irradiated at 365 nm and gave stronger fluorescence (Figure 2). This result revealed that the 1O2 was not generated from the dissolved O2 through energy transfer from a photosensitizer. N2 had a similar effect as argon. Neither argon nor N2 itself could trigger the fluorescence of SOSG. The release of singlet oxygen from a PtIV-diazidodihydroxido complex upon irradiation with light in the absence of any exogenous source of oxygen gas appears to be unprecedented.

Bottom Line: Worth the excitement: Highly reactive oxygen and nitrogen species are generated by photoactivation of the anticancer platinum(IV) complex trans,trans,trans-[Pt(N3 )2 (OH)2 (MA)(Py)] (MA=methylamine, Py=pyridine).Singlet oxygen is formed from the hydroxido ligands and not from dissolved oxygen, and ammine ligands are products from the conversion of azido ligands to nitrenes.Both processes can induce oxidation of guanine.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Warwick, Coventry CV4 7AL (United Kingdom); Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (P.R. China).

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