| 1. |
- Preus, S., et al.
(författare)
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The photoinduced transformation of fluorescent DNA base analogue tC triggers DNA melting
- 2013
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Ingår i: Photochemical and Photobiological Sciences. - : Springer Science and Business Media LLC. - 1474-9092 .- 1474-905X. ; 12:8, s. 1416-1422
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Tidskriftsartikel (refereegranskat)abstract
- While fluorescent analogues of the canonical nucleobases have proven to be highly valuable in a large number of applications, up until today, fluorescent DNA base analogues remain virtually inapplicable for single-molecule fluorescence experiments which require extremely bright and photostable dyes. Insight into the photodegradation processes of these fluorophores is thus a key step in the continuous development towards dyes with improved performances. Here, we show that the commercially available fluorescent nucleobase analogue tC under intense long-term illumination and in the presence of O-2 is degraded to form a single photoreaction product which we suggest to be the sulfoxide form of tC. The photoproduct is characterized by a blue-shifted absorption and a less intense fluorescence compared to that of tC. Interestingly, when tC is positioned inside double-stranded DNA this photodriven conversion of tC to its photoproduct greatly reduces the duplex stability of the overall double helix in which the probe is positioned. Since tC can be excited selectively at 400 nm, well outside the absorption band of the natural DNA bases, this observation points towards the application of tC as a general light-triggered switch of DNA duplex stability.
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| 2. |
- Karpkird, T. M., et al.
(författare)
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Photophysical characterization of cinnamates
- 2009
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Ingår i: Photochemical and Photobiological Sciences. - : Springer Science and Business Media LLC. - 1474-9092 .- 1474-905X. ; 8:10, s. 1455-1460
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Tidskriftsartikel (refereegranskat)abstract
- The photophysical properties of five methoxy-substituted 2-ethylhexylcinnamates were studied with experimental and theoretical methods. It was found that the fluorescence quantum yields varied strongly with the substitution pattern of the phenyl ring. A methoxy substitution at the meta position gave strong fluorescence, whereas the para substituted compounds were strongly quenched. This observation could be correlated to corresponding changes in the UV absorption spectra; the two lowest pi pi* states were split for the meta-methoxy substituted cinnamate but almost degenerate for the para compound. Semi-empirical quantum mechanical calculations confirmed both the observed state order and the difference in the experimentally determined activation energies for non-radiative decay. This "meta-effect" was also preserved in the trimethoxy-substituted compounds, 2-ethylhexyl-2,4,5- and 2,4,6-trimethoxycinnamate, resulting in strong fluorescence and relatively high barrier for non-radiative decay in the former and weak fluorescence and relatively low barrier for non-radiative decay in the latter. The obtained information shows how the performance of the commercial sunscreen agent, 2-ethylhexyl-para-methoxycinnamate (OMC) might be improved.
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