Current Group Research
Excited-State Dynamics of UVA Sensitizers and DNA Analogues
The focus of our research group is on identifying and studying DNA and RNA monomer analogues that exhibit high triplet yields. Excited triplet states are important precursor of light-induced DNA damage. However, progress at understanding the kinetic mechanisms by which triplet state is populated has been hindered by the intrinsically small triplet quantum yields of DNA and RNA monomers in aqueous solutions. Efforts at understanding the mechanisms by which triplet states are populated in DNA/RNA analogues can provide important information about the electronic and nuclear relaxation pathways that control the population of the triplet state in DNA monomers.
We are currently interested in a family of biomolecules known as prodrugs, which are widely use in therapeutic and pharmacological applications. Their metabolic incorporation into the DNA of patients treated with these prodrugs often results in increased toxicity and skin cancer after the patients are exposed to prolonged periods of sunlight. Understanding the excited-state dynamics in these DNA/RNA analogues can help to understand the light-induced chemistry in DNA/RNA monomers and it is also an important step toward the design of the next generation of prodrugs showing reduced phototoxic side effects.
Example of the Ultrafast Spectroscopy of 6-Thioguanosine
Figure legend: Absorption spectra of 6-thioguanosine in aqueous buffer solution and acetonitrile (top panel) and Femtosecond-to-microsecond broadband transient absorption spectra of 6-thioguanosine (6tGuo) in aqueous buffer solution after photoexcitation at 350 nm (bottom panel). See Reichardt et al. J. Phys. Chem. B 2011, 115, 3263 for details.
Literature Recipes For Calculating Extinction Coefficients and Other Physical Properties of Short Oligonucleotides and DNA
- Reichardt, C.; Wen, C.; Vogt, R. A.; Crespo-Hernández, C. E.; "Role of Intersystem Crossing in the Fluorescence Quenching of 2-Aminopurine 2'-deoxyriboside in Solution" (Invited Manuscript; submitted as part of the themed issue on the "Interaction of UV Radiation with DNA"), Photochem. Photobiol. Sci. 2013, DOI:10.1039/C3PP25437B.Access article
- Reichardt, C.; Guo, C.; Crespo-Hernández, C. E.;"Excited-State Dynamics in 6-Thioguanosine from the Femtosecond to Microsecond Time Scale", J. Phys. Chem. B 2011, 115, 3263-3270.Access article
- Reichardt, C.; Crespo-Hernández, C. E.; "Room-Temperature Phosphorescence of the DNA Monomer Analogue 4-Thiothymidine in Aqueous Solutions after UVA Excitation", J. Phys. Chem. Lett. 2010, 1, 2239-2243.Access article
- Reichardt, C.; Crespo-Hernández, C. E.; "Ultrafast Spin Crossover in 4-Thiothymidine in an Ionic Liquid", Chem. Comm. 2010, 46, 5963-5965.Access article