UV-Induced Charge-Transfer States in Short Guanosine-Containing DNA Oligonucleotides.

Corinna L Kufner,Dominik B Bucher,Wolfgang Zinth

doi:10.1002/cbic.202000103

Abstract

Charge transfer has proven to be an important mechanism in DNA photochemistry. In particular, guanine (dG) plays a major role as an electron donor, but the photophysical dynamics of dG‐containing charge‐transfer states have not been extensively investigated so far. Here, we use UV pump (266 nm) and picosecond IR probe (∼5–7 μm) spectroscopy to study ultrafast dynamics in dG‐containing short oligonucleotides as a function of sequence and length. For the pure purine oligomers, we observed lifetimes for the charge‐transfer states of the order of several hundreds of picoseconds, regardless of the oligonucleotide length. In contrast, pyrimidine‐containing dinucleotides d(GT) and d(GC) show much faster relaxation dynamics in the 10 to 30 ps range. In all studied nucleotides, the charge‐transfer states are formed with an efficiency of the order of ∼50 %. These photophysical characteristics will lead to an improved understanding of DNA damage and repair processes.

Highlights

Introduction irradiationThis repair is explained by a charge transfer from the transiently formed charge-transfer state d(G + A ).[5a]In this study, we investigated the photophysical properties of dG-containing short oligonucleotides
We investigated the photophysical properties of dG-containing short oligonucleotides
In a first set of experiments, we investigated the dinucleotides d (GA), d(GT) and d(GC) by using transient UV-pump and mid-IR

Summary

Very Important Paper

UV-Induced Charge-Transfer States in Short GuanosineContaining DNA Oligonucleotides. Charge transfer has proven to be an important mechanism in DNA photochemistry. UV irradiation induces a selection pressure to which DNA molecules have been exposed for several billions of years on the surface of the earth.[1] It is assumed that the selection of the four canonical DNA mononucleotides is related to photostability provided by the ultrashort lifetimes of the excited states.[2] As information carrier, DNA contains the individual canonical nucleotides in strands of defined sequences. This geometric arrangement drastically alters the photophysics. It has been shown that the cyclobutane thymine-dimer lesion (T=T) in the sequence d(GAT=T) is strongly repaired under UV

Results and Discussion

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Conclusions

Conflict of Interest

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