Observation of Enhanced Dissociative Photochemistry in the Non-Native Nucleobase 2-Thiouracil
| Autor: | Rosaria Cercola, Kelechi O. Uleanya, Natalie G. K. Wong, Edward Matthews, Maria Nikolova, Caroline E. H. Dessent |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Free Radicals
Photochemistry Pharmaceutical Science Electrons Protonation 02 engineering and technology 010402 general chemistry 01 natural sciences Thiouracil Article Analytical Chemistry Ion lcsh:QD241-441 lcsh:Organic chemistry Drug Discovery 2-thiouracil free-radicals Physical and Theoretical Chemistry excited states Ions Chemistry Spectrum Analysis Organic Chemistry Photodissociation non-native nucleobase 021001 nanoscience & nanotechnology Internal conversion (chemistry) 0104 chemical sciences Photoexcitation Intersystem crossing Chemistry (miscellaneous) Excited state Molecular Medicine 0210 nano-technology Ground state phototherapy |
| Zdroj: | Molecules Volume 25 Issue 14 Molecules, Vol 25, Iss 3157, p 3157 (2020) |
| ISSN: | 1420-3049 |
| DOI: | 10.3390/molecules25143157 |
| Popis: | We present the first study to measure the dissociative photochemistry of 2-thiouracil (2-TU), an important nucleobase analogue with applications in molecular biology and pharmacology. Laser photodissociation spectroscopy is applied to the deprotonated and protonated forms of 2-TU, which are produced in the gas-phase using electrospray ionization mass spectrometry. Our results show that the deprotonated form of 2-thiouracil ([2-TU-H]&minus ) decays predominantly by electron ejection and hence concomitant production of the [2-TU-H]· free-radical species, following photoexcitation across the UVA-UVC region. Thiocyanate (SCN&minus ) and a m/z 93 fragment ion are also observed as photodecay products of [2-TU-H]&minus but at very low intensities. Photoexcitation of protonated 2-thiouracil ([2-TU· H]+) across the same UVA-UVC spectral region produces the m/z 96 cationic fragment as the major photofragment. This ion corresponds to ejection of an HS· radical from the precursor ion and is determined to be a product of direct excited state decay. Fragment ions associated with decay of the hot ground state (i.e., the ions we would expect to observe if 2-thiouracil was behaving like UV-dissipating uracil) are observed as much more minor products. This behaviour is consistent with enhanced intersystem crossing to triplet excited states compared to internal conversion back to the ground state. These are the first experiments to probe the effect of protonation/deprotonation on thionucleobase photochemistry, and hence explore the effect of pH at a molecular level on their photophysical properties. |
| Databáze: | OpenAIRE |
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